Many forget that a meme is simply a concept or idea that grabs hold within a human community and is propagated and promulgated. Patriarchy is a meme. Capitalism is a meme. Doing ‘bunny ears’ behind someone’s head in a photo is a meme (h/t Parker and Stone). Doing cave paintings of animals is a meme. Fashion of an era is a meme. Our entire social structure runs on memes.
We were taught a similar trick in physics - point your right-hand thumb in the direction that current (or electrons, same same) is travelling and the curling of your fingers shows the direction of the resultant magnetic field that the current creates.