A definitive answer should be available once we understand what gravity is. Speculation before then. The absence any other objects eliminates some external influence but if gravity is determined to be a variable force, collision or separation is possible. Also, if your two object universe has...
I'm sure this idea has been considered since the invention of the particle accelerator. What would happen to an entangled particle if it's pair was collided in an accelerator? My guess is simply an end to entanglement but I'm too curious not to ask.
Forgot about Blue Shift. I work as a paint color matcher and green is always considered the opposite of red. But it's interesting to note that red shift is not universal!
I've always read that the proof of the expanding universe is the red shift in all observable stars/galaxies showing velocity away from Earth observation. I've also read that the Andromeda galaxy is on a collision course with our galaxy. Would'nt that mean the stars in Andromeda would be green...