# Is dark matter an actual thing? Or just a coy way of saying "it doesn't add up"? **URL:** \ **Category:** Factual Questions\ **Created:** [November 30, 2006, 3:41pm UTC](https://boards.straightdope.com/t/is-dark-matter-an-actual-thing-or-just-a-coy-way-of-saying-it-doesnt-add-up/382329 "2006-11-30T15:41:52Z")\ **Posts on this page:** 15\ **Page:** 1
**Author:** ![happywaffle](https://avatars.discourse-cdn.com/v4/letter/h/ee59a6/32.png) [@happywaffle](https://boards.straightdope.com/u/happywaffle)\ **Post date:** [November 30, 2006, 3:41pm UTC](https://boards.straightdope.com/t/is-dark-matter-an-actual-thing-or-just-a-coy-way-of-saying-it-doesnt-add-up/382329/1 "2006-11-30T15:41:52Z")
This whole dark matter thing makes me think of taking a math test, coming up with 10 for an answer when it should be 100, and then telling my teacher there must be 90 “dark numbers” that make it all add up. In other words, smugly accounting for an error by just “making up” the stuff that evens everything out. Am I spot-on here? Is the only evidence for dark matter (and dark enegry while we’re at it) the mismatched equations? Is it more reasonable to believe that such things exist, or that current physics estimates are simply wrong? ---
**Author:** ![CurtC](https://avatars.discourse-cdn.com/v4/letter/c/ce73a5/32.png) [@CurtC](https://boards.straightdope.com/u/CurtC)\ **Post date:** [November 30, 2006, 3:59pm UTC](https://boards.straightdope.com/t/is-dark-matter-an-actual-thing-or-just-a-coy-way-of-saying-it-doesnt-add-up/382329/2 "2006-11-30T15:59:49Z")
I think the vast majority of cosmologists think that dark matter is actually real matter of some sort. Most argue for Weakly Interacting Massive Particles (WIMPs) or Massive Compact Halo Objects (MACHOs). There are other ideas, such as Newton’s law of gravity being wrong on large scales, but that opens a pandora’s box of problems and most find it distasteful. ---
**Author:** ![charizard](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/charizard/32/4166_2.png) [@charizard](https://boards.straightdope.com/u/charizard)\ **Post date:** [November 30, 2006, 4:07pm UTC](https://boards.straightdope.com/t/is-dark-matter-an-actual-thing-or-just-a-coy-way-of-saying-it-doesnt-add-up/382329/3 "2006-11-30T16:07:54Z")
Until recently, “dark matter” had been just one possible explanation thrown around to address the “it doesn’t add up” problem But in the last couple of years the evidence has been pointing to the conclusion that dark matter is real stuff that only interacts with regular matter gravitationally. Likewise with “dark energy” being real, as well. A major step was [this recent photo](http://chandra.harvard.edu/photo/2006/1e0657/), which many take to be the first direct observational sighting: ---
**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\ **Post date:** [November 30, 2006, 4:14pm UTC](https://boards.straightdope.com/t/is-dark-matter-an-actual-thing-or-just-a-coy-way-of-saying-it-doesnt-add-up/382329/4 "2006-11-30T16:14:47Z")
The classic example of a particle whose existence was predicted based upon “bookkeeping” is the neutrino. Conjectured by Pauli in 1930 based on momentum not adding up right in beta decay tracks of the then known particles. Not actually detected for 25 years. _But_, neutrinos were conjectured to have very specific properties in terms of charge, spin, interactions, etc. Dark matter, OTOH, is a much vaguer conjecture. Hence the various proposals for types of particles that might compose dark matter. Based on the long history of “it doesn’t add up” leading to the discovery of particles, the existence of dark matter is likely. It is just far too early to know what it is. ---
**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:** [November 30, 2006, 7:16pm UTC](https://boards.straightdope.com/t/is-dark-matter-an-actual-thing-or-just-a-coy-way-of-saying-it-doesnt-add-up/382329/5 "2006-11-30T19:16:23Z")
At least some dark matter is known to exist. You and I are known to exist. The keyboards we’re typing on are known to exist. Jupiter is known to exist. All of these things are made up of dark matter. So in that sense, yes, dark matter exists. However, there’s a limit to how much material can be made up of ordinary matter, even granted that we can’t see all of it. And that limit is, at most, about a third of the amount of dark matter that the math suggests must be out there. So if the math is correct (which is, as you note, not completely accepted), then there must be some other kind (or kinds) of dark matter out there as well. ---
**Author:** ![happywaffle](https://avatars.discourse-cdn.com/v4/letter/h/ee59a6/32.png) [@happywaffle](https://boards.straightdope.com/u/happywaffle)\ **Post date:** [November 30, 2006, 8:24pm UTC](https://boards.straightdope.com/t/is-dark-matter-an-actual-thing-or-just-a-coy-way-of-saying-it-doesnt-add-up/382329/6 "2006-11-30T20:24:59Z")
[QUOTE=Chronos] At least some dark matter is known to exist. You and I are known to exist. The keyboards we’re typing on are known to exist. Jupiter is known to exist. All of these things are made up of dark matter. So in that sense, yes, dark matter exists. However, there’s a limit to how much material can be made up of ordinary matter, even granted that we can’t see all of it. And that limit is, at most, about a third of the amount of dark matter that the math suggests must be out there. So if the math is correct (which is, as you note, not completely accepted), then there must be some other kind (or kinds) of dark matter out there as well. [/QUOTE] Sorry to say, I have NO idea what you mean. We are made of dark matter? I thought dark matter was, y’know, matter that can’t be seen and has never (or almost never) been observed. In other words, the “other two thirds” out there is dark matter. ---
**Author:** ![Ludovic](https://avatars.discourse-cdn.com/v4/letter/l/7ab992/32.png) [@Ludovic](https://boards.straightdope.com/u/Ludovic)\ **Post date:** [November 30, 2006, 8:33pm UTC](https://boards.straightdope.com/t/is-dark-matter-an-actual-thing-or-just-a-coy-way-of-saying-it-doesnt-add-up/382329/7 "2006-11-30T20:33:46Z")
[QUOTE=happywaffle] Sorry to say, I have NO idea what you mean. We are made of dark matter? I thought dark matter was, y’know, matter that can’t be seen and has never (or almost never) been observed. In other words, the “other two thirds” out there is dark matter. [/QUOTE] Planets and other sufficently dense, small, and cold objects such as bicycles, polar ice caps, and Chuck E Cheese pizza cannot be detected at galactic distances and so must be inferred. Therefore, they are dark matter. How much of this dark matter in distant galaxies is “conventional” fermionic matter is still unknown. ---
**Author:** ![Pleonast](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pleonast/32/1183_2.png) [@Pleonast](https://boards.straightdope.com/u/Pleonast)\ **Post date:** [November 30, 2006, 9:01pm UTC](https://boards.straightdope.com/t/is-dark-matter-an-actual-thing-or-just-a-coy-way-of-saying-it-doesnt-add-up/382329/8 "2006-11-30T21:01:20Z")
Remember, these are the same people who call any element heavier than helium “metal”. ---
**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:** [November 30, 2006, 9:24pm UTC](https://boards.straightdope.com/t/is-dark-matter-an-actual-thing-or-just-a-coy-way-of-saying-it-doesnt-add-up/382329/9 "2006-11-30T21:24:19Z")
Using the term “dark matter” just for the mysterious component(s) is somewhat widespread, but it’s not really helpful. We know (or rather, infer) that there’s some quantity of mass out there which isn’t glowing. We know that at least some, but not all, of it is fairly ordinary stuff which just happens to not be stars. But we don’t know exactly how much that “normal” component is, and thus we also don’t know how much is the weird component(s). So it’s probably best to attach the label to the stuff whose quantity we know, which includes both the normal stuff and the weird stuff. ---
**Author:** ![happywaffle](https://avatars.discourse-cdn.com/v4/letter/h/ee59a6/32.png) [@happywaffle](https://boards.straightdope.com/u/happywaffle)\ **Post date:** [November 30, 2006, 9:56pm UTC](https://boards.straightdope.com/t/is-dark-matter-an-actual-thing-or-just-a-coy-way-of-saying-it-doesnt-add-up/382329/10 "2006-11-30T21:56:00Z")
[QUOTE=Ludovic] Planets and other sufficently dense, small, and cold objects such as bicycles, polar ice caps, and Chuck E Cheese pizza cannot be detected at galactic distances and so must be inferred. Therefore, they are dark matter. How much of this dark matter in distant galaxies is “conventional” fermionic matter is still unknown. [/QUOTE] Well, I would count bicycles etc. as part of the mass of the earth, which can be detected at a medium distance, anyway (and which contributes to the solar system’s overall gravitational pull). But I guess if you’re referring to a bicycle-sized hunk of rock floating by itself, a thousand light-years from the nearest star, then yeah, that could be dark matter. ---
**Author:** ![chrisk](https://avatars.discourse-cdn.com/v4/letter/c/6de8d8/32.png) [@chrisk](https://boards.straightdope.com/u/chrisk)\ **Post date:** [November 30, 2006, 10:20pm UTC](https://boards.straightdope.com/t/is-dark-matter-an-actual-thing-or-just-a-coy-way-of-saying-it-doesnt-add-up/382329/11 "2006-11-30T22:20:21Z")
[QUOTE=happywaffle] Well, I would count bicycles etc. as part of the mass of the earth, which can be detected at a medium distance, anyway (and which contributes to the solar system’s overall gravitational pull). But I guess if you’re referring to a bicycle-sized hunk of rock floating by itself, a thousand light-years from the nearest star, then yeah, that could be dark matter. [/QUOTE] Remember that we haven’t even directly observed earth-sized hunks of rock, or Jupiter-sized balls of gas floating around nearby stars (unless I missed something,) though we’ve gotten some indications that the balls of gas are there from wobbles they induce in their suns. Most of the universe is not ‘medium distance’ from us, by a long shot. ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [November 30, 2006, 10:22pm UTC](https://boards.straightdope.com/t/is-dark-matter-an-actual-thing-or-just-a-coy-way-of-saying-it-doesnt-add-up/382329/12 "2006-11-30T22:22:42Z")
[QUOTE=charizard] A major step was [this recent photo](http://chandra.harvard.edu/photo/2006/1e0657/), which many take to be the first direct observational sighting: [/QUOTE] Also [A DIRECT EMPIRICAL PROOF OF THE EXISTENCE OF DARK MATTER](http://arxiv.org/PS_cache/astro-ph/pdf/0608/0608407.pdf) (pdf) > [@](#): > > By using both wide-field ground based images and HST/ACS images of the cluster cores, we create gravitational lensing maps which show that the gravitational potential does not trace the plasma distribution, the dominant baryonic mass component, but rather approximately traces the distribution of galaxies. An 8σ significance spatial offset of the center of the total mass from the center of the baryonic mass peaks cannot be explained with an alteration of the gravitational force law, and thus proves that the majority of the matter in the system is unseen. Modified Newtonian Dynamics (MOND) is dying, long live Nonbaryonic dark matter! ---
**Author:** ![solkoe](https://avatars.discourse-cdn.com/v4/letter/s/919ad9/32.png) [@solkoe](https://boards.straightdope.com/u/solkoe)\ **Post date:** [December 1, 2006, 12:27am UTC](https://boards.straightdope.com/t/is-dark-matter-an-actual-thing-or-just-a-coy-way-of-saying-it-doesnt-add-up/382329/13 "2006-12-01T00:27:09Z")
[QUOTE=chrisk] Remember that we haven’t even directly observed earth-sized hunks of rock, or Jupiter-sized balls of gas floating around nearby stars (unless I missed something,) though we’ve gotten some indications that the balls of gas are there from wobbles they induce in their suns. Most of the universe is not ‘medium distance’ from us, by a long shot. [/QUOTE] Check [this](http://antwrp.gsfc.nasa.gov/apod/ap960131.html) out. I was surprised that some extra solar planets have a mass of less than Jupiter. ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [December 1, 2006, 12:34am UTC](https://boards.straightdope.com/t/is-dark-matter-an-actual-thing-or-just-a-coy-way-of-saying-it-doesnt-add-up/382329/14 "2006-12-01T00:34:04Z")
[QUOTE=solkoe] I was surprised that some extra solar planets have a mass of less than Jupiter. [/QUOTE] About 38% of them [according to the latest list.](http://exoplanet.eu/catalog-all.php?&mode=2&more=) ---
**Author:** ![solkoe](https://avatars.discourse-cdn.com/v4/letter/s/919ad9/32.png) [@solkoe](https://boards.straightdope.com/u/solkoe)\ **Post date:** [December 1, 2006, 1:02am UTC](https://boards.straightdope.com/t/is-dark-matter-an-actual-thing-or-just-a-coy-way-of-saying-it-doesnt-add-up/382329/15 "2006-12-01T01:02:41Z")
[QUOTE=Squink] About 38% of them [according to the latest list.](http://exoplanet.eu/catalog-all.php?&mode=2&more=) [/QUOTE] But that would only be the ones they can detect. There are most likely many small ones but when don’t have the technology to see them. Yet.