Why does GSim say the mass of an asteroid is approximately0?

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wtg62
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Why does GSim say the mass of an asteroid is approximately0?

Post by wtg62 »

As some of you may know, putting a tilde (~) before a number means that you're approximating. ~5 translates to "about five"
I sort of have to wonder, how come GSim says in the edit menu for asteroids that the mass is ~0?

I don't know if anybody has asked this before.
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testtubegames
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Re: Why does GSim say the mass of an asteroid is approximate

Post by testtubegames »

Ha - nobody *has* asked this before. Or, at least, I can't remember answering it.

The basic issue is that if the mass were truly zero... then it shouldn't feel any gravitational force at all. It'd travel in a straight line forever, ignoring planets, stars, etc. (Since the force felt is proportional to m, and yes, for the moment we're purely in the classical realm, no relativity in this discussion.)

So, the mass is 'kinda' zero. It's an object that accelerates due to the force from other masses... but exerts no force on them whatsoever. Basically, it has a negligible mass.
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wtg62
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Re: Why does GSim say the mass of an asteroid is approximate

Post by wtg62 »

Ah, nice answer! Makes sense, since (M₁M₂)/r² would be 0 if M₁ or M₂ were 0.
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testtubegames
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Re: Why does GSim say the mass of an asteroid is approximate

Post by testtubegames »

wtg62 wrote:Ah, nice answer! Makes sense, since (M₁M₂)/r² would be 0 if M₁ or M₂ were 0.
Bingo - well put.
AndyVelwest
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Re: Why does GSim say the mass of an asteroid is approximately0?

Post by AndyVelwest »

OK, I get all that, but I'm still curious. What value do you use in your calculation, is it .01, .00001, or what? And how did you choose that number? Did you try others? Thanks. Just found this site yesterday, it's all very cool.
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testtubegames
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Re: Why does GSim say the mass of an asteroid is approximately0?

Post by testtubegames »

AndyVelwest wrote:OK, I get all that, but I'm still curious. What value do you use in your calculation...
Zero. That ensures the asteroids don't pull on anything else, even a little bit.

In general, I calculate the acceleration on an object as opposed to the force, which means there isn't any mathematical problem with having a zero-mass asteroid. Other objects accelerate them, but they don't accelerate other objects. Putting in the 'about' sign just lets me dodge the philosophical implications of it all.

Also - welcome to the forums and the site - glad to hear you're enjoying it!
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