Sean Carroll is a theoretical physicist at the California Institute of Technology. He specialises in quantum mechanics, gravitation, cosmology, statistical mechanics and foundations of physics. His latest book is Something Deeply Hidden: Quantum Worlds and the Emergence of Spacetime (2019). He lives in Los Angeles.
2,600 words.
If you were to travel back in time to kill your grandparents — let’s ignore the ‘why’ here, for the sake of argument — you would never have been born. Which means there was nobody to kill your grandparents. Which means you were actually born after all, which… hold up, what’s going on here?!
These kinds of brain-breaking paradoxes have been puzzling us forever, inspiring stories ranging from “Back to the Future” to “Hot Tub Time Machine.”
Now, New Scientist reports that physicists Barak Shoshany and Jacob Hauser from the Perimeter Institute in Canada have come up with an apparent solution to these types of paradoxes that requires a very large — but not necessarily infinite — number of parallel universes.
Scientists thought the case of the cosmic rays’ source was closed, but new evidence cracks it wide open again.
Our home galaxy has a new, super-precise mass measurement: about 890 billion times the mass of our sun. That’s 3.9 tredecillion lbs. (1.8 tredecillion kilograms), a tredecillion being a 1 with 42 zeros after it, or 1,000,000,000,000,000,000,000,000,000,000,000,000,000,000. That amounts to about 6 billion billion billion elephants, 296 quadrillion Earth masses or 135 times the mass of the supermassive black hole in the image released back in April.
Measuring the Milky Way’s mass presents some unusual difficulties, because we live in it. There’s no way to stick galaxies on scales, so researchers typically “weigh” galaxies by tracing the movements of stars inside the galaxies, which can reveal how the galaxy’s gravity is influencing those stars. But while anyone with a reasonably good telescope can spot the full Andromeda galaxy, most of the body of the Milky Way is hidden from us.
MIT physicists are reigniting the possibility, which they previously had snuffed out, that a bright burst of gamma rays at the center of our galaxy may be the result of dark matter after all.
For years, physicists have known of a mysterious surplus of energy at the Milky Way’s center, in the form of gamma rays—the most energetic waves in the electromagnetic spectrum. These rays are typically produced by the hottest, most extreme objects in the universe, such as supernovae and pulsars.
Gamma rays are found across the disk of the Milky Way, and for the most part physicists understand their sources. But there is a glow of gamma rays at the Milky Way’s center, known as the galactic center excess, or GCE, with properties that are difficult for physicists to explain given what they know about the distribution of stars and gas in the galaxy.
Crisis on Infinite Earths was seeing the destruction of the Multiverse — but there have been hints that it could be reversed in the end.
Posted in cosmology, entertainment
These could definitely exist and their fuel is everywhere.
The dark-matter engines are engines created by Professor Farnsworth for the Planet Express ship. Fueled by dark matter, the engines allow the ship to travel vast distances very quickly by moving the universe around the ship (rather than the ship around the universe). The Professor also has an emergency engine, though he may have pawned it. As of Bender’s Game these have been converted to use whale oil.
A team of scientists in Hungary recently published a paper that hints at the existence of a previously unknown subatomic particle. The team first reported finding traces of the particle in 2016, and they now report more traces in a different experiment.
If the results are confirmed, the so-called X17 particle could help to explain dark matter, the mysterious substance scientists believe accounts for more than 80% of the mass in the universe. It may be the carrier of a “fifth force” beyond the four accounted for in the standard model of physics (gravity, electromagnetism, the weak nuclear force and the strong nuclear force).
The hot Big Bang occurred 13.8 billion years ago, and there’s no other possible answer consistent with what we know today.
