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Quantum Physics and Time Travel
Transcript of Quantum Physics and Time Travel
Although time travel has been a common plot device in fiction since the 19th century, and one-way travel into the future is arguably possible given the phenomenon of time dilation based on velocity in the theory of special relativity (exemplified by the twin paradox), as well as gravitational time dilation in the theory of general relativity, it is currently unknown whether the laws of physics would allow backwards time travel.
Any technological device, whether fictional or hypothetical, that is used to achieve time travel is commonly known as a time machine.
Some interpretations of time travel also suggest that an attempt to travel backwards in time might take one to a parallel universe whose history would begin to diverge from the traveler's original history after the moment the traveler arrived in the past Very Boring wikipedia article. Let's get to the Gist of it - Is it Possible? Well... Yes. Theoretically - at least, for us. And physically, for other things. Other Things being: photons and electrons This'll be Quantum Theory based. . But a little backdrop to Quantum Mechanics will help first. So - back to electrons and photons. Basically. Photon is eaten by Electron.
Electron goes on - and then an entirely new
Photon pops out. So where does this come from? We can actually watch this happening. If you go just slower than the speed of light
which is a good 299 792.458 km per second - 7 revolutions around the earth a second, if it were to be sent around the equator, then relativity means that time is slowed down in relation to you. Say you travelled at 0.99c - c is the speed of light, to Proxima Centauri, a star approximately 4.2 light years away - the closest star after the Sun. It would take you - in relative terms to you travelling, 4.2424... human years.
Got that? Right. Now we get complicated. Right. So, it's 4.242424 years for you. But on earth,it's a lot longer.
The formula for working out the time on earth is ɣ Gamma equals It equals to about 28 years, on Earth. So - it takes the space traveller 4 ish years each way, and 28 years for the people on Earth. suppose a man traveled back in time and killed his biological grandfather before the latter met the traveler's grandmother. As a result, one of the traveler's parents (and by extension the traveler himself) would never have been conceived. This would imply that he could not have traveled back in time after all, which means the grandfather would still be alive, and the traveler would have been conceived allowing him to travel back in time and kill his grandfather. suppose a man traveled back in time and killed his biological grandfather before the latter met the traveler's grandmother. As a result, one of the traveler's parents (and by extension the traveler himself) would never have been conceived. This would imply that he could not have traveled back in time after all, which means the grandfather would still be alive, and the traveler would have been conceived allowing him to travel back in time and kill his grandfather. Time Travel And a bit of Quantum Physics. By Us Well, the current theory is And this isn't anything unnatural.
This isn't a human invention - whilst
a human explanation, it's natural! A phenomena. So - we know it works at
the microscopic level - but
at macroscopic level, is it possible? Yes - but only for going forward. Einstein's theory of special relativity allows this to happen. So - it now comes down
to a decision. Who's doing the time travelling?
Earth, or the space traveller. If it's the space traveller, he's travelling into the future. If the Earth is moving away, Earth is travelling into the past. The general assumption is that it's the traveller that does the time travel. We've worked out how to go forward through
going close to the speed of light. How about other ways? So- what do black holes have to do with time travel? Realistically, not much, because they are so far way, and people would die if they got close to them. But, theoretically, it is possible to use them as a form of time travel. Black holes have huge gravitational force around them, which apparently, according to some Harvard scientists, would affect the speed of a clock tick. This is a picture of a black hole In a very strong gravitational field, if you were to send pulses of light once a second, someone far away would see the interval between the pulses as much more than a second. One second to you falling into a black hole is several minutes to the other person and, in a strange way, you are aging more slowly than the other person and travelling into the future faster than they are. If you could manage to put on the brakes just before crossing over into the black hole boundary, and return to the person who has been watching you this whole time, you could see that your clock reads a much earlier time than his/her clock. To you, only 2000 hours may have elapsed, however, their clock would read perhaps 10000 hours or several weeks later, depending how close to the boundary of the black hole you got before escaping. In space, masses that place pressure on different parts of the universe could come together to form a wormhole, a tunnel through space and time. We could then travel from Earth to another galaxy and back in a much shorter time than if we tried to get there by travelling thorugh the intervening space. Let's say that we wanted to travel to Sirius, a star that's been seen in the Canis Major constellation just below Orion. Sirius is roughly 9 light-years from Earth, which is about 54 trillion miles (90 trillion km). This distance would be far too big for space travellers to get there and return to tell us about what they found. The farthest people have travelled into space is to the moon, which is only about 248,548 miles (about 400,000 km) away from Earth. If we could find a wormhole that connected us to the space around Sirius, then we could cut the time considerably by avoiding the trillions of miles that we would have to cross with traditional space travel. However, these both rely on the fact that backwards time travel is able to take place in the first place, which we have already said is impossible, at least by our understanding of the world. Because of their compelling nature, these sorts of paradoxes have been the inspiration for many works of science-fiction, in the form of books as well as TV shows and films.
Paradoxes: The Grandfather paradox
A man travels back in time and kills his biological grandfather before he has met the traveller's grandmother. As a result, one of the traveller's parents (and therefore the traveller himself) would never have been conceived. This would mean that he could not have travelled back in time after all, which means the grandfather would still be alive, and the traveller would have been conceived allowing him to travel back in time and kill his grandfather. The free-lunch paradox
The free-lunch paradox also arises from backward time travel. Say if you were to travel backwards in time, and give Beethoven a copy of all the piano sonatas that have made him famous. If he then copied them all down before he had even composed them, it would mean their existence would depend on your decision to travel back in time, and Beethoven wouldn't have to do any composing at all.
Paradox Time! So - to sum up. Time travel kind of naturally exists.
Time travel is only theoretically possible at great speeds, and only for going forward - with our current understanding of space-time mechanics.
Time Travel can be a messy business - paradoxes are just hard to get your head around.
Henry should do Quantum Physics
Elliot should do Black hole research
And they both are from the year 5000BC, and have travelled to the future to tell you this.
Research generally done from the internet,
some physics teacher, a calculator and lots
of free time. Thanks for reading this :) Confused? Oh, and give me a bit of time to load.