The Official Cricketweb Science Thread!

[silentstriker]

Happy birthday to the great man. Would've turned 94 today if he were still alive.

Amazon.com: The Feynman Lectures on Physics, boxed set: The New Millennium Edition (9780465023820): Richard P. Feynman, Robert B. Leighton, Matthew Sands: Books

These books are what really got me into physics. Introductory but done very beautifully. I was never much for most of it in high school (couldn't care any less), but in preparing for college I wanted to go through it so I could take the exam for those classes and pass out so I'd never have to take physics again, but it did the opposite and made me just super-curious about everything.

[Teja.]

Surely You're Joking, Mr. Feynman? is such a ridiculously good book. Would've read it 3-4 times and remember many anecdotes in it vividly. Happy Birthday.

[silentstriker]

Yes, absolutely. Great book.

[G.I.Joe]

Out of curiosity, as someone who has nfi, is Neil DeGrasse Tyson a great mind on the lines of Feynman, or is he this popular just because he articulates the scientific viewpoint so well?

[Spark]

The latter. Feynman was a peerless communicator but he was also one of the leading lights behind the path-integral formulation of QM and a big player in the development of quantum field theory (and esp. QED), arguably the pinnacle of scientific achievement.

[silentstriker]

Out of curiosity, as someone who has nfi, is Neil DeGrasse Tyson a great mind on the lines of Feynman, or is he this popular just because he articulates the scientific viewpoint so well?

Neil de Grasse Tyson is closer to Carl Sagan (not a bad thing to be by any means). Feynmann, on the other hand, was one of the best physicists of the 20th century.

[shankar]

Sorry for the late reply.

It's similar to this: before we knew about extra-solar planets, could we ask if there was water on those planets? No. It's just that we lacked the ability to frame it appropriately because we weren't aware of the existence of planets, let alone water on it. Is the question itself meaningless? No. It's merely premature.

What is the difference between this question and a question about Nessie? The difference is that despite not having any direct evidence about the existence of extra-solar planets, there were good theories which predicted that planets would be found outside our solar system. Whereas w.r.t the Loch Ness question, there is no good theory that tells us that its reasonable to expect a Loch ness monster to exist.

So coming to the question at hand, are there any theories available which predict that in the new theory "time before t1" will be a meaningful entity? No.

I think we're arguing semantics here, but I do not think it is at all similar to the unicorn analogy. Did something exist before t1 is a valid, if premature, question. In fact, one of the main purposes of a theory of quantum gravity would be to answer if that question is valid - I would say it's one of the more important questions - to give us an impression of a unified force. So no, the question is not meaningless, it's one of the reasons for trying to find a theory of quantum gravity in the first place.

The right question is not "What happened before t1?" Rather it is" "How to resolve the current anomaly" and "In the new theory what will the status of the entity of time?" i.e. not presuming the shape of the new theory before it is here.

[silentstriker]

So coming to the question at hand, are there any theories available which predict that in the new theory "time before t1" will be a meaningful entity? No.

Yes. Because we disbelieve that there exists a state of infinite density and to show that something else must exist instead of that is one of our purposes in trying to find a theory of quantum gravity. That's a stated goal - to figure out what was going on when all four forces were the same.

The right question is not "What happened before t1?" Rather it is" "How to resolve the current anomaly" and "In the new theory what will the status of the entity of time?" i.e. not presuming the shape of the new theory before it is here.

Semantics.

[shankar]

Let me just put it this way: The question "what happened before t1?" has the same cognitive status as the question "What happened 50 million years before t1?"

[silentstriker]

Well I've put forth my argument and I think we're just talking about semantics but I'll end it with the fact that the very reason we don't call our theory complete is because we can't ask the question what happened before "t1" or for that matter, 50 million "years" before t1. The very fact that you've defined the variable as t1 makes the question of "what the hell was t0" a valid one. Anyway you are free to respond and disagree but I think we're playing with words not with any scientific ideas so I'll leave it here.

[Flem274*]

watching the vid in SS's sig aws.

"90% of you is empty space"

Finally physics gets something right.

Now he's talking about measuring the curvature of the universe by weighing it. Pretty sure whoever came up with that idea was inspired by boobs.

[silentstriker]

Black holes turn up the heat for the Universe

[weldone]

Why Nikola Tesla was the greatest geek who ever lived - The Oatmeal

[shankar]

Well I've put forth my argument and I think we're just talking about semantics but I'll end it with the fact that the very reason we don't call our theory complete is because we can't ask the question what happened before "t1" or for that matter, 50 million "years" before t1. The very fact that you've defined the variable as t1 makes the question of "what the hell was t0" a valid one. Anyway you are free to respond and disagree but I think we're playing with words not with any scientific ideas so I'll leave it here.

When I say t1 what I mean is some (varying) time-interval T before the present not t1 after the big bang.

The problem lies in talking of the Big bang as an actual event that took place and the planck epoch as an actual period of time that elapsed. Under general relativity alone, these would be true. But as you know, with the quantum effects, this is no longer the case. So the big bang is not an actual event which actually took place but a prediction made by GR that is no longer valid. The time at which the big bang happens in GR is now a sort of pseudo-origin. A new theory might resolve the conflict leaving the predictions of GR untouched. But there is no reason (that I know of, I could be mistaken) to expect this to happen however. For example a new theory might make time itself meaningless beyond a certain time in the past. Or time might extend back to a far greater period of time than t1. There is no reason to privilege one of these with respect to the others.

[silentstriker]

Baby galaxies grew up quickly