The latest attempt to rattle the foundations of cosmology appeared as a smattering of dots pulled upward into a cosmic sneer. The arc of distant galaxies, which Alexia Lopez presented at the American Astronomical Society’s meeting in June, sprawls so far across the sky that it would take 20 full moons to hide it. Spanning an estimated 3.3 billion light-years of space, the smile-shaped structure joined a controversial club: unexpectedly big things.
“It’s so big that it’s hard to explain with our current beliefs,” Lopez, one of the astrophysicists at the University of Central Lancashire who identified the galaxy chain, said during the presentation.
Lopez’s “Giant Arc” seemed to clash with an idea that has guided astronomy for centuries: that the universe has no conspicuous features. From a zoomed-out perspective, no matter where you are or which way you look, you should see roughly the same number of galaxies pinwheeling around.
This assumption, enshrined as the “cosmological principle,” has let researchers draw sweeping conclusions about the whole universe based only on what we see from our corner of it.
“If that turns out to be wrong, then we have to redo many of our measurements or reinterpret many of our measurements,” said Ruth Durrer, a cosmologist at the University of Geneva.
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