4:01 am and the clock goes tick-tick-tick Musings

To help me back to sleep I try to challenge myself to thinking something.

I've worked through the perpetual motion machines, came up with a great idea, and almost convinced myself that I understood the theory of general relativity.

http://pdubyah.com/2013/11/26/4am-and-the-clock-goes-tick-tick-tick-musings/

This morning I was trying to work out what you'd see for two objects that are colliding, both of which are travelling at, for instance, 75% of the sped of light.  The closing speed would therefore be 1.5X the speed of light.

For each of the objects they would observe something approaching them at .75% of the speed of light, but if they could measure that they should know that they are closing at 150% of the speed of light?

And what would an observer view.

Anyway, putting that aside, the other thought train has been on super-powers and why I think that most of them are rubbish, the flight, the invisibility, the teleportation, the mind reading and thought control.

The latest one though, re-sizing. The ability to grow or shrink. Clearly nonsense.

Your mass couldn't change, you can't shed or gain mass. So if you shrank to say the size of a mouse, you'd still have to weigh 140lbs. There would also be a limit on the size you could shrink to, and this would be based on the 'space' that atoms meed. You can't cram more atoms into a space than will fit.

Would you turn into a black-hole?

Did I just show up my ignorance of science again?