Amongst other forces, gravitation.
yes
Scientists don't "think" it was gravity, scientists know that it was gravity.
Gravity
Dark matter is matter that does not interact via the electromagnetic force. We don't really know what dark matter is, exactly; there are several possibilities. We know that it interacts via gravity, meaning it has mass. It may, or may not, or SOME of it may, interact via the weak force as well.
The best theory is that all matter was created at the Big Bang
All matter. All the matter that exists emerged from the primordial cosmological state that we call the 'Big Bang'.
When Matter and anti-matter collided the Big Bang came into existence. But something still remains a mystery that how did the Matter and anti-matter come.
We have no idea what it was that exploded in the Big Bang, but it probably was NOT "matter" in the sense that we think of now.
Why our Universe is composed almost entirely of matter, with almost no anti-matter in it.
The matter that came out of the Big Bang was about 90% hydrogen and 10% helium.
the big bang
yes
The spread of mass and space. The matter-antimatter collisions HAD to happen after the big bang.
Ever since the Big Bang of about 13.7 billion years ago, all matter has been moving apart from each other. Fortunately, this tendency for matter to fly apart is more than counter-acted by the force of gravity -- at least over "short" distances (like the size of a galaxy).
The big bang was the source of the matter in the universe, some of which eventually formed the earth.
According to the scientists big bang is the main reason of the creation of this universe. after the big bang only the matter space and time came into being
Yes.