On a high-speed highway, a steady flow of cars sometimes clumps into a traffic jam because of random slowdowns. In the young Universe, the overall expansion of galaxies after the Big Bang resembled this orderly movement. But each galaxy also performed its own maneuvers — braking or accelerating under the pull of neighboring galaxies. These wanderings acted like local traffic jams: where galaxies drew closer, clouds of dark matter and gas clumped together faster, speeding up the birth of giant star systems. Previously, cosmologists overlooked such maneuvers, but data from the James Webb Space Telescope revealed their decisive role in the early Universe. Accounting for these deviations within the framework of relativity and the standard model fully explains the mystery of massive baby galaxies. And most unexpectedly, these tiny irregularities in motion, once dismissed as noise, turned out to be the key, sparing scientists the need to invent new physics.
The peculiar motions of some galaxies accelerate them to 1000 km/s — dozens of times faster than the overall expansion of the Universe at those same distances.