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What does time travel reveal about the nature of space and time? What about the laws of physics under extreme conditions?

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Time travel makes great science fiction, but can it really be done? Travel into the future is already a reality, but visiting the past is a much tougher proposition, and may require fantastic resources such as a wormhole in space. Nevertheless, if going back in time is allowed, even in principle, then what about all those paradoxes that make time travel stories so intriguing?

Paul Davies is a physicist, cosmologist and astrobiologist at Arizona State University, where he is Director of the Beyond Center for Fundamental Concepts in Science. He is the author of many books, including “How to Build a Time Machine” and, most recently, “The Eerie Silence: are we alone in the universe?”

Time travel is one of sci-fi’s favorite tools. But is it possible to build a real time machine? Could you travel into the future or the past? Paul Davies joins John Michael Godlier to discuss the possibilities of time travel and how it would work within Einstein’s theory of general relativity.

Paul Davies is a theoretical physicist and regents professor at the department of physics at Arizona State University. He is a cosmologist, astrobiologist and best-selling science author, including the author of How to Build a Time Machine.
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In this video, we’ll sit down in our time machine and go forward a few millenniums into the future, to see where we would be progressing as a civilization.

Chapters:
0:00 Opening.
0:51 The levels of civilization.
2:13 Timelapse of the future.
5:25 Year 2141
6:34 Year 2768
8:43 Conclusion.

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Two different groups have tested a seemingly counter-intuitive property of the quantum world: That it’s possible to put a photon, a particle of light, in a superposition of states going forward and backward in time. This is not time travel and won’t lead to communicating with the past – but it is an intriguing demonstration of how time can be thought to work at a quantum level.

Unless you have a TARDIS or a DeLorean, time only flows in one direction (forward) for us. This annoying little fact that protects us from all sorts of paradoxes is called the arrow of time. It is believed to be related to the concept of entropy (which always increases in an isolated system like the universe) but it doesn’t seem to be as fundamental at the quantum level.

Instead, something that appears to be fundamental is the so-called CPT symmetry (charge, parity, and time reversal symmetry). This holds for all physical phenomena, and if a combination of two of them is violated (such as famously the CP violations) there ought to be a violation in time symmetry as well.

Many modern science fiction movies tend to use the veneer of science fiction as a way to plug potholes or feature elaborate explosions and action. There’s always a time-travel portal to stand in as the deus ex machina, and some advanced robot or alien who only seems interested in killing everyone.

I like those movies as much as the next fella. But some filmmakers do make a sincere effort to imagine other realities and technologies that inspire in the way classic science fiction does. It doesn’t mean the films have to be the on-screen equivalent of reading an MIT paper on quantum entanglement or something, just that they spin a decent yarn inspired by actual science.

The below are a few slightly less commercial selections, instead of obvious choices like Interstellar or 2001 or Chef, that science fiction movie where Jon Favreau dates both Scarlett Johnasson and Sofia Vergara. That’s the future I want.

A time travel enthusiast may just have found a way to create a time machine, but passengers that go inside it face a dark fate. The idea of a time machine was discussed on the Time Travel Facebook page, which boats a healthy 32.5k members. In the social media group, many ideas are discussed surrounding time travel, with many of them being outlandish and instantly dismissed.