Aliens

Buddha Dhamma says there are 31 realms associated with each habitable planetary system (cakkavāla). And there are an infinite number of them in the universe (this latter fact has been confirmed by science).
– It is likely that life in other cakkavāla is not that different from ours.

However, the nearest cakkavāla (star with planets) is about 4 light-years away. That means a spacecraft traveling at the speed of light will take four years to get there.
– Since it is unlikely that even one-hundredth of the speed of light can be achieved for a spacecraft, travel to another cakkavāla is highly unlikely.

See, “Pāṭihāriya (Supernormal Abilities) of a Buddha – Part I“

There can be only one Buddha for a group of 10,000 cakkavāla within a given period of time. The next Buddha for us will not appear for a few more million years.
– There can be multiple Buddhas in different groups of 10,000 cakkavāla simultaneously.

I think there is some information on the system of 10,000 cakkavāla in the post I referred to in the previous comment.