Changes

::The radial velocity of the Andromeda galaxy with respect to the Milky Way can be measured by examining the Doppler shift of spectral lines from stars in the galaxy.  Using this the Andromeda Galaxy is approaching the Sun at about 100 to 140 kilometers per second.[http://www.space.com/scienceastronomy/astronomy/galaxy_collides_020507-1.html]  We can then estimate how long it would be before the galaxies meet up using math.  That is how we get the estimate of 2.5 billion or so years.  I will however concede that the collision is uncertain because the two galaxies may move past each other instead because we cannot exactly measure Andromeda's transverse velocity.  Because of that, I will change the text about the galaxies colliding to being uncertain.  Is this acceptable?

::The radial velocity of the Andromeda galaxy with respect to the Milky Way can be measured by examining the Doppler shift of spectral lines from stars in the galaxy.  Using this the Andromeda Galaxy is approaching the Sun at about 100 to 140 kilometers per second.[http://www.space.com/scienceastronomy/astronomy/galaxy_collides_020507-1.html]  We can then estimate how long it would be before the galaxies meet up using math.  That is how we get the estimate of 2.5 billion or so years.  I will however concede that the collision is uncertain because the two galaxies may move past each other instead because we cannot exactly measure Andromeda's transverse velocity.  Because of that, I will change the text about the galaxies colliding to being uncertain.  Is this acceptable?