11 ms·

Nasa’s Roman Mission Will Hunt for Primordial Black Holes

140 points by gmays 3y ago

api 3y ago
Primordial black holes are a fascinating topic. One of my favorite hypotheses is that "planet nine," a large possibly 1-5 Earth mass planet suggested by some orbital models to exist beyond Neptune and Pluto in the far outer solar system, may be a primordial black hole. If such a thing existed it'd be a black hole about the size of a billiard ball and would be extremely hard to detect. It would not emit Hawking radiation (Hawking temperature still below the CMB), so the only thing it would emit would be when it encountered something and tore it apart. In that case you'd see X-rays, gamma rays, etc., but maybe only briefly. Only way to find it might be to model orbits accurately enough to predict its position and then look for gravitational lensing. If this companion object did exist it'd be a gigantic discovery of huge importance. It'd be within reach of probes, making it possible to study and even do experiments on to investigate things like quantum gravity. It could also be used in tight gravity assist flybys to accelerate probes to incredible velocities, maybe making interstellar probes a lot more practical. It'd be our very own way to yeet stuff to the stars, assuming these things could withstand insane g-forces (so probably not humans unfortunately).
- ryandrake 3y ago
  > It could also be used in tight gravity assist flybys to accelerate probes to incredible velocities, maybe making interstellar probes a lot more practical. Would 1-5 earth masses really provide enough of a yeet to appreciably affect the speed of a probe? Jupiter is about 300+ earth masses and we're not flinging probes out to stars using him.
  - bigyikes 3y ago
    You can get a lot closer to the center of mass of the black hole, which should drastically increase acceleration since it falls off with distance squared.
    - gus_massa 3y ago
      The satelite acelerates when it aproach the planet, but most of it is compensated when it goes away. There is a nice graphic in https://en.wikipedia.org/wiki/Gravity_assist#/media/File:Voyager_2_velocity_vs_distance_from_sun.svg https://en.wikipedia.org/wiki/Gravity_assist#/media/File:Voy...
      - pixl97 3y ago
        You toss off some mass as you pass the black hole and it gives a powerful boost.
        gus_massa 3y ago
        Do you have a source for that?
        vundercind 3y ago
        Star Trek fans will recognize the name as that of a versatile light starship class often seen acting as science vessels. https://en.m.wikipedia.org/wiki/Oberth_effect https://en.m.wikipedia.org/wiki/Oberth_effect FWIW I’ve read several explanations of why this works, including some confidently claiming that one or more of the others was wrong, and a couple of which kinda made sense as I was reading them, but not a one of them has made a lick of sense to me after I thought about it for a while. Despite all the attempts at understanding it, I still couldn’t tell you why it works (aside from “this math says it does” which is a shit answer) [edit] the other thing you can do, even at the same time is: https://en.m.wikipedia.org/wiki/Gravity_assist https://en.m.wikipedia.org/wiki/Gravity_assist But the specific effect in question seemed to be the Oberth Effect, given the mention of throwing off mass. Gravity assist just relies on the body in question being really heavy and in (orbital, say) motion in some fashion that’s useful to you. Kinda “pulls” you along. You steal a negligible amount of energy from a huge body, which translates into some decent speed for your very-light spacecraft.
        MeImCounting 3y ago
  - dooglius 3y ago
    We did, Voyager 1 and 2 used Jupiter to get out of the solar system
    - Sharlin 3y ago
      And the Pioneers and New Horizons too.
- caf 3y ago
  Assuming you don't go so close that tidal effects tear the probe apart, the g-forces should only be those imposed by the probe's thrusters firing during the assist. When the thrusters aren't firing it's just in free-fall.
  - kadoban 3y ago
    Hm, that can't be how that works, can it? How do you get any extra velocity then if there's never any acceleration beyond what your thrusters provide?
    - messe 3y ago
      It's called the Oberth Effect. In short, in Orbital mechanics, burning your thrusters deeper within a gravity well, results in a greater increase in kinetic energy than burning them further out. This is because momentum ~ v, while kinetic energy ~ v^2. If you're travelling faster—as you would be as you approach the black hole and fall deeper and deeper in your orbit—then you can expend to same amount of momentum to receive a disproportionally larger increase in kinetic energy. Because your potential energy falls off with distance to the black hole at the same rate regardless of the speed you're travelling at, your total energy upon escaping the black hole is much larger than it would be had you burned your thrusters outside its gravity well.
      - deleted 3y ago
        [deleted]
      - HeatrayEnjoyer 3y ago
        But you are still burning the same amount of chemical energy...
        ibeforee 3y ago
        Wikipedia says: In terms of the energies involved, the Oberth effect is more effective at higher speeds because at high speed the propellant has significant kinetic energy in addition to its chemical potential energy.[2]: 204 At higher speed the vehicle is able to employ the greater change (reduction) in kinetic energy of the propellant (as it is exhausted backward and hence at reduced speed and hence reduced kinetic energy) to generate a greater increase in kinetic energy of the vehicle.
- Loughla 3y ago
  I feel like if you were close enough for a gravity assist, wouldn't the tidal forces just tear the probe apart?
  - Tostino 3y ago
    Not necessarily. If you replaced the sun with an equivalent mass black hole, none of the orbits of the planets would change.
    - tsimionescu 3y ago
      Sure, because none of the planets are anywhere near close enough to the sun to experience tidal forces. But if you were to approach the sun VS a sun-mass black hole, at some distance the difference would become noticeable through tidal forces (ignoring the massive difference in emitted radiation, of course).
    - jebarker 3y ago
      I'd like to see a simulation of what that would look like. I mean, if by magic the sun was replaced with an equivalent mass black hole in an instant would anything be visible from earth before the inevitable freeze?
      - utensil4778 3y ago
        From Earth's perspective, you wouldn't see anything interesting except for the sun vanishing. Gravitationally, all that matters is the absolute mass, so all the dynamics of the solar system stay the same. A black hole of 1 solar mass has a radius of something like 3km. Totally invisible from Earth. You probably wouldn't even see any gravitational lensing. All we would see is the sun there one moment, and then nothing the next. Life on Earth would continue for a while, but the planet would eventually freeze over. So, nothing interesting. The sun vanishes and then some time later you freeze and/or starve to death.
        jebarker 3y ago
- sandworm101 3y ago
  At that size, very few things would ever get close enough to be torn apart, let alone fall in. We should look for objects suddenly changing course ivo the potential black hole.
- perihelions 3y ago
  - "In that case you'd see X-rays, gamma rays, etc., but maybe only briefly." One speculative possibility is that we could find a continuous gamma annihilation signal from its dark matter halo, https://arxiv.org/abs/1909.11090 https://arxiv.org/abs/1909.11090 https://hn.algolia.com/?query=What%20If%20Planet%209%20Is%20a%20Primordial%20Black%20Hole%3F&type=story https://hn.algolia.com/?query=What%20If%20Planet%209%20Is%20...
breckenedge 3y ago
I really want primordial black holes to turn out to be the missing antimatter from the Big Bang, but I don’t think that could ever be tested. And of course a mechanism for this would probably need new physics since antimatter interacts the same as normal matter wrt gravity.
- deepsun 3y ago
  When I asked similar questions physicists, turns out all of them were thought off and tested long time ago. E.g. small black holes would still cause detectable and attributable radiation.
- stainablesteel 3y ago
  it sounds a lot like it now that i read this, large dispersed amounts of antimatter that apparently doesn't give off light yet has massive gravitational pull
  - nullserver 3y ago
    https://youtu.be/qy8MdewY_TY?si=NVZzWJSFXl4EATRK https://youtu.be/qy8MdewY_TY?si=NVZzWJSFXl4EATRK Good video on topic
  - ccgreg 3y ago
    Antimatter has the same electrodynamic properties as matter.
- pfdietz 3y ago
  There were suggestions that the antimatter-matter asymmetry is because antimatter was preferentially segregated into a dense phase of hadronic matter, like quark matter nuggets. This would be interesting because if such nuggets could be found and captured, they'd be a potential source of energy by annihilation with ordinary matter.
  - exe34 3y ago
    Spicy nuggets.
woopsn 3y ago
Fascinating mission. I don't understand how microlensing events resulting from primordial black holes can be differentiated even statistically, given that they "can't be formed by any known physical process", but in any case it's exciting to discover there's much more of something up there than we knew. Even if they are "just" rogue planets.
- api 3y ago
  We have a variety of ways to make insanely precise measurements of light to the point of counting photons. I’m guessing that factors into being able to detect microlensing.
hyperific 3y ago
NASA in the title should be all capital letters as it's an acronym and not a name.
- jdminhbg 3y ago
  Depends on where you live: https://proofreadingpal.com/proofreading-pulse/writing-guides/us-vs-uk-english-grammar/#:~:text=Acronyms%20(Initialisms%2C%20per%20UK),Nasa%20and%20Unesco%20(UK).&text=Collective%20nouns%2C%20which%20are%20nouns,but%20singular%20in%20US%20English https://proofreadingpal.com/proofreading-pulse/writing-guide....
  - ibeforee 3y ago
    nasa.gov is the domain here
  - ralferoo 3y ago
    As a Brit, I've never noticed NASA spelt Nasa before, and I'm on the fence about Unesco, not because I recall seeing it title-caps, but because it doesn't look offensive to me. That said, when I googled for the title-caps variants of both words, I saw the Guardian, Independent and Times all used it for Nasa, but only the Guardian and Times seem to use it for Unesco. There was also a page from the NYT that used Unesco, so a counter example from the US, but even the UK government pages refer to it in all caps, as do most other UK articles. I certainly find it a weird generalisation that "UK English" (sic) prefers title-caps, as we tend to like our abbreviated names and pretty much always use all-caps when every letter comes from a separate word, and only title-caps when we use runs of letters from each different word - quango (quasi-NGO), Bakerloo (Baker St-Waterloo), Beeb (compared with BBC), Lib Dems, etc. We also have a few things that aren't consistent for government things - Defra (always used to be DEFRA, but they seem to have rebranded), MOD (always caps), Ofqual (=Office of Qualifications, always title case), Ofcom (=Office of Communications, now seems to officially be title case, but always used to be OFCOM), UCAS (University and Colleges Admission Scheme, always all-caps), etc. Maybe the stylistic choice is based on how pronounceable it is as a word, but whatever I don't think there are any hard and fast rules!
kristianp 3y ago
Launching by May 2027. Was hoping it would be sooner, given the presence of this article, but it seems they drip feed them out gradually. https://science.nasa.gov/mission/roman-space-telescope/ https://science.nasa.gov/mission/roman-space-telescope/
chefkd 3y ago
question for the initiated: why do space agencies divide their resources and attention between different projects? Wouldn't it make sense to focus first on making the moon and it's resources accessible kind of like airplanes then systematically expand to Mars, asteroid belt, and so on instead of spreading out too thin without conquering the closest
- macintux 3y ago
  Purely speculative: - Betting everything on a single huge project is risky. You wait for years for completion, and if some critical part of the project costs more/takes longer than expected (much like Artemis today) you risk achieving nothing at all. - Small, cheap projects that don't bankrupt the agency if they fail, when they succeed, generate ongoing positive PR and scientific results. NASA famously promoted this concept after one or two expensive projects had problems (of course, not famously enough that I remember more details). - Some of those smaller projects are critical, like climate monitoring. You can't just set aside those sorts of tasks for a literal moonshot. - Smaller projects contribute towards the big ones: NASA has given SpaceX a fair bit of money over the years that is paying off with Starship and Artemis.
mrcwinn 3y ago
What the heck is "Nasa"? Not the sword I'll prefer to fall on, but even if you're in the UK, let's honor that this organization is in the United States and they self-describe as "NASA."
scotty79 3y ago
I believe that most black holes in the universe are primordial. Even most of the star sized ones. And definitely the supermassive ones. But it would be super nice to find the ones with masses that are unexplainable in the current framework.
- luyu_wu 3y ago
  Why would you believe this? Stars collapse into black holes all the time as long as they're over the threshold mass.
  - scotty79 3y ago
    Mostly because time slows as things approach event horizon. I know that in the frame of reference of infalling object everything seems like business as usual but for far away observer (us) nothing ever crossed any event horizon. You can't do away with this problem without dismissing the notion of any well defined simultaneity altogether (which people do, but I believe it's a cop out). As far as I'm concerned there just wasn't enough time since the beginning of the universe for any blackhole to form, from our point of view, because of the infinite time dilatation. And I think our (remote observer) point of view is what counts because most places in the universe are remote observers. If you are interested in the rest of my cosmological beliefs I believe that black holes are primary form of matter, the rest is just a dust between them. I believe that big bang wasn't the beginning of time and space but rather highly energetic event caused by collision of two superdense clusters of trillions of supermassive balckholes. What inflates space is the kinetic energy imparted on the dust by this collision. The mass flies away in all direction with random velocities and the spacetime is "dragged" by it. We all came from the dust swirling between them that got heated by the event to the energies of quark gluon plasma and higher. We are also possibly under the influence of very strong, very long wavelength gravity waves originating from outside of observable universe. Larger remaining chunks of the objects that collided to give birth to our universe might be the source. https://www.researchgate.net/publication/330726290_Confirmation_of_Inflaton-like_Oscillations_in_the_Scale_Factor_from_the_Pantheon_Compilation_of_1048_SNe1a https://www.researchgate.net/publication/330726290_Confirmat...

140 points by gmays 3y ago

api 3y ago

Primordial black holes are a fascinating topic. One of my favorite hypotheses is that "planet nine," a large possibly 1-5 Earth mass planet suggested by some orbital models to exist beyond Neptune and Pluto in the far outer solar system, may be a primordial black hole. If such a thing existed it'd be a black hole about the size of a billiard ball and would be extremely hard to detect. It would not emit Hawking radiation (Hawking temperature still below the CMB), so the only thing it would emit would be when it encountered something and tore it apart. In that case you'd see X-rays, gamma rays, etc., but maybe only briefly. Only way to find it might be to model orbits accurately enough to predict its position and then look for gravitational lensing. If this companion object did exist it'd be a gigantic discovery of huge importance. It'd be within reach of probes, making it possible to study and even do experiments on to investigate things like quantum gravity. It could also be used in tight gravity assist flybys to accelerate probes to incredible velocities, maybe making interstellar probes a lot more practical. It'd be our very own way to yeet stuff to the stars, assuming these things could withstand insane g-forces (so probably not humans unfortunately).

ryandrake 3y ago
> It could also be used in tight gravity assist flybys to accelerate probes to incredible velocities, maybe making interstellar probes a lot more practical. Would 1-5 earth masses really provide enough of a yeet to appreciably affect the speed of a probe? Jupiter is about 300+ earth masses and we're not flinging probes out to stars using him.
- bigyikes 3y ago
  You can get a lot closer to the center of mass of the black hole, which should drastically increase acceleration since it falls off with distance squared.
  - gus_massa 3y ago
    The satelite acelerates when it aproach the planet, but most of it is compensated when it goes away. There is a nice graphic in https://en.wikipedia.org/wiki/Gravity_assist#/media/File:Voyager_2_velocity_vs_distance_from_sun.svg https://en.wikipedia.org/wiki/Gravity_assist#/media/File:Voy...
    - pixl97 3y ago
      You toss off some mass as you pass the black hole and it gives a powerful boost.
      - gus_massa 3y ago
        Do you have a source for that?
        vundercind 3y ago
        Star Trek fans will recognize the name as that of a versatile light starship class often seen acting as science vessels. https://en.m.wikipedia.org/wiki/Oberth_effect https://en.m.wikipedia.org/wiki/Oberth_effect FWIW I’ve read several explanations of why this works, including some confidently claiming that one or more of the others was wrong, and a couple of which kinda made sense as I was reading them, but not a one of them has made a lick of sense to me after I thought about it for a while. Despite all the attempts at understanding it, I still couldn’t tell you why it works (aside from “this math says it does” which is a shit answer) [edit] the other thing you can do, even at the same time is: https://en.m.wikipedia.org/wiki/Gravity_assist https://en.m.wikipedia.org/wiki/Gravity_assist But the specific effect in question seemed to be the Oberth Effect, given the mention of throwing off mass. Gravity assist just relies on the body in question being really heavy and in (orbital, say) motion in some fashion that’s useful to you. Kinda “pulls” you along. You steal a negligible amount of energy from a huge body, which translates into some decent speed for your very-light spacecraft.
        MeImCounting 3y ago
- dooglius 3y ago
  We did, Voyager 1 and 2 used Jupiter to get out of the solar system
  - Sharlin 3y ago
    And the Pioneers and New Horizons too.
caf 3y ago
Assuming you don't go so close that tidal effects tear the probe apart, the g-forces should only be those imposed by the probe's thrusters firing during the assist. When the thrusters aren't firing it's just in free-fall.
- kadoban 3y ago
  Hm, that can't be how that works, can it? How do you get any extra velocity then if there's never any acceleration beyond what your thrusters provide?
  - messe 3y ago
    It's called the Oberth Effect. In short, in Orbital mechanics, burning your thrusters deeper within a gravity well, results in a greater increase in kinetic energy than burning them further out. This is because momentum ~ v, while kinetic energy ~ v^2. If you're travelling faster—as you would be as you approach the black hole and fall deeper and deeper in your orbit—then you can expend to same amount of momentum to receive a disproportionally larger increase in kinetic energy. Because your potential energy falls off with distance to the black hole at the same rate regardless of the speed you're travelling at, your total energy upon escaping the black hole is much larger than it would be had you burned your thrusters outside its gravity well.
    - deleted 3y ago
      [deleted]
    - HeatrayEnjoyer 3y ago
      But you are still burning the same amount of chemical energy...
      - ibeforee 3y ago
        Wikipedia says: In terms of the energies involved, the Oberth effect is more effective at higher speeds because at high speed the propellant has significant kinetic energy in addition to its chemical potential energy.[2]: 204 At higher speed the vehicle is able to employ the greater change (reduction) in kinetic energy of the propellant (as it is exhausted backward and hence at reduced speed and hence reduced kinetic energy) to generate a greater increase in kinetic energy of the vehicle.
Loughla 3y ago
I feel like if you were close enough for a gravity assist, wouldn't the tidal forces just tear the probe apart?
- Tostino 3y ago
  Not necessarily. If you replaced the sun with an equivalent mass black hole, none of the orbits of the planets would change.
  - tsimionescu 3y ago
    Sure, because none of the planets are anywhere near close enough to the sun to experience tidal forces. But if you were to approach the sun VS a sun-mass black hole, at some distance the difference would become noticeable through tidal forces (ignoring the massive difference in emitted radiation, of course).
  - jebarker 3y ago
    I'd like to see a simulation of what that would look like. I mean, if by magic the sun was replaced with an equivalent mass black hole in an instant would anything be visible from earth before the inevitable freeze?
    - utensil4778 3y ago
      From Earth's perspective, you wouldn't see anything interesting except for the sun vanishing. Gravitationally, all that matters is the absolute mass, so all the dynamics of the solar system stay the same. A black hole of 1 solar mass has a radius of something like 3km. Totally invisible from Earth. You probably wouldn't even see any gravitational lensing. All we would see is the sun there one moment, and then nothing the next. Life on Earth would continue for a while, but the planet would eventually freeze over. So, nothing interesting. The sun vanishes and then some time later you freeze and/or starve to death.
      - jebarker 3y ago
sandworm101 3y ago
At that size, very few things would ever get close enough to be torn apart, let alone fall in. We should look for objects suddenly changing course ivo the potential black hole.
perihelions 3y ago
- "In that case you'd see X-rays, gamma rays, etc., but maybe only briefly." One speculative possibility is that we could find a continuous gamma annihilation signal from its dark matter halo, https://arxiv.org/abs/1909.11090 https://arxiv.org/abs/1909.11090 https://hn.algolia.com/?query=What%20If%20Planet%209%20Is%20a%20Primordial%20Black%20Hole%3F&type=story https://hn.algolia.com/?query=What%20If%20Planet%209%20Is%20...

breckenedge 3y ago

I really want primordial black holes to turn out to be the missing antimatter from the Big Bang, but I don’t think that could ever be tested. And of course a mechanism for this would probably need new physics since antimatter interacts the same as normal matter wrt gravity.

deepsun 3y ago
When I asked similar questions physicists, turns out all of them were thought off and tested long time ago. E.g. small black holes would still cause detectable and attributable radiation.
stainablesteel 3y ago
it sounds a lot like it now that i read this, large dispersed amounts of antimatter that apparently doesn't give off light yet has massive gravitational pull
- nullserver 3y ago
  https://youtu.be/qy8MdewY_TY?si=NVZzWJSFXl4EATRK https://youtu.be/qy8MdewY_TY?si=NVZzWJSFXl4EATRK Good video on topic
- ccgreg 3y ago
  Antimatter has the same electrodynamic properties as matter.
pfdietz 3y ago
There were suggestions that the antimatter-matter asymmetry is because antimatter was preferentially segregated into a dense phase of hadronic matter, like quark matter nuggets. This would be interesting because if such nuggets could be found and captured, they'd be a potential source of energy by annihilation with ordinary matter.
- exe34 3y ago
  Spicy nuggets.

woopsn 3y ago

Fascinating mission. I don't understand how microlensing events resulting from primordial black holes can be differentiated even statistically, given that they "can't be formed by any known physical process", but in any case it's exciting to discover there's much more of something up there than we knew. Even if they are "just" rogue planets.

api 3y ago
We have a variety of ways to make insanely precise measurements of light to the point of counting photons. I’m guessing that factors into being able to detect microlensing.

hyperific 3y ago

NASA in the title should be all capital letters as it's an acronym and not a name.

jdminhbg 3y ago
Depends on where you live: https://proofreadingpal.com/proofreading-pulse/writing-guides/us-vs-uk-english-grammar/#:~:text=Acronyms%20(Initialisms%2C%20per%20UK),Nasa%20and%20Unesco%20(UK).&text=Collective%20nouns%2C%20which%20are%20nouns,but%20singular%20in%20US%20English https://proofreadingpal.com/proofreading-pulse/writing-guide....
- ibeforee 3y ago
  nasa.gov is the domain here
- ralferoo 3y ago
  As a Brit, I've never noticed NASA spelt Nasa before, and I'm on the fence about Unesco, not because I recall seeing it title-caps, but because it doesn't look offensive to me. That said, when I googled for the title-caps variants of both words, I saw the Guardian, Independent and Times all used it for Nasa, but only the Guardian and Times seem to use it for Unesco. There was also a page from the NYT that used Unesco, so a counter example from the US, but even the UK government pages refer to it in all caps, as do most other UK articles. I certainly find it a weird generalisation that "UK English" (sic) prefers title-caps, as we tend to like our abbreviated names and pretty much always use all-caps when every letter comes from a separate word, and only title-caps when we use runs of letters from each different word - quango (quasi-NGO), Bakerloo (Baker St-Waterloo), Beeb (compared with BBC), Lib Dems, etc. We also have a few things that aren't consistent for government things - Defra (always used to be DEFRA, but they seem to have rebranded), MOD (always caps), Ofqual (=Office of Qualifications, always title case), Ofcom (=Office of Communications, now seems to officially be title case, but always used to be OFCOM), UCAS (University and Colleges Admission Scheme, always all-caps), etc. Maybe the stylistic choice is based on how pronounceable it is as a word, but whatever I don't think there are any hard and fast rules!

kristianp 3y ago

Launching by May 2027. Was hoping it would be sooner, given the presence of this article, but it seems they drip feed them out gradually. https://science.nasa.gov/mission/roman-space-telescope/ https://science.nasa.gov/mission/roman-space-telescope/

chefkd 3y ago

question for the initiated: why do space agencies divide their resources and attention between different projects? Wouldn't it make sense to focus first on making the moon and it's resources accessible kind of like airplanes then systematically expand to Mars, asteroid belt, and so on instead of spreading out too thin without conquering the closest

macintux 3y ago
Purely speculative: - Betting everything on a single huge project is risky. You wait for years for completion, and if some critical part of the project costs more/takes longer than expected (much like Artemis today) you risk achieving nothing at all. - Small, cheap projects that don't bankrupt the agency if they fail, when they succeed, generate ongoing positive PR and scientific results. NASA famously promoted this concept after one or two expensive projects had problems (of course, not famously enough that I remember more details). - Some of those smaller projects are critical, like climate monitoring. You can't just set aside those sorts of tasks for a literal moonshot. - Smaller projects contribute towards the big ones: NASA has given SpaceX a fair bit of money over the years that is paying off with Starship and Artemis.

mrcwinn 3y ago

What the heck is "Nasa"? Not the sword I'll prefer to fall on, but even if you're in the UK, let's honor that this organization is in the United States and they self-describe as "NASA."

scotty79 3y ago

I believe that most black holes in the universe are primordial. Even most of the star sized ones. And definitely the supermassive ones. But it would be super nice to find the ones with masses that are unexplainable in the current framework.

luyu_wu 3y ago
Why would you believe this? Stars collapse into black holes all the time as long as they're over the threshold mass.
- scotty79 3y ago
  Mostly because time slows as things approach event horizon. I know that in the frame of reference of infalling object everything seems like business as usual but for far away observer (us) nothing ever crossed any event horizon. You can't do away with this problem without dismissing the notion of any well defined simultaneity altogether (which people do, but I believe it's a cop out). As far as I'm concerned there just wasn't enough time since the beginning of the universe for any blackhole to form, from our point of view, because of the infinite time dilatation. And I think our (remote observer) point of view is what counts because most places in the universe are remote observers. If you are interested in the rest of my cosmological beliefs I believe that black holes are primary form of matter, the rest is just a dust between them. I believe that big bang wasn't the beginning of time and space but rather highly energetic event caused by collision of two superdense clusters of trillions of supermassive balckholes. What inflates space is the kinetic energy imparted on the dust by this collision. The mass flies away in all direction with random velocities and the spacetime is "dragged" by it. We all came from the dust swirling between them that got heated by the event to the energies of quark gluon plasma and higher. We are also possibly under the influence of very strong, very long wavelength gravity waves originating from outside of observable universe. Larger remaining chunks of the objects that collided to give birth to our universe might be the source. https://www.researchgate.net/publication/330726290_Confirmation_of_Inflaton-like_Oscillations_in_the_Scale_Factor_from_the_Pantheon_Compilation_of_1048_SNe1a https://www.researchgate.net/publication/330726290_Confirmat...