Dark matter hasn’t been directly detected, but some form of invisible matter is clearly gravitating. Could the graviton hold the answer? — One of the most puzzling observations about the Universe is that there isn’t enough matter — at least, matter that we know of — to explain how we see things are gravitating. On Solar System scales, General Relativity and the masses we observe do the job just fine. But on…

A spherical structure nearly one billion light-years wide has been spotted in the nearby Universe, dating all the way back to the Big Bang. — If you were to look at the Universe on the absolute largest of cosmic scales, you’d find that galaxies clustered together in an enormous web of structure. Individual galaxies form along the threads of the web, with rich groups and clusters of galaxies forming at the nexuses where the threads…

The matter that creates black holes won’t be what comes out when they evaporate. Will the black hole information paradox ever be solved? — When something falls into a black hole, where does it go, and will it ever come back out again? According to Einstein’s General Relativity, those answers are simple: as soon as anything physical — matter, antimatter, radiation, etc. — crosses over the event horizon, it’s gone. It can add things…

In 1987, the closest supernova directly observed in nearly 400 years occurred. Will a pulsar will arise from those ashes? JWST offers clues. — In 1987, humanity observed the closest supernova since 1604.

Three fundamental forces matter inside an atom, but gravity is mind-bogglingly weak on those scales. Could extra dimensions explain why? — There’s a problem with gravity that no one is comfortable with, and that even physicists rarely talk about. If you take any two particles with a mass to them — like two electrons, two of the quarks within a proton or neutron, or even composite particles like two protons —…

Newton thought that gravitation would happen instantly, propagating at infinite speeds. Einstein showed otherwise; gravity isn’t instant. — When you look at the Sun, the light you’re seeing isn’t the light that’s being emitted right now. Instead, you’re seeing light that’s a little more than eight minutes old, since the Sun is some 150 million kilometers (93 million miles) away, and light — although it’s fast — can…

There are a few clues that the Universe isn’t completely adding up. Even so, the standard model of cosmology holds up stronger than ever. — One of the most exciting things that can happen to a scientist is the discovery of evidence that appears to contradict the predictions of the leading theories of your field. In some cases that you can imagine, the evidence would immediately be revolutionary. For particle physics, that would be like…

With ~400 billion stars in the Milky Way and 6–20 trillion galaxies overall, that makes for a lot of stars. But not as many as you’d think. — No matter where we look in space, in any direction, we see that the Universe is filled with stars and galaxies absolutely everywhere. As far as stars go, on a clear, dark night, the naked human eye can see about 6000 of them, but that’s just a tiny fraction of…

The biggest, brightest galaxies are the easiest to spot, but the tiniest ones teach us about how the Milky Way assembled and grew up! — When we look at our nearby Universe, it’s easy to recognize our own galaxy and the other large, massive ones that are nearby: Andromeda, the major galaxies in nearby groups like Bode’s Galaxy, the group of galaxies in Leo, and the huge galaxies at the cores of the Virgo and…