Actually, Jayjay Kelvin can't be blamed for his attitude. All he was saying was that it was highly improbable that a spaceship would be hit by a meteor. In one way, he was perfectly right, and, in another, he was dead wrong.
How small must a piece of matter be before it is no longer a meteor?
Fortunately, the big hunks rarely travel at more than about two times ten to the sixth centimeters per second, relative to Sol, in the Solar System. But there are little meteors—very tiny ones—that come in, hell-bent-for-leather, at a shade less than the velocity of light. They're called cosmic rays, but they're not radiation in the strict sense of the word. A stripped hydrogen atom, weighing on the order of three point three times ten to the minus twenty-second grams, rest mass, can come galumping along at a velocity so close to that of light that the kinetic energy is something colossal for so small a particle. Protons with a kinetic energy of ten to the nineteenth electron volts, while statistically rare, are not unusual.
Now, ten million million million electron volts may be a wee bit meaningless to the average man, so let's look at it from another angle.
Consider. According to the well-known formula E = mc2, a single gram of matter, if converted completely into energy, would yield some nine hundred million million million ergs of energy. An atomic bomb yields only a fraction of that energy, since only a small percentage of the mass is converted into energy.
If all of the mass of an atomic bomb were converted into energy, the test in Alamogordo, New Mexico, 'way back in 1945, would probably have been the last such test on Earth; there wouldn't have been anyone around to make a second test.
So what does this have to do with cosmic ray particle? Well, if that atomic bomb had been moving at the velocity with which our ten-to-the-nineteenth-electron-volts proton is moving, it could have been made of sand instead of U235. It would have produced ten thousand million times as much energy as the total disintegration of the rest mass would have produced!
Kinetic energy, my children, has a great deal more potential than atomic energy.
But we digress.
What has all this to do with Jayjay Kelvin?