Gravity posits that matter has a natural pull towards other matter. But, it’s also so weak that you need something as big as the Earth to hold little things like us down, and even then we can still jump up and down on it.
Is there anything that humanity could feasibly build to demonstrate gravity? For example, could we construct a vacuum chamber that has such a smooth floor that two very large, super high-tolerance spheres would be able to roll themselves across the floor to touch each other, based purely on the force of their mutual attraction? Failing that, is there anything that a young child could understand, that we could demonstrate?
I remember back in grade school my science teacher was talking about gravity, then, when explaining that it was actually a pretty weak force she said “look, the ENTIRE Earth is pulling this paper clip down and I can pull it back up with this little tiny magnet.” There’s a million other ways you could make that same demonstration but she really got her point across. Now, that was a really important teacher to me, but that was one of those statements that really stood out to me.
As for how you can demonstrate it, they always talk about gravity warping space and that never made sense to me (even as a ‘science guy’ that dabbled in a bit of physics). But then I saw a demo on youtube that really sort of cleared it up.
This might be too advanced for a young child (you didn’t say the age), but even then, it’s fun to watch.
FTR, he’s teaching other teachers how to do this demo.
Note also that the experiments have gotten a lot better since Cavendish’s time. The current state of the art is experiments to measure the force of gravity over scales smaller than about a tenth of a millimeter: There were some hypotheses that said that the qualitative behavior of gravity might change at such short scales.
What about measuring g at different latitudes? Sure, the centrifugal force would play into this, but it would constitute a minor term of the equation , and could easily be corrected for.
That video is fun but it doesn’t really demonstrate gravity, it just illustrates it… the way baking soda illustrates a volcano. It’s just a visualization, not the real phenomenon.
First of all, the centrifugal force isn’t a minor term in the variation with latitude, but the direct or indirect cause for all of the variation, and the direct and indirect parts are of comparable size. Second, even accounting for that (which could be done with good surveying), you still wouldn’t get the same information you’d get from the Cavendish experiment: You could learn something about how mass is distributed within the Earth, but not how strong G is, nor how much mass there is in total (only the product of those two numbers).
That doesn’t demonstrate that any two masses are attracted to one another. It only demonstrates that things fall towards the center of the Earth.
I was hoping for something that might be slightly more thrilling than watching paint dry… More importantly, in the video that Ornery Bob linked, it seems like we have to take it on faith that the room is current-free, despite the fact that we can see him moving around doing things and have no idea how he protected the room from air circulation.
For anyone born on the Earth, the fact that things go “down” is just a fact of life, just like the fact that the sky is blue or that the Pope is Catholic. So far as they’re concerned, I could say that the Pope is Catholic because God selected him, because he was born and raised in a Catholic family and climbed the ladder through various means, or that he was put in the position by Devil. So far as the disinterested third party is concerned any of these is just as reasonable as the others, unless I can provide evidence.
Just as I’m saying that things fall to the ground because matter attracts other matter, someone else could be saying that down is down and that’s just natural for things to go down, or that our understanding of pressures is reversed and things that we consider to be light are actually heavy, and outerspace is so dense, it has compacted the lighter elements of the Earth together, pushing us against the surface and only very heavy things, like helium balloons, can sink back towards the sky… Basically, there’s as many possible explanations as the human imagination can come up with. Minus evidence, they’re all just as good as each other.
