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Acceleration Question

Started by Endemoniada Nov 25, 2003 at 11:32 PM 7 replies 1k views

Original Post

131

Nov 25, 2003 at 11:32 PM

Hi guys, I''m learning some physics and am trying to fully understand acceleration which is a little hard to grasp so here is my question: Lets say I throw a sphere in a perfect vacuum, and lets say nothing at all will affect it (no gravity, no collisions, no damage because of low/high heat or high speeds, etc.) will it keep going faster and faster until it hits light speed (or just under light speed) ? Even if when it left my hand it was only going, say, one mile per hour ? That''s pretty crazy if it''s true.

DrEvil

155

DrEvil

Nov 25, 2003 at 11:34 PM

no it wont

Atheist

Nov 26, 2003 at 12:27 AM

... because it doesn´t accelerate.

NLDEV

Nov 26, 2003 at 12:31 AM

Its velocity remains constant. But without any force acting upon the ball, acceleration is 0:

a = F/m
a = 0/m
a = 0

Eric Lengyel

108

Eric Lengyel

Nov 26, 2003 at 1:03 AM

Actually... Recent developments in cosmology (the study of the cosmos as a whole) seem to show that empty space contains a tiny bit of negative energy known as the vacuum energy. This implies a nonzero cosmological constant in Einstein''s field equation and is responsible for the fact that the expansion of the universe is accelerating. So, a sphere in a vacuum that is moving away from some initial position will gradually accelerate, albeit at an immeasurably small rate until it has covered intergalactic distances. This has absolutely no impact on game programming, I know, but it''s interesting stuff.

eighty

Nov 26, 2003 at 3:23 AM

Could quantum fluctuations cause it to accelerate? I do realise such a lucky event only could happen once every few billion years, and that the overall effect would be that nothing ever changed, but still...

[edited by - eighty on November 26, 2003 4:24:16 AM]

Endemoniada

Author

131

Endemoniada

Nov 26, 2003 at 11:46 AM

Thanks guys. I understand now.

sadwanmage

Nov 26, 2003 at 4:48 PM

eighty, no quantum effects couldn''t, assuming the overall effect is nothing changes. conservation of momentum still holds, so it would have to do something to go somewhere.
THat doesn''t stop it from, say, randomly emmitting billions of photons in the same direction, which would push it marginally. Or it might randomly split in two, in which case they might move away from each other.

Or suppose you could talk about a quantum object jumping from one location to another (uncertainty), but that is not the same as velocity, nor a macroscale phenomena (even given good luck, it just cannot happen if it is collapsed all the time).

Hope that makes sense...

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