I gave a tech talk at Google headquarters on the arrow of time, which was a lot of fun. Must be what all of Silicon Valley was like back in the boom days — pool tables, free food, volleyball, and lots of smart people everywhere. Rather than a lecture hall, the talks are held in a big lobby space where people are regularly walking through, so that passers-by can become intrigued and start listening. Also, it became clear during the questions that at least one Google employee is concerned about how to preserve intelligent life past the 10100 year mark when our universe will be nothing but empty space. Glad they’re thinking long-term!
Here is the talk, which is basically at a popular level, although I felt empowered to use the word “logarithm” without explanation. I’ve also tried to collect other talks by me onto one page, for those who just can’t get enough. (Hi, Mom!)
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Stream-of-conscientious writ accelerated.
Give your audience an occasional break to cogitate; breath once in a while.
my first thought was “why is sean carroll blogging about instant messaging?”
Awesome talk!
I read up on the arrow of time, and it’s very cool stuff…
One possible way to think about it is perhaps to say that at the macroscopic level, causality only works in the direction of increasing entropy. When you drop an object, you know what will happen, at the macroscopic level: the object will hit the ground, make a sound, and slightly heat up the ground.
But in the opposite direction of time, the event is unpredicable. By a macroscopic observation of the world, it is impossible to say that the object is about to jump up. And, in the time direction towards low entropy, such events are common.
Evolution of life can only happen in the direction in which macroscopic causality is well-behaved. Similarly, a conscious being can only make sense of the world in the well-behaved direction of time.
That’s how I’d try to explain it… does that sound reasonable?
Hey Sean- looks like a good talk, which is cool — but i feel compelled at this moment to make an unrelated comment here on an issue which is pretty critical, and if you feel this takes the thread too awry, you can go ahead and freely delete this, i’ll save it and post at DailyKos or other places where it’s being directly discussed.
But: how do you feel about Google’s recent stand on Net Neutrality, and their clear efforts in collaboration with Verizon to undermine it? For all the other issues that have come up with Google before, i’ve given them a pass, and/or understood their position — but this one matters a *hell* of a lot, and i can’t do that, not when their core motto is “Don’t be evil”. I mean, i use many of their products, and so far continue to, but if they keep going like this, my faith in their ‘goodness’ as a company (and i have that for very, very few megacompanies, btw) is going to be undermined, sadly.
Did you have any concerns about this when you spoke, or talk with any employees about these issues?
thx–
M
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Very good talk, for a lay person like me. Explained where time comes from which was/is always a question I think of. Thanks Sean!
Just curious, but if the universe evaporates away into nothingness…will we be starting with low entropy again? what was space before there was a space-time fabric? In other words, what did the infinately massive, infinitely hot, infinitely compressed plasma entity exist in (what was “space” at the time of the big bang)?
Mandeep– I don’t know enough about the net neutrality issue to have a strong opinion.
Tbird49er– The idea is that “empty space” actually has a very high entropy. The density of entropy is low, but not the total entropy.
Sean, I missed your talk at JPL the other day unfortunately — how did that go? Hope it was a good crowd.
Great crowd for the JPL talk. Unfortunately the regular auditorium is being renovated, so they had it at a new auditorium in the middle of JPL, which meant that foreign nationals weren’t allowed in without a pass — a few were turned away at the door.
🙂 That reminds me of a time when James Randi gave a talk for NASA’s JPL and felt the need to explain scientific notation.
Clyde Tombaugh & I shook hands in ’81 at JPL during the Voyager II @ Saturn encounter.
Not likely to have meant very much to him.
He was leaving the commissary as I was entering.
I was just a credentialed visitor. He didn’t seem to mind.
“Buzzed” Aldrin I’ve met 3 times. The most spatially adept narcissist evah.
Shared a radio studio for an interview with Apollo 14’s Edgar Mitchell — Quantum holograms: It’s totally improbable that I’m not as smart as I think I am.
Really a 2012 question?
As quantum observers we are constantly performing operations on the universal wave function. Inverse operations on functions are not typically symmetric. Our notion of time is not related to variable t, it is related to the sequence of operations. Reversing the order of operations will not produce the same result. I am glad to know that all the employee’s of google are now misinformed as it will give me a competitive advantage.
Hi Sean:
How might you have answered this simple question at the Google Talk?
Since the gravitational field of the mass on the inner side of a black hole horizon (that’s otherwise unobservable) freely ‘penetrates’ that horizon to influence mass in our observable universe, why can’t a ‘shell’ of matter beyond the cosmic horizon likewise be responsible for the increasing acceleration away from us as galaxies approach that horizon – and which we currently attribute to dark energy?
So Relativity puts its own spin on the variance of how time passes due to the invariance of light speed. Does Relativistic time dilation have an entropy-centric explanation or connection?
One confusion I have is that there seems to be three concepts… 1) that time “is”, 2) that time advances “forward”, and 3) that time advances at a certain rate. Perhaps entropy explains only (2), and Relativity focuses on (3), and they don’t really mix.
Eh… I need to pick up your book.
I would be interested in comments regarding this. How wide is ‘now’ or ‘the present’?
I tried and failed to go backwards and forward in time by one year. So failing in this it seemed maybe it would be easier to reduce the time to just one day. Again failure. Not one to give up the time was reduced to one second. Failure. Perhaps just a minute fraction of a second, a femtosecond then. Nope nothing doing. Finally I have come to the conclusion I am stuck here in the present. But what confounds me is this. If we cannot move out of the present and neither a year or a second forward or backward is doable how wide or thick is our present time. Is is wavelike, similar to a burning fuse where the present can be likened only to the burning area and the unburned and burned areas of the fuse represent the past and the future? The more I think about it the more claustrophobic I become. It seems pretty narrow in here. Suggestions on how to widen out the present would be welcome.