-
I won't repeat what is already written above, the red-shift of distant galaxies, the CMB, etc. But is it a proof? No. Science expect an experiment to be repeated in the same conditions to become a fact. Something we can't do with the Big Bang and, therefore, it must remain a theory.
This being said, what are the alternatives? As far as I know there are only the "young earth creationists" who claim that the universe is only six thousand years old and was made in six days.
What could be a scientific alternative? The static universe? Even Einstein, when he was asked if he thought the universe was expanding or contracting, prior to Hubble's discovery of the red shift, answered: "I don't know. All I know is that nothing is static in the universe!"
Perhaps the Big Bang is only an illusion, similar to the horizon. A thousand years ago, seafarers were afraid to sail to the horizon and fall at the edge of the earth into oblivion. Perhaps the Big Bang is the same thing; something that will always appear to have happened 13.7 billion years ago. But it would be nice if we had something to base that theory on, right? Just a "feeling" isn't enough in science.
This being said, what are the alternatives? As far as I know there are only the "young earth creationists" who claim that the universe is only six thousand years old and was made in six days.
What could be a scientific alternative? The static universe? Even Einstein, when he was asked if he thought the universe was expanding or contracting, prior to Hubble's discovery of the red shift, answered: "I don't know. All I know is that nothing is static in the universe!"
Perhaps the Big Bang is only an illusion, similar to the horizon. A thousand years ago, seafarers were afraid to sail to the horizon and fall at the edge of the earth into oblivion. Perhaps the Big Bang is the same thing; something that will always appear to have happened 13.7 billion years ago. But it would be nice if we had something to base that theory on, right? Just a "feeling" isn't enough in science.
-
A key piece of evidence was predicted from the hypothesis in the 1940s, the CMB (cosmic microwave background radiation), however, it had never been detected. Then, in the 60s, it was detected by accident and initially thought to be interference. The ability of a hypothesis to predict future observations is a very strong indication that said hypothesis is correct.
Expansion of the Universe is also a factor. The Universe must have been smaller before, if it is expanding. There must have been a source of energy large enough to scatter all matter across the Universe and make it expand.
Expansion of the Universe is also a factor. The Universe must have been smaller before, if it is expanding. There must have been a source of energy large enough to scatter all matter across the Universe and make it expand.
-
None, actually. The current theories about the evolution of the universe all commence a minute fraction of a second AFTER the supposed "big bang" occurred. Before then, the current properties of space/time were not operative, and current cosmology cannot go back beyond that. So whether there was a "big bang" remains speculation, and maybe will always be so.