pillar of creation
The Universe is extremly huge and the actual size of the universe can't be measured but it is estimated that the diameter of the observable universe is about 28.5 gigaparsecs.
The universe for every million parsecs of distance from the observer, the rate of expansion increases by about 67 kilometers per second.
As the universe expands millions of new galaxies form creating new stars and new planets with it.
I personally feel that as the universe expands the possibilities of new life forming is endless.
Many people believe that aliens exist because of the huge amount of planets that can house life.
The big bang is what caused the universe to form
"Because there is a law such as gravity, the Universe can and will create itself from nothing. Spontaneous creation is the reason there is something rather than nothing, why the Universe exists, why we exist." -Steven Hawking
One alternative theory is the Steady State universe. An early rival to the Big Bang theory, Steady State posits continuous creation of matter throughout the universe to explain its apparent expansion. This type of universe would be infinite, with no beginning or end.
The Eternal Inflation theory posits that inflation never stopped, and has been going on for an infinite length of time. Somewhere, even now, new universes are coming into existence in a vast complex called the multiverse.