Neutron stars, when they merge, should create an electromagnetic counterpart if they don’t create a black hole right away, as light and particles will be expelled due to internal reactions in the interior of these objects. However, if a black hole forms directly, the lack of an outward force and pressure could cause total collapse, where no light or matter escapes at all to the outside observers in the Universe. (DANA BERRY / SKYWORKS DIGITAL, INC.)

Merging Neutron Stars Really Can Solve Cosmology’s Biggest Conundrum

With just a few more neutron star mergers, we’ll have the best constraints of all-time.

How fast is the Universe expanding? Ever since the expanding Universe was first discovered nearly 100 years ago, it’s been one of the biggest questions plaguing cosmology. If you can measure how fast the Universe is expanding right now, as well as how the expansion rate is changing over time, you can figure out everything you’d want to know about the Universe as a whole. This includes questions like:

• What is the Universe made of?
• How long has it been since the hot Big Bang first took place?
• What is the Universe’s ultimate fate?
• Does General Relativity always govern the Universe, or do we need a different theory of gravity on large, cosmic scales?

We’ve learned a lot about our Universe over the years, but one enormous question is still in doubt. When we try to measure the expansion rate of the Universe, different methods of measuring it yield different results. One set of observations is about 9% lower than the other set, and no one has been able to figure out why. With a completely independent test that isn’t subject to any of the biases of the other methods…