4 ms·

> He also says the numbers don’t seem to add up: Dark energy is known to make up 70% of the mass-energy of the universe, whereas black holes are a mere fractio

> He also says the numbers don’t seem to add up: Dark energy is known to make up 70% of the mass-energy of the universe, whereas black holes are a mere fraction of the ordinary matter, which constitutes less than 5% of the universe So it seems both the missing dark energy and the missing dark matter could both be explained for, if there were far more black holes in our universe than we're currently aware of?

contravariant 4y ago
Black holes are a known explanation for dark matter (until recently not for dark energy, as black holes were in the end still thought of as a bunch of dense matter). There are bounds on the size and quantity of such black holes, which get increasingly tight as more data on dark matter becomes available.
mr_mitm 4y ago
Primordial black holes used to be a dark matter candidate but have been largely ruled out. This has been extensively studied already. They'd be anything but supermassive, though. The exact opposite, to be precise.
shagie 4y ago
The "black holes as dark matter" were termed MACHOs (massive astrophysical compact halo object) https://en.wikipedia.org/wiki/Massive_compact_halo_object https://en.wikipedia.org/wiki/Massive_compact_halo_object Most of that has been ruled out (see the graph on http://resonaances.blogspot.com/2016/06/black-hole-dark-matter.html http://resonaances.blogspot.com/2016/06/black-hole-dark-matt... ) and while some black holes may fall into the dark matter category, the observed "if there were that many black holes, micro lensing would be this common..." The result of those tests constrains black holes to less than 1% of the calculated dark matter... though there are some windows where there is very likely active research to try to detect black holes with those masses along with the cosmological models needed to have an early universe that produces black holes of that size in that quantity. From https://arxiv.org/pdf/2007.10722v3.pdf https://arxiv.org/pdf/2007.10722v3.pdf > Primordial Black Holes, in particular asteroid mass ones, remain a viable dark matter candidate. Further improve- ments in the theoretical calculations of the production and evolution of PBHs are required to reliably predict the abundance and properties of PBHs from a given model. Even so, it seems clear that a cosmologically interesting num- ber of PBHs can only be produced in specific models of the early Universe, and often fine-tuning is required. However, whether or not PBHs are a significant component of the DM is a question that has to be answered observationally. Novel ideas are needed here to either detect or rule out the remaining open parameter space. Note that we're dealing with really small ones that haven't evaporated yet. The chart on page 16 - with M PBH [g] and the X axis of 10^15 to 10^36 - that's grams. Also fun - https://github.com/bradkav/PBHbounds https://github.com/bradkav/PBHbounds which has them in solar masses
vecter 4y ago
The remaining ~25-27% is suspected to be dark matter.

contravariant 4y ago

Black holes are a known explanation for dark matter (until recently not for dark energy, as black holes were in the end still thought of as a bunch of dense matter). There are bounds on the size and quantity of such black holes, which get increasingly tight as more data on dark matter becomes available.

mr_mitm 4y ago

Primordial black holes used to be a dark matter candidate but have been largely ruled out. This has been extensively studied already. They'd be anything but supermassive, though. The exact opposite, to be precise.

shagie 4y ago

The "black holes as dark matter" were termed MACHOs (massive astrophysical compact halo object) https://en.wikipedia.org/wiki/Massive_compact_halo_object https://en.wikipedia.org/wiki/Massive_compact_halo_object Most of that has been ruled out (see the graph on http://resonaances.blogspot.com/2016/06/black-hole-dark-matter.html http://resonaances.blogspot.com/2016/06/black-hole-dark-matt... ) and while some black holes may fall into the dark matter category, the observed "if there were that many black holes, micro lensing would be this common..." The result of those tests constrains black holes to less than 1% of the calculated dark matter... though there are some windows where there is very likely active research to try to detect black holes with those masses along with the cosmological models needed to have an early universe that produces black holes of that size in that quantity. From https://arxiv.org/pdf/2007.10722v3.pdf https://arxiv.org/pdf/2007.10722v3.pdf > Primordial Black Holes, in particular asteroid mass ones, remain a viable dark matter candidate. Further improve- ments in the theoretical calculations of the production and evolution of PBHs are required to reliably predict the abundance and properties of PBHs from a given model. Even so, it seems clear that a cosmologically interesting num- ber of PBHs can only be produced in specific models of the early Universe, and often fine-tuning is required. However, whether or not PBHs are a significant component of the DM is a question that has to be answered observationally. Novel ideas are needed here to either detect or rule out the remaining open parameter space. Note that we're dealing with really small ones that haven't evaporated yet. The chart on page 16 - with M PBH [g] and the X axis of 10^15 to 10^36 - that's grams. Also fun - https://github.com/bradkav/PBHbounds https://github.com/bradkav/PBHbounds which has them in solar masses

vecter 4y ago

The remaining ~25-27% is suspected to be dark matter.