Mindscape Ask Me Anything, Sean Carroll | February 2021

Welcome to the February 2021 Ask Me Anything episode of Mindscape! These are funded by Patreon supporters (who are also the ones asking the questions). This month is in what has been the conventional format, where I just try my best to answer every question. But it's growing a bit unwieldy, so going forward I might just try to pick my favorite questions and answer them in greater detail. We shall see.

#podcast #ideas #science #philosophy #culture

[josephturner]

Out of all the lectures I listen to on youtube, Sean Carroll's voice is most soothing.

[kvandekolk]

I’m listening to your Google talk as this notification came out! Keep up the good work Sean.

[koolguy]

2:45:30 Light reflected off a mirror doesn't involve absorption and re-emission of light. It's a scattering process. Fluorescence involves the absorption and re-emission, and this has no preferential angle.

[PugetSoundFlyer]

Long form answers are so much more satisfying.

[Well_Earned_Siesta]

Can you do an episode on the topic of John Wheeler?

How did one person manage to attract and support so many highly successful grad students? That plus his own contributions has had a combined impact on the field that is truly awesome.

[BrianFedirko]

Your "jump off a building" comment made my day. I tried it out my front door today 31 times. Sure enough, I didn't fly away... even though my mind wanted to. I must admit my mass/acceleration might need more than 20 cm to acquire flight in any of my engineering programs. Thanks for the lift in attitude rather than altitude. You Rock!

[akumar]

I wanted to know your personal opinion on Sir Roger Penrose CCC theory, thank you .

[mattgraves]

I am a computer scientist watching physics because it's interesting, glad to hear a physicist could find my field interesting.

[mattgraves]

Great point also about the difficulty of a venture being a big reason for why it's worth it.
Intellectual endeavor

[derschutz]

I dont know if you read these, but. I think a lot of people would be extremely interested in a podcast with Demis Hassabis. I think he is different from the other ML guests you have had and id be interested to hear his ideas on ML applications to physics, especially since his goal for ML is to better our scientific knowledge. Of course I dont want to make it seem like i am demanding anything, so only if it seems like something you would be interested in. But he is an expert in neuroscience, AI, and he does have experience interacting with scientists/philosophers. I'd love to see you two brilliant minds interact. Thanks for these great podcasts Sean!

[deeptochatterjee]

To give another explanation of why time reversal doesn't reverse the direction of forces:

Acceleration is the second derivative of position with respect to time d²x/dt². If you change to t'=-t, then you can calculate the new acceleration d²x/dt'², and we get two minus signs from the chain rule (once for each time we differentiate by t'). So it cancels, and the acceleration is invariant

[conceptflow]

I personally love the long answers and long podcasts like most people probably do. But the dumb questions are usually entertaining if they are funny and the dumb physics ones really really help people that are trying to learn. Not everybody is a graduate student! I know I have personally learned a ton from questions that many would consider dumb. I'm sure you can parse out the really awful ones unless they're funny. I would say a combination of the top 100 best questions with as long answers as possible would be perfect. Take a few and do them really long and keep the worst ones really short. Thanks for everything!!

[timw]

Simulation theory is gaining momentum in the broader scientific community.Physicist Tom Campbell has a very interesting TOE. I'd like to know Sean's opinion on the subject.

[lsdap]

Professor Carroll,
Thank you for your contribution in popularising all the wonderful concepts modern physics was able to procure.

Using the occasion I'd very much like to hear your thoughts about the nature of spacetime. I have always wondered if spacetime itself could be quantized and whether its proper to ask a question "is spacetime an emergent phenomenon of quantum fields existence? Or is it the other way round?"
Can you suggest any materials which delve into such topic? What are your thoughts on this matter?

In any case - all your work is very much appreciated. Godspeed!

[marvinmauldin]

We are at the center of the universe, because since the universe is not expanding into anything, the entire universe is the center of the universe, the same as saying that every point in the universe is the center. Some things are hard to express without circular logic.

[munderlarkst]

Is time the result of (i.e., emergent due to) motion? Or, does time exist before motion (perhaps 'potential time', akin to potential energy?) which allows motion and change to occur at all in the first place? If all motion (including motion of all subatomic particles, etc.) were to somehow freeze, would that mean time would freeze; and then when things start moving again time exists (results) again? Or, is time related to degrees of freedom (to move or potentially move) in 3 (or more) dimensional space? Or, none of the above?

[baraka]

I love hearing you tackle philosophical themes. Wish I had a fraction of your intellect.

[johnholly]

Sean, I have a good question I’ve never heard addressed.
Does the double slit delayed choice quantum eraser make worlds re-cohere when the quantum information is erased?

[exodia]

I appreciate the hard work and effort you put in to these, Sean, but how you dismissed one of the first questions regarding how long would it take our fastest rocket to pass Voyager I was, well, lame and downright pompous. I mean, you seemed delighted to talk about your Colbert interview…That person could have waited a long time to get the opportunity to ask you that, or worse yet, what if it was a kid and you are his hero? I quickly Googled something and found that NASA has a probe that can travel 393, 044 km/hr. Is that the fastest? Is it technically a rocket? No, but it’s something. Again, thanks for what you do, it’s more than most scientists do, but you could do better in these situations. Cheers.

[lower_case_t]

2hrs 45: If anyone wants a simple but comprehensive answer to this question (why are photons reflected at an angle equal to the angle of entry by a mirror?) - Richard Feynman used exactly this an an example to show how QED can explain the behavior of light in his book QED - the strange theory of light and matter, which he wrote for an interested layman audience. It's the first 10 pages of chapter 2: Photons - Particles of light. There's no way to squeeze the answer into a YouTube comment, I'm afraid.