Added 3 new A* pages:So how big is big? I actually did some math for this, because I wanted to make sure the threatened impact was threatening enough. The non-relativistic formula for impact energy (how big the kaboom will be--for speeds of 14% light and above you apparently need to use a more complicated formula) is|
kinetic energy (joules) = 0.5 x mass (in kilograms) x velocity (in meters per second) squared
Proctor told us the speed of the approaching ship: 10% light speed, ie 30,000,000 m/s. Then he says the ship is 10x the size of a "Galaxy-class freighter." How the heck big are those? Well, I thought I'd see how it would go if we say one of those is about the size of a modern supercarrier, or roughly 100,000 tons, which is roughly 100,000,000 kg. What a nice round number to work with! So this ship is ten times that, *but* if we figure it's burned up its fuel accelerating to that speed, and its fuel took up say 90% of its mass, then it's down to 10% of its starting mass, which is then the 100 million kg figure we already had. Man estimating is cool.
0.5 x 100,000,000 kg x (30,000,000 m/s)^2 = 45,000,000,000,000,000,000,000 joules
So the impact energy would be 4.5e^22 joules, which is a lot. To put it in numbers that might correspond to something I can understand, according to this table, it's equivalent to about 22 million conventional thermonuclear warheads, or two Shoemaker-Levy impacts; Shoemaker-Levy was the comet that broke apart and hit Jupiter in 1994; it was going "only" 60,000 m/s, but consisted of dozens of fragments, some as large as 2 km across, and Wikipedia says the largest of its impacts was equal to 600 times the world's nuclear arsenal, and created a dark spot in Jupiter's atmosphere twice as wide as Earth--and there were at least several other similarly sized impacts from other chunks, some of which are seen here (the biggest one was "G"):
image by NASA (source)
So two Shoemaker-Levy's--although still only about 1/10,000th of the energy necessary to boil off all of Earth's oceans and atmosphere--should be pretty dangerous to an inhabited planet, one would think, and that's about what Paralt 27-2 is facing here. :o