Our universe began in a burst of light and energy that sent all matter spinning out into the void. This new cluster is believed to have initially taken a lenticular shape. Although we cannot see back in time to that event, we can see relatively close to it. The energy sent out by that explosion is still reaching us today.
Some scientists thought that eventually the universe would stop expanding, and collapse back into itself, but there are a few things keeping that from happening. Firstly, our universe doesn't have enough mass to fall back in on itself. Secondly, simple momentum is not the only thing driving us outward. Some sort of anti-gravity force, called dark energy, is pushing galaxies apart, and we are actually gaining speed.
Some scientists thought that eventually the universe would stop expanding, and collapse back into itself, but there are a few things keeping that from happening. Firstly, our universe doesn't have enough mass to fall back in on itself. Secondly, simple momentum is not the only thing driving us outward. Some sort of anti-gravity force, called dark energy, is pushing galaxies apart, and we are actually gaining speed.