Can someone explain the science of dry hopping to me?

[TorMag]

I've just brewed my first IPA and have moved into the dry hopping part of the process. I was just thinking about it this morning and was wondering "does dry hopping actually do anything?"

I know, don't shoot me. But seriously, there is no circulation within the fermentation "tank", no stirring. The hops just sits there in a bag. How does it get into all the beer?

I get the beer around the bag gets hop impregnated, but how about the stuff away from the bag?

Noob minds want to know.

 

[didinho]

I guess is the chemical concept of diffusion:
https://en.wikipedia.org/wiki/Diffusion
Particles randomly move, and the final result would be have an equal distribution in all solution

 

[TorMag]

Wow, pulled that one right out of the air, but makes complete sense. I skipped taking a chemistry class.

 

[Talgrath]

Think of it like iced tea. In case you've never made iced tea, it looks something like this when you first add the tea:

Even though you don't see the water flowing, there are small eddies and flows within the liquid, remember that temperature circulation occurs at all times in the system. So as liquid cools, it falls downward, while liquid heating up will rise.