re: something small, at light speed
"This demonstrates your gross misunderstanding of relativistic physics. No object with a finite rest mass (i.e. something small) can EVER travel at light speed.
You can accelerate a small object (like a charged particle) to CLOSE to light speed, and in the process imbue it with enormous energy (mass), but you can never REACH light speed."
For me something traveling at 99.9% of speed of light is close enough to the speed of light for me to count it as light speed.
99.9% the speed of light is 299,492,665.5 m/s
Being more precise, what effect would a 1 meter iron sphere [weighing 4122 kg- at finite rest] hitting the earth at 299,492,665 m/s be?