Gravity. It's the law.

jtotheizzoe:

It turns out that exploding bubbles of hydrogen filmed at 16,000 frames per second are one of the coolest things on Earth. 

This is part of a study of the fluid dynamics of various explosive mixtures of hydrogen and air. The video talks a lot about the idea of “buoyancy”, which for flames and explosions relates to their ability to push out and displace the air around them, use up all the available fuel, etc.

Of course, if you’re not into the science side of it, just skip ahead in the video to about 1:20 and then pick your jaw up off the floor.

As per PhysicsPhysics recommendation, immediately stop what you are doing, and watch this video in 1080p in full screen. We promise you will have no regrets!