After a million years or so, the hydrogen and helium began to clump together in swirling clouds and strands. Eventually, the gas clouds condensed into galaxies of countless stars. The black heart of a galaxy Quasars are the universe's most intense energy sources - as bright as 100 galaxies, yet no larger than our solar system. They are billions of light-years away yet emit radio signals that are easy to pick up. Because they are so far away, scientists think that they burst on the universe when it was young.
Quasars are the energy of the gas spiralling in.
In 1676 Ole Roemer showed how an eclipse of Jupiter's moons was seen 10 minutes later because light from them took that time to reach us. This shows that we may not see events at the same time they happen. If we look at a star 5 billion light-years away, we see it as it was 5 billion years ago. From somewhere else, it is seen at a different time. So the timing of events depends on where you are.