[wallijonn]

Have you ever watched a Boening 747 take off? It amazes me - something so big looks like it is going so slow into the air. But I know that it is going over 200KPH, the same velocity as a smaller plane. But the smaller plane "seems" as if it is taking off faster.

So when I saw the Star Trek episode where Enterprise goes back to 1962 and saw it going up slowly I knew what they were talking about.

Speed is relative to mass - the bigger the mass, the slower it seems to be rotating. At least that's the way it seems to my mind. It may be rotating at the same speed as a smaller satellite but it seems like it is spinning slower.

 

[Megaptera]

What's actually surprising is that if you have two different bodies rotating on their axis at the same rate, the bigger one is actually going "faster". Sort of.

Imagine you're on Planet Alice, which is 10 kilometers around. It makes one complete rotation every minute, let's say. That means that if you stand perfectly still on the equator, after one minute you've moved 10km, in a complete circle. Now let's go to Planet Bob, which is 50km around. It's also rotating at 1rpm. Stand on the equator here and after an hour, you've moved 50kmh. In terms of rpm, Bob has to rotate five times as fast as Alice just to keep up.

The same thing hold true for orbits around the sun. Let's say Bob is pretty close, and its orbit only takes it through 1,000,000 km of space. (By the way, I am totally making these numbers up. In reality, even though a million km is 25 times the distance around the Earth, an 'orbit' that small would be inside of the sun. Space is pretty fricken' big.) Alice is a little bit further out, and its orbit takes it through 100,000,000 km of space. Let's assume they're both orbiting at a rate that will take them back to their starting point in exactly one year. Wait a year on Bob, and you've gone a million km. Now wait a year on Alice and you've gone a hundred million km. Alice is orbiting 100 times as fast as Bob, just to go at the same rate.
(I should really point out again that I'm just making these numbers up for convenience. The less distance an object has to travel in its orbit, the faster it moves around it. It just has to work that way. Don't let me mislead you

)

But that all has nothing to do with relativity. It's just basic mechanics and dynamics -- nothing different than gears, wheels, or anything else that spins or moves in circles. Relativity is a whole different bag of weirdness.

 

[wallijonn]

RickG,

The picture looks like it's oval - the 2D representation of the cup which shows the Ovaltine 'inside the cup' is oval.

 

[chadbang]

Quote:

Originally Posted by wallijonn Speed is relative to mass - the bigger the mass, the slower it seems to be rotating.

This is why, as I previously posted, gentlemen shouldn't dance over the age of 35.