What particles are black holes made of?

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Discussion Overview

The discussion revolves around the composition of black holes and the calculation of particle ratios in the universe, specifically focusing on known matter while excluding dark matter and dark energy. Participants explore the nature of black holes and the feasibility of estimating the total number of various particles, such as quarks, electrons, and neutrinos.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants question whether black holes are made of particles, suggesting that they are defined by a region of curved space due to dense mass, making the type of mass irrelevant.
  • There is a proposal to calculate the ratio of types of particles in the universe, specifically focusing on up and down quarks, electrons, and neutrinos, while excluding black holes, dark matter, and dark energy.
  • One participant mentions that rough estimates for the number of atoms in the observable universe can be made based on the total mass, primarily considering hydrogen atoms.
  • Another participant notes the challenge of estimating the number of neutrinos due to their low mass and suggests that they are part of the cosmic neutrino background, which is abundant in the universe.
  • There is a reference to the cosmic energy inventory, which estimates particle numbers based on energy divided by typical energy per particle, highlighting the predominance of hydrogen and helium in the mass composition of atoms.

Areas of Agreement / Disagreement

Participants express differing views on whether black holes are made of particles, with some asserting they are not, while others focus on the calculation of particle ratios without reaching a consensus on the nature of black holes.

Contextual Notes

Limitations include the exclusion of dark matter and dark energy from particle calculations, as well as uncertainties in estimating the number of neutrinos due to their minimal impact on total mass.

fxdung
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What particles that constitute the black holes?Does normal particles constitute the black holes?
How can we calculate the ratio of types of particles in the universe(we consider known matter but not consider dark energy and dark matter)?How can we calculate the total number of particles in the universe?
 
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Black holes are not made of particles. A black hole is defined by a region of extremely curved space, caused by the presence of extremely dense mass. The type of mass that creates the curved space is irrelevant.
 
Then if we do not consider Black Holes,Dark Matter and Dark energy,could we calculate the ratio of types of particles? Could we calculate the total number of up and down quarks,of electrons and of neutrinos in the Universe?
 
fxdung said:
could we calculate the ratio of types of particles? Could we calculate the total number of up and down quarks,of electrons and of neutrinos in the Universe?

We can make rough estimates for the number of atoms in the observable universe based on the total amount of mass; see, for example, here:

https://en.wikipedia.org/wiki/Observable_universe#Matter_content_.E2.80.94_number_of_atoms

This estimate is based on most of the atoms being hydrogen atoms, so the number will also give a rough estimate of the number of protons (and hence quarks) and electrons. You could use estimates of the relative abundance of heavier elements to make a rough estimate of the number of neutrons (which would adjust the estimate for quarks). I'm not sure how you would estimate the number of neutrinos, since they are too light to affect the total mass significantly.
 
PeterDonis said:
I'm not sure how you would estimate the number of neutrinos, since they are too light to affect the total mass significantly.
Most neutrinos are part of the cosmic neutrino background. You can compute it the same way you compute the photon density from the CMB. The result is large, neutrinos are the second most abundant particle in the Universe.
 
The cosmic energy inventory does a related estimate: not particle numbers, but energy. Divided by the typical energy per particle it gives particle numbers. For atoms. about 3/4 of the mass is hydrogen and 1/4 is helium, the contribution from other elements are negligible (unless you consider planets separately).
 

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