Hindsight, as they say, is 20/20, but sometimes it would be nice to have known the outcomes before making a choice. This is as true in day-to-day life as it is in quantum mechanics. But it seems that the quantum world has something we do not have: a way to alter yesterday’s choices today, before they become tomorrow’s mistakes.
None of this is real time-travel. Physicists remain skeptical about that possibility. However, it is possible to simulate a closed time-loop with quantum mechanics, thanks to the property of entanglement. When two particles are entangled, they are in a single state even if they are separated by huge distances. A change to one is a change to the other, and this happens instantaneously.
So a particle can be prepared for an experiment, entangled, and sent to the experiment. Then scientists can modify its entangled companion, changing the way the particle in the experiment behaves.
For most of us, the passage of time flies in just one inexorable direction.
But for theoretical quantum physicists, time’s direction isn’t quite so inflexible. It’s possible to theoretically model, simulate, and observe the backwards flow of time in ways that are impossible to achieve in the real world.
And now, scientists have shown that simulations of backwards time travel can help solve physics problems that cannot be resolved with normal physics.
Scientists trying to take advantage of the unusual properties of the quantum realm say they have successfully simulated a method of backward time travel that allowed them to change an event after the fact one out of four times. The Cambridge University team is quick to caution that they have built a time machine, per se, but also note how their process doesn’t violate physics while changing past events after they have happened.
“Imagine that you want to send a gift to someone: you need to send it on day one to make sure it arrives on day three,” explained lead author David Arvidsson-Shukur from the Cambridge Hitachi Laboratory. “However, you only receive that person’s wish list on day two.”
To respect the gift recipient’s timeline, you would need to send it on day one. But, as Arvidsson-Shukur notes, you won’t know what gift to send until later, meaning your gift will either be late or be wrong.
Physicists have shown that simulating models of hypothetical time travel can solve experimental problems that appear impossible to solve using standard physics.
“Lightning” system connects photons to the electronic components of computers using a novel abstraction, creating the first photonic computing prototype to serve real-time machine-learning inference requests.
Computing is at an inflection point. Moore’s Law, which predicts that the number of transistors on an electronic chip will double each year, is slowing down due to the physical limits of fitting more transistors on affordable microchips. These increases in computer power are slowing down as the demand grows for high-performance computers that can support increasingly complex artificial intelligence models. This inconvenience has led engineers to explore new methods for expanding the computational capabilities of their machines, but a solution remains unclear.
Is time travel possible, and if it is, what sort of civilizations would result? We’ll explore the science that might permit it as well as the classic science fiction examples to see if they make sense.
What happened before the Big Bang? In two of our previous films we examined cyclic cosmologies and time travel universe models. Specially, the Gott and Li Model https://www.youtube.com/watch?v=79LciHWV4Qs) and Penrose’s Conformal Cyclic Cosmology https://www.youtube.com/watch?v=FVDJJVoTx7s). Recently Beth Gould and Niayesh Afshordi of the Perimeter Institute for Theoretical Physics have fused these two models together to create a startling new vision of the universe. In this film they explain their new proposal, known as Periodic Time Cosmology.
0:00 Introduction. 0:45 NIayesh’s story. 1:15 Beth’s story. 2:25 relativity. 3:26 Gott & Li model. 6:23 origins of the PTC model. 8:17 PTC periodic time cosmology. 10:55 Penrose cyclic model. 13:01 Sir Roger Penrose. 14:19 CCC and PTC 15:45 conformal rescaling and the CMB 17:28 assumptions. 18:41 why a time loop? 20:11 empirical test. 23:96 predcitions. 26:19 inflation vs PTC 30:22 gravitational waves. 31:40 cycles and the 2nd law. 32:54 paradoxes. 34:08 causality. 35:17 immortality in a cyclic universe. 38:02 eternal return. 39:21 quantum gravity. 39:57 conclusion.
Elizabeth Gould has asked to make this clarification in the written text ” “Despite the availability of infinite time in the periodic time model, this doesn’t lead to thermalization in a typical time-evolution scenario, and therefore doesn’t, strictly speaking, solve the problem related to thermalization in the power spectrum. The reason for this is that, unlike bounce models with a net expansion each cycle, our model has an effective contraction during the conformal phases. Periodic time, therefore, has a unique character in which it reuses the power spectrum from the previous cycles, which is confined to a given form due to the constraints of the system, rather than removing the old power spectrum and needing to produce a new one.”
Whether you find yourself laying awake at night crippled with anxiety regarding the embarrassing errors of your past, or just love Christopher Nolan’s non-linear storytelling, you may be shocked to learn about the latest scientific discovery. According to a recent write-up from Science Alert, time travel may actually be achievable, using the powerful time dilation of interstellar wormholes.
