Readers discuss dark energy, Ötzi’s tattoos and sneaky plant invasions

Secrets of space

New data hint that dark energy’s density, commonly thought to remain constant, might vary over time, Emily Conover reported in “3-D map hints at dark energy’s secrets” (SN: 5/4/24 & 5/18/24, p. 6).

In the standard picture of the cosmos, the amount of dark energy is increasing as the universe expands. Reader Mark Granville wondered where new dark energy comes from.

Dark energy’s source is an enduring mystery. Quantum fluctuations in empty space, in which particles pop into existence for extremely brief moments, could be one explanation, Conover says. But these fluctuations yield even more questions.