Perpetual Motion

I didn't know where to put this so I put it here. Why are car companys making hydrogen fuel cells, why don't they just make a hydrogen internal combustion engine I know it can be done, but there must be something I don't understand because they seem to all want to make fuel cells and not internal combustion engines. Could someone please explain and educate me as to why hydrogen fuel cells are better than hydrogen internal combustion engines?

If the world has enough gravitational pull to keep the moon in orbit then how can we send satellites into space? And if the sun has enough gravitational pull to keep planets much further away from the earth in orbit then why does the moon not just orbit the sun? I'm really confused

If i put my toothbrush under a UV light to kill bacteria is it safe to put into my mouth?

The most coveted prize in particle physics - the Higgs boson - may have been glimpsed, say researchers reporting at the Large Hadron Collider (LHC) in Geneva. They need more evidence to claim a discovery. Sources:http://www.bbc.co.uk/news/science-environment-16158374 http://richarddawkins.net/articles/644214-lhc-higgs-boson-may-have-been-glimpsed

When you exercise lactic acid is shifted into your muscles, i believe getting a cold shower gets this stuff out. that's the only reason i can see behind it.

i know it is not possible but theoretically speaking if I put my hang in the Large Hardon Collider and the two particles wizz around and smashed into my hand what would happen? would my hang just explode? would there be a big hole in my hand? or is the collision so small it wont effect my hand at all?

Correct me if I'm wrong but the force/power you put in is equal to what you will get out.

I am currently doing my GCSEs I'm getting A-B grades and I am very interested in biology and mostly in physics, I'm looking to do a science subject A level in the near future. but I really don't see a good career path in physics as I struggle to see what job I could get, However biology offers allot to do with hospitals and health care medicine ect. as for chemistry i hardly know of any job opportunities. which subject opens the most opportunities? Thank you for reading.

Would this work if I leave a huge bucket of water floating in a vacuum in space and say I included a bunch of other elements like carbon and nitrogen (and anything essential for life) into the bucket then if I came back in 500 billion years, would there be life in the bucket?