Would two grains of sand attract and collide in an empty universe?

I actually have more questions that you'd like me to ask, but one of them I tried to figure out on my own, and failed.

Imagine, for a moment, an empty universe, to avoid interference.
We then place two grains of sand, or something else if you wish, a great distance apart, say a light year. (a billion trillion quadrillion light years and rather heavy objects would also be fun ;) )
It is my understanding that these two objects, as long as they've got mass, will attract each other so, my question is:

Given similar parameters as previously explained, how long would it take for these two object to collide and how fast would they be travelling at the time of impact?

I would also be very interested in understanding the maths. as previously explained, I've tried, and failed. But I can understand if it isn't practical.

In any case, thank you for your time, I do hope you'll answer my question.

Best regards.
Felix Nielsen
Copenhagen, Denmark