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General Relativity
Particles are everywhere, including particles from space that stream through the human body. Here's how they prove Einstein's relativity.
From white holes to dark stars and multiverses, James Riordon explores the bizarre exhibits of general relativity's "cryptozoo."
We first measured G, the gravitational constant, back in the 18th century. As the least well-known fundamental constant, can it be improved?
In 2017, a kilonova sent light and gravitational waves across the Universe. Here on Earth, there was a 1.7 second signal arrival delay. Why?
16mins
“The messy reality of it is that all of these very smart people, including Isaac Newton, were talking to other people.”
The planet, the Solar System, and the galaxy aren't expanding. But the whole Universe is. So where does the dividing line begin?
We've long known we can't go back to infinite temperatures and densities. But the hottest part of the hot Big Bang remains a cosmic mystery.
Observations with the Hubble space telescope helped cement dark energy and reveal the Hubble tension. How are these two things so different?
Inflation's two main criticisms, that it can predict anything and that the "measure problem" remains unsolved, can't erase its successes.
As the Universe ages, it continues to gravitate, form stars, and expand. And yet, all this will someday end. Do we finally understand how?
23mins
"Could black holes be the key to a quantum theory of gravity, a deeper theory of how reality, of how space and time works? Well, I think so."
If you think of the Big Bang as an explosion, we can trace it back to a single point-of-origin. But what if it happened everywhere at once?
The hot Big Bang is often touted as the beginning of the Universe. But there's one piece of evidence we can't ignore that shows otherwise.
As we gain new knowledge, our scientific picture of how the Universe works must evolve. This is a feature of the Big Bang, not a bug.
10 years ago, LIGO first began directly detecting gravitational waves. Now better than ever, it's revealing previously unreachable features.
It's the origin of our entire observable Universe, but it's still not the very beginning of everything.
The Holy Grail of physics is a Theory of Everything: where a single equation describes the whole Universe. But maybe there simply isn't one?
Since even before Einstein, physicists have sought a theory of everything to explain the Universe. Can positive geometry lead us there?
The Universe isn't just expanding; the expansion is accelerating. If different methods yield incompatible results, is dark energy evolving?
When you don't have enough clues to bring your detective story to a close, you should expect that your educated guesses will all be wrong.
10 years ago, LIGO saw its first gravitational wave. After 218 detections, our view of black holes has changed forever. Can this era endure?
1hr 26mins
“I like to say that physics is hard because physics is easy, by which I mean we actually think about physics as students.”
Throughout history, "free energy" has been a scammer's game, such as perpetual motion. But with zero-point energy, is it actually possible?
Just 13.8 billion years after the hot Big Bang, we can see 46.1 billion light-years away in all directions. Doesn't that violate...something?
Einstein is credited with saying, "If the facts don't fit the theory, change the facts." What he actually said has a very different meaning.
Two supermassive black holes on an inevitable death spiral push the limits of Einstein's relativity. New observations reveal even more.
Once you cross a black hole's event horizon, there's no going back. But inside, could creating a singularity give birth to a new Universe?
From high school through the professional ranks, physicists still take incredible lessons away from Newton's second law.
With over 300 high-significance gravitational wave detections, we now have a huge unsolved puzzle. Will we invest in finding the solution?
1hr 18mins
“Could black holes be the key to a quantum theory of gravity, a deeper theory of how reality, of how space and time works?”