Katherine Freese, a theoretical astrophysicist at The University of Texas at Austin, answered questions about dark matter ahead of Dark Matter Day on Oct. 31. UT News reported that ordinary matter, the stuff that makes up stars, planets and people, accounts for only about 5% of the universe's total matter. According to the report, about 25% is dark matter and the remaining 70% is dark energy.
Freese said gravity works on both ordinary matter and dark matter in the usual way. She said dark energy is causing the universe's expansion to speed up, and that scientists do not yet understand where it comes from. The report said the dark matter question dates to the 1930s, when scientists observed the motion of galaxies in a cluster.
The report said the underground LUX-ZEPLIN experiment recently recorded a possible detection of dark matter, a single particle interaction that scientists find hard to explain. Scott Kravitz, an assistant professor of physics at UT, served as the experiment's analysis coordinator during most of the search. The report said the finding is not enough to claim a discovery.