The first ever What If, that made it a hit (in more than a sense). 0.9c is not fast enough to make a really big difference in mass or time for the ball, but its

The first ever What If, that made it a hit (in more than a sense). 0.9c is not fast enough to make a really big difference in mass or time for the ball, but its speed alone is bad news in something like a dense enough atmosphere.