1158: Rubber Sheet

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Rubber Sheet
It IS about physics. It ALL is.
Title text: It IS about physics. It ALL is.


This comic refers to a common analogy used to explain how mass distorts space-time — a bowling ball resting on a sheet of rubber distorts the sheet due to its weight. The system has some qualitative features in common with gravity; it's often misused to show that "mass warps spacetime" (895: Teaching Physics).

The next part of the original analogy explains a black hole: the slope of the sheet becomes so deep that you can't climb out from the bottom any more, similar to a black hole, which even light can't escape from. However, the comic subverts the analogy, and the sheet becomes a trampoline instead.

Reading onwards, it seems that Beret Guy is just messing about with the scenario.

The line "Imagining is fun!" is also a homage to Richard P. Feynman's "Fun to Imagine" Series of Interviews. The power of Beret Guy's imagination—so that he can physically experience what he imagines—is reminiscent of 248: Hypotheticals.

The title text also states that the rubber sheet, broken rope and trampoline are still all about physics (see also 435: Purity).


[Beret guy is standing on a giant bowling ball on a rubber sheet. Megan is watching.]
Beret Guy: Imagine a giant bowling ball on a rubber sheet.
Beret Guy: The ball's weight makes a dent in the sheet.
[A rope is pulling the ball down into the sheet.]
Beret Guy: Now imagine a rope that pulls the ball down even further.
Beret Guy: ...Annnnd...
[Rope lets go. Ball is catapulted with Beret Guy on it.]
Beret Guy: Wheee
[Beret guy and ball are falling back down.]
Megan: ...Oh. I thought this was about physics.
Beret Guy: Imagining is fun!

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There is no rope in black hole analogy. On the other hand ... maybe one day this becomes common analogy for explaining some method of FTL travel ... -- Hkmaly (talk) 08:52, 9 January 2013 (UTC)

It is no rope - it is a rubber sheet seen from the side. Sebastian -- 14:01, 9 January 2013 (UTC)sorry, you meant the rope there ;-) Sebastian -- 20:18, 9 January 2013 (UTC)

Did you see the harmonics of the wave? I think there are four different ones in the third frame. Sebastian -- 14:01, 9 January 2013 (UTC)

- Two harmonics, two different phases of each. 15:56, 9 January 2013 (UTC)

- Realistically, the forms of the rubber sheet in panels 1-3 and possibly the last are significant. The first and second panels are probably illustrating something interesting related to Catenary curves and behaviour when external force is applied, the 3rd references wave reinforcement, the heavy ball is correctly moving straight up and down as expected under Newton's laws. I don't know if the orientation of the bowling ball, hight relative to how far down it is pulled or the vibrations have formal significance, but a physicist would be wise not to neglect them if they wanted to model the situation properly. The comic overall is clearly showing how a large number of well known effects can occur in a simple thought experiment. The tag line isn't joking when it says there is a lot of physics going on, those shapes aren't being chosen arbitrarily to look good. They are accurate illustrations of the situation being described. A look into the details of what a physicist might imagine, if you will. (talk) (please sign your comments with ~~~~)

It seems to me there should be a cross-reference to 895: Teaching Physics (and if I knew more about the conventions of this wiki I would be bold and add it myself... but I don't, so I won't.) -- 17:35, 9 January 2013 (UTC)

Furthermore, you could see the "BOOOIING" in this comic as an alternative to the "Boooooring" (only one-letter difference) at the end of 895: Teaching Physics : Instead of becoming boring after "...Annnnd..." cliffhanger, the demonstration becomes really fun. Anyone to add that point in the explanation if relevant ? --KoundelitchNico (talk) 09:36, 24 September 2014 (UTC)

I made a playlist of the mentioned "Fun to Imagine" series of videos:


Deelkar (talk) 03:16, 10 January 2013 (UTC)

Well I made a rebuttal of Einsdynamics: Gravity first, luser! I used Google News BEFORE it was clickbait (talk) 18:57, 13 January 2015 (UTC)

Here's a video of a bowling ball being dropped on a trampoline from a height of 165 m (500 ft) https://youtu.be/-6h65t2MOfU?t=623 -- The Cat Lady (talk) 15:39, 22 September 2021 (UTC)