Who came up with the rubber sheet analogy?

[Strange]

Not strictly a physics question, more history of science. But this has come up in a few threads where people have mentioned "Einstein's rubber sheet model". I have read little of Einstein's original writing but I didn't think he came up with this analogy.

 

Does anyone know where it originated?

 

[imatfaal]

For some reason I always think of this as the precursor

 

FORD:
Alright imagine this: you get a large round bath made of ebony.

ARTHUR:
Where from? Harrod’s was destroyed by the Vogons.

FORD:
Well it doesn’t matter -

ARTHUR:
So you keep saying!

FORD:
No, No listen. Just imagine that you’ve got this ebony bath, right? And it’s conical.

ARTHUR:
Conical? What kind of bath is -

FORD:
No, no, shh, shhh, it’s, it’s, it’s conical okay? So what you do, you fill it with fine white sand right? Or sugar, or anything like that. And when it’s full, you pull the plug out and it all just twirls down out of the plug hole… but the thing is…

 

 

I understand it is not - but any excuse to read through one of the greatest radio scripts in the history of man

[Strange]

I feel privileged to have been around to hear the original broadcasts. Nothing else has quite lived up to that (not even the repeats!)

[imatfaal]

I feel privileged to have been around to hear the original broadcasts. Nothing else has quite lived up to that (not even the repeats!)

 

I love the books, the TV series, even the film - but the radio broadcasts were exceptional. I caught up with the series at about age 11 via a set of tapes of the broadcasts that I borrowed from local library (and nearly wore out).

 

I met the great man a few times and he was one of those rare heroes who exceed your expectations when you met in person.

[geordief]

From a look around the internet ,I get the feeling that it may have been Einstein -or at least a few people attribute it to him.

 

It doesn't come up in his quotations ,not surprisingly but I have found an academic who says that is how Einstein pictured it so perhaps it could have been his idea,

 

As an aside is there a way of measuring the extent of spacetime and the amount of mass-energy in the same units (similarly to how time and space do when c is introduced as a conversion factor)?

 

 

 

I used to listen to those broadcasts too (great music-it was the same wasn't it?)-a long time ago now.(viva the BBC)

[Strange]

I met the great man a few times and he was one of those rare heroes who exceed your expectations when you met in person.

 

Wow.

From a look around the internet ,I get the feeling that it may have been Einstein -or at least a few people attribute it to him.

 

It doesn't come up in his quotations ,not surprisingly but I have found an academic who says that is how Einstein pictured it so perhaps it could have been his idea,

 

Ah, thanks. I couldn't find anything. Do you still have a link to that last one?

 

 

As an aside is there a way of measuring the extent of spacetime and the amount of mass-energy in the same units (similarly to how time and space do when c is introduced as a conversion factor)?

 

'Fraid I can't answer that. (I assume you mean "extent of space-time curvature"?) I would guess the answer is no, as the curvature cannot be quantified by a simple value and there is a complex mapping from mass-energy to curvature. (Plus there are other factors that affect the amount of curvature, for example pressure.)

[geordief]

 

 

 

Ah, thanks. I couldn't find anything. Do you still have a link to that last one?

 

 

 

I will just give you the reply I was drafting.

 

 

 

jthorusen (post# 32) on this site http://physicsworld.com/cws/article/news/2011/sep/28/galaxy-clusters-back-general-relativity

 

thinks it may have been Einstein but no one follows up on this..

 

I also found this :https://worldhistoryproject.org/1915/albert-einsteins-general-theory-of-relativity-is-published

 

"General Relativity describes gravity as a warping of space itself, not as a force. Einstein pictured space as a three-dimensional version of a thin rubber sheet. If you put a heavy object on the sheet, it makes a dent, and therefore an object's path would be affected by that dent. So, planets orbit the sun because the space around the sun is curved in the 2-D equivalent of a funnel or basin."

 

I have no idea if the author (http://burro.astr.cwru.edu/)was sure of this or just talking vaguely

 

 

 

 

 

'Fraid I can't answer that. (I assume you mean "extent of space-time curvature"?) I would guess the answer is no, as the curvature cannot be quantified by a simple value and there is a complex mapping from mass-energy to curvature. (Plus there are other factors that affect the amount of curvature, for example pressure.)

No , I meant the extent of apace time (mathematically) per se. Similar to the distance between events but something to measure the spacetime enclosure of a subset of events.

 

Like a "volume of spacetime "

Edited October 11, 2016 by geordief

[Strange]

Thanks.

[geordief]

By the way ,is that quote Einstein pictured space as a three-dimensional version of a thin rubber sheet. wrong (as an analogy) ?

 

Should/could it really read (not necessarily accepting that Einstein did picture anything along any rubber sheet line )

 

Einstein pictured space-time as a four -dimensional version of a thin rubber sheet. ?

 

Would that take it from an analogy to a closer description,perhaps a correct one?

Edited October 11, 2016 by geordief

[studiot]

By the way ,is that quote Einstein pictured space as a three-dimensional version of a thin rubber sheet. wrong (as an analogy) ?

 

Should it really read

 

Einstein pictured space-time as a four -dimensional version of a thin rubber sheet. ?

 

Would that take it from an analogy to a closer description,perhaps a correct one?

 

I have never liked the rubber sheet analog as it introduces an inconsistency as well as an explanation/example.

 

IMHO a far better analog is provided by the surveyors' technique of deflection angles, but that should be discussed in a separate thread if you are interested.

 

Oh and I'm sorry , Strange, I do not have the information you request, but it would be interesting to know the answer if you find a definitive one.

Edited October 11, 2016 by studiot

[geordief]

 

I have never liked the rubber sheet analog as it introduces an inconsistency as well as an explanation/example.

 

IMHO a far better analog is provided by the surveyors' technique of deflection angles, but that should be discussed in a separate thread if you are interested.

 

OK .Will do.

[Strange]

By the way ,is that quote Einstein pictured space as a three-dimensional version of a thin rubber sheet. wrong (as an analogy) ?

 

Should/could it really read (not necessarily accepting that Einstein did picture anything along any rubber sheet line )

 

Einstein pictured space-time as a four -dimensional version of a thin rubber sheet. ?

 

I think you are correct. Especially as the force of gravity is mainly determined by the curvature in the time dimension (don't ask me to expand on that!)

 

Similarly, his "2D funnel" phrase sounds wrong, too.

[geordief]

 

I think you are correct. Especially as the force of gravity is mainly determined by the curvature in the time dimension (don't ask me to expand on that!)

 

 

And (at least as a mathematical concept) space-time is not compressed so much as squashed. Time,say is compressed and the spatial dimensions are correspondingly stretched?

 

So the overall "volume" of space time is unchanged?

 

Does that also answer my "volume" question (or at least define the question ) in posts #5 and #7 ? All I need is to relate that "volume" to a measurement for mass-energy (with units that cover both )

 

Can that be done?

[Strange]

 

So the overall "volume" of space time is unchanged?

 

I believe that is true (but I'm not sure).

 

 

Does that also answer my "volume" question (or at least define the question ) in posts #5 and #7 ? All I need is to relate that "volume" to a measurement for mass-energy (with units that cover both )

 

But if the mass-energy can change while the volume, as you suggest, stays the same, how can you relate them? (But I have no idea if what you want to do is practical or not).

[Memammal]

Lol, I recently tried to explain this to my kids (who are in primary school) using the analogy of a firm trampoline with different sized/weight balls being placed on it...

[Strange]

Well, I guess it is time for this:

https://xkcd.com/895/

[michel123456]

And (at least as a mathematical concept) space-time is not compressed so much as squashed. Time,say is compressed and the spatial dimensions are correspondingly stretched?

 

So the overall "volume" of space time is unchanged?

 

Does that also answer my "volume" question (or at least define the question ) in posts #5 and #7 ? All I need is to relate that "volume" to a measurement for mass-energy (with units that cover both )

 

Can that be done?

I am not sure.

What remains unchanged is a ratio, not a volume. Length divided by time remains unchanged. Not length multiplied by time.

My guess is that the volume changes as a scale factor.

[geordief]

We are talking about a 4D volume inside a 4D "parallelogram". I think one of its apexes is at an event in Space-Time (hope I have not put my foot in my mouth yet)

 

Can this 4D volume have anything "inside" it or is it simply a mathematical construct that allows us the calculate the space/time ratio at that point?

 

If I am still "on board" , is this ratio closely connected (mathematically) to the curvature of space-time at that point?

[Endy0816]

Topology is sometimes referred to as 'rubber sheet geometry'. Might have been picked up from there.

[Strange]

Topology is sometimes referred to as 'rubber sheet geometry'. Might have been picked up from there.

 

Good point. The concept could well predate GR.

[Phi for All]

It was this guy, and I had him dealt with.

 

 

You're welcome.