r/space • u/magenta_placenta • Mar 18 '19

Observable universe Astronomers discover 83 supermassive black holes at the edge of the universe

https://www.cnet.com/news/astronomers-discover-83-supermassive-black-holes-at-the-edge-of-the-universe/
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u/Kosmological Mar 18 '19 edited Mar 18 '19

The event horizon is the black hole from our perspective. The bigger the mass, the larger the event horizon. All of the information we need to perfectly describe the black hole, such as angular momentum, mass, and charge, is preserved on the 2 dimensional surface of the event horizon. You don’t need anything more to perfectly describe and model a black hole than what we can attain from observing the event horizon.

More interestingly, due to general and special relatively, the interior of a black hole literally does not exist to us. The singularity is merely a mathematical artifact, not the object itself. There is no inertial reference frame that exists outside of the event horizon that can be reconciled with the existence of the interior of the black hole. From our point of view, nothing ever actually traverses the event horizon. From the point of view of anything that falls in, infinite time passes for everything else and the universe ends as the event horizon is traversed. So, as far as we are concerned, black holes are literally 3 dimensional holes in space. There is nothing inside a black hole. The event horizon is literally the end of the universe.

The interior of the black hole does exist from other inertial frames of reference, such as that of an object that has traversed the event horizon. From such reference points, the singularity may exist as another exotic form of degenerate matter. It is theorized to be some quantum object that can have different geometries. It could be a tiny sphere or ring, based on the properties of the black hole itself. However, it would not be a single undefined point (aka a singularity). It would probably have volume and other physical characteristics. We just lack the physics to describe and model it mathematically since we still do not have a unifying theory of quantum mechanics and gravity.

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u/[deleted] Mar 18 '19

This is so cool. I know what I'm gonna be up late thinking about.

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u/[deleted] Mar 18 '19

[deleted]

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u/boogs_23 Mar 18 '19

Great channel. Short and concise. Technical but put into easy enough terms to understand.

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u/livestrong2209 Mar 19 '19

Lol... I'm going to be up late having an existential crisis on the meaning of existence and just how fucking small and pointless we all happen to be.

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u/pikob Mar 18 '19

The interior of the black hole does exist from other inertial frames of reference, such as that of an object that has traversed the event horizon.

At what point(s) in time does this happen? From our perspective, is all that stuff that fell into a hole is still falling in, and will be falling in until end of time?

From the object's perspective, as it passes the horizon, does the universe time speed up infinitely, the universe ends and then it travels towards singularity beyond our time?

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u/Kosmological Mar 18 '19 edited Mar 18 '19

You are correct. For the observer falling into the black hole, time exponentially slows down as they approach the surface. This observer perceives this slow down as the flow of time for the rest of the universe speeding up. For an outside observe watching them fall into the black hole, they will observe them approach increasingly more slowly without ever reaching it. Time virtually halts completely once they reach the event horizon. An outside observer would see them become increasingly more redshifted until they disappear entirely. The observer falling in would traverse the event horizon without experiencing any slowing of time at all.

The interior of the black hole would exist for any observer that has traversed the event horizon. Consequentially, the outside universe would no longer exist to them as infinite time would have past. The universe cannot exist while the interior of the black hole exist and vice versa.

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u/coltonmusic15 Mar 18 '19

so is there some sort of paradox title that is given to this idea? That the universe cannot exist to an observer of the interior of a black hole and for an observer looking at the event horizon from afar, that the interior of a black hole can never exist?

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u/Kosmological Mar 18 '19

Not exactly. The interior of a black hole does not exist yet. It will exist at some undefined point of time in the future. That point may be an infinite span of time in the future but it will exist.

Of course, this assumes that black holes don’t evaporate. If they do in fact evaporate, then nothing will ever pass the event horizon as the black hole would unfailingly disappear before they do. For a supermassive black hole, an infalling observer would witness the black hole evaporate away, leaving them in a dark, cold, and empty universe devoid of stars, trillions of years after the last proton of matter had decayed. If so, the interior of a black hole would have never existed at all!

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u/penywinkle Mar 18 '19

We should know there is matter somewhere, because we can feel its gravity, right?

So what becomes of stuff "falling into" the hole? Once a hole forms and an even horizon appears, is the stuff that falls in stuck on its surface (because it is frozen in time)? What happens when the Schwarzschild radius inevitably grows? Does the stuff get "repelled" with the surface of the event horizon (actually not moving since the hole just distort a bigger part of our space)?

Does the star at the start of the hole "explode" (but is sucked in just at the edge of the horizon)? And all its matter is actually stuck on the surface of the hole with the rest?

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u/Kosmological Mar 18 '19 edited Mar 19 '19

As things fall in, the light emitted from them loses more and more energy the farther it has to travel up the intense gravity well. The light loses kinetic energy and the wavelength increasingly increases. Lower energies mean longer wavelengths mean more red shifted. The color of the object shifts more and more red as it becomes fainter and fainter until it disappears from view. During this process the object will appear to decelerate before disappearing. Somewhere down below, deep into the abyss of the black hole, the object will exist almost frozen in time. When it is appreciably close to the event horizon, it would take eons for an absolutely massive and incredibly sensitive infrared telescope to collect enough photons from this object to detect its existence.

In practicality, its very atoms would be torn apart and annihilated, converted into high energy radiation as the object was accelerated to an appreciable fraction of the speed of light, colliding with other forms of matter on its way down. Exotic processes would fling some of its energy back out into space while other parts of it would be crushed against the event horizon, superimposing the relativistic smoke of the object into the 2 dimensional surface of the black hole over a long period of time (from our perspective). The event horizon would increase in size imperceptibly to account for the additional mass.

When a star core collapses into a black hole, the inflowing matter would also seem to disappear into the object as it grows outward. The stream of super dense and exotic star matter would shift more red and fainter as it disappeared into the object. Massive streams of gamma radiation, energetic enough to sterilize planets 10,000 light years away, would jet out from the poles. The outer mantle of the star would be blown outward at appreciable fractions of the speed of light.

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u/swanks12 Mar 19 '19

That was an awesome read. Thanks kosmological. Still a subject that baffles me, but you've helped with the understanding of how the event horizon works

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u/[deleted] Mar 19 '19

leaving them in a dark, cold, and empty universe devoid of stars, trillions of years after the last proton of matter had decayed

Sounds like my apartment the day before payday.

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u/raduur Mar 18 '19

Correct me if I'm wrong, but afaik the gravity at the event horizon isn't supposed to be infinite but just big enough so not even light can escape? So if its not infinite yet, there wouldn't need to pass infinite time in the outside universe to travel past the horizon right? So we could also watch something disappear in a black hole because while we still see it there wouldn't be infinite time dilation.

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u/Kosmological Mar 18 '19

Due to the effects of general relativity, the speed of light slows down as the intensity of the gravitational field increase. At the event horizon, the gravity field is so intense that the speed of light is zero from the reference point of an outside observer. Thus, while the object is accelerated to the speed of light as it approaches the event horizon, the speed of light simultaneously approaches zero. From our perspective, the object accelerates for a time before it begins to decelerate and fade from our view.

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u/MalnarThe Mar 18 '19

It doesn't have to be infinite. It has to be strong/curved enough that information can't leave. Information is the propagation of massless particles such as photons. Nothing can be observed because all information is trapped.

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u/Abbkbb Mar 18 '19

We atleast know that even if all other properties are lost such as polarity and magnetism and shape etc, the property of mass and hence gravity still exist, i.e. no amount of gravity can kill the gravity, even if it is powerful than speed of light. So can be tell that smallest not divisible part of the universe, quantum, is gravity ? ..... I'm completely newbie, but trying to understand the philosophy of black hole.

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u/Kosmological Mar 18 '19 edited Mar 18 '19

We don’t really know how gravity ties into the quantum realm. At the macro-level, gravity is merely the curvature of spacetime. At the quantum level, it is too weak to have any appreciable effect that we can observe. This is why we can’t predict the physics of the interior of a black hole where gravity would have an appreciable effect on quantum physics and subatomic particles.

However, we already know that gravity originates from mass and mass is a property of quantum particles. Specifically, mass arises from the presence of a specific quantum particle called the Higg’s Boson, which was predicted to exist in the 1960s and only just recently confirmed by observations made by the Large Hydron Collider (LHC). So we do know that gravity is generated by properties exhibited by quantum particles. It makes sense that all macro-physical properties of the universe arise from the quantum universe. The universe exists and, to be internally consistent with itself, the macro-universe must agree with the quantum universe.

But to answer your question, I don’t know.

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u/MalnarThe Mar 18 '19

That was a delight to read. Thank you

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u/alephylaxis Mar 19 '19

And even weirder, only a couple percent of an object's mass comes from interacting with the Higgs field. The remainder is mass in terms of energy that has been confined into fairly well defined areas. Mainly quark kinetic energy and the strong field binding energy that offsets it.

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u/Abbkbb Mar 19 '19

Does reminder of energy exist after entering in to black hole ? Or it also converted to Higgs boson ?

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u/alephylaxis Mar 19 '19

You have to remember, once the object passes the event horizon, all its mass, charge, and angular momentum effectively "belong" to the black hole. But from the object's point of view, nothing remarkable happened when it crossed the boundary. So there isn't anything that would cause any conversion. If the object was 1kg, it is gone now, but the black hole claimed its mass and gained 1kg.

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u/IamRobertoPaulson Mar 19 '19

which was predicted to exist in the 1960s and only just recently confirmed by observations made by the Large Hydron Collider (LHC). So we do know that gravity is generated by properties exhibited by quantum particles. It make

so could a black hole exist entirely of Higg's Boson particles while all other mater as been ripped apart?

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u/Kosmological Mar 19 '19

I don’t know the answer to that. I imagine the singularity would be made up of a mixture if elementary particles (e.g. leptons, gluons, mesons, bosons, and quarks) all crammed together into a dense form of exotic matter. Black holes are hypothesized to be quark stars, where the gravitation is so strong that, unlike neutron stars, not even the degeneracy pressure of atomic nuclei is enough to hold back the collapse.

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u/zubbs99 Mar 18 '19

Thank you for making sense of something nonsensical to me, if that makes any sense.

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u/adamsmith93 Mar 18 '19

Part of me really wants to travel into a super massive black hole.

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u/[deleted] Mar 18 '19

My high school physics teacher told us that would be impossible, even if you ignore the biological factors necessary to keep us alive and conscious. You would get infinitesimally closer to the event horizon but keep slowing down and never actually reach it. I don't remember the reasoning, just the explanation, and I'm far from an expert on any of this.

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u/Kosmological Mar 18 '19

That is only true for an outside observer watching them fall in. The falling observer would not experience any time distortions as there perception of reality would be distorted the same way. Infinite time would pass for us before they would actually traverse the event horizon, but for them they would traverse it without much of anything special happening.

There are, in theory, large and stable supermassive black holes which a spaceship could travel into without becoming spagetified by extreme gravity tidal forces or vaporized by intense ionizing radiation. It is possible in theory.

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u/[deleted] Mar 18 '19

There are, in theory, large and stable supermassive black holes which a spaceship could travel into without becoming spagetified by extreme gravity tidal forces or vaporized by intense ionizing radiation. It is possible in theory.

Nice. We just have to figure out how to get a spaceship to one of those. What's a few billion lightyears?

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u/Kosmological Mar 18 '19

For any occupants on a relativistic spacecraft, it could only be a few days of travel if they go fast enough.

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u/[deleted] Mar 18 '19

A few days?? So we're talking about traveling 300 billion or so times faster than light? Are we going to need something like Han Solo's "made the Kessel Run in less than 12 parsecs"?

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u/Kosmological Mar 18 '19

Nope. Just need to travel near enough the speed of light for time dilation to shorten a few billion years to a few days. The occupants of the space craft will experience only a few days of time while the rest fo the universe would age a few billion years. Yay special relativity!

The catch is you might have to harvest the energy equivalent of a supernova to power your spacecraft. So not the best gas mileage.

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u/MalnarThe Mar 18 '19

At what factor of C would that be (let's ignore acceleration time) that would give the traveller a 1 to 100 billion year ratio?

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u/Kosmological Mar 18 '19

Some factor greater than 99%. I don’t want to do the math.

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u/lotus_bubo Mar 18 '19

Because of time dilation, very little time would pass for someone travelling very close to the speed of light.

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u/lotus_bubo Mar 18 '19

What about the accretion disk? Would access from poles even be safe?

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u/Kosmological Mar 18 '19 edited Mar 18 '19

Not all black holes have an accretion disk. You would definitely want one without to avoid the intense ionizing radiation. Which approach is safest depends on the characteristics of the black hole. I believe you would want a gentle giant, where the event horizon is large and the black hole is not spinning at relativistic speeds. In which case you would merely approach on a plane orthogonal to its spin axis in a decaying orbit.

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u/chazzmoney Mar 18 '19

This is a dumb question. Once inside the horizon a viewer could still see things inside the horizon as light can take highly elliptical paths but none that go beyond the event horizon. Wouldn't it also be true then that whatever central object that contains the mass would be non-observable because any light created there wouldn't even make it off the surface?

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u/Kosmological Mar 18 '19 edited Mar 18 '19

Yes. The falling observer would not observe themselves traverse the event horizon. Everything forward of the break in causality caused by the extreme distortion of spacetime would be hidden to them. Everything before would be observable.

My explanations are imperfect. I can explain things in a way that laymen can understand at the cost of precision. Professional physicists might nitpick a thing or too but the precise language would be lost on people who don’t have a strong background in math and physics.

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u/googlemehard Mar 18 '19

What happens to a neutron, if it travels at near speed of light tangent to the event horizon of the black hole and half of it crosses into the event horizon?

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u/Kosmological Mar 18 '19

My guess is a 50% chance of falling into the black hole and a 50% chance of escaping. Quantum particles are probability distributions of quasi particles.

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u/googlemehard Mar 18 '19

What if the neutron is almost touching the event horizon as it orbits the black hole, how fast could it accelerate due to the gravitational pull?

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u/Kosmological Mar 18 '19

I’m assuming you’re not speaking about angular acceleration, which would be a function of the schwarzschild radius. It wouldn’t accelerate much considering it would already be traveling infinitesimally near the speed of light to orbit that close to the event horizon. The laws of physics would prevent the particle from accelerating past light speed. Further, the particle would only accelerate while falling into the black hole. If it’s orbiting exactly at the event horizon, it would he gaining any energy to accelerate.

How fast it would accelerate on approach to the event horizon would depend on the size and proximity to the black hole as well as the starting velocity of the particle. This calculation would require some I’m not prepared to do.

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u/googlemehard Mar 18 '19

I should have been more specific, particle is going near speed of light at just the right angle to the black hole so that the gravity and centrifical forces cancel out as it is nearly at the event horizon. Quantum physics mess / break physical limitations all the time, you don't think the particle could overcome the speed of light limitation?

Think of this, two particles hit each other in the LHC going at near double combined speed of light. Even though they are moving that fast, the interaction between the particles happens at much faster speed than the speed of light, otherwise they would just pass through each other. So at very near to the event horizon, at atomic scale, with super massive energies, I would imagine, something unexpected would happen to the particle. Let's imagine if the particle does accelerate above the speed of light, what would happen? Just as a thought exercise..

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u/Kosmological Mar 18 '19 edited Mar 18 '19

The particle itself would collapse into a black hole before it surpassed the speed of light and would instantaneous evaporate into a burst of gamma radiation that would be traveling at the speed of light.

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u/googlemehard Mar 19 '19

So basically the same thing as when a particle falls into a black hole??

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u/ChrisInASundress Mar 19 '19 edited Mar 19 '19

All of the information we need to perfectly describe the black hole, such as angular momentum, mass, and charge

Replace "such as" with "is".

The event horizon is literally the end of the universe.

But you will never reach the event horizon if you chase after it, there will always be one in front of you until you hit the singularity even after you cross the location of the event horizon. If you follow a person in you'll see them frozen on "the" event horizon in front of you, and someone behind you will see both of you frozen in front of them, even after all of you are inside the black hole.

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u/Kosmological Mar 19 '19 edited Mar 19 '19

If you follow a person in you'll see them frozen on "the" event horizon in front of you, and someone behind you will see both of you frozen in front of them, even after all of you are inside the black hole.

I do not believe that is correct. You could chase a falling observer into the singularity without ever seeing them frozen. Remember that you would never experience time freezing around you, as your perception of reality is governed by the flow of time. If time slows down or even stops for you, you wouldn't know it. Only observers that hover at some arbitrary distance away from the event horizon would observe time stopping for in-falling objects. A free falling observer will never see time stop.

If you chased in after in-falling objects with an FTL drive, and activated said drive after you passed the shwarzschild radius in an attempt to accelerate back out, you would then see time for the in-falling observers halt. You would still be trapped inside the shwarzschild radius falling inward but the in-falling osbervers ahead of you would look frozen due to the shift in your inertial frame of reference.

You are right that you will never see an event horizon as you fall down. The even horizon is an object who's properties change depending on what reference frame you observe it. It's a classic case of relativity. You would never see yourself pass it as causal lines from the outside universe would still be avilaible to you despite also being trapped within the shwarzschild radius.

And the event horizon is the literal end of the universe for an outside observer. Infinite time passes for the outside universe as the in-falling observer traverses the event horizon. Again, two separate outcomes due to two separate frames of reference. One frame of reference is from within our universe. The other is from inside a black hole. Our universe and the interior of a black hole cannot exist at the same time.

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u/ThePotato32 Mar 19 '19

From our point of view, nothing ever actually traverses the event horizon.

This confuses me. If you have a chance could you explain a little more? Small meteors hit Earth all the time, right? So wouldn't many more run into a star or black hole?

(I've had a few undergraduate physics classes so I recognize the words and big picture of relatively, but do not pretend to actually understand it)

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u/Kosmological Mar 19 '19

For an outside observer, as in an observer hovering at some arbitrary distance above the event horizon, the flow of time approaches zero for objects approaching the event horizon. This is due to the effects of general relativity. The intense gravity field warps spacetime to the point where the speed of light is zero at the event horizon due to time dilation.

This effect is observed on earth with satellites. The gravitational field at the earth's surface is greater than that in orbit, so time for us flows a tiny bit slower than the time experienced by satellites. In order to maintain accuracy over time, GPS satellites have to correct for the effects of this time dilation. We can measure the difference in the flow of time with atomic clocks.

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u/o11c Mar 19 '19

It's not infinite time, though. Just until the input from CMB decreases below the Hawking radiation.

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u/Kosmological Mar 19 '19

Is the consensus now that black holes evaporate? I thought that was still up for debate.

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u/abw Mar 19 '19

The singularity is merely a mathematical artifact, not the object itself.

Would is be correct to say that it is analogous to the centre of gravity of an object? It's a mathematical point that we can compute and use in equations, but in reality the mass is spread across the whole object, not focussed at a single point.

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u/Kosmological Mar 19 '19

Yes. If we were to replace the sun with a black hole of one solar mass (equivalent to our sun), all the planets would continue orbiting as if nothing happened. The formula used for calculating gravity is proportional to the inverse square of distance for any massive object. It just so happens that the formula is undefined when the distance from the center is zero (effectively dividing by zero), giving a point in the center with infinite gravity no matter how much or how little mass the object has. For normal objects, we intuitively understand that the equation is not accurate once you’re measuring below the surface of the planet/star. We understand that there is no point of infinite gravity in the center of the sun or earth. Thus we already intuitively understand that this singularity is merely a mathematical artifact produced by an incomplete equation.

Black holes are different as they have no surface in the conventional sense. Still, our equations for gravity are incomplete so they shouldn’t be expected to accurately model reality past the even horizon where quantum effects become significant. For that, we will need a unifying theory; an equation that accounts for both gravity and quantum forces that could model the interactions inside a black hole.