How we remember time is vastly different to how we experience it, says neuroscientist Dean Buonomano.
Time is objective—except between your ears, says neuroscientist Dean Buonomano. Each of us intuitively feels what has been written about since at least 1890, in William James' 'The Principles of Psychology': a warping of our internal clock that is inconsistent with the notion of time as a constant force. Here, Buonomano explains our paradoxical experience of time. In the moment, pleasure is fleeting, while pain and boredom seem to last forever. But that's just one way our brain interprets time: prospectively. In the opposite view, retrospective timing, the tables are turned, and the good times are rebuilt to hold much more weight in our memory while that six-hour delay at the airport fades into oblivion. How we remember time is vastly different to how we experience it. Dean Buonomano is the author of Your Brain Is a Time Machine: The Neuroscience and Physics of Time.
The Many Worlds Interpretation is just one of a few multiverse hypotheses—but is there a glaring paradox in this popular idea?
The idea of a multiverse as we conceive of it was first mentioned by Nobel Prize-winning Austrian physicist Erwin Schrödinger in 1952, who warned a lecture hall full of people that this may "seem lunatic", but perhaps his equations did not show mere alternative versions of history, but alternatives all happening simultaneously. For this week's question, Austin wants to know about the multiverses paradox: if every alternate timeline happens, and anything that can happen does—somewhere—then wouldn't there be a universe that could not support the idea of any other universe existing? All multiverse hypothesis are as yet unverified by experiments, so it's all up in the air. But if we ever want to find out, the way to do it is by supporting space exploration, because the more we find out about the cosmos, the closer we get to knowledge about our own origins and the greater our capacity grows for multiverse experimentation. Bill Nye's most recent book is Unstoppable: Harnessing Science to Change the World.
Astrophysicist Neil deGrasse Tyson explains the nature of time and the conundrums of time travel in a recent interview.
Astrophysicist and science educator Neil deGrasse Tyson gave a fascinating interview recently to Jake Roper of Vsauce3, where he talked at length about the nature of time and the possibility of time travel.
Tyson thinks the most dramatic impact on our current understanding of time came from Einstein's discovery of general relativity. Time stopped being a linear, necessarily sequential idea where “we are all participating in the same ticks of the clock,” as Tyson says. With relativity, time became a more fluid concept, dependent on the observer.
Because of relativity, we learned that there is no “absolute time”.
“Time is relative, so time can be stretched, for me relative to you. So, time has multiple, sort of, parallel rates at which it flows, depending on the state of who's making the measurement and the state of who's in motion, and what conditions they are in,” said Tyson (0:53).
Tyson rather thinks of time as a dimension, calling us “prisoners of the present”. What he means is that we don’t have an ability to jump into the past or the future on our individual timelines. But what if we could do just that?
If time travel was feasible, we’d open ourselves up to some potentially mind-bending situations and logic puzzles.
“Suppose you could move around in your timeline with the same flexibility as moving left and right, up and down, forward and backward. If that's the case you can revisit your own timeline. Under those conditions you do not die. You are always dying. You are not born. You're always being born. That's another kind of interesting way to think about time,” explained Tyson (1:34).
Some classic time paradoxes come out of this thinking. They revolve around the changes that can be imagined by suddenly being able to go back and forth in time.
If you jumped into the future, would you then know and remember everything that would have happened to you had you stayed in your original timeline and let events take place naturally?
And if your timeline already exists, could you change your fate by changing aspects of your future, if you managed to travel to it, like in the classic sci-fi movie franchise “Terminator”.
Neil deGrasse Tyson, astrophysicist, 'Cosmos' television show host and Frederick P. Rose Director of the Hayden Planetarium at the American Museum of Natural History speaks August 4, 2014 after a screening of James Cameron's 'Deepsea Challenge 3D' film at the museum in New York. (Photo credit: STAN HONDA/AFP/Getty Images)
Tyson hypothesizes that maybe you could alter your timeline, creating a new one as part of a “very complex, sort of, fractal structure”. And if this was possible, Tyson really doesn’t agree with some of the unnecessarily complicated plot choices of the "Terminator":
“So, what gets me about Terminator is he's got to kill everybody who might be the mother of the future of the person who overthrows the thing… You can go further back [in time] just have one little thing change and everything after that would change.”
In an example of another strange conundrum, Tyson also explores the idea of a particle that is never created nor destroyed and only exists in a time loop, a concept called “the Bootstrap Paradox”. In the time-travel movie “Somewhere in Time”, this “self-created” object was a locket which the lead character received as a gift from an old woman who told him to meet her back in time. He figures out how to go back in time, meets her when she's young and gifts her the same locket that she gave him back in the future. Once he did that, the origin of the object became uncertain and it got trapped in the time loop.
Another potentially big player in time travel - the infamous Butterfly Effect. It's a concept from chaos theory which basically says that small initial causes can create large ripple effects. If you were time traveling, could you too easily change the course of history?
Tyson isn’t so sure that if you, let’s say, go back and kill baby Hitler that you’d really change anything.
“You pivot everything on this one thing and tell me that all of civilization will be different. I'm not buying it. Civilization is more robust than that. And if Hitler were killed as a child, then no, maybe not - the Germans were ripe to have somebody rise up and take control of their psyche. And maybe the circumstances made Hitler - not Hitler making the circumstances,” pointed out Tyson (10:27).
In the end, Tyson doesn’t believe that travel back in time is possible, agreeing on that with Stephen Hawking. He thinks that at some point, physicists will discover a new law that will explain what prevents backwards time travel, adding “we don't know what that law is or why it must exist but everything we can imagine that allows it totally messes everything up.”
While this is still just a hypothetical discussion, Tyson sees definite value in speculating about time travel. On the other hand, he takes comfort in living a “fixed” life in a linear timeline, adding his opinion of free will:
“If it is being a prisoner of the present transitioning from the past to the future, I have the illusion of free will. And I'm happy to live in that illusion in the knowledge that I don’t.” (13:15)
Watch the whole interview here:
Schrodinger's cat is one of the most famous thought experiments of all time, but what does it mean for science, and what happens to the poor cat?
Schrodinger's cat is one of the most famous thought experiments in all of science. It's the source of countless jokes, t-shirts, and pseudo-intellectual conversations. The idea is this: if a cat is put into a box with an elaborate quantum booby trap then when we open the box the trap will either be activated and kill the cat or not be activated at all. Quantum Physics says the cat should be in “superposition" while we are not looking at it, just like the rest of the quantum system. Meaning the cat is both alive and dead at the same time until we look at it! Zombie cat!
Incredible! Except, Schrodinger didn't mean that at all.
Erwin Schrodinger, quantum physicist extraordinaire, devised the thought experiment as a way to show how the Copenhagen Interpretation of quantum mechanics, the mainstream one, must be wrong. Pointing out that we cannot think of a cat as both alive and dead at the same time, but if the interpretation tells us this is the case, then it must be incorrect.
Albert Einstein, who was never completely comfortable with much of quantum mechanics, also agreed, writing to Erwin: “You are the only contemporary physicist, besides Laue, who sees that one cannot get around the assumption of reality, if only one is honest. Most of them simply do not see what sort of risky game they are playing with reality—reality as something independent of what is experimentally established. Their interpretation is, however, refuted most elegantly by your system of radioactive atom + amplifier + charge of gunpowder + cat in a box, in which the psi-function of the system contains both the cat alive and blown to bits. Nobody really doubts that the presence or absence of the cat is something independent of the act of observation."
Schrodinger later tried for a purely wave based understanding of quantum mechanics, but it was never as popular nor successful as the Copenhagen understanding, which is still dominant today. Of course, there are other ways to look at it, here are a few, and what happens to the poor cat in each one. There are many more interpretations than just these, but these are the most popular alternatives.
A happy cat, not in quantum superposition or a box with a trap in it.
MANY WORLDS: The idea of the multiverse is known to many people. In this interpretation, the cat is alive in one universe and dead in another one. The new universe was “created" when the cat is observed, there is no being alive and dead for this cat. This model of the universe is seen in Bioshock Infinite, and Rick and Morty; among other popular works.
OBJECTIVE COLLAPSE: These theories suggest that the system would collapse long before you open the box, either with the passage of enough time or some other simple event. Therefore, the cat is in a definite state of alive or dead long before you look. This does, however, leave open the idea that the cat is both for at least a fraction of a moment, it just doesn't stay that way long.
All this is great in theory, has anybody tried an experiment?
Yes, but not on a cat. Objects that are rather large, for these purposes, have been placed in superposition. These states don't seem to last long, however. We aren't even to the point of having bacteria be in a “cat state" yet. It seems like no experiment has been done, or will be done for some time.
Schrodinger's cat is one of the best known thought experiments in science. One that most people know, but few understand. While it was intended to be a simple critique, it has evolved into a key test for judging how an understanding of quantum mechanics works, and if that interpretation is a viable one. Is the cat alive? Is it dead? Is it both? How can we know? How is this possible? A quote from Richard Feynman comes to mind:
“Do not keep saying to yourself, if you can possibly avoid it, "But how can it be like that?" because you will get "down the drain", into a blind alley from which nobody has yet escaped. Nobody knows how it can be like that."
This is still a subject of great debate, both for physics and philosophy. Perhaps a new interpretation will be proposed which finally lays the cat to rest, or lets it live outside of the box, or both.