they think that space is neverending and never stops.
So they can explore space
...
mmm
It is so that scientists, could investigate the effects of space exploration.
scientists were curious and asked questions.
there is just more space no one has seen is before so no one knows what is beyond the galaxies. hmm i think beyond the galaxies there are no spacetime so nothing exist but time doesn't ends so there is no end to space so there might be vacum beyond the galaxies.
Space is always gonna go on and on and on. IT NEVER ENDS! so the answer to your question is that space keeps going on and will never end.
it is so very dangerous to travel if it is not tested by the scientist
No, I don't think so.
So that scientists could investigate the biological effects of space travel without risking the lives of humans.
actually i think so Marie curie
No, they don't. There is so many (beyond numbers) galaxies that it is impossible to know everything.