5 ms·

Does this have any implications for the amount of dark matter or do estimates of the energy content of the universe not rely on the number of observed galaxies?

• m4dc4pXXX 10y ago
  Also questions I'd like to know the answers to!
  • danbruc 10y ago
    My layman guesses. The ratio of baryonic and dark matter remains unchanged because the new galaxies come with their own dark matter and we can determine the ratio from looking at individual galaxies. The amount of baryonic and dark matter in the universe goes up by a factor of ten unless the new galaxies are exceptionally small or large which would change this factor accordingly. Finally the amount of dark energy goes up to yield the observed expansion rate, no idea if that also means a factor of ten in which case the relative composition of the universe would remain unchanged.
• yummybear 10y ago
  My understanding is that dark matter was "discovered" when trying to find out why stars in the outer edge of a galaxy rotates with the same speed as the inner. A ten-fold increase in number of galaxies doesn't seem to affect this.
• netcraft 10y ago
  I don't think our evidence for dark matter comes from interactions between galaxies but within a galaxy - the interaction of matter within the galaxy and the amount of lensing observed because of the amount of observed matter in a galaxy - in other words I dont _think_ that this will do much to the dark matter calculations - but I am not certain and hope someone knowledgeable will come along and set us straight.
  • flukus 10y ago
    One line of dark matter evidence is galactic clusters, though I'm not sure what the distribution of these "new" galaxies is and whether it would affect this.
• AnimalMuppet 10y ago
  As others have said, the argument for dark matter is based on stars within galaxies, not on the number of galaxies. What this does, though, is change the total mass of the universe (I presume). That might have implications for dark energy (rather than for dark matter), but I can't tell you what the implications actually are.
• jessriedel 10y ago
  Others replying to you are wrong in suggesting that evidence for dark matter comes only intragalactic scales. In fact, there is evidence for dark matter at the much larger scales on which galaxies and galaxy cluster clump. https://en.wikipedia.org/wiki/Dark_matter#Observational_evidence https://en.wikipedia.org/wiki/Dark_matter#Observational_evid... The average mass density of the universe is known within a few percent. http://hyperphysics.phy-astr.gsu.edu/hbase/astro/denpar.html http://hyperphysics.phy-astr.gsu.edu/hbase/astro/denpar.html From reading the article, I believe this is literally just a finding about how many galaxies into which the known amount of matter was clumped in the distant past, i.e., more galaxies with less average mass.
• rusanu 10y ago
  My understanding of the article is that the answer is: No. "found that 10 times as many galaxies were packed into a given volume of space in the early universe than found today. Most of these galaxies were relatively small and faint, with masses similar to those of the satellite galaxies surrounding the Milky Way. As they merged to form larger galaxies the population density of galaxies in space dwindled. This means that galaxies are not evenly distributed throughout the universe's history," I read this as they did not find new visible matter, but they discovered that the visible matter was distributed in many more small galaxies compared with today. I could be wrong though, I'm by no means an expert in this field.
• dogma1138 10y ago
  Potentially, there likely still be "dark matter" but it might we might not need e a new classification of dark matter. We've known for a while now that there seems to be more galaxies out there, heck before the hubble went up we didn't even knew how much there is. There are also indications that there is considerably more intergalactic material out there than we've suspected before. However the problem is that "dark matter" is also needed on local scales, including our solar system; this is a good read http://scienceblogs.com/startswithabang/2013/01/18/why-the-u.. http://scienceblogs.com/startswithabang/2013/01/18/why-the-u.... So "dark matter" is needed to explain our current model of gravity both local and global scales; it is important to note tho that "dark matter" is a placeholder it doesn't necessarily have to be a new type of matter (e.g. AXIONs), some irregular mode for normal matter (e.g. WIMPs) or or it can be regular matter which isn't easily observable (e.g. MACHOs) or it can be also be any combination of the above, and things we haven't even considered yet. Alternatively we might need to rethink our understanding of gravity, and of the existing forces in general, a good point to note is that gravity isn't a traditional force in the first place which already sets it apart from the bunch (it's a property of the distortion of spacetime, it also is only attractive unless dark energy is somehow a very low/zero value property of the gravitational field). So gravity might not work like we think it does, it might be hiding another elementary force, or it might be that gravity on certain scales/conditions splits into multiple forces similarly to how the electroweak force works (at some point during/prior to the big bang all forces/fields were unified at least in theory). Mainstream Physics have been stuck somewhat for a fairly long time on certain aspects, there is also quite a bit of misconception about what works and what doesn't for example most people think that quantum gravity doesn't work which it does, you can use it for everyday life and for many other things, you can't use it during the big bang (and shortly after) and it breaks down near very strong fields e.g. a singularity which is also the internal killswitch or "mathematical contradiction" embedded within general relativity where gravity and spacetime as we know it break down.