This, is a fact.
Well, unless you're an anaerobic type of beasty in which case Oxygen is very much not your friend.
Yeast, is aerobic. The reaction which happens in brewing to get from natural barley sugars to alcohol is...
Sugar (from barley) + Oxygen + Yeasty beasties → Alcohol + Carbon dioxide (beery bubbles) + lots more Yeast
When we brewed the first two batches of Welbeck beer, there was a huge and very dense foam on the top after pumping the wort in to the fermenting vessel. I think this is mainly due to pumping lots of oxygen into the wort during the transfer, so for the third beer we pumped in far less oxygen. We aimed for about 15-20 minutes of oxygenation, because if there isn't any in it, we don't get any fermentation.
We brewed it Thursday
On Friday, no fermentation. But this is quite normal. It's called a 'lag' phase where the yeasty cells are getting used to it's new surroundings.
On Saturday I was expecting it to have gone bonkers. Alas, no fermentation. Eek! I went though all the possible causes of no fermentation, and decided that a lack of oxygen could be the only cause.
Sterilise a long ol' bit of air hose and pump oxygen into the beer for about half an hour. I stood up a ladder holding this daft bit of hose in the beer. It was a bit like blowing bubbles in your milk as a kid, I expected to hear my mother say 'don't do that!'. Oh then I realised, it was 8am on a Saturday morning and everyone else had better things to do!
Whoopee! Came in on Sunday, and after spending Saturday grumbling to my friend Ali about crappy beer and crappy yeast and crappy job, it was foaming all over the floor! I, am technical genius. I awarded myself bonus points for fixing the beer. I have yet to decide what bonus points earn me but, for now, I shall just say homemade Elderflower cordial with tonic. And gin. Lots of gin.
Enjoy the sunshine, and appreciate that pint.