How were galaxies and stars formed in the early universe?
When the universe began in the big bang, about 13.8 billion years ago,there was no carbon. It was so hot that all the matter would have been in the form of particles called protons and neutrons. There would initially have been equal protons and neutrons. However, as the Universe expanded, it cooled. About a minute after the big bang, the temperature would have fallen to about a billion degrees, which is about a hundred times more than the temperature in the sun. At this temperature, neutrons start to decay into more protons. If this had been all that happened, all the matter in the universe would have ended up as the simplest element, hydrogen, whose nucleus consists of a single proton. however, some of the neutrons collided with protons and stuck together to form the next simplest element, helium, whose nucleus consists of two protons and two neutrons. But no heavier elements, like carbon and oxygen would have been formed in the early universe. It is difficult to imagine that...