Where Is Dark Matter in Our Universe?

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Discussion Overview

The discussion revolves around the concept of dark matter in the universe, particularly questioning its presence and nature. Participants explore theoretical implications, the relationship between dark matter and visible matter, and the philosophical statement "the universe is in us." The conversation includes various perspectives on the properties and distribution of dark matter, as well as its implications for understanding the universe.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • Some participants express confusion over the statement "the universe is in us" and seek clarification on its meaning.
  • One viewpoint suggests that if dark matter exists throughout the universe, it raises the question of whether humans could be made of dark matter, although this idea is considered speculative.
  • Another participant argues that dark matter is not evenly distributed and is not present near Earth, implying that humans do not contain dark matter.
  • Some participants assert that there is no definitive proof of dark matter, suggesting it may be a theoretical construct to address discrepancies in current models of the universe.
  • There are claims that dark matter interacts only gravitationally with normal matter and does not clump in the same way, which some argue is a well-established property.
  • Others challenge the certainty of dark matter's properties, stating that its nature and interactions are still not fully understood.
  • Several participants discuss the implications of galactic rotation curves as evidence for dark matter, while others propose alternative theories like MOND that could explain the observations without invoking dark matter.
  • There is a contention regarding the viability of MACHOs as dark matter candidates, with some asserting they are no longer considered valid based on various measurements.
  • One participant speculates that dark matter could be ubiquitous, similar to how mass is perceived in protons, suggesting a connection between dark matter and the fabric of space.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the nature and properties of dark matter. There are multiple competing views regarding its existence, distribution, and implications, leading to an unresolved discussion.

Contextual Notes

Participants express uncertainty about the definitions and properties of dark matter, with some arguing that current observations do not provide conclusive evidence for its presence in the solar system. The discussion reflects a range of assumptions and interpretations regarding dark matter and its theoretical implications.

universe11
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We are in the Universe and the Universe is in us.
The Universe contains 23% dark matter and 4.6% visible matter; this means there is 5 times more dark matter than visible matter.
If the Universe is in us where is the dark matter?
 
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universe11 said:
We are in the Universe and the Universe is in us.

Am I the only one confused by this "the universe is in us" statement and what that means? Until that point is clarified I do not see how we can get even begin to try and answer this.
 
Yes, please clarify what you mean by that.
 
Pengwuino said:
Yes, please clarify what you mean by that.

I think what OP is trying to get at by the whole "in us" statement is that since dark matter is in the universe(hypothetically speaking) and that we "humans" happen to live in it,could we be made of d.m ? though how erroneous this idea sounds.OP I think we are going ahead of ourselves if we are to answer questions like "where" it possibly is since we don't know what it's basically composed of "only a theoretical particle for now".

If I recall my beginners knowledge on d.m correctly.One way we come to link d.m is by comparing the observed and expected values of the rotational speed of the galaxies.Some of the observed data is given out by neutral hydrogen ions(in regions where light is not present).Please correct me if I am mistaken,Partially being the reason why I made such a lengthy post.
EDIT: At first glance OP's post sounds more like a theological statement.I remember having it read elsewhere...
 
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Also, although you say the Universe is 25% dark matter and 5% visible matter, it isn't a nice even mix in the Universe, i.e there is no dark matter near Earth or the solar system, because if it was there, we would be able to detect it. Therefore humans do not contain dark matter, because if we did, we would have strange empty holes in us with mass we can't see, which is clearly, not the case.
 
Also we have no "proof" of dark matter at all. We are observing effects which contradict our models of how the universe works. Some say Dark Matter is just a solution to prevent the current theory from falling apart by adding this mysterious/magical "stuff" which we cannot explain or detect.

I am not saying it does not exists though as throughout history scientists have had to "add" something to theory's just to make them add up which years later turned out to be correct through further research. It is just that this has not happened with dark metter just yet.
 
"the universe is in us" because of Big Bang.
We are are entangled with the whole Universe...
 
universe11 said:
"the universe is in us" because of Big Bang.
We are are entangled with the whole Universe...

That is my favourite ever comment about science.
 
Happy New Year!

of course in baryonic matter
 
  • #10
Dark matter is not just dark, it doesn't interact with normal matter in any way except gravitationally. Also, it doesn't clump together in the same way as normal matter. Hence in the solar system there is much more normal matter than dark matter. The dark matter will be streaming through normal matter without any noticable effect. (There may be small amounts of dark matter at the centres of the sun and planets)
 
  • #11
chronon said:
Dark matter is not just dark, it doesn't interact with normal matter in any way except gravitationally. Also, it doesn't clump together in the same way as normal matter. Hence in the solar system there is much more normal matter than dark matter. The dark matter will be streaming through normal matter without any noticable effect. (There may be small amounts of dark matter at the centres of the sun and planets)

But, we don't actually know what Dark Matter is, so I don't think we can be that sure about its properties.
 
  • #12
Kracatoan said:
But, we don't actually know what Dark Matter is, so I don't think we can be that sure about its properties.

Sure we can. We are absolute certain that it doesn't "clump", because if it did, we would see different galactic rotation curves than we do.

Your statement also isn't very logical. Suppose I find a blue rock. I don't know what kind of rock it is. Does that mean that I don't know it's blue?
 
  • #13
Vanadium 50 said:
Your statement also isn't very logical. Suppose I find a blue rock. I don't know what kind of rock it is. Does that mean that I don't know it's blue?

Although the fact said rock is blue tells us nothing about the rock's properties, which are by far more important than what colour it is. Same goes with dark matter, we know a little about what it looks like (i.e the blue colour of the rock), but from that we cannot deduce many meaningful properties, such as composition.
 
  • #14
Kracatoan, that's completely wrong. The one thing that we know about dark matter is its distribution, and its distribution puts very strong constraints on its interactions: if it interacted with either itself or ordinary matter with any strength, it's distribution would match that of ordinary matter. It doesn't.
 
  • #15
But knowing that it doesn't interact in the same way as normal matter doesn't tell us anything in addition to that fact. To put even more stress on that point, we don't even know if dark matter is, in fact, matter (to put it bluntly). As I'm sure you are aware, gravity is different on different scales, and theories such as MOND explain dark matter just as well as making up a new type of particle to fit the data. And although we may have evidence that there could be dark matter hanging around at a galactic scale, there is no evidence whatsoever that there is any near, or in the solar system. Which is why I found the first post by chronon so speculative and inaccurate.
 
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  • #16
We have an observation - galactic rotation curves.

We have a theory to explain the rotation curves - "dark matter", a kind of matter that interacts only weakly with itself and with ordinary matter. These properties are necessary to explain the rotation curve.

It is therefore illogical to argue that dark matter does in fact interact more strongly and does in fact clump.
 
  • #17
Precisely, and that is why I am not disputing the point that dark matter does not interact with ordinary matter, in some models. Never have I said that.

I just think that is it highly foolish to take observations on a galactic scale and then make conclusions about what is going on in the solar system, i.e clumps of dark matter in the solar system and inside planets. We don't know enough about it to say anything like that, and I doubt we ever will.
 
  • #18
Vanadium 50 said:
We have an observation - galactic rotation curves.

We have a theory to explain the rotation curves - "dark matter", a kind of matter that interacts only weakly with itself and with ordinary matter. These properties are necessary to explain the rotation curve.

It is therefore illogical to argue that dark matter does in fact interact more strongly and does in fact clump.

But several prominent theories of dark matter do in fact allow for it to clump, and still explain observations (e.g. MACHOS).
 
  • #19
MACHOs are not viable candidates any more. They are in conflict with CMBR measurements, BBN measurements, microlensing measurements and the Bullet Cluster measurements.
 
  • #20
universe11 said:
We are in the Universe and the Universe is in us.
The Universe contains 23% dark matter and 4.6% visible matter; this means there is 5 times more dark matter than visible matter.
If the Universe is in us where is the dark matter?

Wonder anyone recalls that the total masses of the quarks in a proton is quite negligible comparing with the mass of the proton. So it seems what gives the proton its mass is the space(?) within, rather than the quarks itself..Protons (with neutrons) are basically the reason that you have mass which seems to come out of a bunch of space.

I guess, then, maybe the answer is that the dark matter is everywhere just like the matter is; probably the reason for that spatial mass..
 
  • #21
There is 5 times more dark matter than visible matter and looks like nobody have anything to do with it.
I think in the past was the same thing: the Earth is covered with water and people were thinking they do not have water inside their body
 

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