Almost a century ago, Edwin Hubble noticed that galaxies are receding — the Universe is expanding. Today, two methods of measuring the expansion rate yield differing results: using the afterglow of the Big Bang and supernova explosions, whose brightness and color shifts are meticulously measured. The 8% discrepancy — the Hubble tension — had long baffled scientists until an unexpected solution emerged.

It turns out that a photon wandering through space for billions of years can freeze out into dark matter particles — as if quantum tunneling through an invisible barrier. Astronomers have always corrected for the dimming of light, but they missed the accompanying redshift. This mistake created the illusion that supernovae are closer and the Universe is expanding faster. Accounting for this effect removes the contradiction and also explains why JWST observed overly massive early galaxies — they are actually lighter — and why invisible lenses bend light. The time dilation of distant objects is also not violated. A test is near: a laser beam sent to the edge of the Solar System will lose a billionth of its energy — ultraprecise clocks will detect it. If so, we will realize that dark matter is a 'sediment' of light, and more of it has accumulated than visible stars and planets.