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General Relativity
A recent paper in the journal Physical Review Letters claims to prove that a "kugelblitz" is not possible.
Straddling the bounds of science and religion, Newton wondered who set the planets in motion. Astrophysics reveals the answer.
Just 13.8 billion years after the hot Big Bang, we can see objects up to 46.1 billion light-years away. No, this doesn't violate relativity.
The Bullet Cluster has, for nearly 20 years, been hailed as an empirical "proof" of dark matter. Can their detractors explain it away?
The standard picture of our Universe is that it's dominated by dark matter and dark energy. But this alternative is also worth considering.
On the largest of cosmic scales, the Universe is expanding. But it isn't all-or-nothing everywhere, as "collapse" is also part of the story.
There are many things that separate science from ideology, politics, philosophy, or religion. Follow these 10 commandments to get it right.
Gravitational waves carry enormous amounts of energy, but spread out quickly once they leave the source. Could they ever create black holes?
Traveling back in time is a staple of science fiction movies. But according to Einstein, it's a physical possibility that's truly allowed.
From the coldest planets to spacecraft that have exited the Solar System, these little-known facts stump even many professional astronomers.
Is gravity weaker over distances of billions of light-years?
If you bring too much mass or energy together in one location, you'll inevitably create a black hole. So why didn't the Big Bang become one?
For nearly 25 years, we thought we knew how the Universe would end. Now, new measurements point to a profoundly different conclusion.
The mutual distance between well-separated galaxies increases with time as the Universe expands. What else expands, and what doesn't?
There are many theories of gravity out there, and many interpretations of wide binary star data. What have we really learned from it all?
The evidence that the Universe is expanding is overwhelming. But how? By stretching the existing space, or by creating new space itself?
Holograms preserve all of an object's 3D information, but on a 2D surface. Could the holographic Universe idea lead us to higher dimensions?
In general relativity, white holes are just as mathematically plausible as black holes. Black holes are real; what about white holes?
In the 20th century, many options abounded as to our cosmic origins. Today, only the Big Bang survives, thanks to this critical evidence.
The Universe is expanding, and the Hubble constant tells us how fast. But how can it be a constant if the expansion is accelerating?
Yes, the Universe is expanding, but if you've ever wondered, "How fast is it expanding," the answer isn't in terms of a speed at all.
Is the Universe finite or infinite? Does it go on forever or loop back on itself? Here's what would happen if you traveled forever.
The Universe is 13.8 billion years old, going back to the hot Big Bang. But was that truly the beginning, and is that truly its age?
The "first cause" problem may forever remain unsolved, as it doesn’t fit with the way we do science.
First derived by Emmy Noether, for every symmetry a theory possesses, there's an associated conserved quantity. Here's the profound link.
There are a wide variety of theoretical studies that call our Standard Model of cosmology into question. Here's what they really mean.
Physicists just can't leave an incomplete theory alone; they try to repair it. When nature is kind, it can lead to a major breakthrough.
Because of dark energy, distant objects speed away from us faster and faster as time goes on. How long before every galaxy is out of reach?
Symmetries aren't just about folding or rotating a piece of paper, but have a profound array of applications when it comes to physics.
The Multiverse fuels some of the 21st century's best fiction stories. But its supporting pillars are on extremely stable scientific footing.