'Science' doesn't believe that there is life on other planets. Some scientists think that is a possibility that there is life on other planets but with out some sort of evidence it will not be accepted, assumptions need to have evidence behind them. Evidence exists for black holes and black matter - just because it can not been seen doesn't mean that there isn't evidence for their existence.
I just want to be clear on something, I tried to be very specific here. I didn't refer to science. i referred to scientist. There's a difference, science is based on what can be proved; people go by what they believe is possible in order to study the science of it. That is what I mean. Some scientist believe there is life, not science.
It's interesting that you said "just because it can not been seen doesn't mean that there isn't evidence for their existence" since there is evidence that God exists but scientist do not accept it as evidence yet religious people do. I myself have witnessed divine intervention, some would call it coincidence, I say things don't just happen for no reason.
Science is not based on belief - it is based on evidence. In my scientific career I have seen the working model for several large plant biology systems change as new evidence was found. These were across the entire field world wide while in my project the working model changed every couple of months as new experiments supplied evidence that either supported or contradicted the model. If science was belief I would have made the evidence fit the model - not the model fit the evidence.
Actually science is based one belief. If scientist didn't believe that something may exist, they would not try to find it. Some scientist believe in parallel universes, others believe time travel is actually possible and some even believe that warp speed may actually be possible. At one point in time these things were thought to be only in sci fi movies yet today we have scientist who "believe" in the possibility that they either exist or are possible. Again, it's not because science just showed it to them, it's because they believe it's possible.
Tell me Basmas, do you wake up every morning because it's simply a natural reaction or a programming inside of you like a computer or because you "believe" you are suppose to? everything I do I do because I believe I am suppose to. thieves steal because they believe they are suppose to, cops give tickets because they believe they are suppose to and some don't give tickets because they believe at that moment they don't have to. get my point? Everything in life is based on a belief. Obama became President because of a belief.
Science is based one belief, the evidence is to prove or disprove this belief.