Not only does gravity keep the planets moving around the Sun, it has also had, and continues to have, a major role in physically shaping the universe. To help you understand this role let us travel back to the beginning of time, which scientists now estimate to be about 15 billion years ago, give or take a few hundred million years.According to the current generally accepted theories, the universe began when an infinitely compact object containing all the matter and energy in existence suddenly exploded, flinging all the raw material of the universe outward in a rapidly expanding sphere. We call this explosion the Big Bang.
Now, for the most part, matter was distributed very evenly throughout this expanding universe. However, there were a number of tiny “dimples” in this distribution where matter was, for some reason, just a little more densely packed together. If the universe had been perfectly smooth and had lacked these little imperfections, the pull of gravity on every particle of matter would have been equal from every direction. But it wasn’t.
These little dimples became the focuses of gravitational attraction and eventually evolved into coherent structures such as stars and planets. In turn, gravity pulled these stars and planets together into close knit groups called galaxies and these galaxies became part of even larger strands of matter known as clusters and super clusters. In short, the universe as we know it today would never have come into existence if it weren’t for the work of gravity.
