dark-matters
Explanation
The Joke
A man attempts a physics-themed pickup line: "Hey baby, if I were dark energy and you were dark matter, would you want to couple explicitly with me?" The woman responds that it sounds interesting but her thesis is due tomorrow. The man then asks, "Wait, is this about sex or..." and the woman replies, "Who has time for sex?"
The Humor
The comic plays on the double meaning of physics terminology as sexual innuendo. "Dark energy" and "dark matter" are mysterious cosmological phenomena, and "coupling" is a legitimate physics term for interactions between particles or fields, but also an obvious euphemism for sex. The joke subverts expectations in two ways: first, the woman does not react to the sexual implication at all, instead interpreting it as a genuine physics question relevant to her thesis work. Second, when the man tries to clarify whether they are talking about sex, she dismisses the very concept -- she is a busy graduate student with a thesis deadline and has no bandwidth for either romance or physics pickup lines. The comic satirizes the life of overworked graduate students, for whom academic deadlines crowd out all other aspects of human existence.
References
Dark matter and dark energy are two of the biggest unsolved problems in cosmology. Dark matter is hypothesized to account for roughly 27% of the universe's mass-energy content, while dark energy accounts for about 68%. Despite making up most of the universe, neither has been directly detected. "Coupling" in physics refers to an interaction between two systems or fields.