This is a lesson taught in british sign language, a language that until recently was missing crucial scientific vocabulary. at this secondary school in glasgow, deaf children are learning newly created signs that have just been added to the bsl dictionary. so this is a sign for greenhouse gases — and that's a new one, i didn't know that one before. so in physics, for example, some of the concepts are really abstract, and sign language can help children understand, because it's a visual language. so this is a sign for photosynthesis. so here we have a leaf. and this is the sun. it's light ene...