# Dark Matter **URL:** \ **Category:** Factual Questions\ **Created:** [January 17, 2019, 4:41am UTC](https://boards.straightdope.com/t/dark-matter/827910 "2019-01-17T04:41:32Z")\ **Posts on this page:** 8\ **Page:** 2
**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\ **Post date:** [January 17, 2019, 10:30pm UTC](https://boards.straightdope.com/t/dark-matter/827910/21 "2019-01-17T22:30:39Z")
> [@scr4](#): > > I’d go one step further and say “dark matter” is really a name for a science mystery. “Dark matter” is a shorthand for “something that explains the discrepancy between different ways we measure the amount of matter in the universe.” It makes no sense to ask if you believe it exists - of course the discrepancy exists, there’s no way to deny that. Your wording is somewhat unclear. The entire point of MOND is that there _isn’t_ a discrepancy in mass, just an apparent but false set of measurements that are an artifact of gravity over distance. The evidence for MOND is very weak but has not been definitively ruled out. You have to define discrepancy in an odd fashion to include MOND as an answer. ---
**Author:** ![leahcim](https://avatars.discourse-cdn.com/v4/letter/l/b4bc9f/32.png) [@leahcim](https://boards.straightdope.com/u/leahcim)\ **Post date:** [January 17, 2019, 10:31pm UTC](https://boards.straightdope.com/t/dark-matter/827910/22 "2019-01-17T22:31:12Z")
> [@scr4](#): > > I’d go one step further and say “dark matter” is really a name for a science mystery. “Dark matter” is a shorthand for “something that explains the discrepancy between different ways we measure the amount of matter in the universe.” It makes no sense to ask if you believe it exists - of course the discrepancy exists, there’s no way to deny that. I’d say it’s slightly more than that. Dark matter is a solution to the discrepancy that posits that it is some kind of hard-to-detect matter causing the difference, as opposed to the discrepancy being caused by our theory of gravity being wrong. ---
**Author:** ![rat\_avatar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rat_avatar/32/255_2.png) [@rat\_avatar](https://boards.straightdope.com/u/rat_avatar)\ **Post date:** [January 17, 2019, 11:53pm UTC](https://boards.straightdope.com/t/dark-matter/827910/23 "2019-01-17T23:53:01Z")
To add to the above. While not ruled out a new version of MOND that accounts for observations will be required to move forward with that direction. The constraints due to observations like the GW170817 have resulted in several forms of MOND that depended on additional matter-coupling fields being ruled out. While MOND in general hasn’t been falsified, the above event did falsify several theories that were MOND. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [January 17, 2019, 11:56pm UTC](https://boards.straightdope.com/t/dark-matter/827910/24 "2019-01-17T23:56:54Z")
Honestly, I’m not sure why folks are so hostile to the idea of dark matter. To me, it would seem to be much more remarkable if it didn’t exist: Why should we expect that most of the matter in the Universe would happen to couple to the electromagnetic force? And indeed, we do know of some non-baryonic dark matter particles already-- Why not more? ---
**Author:** ![rat\_avatar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rat_avatar/32/255_2.png) [@rat\_avatar](https://boards.straightdope.com/u/rat_avatar)\ **Post date:** [January 18, 2019, 1:00am UTC](https://boards.straightdope.com/t/dark-matter/827910/25 "2019-01-18T01:00:11Z")
> [@Chronos](#): > > Honestly, I’m not sure why folks are so hostile to the idea of dark matter. To me, it would seem to be much more remarkable if it didn’t exist: Why should we expect that most of the matter in the Universe would happen to couple to the electromagnetic force? And indeed, we do know of some non-baryonic dark matter particles already-- Why not more? While not universal I find it is related to pedagogy and related ‘physical substance’ and the overloaded ‘mass’ term. In general our education system drills the idea that ‘rest mass’ and ‘matter’ are additive and invariant. It isn’t until one has to start working with the energy–momentum tensor and what contributes to a “thing’s” energy–momentum that the modern meaning is explained. Cosmology, being relativistic by nature uses the more modern meaning. As we delay introducing these subject and expect students to deal with the cognitive-dissonance when special and general relativistic applications are discussed many people never reach this point even if they dig deep into post-doctorate degrees in subjects like chemistry. The classical meaning of _Mass_ as a _fundamental measure of the amount of matter in the object_. is taught as an almost a religious absolute truth or the importance of that specific definition only applying to specific classical domains is lost. As an example. [https://www.ck12.org/c/physical-science/matter-mass-and-volume/lesson/Matter-Mass-and-Volume-MS-PS/](https://www.ck12.org/c/physical-science/matter-mass-and-volume/lesson/Matter-Mass-and-Volume-MS-PS/) > [@](#): > > Matter is all the “stuff” that exists in the universe. Everything you can see and touch is made of matter, including you! The only things that aren’t matter are forms of energy, such as light and sound. In science, matter is defined as anything that has mass and volume. Mass and volume measure different aspects of matter. > … > Mass is a measure of the amount of matter in a substance or an object. Thus ‘matter’ relating to a math relation between the potential energy density, energy-momentum tensor and scalar potential etc… is lost and information about dark matter is viewed as _‘stuff that really isn’t stuff but is stuff’_ It is the same reaction one gets when pointing out that “mass is additive” is not an “empirical fact”, but a postulate which is assumed true without any proof in Newtonian mechanics but not necessarily in theories which superseded it. Those conflicts with domain specific postulates of classical mechanics are almost always the reason behind the discomfort with the concept of dark matter in my experience. ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [January 18, 2019, 1:11am UTC](https://boards.straightdope.com/t/dark-matter/827910/26 "2019-01-18T01:11:31Z")
> [@Exapno\_Mapcase](#): > > Your wording is somewhat unclear. The entire point of MOND is that there _isn’t_ a discrepancy in mass, just an apparent but false set of measurements that are an artifact of gravity over distance. The evidence for MOND is very weak but has not been definitively ruled out. You have to define discrepancy in an odd fashion to include MOND as an answer. I’m objecting to the OP’s framing of the question in terms of “do scientists believe dark matter exists.” If MOND turns out to be the answer, I’d say the dark matter has been explained, not disproved. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [January 18, 2019, 1:25am UTC](https://boards.straightdope.com/t/dark-matter/827910/27 "2019-01-18T01:25:00Z")
I’d say that dark matter is one explanation for the missing mass problem, and that MOND is a different and incompatible explanation for the missing mass problem. ---
**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\ **Post date:** [January 18, 2019, 3:24am UTC](https://boards.straightdope.com/t/dark-matter/827910/28 "2019-01-18T03:24:18Z")
> [@scr4](#): > > I’m objecting to the OP’s framing of the question in terms of “do scientists believe dark matter exists.” If MOND turns out to be the answer, I’d say the dark matter has been explained, not disproved. You just make life hard for yourself when you define words differently than everybody else in the world. [Previous page](https://boards.straightdope.com/t/dark-matter/827910.md?page=1)