The jets are 23 million light years in length! That's 140 milky way galaxies laid out -- these are sizes I can't even begin to comprehend
Imagine the amount of energy required to create a jet that large! The scales are so big, it makes me wonder if there isn’t an upper limit to energy density. How much energy can be in one spot before you inadvertently create a Big Bang?
> it makes me wonder if there isn’t an upper limit to energy density
Yes, in a sense. The point at which the energy bends space-time into a black hole.
Actually, in theory there is one place denser but our models show it can never happen.
The moment right after the big bang. As energy can never be created nor destroyed, all the energy in the universe was practically in one point in space-time a femtosecond after the big bang.
This is a misunderstanding. All the energy in our « observable » universe was compressed in that small size. We do not have any estimates of the size of the actual universe now, nor at a time shortly after Big Bang. For all we know, the universe might be infinite, both now and back then.
My layman understanding is that we don't have the theories or math to try and understand this so it's just a black box that we pretend to understand
The whole concept of the Big Bang is a mind warp. The whole explosion must have happened in some… space-time thing to begin with. What was that immense point of matter and energy in? What was “around” it? We’ll never know.
It wasn't an explosion. Space itself expanded, so there wasn't anything to expand into. https://en.wikipedia.org/wiki/Expansion_of_the_universe
I think there are some philosophical definitions in the way. The Universe is everything we know, it is made of space and time, so of course it cannot expand into any space as it contains all of it.
We don't know what's outside the Universe, so we can't say there is nothing, and we can't say there's anything, we don't know what it is expanding into, or if "expansion" even makes sense outside the Universe. If we somehow find out what's outside the known Universe, that will inevitably become part of the known Universe, so we will never know what's outside the Universe.
Consider a bubble rising to the surface of a pond. As the bubble breaches the surface, it extends beyond the surface and expands as the pressure reduces.
If you consider the surface of the water as a 2D plane, the bubble expands into a third dimension perpendicular to the others. The bubble's surface is made of the same water as the surface of the pond, and there is no hard boundary between them. The bubble pushes part of the 2D plane into the third dimension, which results in the water having more surface area than the total possible area of the 2D plane.
Area (space) has been created without creating matter or energy. The surface is simply extended into an extra spatial dimension.
The way I like to interpret the big bang is as a higher dimensional structure folding or knotting itself such that a bubble is forced into a 3D space. The bubble expands and thus creates more volume than is possible in the lower-dimensional surface the bubble was formed on. This is my ill-informed interpenetration of M-theory.
Dunno why, but much of mathematics and the universe in general makes much more sense to me when viewed in terms of dimensionality. Our universe is 'just' a 4D slice of a higher dimensional structure, and I find a certain kind of beauty in that. In another life, I'd have been a string theorist
Instead of thinking of it as a bang in an existing space-time, the way to conceptualize it is the collapsing of a universal wave function from a superposition of all possible universal states. Of which our universe is just one potential possibility. Space time is a function of the collapsing state.
I think I understand that to a certain extent. But where does the universal wave function exist to begin with? There must be some construct it exists within.
Why? I would look at Occam’s razor, believing there must be an outer layer (or a creator of god) just leads to an infinite regress. It’s much more likely that the thing is just eternal according to that logic
One word, AGI
At that moment, why didn't the entire [mass of the] universe collapse into a black hole?
Perhaps gravity evolved.
I’m a layman but I think I’ve understood this enough to repeat. The early universe is hypothesized to have been so uniform (gravity pulling in every direction) there was no net direction for anything to collapse to. Because the expansion was so quick, before the uniformity could be ruined due to quantum randomness, it expanded away from there being tons of or one giant black hole.
You also must remember the universe was always infinite (in this model). So for every particle there were particles in every direction from them, ie the universe not a point or point like because points have edges. It was (much much) denser, but still infinite and expanding from all regions.
That's a question that I always also asked myself, from my layman understanding space time expanded quicker than gravitational collapse
Yes and it was never a point, it was just much much denser but still infinite. And so uniform there was no net direction for collapse before expansion took over.
Since there are conserved quantities like energy and angular momentum it is impossible that everything just collapses. If something collapses, there is usually a large amount of matter which does not collapse to carry away the energy and momentum of the collapsing stuff.
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For comparison that's almost 10 times the distance to the Andromeda galaxy (2.5m ly).
Imagine a one meter long jet. Congratulations, you've begun to comprehend it and now are at 1/(2.176 × 1023) of the total length.
10^23 is actually easy to comprehend, because it’s close to the amount of h2o molecules in a syringe. Just that many meters.
Pretty crazy!
If the plasma jet is wildly larger than our entire galaxy, I wonder if some sort of exotic life could evolve inside the jet. Some sort of life that would be totally rare in the universe.
Sometimes I wonder if our whole universe is some kind of transient aberration, if you zoom out far enough
For all we know, we live inside some large scale invisible jet and our entire understand of physics is really the exception rather than the rule
if you zoom out far enough, there's no other option (imo)
We are little critters living in space squirts
Not my field, but could the Big Bang have been a massive black hole that "spat" out jets of plasma that formed into new stars and galaxies? I call this the black hole big burp theory.
This is very close to an idea known as "Black hole cosmology" -- basically the idea being that the visible universe is inside a black hole, leading to a sort of "nested multiverse".
https://en.wikipedia.org/wiki/Black-hole_cosmology
A related theory, rather than being inside a black hole, is that the other side of a black hole is a "white hole". As matter collapses into a black hole, it is emitted from the white hole, creating another universe.
Here's an article from 2010 that expands on the idea, though this is definitely not the first time (or last time) it was discussed, it just happens to be an easily searchable article.
https://www.space.com/8293-universe-born-black-hole-theory.h...
I'm sure it's not practical, but I always thought it would be interesting if instead of living "inside" a black hole, the visible universe was simply being consumed by a black hole so large it just encompassed everything outside the visible part. So no nesting, the universe just eventually gets consumed entirely by one black hole.
Unsure if the math actually checks out on this, but I was told that if you add up the observable mass/energy in our universe with the same average density we see now, you get a black hole with a Swarzchild radius around the size as the observable universe.
One could then quite reasonably argue that our universe is indeed inside or is itself a black hole.
In this "universe is inside a black hole" theory, is mass 1-to-1 with the "parent" universe? In this theory, are we inside a black hole containing billions of galaxies worth of matter?
An average black hole has 50 suns in it, 50 times the mass of our star, that would be a universe without much matter.
To preface, this is not my field (space stuff is just an interest of mine), and this specific theory is more on the fringes than most so I haven't spent a significant amount of time thinking about it.
>is mass 1-to-1 with the "parent" universe? In this theory, are we inside a black hole containing billions of galaxies worth of matter?
My understanding of the theory is that the proposed parent black hole which our universe is inside would necessarily have to contain all of the mass that we detect in our observable universe. So our universe would be 1-to-1 mass of the parent black hole. The parent universe would be larger (and may contain many black holes, each with a nested universe).
>An average black hole has 50 suns in it, 50 times the mass of our star, that would be a universe without much matter
Indeed! It's interesting to think that perhaps we are on one of the "lowest" layers of the nested multiverse, and perhaps there are only a few dozen (or whatever) layers below us until there is too little mass in that universe to create any more black holes. However, there could be an infinite amount of layers "above" us.
I am curious to where the 50 solar-mass figure comes from, though. Is this excluding super-massive and ultra-massive black holes (which are on the order of 10^6 to 10^11 solar masses)? My intuition says 50 solar-masses is orders of magnitude too low for the average mass of a black hole, but I've never really looked into it
Wow, thanks for the resources! I actually never heard of a living universe 'inside' a black hole.
Wait a minute, I missed the discussion
This seems incompatible with inflation
Isn't universe inflation already on shaky ground though? https://www.scientificamerican.com/article/cosmic-inflation-...
Interesting read. Her proposal for a “bounce” cosmology sounds like it has a neat explanation for why things appear smooth, but as far as why/how the universe should bounce at all (especially given current consensus that the current universe will NOT bounce) are only briefly gestured at (“promising recent work”, to paraphrase).
Has that work developed and found traction among physicists in the 7 years since the article?
This was on the front page a couple weeks back iirc: https://www.livescience.com/physics-mathematics/dark-matter/...
Interesting! It would be nice to solve dark matter & excise inflation in one stroke (or a few strokes). My lay understanding of PBHs—as-dark-matter is that it has been whittled down to a pretty tight range of their masses, though, bounded by “they would’ve already evaporated” and “we’d already have detected them”
You are getting a single plastid. No more, no less.
> I wonder if some sort of exotic life could evolve
Some might say humans are exotic life that evolved.
The referenced paper: https://www.nature.com/articles/s41586-024-07879-y
Just think... in the presence of a constant magnetic field, this could be the most powerful particle collider in the visible universe
I thought that only hawking radiation could escape a black hole. Now a paper describing a vast jet of emitted plasma??
The article doesn't quite clarify this point. It mentions the jets shooting from below and above the black holes, but does this mean they're emerging from their interior or being created by the accretion of superheated material that forms in orbit around black holes?
The article simple states this, which seems wrong given the immense gravity of black holes:
>When supermassive black holes become active—in other words, when their immense forces of gravity tug on and heat up surrounding material—they are thought to either emit energy in the form of radiation or jets.
So the holes themselves emit energy jets or their accretion disks do? Sloppy damn phrasing and reporting, and all too common for science subjects.
Its not coming out of the black hole itself, its more like the black hole has an accretion disk around it of material that is being sucked in. The dynamics of the huge forces and energies involved can cause jets to form, throwing high energy particles away from the black hole. The jets still represent a tiny fraction of the matter, most of which is still heading into the hole.
And crazy strong and twisted magnetic fields that will heat things up/create large forces on charged particles.
Hawking radiation is one process, but for spinning black holes, especially ones with accretion disks and magnetic fields around them, there are two more theoretical predictions: the Blandford–Znajek process and the Penrose process.
https://en.m.wikipedia.org/wiki/Astrophysical_jet#Rotation_a...
> I thought that only hawking radiation could escape a black hole.
I think this is likely a misconception too. Hawking radiation does not come from inside a black hole, it comes from the event horizon. A virtual particle/anti-particle pair is created close enough to the event horizon that one of them falls in and the other escapes. This means the origin is outside the hole!
Similar story with jets. They're created by the interactions of matter as it falls towards the black hole (gaining energy), but before it actually falls inside.
You may have heard that a black hole is the most efficient way to convert matter to energy apart from antimatter annihilation. This is that.
In the accretion disk, friction and collision between fragments, molecules, atoms cause things to reach incredible temperatures. The matter gets so incredibly hot that the radiation it emits is actually enough to offset the black hole's gravity and prevents more matter falling in faster. The innermost section of the disk is so ludicrously hot that matter dissociates into subatomic particles and becomes a plasma. This plasma is very energetic and moves very fast and creates a very strong magnetic field. This interacts with the electric field produced by the black hole. This plus the stupendous distortion of spacetime caused by the black hole's rotation causes the magnetic fields to twist up tightly in a vortex about the axis of rotation.
Again, the energies involved are impossibly huge. We're converting matter into energy at something like 95% efficiency. Just through gravity!
Because the plasma is so highly charged, the magnetic vortices are so powerful, and the twist is so tight, it essentially creates a particle accelerator on a galactic scale. Plasma from the accretion disk is sucked into the vortex by the insane magnetic fields. Particles spin round and round in the vortex until they get as close to light speed as is possible. The vortex also confines the jet into a cone, blasting out charged particles with impossible velocities along the axis of rotation.
These jets convert matter into pretty much every kind of energy. Radiation across the entire spectrum, lightspeed particles, magnetic and electric fields. It's really impossible to overstate just how much energy these things throw out. It's just a few degrees shy of a sustained matter/antimatter reaction on stellar scales running for millenia.
These things can extinguish entire galaxies. Not sterilize, extinguish. They can blast away any free gas in a galaxy, immediately and irrevocably halting star and planet formation. Not even just in the host galaxy. Exceptionally powerful quasars can extinguish galaxies lightyears away.
And again, this is only driven by gravity. Nothing else. All of the impossibly huge energies are produced by nothing more than matter falling into a gravity well.
If you track down the original source, there's a video of the lead author of the Nature paper explaining how it works:
https://www.caltech.edu/about/news/gargantuan-black-hole-jet...
Truly, what kind of pedants would downvote an honest question about this poorly described detail?
I've seen people say "you're not supposed to mention" downvotes if they happen to you, but when they're plainly stupid?
I have a question about black holes, HN.
Let’s say you have a black hole. You fire a laser beam straight into it. Just by symmetry, shouldn’t it blueshift on the way in, gain some preposterous amount of energy — enough that it can escape?
> shouldn’t it blueshift on the way in, gain some preposterous amount of energy — enough that it can escape
You're devilishly close to the Penrose process by which "energy can be extracted from a rotating black hole" [1]. (You can also make them explode [2].)
Light travels in a straight line - black holes don't "pull" light in, they change what a straight line looks like in the space around it.
The event horizon is the distance where all straight lines lead to the black hole.
It will gain energy.
There _is_ no amount of energy it could gain to escape though. It goes no faster, gets no closer to escape. It just splats into the black hole and we'll never see it again no matter how much energy it started with or gained.
From an outside observer, the black hole is finite in width though, though. and if the speed of light is constant, isnt that a contradiction? Or is a black hole somehow of infinite width?
It's not a contradiction because the path of the light enters the black hole event horizon but does not come back out.
All paths end at the ~center of the black hole. We don't really know what's there, at the so-called singularity at the center, it may be impossible to know. But it's probably something that light can hit and stop existing, or even if it can't it'll be stuck there in some way or another.
We know that the gravity (warping of spacetime) around a black hole is such that it cannot escape, even at light speed. What happens inside is less sure, but largely moot because none of it can ever affect anything outside of the event horizon ever again.
(Hawking Radiation or something else may make this technically a lie, but it's close enough to the truth to last a few trillion years)
It is finite in circumference, yes, but its geometry is not the usual geometry so diameter does not equal circumference divided by pi.
It must be infinite then?
Maybe. Nobody really knows what happens at the center. General relativity I believe says "yes", but nobody knows how true it is in the case of ~infinitely dense crap in an infinitely small spot. Usually "infinite" means what really happens is not captured by the model, but nobody has a better answer yet as far as I know.
A better answer would be something like a grand unified theory of gravity and the other forces, including quantum effects, which doesn't exist. It's like the holy grail of physics, you'd be the next Einstein if you figure it out.
Yes.
> Just by symmetry, shouldn’t it blueshift on the way in, gain some preposterous amount of energy — enough that it can escape?
Escape requires a certain critical speed (escape velocity), and light always travels at the speed of light regardless of it's energy, so light's ability to escape a black hole is not energy dependent. At some radius (the event horizon), space itself falls into a black hole faster than the speed of light, and that's sets a hard limit on everything's ability to escape.
Past the event horizon physics get weird. Time becomes finite and ends for all observers at a point in the future called the singularity. Everything falls towards this point, gaining preposterous amounts of energy. "Preposterous" here means infinite energy, and infinite density, really just a whole lot of infinities. Those infinities are problematic, and mean there's probably something non-infinite and uniquely interesting going on in there, but since nothing can escape the event horizon we'll likely never know.
Here’s something else that I’m concerned with with about black holes. If a mass is one nanogram below that of a black hole, how similar is it to a black hole?
Yes, but only if the black hole is rotating. Fortunately, all known black holes do rotate.
There's a concept for using exactly this idea for interstellar propulsion. You fire a laser around a black hole, it gains energy, then hits you, imparting more kinetic energy than you spent firing the laser.
In essence, you're executing a gravity slingshot with photons.
You might enjoy the Halo Drive idea [0]. From my (very layman) understanding this uses this principle for propelling a spacecraft - you just need a moving black hole nearby :)
And to think that we witness this from the comfort of our pocket sized terminals makes me happy, but also sad that maybe mankind will not reach spacefaring… great filter and all… dunno
I’ve seen stellar engines [1] show up in fiction.
Has anyone done a galactic engine?
John C. Wright in the Count to the Escaton sequence. But it's just part of the background of awesome while the real people story plays out in the foreground (as it should)
What happens to the plasma that the black hole spits out? Do they have any ideas?
I studied these objects for my first research paper in grad school. (You can see a few images of some of the objects I found in Figure 3 of my paper [1]) In essence the jet blows a hot bubble into the gas that comprises the intracluster medium of the galaxy cluster. Over time synchrotron radiation causes the bubble to cool down and eventually (maybe on the order of a few 100 million to a billion years if I recall right) the bubble comes into thermal equilibrium with the surrounding gas.
I think it just blasts off into the universe
Panspermia?
slows, cools, condenses into us sometimes
Is it possible for these jets to hit other galaxies/stars/planets?
Yes. A poweful enough quasar can halt star formation in nearby galaxies by blasting away free gas.
Most quasars emit enough gamma radiation to sterilize all of space within a hundred lightyears or so.
Very exciting until they figure out the jet is just a Starlink satellite passing in front of the telescope.
One hell of a thruster.
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