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Ask Slashdot: How Would You Explain Einstein's Theories To a Nine-Year-Old?
SiggyRadiation writes: A few days ago, my 9-year-old son asked me why Albert Einstein was so famous. I decided not just to start with the famous formula E=mc^2, because that just seemed to be the easy way out. So I tried to explain what mass and energy are. Then I asked him to try to explain gravity to me. The earth pulls at you because it has a lot of mass. But how can the earth influence your body, pull your feet to the ground, without actually touching you? Why is it that one thing (the earth) can influence something else (you) without actually being connected? Isn't that weird? Einstein figured out how energy, mass and gravity work and are related to each other. This is where our conversation ended.
Afterwards I thought: this might be a nice question to ask on Slashdot; how would I continue this discussion to explain it to him further? Of course, with the goal of further feeding his interest in physics.
Afterwards I thought: this might be a nice question to ask on Slashdot; how would I continue this discussion to explain it to him further? Of course, with the goal of further feeding his interest in physics.
next.
If he's pretty smart, then you might be able to hand him a copy of Einstein's Relativity: The Special and General Theory. This is a layman's-level introduction that avoids the weeds of Riemann geometry and the like. The math will still be above his head (unless your nine-year-old understands college-level algebra), but he should still be able to get the concepts from reading this.
Finding God in a Dog
I wouldn't try to do it directly. Plenty of other people have covered these areas, and on a level that makes it accessible. For time dilation, Carl Sagan's original Cosmos series had an excellent depiction of time dilation and travel approaching the speed of light. IIRC, part of it was based on a "what if" scenario in which c was something you could approach by peddling a bicycle really hard. When you returned from the ride, all your friends were grey-haired old people.
I'm sure there is some other good programming out there.
For all intensive purposes, "whom" is no longer a word. That begs the question, "who cares"?
"Everything should be made as simple as possible, but not simpler." -- Albert Einstein
By your own account, your son is not asking you about relativity: he is asking why Einstein is so famous (and he is 9 year old).
The proper answer is, then, because he ranked to the top of his field, just like (put here whatever TV competition he is fan of, Disney young singers or whatever). When you get to the top of your field, you get famous. Full stop.
Now, if you really want to introduce him into Einstein's, I can tell how I introduced myself, but I was eleven or twelve back then, which I think makes the situation a world apart.
I happened to start thinking about the relativity principle, the original one, Galileo's (no memory of how I stumbled onto it, though) and felt fascinated by the old man in his ship, trying to decide from within his cabin if the ship was moving or not. From there I moved to the "known fact" that nothing, and I mean NOTHING, can go faster than light in a vacuum (you can disgress a bit here talking about Mach's aether and Michelson-Morley experiment if you want to), and how would the world look like if that were true (I probably had read some of the old mental experiments about trains and watches coming and going, but I've forgotten when or where, probably because all this became obscured on my memory by my read, years later, of both Russell's 'ABC of Relativity' and Einstein's 'The meaning of Relativity' -*you* should read them and you would probably wouldn't be asking this question.
Once I got satisfied about special, I moved to the general starting also on"known" facts (taken by me as granted, back then): energy and mass are somehow equivalent (E=m*c^2) and gravity and acceleration look very much the same but can they in fact be set appart? (hint: gravitity looks "spherical" from the perspective of an observer under a heavy field). Oh, another interesting fact: there can also be black holes under newtonian physics, as long as C stands constant and nothing can run faster than light (in a vacuum -oh! and why does light runs faster in a vacuum than through transparent matter? does something can go faster than light -on said matter? Mr Cerenkov left a message).
The fact is, that though you cannot *demonstrate* Einstein's Special or General theories of Relativity without advanced maths (you can't demonstrate Newton's either), you can *exhibit* them on a credible manner, specially the special one (pun intended), on a two dimensional field, just using basic geometry, so a child can have a grasp of them.
"If you can't explain it simply, you don't understand it well enough.""
-- Albert Einstein