Yes, Time Travel Is Possible; Here's How
EXPAND
Time travel's been one of man's wildest fantasies for centuries. It's long been a popular trend in movies and fiction, inspiring everything from Charles Dickens' A Christmas Carol to H.G. Wells'The Time Machine to the Charlton Heston shrine that is The Planet of the Apes. And with the opening of Interstellar today—n0t to spoil anything—we're about to fantasize about it even more.
The most fantastic thing? It's probably possible.
What's almost impossible
Let's start with the bad news. We probably can't travel back in time and watch the Egyptians build the pyramids. In the last century scientists came up with a number of theories that suggested it is indeed plausible to take a leap into the future; going back in time, unfortunately,is much more complicated. But it's not necessarily impossible.
Albert Einstein laid the groundwork for much of the theoretical science that governs most time travel research today. Of course, scientists like Galileo and Poincaré that came before him helped, but Einstein's theories of special and general relativity dramatically changed our understanding of time and space. And it's because of these well-tested theories that we believe time travel is possible.
One option for would be a wormhole, also known as an Einstein-Rosen bridge. Along with physicist Nathan Rosen, Einstein suggested the existence of wormholes in 1935, and although we've yet to discover one, many scientists have contributed their own theories about how wormholes might work. Stephen Hawking and Kip Thorne are probably the most well known. Thorne, a theoretical physicist at CalTech, even helped Christopher Nolan with the science behind Interstellar.
So let's just assume that wormholes do exist. In the late 1980s, Thorne said that a wormholecould be made into a time machine. According to Einstein's theory of general relativity, a wormhole could act like a bridge though space-time by connecting two distant points with a shortcut. Certain types of wormholes, it's theorized, could allow for time travel in either direction, if we could accelerate one mouth of the wormhole to near-light speed and then reverse it back to its original position. Meanwhile, the other mouth would remain stationary. The result would be that the moving mouth would age less slowly than the stationary mouth thanks to the effect of time dilation—more on this in a second.
But there are several major caveats of traveling back in time with this method. Chief among them is the simple fact that we'd need a method for creating wormholes, and once created, the wormhole would only allow us to travel as far back as the point in time when it was created. So we'll definitely never be spectators to Great Pyramids' construction.
The other really serious caveat is that we'd need a way to move one of the mouths of the wormhole nearly the speed of light. In their seminal 1988 paper on wormholes, Thorne and his colleagues assumed that "advanced beings [would] produce this motion by pulling on the right mouth gravitationally or electronically." We can't do that right now, however.
What we can do is travel into the future—but only by a little bit.
What's almost certainly possible
In recent years, we've seen some aspects of Einstein's fanciful theories proven true. The latest and perhaps most exciting theory is the aforementioned effect called time dilation. Though we've based technology on the theory for decades, an experiment finally proved this year that time dilation is absolutely a real phenomenon. It's also a phenomenon that could allow us to travel into the future.
Time dilation basically refers to the idea that time passes more slowly for a moving clock than it does for a stationary clock. The force of gravity also affects the difference in elapsed time. The greater the gravity and the greater the velocity, the greater the difference in time. Black holes,like the one depicted in Interstellar, for instance,would produce a massive amount of time dilation, due to their extreme gravitational pull.
Thanks to the space program, we've actually been dealing with this effect for many years. This is why the clocks on the International Space Station tick just a little bit more slowly than clocks on Earth do. Since the space station is moving so fast and is affected by less gravity, time moves more quickly. It's also why no clock on Earth is perfectly accurate, since the effect of time dilation means that time moves more slowly closer to the planet's surface. Okay, maybe one is almost perfect.
A better example of time dilation at work involves GPS satellites. The GPS chip in your smartphone works because there are 24 satellites circling the globe at all times that triangulate your location based on how long it takes time-stamped information to travel to and from the device.
However, scientists learned when building the system that the atomic clocks on GPS satellites do indeed run a little bit fast, since they're moving 9,000 miles per hour in orbit. To be specific, they lose 8 microseconds a day. That's hardly perceivable, but it's enough to throw off the location data. And so GPS technology makes adjustments to the clocks on board to account for the relativistic effects. The equation used is kind of complicated.
The implications of all this are huge. What if you took this to the extreme? If you jumped in a spaceship that flew super fast, time would pass more quickly for people on Earth. You could do a lap around the galaxy and return to Earth in the future. This is basically what happens inPlanet of the Apes. In effect, Charlton Heston's character is a time traveler.
What's definitely possible (but kind of silly)
The question remains, can we really take it to that extreme? And is it possible to go backwards through time, too?
Once again, we don't really know. Einstein's theories tend to rule out rewinding time, but they're still theories. It's possible some future discovery could prove them wrong. As for the wormhole approach, we won't really know exactly how that works until we try it, and at the moment, we don't really have a feasible method for building a wormhole in space.
Hence, one easy way to find out is simply to search for time travelers walking amongst us. No laboratory required! And that's exactly what several zany scientists have done. (Spoiler: They haven't found any.)
If you're really curious about time travel though, go see Interstellar. The science behind it is sound—if sometimes a bit fantastic—but the movie itself is very fantastic.
Top image: Interstellar promo shot
i'm travelling into the future right now, albeit too slowly - it's not friday yet.
These zany guys?
So are your article headlines always so utterly off base?
Also, Is your scientific speculation always so utterly flawed?
Time travel is still not possible, and it will never be possible. Time itself is nothing but a made up concept by humans. To suggest that its a thing that we can jump around in is foolish. Existence is not something on a track that we can reverse.
Also, Is your scientific speculation always so utterly flawed?
Time travel is still not possible, and it will never be possible. Time itself is nothing but a made up concept by humans. To suggest that its a thing that we can jump around in is foolish. Existence is not something on a track that we can reverse.
This has always been my standing. Time is nothing buy a metric designed to describe how far we've traveled through space. Time is not a thing.
Did you actually read the article, by chance?
The way we measure time is an invention. But the fact that there is a forward progression is not. Your phrasing would also imply that length, volume, mass, and density are also non-existent because humans came up with a way to quantify them.
The article pretty clearly states that there is no known method to go back to ancient civilizations. At best (with the required physics to be correct and the required technology to be available), you could take your "vessel" back in time as far as the creation of the required wormhole. It may all be theory at this point, but I would trust the theories of Einstein, Rosen, Thorne, and Hawking before I would trust the reasoning of Optix3344.
The geocentric model of the universe was once considered to be the only possible means of human existence, and we see how true that turned out to be...
Time travel is possible in the sense that very high velocities or very strong gravity slow the passage of time compared to time here on Earth. So for example, if you accelerate a ship to say 95% the speed of light, on the ship the passage of time still seems the same as here on Earth. Every instrument you could use to check the passage of time including nuclear reactions, or any other natural process that occurs are a particular rate, and your clocks, and your biological sense of time passing would all seem "normal". However, when you returned to Earth, you would find that much more time had passed on Earth than had passed for you. If you (for example) did this for a year, you would have aged a year, an atomic clock on your ship would show a year had passed, etc. But back on Earth, maybe 20 years would have passed. (Didn't do the actual math so I'm not sure it would actually be 20 years...but at 95% the speed of light it would be a significant difference between your aging and the aging of everything / everyone on Earth.)
Time is not something "made up by humans". There are innate features of the universe that happen at known frequencies and rates in particular circumstances. The article already mentions that it's very unlikely we could go back in time with the possible exception of engineering a system that would allow us to go back in time to the point where such a system was created, but even that is only theoretically possible and might not be possible at all.
But traveling into the future at a rate different than normal 1 second per second rate is absolutely doable. Even if we can't ever figure out how to do it by acceleration, we could do it by orbiting close enough to a black hole, then return to Earth.
There are a lot of paradoxes in backward time travel. Theoretically time stops at the Speed of light, and you need infinite energy to achieve that speed, but if you somehow achieved FTL travel you would travel back in time.
It stops, not reverses. You wouldn't travel back in time, but rather stop aging relative to the rest of the universe. So you would, in effect, be going forward, not back.
In FL travel you would still age though, right?
According to Orson Scott Card, at least.
Not at the speed of light. 90% of the speed of light you'd age very slowly compared to the rest of the universe.
But if you were to accelerate everything BUT yourself to the speed of light, time would seem to stop, right? Ponder that we accelerated everything past the speed of light and you might travel back in time!
And because of relativity, if everything moves at the speed of light compared to you, you move at the speed of light compared to them. Thus it follows that if you yourself hit the speed of light you both stop in time and travels to the future.
I'm confused...
I'm not a scientist (not even close as you'll see from the question I'm about to ask), but why do you say you need infinite energy to achieve the speed of light? If light can travel at the speed of light, who's to say other things can't achieve this? Does light have infinite energy?
Silly humans. What makes you so sure that time is linear?
If time is circular, and you could go forward in time far enough, you would end up in the past.
This is similar to the idea of a finite universe, where you travel away from earth and if you go far enough, you arrive back at earth.
If time is circular, and you could go forward in time far enough, you would end up in the past.
This is similar to the idea of a finite universe, where you travel away from earth and if you go far enough, you arrive back at earth.
Light has no mass. You have mass. the faster you travel the more mass you gain the more energy required.
Ah, right. The whole "mass" thing. Forgot about that. I knew it was a dumb question. Haha! Thanks for the reminder!
If satellites lose 8 microseconds a day, aren't the people who have worked on the space station time travelers?
Yes. I am not a physicist, but as I understand it, they are operating very slightly in future than the rest of us, although the difference is so small that it is impossible to perceive, or even measure. The same effect is true of two people, one of whom has been on slightly more plane journeys than the other, though obviously at a smaller scale.
Yes; they have very minorly traveled into the "future" - that is, less time has elapsed for them to reach this particular moment in time than for the rest of us. But time passes (imperceptibly) differently for everyone anyway, because whenever you have a velocity your movement through time changes.
Easiest way I've found to think about it (and I hope this helps someone): every single particle is traveling through 4D (or 10D, or 11D doesn't matter) spacetime at the speed of light. That velocity is divided amongst the various dimensions. The faster you're moving in the spatial dimensions, the slower you are in the time dimension.
The same thing happens between an athlete and a couch potato. The couch potato ages faster, while the athlete remains younger for a bit longer. Right?
No comments:
Post a Comment
Note: Only a member of this blog may post a comment.