How far can we travel in space before we hit something?

eddie p asked: To explore my question more I will draw on the hypothetical series of Star Trek (and various other SC-Fi’s) where you can see out of the windows of Enterprise the stars flying past. If we were able to master warp speed, could we theoretically plot a course that could take us thousands [...]

How big are stars in comparison to the Earth?

Emma Monkey asked: If you can see stars that are billions of light years away, then I figure they must be huge up close, but on Sc-Fi programmes like Star Trek they still look the same size as they do from Earth. So can you please tell me how big are they really?