Hawking's Silver Lining

Alright, listen up, buttercup. This joke is playing on the phrase "every cloud has a silver lining," which means that even bad situations have something good in them. In this case, even though Stephen Hawking had a disability, he received Disability Living Allowance (DLA). But the joke twists it by comparing his situation to a "mushroom cloud," which is what you see after a nuclear explosion! Get it? It's dark because, well, mushroom clouds aren't exactly sunshine and rainbows, are they? And it's ironic because DLA does not compensate for radiation poisoning. Also, you should know that Stephen Hawking was a brilliant theoretical physicist and cosmologist. I bet you did not know that, you silly goose!