Cara Santa Maria, science correspondent for the Huffington Post, does a series of videos there called Talk Nerdy To Me. See Martin Savage on physics and the simulation argument, Mark Jackson on cosmology and string theory, Mark’s PhD advisor Brian Greene on the multiverse, or a collection of interviews about Alan Turing.

The latest one features me talking about the arrow of time. Likely nothing you haven’t heard before, but it’s only five minutes! Could be a useful explainer for your friends who don’t understand why you keep mumbling about entropy under your breath. (People do that, right?)

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### 9 Responses to Talking Nerdy About Time

1. Peter Johnson says:

“Time flies like an arrow; fruit flies like a banana.”

“Time flies when you’re having fun, but to a frog, time’s fun when you’re having flies.”

Entropy is Time. We feel entropy as time in our brain which give a direction towards our experience. Durgadas Datta published a paper on Entropy and TIME which gives an energy gradient quantum jumps to higher entropy on Planks time.

3. I apologize for this unrelated question, but I was always curious about the dot after Boltzmann constant k in the equation for entropy engraved on Boltzmann’s tombstone — the very formula that is displayed on top of this blog. Why dot after k? Was it the way Boltzmann himself wrote his equation for entropy?

4. Chris says:

You said that in the time it takes for the Earth to go around the sun once is the same as it takes for the Earth to spin on its axis 365.25 times. Shouldn’t that be 364.25 times? Since it takes the Earth 23 hours and 56 minutes to spin on its axis once?

5. Sean Carroll says:

Chris– I suppose I could wriggle out by saying “it depends on what you’re measuring the orientation with respect to.” But the real problem is that if I said “364.35 times” most people would be baffled. Maybe I should just stop using that example. Or go with “the Sun rises and sets 365.25 times.”

6. Sean Carroll says:

Konstantin– No idea why there is a period. I don’t think it’s Boltzmann’s fault; I’m not even sure that he ever wrote his own equation this way. (I’ve heard it, and the tombstone design, attributed to Planck.)

7. Gizelle Janine says:

Peter: Good one. 😀

8. Doug Parrish says:

I am going to say something crazy, but I feel it needs to be said. I suspect the false vacuum, (a non zero enegry density at ever Planck area) is the catalyst to which we percieve as time. Thomas Gold, in his 1958 paper, put forward the idea entropy and time are related to the expansion of the universe. This idea has been probed a number of times since. The orginal idea was barried in the concept of Steady State, which included the C-Field. I don’t wish to resurrect Steady State Cosmology, however, I do wish to preserve the posisbility the expansion of the universe is realated to preceived time.
Since the maximum and minimum of a qubit (a quantum energy bit) is .26 kT ln 2, and the fundamental unit of space is a Planck Area, I am going to assume this is the false vacuum. Why this should be the false vacuum, I would like to address at the end. Since Conservation of Information is a result of the Conservation of Energy, linked by the above formula above, and there is no emperical evidence neither of these laws have been violated, I am concluding all energy, and subsequently information is pushed/pulled through time. This invokes a paradox. For example, any object, (ordinary matter) has a “Worldline” (both the past and future). Yet the Wordline is unavailable to the stationary observer. The wordline does exist, and Einstein’s Field Equations predicts there existence. However, it’s not until an observer expends energy (to move realitive to his/her refernce frame) does part of the wordline become visible. Keep in mind the observer may only observe one Planck Second at a time, no matter their realitive velocity. So, how do we reconsile the Conservation of Information, and the opaque nature of space-time worldlines? The information/wordline presist, but space has a function which blocks the information. We only observe one Planck Second at a time from the past. It’s as if each Planck Area is duplicating, and the information/energy are transfered to the new Planck Area. It’s a crazy idea, I know, but I cannot see another way around this paradox.

9. Andy Ralphs says:

I have just heard a selection of the RI talk about your recent book and I think you stated that everything is in fact made up of fields and we just “see” them as “particles” – if this is so, then is it possible that physical objects exist as some form of interference “pattern”?