Missing Matter in Universe Found

This study accounts for missing ordinary matter, not dark matter. The linked article makes this clear in the first paragraph. Sometimes I wonder if the first commenters (and often top commenters) on HN read the article at all or just respond based on the headline, because these comments often seem barely related to the actual article content.

Re: Missing Matter in Universe Found

#5

Post by jbotz » Fri, Jun 20, 2025, 4:48 AM UTC

philipov wrote: post #3

Does this remove the need for WIMPs and other exotic explanations for dark matter?

This has nothing to do with dark matter, it's about the missing baryonic matter. And this result just confirms what most people thought anyway, but it's still rather important because it's a very solid result so we don't need to call it "missing matter" anymore.

Re: Missing Matter in Universe Found

#6

Post by verisimi » Fri, Jun 20, 2025, 4:55 AM UTC

It was on the table under the dishcloth!

Re: Missing Matter in Universe Found

#7

Post by throwaway290 » Fri, Jun 20, 2025, 4:59 AM UTC

> The vast majority of matter in the universe is dark—it is entirely invisible and detected only through its gravitational effects

They state like dark matter is a fact. Isn't it a hypothesis?

> The FRBs shine through the fog of the intergalactic medium, and by precisely measuring how the light slows down, we can weigh that fog, even when it's too faint to see

Light slows down??

Re: Missing Matter in Universe Found

#8

Post by nxpnsv » Fri, Jun 20, 2025, 5:09 AM UTC

throwaway290 wrote: post #7

> The vast majority of matter in the universe is dark—it is entirely invisible and detected only through its gravitational effects They state like dark matter is a fact. Isn't it a hypothesis? > The FRBs shine through the fog of the intergalactic medium, and by precisely measuring how the light slows down, we can weigh that fog, even when it's too faint to see Light slows down??

1. It is a phenomenon not a hypothesis. Dark matter is a collection of observational facts that indicate an unknown source of gravity. 2. Yes, in any medium lights slows down. This is what refractive index measures.

Re: Missing Matter in Universe Found

#9

Post by pmontra » Fri, Jun 20, 2025, 5:09 AM UTC

throwaway290 wrote: post #7

> The vast majority of matter in the universe is dark—it is entirely invisible and detected only through its gravitational effects They state like dark matter is a fact. Isn't it a hypothesis? > The FRBs shine through the fog of the intergalactic medium, and by precisely measuring how the light slows down, we can weigh that fog, even when it's too faint to see Light slows down??

Light is always light and has always the same speed but its path in a gas is less straightforward than in a vacuum because of the interactions with atoms. It takes longer to get through. Its speed as we can measure it is c divided by the refractive index of the gas, if I'm not wrong.

Same thing for light in a liquid or in a solid. Example: speeds of radio waves in networking cables https://en.wikipedia.org/wiki/Velocity_factor#Typical_veloci...

Re: Missing Matter in Universe Found

#10

Post by nxpnsv » Fri, Jun 20, 2025, 5:09 AM UTC

philipov wrote: post #3

Does this remove the need for WIMPs and other exotic explanations for dark matter?

No.