"Even though Earth is floating in the void, it does not exist in a vacuum. The planet is constantly bombarded by stuff from space, including a daily deluge of micrometeorites and a shower of radiation from the sun and more-distant stars. Sometimes, things from space can maim or kill us, like the gargantuan asteroid that wiped out the dinosaurs. More often, stellar smithereens make their way to Earth and the moon and then peacefully settle, remaining for eternity, or at least until scientists dig them up.
Dark matter, if it exists, is probably in the latter category. If hypothetical weakly interacting massive particles (WIMPs) are real, their collisions with regular matter may have left fossil traces in the depths of the planet’s rock record. A team of physicists has proposed a new way to look for such fossil tracks as a way of hunting for dark matter, as I reported earlier this month.
But the search for cosmic debris on Earth has a long history. Other researchers have demonstrated that it’s possible to find fossil evidence of astrophysical particles in Earth’s crust. Some researchers are pondering how these cosmic events affect Earth — even whether they have altered the course of evolution. A new study suggests that energetic particles from an exploding star may have contributed to the extinction of a number of megafauna, including the prehistoric monster shark megalodon, which went extinct at around the same time."
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