Greetings Astronomers,

This may be an old subject but could you help me understand. Does this article suggests that dark matter is no longer dark? This article suggests that the baryonic gas found among the intergalactic medium--the space between galaxies--comprises 79% of our universe's missing matter. Am I reading that article correctly?

17 minutes ago, DrmDoc said:

Greetings Astronomers,

This may be an old subject but could you help me understand. Does this article suggests that dark matter is no longer dark? This article suggests that the baryonic gas found among the intergalactic medium--the space between galaxies--comprises 79% of our universe's missing matter. Am I reading that article correctly?

I think I can help you understand it. For years, scientists knew that a large portion of the universe's normal matter was missing, we are not talking about dark matter, just the regular stuff that makes up stars, planets, and people. Based on what we know from the Big Bang, there should be more of this matter than we could actually find. Recently, astronomers solved this mystery using something called fast radio bursts, which are brief, powerful signals from distant galaxies. As these signals travel through space, they interact with matter and get slightly changed. By studying how the signals were affected, scientists realized that most of the missing matter is spread out as thin gas between galaxies, not gathered in stars or galaxies like we expected. So the matter was always there it was just really hard to detect until now.

It’s known as the missing baryon problem, which is distinct from dark matter

https://en.m.wikipedia.org/wiki/Missing_baryon_problem

I understood dark matter to be that undetectible matter whose gravitational effects are not explained by visible matter. If I now understand correctly, baryons are not that invisible matter? Just missing protons? Forgive my ignorance but aren't protons matter?

2 minutes ago, DrmDoc said:

I understood dark matter to be that undetectible matter whose gravitational effects are not explained by visible matter. If I now understand correctly, baryons are not that invisible matter? Just missing protons? Forgive my ignorance but aren't protons matter?

Baryonic matter makes up much of what we call “normal” matter - neutrons and protons. Dark matter is thought to (mostly) be not baryonic, since it doesn’t interact as baryons do

1 minute ago, swansont said:

Baryonic matter makes up much of what we call “normal” matter - neutrons and protons. Dark matter is thought to (mostly) be not baryonic, since it doesn’t interact as baryons do

Oh, I see. That article was just click bait for science readers. Thanks to you both, Swansont and Sohan!

49 minutes ago, DrmDoc said:

Oh, I see. That article was just click bait for science readers. Thanks to you both, Swansont and Sohan!

Anytime my friend!

Mr. DrmDoc ,

You are correct in that that article APPEARS to conflate/mangle the percentage for Dark-Energy in the Universe . Even if it means ONLY baryonic-matter , it is confusing .

Now about that surprise ; it is one because no one had a theory proposing such . However , there is a possible explanation . The energetic components of the Universe have always emitted enormous quantities of particle radiation . These start out moving at extremely high speeds , but slow down over great stretches of time . Eventually , they "cool down" and become the sea of atomic particles (gas) observed by astronomers .

8 minutes ago, Professor-M said:

Mr. DrmDoc ,

You are correct in that that article APPEARS to conflate/mangle the percentage for Dark-Energy in the Universe . Even if it means ONLY baryonic-matter , it is confusing .

Now about that surprise ; it is one because no one had a theory proposing such . However , there is a possible explanation . The energetic components of the Universe have always emitted enormous quantities of particle radiation . These start out moving at extremely high speeds , but slow down over great stretches of time . Eventually , they "cool down" and become the sea of atomic particles (gas) observed by astronomers .

What makes them slow down?

And what prevents them from being detected?

Also, saying nobody has proposed some explanation discounts the likely scenario where it was thought of and almost immediately discarded because it was flawed, so it never got exposure.

From https://en.wikipedia.org/wiki/Greisen%E2%80%93Zatsepin%E2%80%93Kuzmin_limit

"The Greisen–Zatsepin–Kuzmin limit (GZK limit or GZK cutoff) is a theoretical upper limit on the energy of cosmic ray protons traveling from other galaxies through the intergalactic medium to our galaxy. The limit is 5×10¹⁹ eV (50 EeV), or about 8 joules (the energy of a proton travelling at ≈ 99.99999999999999999998% the speed of light). The limit is set by the slowing effect of interactions of the protons with the microwave background radiation over long distances (≈ 160 million light-years)."

🤓 Physics-Fans !

Though rare , over great stretches of time relativistic particles will eventually collide with other particles .

A good example of the above process is cosmic-rays entering the Solar-System and colliding with solar-wind particles . This slows down and seriously mitigates the severity of said cosmic-rays .

*It is indeed possible that someone previously thought of the idea presented by me above ; I just never heard of it before , so... figure of speech .

Edited July 27Jul 27 by Professor-M

2 minutes ago, Professor-M said:

🤓 Physics-Fans !

Though rare , over great stretches of time relativistic particles will eventually collide with other particles .

A good example of the above process is cosmic-rays entering the Solar-System and colliding with solar-wind particles . This slows down and seriously mitigates the severity of said cosmic-rays .

We detect such particles, and I'd like a source that says it’s the solar wind vs our own atmosphere that shields us, but also an explanation of how this supposedly answers the questions you were asked.

Hallo again !

Although my commentary is primarily aimed at addressing the Thread Title , I will elucidate about those two questions :

"What prevents the particles from being detected ?" , and "What makes them slow down ?" .

The former is a non sequitur , as they already HAVE been detected . The latter is answered effectively above as regards particle collisions . I will add that the Universe’s expansion apparently adds to the cool-down much as expanding a volume of gas cools IT down .

Now in regards to your Solar-Wind versus atmosphere question : they BOTH mitigate cosmic-rays , with the atmosphere being the more effective of the two . I am confident that you are capable of searching up "Cosmic-ray attenuation" , but I will shortly add a link anyway .

nasa.com/cosmic-rays-vs-solar-wind

*Use "Inquiries" Link at bottom of page .

Edited July 27Jul 27 by Professor-M

Cosmo-Folk (and Doctors) ,

There is another possible source of invisible mass in deep interstellar space , this being gravity-waves .

Although we have begun to measure and use gravity-waves to evaluate very distant cosmic phenomena , there has so far been minimal appreciation of the existence and effects of attenuated and primordial gravity-waves upon the Universe and it's contents .

These G-Ws are unimaginably diluted by distance , and thus weak in energy-content . However, 13.8-billion years of their constant generation have doubtless soaked the cosmos with an endless ocean of them . The total virtual (relativistic) mass of this abundance of putative gravitons must actually be a cosmically significant amount, likely being a large portion of the missing "mass-energy" addressed up above .

*Reference Article below :

Premium

Colossal gravitational waves—trillions of miles long—foun...

Detected by studying rapidly spinning dead stars, these giant ripples of spacetime likely came from merging supermassive black holes—and they may reveal clues about the nature of the universe.

Edited July 31Jul 31 by Professor-M
Referencing .

On 7/27/2025 at 9:39 AM, Professor-M said:

Hallo again !

Although my commentary is primarily aimed at addressing the Thread Title , I will elucidate about those two questions :

"What prevents the particles from being detected ?" , and "What makes them slow down ?" .

The former is a non sequitur , as they already HAVE been detected . The latter is answered effectively above as regards particle collisions . I will add that the Universe’s expansion apparently adds to the cool-down much as expanding a volume of gas cools IT down .

If we can easily detect them why was the article a revelation about finding missing matter? Missing implies not detected.

Yes Doctor , but...

We can detect their gravitational effects , so... from what ? 🤔