The dark matter hypothesis isn't perfect, but the alternatives are worse - Space.com

You may not be a fan of dark matter, the hypothetical particle that makes up the bulk of the mass in the universe.

And it's true that the dark matter hypothesis has its shortcomings — and, of course, we haven't found any dark matter particles yet.

The best hypothesis scientists have to explain all of these disparate observations is that there is a new kind of particle, known as dark matter, that inhabits the cosmos.

This idea isn't as far-fetched as it seems; neutrinos are particles with exactly these properties.

They don't have enough mass to explain the dark matter, but they do show that such particles can exist.

But the dark matter hypothesis isn't perfect.

Also, simulations of dark matter evolving in the universe predict that every galaxy should have hundreds of smaller satellites, while observations consistently come up short.

Given that the dark matter hypothesis isn't perfect — and that we have no direct evidence for the existence of any candidate particles — it's worth exploring other options.

One such option was introduced back in the 1970s alongside the original dark matter idea, when astronomer Vera Rubin first discovered the problem of stars moving too quickly inside galaxies.

But instead of adding a new ingredient to the universe, the alternative changes the recipe by altering how gravity works at galactic scales.

Models based on modified gravity have significant trouble explaining the growth of structure in the universe, features of the cosmic microwave background and more — all places where dark matter works quite well.

While MOND may still be accurate when it comes to galaxy rotation curves, there are enough observations to tell us that we would still need dark matter to exist in the universe.

No, the dark matter hypothesis isn't perfect.

That doesn't make MOND wrong, but it does make it a far weaker alternative to dark matter.