“Time really exists”: Highlights from our live-chat with Sean Carroll

Posted by: Ben Lillie

Sean Carroll took a two hour break from his vacation to chat on TED Conversations about his talk on the nature of time and other questions about time, the cosmos, and poker. Thanks to everyone who came by with questions, and to Sean for exciting answers about an enormous topic. As proof that we was in Vegas, and that he’s good at poker, he sent a photo of the token he received for winning a tournament:

Here are some other highlights:


Sean Carroll: Our brains did not evolve to study physics or cosmology; yet, we’re doing a very good job.


Sean Carroll: Interestingly, it’s very possible for two universes to bump into each other without creating much fuss. That’s because chances are that one universe is much, much bigger than the other one; the colliding universe would just show up as a hot spot in the bigger universe, which would eventually come to equilibrium with all the stuff around it. Cosmologists are actively looking for signs of such universes in the cosmic microwave background.


Nafissa Yakubova: How does this knowledge about Universe and Time affect your everyday life? ( beyond your work)

As a space and time enthusiast, my layman knowledge about universe has a huge impact on how my mind works and how I live my daily life. I’m curious about how it’s for YOU as a pro physicist and cosmologist: could you please share how it affects your thinking, views and daily life?

Sean Carroll: I think it affects my everyday life quite a bit. When you fly to a physics conference, and you’re in the airport waiting to board, it’s usually not hard to pick out the other physicists. But I try to blend in to some extent.

Physics helps you think quantitatively about the world, understand hypothesis-testing, and get some feeling for the uncertain values of real-world measurements. All very useful skills!


Andrew Cross: Sean, you stated that: “…empty space essentially lasts forever (but) since empty space gives off radiation there’s actually thermal fluctuations and it cycles around all the different possible combinations of the degrees of freedom that exists in empty space.”

Does this make life possible in the empty space era?

Sean Carroll: Yes, absolutely, at least in principle. Indeed, that’s the big question: if a model like this is right, why aren’t we random fluctuations in an otherwise empty space, rather than finding ourselves in a warm and inviting universe filled with stars and galaxies?


Piotr Bulczak: Does that all mean that there is actually nothing like time? Is it just a our “feeling” of the changes around, states changes, fluctuations? Without any change around us would we be in present time time? Ok, just said there is no time in fact. :-)

Sean Carroll: I’m someone who believe that time really exists. Otherwise how would we know when to participate in the TED chat?

Comments (4)

  • Dale Stocker commented on Aug 29 2012

    I first point out that time as we perceive it is based on our brains. What this means is that it is restrained to the neurological structure. This has its basic functions within the electro chemical actions that take place within it. It is in a constant state of chemical activity, and this activity takes time to happen. Along with this is the capability for of memory. Without this, the continuity of time would not happen. Consider this, how long did it take you to read the last sentence? If there was not a memory, as you read the first word, it would then be within that time it took, but as you read the next word, the first one is gone. It is only that we can remember what had come before that we can string together a sentence, and with this the information. If you had no memory of all your yesterdays, then time would not be the same. In this it would also be unlikely that you could assume there would be a tomorrow. You would simply be in the moment. Even within that moment however our brains take time to process.
    So time in itself does not exist as we may think of it. Here come the idea that time is almost like a thing or property of the universe. In this we think of things in terms of Space-Time and the relation that was shown my Einstein. However, if we can get away from thinking of time as a constant thing, or property of the universe then was is it? If it does not exist is it some metaphysical, other dimensional thing? In this I consider one of the properties and definitions that I have for what is metaphysical and what is physical. That is “If it can be measured, it is physical, if it cannot be measured, it is metaphysical.” By my own definition then I have to concede that time is physical because it can be measured. It however, is not a constant as shown by the theory of relativity. So what is it, again not thinking of time as a thing or “IT.”
    Time is a measurement of the rate at which something changes. In order for there to be any time, there must be change. Within this universe that is always happening. Every atom is in a constant state of motion, from that of a gas to just the vibration and electron movement. Nothing in this universe stands still. I will get to black hole theory later.
    Within the theory of relativity time seems to change in a calculable way. Again what are we really measuring? A rate of change. What this theory has shown by experimentation is that the perceived time does in fact change at a predictable rate. However, this experimentation is still limited to what we are able to do in experimentation. We are so far limited in the source of gravity as that of the Earth. Also the speeds we can reach are nowhere close to the speed of light in a way we can measure time. Still the effects seem to support the theory and this is a good indication.
    I will also interject a bit of my own theory here in saying I think that it is movement of space, and not gravity itself that creates the time change. I will try to explain this with a colorful metaphor.
    Let’s imagine time as each single moment in a quantum way. So for this metaphor each moment of time can be represented as a ball. It may be interesting to break up time in this way, so a moment is a definite quantity, but hard in that physical reality does not seem to have a quantum of time. Still for this metaphor we can use this. Not how to make time pass? Let’s say that father time has to pick up one of these balls and put it through a hole at a certain level, and this will represent the passing of that moment of time. So this is the picture, see father time standing on infinite balls. He reaches down and picks one up, then lifts it to the height of the hole and puts it in. Then repeating the process. Father time never gets tired and the balls are the same. The speed he picks up and places the balls is the rate that times seems to pass. For those of you that would like a bit more quantum or scientific view to our little story; make the speed that of light and the distance that of plank length. Here you could really say that a moment is such and such or as calculated as plank time. At the end of this I will also add a theory about the changing of the speed of light, but for now let’s keep it as a constant.
    Now that we have our image, watch as time does his work. We put time in space at our rate of speed. Here he can pick up the time balls and put them into the hole very fast, there being little to no resistance. If he was in a place where he was not in any motion he would be doing this as fast as it could be done. We are however moving through space, so they the theory of relativity if is not that fast. Why is this? And if this is the case, is there some vector of space and speed were a absolute none movement can be found. Well, if we take it that we are moving away from the origin of the universe, the big bang, than a vector and speed in that direction may be measurable. Here I am not sure we can find this out, but it’s an idea. Back to our father time as he lifts time balls. His speed is limited to the speed of light. So, not we speed him up in space, say to close to the speed of light. Depending on his vector he would either be moving slower, or at his fastest speed. What I mean by this is let’s place the direction of his speed in the same direction of how he is lifting the balls. Now when he picks one up and moves it to the hold it would take longer because the speed he moves the balls is always the speed of light. But if half of that speed is already taken from his motion it would take about twice as long to get the time ball to the hole. Hence, it would appear that time was slowed down. If we however place the vector in the other direction, there would be no slowing but time at its fastest speed, but no faster than the speed of light. So if we place the direction our father time is lifting these time balls to be all directions then we have to take all the computations together to get a really feel for how time is passing.
    In the above imaginary work maybe we can use something a bit more scientific. For this let’s just use an atom. Our atom has electrons that are buzzing around it, or for this model we will at least think of it that way. The cloud and standing wave of the electron may best represent the true nature of it, but it’s easier to look at the electron as a moving particle for this experiment. So, as the electron moves around the atom, we will assume at the speed of light, it is going in all directions at some point. Here we can compare it to the time balls, in that at some point it is moving with the vector of speed and at some point away, and all else in-between. As in the time balls case when it is moving with the vector it cannot pass the speed of light. This may give some explanation for times apparent change as something gets closer to the speed of light.
    Now let’s bring father time down to Earth, or some other gravity source. Here again the direction of father time comes into play. We will start him out standing upright so he reaches down and picks up a time ball. Now to put this time ball into the hold he is moving through space and the speed of light. But the gravity is moving space down at some speed as well. So in a large gravity field, I will use something big enough to show the effects, say that would cause space at whatever point father time was to move passed him at half the speed of light. This would be identical to the situation we have above were father time was moving at half the speed of light. We can also apply this to all the directions of the vectors. However, it is the speed of space passing father time that makes this effect, not gravity. The gravity is just the movement of space. For this to work father time must not be falling and here is where my theory may vary from that of contemporaries. With this model, if we let father time fall with the rest of space, time would act as if it was not within the gravity.
    Is there any way to test my theory? I am thinking of a centrifuge. Though this has its limits and may not be the best way. Let’s put father time in the centrifuge and crank it up till it has high relative gravity based on inertia but the speed in not that high. If it was inertia that causes time to slow, because father time has a harder time lifting the time balls to the hole, we should see time change based on that. I do not at this time know of any experiments done were the change of time is measured in a centrifuge and there for cannot say. If someone has done this experiment I would like to know what the results are as this can show us a better picture of what time really is. The other way of seeing if my theory has some merit is a lot trickier. It would require some very precise time measurement. Let’s take 3 time pieces. One we place high up, like on top of a mountain. Another we place low, at sea level. Yes this has been done to see the variation of time for the relativity theory, and yes it worked out. But by my theory, it’s the movement of space, not gravity. At the higher clock space would still be loss and moving a bit slower, very little bit. It’s this very, very little bit that we would have to measure a change in, in a very short time. To test my theory we take the third clock and place it at the height of the mountain clock. Put a good transmitter on it or some way to record the time. Then drop it to the low clock position. With the explanation I have given above the time for this clock would be faster than both the high and low clocks, for as it fell it would be moving with the speed of space that we call gravity. Now more problems of this experiment for the real world. We would have to factor in air resistance unless we could do this in a vacuum. Even with the technology we now have I think something could be done to show results, and until that is done this will just remain my theory.
    In all of this I wanted to show the one thing about time and that is that there is no such thing in an objective form. Time is the rate of action.

    • commented on Aug 30 2012

      A Vida é Feita de Momentos, A Felicidade de Momentos Vividos intensamente. Positividade, nasceres do sol Liberdade e.Dia de luz e positividade.Bom dia!!!

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