<story><title>Dark matter nightmare: What if we are just using the wrong equations?</title><url>http://backreaction.blogspot.com/2019/10/dark-matter-nightmare-what-if-we-just.html</url></story><parent_chain><item><author>superqd</author><text>I very much wish no one had used the terms &amp;quot;dark matter&amp;quot; and &amp;quot;dark energy&amp;quot;, as those imply far more knowledge than we have.  It implies to those unfamiliar that there is in fact some form of energy or matter that has been &amp;quot;sort of&amp;quot; identified, but whose properties are unknown.&lt;p&gt;That isn&amp;#x27;t the case at all.  We have equations we use to predict observations, and in certain cases, those observations are not quite matching what we predicted.  There are a lot of reasons why this can happen, and using the equations poorly is but one of them.&lt;p&gt;I really wish they&amp;#x27;d just said we&amp;#x27;ve found an &lt;i&gt;inconsistency&lt;/i&gt;, between theory and observation, which is the actual case. It would, I think, better inform the public about the actual process of science, rather than making it sound like a new discovery has been made, which has not happened, clearly.  Or perhaps the real discovery &lt;i&gt;was&lt;/i&gt; the inconsistency, and that should be the framing of the problem.  Describing it using sort of known words like &amp;#x27;energy&amp;#x27; and &amp;#x27;matter&amp;#x27; makes the general public think a new type of matter has been found, rather than what has actually been found which is a hole in our understanding.</text></item></parent_chain><comment><author>millstone</author><text>There&amp;#x27;s inconsistencies, and then there&amp;#x27;s &lt;i&gt;real&lt;/i&gt; inconsistencies.&lt;p&gt;Recall some predictions that were later confirmed: the top quark (18 years later) or the Higgs boson (48 years!). These theories were a jigsaw puzzle with a single piece-shaped hole. You could call &amp;quot;inconsistency!&amp;quot; and break apart the whole puzzle, or look behind the couch for the missing piece. (The piece was found!)&lt;p&gt;We also have &lt;i&gt;real&lt;/i&gt; inconsistencies, such as between QM and GR. Not a missing piece but a yawning gap: no single observation can fill in that hole.&lt;p&gt;Dark matter is a &amp;quot;missing piece&amp;quot; problem. The dark matter hypothesis fills in the cosmological missing mass problem, galactic rotation curves, Bullet-cluster-style gravitational observations, the expectation of non-EM interacting particles, and others. The gap between prediction and observation is the size and shape of a single jigsaw piece; let&amp;#x27;s just find it behind the couch.&lt;p&gt;Dark energy is a &amp;quot;real inconsistency&amp;quot; problem. Predictions and observations are orders of magnitude apart. Well hell.</text></comment>
<story><title>Dark matter nightmare: What if we are just using the wrong equations?</title><url>http://backreaction.blogspot.com/2019/10/dark-matter-nightmare-what-if-we-just.html</url></story><parent_chain><item><author>superqd</author><text>I very much wish no one had used the terms &amp;quot;dark matter&amp;quot; and &amp;quot;dark energy&amp;quot;, as those imply far more knowledge than we have.  It implies to those unfamiliar that there is in fact some form of energy or matter that has been &amp;quot;sort of&amp;quot; identified, but whose properties are unknown.&lt;p&gt;That isn&amp;#x27;t the case at all.  We have equations we use to predict observations, and in certain cases, those observations are not quite matching what we predicted.  There are a lot of reasons why this can happen, and using the equations poorly is but one of them.&lt;p&gt;I really wish they&amp;#x27;d just said we&amp;#x27;ve found an &lt;i&gt;inconsistency&lt;/i&gt;, between theory and observation, which is the actual case. It would, I think, better inform the public about the actual process of science, rather than making it sound like a new discovery has been made, which has not happened, clearly.  Or perhaps the real discovery &lt;i&gt;was&lt;/i&gt; the inconsistency, and that should be the framing of the problem.  Describing it using sort of known words like &amp;#x27;energy&amp;#x27; and &amp;#x27;matter&amp;#x27; makes the general public think a new type of matter has been found, rather than what has actually been found which is a hole in our understanding.</text></item></parent_chain><comment><author>joe_the_user</author><text>I don&amp;#x27;t think your description is correct. The situation is we have a reasonably exact theory that assumes that most of the matter in the universe is neutral in the sense of only interacting gravitationally. But that interaction can be calculated quite readily in certain circumstances - for example, we can observe the &amp;quot;dark matter halo&amp;quot; in galaxies through gravitational lensing.&lt;p&gt;This is the dominant theory, it&amp;#x27;s not in contradiction with observations, it&amp;#x27;s just, &lt;i&gt;a little weird&lt;/i&gt;. Why things are like that is the mystery but that&amp;#x27;s it for dark matter.&lt;p&gt;Sure, this stuff is invisible. So is electricity but we deal with that.&lt;p&gt;(Dark Energy I don&amp;#x27;t enough to talk about).</text></comment>