Physics

[burgs]

I hope this is the right place for this question.

Everything is supposedly always in motion -- relative motion, if I'm understanding things. Does that mean that something like a rock, say, is in motion? Or a dinner plate?

Pardon my apparent stupidity, but I've never taken physics (I'll need to fix that...never too old to learn!), and I don't know the answer.

[I'm Murrin]

If I'm understanding your question correctly, then yes.
A rock, stationary relative to the earth, is not stationary relative to--for example--a person moving on the surface of the earth. That much is self-evident. To go further, however, the earth is moving through space--so the rock, stationary on the earth's surface, is moving relative to the sun, moon, planets, and anything that is not in relative motion to the earth.

For something to be stationary in an absolute sense, there would need to be some frame of reference to which "stationary" could be applied. That is impossible, however, as it is only possible to measure velocity in relation to other objects with their own velocities.
Even if we could say, for example, that an object was sitting at the exact centre of the universe (where it would be "stationary" relative to the whole universe), it would still be possible to conceive that the universe itself is moving, and so the object is not stationary.

[The Laughing Man]

the molecules themselves are always in constant motion, which I think is what burgs question is relevant to. so a "stationary" rock is actually "vibrating". as far as I can tell, the only apparent non-motion in the universe is what comprises the spaces between everything else(molecularly speaking), which has to be made of something (and not dark matter, that is also comprised of molecules with spaces between them), and that as well may be hurtling along with the rest of everything which is indeed always moving and in perpetual motion, even the things that aren't there.

[burgs]

Thanks, both of you - your answers each helped.

Esmer, that's exactly what I wanted to know.

[Avatar]

I woulda made Murrin's explanation myself. But I agree with Esmer's too.

--A

[burgs]

Esmer's answer is what I needed. If that wasn't true, then an entire storyline just went THUD.

[I'm Murrin]

Heh. It was your mention of "relative motion" that sent me in that direction. The other possibility did occur to me.

[The Laughing Man]

glad I could help burgs.