the big bang theory?

The Big Bang theory is a collection of equations from all branches of science, that explains what happens when a universe begins from a very high state of energy density (what we could call extremely high temperature), and expands while cooling.

The Big Bang theory does not explain why the universe would have been in that state nor how it got there. It simply starts from that point (the Primordial Atom Hypothesis).

The Hypothesis came from observations made by Hubble (the famous astronomer -- the modern space telescope is named in his honor): all galaxies appeared to be moving away from each other and the rate of recession seemed linked to the distance. Twice as far = twice as fast.

Lemaitre looked at the data; he thought that if you ran all the speeds backwards, you'd find that at some point in the past, everything would have been all bunched up together. This is how the hypothesis was created.

Later, astronomers and cosmologists studied what would happen to such a universe and, little by little (as we found how different things behave at different temperatures), found that the universe we see does match what the equations predict for such a universe.

Almost 14 billion years ago, the universe was so hot that every single point in the universe would have been a black hole. Our understanding of physics prevents us from going further back, that is why we do not know what was there before.

That extra hot universe has been expanding (and cooling) ever since. In the first second, the forces were created (actually, the first particles that were created were the ones we call "bosons" -- they are the particles that cause the forces to keep things together or push them apart).

Then, after the first second of expansion, the "matter" particles began to appear. Quarks were probably first. The gluons (which had been created a fraction of a second before) quickly "tied" the quarks together to form protons and neutrons. Electrons and neutrinos were also created.

Protons and neutrons would hit each other with such force that some bigger atoms were created (helium, lithium, beryllium, but not much of the bigger atoms). After 3 minutes, the universe was already too cool for this to continue.

However, it was still hot enough for the photons (the bosons of the electromagnetic force) to pack a lot of energy. Enough to keep electrons away from protons: complete neutral atoms could not form.

After 300,000 years (yes, years), the temperature finally cooled around 3000 K (4900 F) and the photons were no longer strong enough to keep electrons apart from protons. They joined to form neutral atoms and the universe suddenly became transparent.

The total light of the universe at the time was suddenly liberated. That is what we see today as the Cosmological Microwave Background radiation.

The expansion is still continuing. The average temperature of the universe is now very low (2.75 K = -455 F) but it is still not zero.

The expansion continues. It is in fact a bit faster than expected, leading scientist to think that there could be another force that we do not know about (that is why it is called the dark energy, with "dark" meaning unknown, as in "we can't see what it is")

Big Bang Cosmology

The Big Bang Model is a broadly accepted theory for the origin and evolution of our universe. It postulates that 12 to 14 billion years ago, the portion of the universe we can see today was only a few millimeters across. It has since expanded from this hot dense state into the vast and much cooler cosmos we currently inhabit. We can see remnants of this hot dense matter as the now very cold cosmic microwave background radiation which still pervades the universe and is visible to microwave detectors as a uniform glow across the entire sky.

The Big Bang is the cosmological model of the universe that is best supported by all lines of scientific evidence and observation. The essential idea is that the universe has expanded from a primordial hot and dense initial condition at some finite time in the past and continues to expand to this day. Georges Lemaître proposed what became known as the Big Bang theory of the origin of the Universe, although he called it his 'hypothesis of the primeval atom'. The framework for the model relies on Albert Einstein's General Relativity as formulated by Alexander Friedmann.

this information is from wikipedia not my own this is the URl

As astronomers discovered galaxies, they noticed that they were all moving away from each other.

So a long time ago, they must have been much closer to each other, and...

At some point in time, they must have come from one singular point.

The Big Bang theory states that all this matter from all these galaxies, (and everything else) exploded and began to expand very rapidly.

The universe today is the size it is, because of the time it has been since the Big Bang.

In the future the galaxies will be far apart and our night sky will have no stars. Sad.

the big bang theory is a bunch of bull that scientists made up

God said BANG! ...and there it was