Physics anyone?

[rickyarbino]

Danrev,
We can't observe them. Otherwise they wouldn't be "black holes". The term is used because light cannot reflect back to us as the escape velocity is greater than the speed of light which is at maximum in space, making them completely black.




But Magma, I was thinking about what you wrote just then.
Not necessarily a question to you, but more of a thought experiment perhaps.
If we were to create a black hole, and it was highly dense, to the point that earth would be completely within its Event Horizon, what would happen? We'd be pulled in, but would we be destroyed? I figured we wouldn't be since there would be no gravitational difference to tear us apart.
I guess we still wouldn't be able to see very much of the singularity itself because of the black-ness, but what do you guys think?

[Phigure]

if we were to create a black hole, and it was highly dense, to the point that earth would be completely within its Event Horizon, what would happen? We'd be pulled in, but would we be destroyed? I figured we wouldn't be since there would be no gravitational difference to tear us apart.
I guess we still wouldn't be able to see very much of the singularity itself because of the black-ness, but what do you guys think?

i think your understanding of a black hole is a bit flawed. it sounds like you're thinking of it in terms of something like an actual "hole"

in the simplest terms - it's really just a very very very massive object. and with large mass, comes a lot of gravity, which compresses this object. in a black hole, there's a singularity where all the matter in the black hole exists at a point of 0 volume, ergo infinite density.

so basically, if you were to just "pop" a black hole into existence around the earth, it would simply become part of the singularity and be compressed to infinity.

sometimes when supernovas collapse, what they leave behind is so dense that it crushes the matter so much that it breaks down into neutrons and forms a neutron star. the density of a singularity is infinite, so the matter of the earth wouldn't just stop breaking down there, it would break down into the fundamental fermions that make up all matter. and it wouldn't stop there. however we don't actually know what would happen past that, since a singularity can't be observed.

i guess that answers your question of whether the earth would be "destroyed". in the simplest terms, yes. if you want to get technical though, you can ask if the physical information "encoded" in the earth is destroyed upon being absorbed by the singularity

to which i, nor anyone else, do not know the answer
https://en.wikipedia.org/wiki/Black_hol ... on_paradox

It's quite likely we've already created small black holes at CERN and almost certainly will when the powers are ramped up on re-opening - they're too fleeting to be useful for much (apart from confusing everyone over the nature of black holes and their ability to disappear) though. The problem with intentionally keeping one for any length of time even if we could is that it could feasibly swallow the Earth unless it was somehow shielded... black holes are probably the most dangerous phenomenon in the Universe - almost every way of investigating something that doesn't involve interrogating a local black hole is probably preferable!

yeah that whole media circus about black holes at the LHC was cringeworthy

but it's absolutely not true that there have likely been black holes created at the LHC. the amount of energy required to produce a micro black hole would be 10^16 tera electronvolts. the LHC runs/ran at a relatively pathetic 7 TeV. In 2015 it'll start running at 14 TeV. we're talking hundreds of trillions of times as much to create a black hole

even if we somehow were capable of harnessing and focusing that much energy, we wouldn't even be able to intentionally keep one around if we wanted to. as we know, black holes release hawking radiation. they "evaporate" through giving off this radiation. the rate of evaporation is inversely related to the mass of the black hole. such a black hole would be so small (we're talking pretty much a little above planck length) that the rate of evaporation would be so high that you wouldn't even be able to "feed" it more matter before it evaporated

[rickyarbino]

I'm aware that it isn't literally a hole, but admittedly I'm by no means an expert on the matter.
What I didn't know is that matter was broken down, I guess this is obvious given that singularities are just single points in spacetime, but I don't think I have a very good mental grasp of that to begin with and I doubt that this serves as enough reason to say obviously. Which explains my reaction to the Smolin black holes earlier on in here.

I did click through to that link to get a better Idea of what you mean by information, do you mean matter is effectively energy - I doubt this as it must be conserved mustn't it? Or how for example a the matter which an object consists of being arranged into said object? Or something else entirely?

[Phigure]

but I don't think I have a very good mental grasp of that to begin with

don't worry man, i don't think there's anyone on earth that can fully grasp the idea of a singularity. it's just such an abstract, completely irrational concept, you know? zero volume, yet infinite density? and then once once you start thinking about the relativistic effects of a singularity... makes my head hurt already

I did click through to that link to get a better Idea of what you mean by information, do you mean matter is effectively energy - I doubt this as it must be conserved mustn't it? Or how for example a the matter which an object consists of being arranged into said object? Or something else entirely?

actually, the black hole information paradox isn't related to conservation of mass and energy. energy and mass are conserved in a black hole. however, for quantum mechanical reasons that i can barely even begin to comprehend, there is what effectively amounts to a "law of conservation of information". that wikipedia page i linked basically explains possible ways that this paradox is avoided

since you asked though, yes, matter is effectively energy. that's the basic principle of e=mc^2 . matter can be converted to energy, and energy can be converted to matter. if you've ever wondered, that's also why masses of elementary particles are measured in electrovolts (like the Higgs boson at ~125 GeV), rather than a unit of mass, because the values of mass would be a pain in the ass (like 2.228327×10^-22 g for the Higgs).

Or how for example a the matter which an object consists of being arranged into said object? Or something else entirely?

care to clarify? i don't quite understand the question

[rickyarbino]

Without wanting to bastardise energy-mass equivalence too much, I'm getting at the way energy is organised into things. Like DNA for making genes, or the intermolecular bonds that 'hold substances together'.

So the fact that a ball is a ball for example, all the factors which give that ball it's shape, bounce, mass, texture etc. the 'instructions' for creating something.

But I guess it wouldn't be that either on second thought since it is destroyed to begin with. I kinda feel like that isn't really a 'thing' anyway

[Phigure]

i sort of see what youre getting at with that. the ball analogy is actually pretty close in a lot of ways

i guess this is a little weird of a way to explain it, but try to bear with me. Strictly metaphorically, imagine the universe as a computer or information processing device. In this information processing device, the laws of physics, which govern how everything the universe interacts, are basically like functions with various input variables and then a solution. the information being referred to here is somewhat like all those various variables. according to the fairly widely accepted standard model of particle physics, all matter, energy, and even force is the result of a select number of fundamental particles (i can elaborate on that if you're interested). so the "information" would be things like those particles' velocities, spins, charges, etc.

and so this is the paradox: once these particles enter the singularity, they lose this information. according to what we know based on quantum mechanics, that shouldn't be possible. Which is why people hypothesize about potential ways for this information to be conserved in some way

[scspkr99]

I have a lot of love for this thread but fuck all to add so thanks.

[magma]

It's quite likely we've already created small black holes at CERN and almost certainly will when the powers are ramped up on re-opening - they're too fleeting to be useful for much (apart from confusing everyone over the nature of black holes and their ability to disappear) though. The problem with intentionally keeping one for any length of time even if we could is that it could feasibly swallow the Earth unless it was somehow shielded... black holes are probably the most dangerous phenomenon in the Universe - almost every way of investigating something that doesn't involve interrogating a local black hole is probably preferable!

yeah that whole media circus about black holes at the LHC was cringeworthy

but it's absolutely not true that there have likely been black holes created at the LHC. the amount of energy required to produce a micro black hole would be 10^16 tera electronvolts. the LHC runs/ran at a relatively pathetic 7 TeV. In 2015 it'll start running at 14 TeV. we're talking hundreds of trillions of times as much to create a black hole

even if we somehow were capable of harnessing and focusing that much energy, we wouldn't even be able to intentionally keep one around if we wanted to. as we know, black holes release hawking radiation. they "evaporate" through giving off this radiation. the rate of evaporation is inversely related to the mass of the black hole. such a black hole would be so small (we're talking pretty much a little above planck length) that the rate of evaporation would be so high that you wouldn't even be able to "feed" it more matter before it evaporated

I'm trying to find the article, but I read something in the last couple of weeks that shed a bit of doubt on the energies required... it might've been a fair bit lower, though it would still be a bit of a stretch for the LHC. Maybe I dreamt it...

Thanks for the Hawking radiation explanation - I've been struggling to work out how a black hole could logically evaporate for ages.

[rickyarbino]

i sort of see what youre getting at with that. the ball analogy is actually pretty close in a lot of ways

i guess this is a little weird of a way to explain it, but try to bear with me. Strictly metaphorically, imagine the universe as a computer or information processing device. In this information processing device, the laws of physics, which govern how everything the universe interacts, are basically like functions with various input variables and then a solution. the information being referred to here is somewhat like all those various variables. according to the fairly widely accepted standard model of particle physics, all matter, energy, and even force is the result of a select number of fundamental particles (i can elaborate on that if you're interested). so the "information" would be things like those particles' velocities, spins, charges, etc.

and so this is the paradox: once these particles enter the singularity, they lose this information. according to what we know based on quantum mechanics, that shouldn't be possible. Which is why people hypothesize about potential ways for this information to be conserved in some way

Does that extend to the way they interact with each other?

Reminds me of something I stumbled upon while "revising". I was watching an Intro to the EPR paradox video, and if I recall correctly it said that matter and it's respective anti-matter are always in 'contact' with each other so that their their 'upward and downward' spin can never be determined. Would that be encoded too?

[SignalRecon]

Wow... page 9

Phil you are clearly passionate about the subject matter. Did you major in Physics or are you an extremely well read enthusiast?

[rickyarbino]

He's a physics major.

[Phigure]

@Magma ah well I'll have to look into that, if the energy required was really within our reach then that would have some really cool implications. I imagine there could be a lot to learn from being able to create black holes and studying them closely

i sort of see what youre getting at with that. the ball analogy is actually pretty close in a lot of ways

i guess this is a little weird of a way to explain it, but try to bear with me. Strictly metaphorically, imagine the universe as a computer or information processing device. In this information processing device, the laws of physics, which govern how everything the universe interacts, are basically like functions with various input variables and then a solution. the information being referred to here is somewhat like all those various variables. according to the fairly widely accepted standard model of particle physics, all matter, energy, and even force is the result of a select number of fundamental particles (i can elaborate on that if you're interested). so the "information" would be things like those particles' velocities, spins, charges, etc.

and so this is the paradox: once these particles enter the singularity, they lose this information. according to what we know based on quantum mechanics, that shouldn't be possible. Which is why people hypothesize about potential ways for this information to be conserved in some way

Does that extend to the way they interact with each other?

Reminds me of something I stumbled upon while "revising". I was watching an Intro to the EPR paradox video, and if I recall correctly it said that matter and it's respective anti-matter are always in 'contact' with each other so that their their 'upward and downward' spin can never be determined. Would that be encoded too?

Yes, according to the standard model, all interactions between matter (which happen through the weak force, strong force, electromagnetic force, and gravity) are actually mitigated by particles. W and Z bosons for the weak force, gluons for the strong force, photons for the electromagnetic, and, in theory, gravitons for gravity (gravitons have not been observed yet, but then again, neither was the Higgs until last year).

The way I understand the EPR paradox is referring to entangled particles (the entanglement is is the "contact" you're talking about), and when you measure the one of the properties of one particle (like the spin), the property of the other becomes undeterminable. The crazy thing is that "information" carried through this entanglement has actually been ovserved to travel at several thousand times the speed of light ( http://www.fromquarkstoquasars.com/chin ... anglement/ )! There are a couple different ways of resolving the paradox, some of which involve "hidden" variables. If this is the case, then yes, such information is also encoded in these particles, and would theoretically be lost upon entering the singularity.



And yeah, I'm a physics major, but I'm actually only in my first year still. I've always geeked out on this sort of stuff though. So yeah, I suppose I'm more of a well read enthusiast, on my way to the next level

[rickyarbino]

So earlier today, I was "revising" again and I stumbled into a SixtysSymbols video on "The Biggest thing in the Universe".

That isn't particularly relevant, but it got me thinking about black holes again, and Smolin's theory of them "creating" or perhaps sustaining, universes. The question is, can black holes "absorb" space?



...
Hold it, I went back and looked up his theory and it seems like he doesn't actually say that they create them, so much as them being portals to them.

The question still stands though.

[Phigure]

massive objects deform the "fabric" of spacetime around them like this:


and in the case of a black hole, it's something like this:


as you approach the singularity, the fabric of spacetime is effectively being pulled in so much that light can't "outrun" it. sort of analogous to trying to run on a treadmill set to max speed, at a certain point you just can't keep up enough to escape it.

at the singularity, we don't actually 100% know what's going on, but basically the fabric of spacetime would be being pulled and deformed to an infinite extent, and the concepts of space and time as we know them break down. "absorb space" can be interpreted a few different ways, but in this sense i suppose you could say they do

[kay]

I would say they don't absorb space (or perhaps spacetime might be a better term) as such, they just deform spacetime to the extent that our current theories and mathematical frameworks breakdown and are unable to describe what occurs within them.

[rickyarbino]

I feel like I'm about to ask a question with an obvious answer, but why is space-time deformed like that and not in all directions?

Is it just that the diagram isn't able to accurately represent what occurs in 'other' dimensions?

[Phigure]

Yeah pretty much, it's just a rough visual representation in terms of a single, 2 dimensional plane

This is probably a better one


But really it's a lot more complex than that still, since we're talking about all of spacetime and not just the three spatial dimensions we're so familiar with

[alphacat]

I like the old sheet-stretched-taut analogy, even if it's allegorical by merit of being 2D.



And in this example, we could effectively refer to a black hole as an object that's so "heavy" (dense) that it punctures the sheet in that spot, and anything rolling around on the sheet that gets within the funnel-shaped indentation ending in the puncture effectively disappears from the sheet.

[hifi]

[kay]

I like the old sheet-stretched-taut analogy, even if it's allegorical by merit of being 2D.



And in this example, we could effectively refer to a black hole as an object that's so "heavy" (dense) that it punctures the sheet in that spot, and anything rolling around on the sheet that gets within the funnel-shaped indentation ending in the puncture effectively disappears from the sheet.

I'm not convinced a puncture actually occurs. The apparent singularity only occurs because we do not have the right physics/mathematical framework to describe what goes on beyond that asymptotic point.