To ask if a beam of light can make a shadow sounds like a sort of Zen paradox, but physicists have demonstrated the possibility. They used a laser beam to block another laser beam, albeit with some ...

Neutrino lasers: It’s an idea that many physicists didn’t see coming. At first glance, physics suggests that it would be impossible to make a laser of neutrinos, famously elusive subatomic particles.

When the green laser encounters atoms along its path through the crystal, it gives the electrons in those atoms a bit of extra energy. In their high-energy state, those electrons can absorb blue light ...