dipper1985 t1_ja1mx7x wrote on February 26, 2023 at 4:08 AM

Reply to comment by PyrrhoTheSkeptic in Explosions in space movies? by DemonOfTheAstroWaste

> the fact that hitting a spec of dust at anything near light speed would obliterate the spacecraft,

How is this, though? You can hit a bug going 90 mph and it just splatters on your windshield. A rock flies off your fender etc.

Ishidan01 t1_ja1or2o wrote on February 26, 2023 at 4:24 AM

Bug soft, so it splats. A pebble at 90 mph WILL crack your windshield, or dent your fender.

Force equals mass times velocity SQUARED: velocity means more to force than mass, so if you have a very high velocity, a very small mass carries a lot of force.

Word correction: should have said energy, not force.

dipper1985 t1_ja1pzea wrote on February 26, 2023 at 4:36 AM

>Force equals mass times velocity SQUARED: velocity means more to force than mass, so if you have a very high velocity, a very small mass carries a lot of force.

This is kind of the answer I wanted, thank you.

rockmodenick t1_ja24sg2 wrote on February 26, 2023 at 7:20 AM

So much of modern ballistics is based on this model it's shocking it isn't more widely known.

PyrrhoTheSkeptic t1_ja1ourv wrote on February 26, 2023 at 4:25 AM

90 mph is almost nothing.

To help you understand, think about tossing a bullet back and forth with a friend. You can do that without your hand getting hurt at all, because the bullet is not going very fast. However, that same bullet being shot from a gun is going very fast coming out of barrel, and it hitting your hand at that speed makes a very significant difference for how it would affect your hand if the bullet hit your hand.

And the speed of a bullet out of a gun is practically nothing compared with going near the speed of light; the forces involved are vastly greater with vastly greater speed.

Im_Chad_AMA t1_ja1oaap wrote on February 26, 2023 at 4:20 AM

The speed of light is 300,000 km/s, or about 671,000,000 miles per hour. Quite a few orders of magnitude larger than 90 mph.

The kinetic energy of an object depends on both its mass and its velocity. A fly against your car is light enough, and the velocity of your car is small enough, that a collision between a car and a fly does nothing to the car. Once you approach lightspeed though, even a speck of dust could wreak havoc