Is Dark Energy Just An Illusion, As Is Often Suggested?
A renewed suggestion that dark energy may not be real — dispensing with 70% of the stuff in the universe — has reignited a longstanding debate.
Dark energy and dark matter are theoretical inventions that explain observations we cannot otherwise understand.
On the scale of galaxies, gravity appears to be stronger than we can account for using only particles that are able to emit light. So we add dark matter particles as 25% of the mass-energy of the Universe. Such particles have never been directly detected.
On the larger scales on which the Universe is expanding, gravity appears weaker than expected in a universe containing only particles — whether ordinary or dark matter. So we add “dark energy”: a weak anti-gravity force that acts independently of matter…
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