If dark matter is 'invisible,' how do we know it exists?

[Admin]

Dark matter is the mysterious substance that accounts for most of the universe's mass, but it doesn't interact with light, making it effectively invisible. So how do astronomers know dark matter exists?

If dark matter is 'invisible,' how do we know it exists? : Read more

 

[bwana4swahili]

"If dark matter is 'invisible,' how do we know it exists?"
In truth it doesn't and all the $$$'s spent researching dark matter is one science's biggest scams!

 

[Manix]

I agree. I think it is a clutching at straws scenario. We cannot explain certain effects, so we've invented something to fill the void. I think it is more likely there is a fifth force at play; or we truly have misunderstood gravity. it's possible under certain conditions that gravity acts differently to what we understand.

 

[bwana4swahili]

I agree. I think it is a clutching at straws scenario. We cannot explain certain effects, so we've invented something to fill the void. I think it is more likely there is a fifth force at play; or we truly have misunderstood gravity. it's possible under certain conditions that gravity acts differently to what we understand.

I personally think gravity is the culprit. Dark matter is overthinking the whole situation. The KISS principle should be the guiding rule in science.

 

[Manix]

I personally think gravity is the culprit. Dark matter is overthinking the whole situation. The KISS principle should be the guiding rule in science.

Space is so vast and as much as we think we understand what is going on in the Universe, our understanding is very limited. Gravity as you mentioned might very well be the culprit. Our understanding of gravity, when boiled down is what we know here in our little sector of the universe. The way objects act in the Kuiper belt for instance and how, even though we're yet to find a planet nine (or ten if you want to include Pluto), shows how little we understand about gravity. We're assuming there is a larg obejct roaming in that region of space, but it's quite possible that that great white whale might not exist. I'm not sure what the obsession with dark matter is, but they love to push it like it's fact, even though there are other equally plausable hypothesis out there to explain these effects.

 

[bolide]

I'm also inclined to think of "dark matter" as this century's "ether," i.e. a mysterious intangible substance postulated to explain what otherwise seems impossible (in that case it was the propagation of electromagnetic waves through empty space).

It would help if they didn't call it dark "matter," since it also doesn't follow another basic law of "matter," namely that different objects can't occupy the same space at the same time. And if it does have such a gravitational effect, why doesn't it form into clumps, like ordinary matter?

Since in fact the only evidence there is of this stuff is certain gravitational effects, why not seek an explanation of these effects in terms of a better theory of gravity, or of spacetime? That would seem to better satisfy Occam's Razor, by avoiding the supposition of an insubstantial substance that can't be seen or felt.

 

[Nardoel]

The answer is much simpler: we don't know that dark matter exists, and the Webb data show that it likely doesn't since the predictions made by the proponents of the dark matter hypothesis turn out to be false.

Dark matter never was even a theory. It was at best a hypothesis made to account for contradictions between the accepted theory, general relativity, and observations. When you're a scientist and the theory you work with is contradicted by observation, you should at least question the theory rather than reality. But that's inconvenient. It is much more easy to decide that reality isn't what it is, and that in fact it's only a tiny fraction of some hypothetic 'real' reality which is conveniently indetectable, unaccounted for and has whatever properties you need to make it all fit together. The whole thing is unscientific. Sounds more like a bad excuse from a 6 years old.

 

[billslugg]

What then is bending the light from far away galaxies?

 

[Unclear Engineer]

First, the Michelson Morley experiment (https://en.wikipedia.org/wiki/Michelson–Morley_experiment ) did not prove that there is no "aether". It proved that we cannot detect our motion through whatever it might be that light propagates in. And that led to the Lorenz Transformations of Special Relativity Theory that related measurements of time and distance between two separate "inertial frames of reference" that were in motion with respect to each other.

So, now we have theories about light travelling through oscillations of "fields" that permeate all of space. And, according to theory. we cannot detect our motion through those fields.

Except, we do somehow have a dipole in the Cosmic Microwave Background Radiation that seems to indicate we are moving with respect to the frame of reference into which radiation was "released" everywhere in space at roughly the same time shortly after the Big Bang.

Add to that the "Higgs Field", which is theorized to create mass by its interactions with other fields that permeate space, and it seems that we are currently hypothesizing something in the way of a medium that permeates space.

So, our current theories do not assume that space is empty. But, there seems to be a lot of double-speak about what is actually in space.

Sometimes space is "empty" and forces propagate through it via particles called bosons, one for each force we know exists, with light photons being the force carriers for electromagnetic force. (But, we can only hypothesize that "gravitons" carry gravity force.)

Other times, we find the particle theory does not work, and we need to use wave theory to get the results we observe in experiments. That is where "fields that permeate space" come in.

And, the theorists just wave away the dichotomy by saying "Light has the properties of both particles and waves." More correctly. "Light sometimes seems to have the properties of a particle and other times seems to have the properties of waves." "Why" is not really understood.

These theories do not mesh together when we get to describing gravity. So far, we have only succeeded in describing gravity with wave theory.

Dark matter is originally a product of observations not matching theory for astronomy observations at galactic scales and larger. Those observations seem to require more mass than we can account for. At first, astronomers seemed to think it might simply be mass that did not radiate light because it was too cold. Maybe gas or dust clouds, rouge planets, or, black holes.

But, particle physicists have been trying to show that dark matter could be some kind of particle that does not interact with photons. And, as we get better infrared telescopes to be able to see matter that is "dark" with respect to the limited range of light frequencies that our eyes can detect, the argument that it must be some sort of exotic particle(s?) gets stronger. However, we have been looking for such particles for a while now, with consistently negative results.

So, others are working on different explanations involving the theories for various "fields" that produce forms of energy and mass. But, again, so far, those are falling short of explaining all of the observations.

So, what is the real answer? That is yet to be determined. And, determining it will surely require a lot of experimentation and probably also some serious concept re-evaluation.

So, I am not going to criticize anybody for scientific exploration of the real world and the theories about it. But I am going to be skeptical of anybody who claims to "have the answer" until they can convincingly demonstrate that they have succeeded in rectifying theory to predict all available observations using things that we can prove actually exist.

At this point, using "dark matter" to fudge the calculations for observations where that works, but then claiming that observations where no dark matter is needed are examples of " dark matter's absence", without explaining why dark matter would be absent, are not logically convincing that the theory is correct.

 

[bolide]

What is a "field," in this usage? Is it supposed (or do you suppose) that it is something that exists independently of anything that may be present in it, or propagating through it?

 

[Unclear Engineer]

That is an appropriate question.

For an engineer, an "electric field" is the electrical potential difference in space surrounding an object with an electric charge. It cam be mapped with an instrument.

But theoretical physicists have turned that inside-out, and define the electric field as something (not well defined) that permeates all of space. And the things that an engineer views as objects with electrical charges are viewed by the physicists as waves in that ubiquitous electric field.

We at least agree that any change in the charge or position of the object/wave propagates through our fields at the local speed of light. The local speed of light is reduced from its value in a vacuum by the presence of matter.

 

[bolide]

My point was that you seemed to be defending the idea that something like the "aether" might independently exist, as a medium for propagating EM energy. My science dictionary says that a field is a "region" in which a body experiences a force due to the presence of another body, therefore "a method of representing the way in which bodies influence" each other, not anything independent of them.

 

[Unclear Engineer]

Bolide, your definition is the "engineering" version, which I am only trying to explain is not the same as the "theoretical physicist" version. They are really 2 substantially different concepts that are being called the same name. It leads to a lot of confusion and misunderstanding.

My point was that I see inconsistency in the theoretical physicist's denial that there is anything in space that waves of energy propagate through, while still insisting that particles are only waves in a field that permeates all of space, independent of the presence of waves/particles.

The does not mean that I have a "better" theory. I am just pointing out some problems with the theories that some folks claim to be "standard" and thus must be believed.

Getting back to "dark matter", I can conjure up all sorts of concepts for what it might actually be. Some of them are fundamental, and some of them are "emergent", which basically means that dark matter appears to exist because of other phenomena involving more basic things.

But, I don't have any better idea than anybody else what is really true. I just support the process of asking good questions and keeping track of the differences between what we really know and what we are assuming in various conceptual "models".

 

[bolide]

OK, that's clear and interesting, thanks.