Just how quickly is the universe expanding? Cosmologists attempt to answer this question in terms of the Hubble Constant, but the exact value of this constant is still a topic of debate.
Locally, spacetime is curved by the presence of massive objects. The total mass and energy density of the universe also has an effect on the overall curvature of space.
Is the universe infinite, or just really, really big? How can we know? To answer these questions, we examine the possible shapes of the universe.
The universe began as a singularity that started expanding in the Big Bang. But the Big Bang was no regular explosion. Rather, space itself expanded, so there is no center of the entire universe. The observable universe, on the other hand, is a different story.
Scientist George Efstathiou weighs in on the latest results from the Planck satellite and what they say about cosmic inflation, the first stars, and more.
There was no “before the Big Bang"—the Big Bang created both time and space as we know it.
Cosmologists have invoked the concept of dark energy to explain the accelerated expansion of the universe, but the nature of dark energy remains one of the most pressing questions facing modern cosmology.
Dark matter is a mysterious type of matter that doesn't interact with any form of electromagnetic radiation, i.e., light. Although we’ve never detected dark matter directly, a large amount of evidence points to its existence.
The Big Bang marked the beginning of the universe's expansion from a singularity — a single point that was infinitely small, infinitely hot, and infinitely dense. Cosmologists have designated several distinct eras for the universe's evolution from the first moments after the Big Bang to a billion years later.