But is time travel in fact possible? Given the popularity of the concept, this is a legitimate question. As a theoretical physicist, I find that there are several possible answers to this question, not all of which are contradictory.
The simplest answer is that time travel cannot be possible because if it was, we would already be doing it. One can argue that it is forbidden by the laws of physics, like the second law of thermodynamics or relativity. There are also technical challenges: it might be possible but would involve vast amounts of energy.
An international group of astronomers led by Benjamin Thomas of The University of Texas at Austin has used observations from the Hobby-Eberly Telescope (HET) at the university’s McDonald Observatory to unlock a puzzling mystery about a stellar explosion discovered several years ago and evolving even now. The results, published in today’s issue of The Astrophysical Journal, will help astronomers better understand the process of how massive stars live and die.
When an exploding star is first detected, astronomers around the world begin to follow it with telescopes as the light it gives off changes rapidly over time. They see the light from a supernova get brighter, eventually peak, and then start to dim. By noting the times of these peaks and valleys in the light’s brightness, called a “light curve,” as well as the characteristic wavelengths of light emitted at different times, they can deduce the physical characteristics of the system.
“I think what’s really cool about this kind of science is that we’re looking at the emission that’s coming from matter that’s been cast off from the progenitor system before it exploded as a supernova,” Thomas said. “And so this makes a sort of time machine.”
“If one made a research grant application to work on time travel it would be dismissed immediately,” writes the physicist Stephen Hawking in his posthumous book Brief Answers to the Big Questions. He was right. But he was also right that asking whether time travel is possible is a “very serious question” that can still be approached scientifically.
Arguing that our current understanding cannot rule it out, Hawking, it seems, was cautiously optimistic. So where does this leave us? We cannot build a time machine today, but could we in the future?
Let’s start with our everyday experience. We take for granted the ability to call our friends and family wherever they are in the world to find out what they are up to right now. But this is something we can never actually know. The signals carrying their voices and images travel incomprehensibly fast, but it still takes a finite time for those signals to reach us.
Have you ever made a mistake that you wish you could undo? Correcting past mistakes is one of the reasons we find the concept of time travel so fascinating. As often portrayed in science fiction, with a time machine, nothing is permanent anymore – you can always go back and change it. But is time travel really possible in our universe, or is it just science fiction?
Our modern understanding of time and causality comes from general relativity. Theoretical physicist Albert Einstein’s theory combines space and time into a single entity – “spacetime” – and provides a remarkably intricate explanation of how they both work, at a level unmatched by any other established theory.
This theory has existed for more than 100 years, and has been experimentally verified to extremely high precision, so physicists are fairly certain it provides an accurate description of the causal structure of our Universe.
We can travel in time, just not like in the movies Earendel was observed using an effect where the fabric of space-time is warped by gravity – a phenomenon predicted by Einstein. This causes light to bend as it passes by objects with large masses, like planets, suns, or even galaxies, allowing us to see around and even behind these objects.
John Abbruzzese, On using the multiverse to avoid the paradoxes of time travel, Analysis, Volume 61, Issue 1, January 2001, Pages 36–38, https://doi.org/10.1093/analys/61.1.36.
►Is faster-than-light (FTL) travel possible? In most discussions of this, we get hung up on the physics of particular ideas, such as wormholes or warp drives. But today, we take a more zoomed out approach that addresses all FTL propulsion — as well as FTL messaging. Because it turns out that they all allow for time travel. Join us today as we explore why this is so and the profound consequences that ensue. Special thanks to Prof Matt.
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::References:: ► Alcubierre, M., 1994, “The warp drive: hyper-fast travel within general relativity”, Classical and Quantum Gravity, 11 L73: https://arxiv.org/abs/gr-qc/0009013 ► Pfenning, M. & Ford, L., 1997, “The unphysical nature of Warp Drive”, Classical and Quantum Gravity, 14, 1743: https://arxiv.org/abs/gr-qc/9702026 ► Finazzi, S., Liberati, S., Barceló, C., 2009, “Semiclassical instability of dynamical warp drives”, Physical Review D., 79, 124017: https://arxiv.org/abs/0904.0141 ► McMonigal, B., Lewis, G., O’Byrne, P., 2012, “Alcubierre warp drive: On the matter of matter”, Physical Review D., 85, 064024: https://arxiv.org/abs/1202.5708 ► Everett, A., 1996, “Warp drive and causality”, Physical Review D, 53, 7365: https://journals.aps.org/prd/abstract/10.1103/PhysRevD.53.
Wormhole vs Black hole? Which one do you prefer? Most importantly which one truly exists?
Why don’t you watch this video and find out because the information will shock you! Today you’ll FINALLY find out if you can in reality TIME TRAVEL!
So spread the video to pass the word.
Wondering what would happen if you fell into a Black hole? How about if the whole universe got sucked into it? Scary but you’ll get the answers in this video as well.
Enough said. Black hole conversations can be pretty dark.
So do like, share and subscribe to our channel Because it’s Interesting!
From the cosmic microwave background to Feynman diagrams — what are the underlying rules that work to create patterns of action, force and consequence that make up our universe? Brian’s new book “Ten Patterns That Explain the Universe” is available now: https://geni.us/clegg. Watch the Q&A: https://youtu.be/RZB95znAGRE
Brian Clegg will explore the phenomena that make up the very fabric of our world by examining ten essential sequenced systems. From diagrams that show the deep relationships between space and time to the quantum behaviours that rule the way that matter and light interact, Brian will show how these patterns provide a unique view of the physical world and its fundamental workings.
Brian Clegg was born in Rochdale, Lancashire, UK, and attended the Manchester Grammar School, then read Natural Sciences (specialising in experimental physics) at Cambridge University. After graduating, he spent a year at Lancaster University where he gained a second MA in Operational Research, a discipline developed during the Second World War to apply mathematics and probability to warfare and since widely applied to business problem solving. Brian now concentrates on writing popular science books, with topics ranging from infinity to ‘how to build a time machine.’ He has also written regular columns, features and reviews for numerous magazines and newspapers, including Nature, BBC Focus, BBC History, Good Housekeeping, The Times, The Observer, Playboy, The Wall Street Journal and Physics World.
This talk was recorded on 28 September 2021.
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