The electromagnetic attraction between negatively charged electrons and positively charged protons in the nucleus causes the electrons to orbit the nucleus of the atom, just as gravitational attraction causes the earth to orbit the sun.
We must accept that time is not completely separate from and independent of space, but is combined with it to form an object called space-time.
As long ago as 340 B.C. the Greek philosopher Aristotle, in his book On the Heavens, was able to put forward two good arguments for believing that the earth was a round sphere rather than a flat plate.
According to 'M' theory, ours is not the only universe. Instead, 'M' theory predicts that a great many universes were created out of nothing.
A zero-gravity flight is a first step toward space travel.
One is always a long way from solving a problem until one actually has the answer.