the.com/dark energy

means The mysterious force physicists invoke to explain why the universe's expansion is speeding up instead of slowing down under gravity's pull.

from A 20th-century scientific coinage, not a borrowing from myth or old language. 'Energy' traces back to Greek 'energeia,' meaning activity or operation. 'Dark' here means simply unseen and undetected — not sinister, just invisible to every instrument pointed at it. The term itself emerged after astronomers, measuring distant exploding stars called supernovae, found the universe's expansion accelerating rather than coasting or slowing. Needing a name for whatever was pushing space apart, scientists reached for 'dark' by analogy with 'dark matter' — another invisible placeholder — and so christened the unknown with a label that admits, honestly, how little is known.