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One hundred years ago, a young physicist presented a paper to the Prussian Academy of Science--a paper that we now recognize as symbolizing the birth of general relativity. By this [...]

Figuring the distance to stars and galaxies challenged both ancient Greeks and modern cosmologists. The universe may be three dimensional, but our view of it is not. The sky looks [...]

Some of astronomy's greatest moments brought incandescent insights, among the greatest the human mind has ever produced. Hubble's realization that the universe was expanding and Copernicus's dream of the moving [...]

From the point of view of a physicist, whenever anything happens in the world, it happens because of the action of some combination of four fundamental forces. The forces of [...]

We learn about the universe by looking at the heavens, which means our knowledge depends on the kinds of signals we see and the messengers that bring them to us. [...]

Cosmologists know the universe began with the Big Bang approximately 13.7 billion years ago. Astronomers know Earth formed from material in a debris disk surrounding the fledgling Sun. And planetary [...]

Q: How do astrophysicists measure a black hole's mass?--Kirt Bhatt, Columbia, Maryland A: If the black hole is sitting by itself out in space, you probably won't be able to [...]

Earth hasn't always been a green and pleasant place. In fact, our planet's infancy was a violent, chaotic time. When you visualize the hellish conditions back then, it's hard to [...]

Q: If nothing, not even light, can escape a black hole, then why do nearly all artist renderings of black holes show an accretion disk and a jet that appears [...]

Everything and everywhere began about 14 billion years ago in the Big Bang. Since then, a massive expansion of space-time has carried galaxies far away from each other. After American [...]

Sometimes the most profound insights come from the most mundane experiences. So it is with the discovery of the cosmic microwave background (CMB), which manifested itself as an engineering nuisance. [...]

Relativity has always been the odd man out in the sciences. In the general course of affairs, scientific ideas change slowly. Data challenging the old view starts to accumulate, then […]

It was born millions of years ago in a distant galaxy, accelerated to incredible speeds by a process unknown to science. For millennia it sped through the void, twisting and [...]

Imagine you are being given an important assignment by a taskmaster with a strange sense of humor. Your job is to study a forest, but you can only work according [...]

Everyone who lived before Christopher Columbus thought Earth was flat, right? Actually, Greek scientists knew Earth was a sphere thousands of years before Columbus first sailed the Atlantic. That knowledge [...]

Auguste Comte (1798-1857) is known today as an important philosopher and the father of modern sociology, but in his own lifetime he lived a shadowy kind of existence on the [...]

Most of us have a pretty good intuitive grasp of the way time affects our lives. Yet when it comes to defining the essence of time, most of us agree […]

Why is there a universe at all? How could everything we see around us have been created out of nothing? When you begin to think about how the universe began, [...]

If you look at the sky on a clear night, you can see a few thousand stars. With a telescope you can see a lot more - distant galaxies, gas [...]

Einstein's general theory of relativity remains our best explanation of the phenomenon of gravity, but it has accumulated a remarkably small number of experimental verifications. This is because Einstein's relativity [...]