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Traveling faster than light is an inevitable longing for the human species, which aspires to expand through the cosmos. But in reality, if we think about it, light moves very slowly compared to the immense scales of the universe: Earthlings would have to wait more than four years for a ship travelling at the speed of light to reach the closest stars, and 25,000 years to get to the nearest galaxy, Canis Major Dwarf. It would seem that we are condemned to never meet other beings with whom we might establish a civilized relationship.

Fortunately, modern theoretical physics offers us a solution: manipulate space-time to move ourselves to other remote places in the cosmos without formally violating the universal speed limit. The simplest explanation to take home of why you can’t travel faster than light is this: if it were done, an effect could appear before its cause, since the velocity of light is the invariant cosmic ruler that measures physical phenomena—we could receive a phone call before the caller thinks about making it.

However, since Einstein’s general relativity defined space-time as the fabric from which the universe is made , the theory does allow this cosmic tapestry to wrinkle; an example is the gravitational waves detected in recent years by the LIGO and Virgo experiments. If we could create wrinkles in space-time , we might be able to manage to bring a distant location much closer to us, so it would be possible to reach it without breaking the light speed barrier.

Alcubierre’s model

A device capable of achieving this is known as a warp drive and was proposed in 1994 by the Mexican theoretical physicist Miguel Alcubierre, inspired by the concept and the name given in the television series Star Trek , as confirmed by the physicist to OpenMind in a prior interview. The idea is to “ create a bubble of distorted space inside which would be the spacecraft,” said Alcubierre, so that “the space behind the object that we want to move would violently expand, and at the same time the space in front of the object would contract.” Thus, “ the object moves without actually moving ; it is space itself that does the work.”

Alcubierre’s model, considered one of the most formally correct to propose an interstellar voyage on paper, has motivated countless studies and not a little speculation. Recently, a report has been published that the US Department of Defense assigned to two physicists in 2010, entitled Warp Drive, Dark Energy and the Manipulation of Extra Dimensions . The authors present “two loopholes to Einstein’s ultimate speed limit”: the warp drive and wormholes —technically called Einstein-Rosen bridges—a kind of shortcut in the fabric of space-time that would connect very distant regions of the universe, and whose existence is theoretically possible.

The report focuses on Alcubierre’s model, and above all on exploring how the necessary curvature bubble could be created. As the astrophysicist Geraint Lewis from the University of Sydney (Australia), who did not participate in the report, explained to OpenMind : “We know that normal matter can curve space-time, but matter cannot bend space the right way to make a warp drive.” Lewis clarifies that this requires: “very non-normal matter that contains a tension, rather than a pressure that you would have with a gas.” In other words, we need a type of matter capable of generating negative pressure , or negative energy. And this description fits precisely with something that Lewis is an expert in: dark energy. “There is the potential for dark energy to give us a warp drive,” he suggests.

A 193-second journey to Mars

According to current cosmological models, dark energy is what makes up more than 70% of the entire universe . It’s a hypothetical type of antigravity that is responsible for the accelerated expansion of the universe. The authors of the report propose using this dark energy to open a bubble in an additional dimension, which could fit a ship of about 100 cubic metres, somewhat larger than a standard truck. “Trips to the planets within our own solar system would take hours rather than years, and journeys to local star system would be measured in weeks rather than hundreds of thousands of years,” they write. As examples, the authors calculate that at a speed 100 times greater than that of light, Mars would only be a 193-second journey ; Jupiter could be reached 36 minutes, Alpha Centauri in 15 days and the Orion nebula in 1.3 years.

All this sounds enormously tempting, but is there any chance that these proposals could go from paper to reality? Is it just a matter of advanced engineering, or are we facing some insurmountable physical barrier? There is a widespread belief among physicists that these ideas will never materialize . Alcubierre himself points out some colossal obstacles, such as the so-called “horizon problem”: “when traveling faster than light, the front of the bubble is not accessible from the inside, so the ship that is in the centre cannot place the energy at that spot.” “Systems like the one I proposed are almost impossible, but it’s difficult to know,” he concludes.

Naturally, the main obstacle is the energy requirement: the proposal of the authors of the report significantly reduces the amount of energy needed, but even so, travelling at 100 times the speed of light would require an energy input of the order of one tenth of the total power of the Sun . “The energies are still far in excess of those available in the foreseeable future,” the authors admit.

More critical is another essential aspect: this immense quantity of energy will have to be provided not in the form of the energy we handle on a daily basis, but as something called negative energy, which does not yet even exist. “At the moment, we have no idea if we can obtain such a material in any physically workable way, so that a warp drive might be theoretically possible, but practically impossible,” warns Lewis.

All of which has not prevented us from already trying. At NASA’s Johnson Centre there is an Advanced Propulsion Physics Laboratory—informally called Eagleworks Laboratory—which the agency itself does not tend to promote too much, but which has been trying to create microscopic curvature bubbles for years as a proof of concept. At the moment it is still science fiction, but Lewis is optimistic: “As we push the theories of gravity and quantum mechanics together, hopefully we will find clues to make this a reality, which is what I hope will happen.”

Javier Yanes

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Warp drives: Physicists investigate faster-than-light space travel

The closest star to Earth is Proxima Centauri. It is about 4.25 light-years away, or about 25 trillion miles (40 trillion kilometers). The fastest ever spacecraft, the now- in-space Parker Solar Probe will reach a top speed of 450,000 mph. It would take just 20 seconds to go from Los Angeles to New York City at that speed, but it would take the solar probe about 6,633 years to reach Earth’s nearest neighboring solar system.

If humanity ever wants to travel easily between stars, people will need to go faster than light. But so far, faster-than-light travel is possible only in science fiction.

In Issac Asimov’s Foundation series , humanity can travel from planet to planet, star to star or across the universe using jump drives. As a kid, I read as many of those stories as I could get my hands on. I am now a theoretical physicist and study nanotechnology, but I am still fascinated by the ways humanity could one day travel in space.

Some characters – like the astronauts in the movies “Interstellar” and “Thor” – use wormholes to travel between solar systems in seconds. Another approach – familiar to “Star Trek” fans – is warp drive technology. Warp drives are theoretically possible if still far-fetched technology. Two recent papers made headlines in March when researchers claimed to have overcome one of the many challenges that stand between the theory of warp drives and reality.

But how do these theoretical warp drives really work? And will humans be making the jump to warp speed anytime soon?

Compression and expansion

Physicists’ current understanding of spacetime comes from Albert Einstein’s theory of general relativity . General relativity states that space and time are fused and that nothing can travel faster than the speed of light. General relativity also describes how mass and energy warp spacetime – hefty objects like stars and black holes curve spacetime around them. This curvature is what you feel as gravity and why many spacefaring heroes worry about “getting stuck in” or “falling into” a gravity well. Early science fiction writers John Campbell and Asimov saw this warping as a way to skirt the speed limit.

What if a starship could compress space in front of it while expanding spacetime behind it? “Star Trek” took this idea and named it the warp drive.

In 1994, Miguel Alcubierre, a Mexican theoretical physicist, showed that compressing spacetime in front of the spaceship while expanding it behind was mathematically possible within the laws of General Relativity . So, what does that mean? Imagine the distance between two points is 33 feet (10 meters). If you are standing at point A and can travel one meter per second, it would take 10 seconds to get to point B. However, let’s say you could somehow compress the space between you and point B so that the interval is now just one meter. Then, moving through spacetime at your maximum speed of one meter per second, you would be able to reach point B in about one second. In theory, this approach does not contradict the laws of relativity since you are not moving faster than light in the space around you. Alcubierre showed that the warp drive from “Star Trek” was in fact theoretically possible.

Proxima Centauri here we come, right? Unfortunately, Alcubierre’s method of compressing spacetime had one problem: it requires negative energy or negative mass.

A negative energy problem

Alcubierre’s warp drive would work by creating a bubble of flat spacetime around the spaceship and curving spacetime around that bubble to reduce distances. The warp drive would require either negative mass – a theorized type of matter – or a ring of negative energy density to work. Physicists have never observed negative mass, so that leaves negative energy as the only option.

To create negative energy, a warp drive would use a huge amount of mass to create an imbalance between particles and antiparticles. For example, if an electron and an antielectron appear near the warp drive, one of the particles would get trapped by the mass and this results in an imbalance. This imbalance results in negative energy density. Alcubierre’s warp drive would use this negative energy to create the spacetime bubble.

But for a warp drive to generate enough negative energy, you would need a lot of matter. Alcubierre estimated that a warp drive with a 100-meter bubble would require the mass of the entire visible universe .

In 1999, physicist Chris Van Den Broeck showed that expanding the volume inside the bubble but keeping the surface area constant would reduce the energy requirements significantly , to just about the mass of the Sun. A significant improvement, but still far beyond all practical possibilities.

A sci-fi future?

Two recent papers – one by Alexey Bobrick and Gianni Martire and another by Erik Lentz – provide solutions that seem to bring warp drives closer to reality.

Bobrick and Martire realized that by modifying spacetime within the bubble in a certain way, they could remove the need to use negative energy. This solution, though, does not produce a warp drive that can go faster than light.

Independently, Lentz also proposed a solution that does not require negative energy. He used a different geometric approach to solve the equations of general relativity, and by doing so, he found that a warp drive wouldn’t need to use negative energy. Lentz’s solution would allow the bubble to travel faster than the speed of light.

It is essential to point out that these exciting developments are mathematical models. As a physicist, I won’t fully trust models until we have experimental proof. Yet, the science of warp drives is coming into view. As a science fiction fan, I welcome all this innovative thinking. In the words of Captain Picard , things are only impossible until they are not.

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5 Faster-Than-Light Travel Methods and Their Plausibility

Science tells us that it is impossible for an object to travel at light speed, let alone faster than that. But so many of our favorite science-fiction movies, games, and TV shows rely on faster-than-light travel to craft their interplanetary adventures.

Let’s take a look at five means of FTL found in sci-fi that don’t break the rules of relativity and examine how plausible they are based on the science behind them.

1. Hyperdrive

Popularized by Star Wars and used extensively in fiction, a hyperdrive enables a spaceship to travel at FTL speeds by entering another dimension known as “hyperspace.” The spaceship isn’t actually traveling faster than the speed of light, but rather is making use of hyperspace as a shortcut, and the hyperdrive is the mechanism that shunts the spaceship into and out of this parallel dimension.

Specific coordinates within hyperspace have corresponding coordinates in normal space, but the distance between those two points will be shorter in hyperspace, allowing for a faster journey. Before making a “hyperspace jump,” calculations must be made to find the matching coordinates between hyperspace and normal space in order to know when and where to exit hyperspace at the desired normal space destination.

Is it plausible?

Physicist Bukrhard Heim proposed a theory in 1977 that FTL travel may be possible by using magnetic fields to enter higher-dimensional space. The theory uses a mathematical model that calls upon six or more dimensions in an attempt to resolve incompatibilities between quantum mechanics and general relativity, but Heim’s ideas have not been accepted in mainstream science. Still, the fact that a theoretical physicist devoted a large portion of his life in pursuit of a theory that could lead to a means of space travel lends the concept of hyperspace a little more credibility than if it were simply the fancy of a sci-fi writer.

2. Jump Drive

Seen in such works as Battlestar Galactica , a jump drive allows for instantaneous teleportation between two points. Similar to a hyperdrive, coordinates must be calculated to ensure a safe jump; the longer the desired travel distance, the more complex the calculation. In theory, there is no limit to how far a jump can take a ship, but an incorrect calculation may result in a catastrophic collision with a planet or space debris.

The Dune universe’s FTL, based on the fictional “Holtzman effect,” can also be considered a jump drive.

Master of hard sci-fi Isaac Asimov was the first to suggest the idea of a jump drive in the Foundation series, which lends some credibility to the idea. However, most fiction doesn’t clearly explain the principles of physics that allow for this teleportation, making it impossible to claim a jump drive as plausible. However, if it functions by opening a wormhole…

3. Wormholes

A wormhole, as seen in the Stargate franchise, allows for near-instantaneous travel across vast distances. Wormholes may be naturally-occurring or man-made, but are almost always temporary and serve as tunnels through spacetime.

Imagine our universe as a piece of paper, and an ant walking on that piece of paper as a spaceship. If the ant wants to walk from one end of that piece of paper to the other, the fastest way to do so would be to travel in a straight line. But paper, like space, bends. If you bend the paper into a U shape, the ant’s journey goes largely undisturbed – it still has to traverse the same distance along that line. However, in 3D space, the two ends of the paper are very close to each other now. Cut off a piece of a drinking straw and let the ant use it as a bridge or tunnel between the two ends of the paper, and the journey is suddenly much shorter.

While we have never directly observed any evidence for one, wormholes are theoretically possible. Albert Einstein and his colleague Nathan Rosen first discovered wormholes in 1935 as solutions to equations within Einstein’s general theory of relativity – the math says they can exist.

Since then, other scientists, including Stephen Hawking, have argued that it may be possible to traverse a wormhole, under the right circumstances. The debate surrounding wormholes isn’t about their plausibility, but rather how they may be created and sustained.

4. Slipstream

The concept of slipstream can be found in such works as Star Trek , Doctor Who , and the Halo video game franchise, but there is no widely-agreed upon definition of what slipstream is or how it works beyond it being a means of FTL. We’ll consider the slipstream seen in Gene Roddenberry’s Andromeda , where it is “not the best way to travel faster than light, it’s just the only way,” as per the show’s protagonist.

Slipstream is a form of interdimensional highway in which ships ride a series of slipstream “strings” – the unseen connections between all objects in the universe. These strings are in constant flux and form a tangled mess of intersections and divergent paths. Any time a pilot reaches a fork in the road, he has to guess which is the correct path to take to continue along toward his desired destination. Before the pilot makes that decision, both paths are simultaneously the correct and incorrect route, and it is the act of choosing a path that forces one to be correct and the other to be incorrect – if this made you think of Shrödinger’s cat, that does seem to be the basis for this concept. A computer selects the “correct” path 50% of the time, but due to intuition, a human picks the correct path 99.9% of the time.

There are no mainstream scientific theories that support this idea of slipstream. Reading the “lore” of this means of FTL evokes fantastical interpretations of string theory, quantum entanglement, and other concepts in modern physics, but the ideas are supported only through their internal consistency rather than actual fact, much like a well-explained magic system that allows fictional wizards to cast spells.

5. Warp Drive

Popularized by Star Trek , a warp drive distorts space around a ship while leaving the ship itself inside a “bubble” of normal space. The space in front of the ship is contracted, while the space behind it is expanded, and the ship “rides” the distortion wave at FTL speeds. Technically, it is not the ship that is moving, but rather space itself, which is how we avoid breaking any laws of physics.

Imagine a surfer slowly paddling back to shore. When a wave comes, it will lower the water level in front of him and raise the water level behind him, and he can ride the downward slope all the way to shore. Relative to the wave, the surfer isn’t moving – he’s staying between the crest and the trough, and it is instead the wave that is moving.

Surfing doesn’t quite work like that, but it’s a simplification that we can all visualize. In a similar manner to how a wave will distort water to propel a surfer, a warp drive will distort space to propel a ship.

In 1994, the Alcubierre drive was proposed as a theoretical means of FTL travel and is based on a mathematical solution to equations within Einstein’s general theory of relativity. Just like a warp drive, the Alcubierre drive would contract space in front of a spaceship and expand space behind it.

NASA has been actively researching this technology since 2012 , and the lead researcher even worked with a 3D artist to develop a model of what a warp-capable ship might look like . As far as real-life FTL goes, warp is the current front-runner to becoming reality.

As far as real-life FTL travel goes, the fictional favorites can be found in Star Trek and Stargate : the warp drive, and wormholes. Both are theoretically possible; however, both require further scientific breakthroughs before practical testing can begin. In either case, we need to discover “exotic matter” – hypothetical particles with negative mass – to get these mechanisms to work. “Element zero” from the Mass Effect series, the rare material that is essential to FTL travel in that universe, doesn’t quite fit the description, but the lore is at least scientifically sound in suggesting that some new, rare form of matter is required to make this technological leap.

The good news is that scientists don’t believe this is a matter of if, but rather when. There will be a time in the future when a stately, bald man in uniform will sit back in a command chair and relay the order, “Engage.”

The Case for Curving Around Space-Time: Possibilities and Pitfalls

Buckle up for a wild ride through the universe with the power of space-time curvature! Harnessing the power of the universe, we explore the possibilities of bending time and space for interstellar travel. However, such a task comes with practical challenges and ethical considerations. This article delves into the science and technology of manipulating space-time, as well as the consequences of doing so. Discover the frontiers of space-time curvature and the future it holds for humanity.

I. Introduction

Gather around, space pioneers, as we embark on a journey through the universe, exploring the power of space-time curvature. As our knowledge expands, so too does our understanding of the nature of the universe as we investigate the incredible phenomena that govern the fabric of space-time itself. By bending space-time, we push the limits of human exploration, defying the boundaries of interstellar travel.

The consequences of such an endeavor, however, are not for the faint of heart. For many to travel and explore the galaxy, the technology and science behind space-time curvature must advance dramatically. It requires reshaping space-time itself, altering the curvature of the universe to transport us to the farthest reaches of space.

As we push the boundaries of technology, we must also confront the ethical dilemmas of space-time curvature. There are serious questions that must be answered about the impact of manipulating the fabric of space and time, and the consequences not just for ourselves, but for the universe as a whole.

But as we explore the frontiers of space-time curvature, we cannot help but feel the excitement and possibility of what awaits us. In this article, we delve into the science and technology of manipulating space-time, considering the practical challenges and ethical considerations that come with it. Join us for an adventure through the universe as we explore the possibilities of bending time and space using space-time curvature. The question of the power of space-time curvature is not one to be taken lightly, but rather one that demands to be explored and understood as we move towards a future among the stars.

II. Harnessing Space-Time Curvature for Interstellar Travel

As we look towards the stars, we realize that the biggest obstacle to interstellar travel is the vast distance we have to cover. But what if we could bend space-time to cut through those vast distances as if they were mere inches? Harnessing the power of space-time curvature can make what was once thought impossible possible.

The key to space-time curvature lies in our understanding of the curvature of space and time. By warping space-time through the power of gravity, we can navigate journeys that would otherwise have been impossible. It’s like creating shortcuts through the universe that save us valuable time and resources.

So how might we bend space-time to travel to the stars? One approach is the creation of a “warp bubble,” essentially stretching and compressing space-time to move a spaceship through space without being affected by the laws of relativity. Another approach is the use of “wormholes,” theoretical pathways through space-time that create shortcuts in the fabric of space itself.

Yet, there are challenges and limitations to consider. To create a warp bubble, for example, we would need an immense amount of energy, far beyond the capabilities of our current technology. The use of wormholes, on the other hand, would require us to manipulate a singularity or black hole, entities that we have yet to fully understand.

Nonetheless, the power of space-time curvature holds great promise and potential for interstellar travel. The possibilities of exploring distant planets and galaxies, meeting alien species, and discovering the unknown drive us forward to conquer the Herculean task of mastering the power of space-time curvature. But as we look towards the stars, we must remember that every breakthrough comes with its own set of risks and consequences. In the end, the race to harness space-time curvature is not just a scientific challenge, but a philosophical one as well.

III. The Practical Challenges of Space-Time Curvature

As we explore the possibilities of space-time curvature, we cannot ignore the practical challenges that come with it. One of the biggest challenges is developing the technology necessary to manipulate the fabric of space-time itself. It requires immense power, advanced computing, and a deep understanding of both physics and engineering.

Even if we can develop these technologies, the practical challenges of space-time curvature remain daunting. It increases the risk of incurring unforeseen errors and jeopardizing safety. Traveling through curved space-time often involves time dilation, which can cause physical and cognitive issues for travelers.

Furthermore, the manipulation of space-time curvature can have unintended consequences for the natural components of the universe. It could interfere with the gravity field of planets, disrupting their ecosystems and unique features. It could displace asteroids, meteors, and other celestial bodies, creating a cascade of effects.

Additionally, the complexity of space-time curvature and its potential to harm users makes it vital to implement safety protocols to mitigate the risks of use. The management of such protocols could be challenging, as it involves a high level of coordination, record-keeping, and oversight by experts in numerous fields.

IV. The Ethics and Implications of Space-Time Curvature

As we set our sights on the frontiers of space-time curvature, we must also consider the potential implications and ethical dilemmas of manipulating the universe. Altering the curvature of space-time raises serious concerns about the impact on the universe and its inhabitants.

One question that arises is the impact on the environment. As we reshape the universe, what are the consequences for the balance of the cosmos? We must consider the potential effects of altering gravitational fields, tearing the fabric of space and time, and the unknown ripple effects that could alter the universe as we know it.

Ethical questions also arise regarding who controls the technology and the implications of having such power. The risks of misuse, whether by governments or private entities, are significant. Will space-time curvature become a tool for domination, conflict, and subjugation? What are the consequences of holding such immense power, and who decides what is ethical and what is not?

Moreover, we must consider the impact on existence itself. Space-time curvature opens the door to questions of identity, reality, and the very nature of our existence. How do we maintain a sense of self in a universe where space and time are constantly being reshaped? How do we ensure the continuity of reality as we know it?

The reality of space-time curvature is not without its risks, challenges, and ethical considerations. But as we explore the frontiers of the universe, we must also grapple with these questions and address them head-on. As we chart a course forward, we must ensure that the power of space-time curvature is wielded for the greater good of humanity and the universe. Join us as we push the boundaries of science and technology, not just for the sake of exploration but for the sake of the universe and all its inhabitants.

V. The Future of Space-Time Curvature

The future of space-time curvature holds incredible possibilities, but also significant pitfalls. As we expand our knowledge and technology, we move towards a time when space-time curvature may be taken for granted, becoming a part of everyday life without us even realizing it.

With the ability to bend space-time at our fingertips, we will finally be able to push beyond the limits of our solar system and visit other stars, exploring the cosmos in ways never before possible. All this, coupled with the development of technologies like faster-than-light travel, quantum communication, and matter replication, brings us one step closer to achieving the impossible.

But with great power comes great responsibility. The ability to manipulate space-time creates unique ethical dilemmas, affecting the very nature of the universe. The consequences of our actions may resonate throughout the cosmos for millennia to come, posing unknown risks and unexpected dangers.

As society progresses towards a future with space-time curvature, we must ensure that such a technology is developed and implemented with careful consideration and respect. We must prioritize the safety of ourselves and others while exploring the possibilities of space-time curvature, understanding that the universe is a fragile and interconnected web of phenomena.

Despite the potential dangers, space-time curvature is poised to become one of the most revolutionary technologies in human history. Whether through the frontiers of travel or the exploration of new frontiers of knowledge, space-time curvature offers unparalleled possibilities for the future of humanity. But we must move forward with caution if we are to navigate the complex and uncertain terrain of space-time curvature.

VI. Conclusion

But with such possibility comes responsibility. We must not forget the ethical considerations of space-time curvature and must carefully consider the impact of our actions on the universe.

Despite the potential dangers, however, the case for exploring the frontiers of space-time curvature is strong. The opportunity to unravel the secrets of the universe and to push the boundaries of what we thought was impossible is too great to ignore.

As we continue to advance our technology and knowledge, we must explore the frontiers of space-time curvature with humility, wonder, and respect for the universe we seek to understand. The challenges we face are great, but the rewards are even greater.

So let us continue on this journey, unlocking the mysteries of the universe through the power of space-time curvature. The future holds incredible possibilities for humanity among the stars, and we must be ready to embrace them with open minds and hearts. For in this vast and infinite universe, it is through our exploration and understanding that we can truly find our place among the stars.

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Don’t stop me now! Superluminal travel in Einstein’s universe

Professor of Astrophysics, University of Sydney

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Geraint Lewis receives funding from the Australian Research Council.

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The story of the drawn-out development of Albert Einstein’s revolutionary rewrite of the laws of gravity has been told many times , but over the past 100 years it has given us extreme stars and black holes, expanding universes and gravitational mirages. Einstein also ensured you will never get lost, enabling the technology that helps your phone find your location with pinpoint accuracy!

Despite this scientific bounty, relativity appears to place strict limits on our exploration of Einstein’s universe, with any rocketship limited to travelling no faster than the speed of light. With the distance between stars measured in light years , and the distance across galaxies being hundreds of thousands of light years , not to mention the complexities of time dilation , establishing and running a galactic empire is going to be a drawn out and messy affair.

Bending time, bending space

I’ve already written that all is not lost, as in 1994 physicist Miguel Alcubierre discovered something wonderful: that by bending space and time just the right way will allow you to travel at any speed you want! While there are some downsides , with such a warp drive , the speed of light can be broken.

However, a couple of questions spring to mind, not least how can this superluminal bubble of a warp drive be consistent with the rules of relativity. And if it is, why did it take until the 1990s for someone to notice this was the case.

After E = mc² , the fact that nothing can move faster than light is probably the most common fact known about Einstein’s special theory of relativity. So just what can superluminal motion actual mean?

Let’s begin with what Einstein was actually saying about racing a light beam. To Einstein, the race takes place “locally”, such as in a laboratory, where you start a particle with mass and a light beam off at the same time. In this case, the light beam always gets ahead.

But in his special theory, the details of space and time are the same everywhere. More technically, the union of the two – known as spacetime – is flat, and we can compare the speed of a particle in the laboratory to a light ray somewhere off in the universe.

Things get messier in the general theory, as the presence of gravity ensures that the curvature of spacetime here is different to spacetime over there, and it is not possible to uniquely compare the speed of the particle in your laboratory to a light ray off in the distant universe. The only sensible comparison you can make is in your laboratory, and here the light ray still always wins.

The same is true in the curved spacetime of the warp drive. If your traveller in the warp bubble tries to race a particle and a light beam together, the light beam will always win.

An observer watching the bubble go by would calculate the light beam to be travelling faster than any light ray they create in their own laboratory. But this is not a problem, as it really makes no sense to compare velocities “there” with velocities “here”.

It is precisely this reason that cosmologists are happy to talk about galaxies receding from us faster than the speed of light due to the expansion of the universe .

Metric mechanics

Relativity had been around for almost 80 years before Alcubierre uncovered his solution. Why hadn’t people realised superluiminal travel was part of the theory?

The problem, of course, is the mathematically fiendish nature of Einstein’s equations. It is extremely difficult to calculate the curvature of spacetime and resultant action of gravity from any old distribution of mass and energy.

It can be mathematically simpler to define the properties of spacetime and then calculate the required distribution of mass and energy. And Alcubierre’s great insight was to realise a bubble could move at any speed as a rolling wave in spacetime.

However, such “metric mechanics” come with a downside: we may be able to find spacetimes that allow superluminal motion, but the required distribution of mass and energy may not be physically possible.

Those familiar with classical mechanics may remember that it is easier define a gravitational potential to determine forces, but these might require negative matter to physically exist .

The same is true for the warp drive solution, requiring material with a negative energy density to bend and shape space-time appropriately. And while we have hints that such properties exist in the universe, we have no idea if we will be able to mine and forge it to fashion our spaceships. So we may never be able to build an Alcubierre warp drive.

But we should not allow this to demoralise us! Alcubierre’s insights should inspire us to continue to bend and stretch spacetime, to tease out the possibles still hidden within the mathematics. Most may be physically impossible to ever realise, but with sufficient imagination, and a stroke of luck, we may stumble across our pathway to the stars.

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• Speed of light
• General relativity centenary
• Albert Einstein

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We Can't Alter The Flow of Time But, According to Physics, We Can Bend It

Time travel is much more than a dream. it's science..

Traveling in Time

Most of us have dreamed of traveling through time, backward or forwards, faster than those around us. And surprisingly, recent work has shown us that time travel is far more than just a dream. In fact, a number of researchers have explored, and are currently exploring, the legitimacy of time travel. While they haven't quite gotten to the point where they are able to time travel themselves—these researchers  have found some concrete science backing it up.

This past June, I met with  James Beacham , a particle physicist at the European Organization for Nuclear Research (CERN), at Brain Bar Budapest, a festival focused on the future, to talk about the ways in which time travel has enraptured humanity and discuss both the logistical and technical potential of time travel.

Beacham began by outlining the ways that, according to Einstein's theories, time travel is technically possible through a number of different methods.

One proposed method of time travel is via wormholes. “We know that space can be bent. If space can be bent by, say, gravity, then spacetime can be bent," Beacham said. To clarify, space is the three-dimensional body in which all things in the universe move. Spacetime, however, is the combined concepts of space and time into a four-dimensional continuum. You may have even seen spacetime portrayed as a fabric , manipulated by energy. If spacetime can be bent, Beacham continued, it's theoretically possible that time can be bent.

Making Time Travel A Reality

This concept of bending spacetime  sprung from Einstein’s theory of General Relativity , which introduced the idea that  wormholes could, in theory, act as a bridge between two points  that would otherwise be very distant. Because of spacetime's flexibility, a wormhole could link two different points in its fabric.

Recently, evidence for this theory has moved beyond the strictly theoretical.   A couple of years ago, scientists  built what they described as a "wormhole." Their model, however, created a portal for magnetic fields. As  Smithsonian outlined, "if another magnetic field travels through the wormhole, it appears to leave space altogether, only showing up at either end."

So it doesn't exactly teleport particles (or people) across spacetime, but it does highlight the continual advances that are being made in our ability to manipulate the various fundamental forces in our universe, and ultimately, the manipulation of this force is an important step towards creating a simplified wormhole that would allow us to send electromagnetic waves through an invisible tunnel. Perhaps, one day, we will be able to manipulate spacetime in a similar manner.

So while wormholes remain theoretically possible and important steps are being made, wormholes in spacetime, specifically, have yet to be observed or created.

Another potential method of time travel is time dilation. Einstein's theories predicted that time passes differently throughout the universe. We now know this to be true— clocks tick slower on the International Space Station (ISS) than they do here on Earth, for example. This happens because time moves slower for objects that are near strong gravitational fields (such as Earth) than for objects further from these fields, like the ISS.  

So by spending time off Earth's surface and returning at a later point, a human could, in a sense, fast forward through time. If you could get close to a black hole, because there are such strong gravitational forces in the vicinity, time would slow to a mesmerizing degree. Thousands of Earth-years might pass by while only a few seconds tick by near a supermassive black hole.

Time dilation also comes into play where speed is concerned. If we were to, say, travel at 95% of the speed of light, time would slow down dramatically. So again, thousands of Earth-years could pass by in what the traveler experiences as just a few moments.

And this is just the beginning, as there are a number of different ways in which we could make time travel into a reality. Scientists from various disciplines are investigating different methods for us to make more dramatic jumps through time, l ike using circulating light beams,  which can be created through the use of gamma and magnetic fields to twist space and cause time to be twisted. Other methods include  quantum tunneling and hypothetical cosmic strings.

Of course, just because something is theoretically possible doesn't mean it's technically feasible. At least, not yet. We can't make wormholes, and we can't travel near the speed of light. But there is hope that we could achieve these things in the very near future. "We could possibly address things about time travel and understand the basic nature of time with the research that we do now. Or at least, in the next 50 to 100 years," Beacham said.

Yet, we must acknowledge the possibility that moving back and forth through time may be contrary to the laws of physics . Still, that doesn't mean we shouldn't try.  As Stephen Hawking famously wrote in his autobiography , "Even if it turns out that time travel is impossible, it is important that we understand why it is impossible."

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This Trick Flips Space and Time

By Meddling With Spacetime Dimensions, We Could Finally Reach Warp Speed

New research shows that the “superluminal observer” needs three separate time dimensions for a warp-speed math trick that would please even Galileo.

✅ Quick Facts:

• In new research, the lead scientist explains why just one space and one time aren’t enough for this scenario.
• Symmetry is a physics concept that goes all the way back to Galileo’s time.

The secret to faster-than-light physics could be to double down on the number of dimensions. Specifically, the solution may lie in three dimensions of time , with just one representing space. The math is deep and complicated, but the ideas may be within our grasp after all. And there’s one math trick at superspeeds that may just “flip” your lid.

The key idea at play is that of a “superluminal observer,” according to research published in December 2022 in the journal Classical and Quantum Gravity. “Superluminal” means faster than light, from super - meaning “more” or “most,” and - luminal like, well, Lumière from Beauty and the Beast, and the lumens that power your home movie projector. The superluminal observer is a hypothetical thing that is looking at the universe while traveling faster than light. It’s you in your Star Trek warp-speed shuttle.

Superluminal observers are cool because, in a way, they marry together two very different sides of physics: general relativity and quantum mechanics . General relativity is the work embodied by Albert Einstein, which governs how spacetime functions as bodies move around the universe at subluminal, or slower than light, speeds. Quantum mechanics explains how subatomic particles behave, or don’t behave, in very strange ways on the smallest of scales.

The research team—led by theoretical physicist Andrzej Dragan of the University of Warsaw and the National University of Singapore—has theorized that many parts of quantum physics, like indeterminism and superposition , can be explained if you take general relativity and apply its principles to the superluminal observer. In other words, how messy does spacetime get if we take our shuttle up to warp speed? Is everything suddenly in multiple places at once?

Dragan’s new work indicates that it’s at least a possibility. Perhaps more interestingly, the way general relativity becomes quantum phenomena at speeds greater than light doesn’t seem to introduce any causal paradoxes. In earlier work , published in the New Journal of Physics in March 2020, Dragan and his coauthor studied “just” one space dimension and one time dimension, known as 1+1. In the new paper, the researchers upped the ante to include one space dimension and three time dimensions, or 1+3.

When Time and Space Flip Math

Why do we need three time dimensions? To understand, we have to talk about some math. “[D]espite our common perception, time and space are strikingly similar according to relativity, and mathematically the only difference between them is the minus sign somewhere in the equations,” Dragan explains to Popular Mechanics in an email. That’s a small difference in complicated math, but think of the algebra example of the difference of two squares: x² - 16, for example, is the result of (x - 4)(x + 4). With one flipped sign, the middle term in the polynomial falls away.

But when the observer is going faster than the speed of light, the difference in signs also changes. That’s because time and space must flip in the math. “The time of the superluminal observer becomes space of the subluminal one, and their space becomes time,” Dragan says. In other words, the regular, non-light-speed observer’s space and time turn into the time and space, relatively, of the faster-than-light observer. “So their corresponding signs have to interchange.”

In a 1+1 scenario, that means the two dimensions are the same, making it redundant. If 50 = 50, does it matter which 50 is which? (In logic, we call this a tautology.) That means that if we want to truly study space and time as different things, we have to add a second “set” of two dimensions: space and time 1, together, represent space; while time 2 and time 3, together, represent time . It’s not quite the difference of two squares, but we have two balanced sets of dimensions.

The Symmetry in Physics

There’s another interesting aspect to this research, because Dragan’s team wants to show that even at superluminal speeds, physics shows symmetry.

“The idea of symmetry in physics can be traced back to Galileo,” Dragan says. “He noticed that no matter what velocity we move at, as long as that velocity is constant, our physics remains the same. A parrot flying in a moving ship experiences the same dynamical laws as at ‘rest’ on Earth.”

✅ Galileo Galilei was an influential Italian scientist who lived during the 16th and 17th centuries. As an elderly man, he received a life sentence for going public with his belief that Earth orbited the sun!

But our conceptions of physics are limited by the long-running (and reasonable!) belief that nothing can travel faster than light, Dragan explains. That means the superluminal observer, by definition, exists as a kind of exception into which we must work to extend the idea of symmetry. Does it make sense that a superluminal observer would still be subject to symmetry? Is the parrot traveling faster than light still the same as the parrot in the ship or on Earth?

“We argued that this additional limiting assumption isn’t necessary,” Dragan says. He believes symmetry may extend into faster-than-light speeds, and our parrot friend would be just as affected by the same laws of physics while traveling in the warp-speed shuttle.

Toward a Grand Unified Theory

So, this paper isn’t about traveling at warp speed, but instead an analysis of physics to show how we can bring two very different physics branches together. Why is that, itself, so important?

“The idea of more than one time dimension has been considered by others over the years, so that particular premise is not novel,” Harold “Sonny” White, a onetime NASA physicist and the founder of the Limitless Space Institute (LSI), a group that funds and promotes far-out space travel and physics research, tells Popular Mechanics . “But the mathematical framework developed by the authors in this published paper is unique. It would seem the authors’ perceived benefit from the effort is that it establishes a mathematical basis for why we need a field theoretical framework.”

What is a field theoretical framework? It’s the big picture of physics that can bring everything together. “[I]f we envision the standard models of physics as a Venn diagram, there would be two circles side-by-side that touch at a single tangent point,” White explains. “The idea of a grand unified field theory might be envisioned as a larger circle that encircles both the smaller circles.”

By showing their work, these researchers have pointed out a really specific way in which one big basket of physics—rather than two baskets that we aren’t sure how to carry at the same time—would make more sense in practical and mathematical terms.

Okay, sure, you may be thinking: all this superluminal jabberwocky is interesting. But warp speed itself is science fiction, right? (At least for now: White’s LSI funds education that may eventually lead us elsewhere.) The superluminal observer is just a thought exercise ... right?

Dragan isn’t so sure. “The last remaining question is whether superluminal objects are only a mathematical possibility, or they actually exist in reality,” he concludes. “We believe the latter to be that case, and that is the purpose of our further research.”

That means our warp-speed shuttle, once the most far-out thing science fiction writers could even imagine, could embody an elegant theory that brings together two very different kinds of physics. Indeed, objects in the superluminal mirror may be closer than they appear.

Caroline Delbert is a writer, avid reader, and contributing editor at Pop Mech. She's also an enthusiast of just about everything. Her favorite topics include nuclear energy, cosmology, math of everyday things, and the philosophy of it all. 

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Star Trek-style warp drive may be possible

Travelling faster than the speed of light, zooming to other planets with warp drive and bending the fabric of space-time itself may all be possible in the near future. Scientists at NASA are working to make Star Trek-style warp drive a reality.

NASA physicist Harold White presented his findings at this year’s 100 Year Starship Symposium , a government-funded program geared toward exploring and creating interstellar travel within the next 100 years.

White’s research is a further look into Mexican physicist Miguel Alcubierre’s ideas from 1994. Alcubierre theorized that warp drive could be achieved by creating enough energy to bypass an actual need to travel faster than the speed of light (which is thought to be impossible), by bending space-time itself and traveling through the wrinkle. Alcubierre’s problem was the amount of energy that it would take to create this bend is more energy than exists in the universe.

However, White says he’s reconfigured the equations to only need a reasonable amount of energy.

White and his team are already testing small-scale ways to create space-time warps. 

Mollie Paige is an intern working at the Toronto Standard. You can follow her on twitter  @MolliePB

For more, follow us on Twitter  @TorontoStandard  and subscribe to our  newsletter .

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• Space & time

Understanding gravity—warps and ripples in space and time

Gravity allows for falling apples, our day/night cycle, curved starlight, our planets and stars, and even time travel ...

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• Isaac Newton described the effects of gravity, but didn’t propose a mechanism for how it worked
• Albert Einstein proposed that massive objects warp and curve the universe, resulting in other objects moving on or orbiting along those curves—and that this is what we experience as gravity
• This theory, general relativity, has led to a number of predictions that have held up to experimental testing
• One prediction of this theory is that ‘gravitational waves’ ripple through the universe, but Einstein thought they would be too small to detect
• In February 2016 the direct measurement of gravitational waves was announced. This provides us with a new method for exploring the universe
• In its current form, general relativity is incompatible with quantum mechanics—signalling that a shift in our understanding may be on the horizon

Take a moment to observe the effects of gravity. Lift your arm and feel how you are compelled to drop it again. Gravity is always there—it’s stable, it’s permanent, it’s unchanging. Or is it?

For hundreds of years we’ve been able to predict the effects of gravity. But we had no idea how it worked until Einstein stepped in, painting a strange and unintuitive picture. In Einstein’s view, gravity is far from a static, unchanging force—it is a fundamental part of the structure of the universe, which curves and twists and ripples as objects move and rotate and jostle about.

The predictions of Einstein’s theories have been validated time and time again. And now, 100 years after the formulation of his theory of gravity, another one of its predictions—gravitational waves—has been directly measured, despite Einstein’s belief that we’d never be able to do this.

In this topic we’ll explore Einstein’s dynamic vision of gravity, including the recently measured phenomenon of gravitational waves. If you’re unfamiliar with relativity GLOSSARY relativity The general idea that the results of experiments do not depend on the states of motion of observers , some of these concepts may boggle your mind. If so, we encourage you to keep pushing onwards, as it’s one of the greatest journeys in the history of science.

Let’s begin by looking at why Newton’s laws didn’t provide a complete picture of gravity.

Newton and the laws of gravity

Newton published one of the most celebrated works of science, the Principia , in 1687. In it, he described that the force that pulls objects towards the ground is the very same force that underlies the motion of the planets and stars.

To come to this conclusion, Newton imagined taking an object far from the surface of Earth, and throwing it. If you throw it with too little momentum, it will fall towards Earth, captured by gravity like we are ourselves. If you throw it with too much momentum, it will speed away from the planet, beginning its journey into the reaches of space. But with exactly the right momentum, you can throw it so that it falls continuously around Earth, around and around in an eternal tug-of-war. The object tries to continue in the path you threw it, but gravity keeps on pulling it back in. With the right balance, the object is now in orbit around Earth—just like the moon, or like Earth around the sun.

Newton formulated this insight into a mathematical equation, known today as the law of universal gravitation. When combined with knowledge of geometry and Newton’s other equations of motion, we can use it to make predictions about the movement of the planets, or the paths of comets, or how much force is needed to get a rocket to the moon.

We acknowledge Newton not just because of his idea, but because he formulated that idea into an equation that made predictions with greater accuracy than ever before. But it wasn’t perfect—Newton’s equations produced some incorrect predictions, and, more importantly, he didn’t describe how gravity works the way it does. Newton was well aware of this when he said,

Gravity must be caused by an agent acting constantly according to certain laws; but whether this agent be material or immaterial, I have left to the consideration of my readers. Isaac Newton

Distortions in space and time

More than 200 years after the  Principia was published, the world was still without an understanding of gravity’s mechanism. Enter Albert Einstein—a man who was to change the world in so many ways. But before we get to his work, we’ll have to take one more detour.

You can’t tell if you’re moving (at a constant rate)

In 1632, even before Newton published his now-famous work, Galileo Galilei wrote about the relative motion of objects familiar in his time: ships. 

If you are in a closed room on a ship sailing at a constant speed and the ride is perfectly smooth, objects behave as they would on land. There’s no physical experiment you could conduct to tell whether you’re moving or stationary (assuming you’re not peeking out of a porthole). This is the core idea behind relativity, and is the same reason why we don’t feel our planet’s movement around the sun, or our solar system’s movement through the galaxy.

Space and time are linked

Almost 300 years after Galileo, Einstein pondered the consequences of relativity in the context of an important factor: the speed of light. He wasn’t the only person who was pondering these topics—other physicists at the time were aware that there were unanswered questions on this front. But it was Einstein who formulated a theory—his theory of special relativity GLOSSARY special relativity Einstein’s theory regarding the relationship between space and time, the constancy of the speed of light, and the fact that physics must be the same in all uniform states of motion —to explain existing phenomena and create new predictions. At first, special relativity may  not seem to have much to do with gravity, but it was an essential stepping stone for Einstein for understanding gravity.

Moving clocks tick more slowly

Experiments during Einstein’s time had shown that the speed of light appeared to be constant. No matter how fast you try and catch up, light always appears to zip away from you at almost 300,000,000 metres per second.

Why is this important? Well, let’s imagine constructing a clock out of light itself. Two mirrors are placed opposite each other, and a “tick” of the clock is the time it takes for a particle of light to travel from one side to the other and back.

Imagining a light clock

(in slow motion)

“Ticks” of the clock

Now let’s imagine that your friend, who’s on a spaceship zipping past Earth, has one of these clocks. For your friend, the clock seems to be working normally—the particles of light travel up and down, as expected, and time proceeds in its usual fashion. But from your perspective, watching the ship pass by, the light is moving both up and down and to the side, with the ship. The light travels a longer distance with each tick.

Stationary vs moving light clocks

As seen from inside the spaceship, as seen by a stationary observer.

So if, for the space traveller, light travels at 300,000,000 m/s but only has to travel up and down; and to the Earthbound observer, light travels at 300,000,000 m/s, but must travel a longer, diagonal distance; then for the Earthbound observer, the clock takes longer to “tick”. 

This effect is called time dilation GLOSSARY time dilation The slowing down of time for one observer relative to another . The faster you travel through space, the slower you travel through time.

Perspective matters

But whose time is really slowed down? Is it the person on Earth, watching his friend zip past in her spaceship? Or the astronaut, who argues she ’ s staying still while the Earth flies by?

Strangely enough, both viewpoints are valid—but only while both are in constant motion.

To illustrate, let’s assume that when the astronaut left Earth, she and her friend were the same age. When she leaves, the spaceship accelerates away from Earth. When she returns, the spaceship decelerates to avoid a crash landing. In both leaving and returning, the spaceship changes its frame of reference GLOSSARY frame of reference The physical environment of an observer that involves their state of motion. A person travelling in one car is in a different frame of reference than someone travelling in a car going a different speed or direction, or a pedestrian at the side of the road, or someone travelling overhead in a plane, etc. , and our astronaut can feel the change of motion. Experiments conducted inside the spaceship during acceleration and deceleration would show that something’s changing. This breaks the symmetry of the situation, and when the spaceship lands back on Earth, our astronaut really will be younger than her Earthbound counterpart. 

The effects are only noticeable if they were travelling really, really fast—but it’s still true to say that when today’s astronauts and fighter pilots return from a high-speed mission, they will have aged a teeny-tiny bit less than the rest of us did during that mission.

The four dimensions of spacetime

Following from this, rather than thinking of three dimensions of space and one separate dimension of time, we can consider them as four dimensions of “spacetime”. The faster you travel through space, the slower you travel through time, and vice versa.

Moving objects contract in space

Another consequence of special relativity is that fast-moving objects appear to contract in size, in the direction of their motion. (And again, this gets flipped around depending on whose perspective you’re looking from.)

This follows from the distortion of time—after all, you can measure the length of something by the amount of space something travels through time (e.g. light-years, light-seconds). And while it’s tricky to imagine measuring the length of a moving object from someone else’s perspective, length contraction is a real, physical effect, and not just an outcome of imprecise measurements.

Unlike the age differences that can arise from time dilation, there are no residual effects due to length contraction once the moving object and the observer are reunited.

Understanding gravity

Einstein’s description of gravity leads to situations just as bizarre as special relativity—time travel included!

Acceleration and gravity can be indistinguishable

Imagine waking up in a spaceship, accelerating through space. Just as you’re pushed back in the seat of an accelerating car, the accelerating spaceship pushes you to the side opposite the one it’s accelerating towards. At a certain rate of acceleration, a set of scales could tell you that you weigh exactly the same as you do when you’re at home on Earth.

Is there any physical experiment you could do within the confines of your spaceship to tell whether you really were accelerating through space (assuming there were no windows to look out from), or if, instead, you were inside a spaceship stationary on the surface of Earth? Einstein said no—just as Galileo imagined the indistinguishability between a person inside a smooth-sailing ship (confined without windows) and a person on land, Einstein realised that the effects of acceleration and gravity were indistinguishable too. This is called the equivalence principle GLOSSARY equivalence principle The effects of being in a gravitational field are indistinguishable from the effects of being in an accelerated frame of reference .

Space warps under accelerated motion

Once Einstein had formulated the equivalence principle, gravity became less mysterious. He could apply his knowledge of acceleration to better understand gravity.

You may know that acceleration doesn’t always mean a change in speed, like when you speed up in a car, pushing you to the back of your seat. It can also mean a change in direction, like when you go round a roundabout, causing you to lean towards the side of the car. 

To extend this further, let’s imagine a cylindrical carnival ride where you and your fellow passengers are pinned to the outer surface. The cylinder is rotated faster and faster until the acceleration eases and the movement stays constant. But even once the speed is constant, you still feel the accelerated motion—you feel yourself being pinned to the outer edge of the ride.

If this spinning ride was large enough and moving at a fast enough rate, you’d start to notice some bizarre effects inside the ride itself, not just from the point of view of someone standing outside it. 

With every rotation, those at the edge of the ride travel the full circumference of the cylinder—while at the very centre, there’s hardly any movement at all. So if someone stood in the very centre of the ride (perhaps held by a brace, stopping them from falling to the edge), they would notice all those weird effects we saw under special relativity—that those on the edge will contract in length, and their clocks will tick at a slower rate.

Gravity is the curvature of spacetime

The equivalence principle tells us that the effects of gravity and acceleration are indistinguishable. In thinking about the example of the cylindrical ride, we see that accelerated motion can warp space and time. It is here that Einstein connected the dots to suggest that gravity is the warping of space and time. Gravity is the curvature of the universe, caused by massive bodies, which determines the path that objects travel. That curvature is dynamical, moving as those objects move.

This theory,  general relativity GLOSSARY general relativity Einstein’s theory of gravity , predicts everything from the orbits of stars to the collision of asteroids to apples falling from a branch to the earth—everything we have come to expect from a theory of gravity.

Spacetime grips mass, telling it how to move... Mass grips spacetime, telling it how to curve Physicist John Wheeler

The success of general relativity

Just as Newton’s formulation of the laws of gravity were valuable because of their predictive power, the same goes for those of Einstein. To date, his predictions—as strange as they may sound—have all stood the test of time. 

Gravity bends light

Although light seems to be pretty unfazed by gravity, Einstein predicted that this is not always the case. Light travels through spacetime, which can be warped and curved—so light should dip and curve in the presence of massive objects. This effect is known as gravitational lensing GLOSSARY gravitational lensing The bending of light caused by gravity .

This effect was first observed in 1919, analysing starlight during a solar eclipse. Astronomers found that starlight that passed very close to the sun was very slightly offset in position compared to the same starlight when measured at night. Today, with more powerful telescopes, we ’ve found evidence of gravitational lensing all over the place—including entire galaxies that distort the light of other galaxies.

Gravity slows the passage of time

Similar to how the passage of time is changed under special relativity, general relativity predicts that massive objects will also dilate time. The more massive the object, the more noticeable the effect.

This was used as a plot device in the 2014 science-fiction film Interstellar, but it’s not fiction. Gravitational time dilation has been confirmed via experiments of extremely precise atomic clocks that lose sync with other clocks depending how close or far away they are from the Earth’s surface. So while we’re yet to send a crew of astronauts near a black hole GLOSSARY black hole Extremely massive and dense objects with so much gravity that not even light can escape , we know that being in the vicinity of such a massive object would mean that when they’d return, they will have aged noticeably less than the rest of us.

GPS technology needs offsetting

While the application of Einstein’s theories may seem so far from everyday experience, consider this: satellite positioning technology—whether used on your phone, or by pilots in planes, or for logistics and industry the world over—would not work without our understanding of relativity.

The Global Positioning System (GPS) consists of satellites that orbit Earth 20,000 km above ground at a speed of around 14,000 km/h. On board each satellite is an atomic clock, and your position on the planet can be determined by checking the time broadcast by the satellites above you and comparing those times against the known position of each satellite. Relativity tells us that these clocks will tick more slowly than those on Earth—so if we weren’t able to correct for these differences, we wouldn’t be able to pinpoint our location on Earth to an accuracy down to a few metres. Seen another way, the accuracy of GPS acts as further proof of Einstein’s theories.

Moving and rotating objects make additional twists and warps in spacetime

Two more predictions of general relativity are the geodetic effect GLOSSARY geodetic effect The additional distortion of spacetime caused by moving objects and the frame-dragging effect GLOSSARY frame-dragging effect The additional distortion of spacetime caused by rotating objects . Both effects have been confirmed by a range of experiments , including the Gravity Probe B satellite. Equipped with extremely sensitive gyroscopes, this satellite measured the tiny twists and warps in spacetime made by Earth as it moves and rotates through space.

The universe ripples as objects move and collide

Since the curvature of spacetime is dynamical, moving objects should create ripples in space that permeate through the universe. Most of these ripples are too small to notice, but the more extreme the event, the higher the chance we can detect it. These ripples have been named gravitational waves, and we’ve found them.

Gravitational waves

Echoes of cataclysm from far away.

Imagine two very massive objects, such as black holes. If those objects were to collide, they could potentially create an extreme disturbance in the fabric of spacetime, moving outwards like the ripples in a pond. But how far away could such waves be felt? Einstein predicted that gravitational waves existed, but believed they would be too small to detect by the time they reached us here on Earth.

So it was with great excitement that on February 11 2016, the scientific community was abuzz with the announcement that a gravitational wave GLOSSARY gravitational wave Ripples in spacetime that propagate outwards like waves had been detected. We needed instruments capable of detecting a signal one-ten-thousandth the diameter of a proton (10 -19 meter). That’s exactly what the Laser Interferometer Gravitational-Wave Observatory (LIGO) equipment, operated by the California Institute of Technology and the Massachusetts Institute of Technology, can do. 

The LIGO experiment

In the LIGO experiment, a laser is directed into a large tunnel structure. The laser beam is split so that half of it travels down one of the 4-kilometre-long ‘arms’, and the other half travels down the other 4-kilometre arm at the exact same time. At the end of each arm, a mirror reflects the light from the laser back to where it came from, and the two beams merge back into one. 

Normally, the laser beams should recombine at exactly the same time. But if a gravitational wave comes rippling through space while the detectors are switched on, that ripple will stretch one arm of the L-shaped structure before stretching the other. The gravitational wave distorts the passage of the light, resulting in a particular kind of interference light pattern detected at the end.

On 11 February 2016, the LIGO teams announced the direct discovery of a gravitational wave matching the signal predicted from the collision of two black holes.

If the February 2016 news of the discovery of gravitational waves caused you to feel a sense of déjà vu, it’s probably because of a similar announcement in March 2014. Astronomers at the Background Imaging of Cosmic Extragalactic Polarization (BICEP2) telescope had supposedly discovered evidence of gravitational waves, but that evidence was later recalled, as it did not pass closer scrutiny.

The methods used in in the BICEP2 study were very different from those used in the LIGO experiment. Rather than listening for the direct signal of a gravitational wave as it rolled past our planet (the setup at LIGO), the BICEP2 team analysed swirls of light within the cosmic microwave background GLOSSARY cosmic microwave background The faint remnant of light that permeates the whole universe, left over from the heat of the big bang . They theorised that during the early expansion of the universe, tiny gravitational waves would have disturbed the light around them, which would have been amplified into a larger pattern as the universe expanded, coalescing into these patterns in the cosmic microwave background.

The announcement was made before the BICEP2 data went through more rigorous analysis and feedback from their colleagues. The experiment’s claims were questioned, and then, later, retracted. Instead, it looked likely that the patterns of light were not caused by gravitational waves, but instead by the dust inside our own galaxy as it interacted with magnetic fields.

Gravitational wave astronomy

The successful LIGO experiment has ushered in a new era of astronomy. Before now, astronomers have largely focused on the study of the electromagnetic spectrum (including light and radio waves). We’ve been able to discover a huge amount about our universe through that work, but now we have a brand new way to study the universe. 

The discovery of gravitational waves gives astronomers a new ‘sense’ with which to explore the universe, and so there will almost certainly be surprises ahead. What we do know is that this technique will allow us to better understand the most massive objects in the universe such as black holes, neutron stars, and supernovae; and it will provide us with a new window to study how the universe formed.

Is our understanding complete?

While Einstein’s theory of gravity has been validated by experiment after experiment, this does not mean our understanding is complete. In fact, we know that something’s not quite right. 

One unanswered question is whether or not gravity is propagated by the graviton—the proposed (but so-far undetected) particle responsible for gravitational interactions. Even more pressing, we know that general relativity is, in its current form, incompatible with the other pillar of modern physics: quantum mechanics GLOSSARY quantum mechanics A branch of physics that explains how the universe works on incredibly tiny scales (atomic and subatomic) . This is an indication that one or both theories are incomplete, or that we’re missing some other key component.

Whether or not Einstein’s theory of gravity will remain unchanged is not known. But it has produced many unexpected, unintuitive predictions that have been confirmed again and again for over a hundred years. That’s the sign of a great scientific theory—it makes predictions that may not be able to be proven at the time, but stand up to rigorous testing. This has been one of the greatest journeys in the history of science, involving not just Newton and Einstein, but thinkers and doers all around the world who have worked to put these theories to the test.

Even so, the schism between relativity and quantum mechanics remains. As for what’s next, no one knows with certainty. However, there are a few theories—stringy, loopy, multi-dimensional theories—unproven but with promise of becoming the next milestone in understanding our cosmos.

The dark stuff of our universe

Exploring the unknown with the square kilometre array, is earth safe from asteroids and comets.

• solar system

Time travel: Is it possible?

Science says time travel is possible, but probably not in the way you're thinking.

Albert Einstein's theory

• General relativity and GPS
• Wormhole travel
• Alternate theories

Science fiction

Is time travel possible? Short answer: Yes, and you're doing it right now — hurtling into the future at the impressive rate of one second per second. 

You're pretty much always moving through time at the same speed, whether you're watching paint dry or wishing you had more hours to visit with a friend from out of town. 

But this isn't the kind of time travel that's captivated countless science fiction writers, or spurred a genre so extensive that Wikipedia lists over 400 titles in the category "Movies about Time Travel." In franchises like " Doctor Who ," " Star Trek ," and "Back to the Future" characters climb into some wild vehicle to blast into the past or spin into the future. Once the characters have traveled through time, they grapple with what happens if you change the past or present based on information from the future (which is where time travel stories intersect with the idea of parallel universes or alternate timelines). 

Related: The best sci-fi time machines ever

Although many people are fascinated by the idea of changing the past or seeing the future before it's due, no person has ever demonstrated the kind of back-and-forth time travel seen in science fiction or proposed a method of sending a person through significant periods of time that wouldn't destroy them on the way. And, as physicist Stephen Hawking pointed out in his book " Black Holes and Baby Universes" (Bantam, 1994), "The best evidence we have that time travel is not possible, and never will be, is that we have not been invaded by hordes of tourists from the future."

Science does support some amount of time-bending, though. For example, physicist Albert Einstein 's theory of special relativity proposes that time is an illusion that moves relative to an observer. An observer traveling near the speed of light will experience time, with all its aftereffects (boredom, aging, etc.) much more slowly than an observer at rest. That's why astronaut Scott Kelly aged ever so slightly less over the course of a year in orbit than his twin brother who stayed here on Earth. 

Related: Controversially, physicist argues that time is real

There are other scientific theories about time travel, including some weird physics that arise around wormholes , black holes and string theory . For the most part, though, time travel remains the domain of an ever-growing array of science fiction books, movies, television shows, comics, video games and more. 

Einstein developed his theory of special relativity in 1905. Along with his later expansion, the theory of general relativity , it has become one of the foundational tenets of modern physics. Special relativity describes the relationship between space and time for objects moving at constant speeds in a straight line. 

The short version of the theory is deceptively simple. First, all things are measured in relation to something else — that is to say, there is no "absolute" frame of reference. Second, the speed of light is constant. It stays the same no matter what, and no matter where it's measured from. And third, nothing can go faster than the speed of light.

From those simple tenets unfolds actual, real-life time travel. An observer traveling at high velocity will experience time at a slower rate than an observer who isn't speeding through space. 

While we don't accelerate humans to near-light-speed, we do send them swinging around the planet at 17,500 mph (28,160 km/h) aboard the International Space Station . Astronaut Scott Kelly was born after his twin brother, and fellow astronaut, Mark Kelly . Scott Kelly spent 520 days in orbit, while Mark logged 54 days in space. The difference in the speed at which they experienced time over the course of their lifetimes has actually widened the age gap between the two men.

"So, where[as] I used to be just 6 minutes older, now I am 6 minutes and 5 milliseconds older," Mark Kelly said in a panel discussion on July 12, 2020, Space.com previously reported . "Now I've got that over his head."

General relativity and GPS time travel

The difference that low earth orbit makes in an astronaut's life span may be negligible — better suited for jokes among siblings than actual life extension or visiting the distant future — but the dilation in time between people on Earth and GPS satellites flying through space does make a difference. 

Read more: Can we stop time?

The Global Positioning System , or GPS, helps us know exactly where we are by communicating with a network of a few dozen satellites positioned in a high Earth orbit. The satellites circle the planet from 12,500 miles (20,100 kilometers) away, moving at 8,700 mph (14,000 km/h). 

According to special relativity, the faster an object moves relative to another object, the slower that first object experiences time. For GPS satellites with atomic clocks, this effect cuts 7 microseconds, or 7 millionths of a second, off each day, according to the American Physical Society publication Physics Central .  

Read more: Could Star Trek's faster-than-light warp drive actually work?

Then, according to general relativity, clocks closer to the center of a large gravitational mass like Earth tick more slowly than those farther away. So, because the GPS satellites are much farther from the center of Earth compared to clocks on the surface, Physics Central added, that adds another 45 microseconds onto the GPS satellite clocks each day. Combined with the negative 7 microseconds from the special relativity calculation, the net result is an added 38 microseconds. 

This means that in order to maintain the accuracy needed to pinpoint your car or phone — or, since the system is run by the U.S. Department of Defense, a military drone — engineers must account for an extra 38 microseconds in each satellite's day. The atomic clocks onboard don’t tick over to the next day until they have run 38 microseconds longer than comparable clocks on Earth.

Given those numbers, it would take more than seven years for the atomic clock in a GPS satellite to un-sync itself from an Earth clock by more than a blink of an eye. (We did the math: If you estimate a blink to last at least 100,000 microseconds, as the Harvard Database of Useful Biological Numbers does, it would take thousands of days for those 38 microsecond shifts to add up.) 

This kind of time travel may seem as negligible as the Kelly brothers' age gap, but given the hyper-accuracy of modern GPS technology, it actually does matter. If it can communicate with the satellites whizzing overhead, your phone can nail down your location in space and time with incredible accuracy. 

Can wormholes take us back in time?

General relativity might also provide scenarios that could allow travelers to go back in time, according to NASA . But the physical reality of those time-travel methods is no piece of cake. 

Wormholes are theoretical "tunnels" through the fabric of space-time that could connect different moments or locations in reality to others. Also known as Einstein-Rosen bridges or white holes, as opposed to black holes, speculation about wormholes abounds. But despite taking up a lot of space (or space-time) in science fiction, no wormholes of any kind have been identified in real life. 

Related: Best time travel movies

"The whole thing is very hypothetical at this point," Stephen Hsu, a professor of theoretical physics at the University of Oregon, told Space.com sister site Live Science . "No one thinks we're going to find a wormhole anytime soon."

Primordial wormholes are predicted to be just 10^-34 inches (10^-33 centimeters) at the tunnel's "mouth". Previously, they were expected to be too unstable for anything to be able to travel through them. However, a study claims that this is not the case, Live Science reported . 

The theory, which suggests that wormholes could work as viable space-time shortcuts, was described by physicist Pascal Koiran. As part of the study, Koiran used the Eddington-Finkelstein metric, as opposed to the Schwarzschild metric which has been used in the majority of previous analyses.

In the past, the path of a particle could not be traced through a hypothetical wormhole. However, using the Eddington-Finkelstein metric, the physicist was able to achieve just that.

Koiran's paper was described in October 2021, in the preprint database arXiv , before being published in the Journal of Modern Physics D.

Alternate time travel theories

While Einstein's theories appear to make time travel difficult, some researchers have proposed other solutions that could allow jumps back and forth in time. These alternate theories share one major flaw: As far as scientists can tell, there's no way a person could survive the kind of gravitational pulling and pushing that each solution requires.

Infinite cylinder theory

Astronomer Frank Tipler proposed a mechanism (sometimes known as a Tipler Cylinder ) where one could take matter that is 10 times the sun's mass, then roll it into a very long, but very dense cylinder. The Anderson Institute , a time travel research organization, described the cylinder as "a black hole that has passed through a spaghetti factory."

After spinning this black hole spaghetti a few billion revolutions per minute, a spaceship nearby — following a very precise spiral around the cylinder — could travel backward in time on a "closed, time-like curve," according to the Anderson Institute. 

The major problem is that in order for the Tipler Cylinder to become reality, the cylinder would need to be infinitely long or be made of some unknown kind of matter. At least for the foreseeable future, endless interstellar pasta is beyond our reach.

Time donuts

Theoretical physicist Amos Ori at the Technion-Israel Institute of Technology in Haifa, Israel, proposed a model for a time machine made out of curved space-time — a donut-shaped vacuum surrounded by a sphere of normal matter.

"The machine is space-time itself," Ori told Live Science . "If we were to create an area with a warp like this in space that would enable time lines to close on themselves, it might enable future generations to return to visit our time."

Amos Ori is a theoretical physicist at the Technion-Israel Institute of Technology in Haifa, Israel. His research interests and publications span the fields of general relativity, black holes, gravitational waves and closed time lines.

There are a few caveats to Ori's time machine. First, visitors to the past wouldn't be able to travel to times earlier than the invention and construction of the time donut. Second, and more importantly, the invention and construction of this machine would depend on our ability to manipulate gravitational fields at will — a feat that may be theoretically possible but is certainly beyond our immediate reach.

Time travel has long occupied a significant place in fiction. Since as early as the "Mahabharata," an ancient Sanskrit epic poem compiled around 400 B.C., humans have dreamed of warping time, Lisa Yaszek, a professor of science fiction studies at the Georgia Institute of Technology in Atlanta, told Live Science .  

Every work of time-travel fiction creates its own version of space-time, glossing over one or more scientific hurdles and paradoxes to achieve its plot requirements. 

Some make a nod to research and physics, like " Interstellar ," a 2014 film directed by Christopher Nolan. In the movie, a character played by Matthew McConaughey spends a few hours on a planet orbiting a supermassive black hole, but because of time dilation, observers on Earth experience those hours as a matter of decades. 

Others take a more whimsical approach, like the "Doctor Who" television series. The series features the Doctor, an extraterrestrial "Time Lord" who travels in a spaceship resembling a blue British police box. "People assume," the Doctor explained in the show, "that time is a strict progression from cause to effect, but actually from a non-linear, non-subjective viewpoint, it's more like a big ball of wibbly-wobbly, timey-wimey stuff." 

Long-standing franchises like the "Star Trek" movies and television series, as well as comic universes like DC and Marvel Comics, revisit the idea of time travel over and over. 

Related: Marvel movies in order: chronological & release order

Here is an incomplete (and deeply subjective) list of some influential or notable works of time travel fiction:

Books about time travel:

• Rip Van Winkle (Cornelius S. Van Winkle, 1819) by Washington Irving
• A Christmas Carol (Chapman & Hall, 1843) by Charles Dickens
• The Time Machine (William Heinemann, 1895) by H. G. Wells
• A Connecticut Yankee in King Arthur's Court (Charles L. Webster and Co., 1889) by Mark Twain
• The Restaurant at the End of the Universe (Pan Books, 1980) by Douglas Adams
• A Tale of Time City (Methuen, 1987) by Diana Wynn Jones
• The Outlander series (Delacorte Press, 1991-present) by Diana Gabaldon
• Harry Potter and the Prisoner of Azkaban (Bloomsbury/Scholastic, 1999) by J. K. Rowling
• Thief of Time (Doubleday, 2001) by Terry Pratchett
• The Time Traveler's Wife (MacAdam/Cage, 2003) by Audrey Niffenegger
• All You Need is Kill (Shueisha, 2004) by Hiroshi Sakurazaka

Movies about time travel:

• Planet of the Apes (1968)
• Superman (1978)
• Time Bandits (1981)
• The Terminator (1984)
• Back to the Future series (1985, 1989, 1990)
• Star Trek IV: The Voyage Home (1986)
• Bill & Ted's Excellent Adventure (1989)
• Groundhog Day (1993)
• Galaxy Quest (1999)
• The Butterfly Effect (2004)
• 13 Going on 30 (2004)
• The Lake House (2006)
• Meet the Robinsons (2007)
• Hot Tub Time Machine (2010)
• Midnight in Paris (2011)
• Looper (2012)
• X-Men: Days of Future Past (2014)
• Edge of Tomorrow (2014)
• Interstellar (2014)
• Doctor Strange (2016)
• A Wrinkle in Time (2018)
• The Last Sharknado: It's About Time (2018)
• Avengers: Endgame (2019)
• Tenet (2020)
• Palm Springs (2020)
• Zach Snyder's Justice League (2021)
• The Tomorrow War (2021)

Television about time travel:

• Doctor Who (1963-present)
• The Twilight Zone (1959-1964) (multiple episodes)
• Star Trek (multiple series, multiple episodes)
• Samurai Jack (2001-2004)
• Lost (2004-2010)
• Phil of the Future (2004-2006)
• Steins;Gate (2011)
• Outlander (2014-2023)
• Loki (2021-present)

Games about time travel:

• Chrono Trigger (1995)
• TimeSplitters (2000-2005)
• Kingdom Hearts (2002-2019)
• Prince of Persia: Sands of Time (2003)
• God of War II (2007)
• Ratchet and Clank Future: A Crack In Time (2009)
• Sly Cooper: Thieves in Time (2013)
• Dishonored 2 (2016)
• Titanfall 2 (2016)
• Outer Wilds (2019)

Additional resources

Explore physicist Peter Millington's thoughts about Stephen Hawking's time travel theories at The Conversation . Check out a kid-friendly explanation of real-world time travel from NASA's Space Place . For an overview of time travel in fiction and the collective consciousness, read " Time Travel: A History " (Pantheon, 2016) by James Gleik. 

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Ailsa is a staff writer for How It Works magazine, where she writes science, technology, space, history and environment features. Based in the U.K., she graduated from the University of Stirling with a BA (Hons) journalism degree. Previously, Ailsa has written for Cardiff Times magazine, Psychology Now and numerous science bookazines. 

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8 Mind-Bending Facts About Outer Space

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Key Takeaways

• Two pieces of the same metal will stick together in space due to the absence of atmospheric oxygen, preventing oxidation and allowing the metals to cold weld in vacuum conditions.
• The Pistol Star, one of the most massive and luminous stars known, is located 25,000 light-years away and is 10 million times brighter than the sun, largely obscured from view by interstellar dust.
• The universe is so vast that there are more stars than grains of sand on Earth's beaches and deserts.

From time to time, we all gaze up at the stars and wonder about outer space. It can be an incredibly mind-blowing, beautiful, fascinating, exciting and even scary place to think about, as it is so incomprehensibly vast and unexplored and it contains so many secrets. We seemingly discover new things about outer space each year and there have been some astonishing accomplishments in recent times, yet we have barely dipped our toes in the water. These out-of-this-world 10 facts are sure to make your next stargazing experience a truly mind-bending one.

• If Two Pieces of the Same Metal Touch in Space, They Will Become Stuck Together
• The Pistol Star is 10 Million Times the Brightness of the Sun
• 99% of Our Solar System’s Mass is the Sun
• You Could Fit All the Other Planets in Our Solar System Between Earth and Our Moon
• There Are More Stars in the Universe Than There Are Grains of Sand on the Earth
• There is a Gigantic Body of Water Floating in Space
• It Takes Around 230 Million Years For Our Solar System to Orbit the Milky Way
• All the Stars, Galaxies and Planets Only Make Up About 4% of the Universe

8. If Two Pieces of the Same Metal Touch in Space, They Will Become Stuck Together

On Earth, if you were to touch two pieces of the same metal together you would simply be able to pull them apart, but this is not the case in outer space (provided they are perfectly smooth). On Earth there is oxygen in the atmosphere, which creates a very thin layer of oxidized metal, and this acts as a barrier between the two metals. There is no atmospheric oxygen in space, and consequently there is no barrier, so the two metals form a bond and become one. This is known as cold welding. This may sound like a complete nightmare in terms of spaceship construction and working on the International Space Station, but because the metals and tools will have come from Earth, it means that they will retain the coated layer and not become stuck together.

7. The Pistol Star is 10 Million Times the Brightness of the Sun

One of the most massive known stars in the universe is accepted to be the Pistol Star, which is located approximately 25,000 light years from Earth in the direction of Sagittarius, and is surrounded by the Pistol Nebula. The Pistol Star has a mass which is about 100-150 times that of the sun, and it is about 10 million times brighter too (making it one of the most luminous). It would be visible to the naked eye as a fourth magnitude star, but it is completely hidden from view due to interstellar dust. Despite this, 10% of its infrared light reaches this planet, and this makes it within reach of infrared telescopes. It is thought to have created the Pistol Nebula by expelling up to 10 solar masses of gas in giant outbursts around 4,000 to 6,000 years ago, but its exact age and future are unknown.

6. 99% of Our Solar System’s Mass is the Sun

The sun makes up an incredible 99.86% of the total mass in our solar system. Of the remaining percentage, 99% of this is made up of the four giant planets (Jupiter, Saturn, Neptune and Uranus). This leaves 0.002% for the remaining objects in the solar system, which includes little old Earth, the remaining terrestrial planets (Mercury, Venus and Mars), dwarf planets, moons, asteroids and comets. This puts into perspective just how small Earth is in our solar system, but mainly just how breathtakingly dominant the sun is. It has a radius 100 times that of Earth, which means about one million Earths could fit inside the sun. Around three-quarters of the sun’s enormous mass is hydrogen (its main fuel), with the rest largely comprised of helium. There are then smaller quantities of heavier elements, such as iron, neon, carbon and oxygen.

5. You Could Fit All the Other Planets in Our Solar System Between Earth and Our Moon

In terms of outer space, we generally think that the distance between Earth and our moon is quite small. Amazingly, it turns out that you could fit the other planets in our solar system within the average distance between the Earth and moon. The average distance is 384,400 km or 238,555 miles, and the diameter of the seven remaining planets added together would leave 8,030 km or 4,990 miles to spare. This makes it a (relatively) tight fit, and is a remarkable statistic when you consider how large some of the other planets in the solar system are. It also makes you think about the distance between Earth and the other planets in our solar system, and just how vast space is. This statistic also makes you realize what an incredible job we have done in exploring our solar system, but equally how much more there is to discover.

4. There Are More Stars in the Universe Than There Are Grains of Sand on the Earth

The size of the universe is truly mind-boggling and difficult to comprehend. Astronomer Carl Sagan is famous for claiming that there are more stars in the universe than there are grains of sand on the world’s deserts and beaches, but this is, of course, difficult to prove. Many people do not take this as a fact, and instead just see it as a good way of describing how astonishingly big the cosmos is. Scientists went about conducting a study at the Australian National University to see if Sagan’s claims are in fact true, and after some mammoth and mind-melting calculations were made, they discovered that this was in fact the case. This is certainly something to think about next time you are relaxing on a beach somewhere, as it really puts into perspective just how vast and unexplored the entire universe is.

3. There is a Gigantic Body of Water Floating in Space

In 2011, scientists discovered the oldest and largest reservoir of water in existence, and it was found floating through space. The water is equivalent to 140 trillion times all the water in the oceans, and it could provide every single person on Earth a planet’s worth of water 20,000 times over. This is an almost incomprehensible amount of water, and it is particularly odd when outer space is generally considered to be a desolate and dry place. The water was discovered around a gigantic black hole that is in the process of sucking in matter, and spraying out enormous amounts of energy (known as a quasar). Water is created by the waves of energy knocking hydrogen and oxygen atoms together. This was found at a distance of 12 billion light years, meaning that this was occurring in the earliest times of the universe.

2. It Takes Around 230 Million Years For Our Solar System to Orbit the Milky Way

Everyone knows that it takes 24 hours for Earth to rotate on its axis and 365 days to orbit the sun, but we never hear much about a galactic year. This is probably because it is estimated to take a whopping 225 to 250 million years for our solar system to orbit around the center of the Milky Way. To put this into perspective, the Big Bang occurred around 61 galactic years ago, and dinosaurs would have been walking the Earth one galactic year ago. Dinosaurs were then wiped out 0.26 galactic years ago, with modern humans making an appearance “just” 0.001 galactic years ago. Some believe that in one galactic year, all the continents on Earth will have fused into a supercontinent. These breathtaking statistics put into perspective just how long the universe has been around, and are enough to make anyone feel slightly insignificant in the big picture.

1. All the Stars, Galaxies and Planets Only Make Up About 4% of the Universe

It may seem that we know a fair amount about outer space, but it is really just a penny in the ocean. All the stars, galaxies, planets and other matter that can be detected only make up 4%, with the other 96% being what cannot be seen, detected or even understood by astronomers. Twenty-three percent of the mass of the universe is called dark matter, and we know about this because its gravity pulls on visible stars and galaxies. This stuff is baffling enough, but 73% of the mass of the universe is dark energy, and this is something that scientists are stumped by. This has repulsive gravity, and is believed to be the reason that the universe is accelerating in its expansion, instead of expanding at the same rate throughout time or slowing down. This makes it one of the most baffling and mind-melting mysteries out there.

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