Which has the greatest density asteroids at rest or an asteroids traveling nearly at the velocity of light?

Answer 1

Well now, here we go again. When you start talking about the properties of

things moving near the speed of light, now you have to start specifying WHO

is measuring them.

-- If two scientists together got ahold of a piece of an asteroid one day,

brought it to their lab, measured its mass and its volume, calculated its

density, and each of them wrote the number down in his notebook, AND THEN . . .

-- If one of them somehow went to space and landed on that same asteroid,

while the other scientist, still on Earth, watched the asteroid shoot through

space at some high speed, THEN . . .

-- The travelling scientist, sitting on the asteroid and shooting through space,

could dig up a lump of it, measure its mass and volume, calculate its density,

check the number against his notebook, and he would find that it was still the

same density as before. It had not changed since he and his colleague did the

same measurement together in ther lab.

-- The scientist who stayed home ... if he had some way to measure the mass

and volume of a lump of the asteroid as it whizzed past him at a high speed ...

would find that its density has increased. That's because once the asteroid

started moving, any lump of it would shrink in the direction of its motion, while

the mass of the lump would become larger. More mass, divided by less volume,

would show up as increased density.

-- If the two scientists could communicate, they would get into a terrible argument.

Their answers would be different, and they would BOTH be correct.

-- And it would not even depend on the speed of the asteroid. It would happen

at ANY speed ... it's just that the DIFFERENCE would become greater as the speed

increases.

If you understand this, then you haven't read it carefully enough. What it describes

can't be. But it is.

I'm so glad you asked.