Why don't two spaceships at 90% light speed see each other at 180% the speed of light?

[lnsanity]

If Earth is here 0 and I go at 90% the speed of light in that direction <--in my spaceship and my friend is going a 90% the speed of light in that direction --> in is spaceship so it look like this. 90% <-- 0 --> 90% relative to people on Earth we each go at 90% the speed of light in oposite direction, how come relative to my friend I would not be going at 180% the speed of light ? and if so what would be my speed relative to my friend if not 180% ?

From the point of view people on Earth it certainly seem to me that they would see us distance each other at faster than light speed... !?

 

[Matterwave]

From the Earth's point of view, the distance between you two is increasing at 1.8c. From your point of view, and from your friend's point of view, the distance between you two is increasing at only .9945c.

See: http://en.wikipedia.org/wiki/Velocity_addition_formula

 

[ghwellsjr]

Somebody else just asked this same question less than 12 hours ago. Take a look at this thread:

https://www.physicsforums.com/showthread.php?t=570959