The universe doesn't have an outer perimeter, and nothing exists outside it, because there isn't an outside. As an analogy, consider the shape of our galaxy, the Milky Way.

Evidence for the flatness of the universe also shows up in what's known as the critical density. At the critical density, a hypothetical universe would be flat and would eventually stop ...

Feast your eyes upon the first color—not the first one in this book of course, but the first color in the universe. This bright-hot glowing peachy orange didn’t exist until approximately ...

Today’s universe continues to expand, even accelerating. This forces physicists to introduce dark energy to explain this unusual acceleration. Little is known about the nature of dark energy.

The Big Bang: The moment when our universe — everything in existence — began....Right? Turns out, it's not quite that simple. Today, when scientists talk about the Big Bang, they mean a period ...

The Sun may be the center of our solar system, but it is not the biggest star in the universe. The Sun has a mean radius of around 696,000 kilometers, or 432,450 miles . In comparison to UY Scuti ...