Modified Gravity Could Soon Be Ruled Out, Says New Research On Dwarf Galaxies
Dark matter is our leading theory for a reason. New, detailed studies of the smallest galaxies could kill off the most studied alternative.
When you look out at the Universe, there are a few things you’d rationally expect. You’d expect that the same things that made up everything we saw — like atoms and light — made up everything there was. You’d expect that the fundamental laws would apply equally well everywhere you looked, from small scales to large scales. And you’d expect that if you had multiple ways of measuring the same physical quantity, they’d give you the same answer.
Which is why the dark matter problem is such a puzzle. There are a huge variety of measurements we can make that indicate that about 5/6ths of the Universe, by mass, isn’t made up of any of the known particles. It doesn’t interact with normal matter or light. And if you measure the mass of a galaxy directly, from its light, it doesn’t match the mass you infer from gravity.