Dictionary.com says a billion is "a cardinal number represented in the U.S. by 1 followed by 9 zeros, and in Great Britain by 1 followed by 12 zeros." It also seems it indicate that British definition is no longer used, although it's unclear on that.

Does a billion still represent two different numbers among scientists? If not, when did this change? Wouldn't older papers still use the old definition? Has this discrepency caused any practical problems in scientific projects--particularly in relation to astronomy and physics?

Cheers,

John

If the human race was wiped out now due to say a cataclysmic event how long would it be before there was no proof that we ever existed, for example all buildings and objects to erode away. If this could happen in say a million years could we have existed earier than what we originally thought and the same thing have happened before.

As I understand it the "Spooky Action at a Distance" phenomenon was talked about by Einstein in 1935, and was experimentally observed for the first time in 1972.

What was it that caused this paradox to even be considered? Was it the result of some maths calculation? A thought experiment? A wild guess?

My question is really about the  oddity of such a strange result to be considered when there doesn't seem to be any experimental, or observational data to go on.

If all the stars are orbiting a super-massive black hole at the centre, why are they only orbiting in roughly one plane? Granted that once they have momentum in that plane the centripetal force of gravity should tend to keep them in that plane, but after the big bang what force caused them to form in that shape?

If three bodies each move at constant angular speed, each following a trajectory given by r=R.(1+K.cos(A+n.120)) and each of these bodies rotates about its own axis in a manner that balances out the torque variation due to radial change, what angular velocity must the system rotate at before a gravitational force starts to be resolved at the system reference point in the direction A=0?

I always thought it was time, but I've been informed that space/time composes part of the third dimension.

If life developed on a planet which wasnt very rich in iron what could could be used as a suitable subsitute for it? And would this difference in metal restrict these lifeforms to any constraints??

Particle accelerators such as that at CERN accelerate particles to high speeds before colliding them and measuring the particles given off.  However it is almost always protons that are collided, or ions or neutrons. Why doesn't anyone ever collide electrons?  Even if you did collide electrons, what sort of things would you see given off?

EDIT:

thanks for the answer, i'm also interested in what sort of particles are formed from electron collisions and how much energy is needed to form these particles.