Space-Time and Gravity


(Andy Wootton) #1

Last night, Jim Al-Khalili gave the clearest explanation of space-time I’ve ever heard, followed by totally destroying my understanding of gravity.

I think I’m up to about 10% understanding of space-time now. I’d love to talk to anyone that gets this stuff better than me. I liked the beetle on a log analogy and I think it’s helped me slightly to understanding something else I read recently. Can space-time be ‘visualised’ or is it an entirely mathematical idea that can only be hinted at, via models with a reduced number of dimensions?

Jim also screwed up a software release so that’s well worth seeing :slight_smile:


(Marc Cooper) #2

Jim is awesome. I catch him on R4 on my way in every week. Often sit in the car park until he’s done. A friend had him as a lecturer at uni. Kinda envious. Though my uni Prof knew Fred Hoyle http://www.telegraph.co.uk/news/obituaries/9221905/Professor-Maxwell-Irvine.html


(Andy Wootton) #3

One of my physics lecturers was Dr. Bore. He got very cross when asked if he was ‘any relation?’. He was the last leader of Birmingham City Council.


(Andy Wootton) #4

I didn’t want to post spoilers in case anyone wants to watch it but: there is a story in it that Einstein’s son asked why he was so famous. He explained relativity in terms of a beetle crawling on a log. The beetle can only look down and thinks it is walking in a straight line. It can only experiences the curvature of the log in terms of gravitational force.

I THINK I’m the beetle… but the log is a manifold https://en.wikipedia.org/wiki/Manifold

I was looking at the Klein bottles in The Science Museum last year. I wish I’d looked harder:

"A mathematician named Klein
Thought the Möbius band was divine.
Said he: "If you glue
The edges of two,
You'll get a weird bottle like mine." - Leo Moser

(Colin Smith) #5

just received an email from pint of science, might be something interesting for you https://pintofscience.co.uk/events/birmingham


(Andy Wootton) #6

Thanks. I’ve just been sharing that with Slack and Facebook but haven’t actually read it yet :slight_smile:


(Gav) #7

Space-time can only be truly visualised by being conscious, experiencing the passing of time and looking at the space before you.


(Andy Wootton) #8

@ukgav I’d argue that is ‘sensing’ rather than visualising. If you were in a sound-insulated, dark floatation tank, how would you sense the passage of time? I think our experience of time is very largely due to observing state-change. When we are busy, time travels faster than when we are bored?


(Andy Wootton) #9

I need to read this properly but it seems to give a good answer to a bad question https://www.quora.com/Why-is-it-difficult-to-explain-physics-to-a-common-person/answer/Paul-Mainwood


(Marc Cooper) #10

I suspect the reasoning is less complex.

Humans have senses that have evolved to fit our environment. As Darwin explained. There’s no reason that a whole lot of physics occurs outside of our sense organs. We already know some, of course, in the electromagnetic spectrum. And, more recently, gravity waves (though I remain a little sceptical on that one).

The likelihood of physics occurring in a domain we haven’t yet accessed is anyone’s guess. But I consider it to be high.

It’s reasonable to conclude that physics will become ever more inaccessible to a layman, because the models will become ever less intuitive.

I hope I live to see the equivalent of Penzias and Wilson in a whole new domain.


(Marc Cooper) #11

Here’s an alternative viewpoint that I hadn’t considered.

Feminist researcher invents ‘intersectional quantum physics’ to fight ‘oppression’ of Newton


(Andy Wootton) #12

I have no opinion on the religious aspects of feminism. I see cultural norms as as software. It’s like “all humans are created equal”; there’s no evidence that it’s real.

I do, however, have a UML diagram on the state vs flow aspects of physics, in an attempt to deal with the same subject rationally :slight_smile: I’ve been trying to shoe-horn data-code equivalence into it but I’m becoming less convinced. Today, I think code and data can be described by ‘the same stuff’ but that doesn’t prove they are the same. “Is the box a client or a server?” can be answered, “Yes”.


(Andy Wootton) #13

My very tiny amount of reading about space-time has helped me disentangle Einstein’s mathematical model (which seems fairly soundly confirmed by later evidence, if we pretend we know what Time is) from the interpretations which others have put on it, which are many, various and unproven. I’m not always sure ‘popular science’ helps us. I think “scientific facts” should come with confidence and disagreement ratings.