The biggest particle accelerator in the *universe*… is made of galaxies.

Nature writes so calmly about shockwaves of such epic proportions:

Four massive clusters of galaxies are plowing into one another at a crash site about five billion light-years from Earth. The conglomeration is creating one giant concentration of thousands of galaxies. “This is really one of the most massive clusters we know of and one of the most complex mergers we know of,” said Reinout van Weeren of the Harvard–Smithsonian Center for Astrophysics (CfA) in Boston, Massachusetts….

Such naturally arising particle accelerators have been observed before, most commonly in the remnants of supernovae. But MACS J0717+3745 may turn out to be one of the most powerful particle accelerators known. The observations suggest the particles there are reaching energies up to a million times those in Earth-bound atom smashers, such as the Large Hadron Collider in Switzerland.