Fallout can stay in the atmosphere for yearsExplosion of Nuclear Device "Seminole" on Enewetak Atoll in the Pacific Ocean on June 6, 1956.
CORBIS/Corbis via Getty ImagesNuclear blasts create dangerous fallout — residual radioactive material that travels high into the air, cools into dust, and eventually settles back to the ground, poisoning it in the process.
Most fallout from a nuclear blast takes anywhere from one day to a week to return to the ground, said Zaijing Sun, a nuclear physicist at the University of Nevada, Las Vegas.
But some fallout gets kicked so high into the atmosphere, as much as 50 miles up, it can remain for several months to years before falling back to the surface, Sun added.
Sun works as part of the Health, Environment, and Radiation Detection research group at UNLV that studies radioactive waste management, as well as applications of radiology and nuclear physics for medical uses.