Just how void of matter is space?

Question

My question really is this: If you left planet earth in a random direction and traveled for say, 5 billion light years at the speed of light, what would be the chance that you'd collide with another solid object (not gas)?

Answer 1

Not much.  The CMBR - the Cosmic Microwave Background Radiation has travelled for 13.7 billion years.  Most of it doesn't hit anything.

The average density of the Universe is about 3 times 10^-27 kilograms per cubic meter.  It's something like a hydrogen atom per cubic centimeter.  But since most of the matter is clumped together, most of empty space is really empty.

Unless you count the quantum foam.

Answer 2

very likely as solid objects are hitting the earth all the time (every day).

if you are talking about significantly large solid objects like planets then it is less likely but 5 billion light years gives it a good chance of colliding with something.