The Beirut explosion created a huge mushroom cloud and visible blast wave, but nuclear weapons experts say it wasn't an atomic blast. Here's why.

· A explosion at a port rocked the Lebanese capital city of Beirut on Tuesday, killing at least dozens of people.
· As videos of the explosion spread across social media sites, some users claimed an atomic bomb caused the disaster due to the appearance of a mushroom cloud.
· The Lebanese prime minister says the blast came...