The speed of light, and more precisely near the speed of light travel, has always fascinated me, but thinking about it raises the very interesting question, what happens if you actually get to, or near, the speed of light?
If we put aside the problems of getting an object up to that speed and simply imagine a bowler throwing a baseball and it spontaneously accelerating up to 0.9c, we only need to follow basic physics to predict what will happen.
A very simple answer to the above question is a lot of things, none of which are very nice, and none of which end well for the batter (or anyone nearby for that matter). At this speed (0.9c for those with a bad memory) everything else is practically stationary, the batter is stationary, the bowler is stationary, the spectators and fielders too, even the air molecules are stationary. Air molecules vibrate about at a rather pedestrian few hundred meters per second, where as the ball is moving at a few hundred million meters per second (269,813,21,.2 m/s to be precise). This means, as far as this thought experiment is concerned, that they are stationary. As a result, the laws of aerodynamics don’t apply here, the air molecules have no time to be forced out of the way and simply smack into the ball. This happens with such force that the oxygen and nitrogen in the air actually fuse with the carbon, hydrogen and oxygen in the ball. Each collision releases a huge burst of gamma rays, x-rays and other forms of energy, including light and heat.
This EM radiation expands outwards in a bubble centred on the pitcher’s mound, ionising any air molecules it meets, creating a shockwave of superheated plasma, approaching the batter at nearly the speed of light, only just ahead of the ball itself.
This fusion continues to occur on the leading edge of the ball as it moves through the air, slowing it down, similar to a rocket flying tail first while firing its rockets. However, the force of the on-going thermonuclear fusion is insufficient to even barely slow the ball. It does however begin to vaporise the surface, throwing out debris and particles at speeds close to the speed of light, this causes two or three more rounds of fusion as it hits the ionised air around it.
After around 70 nanoseconds the ball reaches the batter. The batter hasn’t even seen the ball leave the bowlers hand as the light carrying this information reaches the batter only 0.6 nanoseconds ahead of the ball. Collisions with the almost stationary air molecules has eaten the ball away to a slug of hot, ionised, expanding plasma, smashing into the air and creating even more fusion as it goes. The x-ray front of the plasma wave reaches the batter first; the disintegrating ball reaches the batter a split second later.
When the shockwave and what’s left of the ball eventually reaches the batter it’s still moving at a fair old lick, still reasonably close to the 0.9c it left the now vaporised bowler at. This shockwave scoops up and carries the batter, backstop and catcher all back through the stadium wall, as they and the wall begin to disintegrate. The shock wave of high energy EM waves and super-heated plasma continues to expand, and within the first 3 microseconds it has consumed the two teams, the stadium the car park and the surrounding half a mile of neighbourhood.
From an observers point of view on a distant hill, the first thing they would notice is a blinding flash of light, outshining the sun for several seconds and then, as it fades, a growing fireball rising into a mushroom cloud. The surrounding one and a half miles of city would be charred to a crisp and completely flattened, and a further two miles would have superficial damage, such as blown out windows and damaged roofs.
By an object, in this case a baseball, traveling at only 90% the speed of light, a nuclear explosion, somewhere in the region of about 1 kiloton has occurred, destroying a sizable chunk of populous city. Now this may seem an unlikely scenario, but it raises the interesting question, what if it did happen? In a future of faster and faster travel, we may have to severely limit the places where we can travel incredible speeds, or face the consequences…
N.B. A careful reading of the major league baseball rules implies that this would be a foul ball and the batter would be permitted to advance to first base, at least, where first base used to be
Two A-level physics books and my trusty calculator for most of the numbers