snowyowl wrote:rmsgrey wrote:Of course, at sufficiently high speeds (.9c may well not be high enough) the relativistic baseball simply isn't around long enough to dump enough energy to cause a problem - most of the energy ends up carried into deep space rather than forming a mushroom cloud in the stadium. Sure, individual atoms in the way get shredded, but surely there just isn't time for much of the energy to get dumped into the surroundings...
You'd need there to be enough mass in the way to drop the ball's speed down to around the (local) speed of sound for energy to bleed off significantly - an air-atom colliding with a ball-atom will give two atoms still traveling at nearly half the speed of light in the ball's original direction - you need to slow down a lot before any lateral component of motion becomes significant.
Yes, I think the ball will easily escape the Earth's gravity and carry off most of its kinetic energy into deep space. But the X-rays thrown off by the nuclear reactions will still be very impressive, and I'd expect air molecules just close enough to the ball to be pulled along in its slipstream but not close enough to actually hit it would dump most of their energy into the environment. There would definitely be a sizeable explosion.
Taking the conversation in a new direction: Isaac Asimov wrote a short story where a journalist recalls the tale of a man who was killed by his rival using an anti-gravity machine and a trick shot on a pool table. Because the pool ball was free of gravity, ALL gravity, it was able to accelerate to near-c and punched straight through the man's chest (instead of floating from the table gently) before heading out into space (if memory of the story serves me correctly).
I'm guessing the journalist wouldn't be talking to anyone that
It also gives us a device that can get the baseball up to speed.