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Primordial black holes not thought to explain dark matter after all,

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black hole/Alain r

… so search called off. In 1971, Stephen Hawking suggested that dark matter consists of primordial black holes formed when dense regions of the early universe underwent gravitational collapse. Such holes were not observed, and one reason could have been small size (less than our Moon). However, from Nature News:

In a paper posted to the arXiv preprint server on 13 January3, astrophysicists Paolo Pani of the University of Lisbon in Portugal and Avi Loeb of the Harvard?Smithsonian Center for Astrophysics in Cambridge, Massachusetts, considered what would happen if small primordial black holes happened to pass through neutron stars, which can be observed from Earth. The researchers suggest that despite their small mass, the black holes would destroy the stars. That means that the presence of neutron stars can be used to place limits on the prevalence of small black holes that would have destroyed them if they existed. “We are using neutron stars as detectors for primordial black holes,” says Loeb.

Pani and Loeb find that the prevalence of neutron stars in the Milky Way almost entirely closes the mass range left open by the 2013 study, meaning primordial black holes, even tiny ones, are unlikely to exist in numbers sufficient to explain dark matter.

Most researchers have assumed that dark matter is actual particles, not black holes, and the search for them continues.

22 Replies to “Primordial black holes not thought to explain dark matter after all,

  1. 1
    Andre says:

    I have said this a million times to friends and almost always with ridicule thrown in my face!


    I rest my case!

  2. 2
    ciphertext says:

    Integers, as an example, have only ever existed in the imagination of man (if by imagination you include “mind”). However, I find them quite useful!

    I don’t think that there will ever be (certainly not in my lifetime) a direct observation of a black hole. By definition it would be difficult to directly observe such an entity.

  3. 3
    owendw says:

    ctext –

    Category mistake – black holes and integers have two distinct ontologies (black holes are supposedly part of the stuff of the universe, while few people would care to argue that the integers are lurking just beyond the next curve, or somewhere).

  4. 4
    ciphertext says:

    So black holes are metaphysically objective (or is posited as such), integers would be metaphysically subjective?

  5. 5
    selvaRajan says:

    Stellar black holes have been found and have been studied in detail. They are detected by the x-ray emitted during accretion, gravitational lensing etc.
    A collapsing stars core needs to be just 3 times the size of our Sun to become a black hole, so we have millions of black hole in our galaxy.

  6. 6
    selvaRajan says:

    WIMPs are the favorite particles for Dark Matter, not primordial black holes

  7. 7
    Andre says:


    Blackholes have never been observed and Einstein’s theory make their existence impossible, sorry for you. Blackholes are a man made thing….

  8. 8
    selvaRajan says:

    Hi Andre @7,
    NuSTAR and Chandra X-ray observatory has been used to observe and study both Supermassive Black Hole and Stellar Black holes. Einstein GR does predict black hole. Black hole was first theoretically derived from Einstein’s GR..
    The Schwarzschild radius is 2G x m/c^2, so that’s roughly 3 solar mass. Hence if core mass is just 3 solar mass, a zero angular momentum black hole can form. Most stellar black holes are 10 to 24 times the mass of Sun.

    Before you object, Yes, I am aware of Einstein’s 1939 paper on why black hole can’t form (he assumes a stable orbit and as the orbit nears the Schwarzschild radius, the orbit speeds up and reaches speed greater than light. However near the Schwarzschild’s radius, orbit should be unstable, in fact there is no orbit at all) and I am also aware of Dr.Krauss’s 2012 stupid paper.

  9. 9
    Andre says:


    I think its time for me to offer you a gobstopper, just in case you shoot your mouth of again… why anybody would willfully lie about something I do not know? Ignorance is what it is I hope!

    Five Fallacies Used to Link Black Holes to Einstein’s Relativistic Space-Time

    But why don’t we ask Einstein himself? A paper of his written in 1939

    Please get yourself updated with the truth because it really will set you free!

  10. 10
    Andre says:


    I hope this helps you in your understanding;


  11. 11
    Andre says:

    Let us be clear black holes have never been observed not anywhere ever!

  12. 12
    selvaRajan says:

    Hi Andre @ 9,

    But why don’t we ask Einstein himself? A paper of his written in 1939…..3320666717

    Refer to my comment @ 8. Para 2 – As I said, Einstein assumes stable orbit even near Schwarzschild radius, which is of course not true. In 1930s no one had an idea of collapsing star.


    I admit I was stunned by utter stupidity of the paper until I realized it was authored by a patent lawyer. E= mc^2 is for rest mass. You don’t calculate momentum from that! The actual equation is E^2 = m^2 x c^4 +p^2 x c^2. p is the momentum. Moreover surface of a collapsing matter doesn’t have to cross the Schwarzschild radius because, the surface of collapsing matter is below it! Only matter being pulled in (accretion) has to enter the event horizon.
    The point is we have observed black holes so all those theories of no black hole is superfluous:
    Partial list of stellar blackholes found studied and photographed. I haven’t even touched Super Massive Blackholes and cluster blackholes found in M31:

    CYGNUS X-1
    GRO J0422+32
    GRO J1655-40
    GRS 1009-45
    GRS 1915+105
    GS 1354-64
    GS 2000+25
    GU Muscae
    GX 339-4
    IC 10X-1
    IGR J17497-2821
    IGR J17497-2821
    LMC X-1

  13. 13
    Andre says:


    Aigain, we have never seen a blackhole, they have never been observed, what you have here is what we think are blackholes, just like we think animals through small successive variations become other animals, its nothing concrete, pure human imagination.

  14. 14
    Andre says:

    More on this and you are wrong my friend

    We are almost positive they exist, but no direct observtion has ever been made…..

    I don’t know about you but I’m very skeptical in believing something unless there is observable and veriviable evidence of it…….

  15. 15
    Andre says:

    This article published in December 2013

    They have never seen a black hole, but believe they exist

    All I can say to you is I hope you guys find one, but truthfully they do not exist, and Einstein is yet to be proven wrong, good luck with your search, notify me when you find one but I won’t hold my breath on science fiction actually becoming science….

  16. 16
    selvaRajan says:

    Hi Andre,
    As you know, we can’t see black hole directly because light can’t escape black hole, so the way we observe and image a black hole is by radiation emanating due to accretion, gravitational lensing and by observing stars orbiting apparent empty space. In fact the Super Massive Black hole of our galaxy(which is what ‘Black Hole Cam’ will ‘capture’) was located by observing 13 orbiting stars.

    The ‘Black Hole Cam’ can’t image the black hole, but only the event horizon of the Black hole(which will show up as a dark shadow during the accretion process).This is now possible because the Chile VLBI-essentially a large array of radio telescope- can observe in 6 (1.3mm) and 7 (0.8mm wavelength)bands.

    We will never ever get the actual image of black hole – not because it doesn’t exist, but because of the nature of black hole – just like you can’t expect to get a black ball’s image in pitch darkness.

  17. 17
    Andre says:


    So Hawkings says there are no black holes. No what are you going to concede, and apologize?

  18. 18
    selvaRajan says:

    Hi Andre,
    The paper is about black hole firewall paradox – a person falling through the event horizon will burn up according to Quantum mechanics, but according to General Relativity the person will feel nothing abnormal at all.
    Dr. Hawkins doesn’t agree with the firewall so he does away with event horizon and introduces ‘apparent horizon’, but if event horizon is removed the quantum information will be lost – how is that possible? So Dr. Hawkins says – no the information will exist in chaotic state (classically chaotic) so though you have information, it is of no use as it cannot be read properly. Effectively it’s lost!
    Does this mean Black hole doesn’t exist? Dr. Hawkins says this:

    The absence of event horizons mean that there are no black holes – in the sense of regimes from which light can’t escape to infinity

    what it means that light or anything travelling at speed of light can escape black hole. Since all matter have mass, no matter can reach speed of light, effectively even in Dr. Hawkin’s new proposal, black hole remains.

  19. 19
    Andre says:

    No they don’t because they don’t exist. They never have they never will. Black holes is as much fantasy as what Frodo is…..

  20. 20
    Andre says:

    No they don’t because they don’t exist. They never have they never will. Black holes is as much fantasy as what Frodo is…..

  21. 21
    selvaRajan says:

    Sure 🙂 Meanwhile another ultra massive black hole found in galaxy cluster RX J1532 .Image released on 23 jan 2014 by NASA Chandra x-ray observatory and Karl G. Jansky VLA

  22. 22
    Querius says:

    However, since Stephan Hawking believes that they don’t exist and NASA believes that they do, are they both correct? 😉


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