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A Cosmic Mystery! Scientists Pick Up a Signal They Can’t Explain
Quick Summary
Deep underground in South Dakota, a giant science machine may have caught a tiny flash of something scientists have been hunting for nearly 100 years. The mysterious stuff is called dark matter. Researchers say they are excited — but they need more evidence before they can say for sure what they found.
What Happened?
Almost a mile below the surface, a remarkable detector sits inside an old gold mine. It is called LUX-ZEPLIN, or LZ for short. The machine is managed by Lawrence Berkeley National Laboratory and run by about 250 scientists from 39 institutions around the world.
LZ’s job is to search for dark matter — an invisible form of matter that scientists believe makes up about 85 percent of all the matter in the universe. Think of it this way: if all the matter in the universe were a pizza, dark matter would be the crust, the sauce, and most of the toppings. Ordinary matter — everything you can touch or see — would be just a couple of small bites.
For the search, the LZ detector uses 10 tonnes of ultra-pure liquid xenon. That is about the weight of two elephants of a very rare, heavy gas cooled into liquid form. When a passing particle bumps into a xenon atom, tiny flashes of light appear. Scientists use special cameras to catch those flashes.
Recently, researchers spotted one very unusual flash. It appeared exactly where dark matter would be expected to show up. It also did not match any ordinary background signal they know of.
“We’re very intrigued to see this event in the data, in the region where we expect dark matter to show up,” said Rick Gaitskell, a physics professor at Brown University and the spokesperson for the LZ experiment.
But scientists are being very careful. One flash is not enough to call it a discovery. In physics, scientists need to see a signal that is extremely strong — called a “five sigma” result — before they can claim they have truly found something new. This signal reached only 2.6 sigma, which is interesting but far from certain.
“With only one event, we don’t want to get ahead of ourselves. We are not claiming to have seen dark matter,” Gaitskell added. The results were shared at a major science conference in Japan.
Why Does It Matter?
Dark matter is one of the biggest mysteries in all of science. It holds galaxies together like invisible glue. Without it, stars and planets might fly apart into space. Scientists have been searching for it for decades with no luck — until this possible hint.
The LZ team plans to keep collecting data through 2028. If more flashes appear in the same spot, that would be a very strong sign that dark matter has finally been found. That would be one of the biggest science discoveries in all of human history.
Big Words
- Dark matter — an invisible material that scientists think makes up most of the matter in the universe, but that nobody has ever directly seen or caught.
- Detector — a machine built to notice very tiny events, like a single particle bumping into another particle.
- Xenon — a heavy, colorless gas that can be cooled into a liquid; the LZ machine uses it to catch signs of dark matter.
- Sigma — a number scientists use to measure how confident they are in a result; five sigma means a discovery is almost certainly real.
- Particle — a tiny piece of matter, far too small to see, that everything in the universe is made of.
Fun Fact
The LZ detector is buried nearly a mile underground on purpose! All that rock acts like a shield, blocking out cosmic rays and other particles that could accidentally look like dark matter and confuse the experiment.
Think About It
If dark matter is invisible and we can’t touch it, how do you think scientists figured out it must exist in the first place?
Sources
- Stanford University — Scientists spot a possible dark matter signal
- Berkeley Lab News Center — LZ Sees Surprising Result in Search for Dark Matter
- Imperial College London — Dark matter hunt takes unexpected turn after puzzling signal spotted in LZ detector
- ABC News (Australia) — ‘Exciting hint’ of dark matter spotted by LUX-ZEPLIN detector
- Brown University — LZ experiment sees surprising result in search for dark matter