What’s the matter?
The proposed Windchime experiment plans to make use of solely gravity to detect some varieties of darkish matter. Ultrasensitive sensors can be jostled by the gravitational forces of a darkish matter “wind” passing by Earth, James R. Riordon reported in “Gravity could aid dark matter search” (SN: 9/10/22, p. 14).
Since darkish matter is affected by gravity, reader David Goldberg requested if darkish matter orbits the Milky Way’s heart identical to our photo voltaic system does. If the 2 transfer collectively, how would there be a darkish matter wind to detect?
It’s potential that darkish matter circles the Milky Way’s heart a minimum of slightly, although it’s onerous to say for positive as a result of nobody has been capable of measure the elusive stuff but, Riordon says. But to seek for darkish matter utilizing the Windchime technique, it doesn’t actually matter whether or not the mysterious substance strikes with the galaxy, he says. That’s as a result of because the solar circles the Milky Way’s heart, Earth can be orbiting the solar. Even if the solar occurs to maneuver with the identical velocity as close by darkish matter, the course of Earth’s velocity modifications over the course of a yr, Riordon says. So we should always sense the pull of a darkish matter wind that shifts with Earth’s seasons.
What’s extra, because the planet spins on its axis, the course of the floor’s motion relative to the galaxy modifications all through the day. “It’s a little like a fish swimming in the ocean,” Riordon says. “Even though the water in general moves with Earth, as a fish swims in various directions, the creature will experience a flow of water relative to its own motion.”
Reader Jack Ryan questioned why, regardless of its gravitational attraction, darkish matter doesn’t kind stars, planets and different celestial our bodies.
“Because no one knows what dark matter is, we can’t say for certain that it can or cannot form globs or come in very massive particles,” Riordon says. “It’s something that researchers like those on the Windchime team are looking out for.”
For regular matter to create asteroids or planets, it should expertise some power past gravity, Riordon says. For occasion, if two rocks collide in area, electromagnetic forces would stop them from merely passing via one another. This would then enable gravity to carry the 2 rocks collectively. And if the focus of matter continues to construct up, then an asteroid or a planet might finally kind.
Some physicists hope that darkish matter experiences different forces, however gravity is at present the one one recognized to have an effect on it. “If a dark matter particle that only experiences gravity approaches a rock, a planet or another dark matter particle, it would glide right through because there is no force that can stop it,” Riordon says. “Gravity can pull dark matter into a halo, but on its own, it probably can’t stick dark matter together.”
Correction
A line dropped from our function “Island lessons” (SN: 9/24/22, p. 22). At the tip of Page 26, the total sentence ought to have learn: Saban native Dahlia Hassell-Knijff received a level in biology in Mississippi, then returned to the island, the place she oversees initiatives on the regional Dutch Caribbean Nature Alliance.
