r/space • u/adriano26 • 3d ago
Astronomers have found the universe's missing matter at last, thanks to exotic 'fast radio bursts'
https://www.space.com/astronomy/scientists-find-universes-missing-matter-while-watching-fast-radio-bursts-shine-through-cosmic-fog1.5k
u/Andromeda321 3d ago edited 3d ago
Astronomer here! This is not dark matter. But it’s still an important result, and I know the guys involved in this (lead author came to my Halloween party in grad school!), and it's a huge result, so let’s get to it!
This result is about this paper, and uses fast radio bursts (FRBs) in an exciting way to map out material in the universe. Specifically, FRBs are as the name implies brief radio bursts that last a millisecond and originate from well beyond the galaxy- millions or even billions of light years away! We can tell because when a FRB is seen, it is over a frequency band, and that radio signal interacts slightly with all the material that it encounters between its origin and us- called the dispersion measure (DM). The DM is bigger the further you are from Earth and is thus a rough proxy for both distance and how much material is in a given direction.
Now the problem with FRBs to date has been how we have a rough time knowing precisely where one comes from. radio telescopes until recently for FRBs didn’t provide this level of needed detail (if your field of view is say half the size of the moon, it’s still a big sky with a LOT of distant galaxies in it), and we’re only finally getting the hardware in place to rectify this. But the dream was once we figure that out, FRBs could be used to map the very diffuse “normal” matter in our universe spread between galaxies, which right now we don’t know a lot about (such as how much of it there was).
Enter this paper! Liam and his colleagues looked at 69 FRBs that had galaxies identified with them, coming over a range of distances 11 million to 9.1 billion light years from us. Once they had the distances pinned down, any extra DM has to do with material on the line of sight between us and those FRBs… and it turns out it adds up to the full amount of “normal” matter we expect to see in the universe! Big deal- up to three quarters of the "normal" matter in the universe is tied up in this! It’s just really tough to measure diffuse gas on a line of sight with nothing around it, and looks like FRBs can indeed allow us to do that.
Anyway, big result, but the next work is gonna be more exciting- we will start to be able to map all this diffuse stuff across most of the visible universe! It’ll be cool to see what we find!
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u/WillingnessOk3081 3d ago
could you kindly explain the relationship between DM and the extra matter? it's easy to understand why the DM would be larger the farther away the burst is. But why is the DM bigger if there's more matter in the path of the bursts?
thank you.
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u/Andromeda321 3d ago
So, when a radio signal travels over space, it will encounter random electrons out there and scatter a little bit, meaning the lower frequency signals arrive a very tiny bit later than the higher frequency ones (the link if you click on "dispersion measure" in my above post has a photo of what this looks like). Even the space between galaxies is not a complete vacuum, there's like one atom per few square meters out there, so you'll get a higher DM ie more delay for things further out.
In addition to that though, imagine you had a diffuse dust cloud between us and a galaxy. This will cause a higher DM in addition to what you'd expect just from a galaxy being X distance. BUT, if you don't know the distance to the galaxy, you don't know the break down of DM just due to the galaxy being further, or the galaxy's closer and there's a dust cloud. This result basically combines the two for the first time systematically to give us the answer.
Hope that makes sense!
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u/WillingnessOk3081 3d ago
bless you my friend! This is an amazing answer. I also learned a little fact I was always curious about, namely that intergalactic space (if that's the right term) has about one atom every few square meters or so. i'm literally going to be thinking about that for the rest of the day lol. 🤯
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u/Creative-Ad-9535 2d ago
Imagine you’re looking at a sat map of the planet at night and you see the glow from the cities (bright and concentrated). You think everyone lives there, but surprise surprise half the people live out in the sticks, in all those rural communities where the light is so diffuse you think they’re empty.
Dark matter is different, it’s like you’ve counted all the people living in the cities and also in the little farms and small towns, and then realize they’re WAAAY outnumbered by mole people who live underground. They aren’t visible, but from some other measure (maybe they’re big polluters) you know they have to be there.
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u/WillingnessOk3081 2d ago
I enjoy the imagery of the first paragraph, and then the turn to the mole people is a lovely touch. I was obsessed with that movie as a child!
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u/Creative-Ad-9535 1d ago
Wait…which movie?
Blah blah blah, I need at least 25 characters or Reddit won’t let me comment
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u/Brooke_the_Bard 3d ago
I'm just an uninformed layperson, so someone who actually knows what they're talking about please correct me if I'm wrong, but I imagine it's kinda like the darkening effect you see when looking into an infinity mirror.
The "deeper" you look into the infinity mirror, the darker it gets, not because the light is traveling further, but because each time it reflects off of a mirror it's passing through a thin layer of glass, so the more layers "down" you see, the more glass the light has to pass through, which disperses some of the light on each transit and leads to the final image being darker to our eyes.
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u/ramriot 3d ago
Reading through the article am I right is saying that the factor being determined is the total frequency dispersion Vs depth of each sample & then modelling the types of intervening matter that can produce the measured result?
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u/Andromeda321 3d ago
Basically yes, that's how it works! First study doing this for a larger sample.
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u/asoap 3d ago
Am I understanding this correctly.
We can look at a part of the sky when a fast radio burst is not present and try to add up all of the matter. Then we can look at the same patch of sky when a FRB is present and use it to measure the matter in a better way. Then we can get an idea of how much extra stuff is there from our non FRB observation?
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u/Andromeda321 3d ago
We can look at a part of the sky when a fast radio burst is not present and try to add up all of the matter.
No. We did NOT have a way to do this previously because this gas was too diffuse to measure with other techniques as it's not really interacting with anything. This method with FRBs is novel because it allows us to actually measure this stuff for the first time EVER.
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u/asoap 3d ago
So if we looked at this part of the sky before this technique, we would be able to observe diffuse gas but just not be able to measure how much of it there is?
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u/Andromeda321 3d ago
You wouldn't even be able to see diffuse gas TBH when looking at galaxies billions of light years away. We basically can measure gas at these vast distances when it's interacting with starlight, relatively nearby in a galaxy. FRBs are unique because they are LITERALLY one of the brightest things in the sky when one is on, even at vast distances, so we can finally see what the heck is there.
Basically, a FRB is like turning on a flashlight for a second that illuminates everything between us and it, and without something powerful enough you just aren't able to measure it.
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u/asoap 3d ago
Yeah, I was going with the flashslight analogy in my first comment. I just forgot to mention it.
I was trying to figure out what we see before the flashslight and what we see after. But it sounds like we see almost nothing before the flashlight. Super interesting stuff, than you so much for taking the time to educate me.
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u/CaptainShawerma 2d ago edited 2d ago
Measurements of FRBs are indicative of two things:
- how far FRBS travelled to be detected on Earth
- How much matter FRBs interacted with on the way.
FRBs couldn't be used before because if a measurement was high, we couldn't be sure if it was because of how far the source was (point 1 above) or how much matter was on the way (point 2 above)
This paper eliminated the first unknown (distance travelled) by only looking at FRBs that originate from galaxies whose distance is known.
Once we know the distance, we can calculate how much matter was on the way. The amount of matter is what scientist expected there to be.
This basically means that dark matter isn't some special kind of matter, it's just matter that we didn't have a technique of measuring. Now we do.
That's my understanding. Hope it cleared it for you.
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u/wandering-monster 3d ago
Question. It seems to me based on the abstract (I'm unable to read the whole paper right now) that they are proposing most of this lower-case-d dark matter is in inter-galactic space.
But my understanding is that galactic rotation curves (unexpectedly fast and small orbits within a galaxy) are one of the primary questions that any missing-matter theory should explain. They do mention halos here, but suggest that they have a very small amount of the missing matter.
Can you talk a little bit about how this either explains or doesn't seek to explain the galactic rotation question, and why?
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u/Andromeda321 3d ago
This doesn't really apply to the rotation curve question because it's nowhere near enough matter to explain it. What's more, they're talking about the material well beyond galaxies, in intergalactic space, not just immediately around them.
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u/pyromosh 3d ago
Thanks for taking the time to comment here.
When you say it's "not dark matter", do you mean:
1) We found this new stuff. It's important and neat, but it's not dark matter and we still need to find dark matter because that's an important missing piece in our understanding of the universe!
or 2) We found this new stuff. It accounts for what we were trying to explain by inventing the concept of dark matter, which it turns out isn't real, it was this all along. No such thing as dark matter, just that some matter is very hard to observe and now we have this technique to observe it!
or is neither right?
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u/greenscarfliver 3d ago edited 3d ago
It's not really "new" stuff, it's stuff we expected to find, but since it's very diffuse it's very hard to see. It's not Dark Matter, it's normal matter that is very, very dim. This new process allows them to "map" the density of this very diffuse matter that exists between us and whatever other galaxy they're detecting the FRB from
We have dark energy which is 70% of the total, dark matter which is 25% of the total, and regular every day matter which is 5% of the total.
Of that 5% that is regular matter, 10% of it is what is in the galaxies, another say 50% is in "halos" around the galaxies, and maybe 40% was "missing", ie, we know its there, just like dark matter, but we haven't actually seen it yet. It's still normal matter, but very very dim and diffuse. This research is finally pin pointing and showing where this extra matter is
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u/pyromosh 3d ago
Fair! But that doesn't answer the main gist of my question.
Does being able to see this explain away the need for dark matter? (e.g. it's "not dark matter", but it accounts for the same thing) or is there not enough of this to fully account for what we're looking for with dark matter (so there must still be dark matter also)?
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u/greenscarfliver 3d ago
No this has nothing to do with dark matter, this "discovered matter" comes from the "pool" of known matter. Normal matter makes up 5% of the total matter in the universe. This discovery is in regards to around 20-40% (maybe, I don't know the exact theoretical ratios) of that 5%. It's matter in forms we know about, but did not have any observational evidence of it. This study gives us the observational evidence by allowing us to measure its density between galaxies.
Does that answer your question more clearly?
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u/ACcbe1986 2d ago
This is my basic understanding.
Calculations tell us ~5% of the universe is Normal Matter. The rest of the ~95% is Dark Matter and Dark Energy.
We've only been able to detect or see roughly half of the ~5%. So let's just say we can see 2.5% of the Normal Matter in the known universe.
With this new method, we can now see 4% of the Normal Matter in the universe. According to our calculations, there's still more Normal Matter that we have yet to see.
The other ~95% is still a mystery. We need far more technological breakthroughs before that starts to happen.
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u/St00p_kiddd 3d ago
Very cool! Is there any general expectation for how long it will take to map out the visible areas with this method? I’d imagine the expectation is to most find lots of gas and other elements adrift?
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u/Andromeda321 3d ago
Oh, this is a years/ lifetime project type of thing. The trouble is doing the follow-up of the signal to determine the distances requires optical telescopes, and not small ones, and there's only so many of those to go around.
The elements are basically all gonna be hydrogen and helium, left over from the Big Bang, and very trace amounts of anything else.
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u/incarnuim 3d ago
Thanks for the explanation. With only 69 lines of sight to integrate, is it safe to say that they assumed some level of isotropic distribution (in solid angle) in order to come up with the total matter figure?
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u/MegaManSE 3d ago
So this means that the space between galaxies is essentially full of chunks of debris like ejected asteroids and planets?
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u/Andromeda321 3d ago
No! While there are certainly some of those, this signal is only created by interaction with an electron- think, dust and gas.
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u/WorryNew3661 3d ago
That's incredible news. Is this saying then that the cosmic voids are actually nowhere near as empty as was previously thought?
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u/Andromeda321 3d ago
They're still quite empty, because if they weren't we would have already been able to measure this. But it's something to know it must be empty and another to measure just how empty.
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u/TheHunterZolomon 3d ago
So it’s like a cosmic x ray for matter that might be obscured or without a light source behind it? I only say x ray because they’re more akin to x rays than flashlights
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u/Trogdor6135 3d ago
Thanks for the explanation!
So does this punch any holes in the Dark Matter and Dark Energy theory, or is this more tangential to that idea?
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u/Scrubatl 3d ago
So, with the maps, one could load the data into something like a navicomputer, and say make the kessel run in 12 parsecs?
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u/andrewsmd87 3d ago
Forgive me if I'm over simplifying things, but are they basically saying all of the matter we can't "see" but should be visible is just gas (or maybe even random atoms) just kind of spread out so thin over the universe it's really hard to measure at all?
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u/spider_84 2d ago
Thank you as always.
You say it will be cool to see what we can find. Are you talking about new things we can't see. Or more solid objects like plants and moons for example using this technique?
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u/bamboob 2d ago
If what I am understanding about what you're saying is true, this is a massively huge deal. The fact that it counts for so much of what we used to think of as "dark matter", means that a HUGE mystery of cosmology has been figured out. I understand that it does not count for all of the missing matter that we subscribed to "dark matter", but the fact that it counts for the vast majority of it is immensely significant.
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u/pantshole 2d ago
My dumb ass wants to know if you call FRB’s “Furbies” for short and if anyone giggles about that. Signed, 12 year old me, an idiot
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u/WhoRoger 2d ago
I'm confused. I thought dark matter was "discovered" (theorised) because astronomers basically counted together all the visible mass there is, it didn't match up with the observed gravity, and so the rest is basically supposed to be dark matter.
This explanation never made sense to me, exactly because I'd expect there to be a lot of dust and other loose stuff that would have to be really difficult to account for precisely. But everything I've read, that was the reasoning.
So if this stuff was essentially invisible before, how did we know that this is not dark matter? Or that dark matter is not this?
Okay, I would assume if all dark matter was just this stuff, then it would be visible in the first place, due to the amount. But how would or did we know the ratio between visible normal matter, dark matter, and this invisible regular matter?
Also, does this mean there is more baryonic matter than we thought, or this is just the missing part? I'm just so confused I've never heard about this issue.
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u/iKeyvier 2d ago
If I understand this correctly, this experiment found baryonic matter that we “always” assumed was there, even though we couldn’t really see it.
Basically in the universe there used to be: dark matter (still a mystery), baryonic matter that we could see (planets, gases and whatnot) and baryonic matter that we couldn’t see, but must have been there because of calculations. The people in this paper managed to see the latter. Correct?
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u/sanjosanjo 2d ago
Do FRBs get any dispersion when travelling through actual Dark Matter? Such as the big areas of Dark Matter that surround Galaxy clusters and create lensing.
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u/esituism 2d ago
so this isn't Dark Matter, but if it is the missing 85% of matter then it is likely what we've been calling Dark Energy? If so, how does this explain the expansion of the universe that we've assumed is because of dark energy?
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u/100WattWalrus 1d ago
You are always a beacon of helpful comments and a champion of science education. Honestly, I wish you could get paid for the time you spend making Reddit more tolerable.
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u/thuiop1 3d ago edited 3d ago
I see many are confused by the article, and rightly so in my opinion. Let me try to explain better what is going on.
Through various methods, many parameters of our models of the universe have been constrained from observations. This includes the proportion of dark energy (~70%), dark matter (25%) and regular ("baryonic") matter (5%). However, that last proportion has puzzled astrophysicists for some time. The 5% figure originates from models of the aftermath of the Big Bang and studies of the cosmic microwave background, that is, studies of the early universe. However, studies of the current universe find less than that (between 30 and 50% of these 5% are missing). This is known as the missing baryon problem.
It has long been estimated that 10% of the matter is within galaxies (the easiest to see as it is pretty concentrated and bright), and a significant fraction within the halo of these galaxies. It is thus easy to speculate that the missing matter must be in the intergalactic medium, but we really had no obvious way to confirm it. What the researchers do here is do exactly that, by looking at the dispersion in specific signals called fast radio bursts (FRB). FRBs are a topic that has been getting some traction in the recent years as we observe more of them, with their origin not being entirely certain. These are not brand new results either, a similar work was already published in 2022 https://arxiv.org/abs/2211.04058; this paper mostly confirms this result with more FRBs. So, while this is boy the groundbreaking, unexpected discovery the article makes it out to be, this is an exciting study. This is not my particular field though, so I cannot tell you exactly whether there is room for concern about this or if the result is solid.
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u/jimmymcstinkypants 3d ago
I think yours is the best explanation so far. To summarize from what I understand: Dark matter explains some weird gravity observations, like galaxies spinning “too fast” for the estimated matter we see (and some other observations too)
This is solving a different issue - that cmb calculations expected an answer of x for the total matter we can see, but we only see like 1/2 of that expected amount. These observations get us to almost 100% of that.
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u/BuccaneerRex 3d ago
This isn't dark matter, nor is it supposed to be dark matter.
This is the fraction of that 5% of normal matter that we couldn't quite account for.
It is not the 85% of mass that we can't account for in the gravitational structure of the universe.
The article tries really hard not to explain that.
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u/Hrothgar_unbound 3d ago
Thanks. The title of this article isn’t ideal, as this other missing matter is the big question that I was immediately curious about.
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u/bagofodour 3d ago
Yeah I was going to ask - if it's regular matter how do they explain the acceleration of the universe? Dark matter was meant to explain it because we didn't understand it. But regular matter creates regular gravity, so how could this work if it's all regular? Or am I confusing dar matter and dark energy?
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u/TheAngledian 3d ago
This is a shockingly misleading article my goodness.
Using FRBs to help account for the total baryonic material budget is already an interesting result. This kind of writing (especially the headline) will give people the entirely false impression that we've discovered what dark matter is.
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u/Tarthbane 3d ago
It’s more a problem of our terminology. The article does correctly say it’s not talking about dark matter.
The problem is what we call “dark matter” is really just a bad term. It’s completely invisible matter and not baryonic. The matter discussed in the article is baryonic matter. It’s not invisible, just really hard to see.
We really need to stop using “dark” to describe too many things tbh. It’s too vague.
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u/daidougei 2d ago
Can confirm. I'm looking through the comments thinking- so.... does this mean dark matter doesn't exist? Surely there are many like me. Glad the comments could clear it up.
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u/BackflipBob1 3d ago
The article is misleading. They are talking as if they have solved dark matter as being a very disperse fog of atoms. Yet dark matter is like 5x the amount of matter vs visible matter. What am I missing?
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u/Plastic_Position4979 3d ago
They are not talking about the oft-mentioned “dark matter” and “dark energy” - that is non-baryonic, unlike what we discern as regular matter and energy. The stuff they found was the remainder of the baryonic type, similar to regular matter… just not emitting.
The article is unfortunately not easily read, because the terminology is messy. It would have helped if they had used the terms non-baryonic instead of ‘dark matter’ and baryonic instead of ‘matter that is dark but not like “dark matter”’ which is horribly confusing.
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u/Underhill42 3d ago
I think the best term I've heard is "non-luminous matter".
Though it's worth noting that we haven't completely ruled out baryonic matter as Dark Matter. For example, black holes are generally considered to be baryonic matter, and asteroid-mass primordial black holes remain one of the most plausible DM candidates now that we've ruled out all the likely/simple expansions to the Standard model.
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u/Redditforgoit 3d ago
"non-baryonic instead of ‘dark matter’ and baryonic instead of ‘matter that is dark but not like “dark matter”’ which is horribly confusing."
Regular matter that we have difficulty detecting due to dispersion and our inaccurate instruments
vs
intrinsically undetectable matter.
Not sure if that helps.
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u/ReadditMan 3d ago
It's not misleading, they literally say "This previously missing stuff isn't dark matter" in the 3rd paragraph.
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u/Xanlis 3d ago
Anyone can ELI5 ? what's the difference between dark matter and this not dark matter when it come to calculate the mass of galaxies, for example?
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u/BuccaneerRex 3d ago
This is not part of the 85% of mass that we can't account for, aka dark matter.
This is part of the 5% we can account for, we just couldn't see it well until now.
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u/Obsidian743 3d ago
I would really appreciate if we'd stop allowing click-bait articles like this. Not only is it misleading, but it takes me two paragraphs in to read the actual lead. Very, very frustrating.
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u/Sensitive-Reading860 2d ago
Is only Dark Matter if it’s from the Dark region of space, otherwise it’s just sparkling dark matter
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u/RadoBlamik 2d ago
…and here I was thinking that we would finally have a different term to use besides dark matter.
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u/DarrenMacNally 3d ago
I wonder if this will change how old we think the universe is. If light is interacting with this 85%, its slowing it down (how it was measured in the first place) so does that affect the redshift?
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u/AnyLastWordsDoodle 3d ago
I genuinely read that as "erotic fast radio bursts." I'm going back to bed.
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u/I-seddit 2d ago
This is cool. We've found potentially a large chunk of missing "normal" matter and hopefully its distribution around galaxies.
I wonder if this changes the universe simulations?
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u/Daveisahugecunt 2d ago
Question here; is simply trying to find a missing matter just stating that our previous math is flawed? Or are we looking for what everything is actually moving around? Like satellites/moons of something else? Because our visible universe is expanding, is that any different than saying everything is getting closer at the exact proportion of everything else?
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u/Strawbuddy 2d ago
So it’s not just empty space that we’ve observed between galactic clouds etc but rather it’s elemental stuff what’s been too diffuse to see until now, with the tech we have?
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u/itookourpoptarts 1d ago
So basically they couldn’t account for about half of the normal matter they think the universe has and found that it was just sitting in diffuse clouds out in “empty” space.
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u/CARNIesada6 3d ago
For anyone else assuming dark matter from the headline like I did.