It just kind of feels like there's a scale with weight on it that, by everything we now observe, should only weigh 200lbs and instead is reading 300 -- it just seems that "broken scale" is a better explanation than "invisible stuff on the scale."
Dismissing it as an incorrect measurement ignores the depth people have long gone into to verify this discrepancy between predictions and reality is not a sensor problem.
Almost 2 centuries ago astronomers found that the orbit of Mercury didn't make sense according to Newton's laws, laws which were at the time considered infallible. The astronomers only explanation was that there was a planet closer to the sun that we couldn't see, they believed this so much that they even named the planet Vulcan and spent many years searching for it.
Turns out that there was no Vulcan and general relativity explains the discrepancy in the orbit of Mercury.
That discovery made both Le Verrier and the world at large very excited, and the race to repeat that feat lead to everyone jumping to conclusions about Vulcan.
So it'd be more like a couch that's supposed to weight 200 lbs reads 300 lbs on a scale. But we've tested it on a half dozen different scales from different makers and keep getting 300 lbs. In addition we've tested this other couch that's suppose to read 100 lbs on some of these scales, and it correctly reads 100 lbs.
Dark matter works well because it's designed to fill in the gaps in our current understanding of astrophysics data. Given it's origin it of course can perfectly explain the data, because that's what it was designed to do.
However, that doesn't necessarily make dark matter particularly useful for understanding how nature actually works.
> Dark matter works well because it's designed to fill in the gaps in our current understanding of astrophysics data.
"Works well" seems like you are looking at it the wrong way. Nobody is touting "dark matter" as a solution. It's the problem itself.
However, this nickname is not absurd, in the sense that the gravity equations for the movement of stars in galaxies don't match the observation.
In order for the stars to move inside their galaxies at their observed speed, these galaxies should have much larger mass.
Hence the "dark matter".
Scientists do not all agree that there is an "invisible" matter to be found. Many think that Einstein's relativity has a more limited domain of validity than we thought.
But then the issue is as dark (in the sense of mysterious), since many of Einstein's predictions - based on his equations - have been observed in experimentations. The gravitational waves (LIGO experiment and other replications) appear to prove that the relativity equations are right. The precision of this instruments are extraordinary.
It's a terrible situation for Physics as a discipline: the equations are confirmed in all know situations, except this case (well, as far as I understood).
There are plenty of theories for explaining the phenomenon, but they lack an feasible experiment to see if their predictions match the observation.
Today, all the theories with feasible experiments have proven to be false. Physicists are stuck.
Many think that we need a new Einstein or a new Newton, meaning a genius among the geniuses, capable of think a whole new paradigm for gravity.
Gravity is a "law" and not a "force". It's as well the nickname for a phenomenon ; that phenomenon is sensible in the domain of validity of Newton, e.g. in our daily life.
The planets in the solar system move all accordingly with Newton's equations, except Mercury. Einstein had to totally put upside down the way we represent the world we live in, from a 3D world with a totally independent time to a 4D world, where everything and everyone live in its own spacetime.
Let's imagine two atomic clock set next to each other and synchronized. If we elevate one by 1 cm, then the clocks have a super slight desynchronizarion. And the tiny tiny difference match Einstein's equations.
Newton and Einstein are a few centuries apart. When will such genius reveal itself? Some physicists point that both were outsiders in their times. Nowadays, the knowledge is so vast that it takes ten years to master a fraction of it: by that time, a brain is so entrenched in the current representations that it's difficult to break the paradigm.
Others think likely that one of the theories already published is right but we'll need to wait a very long time, if ever, before being able to make the experiment that will prove it.
Maybe we will have to accept not being able to explain our universe. After all, since Gödel, mathematicians have kept going despite his proof that the mathematics are based on a quite fragile foundation.
I never quite understood that Gödel thing. Anyone to try and explain us that "dark" theorem?
That may seem surprising, but I don't think it is. There are infinite sets and infinite things you can say about them. It's not really a shock that there might be some properties about that set you can only prove by inspecting all of the elements, but you can't actually do that in finite time -- even though it's true. The sets are infinite, the theorems and their proofs are (by definition) not.
That doesn't mean that the foundations of math are fragile. It just means that there are facts you don't know. But you already knew that, too.
The specific theorems that can't be proven are just a subject of your axiom set. You can prove, or disprove, any specific thing you want, by taking it as axiomatic. It's just a question of whether anything interesting follows. That's a judgment for mathematicians, not a fact of mathematics.
I am, of course, handwaving like crazy, and probably driving the mathematicians nuts. Even though I said that the theorem is less surprising than it might seem, the fact that you can prove the theorem itself strikes me as very surprising.
I'm not aware of any significant number of scientists who think this. Even proponents of MOND acknowledge that they need to come up with a viable relativistic formulation of their theory.
This is not correct. Our measurements are accurate enough now that we have detected relativistic corrections in the motion of, IIRC, at least all the planets out to Jupiter or Saturn.
It’s called dark because it doesn’t interact with the electromagnetic field (i.e. we cannot see it) and matter because it’s otherwise assumed to behave just like the matter we can see.
It is a bit of a “We don’t like it, but it’s the best we can do for now”, but it is not like physicists invented something completely out of thin air to make the theory explain observations.
I basically came into the comments here just to see all the complete armchair novices come out of the woodwork to explain how they think they're smarter than the actual physicists.
Speaking of which, shall we start a discussion on climate science? ;-)
Here's a Monty Hall explainer. Will a plane on a treadmill take off? When you shower, do you explicitly wash your legs? Did you know that 0.999...=1?
That makes it really tempting to think "well maybe it's the model/equation that's wrong", which has been exactly the case throughout scientific history: planet Vulkan vs Relativity, phlogiston vs oxygen, luminiferous ether vs QED.
https://aether.lbl.gov/www/classes/p10/gr/Precessionperiheli...
For those who haven't heard of this, the idea is that the gravitational constant actually changes at very high rotational speeds / centripetal accelerations (such as those at the galactic scale), and this is why our Earth-based gravity experiments don't detect this because we're in roughly the same reference frame and don't see the effect.
https://en.wikipedia.org/wiki/Modified_Newtonian_dynamics
(Also, I am really not a physicists, so I'll let them chime in)
First, the MOND regime is not very high (large) accelerations, but very low (small) accelerations.
Second, the MOND hypothesis is not quite that the gravitational constant changes; it's that the form of the gravitational force changes--it's no longer the Newtonian inverse square force.
The key issue with this is that Newtonian gravity isn't our best current theory of gravity: General Relativity is. MOND as it was originally proposed is not a relativistic theory; there have been attempts to formulate a relativistic version, but none of them have resolved all of the open issues.
> this is why our Earth-based gravity experiments don't detect this because we're in roughly the same reference frame and don't see the effect.
No, that's not why MOND proponents say we don't detect the effect in Earth-based experiments. It's simply that we can't reproduce the required conditions on Earth (the net gravitational acceleration from all sources being small enough to get into the MOND regime).
I'm unsure the differences between "same reference frame" vs. "can't reproduce the required conditions" - ie Isn't it that in order to reproduce the very low accelerations we can't be in our current location with its high accelerations? I'm guessing there's some nuance between location / ref frame here that I'm missing.
"Same reference frame" is just an abstraction (and quite often a meaningless one--according to the proper concept of "reference frame" in physics, there is no such thing as being "in" one reference frame but not another).
"Can't reproduce the required conditions" is a straightforward statement about the limitations of what we can do with our current technology.
> Isn't it that in order to reproduce the very low accelerations we can't be in our current location with its high accelerations?
According to MOND, yes, in order to test it we would have to set up a lab out in deep space (i.e., not near any planet or star) far enough away from the center of our galaxy that the sum of all the "accelerations due to gravity" from all sources was less than the MOND threshold. Which of course is well beyond our current technical capability. But none of that has anything to do with "reference frames".
Many people walk away with the assumption that dark matter is literally massive lumps of stuff out there that is just really hard to see. Kind of analogous to stealth aircraft or something. This sounds absurd and it is. And its why a common reaction is to consider it absurd and that we probably just have gravity wrong.
The reality is that dark matter is just the name given to a set of observations. It wasn't intended to be descriptive. We are talking about scientists here, not public relations. So they are liable to fumble in the PR bit. Its not what they are good at. I consider the Neil DeGrasse Tysons and Michio Kakus of the world more to blame than the community at large. They have chosen to become the popular face of science and with that have a responsibility to properly communicate it. Their failure contributes to why people distrust academia to some degree.