Does a radioactive cat have 18 half-lives? Have you heard that entropy isn't what it used to be? If you're not laughing, then you're either scratching your head, trying desperately to remember your high school chemistry class, or rolling your eyes at these low-brow attempts at scientific humor. Memes, which are a little more complicated than straight word jokes because they use imagery as well, can still be pretty stupid sometimes. But when the subject is science, they can be pretty smart - too smart, maybe.
As this list will likely show, unless you do science for a living, or study it, or have Einstein-ian tendencies, scientific memes sometimes take a few seconds to figure out. Or a few minutes, or hours, depending on how fast your Google search skills are.
You get an A for effort just for reading through all these; bonus points if you can figure out what they all mean without any extra research. If they're too baffling, but you still want to show off your education, you can always go for history memes instead.