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Black holes are an excellent example for so called "cognitive metaphors". Because we found no better analogy, we named them "holes" despite the fact that they

by oevi 9y ago

Black holes are an excellent example for so called "cognitive metaphors". Because we found no better analogy, we named them "holes" despite the fact that they are basically the opposite: an object with enormous mass. This influences our thinking and our language when we discuss problems concerning black holes. We talk about "inside the black hole", "light cannot escape the black hole" or "spitting things out of the black hole". I think it is really interesting how these cognitive metaphors can sometime limit our ability to think about a problem, because they often restrict the properties of the described thing to the properties of the analogy.

westoncb 9y ago
I think this is something that deserves much greater general awareness. I think by default we're pretty unaware of the kind of analogizing/metaphoring that takes place when we conceptualize anything—but it's completely pervasive. I see it as a kind of subtle 'dust on the lens' of the microscope which we use to observe things generally. It's an (in a certain sense) inescapable artifact due to the fact the we conceptualize with a definite thing with its own properties and quirks and limitations, which is the human brain. Anyway, I see it as a kind of 'bias' (best I can think of atm, but that term isn't really broad enough to capture the idea) which we could watch for and in doing so make gains in objectivity. Edit: also, another way of looking at it is: when we express any concepts in some concrete form, the particular representation we choose (and we have to choose something) brings its own baggage along with it. And, subsequently, we end up reasoning off of the baggage rather than the thing in itself.
- dalbasal 9y ago
  One that I think comes up often is the robots/automation metaphor. Technology has reduced 90% or more of farm labour needs, multiplied industrial output many times, etc. We've seen a lot of automation, but it's been vague economics. When we think back on these things, we see technology, tools, & machines like tractors and looms. When we look forward we see robots and automation. Practically this has 2 effects. First, we come back with a Jetsons lime picture, everything is the same as a regular hotel but the maid is a robot, the front desk is an ATM, the barman is a robot arm and the resteraunt is a Japanese conveyor belt. Robots are human shaped metaphors for technology, placeholders for unknowns. Second, we think in terms of replacement. In reality, it's really more like efficiency. A tractor still uses a farmer, but requires a lot less time and effort to get a field ploughed. Again, there's a difference in how we think when looking back or forward.
4ad 9y ago
No, black holes are topological holes. It's a mathematical abstraction, not merely a cognitive metaphor.
- akvadrako 9y ago
  I'm pretty sure every "mathematical abstraction" is a "cognitive metaphor".
  - 4ad 9y ago
    I don't know what a cognitive metaphor is and whether it's applicable to mathematical abstractions. I was responding to the claim that: > Because we found no better analogy, we named them "holes" despite the fact that they are basically the opposite Which is false.
  - leetcrew 9y ago
    if you are unaware, this is extremely controversial. https://en.wikipedia.org/wiki/Philosophy_of_mathematics#Mathematical_realism https://en.wikipedia.org/wiki/Philosophy_of_mathematics#Math...
  - dsacco 9y ago
    No, not really. Symmetries of an n-gon (a 2-dimensional figure with n sides) are just permutations of the n numbers representing the sides. A cognitive metaphor is to call certain types of symmetries “rotations” or “reflections”, because we can’t really describe all symmetries through a metaphor like that. The symmetries are not literally operated by picking up your figure and flipping it over. On the other hand, mathematical abstractions of dimensionality not cognitive metaphors. A “hole” is a meaningful topological abstraction in various dimensions that corresponds to what we consider a colloquial “hole” in 3-dimensional space. If I tell you a Klein bottle is a bottle that has only one surface (no inside or outside) without any “hole”, I’m not making a metaphor, I’m describing a 4-dimensional object as closely as I can describe a mug or a vase in 3-dimensional space. Just because I’m not defining it through pure mathematics and we can’t immediately visualize it (in entirety) doesn’t mean it is a cognitive metaphor, because it perfectly corresponds to the actual concept of dimensionality (instead of being a clever figurative description of it). Similarly, if we geometrically represent a black hole we can clearly see the curvature of space (from one angle), leading down to an event horizon, within which is a singularity. This representation corresponds to rolling a coin at an angle down a curvature, watching it spin at the bottom a bunch of times, then fall in. In fact, a shuttle falling out of orbit down to the event horizon would look just like this as it entered the whirl zoom of a black hole, before the unstable orbit failed and it just fell in. Even further, there is a very cogent, topological sense of what “within” means here. Just as you can fall into a manhole in the middle of the street, you can fall into the event horizon of a black hole. If we represent a street as a 2-dimensional plane, a manhole in the street is the topological space in the plane that has no points - a mathematical hole. In three dimensions, a jelly donut has a topological hole, and the hole is also 3-dimensional (the missing points would be representable as 3-dimensional vectors). Information theoretically speaking, the inside of a black hole’s event horizon does not exist - it’s strictly an absence that we can only reason about heuristically. It would be a cognitive metaphor for me to say that we can only reason about the inside of the event horizon in the same way we can reason about the middle of a donut that tastes like nothing because there is “no donut”. But it is not a cognitive metaphor to call the black hole a “hole”, because fundamentally and literally it acts like one. The singularity inside the black hole is not a hole, but that’s different. Our common sense of what it means to be a hole is literally described by the mathematical abstraction of a hole. When mathematical abstractions are actually just literal abstractions of what we already understand, they’re not cognitive metaphors. If you’d like an example of a cognitive metaphor insead of a pure abstraction, look at string theory. While our common sense of a hole literally corresponds to its 3-dimensional topological abstraction, our common sense of what we call a “string” has no precise mathematical correspondence. A string in the common sense of the word is a 3-dimensional object that is very long and thin. A string in the mathematical/physical sense is a one dimensional object, like a line. To call it a string is to invoke an intuition of something like a small thread that in some sense seems “barely” 3-dimensional.
zrb05293 9y ago
So for example is it more accurate to say that things fall...on to...rather than in to a black hole? That’s fascinating!
- colechristensen 9y ago
  Eh, that's taking it too far as the parent does. "Hole" and "in" are pretty good metaphors for what a black hole is. It's hard to have any particularly accurate metaphors for what a black hole is because time dilation, the speed of light, curved space, etc. just aren't a part of life for any humans.
mrleiter 9y ago
Very true. Although not specifically in this context, Ludwig Wittgenstein said:"The limits of my language mean the limits of my world."
blackrock 9y ago
I would prefer if black holes were called "Dark Stars". Because that really is what they are. A weird star that is so massive, its gravitational field distorted the fabric of its local space, that not even light can escape it. It is theoretically possible that the black hole is still performing fusion, and emitting light and heat, like a regular star. But its gravitational field is so intense, that even light cannot escape it. So, from the outside, the black hole appears dark. Hence, a dark star. Perhaps if you are inside the Event Horizon of the black hole, then you can still see the light from the fusion of the star. But if you are outside of the Event Horizon, then you will only see the star as pitch black, since light can't even escape it.
- JumpCrisscross 9y ago
  > then you will only see the star as pitch black, since light can't even escape it Would it be black? Right above the event horizon is flaming relativistic matter.
  - chopin 9y ago
    That's true but afaik time dilation makes it rather dim infrared radiation.
    - Retra 9y ago
      On the inner-most layer, yes. But outside of that, it will be less dim and less infrared.
- qubex 9y ago
  The term “Dark Star” actually predates the term “Black Hole” by a very long margin (first recorded usage 1783) [0] for classical Newtonian objects whose mass is so large that the escape velocity at their surface exceeds the finite speed of light. Black Holes are very different beasts (self-sustaining concentrations of space-time curvature), despite their popular explanation as being “objects so massive space cannot escape”. It’s extremely improbable that any “classical” (non exotic-quantum) processes are going on within the horizon because it’s very clear that the strength of the gravitational field would far exceed the hydrostatic pressure generated by fusion reactions. It far exceeds the degeneracy forces that prevent neutron stars from collapsing further under their own mass. [0] https://en.wikipedia.org/wiki/Dark_star_(Newtonian_mechanics) https://en.wikipedia.org/wiki/Dark_star_(Newtonian_mechanics...
chrisweekly 9y ago
Great comment -- but while I agree w/ your point about metaphors, I respectfully mildly disagree about this one in particular. For context, I associate it with the popular analogy of timespace as an elastic "sheet" of sorts, with marble-like objects resting on (and sinking into) its surface, with their mass dictating how "deep" their gravity "well" is. With that metaphor in mind, black holes really do approximate holes in the sheet.
- thathappened 9y ago
  But even how we illustrate a sheet of spacetime we show it dip when it should stay flat and pinch, closing the gap between atoms as they get more dense. All of these inaccurate descriptions assume we have the concept already in mind to recursively look up. Describing more accurately let's the reader get a clearer picture and thats where real concepts get conceived. I like heavy/dark star/planet for a vague description. I also think the fact that humans rely on visuals now and we can't get more than a single angle of one of these we can show anyone a 3D view of how it's not just nothing.
- nsxwolf 9y ago
  I don't like the elastic sheet analogy because it doesn't work without gravity, the very thing it's attempting to explain.
  - chias 9y ago
    I like it because it isn't quite as self-referential as it at first seems: the notion of gravity that it requires is not the notion of gravity it is explaining: it uses the colloquial and accessible idea of gravity (i.e. "things fall downwards") to describe a more precise idea of gravity (i.e. "things fall towards each other in accordance with mass").
  - atilaneves 9y ago
    This has always bothered me as well, and I'm surprised that this is the first time I've seen anyone else mention it!
pvg 9y ago
Is it really an [excellent] example of that? We don't use much of the language we use for holes in general for 'black holes'. The term may have been influenced by 'Black hole of Calcutta', itself a metaphorical use.
qubex 9y ago
On the topic of how languages and metaphors affect (and might even form the fundamental substrate of) our thinking, I highly recommend Douglas Hofstadter (he of Godel, Escher, Bach fame) 's book Surfaces and Essences (2010).
Sir_Cmpwn 9y ago
"Hole" is accurate. The "object" with enormous mass would be the singularity, whereas "black hole" refers to the nature of spacetime near the singularity, for which "hole" is an apt name from our reference frame. Also, we don't talk about "spitting things out of the black hole".
dragonwriter 9y ago
> Because we found no better analogy, we named them "holes" despite the fact that they are basically the opposite: an object with enormous mass. Strictly speaking, the defining character is enormous density, not mass. And the black hole is arguably a name for an effect of the object, not the object itself; the object itself is (or is in the process of becoming; verb tenses get weird when time gets weird) infinitesimally small, but the “black hole” generally refers to the space bounded by the event horizon.
- Santosh83 9y ago
  A black hole can literally be considered severely warped spacetime. The high gravity is a consequence of the severe warping, and as for the internal contents, they don't matter to external observers and physics (so far) has very little to say about it.
dahart 9y ago
> Because we found no better analogy, we named them "holes" Are you sure about that? This sounds specious. This requires knowing who named them and why. It sounds like a logical explanation, but history and human events don't follow logic and can't be derived. > We talk about [...] "light cannot escape the black hole" So, light not escaping certain "dark stars" was observed and was a concept before "black hole" was a term. "Dark stars" is one term they were called before the term "black hole". http://curious.astro.cornell.edu/about-us/86-the-universe/black-holes-and-quasars/general-questions/439-who-came-up-with-the-name-black-hole-beginner http://curious.astro.cornell.edu/about-us/86-the-universe/bl... Wikipedia says the name black hole was adopted because it was catchy, which is not because of the value of the analogy. "Dark star" might be a better analogy, and it existed before black hole. https://en.m.wikipedia.org/wiki/Black_hole#Etymology https://en.m.wikipedia.org/wiki/Black_hole#Etymology Having said that, black holes are actually black, and they are literally gravity holes in space. A hole in the ground on earth is only a hole because of gravity, it's a thing you can fall into. Because black holes are things you can fall into if you get too close, because it's doing the exact same thing as a hole in the ground, I'd argue that black hole is not a very good example of a cognitive metaphor. Note also that the best way to demonstrate the intuitive effect of gravity is to show how it acts like a hole. A black hole visualized the same way is a very, very deep pit. https://youtu.be/MTY1Kje0yLg https://youtu.be/MTY1Kje0yLg
- InclinedPlane 9y ago
  Neither dark star nor black hole are apt "models" for the objects. These are phenomena of space-time, not just of gravity. Light cannot escape a black hole because escaping a black hole is impossible. And it's impossible because the space-time inside an event horizon has no trajectories that go forward in time which go farther away from the singularity. Black holes are like pocket universes with one-way roads connecting them to our Universe, this is why light doesn't leave the inside of the event horizon, the path between there and here only goes one way, unlike the rest of space-time. "Dark star" is also a misleading term in that it implies the object is a star or something physical at all. In fact to us it doesn't matter what the object is inside the black hole, and its structure is essentially unknown to us (at present), because we can't interact with it. We can only interact with the space-time phenomenon that it created, the event horizon.
dsacco 9y ago
> Because we found no better analogy, we named them "holes" despite the fact that they are basically the opposite: an object with enormous mass. No, they actually are holes. We don’t need analogies or metaphors to describe black holes. Their mathematical properties are quite complicated to define and we have to reason about what happens around or inside them using figurative thought experiments, but their action does correspond to our intuitive sense of what a hole is. In particular, a black hole consists of an event horizon, around which various stable and unstable orbits are possible, and within which is a theoretical singularity. The event horizon perfectly corresponds to the mathematical concept of a hole, which is a pure abstraction of our common sense of a hole, not a metaphor. A hole is a lack of points in a dimensional space, which means everything inside the event horizon is as much a hole as a manhole in a street is a hole (information theoretically speaking, the inside of a black hole is nothing). To say a black hole is a hole is not a cognitive metaphor, because space around the event horizon actually does curve down to something that is a physical hole. Instead, here are two examples of cognitive metaphors: 1. A donut is a 3-dimensional space with a topological hole in the middle of it. Suppose I define the mathematical properties of taste and equip it as the only sense you have for investigation. Then the hole of a donut tastes like nothing because it is nothing, in the same sense that we can know nothing about the inside of a black hole because it is nothing. 2. Roll a quarter at an angle down a spherical curvature with a hole in the center. The quarter will gradually descend down the curvature, with each revolution about the center happening faster and faster. Finally, it will simply drop it. This is analogous to deteriorating your orbit around a black hole, until you enter various unstable orbits and finally fall into the event horizon. Obviously these cognitive metaphors, while instructive, are imperfect. For instance, we can see a quarter drop into the hole, but we’d never actually see a shuttle fall into the event horizon. On the other hand, the event horizon is a hole in the same sense that a manhole is a hole. Comparing it to a manhole is another cognitive metaphor; calling it a hole isn’t, because it is one.
- nikofeyn 9y ago
  does it make sense to you that a "hole" has mass, electric charge, and angular momentum and is completely characterized by these properties?

by oevi 9y ago

westoncb 9y ago

I think this is something that deserves much greater general awareness. I think by default we're pretty unaware of the kind of analogizing/metaphoring that takes place when we conceptualize anything—but it's completely pervasive. I see it as a kind of subtle 'dust on the lens' of the microscope which we use to observe things generally. It's an (in a certain sense) inescapable artifact due to the fact the we conceptualize with a definite thing with its own properties and quirks and limitations, which is the human brain. Anyway, I see it as a kind of 'bias' (best I can think of atm, but that term isn't really broad enough to capture the idea) which we could watch for and in doing so make gains in objectivity. Edit: also, another way of looking at it is: when we express any concepts in some concrete form, the particular representation we choose (and we have to choose something) brings its own baggage along with it. And, subsequently, we end up reasoning off of the baggage rather than the thing in itself.

dalbasal 9y ago
One that I think comes up often is the robots/automation metaphor. Technology has reduced 90% or more of farm labour needs, multiplied industrial output many times, etc. We've seen a lot of automation, but it's been vague economics. When we think back on these things, we see technology, tools, & machines like tractors and looms. When we look forward we see robots and automation. Practically this has 2 effects. First, we come back with a Jetsons lime picture, everything is the same as a regular hotel but the maid is a robot, the front desk is an ATM, the barman is a robot arm and the resteraunt is a Japanese conveyor belt. Robots are human shaped metaphors for technology, placeholders for unknowns. Second, we think in terms of replacement. In reality, it's really more like efficiency. A tractor still uses a farmer, but requires a lot less time and effort to get a field ploughed. Again, there's a difference in how we think when looking back or forward.

4ad 9y ago

No, black holes are topological holes. It's a mathematical abstraction, not merely a cognitive metaphor.

akvadrako 9y ago
I'm pretty sure every "mathematical abstraction" is a "cognitive metaphor".
- 4ad 9y ago
  I don't know what a cognitive metaphor is and whether it's applicable to mathematical abstractions. I was responding to the claim that: > Because we found no better analogy, we named them "holes" despite the fact that they are basically the opposite Which is false.
- leetcrew 9y ago
  if you are unaware, this is extremely controversial. https://en.wikipedia.org/wiki/Philosophy_of_mathematics#Mathematical_realism https://en.wikipedia.org/wiki/Philosophy_of_mathematics#Math...
- dsacco 9y ago
  No, not really. Symmetries of an n-gon (a 2-dimensional figure with n sides) are just permutations of the n numbers representing the sides. A cognitive metaphor is to call certain types of symmetries “rotations” or “reflections”, because we can’t really describe all symmetries through a metaphor like that. The symmetries are not literally operated by picking up your figure and flipping it over. On the other hand, mathematical abstractions of dimensionality not cognitive metaphors. A “hole” is a meaningful topological abstraction in various dimensions that corresponds to what we consider a colloquial “hole” in 3-dimensional space. If I tell you a Klein bottle is a bottle that has only one surface (no inside or outside) without any “hole”, I’m not making a metaphor, I’m describing a 4-dimensional object as closely as I can describe a mug or a vase in 3-dimensional space. Just because I’m not defining it through pure mathematics and we can’t immediately visualize it (in entirety) doesn’t mean it is a cognitive metaphor, because it perfectly corresponds to the actual concept of dimensionality (instead of being a clever figurative description of it). Similarly, if we geometrically represent a black hole we can clearly see the curvature of space (from one angle), leading down to an event horizon, within which is a singularity. This representation corresponds to rolling a coin at an angle down a curvature, watching it spin at the bottom a bunch of times, then fall in. In fact, a shuttle falling out of orbit down to the event horizon would look just like this as it entered the whirl zoom of a black hole, before the unstable orbit failed and it just fell in. Even further, there is a very cogent, topological sense of what “within” means here. Just as you can fall into a manhole in the middle of the street, you can fall into the event horizon of a black hole. If we represent a street as a 2-dimensional plane, a manhole in the street is the topological space in the plane that has no points - a mathematical hole. In three dimensions, a jelly donut has a topological hole, and the hole is also 3-dimensional (the missing points would be representable as 3-dimensional vectors). Information theoretically speaking, the inside of a black hole’s event horizon does not exist - it’s strictly an absence that we can only reason about heuristically. It would be a cognitive metaphor for me to say that we can only reason about the inside of the event horizon in the same way we can reason about the middle of a donut that tastes like nothing because there is “no donut”. But it is not a cognitive metaphor to call the black hole a “hole”, because fundamentally and literally it acts like one. The singularity inside the black hole is not a hole, but that’s different. Our common sense of what it means to be a hole is literally described by the mathematical abstraction of a hole. When mathematical abstractions are actually just literal abstractions of what we already understand, they’re not cognitive metaphors. If you’d like an example of a cognitive metaphor insead of a pure abstraction, look at string theory. While our common sense of a hole literally corresponds to its 3-dimensional topological abstraction, our common sense of what we call a “string” has no precise mathematical correspondence. A string in the common sense of the word is a 3-dimensional object that is very long and thin. A string in the mathematical/physical sense is a one dimensional object, like a line. To call it a string is to invoke an intuition of something like a small thread that in some sense seems “barely” 3-dimensional.

zrb05293 9y ago

So for example is it more accurate to say that things fall...on to...rather than in to a black hole? That’s fascinating!

colechristensen 9y ago
Eh, that's taking it too far as the parent does. "Hole" and "in" are pretty good metaphors for what a black hole is. It's hard to have any particularly accurate metaphors for what a black hole is because time dilation, the speed of light, curved space, etc. just aren't a part of life for any humans.

mrleiter 9y ago

Very true. Although not specifically in this context, Ludwig Wittgenstein said:"The limits of my language mean the limits of my world."

blackrock 9y ago

I would prefer if black holes were called "Dark Stars". Because that really is what they are. A weird star that is so massive, its gravitational field distorted the fabric of its local space, that not even light can escape it. It is theoretically possible that the black hole is still performing fusion, and emitting light and heat, like a regular star. But its gravitational field is so intense, that even light cannot escape it. So, from the outside, the black hole appears dark. Hence, a dark star. Perhaps if you are inside the Event Horizon of the black hole, then you can still see the light from the fusion of the star. But if you are outside of the Event Horizon, then you will only see the star as pitch black, since light can't even escape it.

JumpCrisscross 9y ago
> then you will only see the star as pitch black, since light can't even escape it Would it be black? Right above the event horizon is flaming relativistic matter.
- chopin 9y ago
  That's true but afaik time dilation makes it rather dim infrared radiation.
  - Retra 9y ago
    On the inner-most layer, yes. But outside of that, it will be less dim and less infrared.
qubex 9y ago
The term “Dark Star” actually predates the term “Black Hole” by a very long margin (first recorded usage 1783) [0] for classical Newtonian objects whose mass is so large that the escape velocity at their surface exceeds the finite speed of light. Black Holes are very different beasts (self-sustaining concentrations of space-time curvature), despite their popular explanation as being “objects so massive space cannot escape”. It’s extremely improbable that any “classical” (non exotic-quantum) processes are going on within the horizon because it’s very clear that the strength of the gravitational field would far exceed the hydrostatic pressure generated by fusion reactions. It far exceeds the degeneracy forces that prevent neutron stars from collapsing further under their own mass. [0] https://en.wikipedia.org/wiki/Dark_star_(Newtonian_mechanics) https://en.wikipedia.org/wiki/Dark_star_(Newtonian_mechanics...

chrisweekly 9y ago

Great comment -- but while I agree w/ your point about metaphors, I respectfully mildly disagree about this one in particular. For context, I associate it with the popular analogy of timespace as an elastic "sheet" of sorts, with marble-like objects resting on (and sinking into) its surface, with their mass dictating how "deep" their gravity "well" is. With that metaphor in mind, black holes really do approximate holes in the sheet.

thathappened 9y ago
But even how we illustrate a sheet of spacetime we show it dip when it should stay flat and pinch, closing the gap between atoms as they get more dense. All of these inaccurate descriptions assume we have the concept already in mind to recursively look up. Describing more accurately let's the reader get a clearer picture and thats where real concepts get conceived. I like heavy/dark star/planet for a vague description. I also think the fact that humans rely on visuals now and we can't get more than a single angle of one of these we can show anyone a 3D view of how it's not just nothing.
nsxwolf 9y ago
I don't like the elastic sheet analogy because it doesn't work without gravity, the very thing it's attempting to explain.
- chias 9y ago
  I like it because it isn't quite as self-referential as it at first seems: the notion of gravity that it requires is not the notion of gravity it is explaining: it uses the colloquial and accessible idea of gravity (i.e. "things fall downwards") to describe a more precise idea of gravity (i.e. "things fall towards each other in accordance with mass").
- atilaneves 9y ago
  This has always bothered me as well, and I'm surprised that this is the first time I've seen anyone else mention it!

pvg 9y ago

Is it really an [excellent] example of that? We don't use much of the language we use for holes in general for 'black holes'. The term may have been influenced by 'Black hole of Calcutta', itself a metaphorical use.

qubex 9y ago

On the topic of how languages and metaphors affect (and might even form the fundamental substrate of) our thinking, I highly recommend Douglas Hofstadter (he of Godel, Escher, Bach fame) 's book Surfaces and Essences (2010).

Sir_Cmpwn 9y ago

"Hole" is accurate. The "object" with enormous mass would be the singularity, whereas "black hole" refers to the nature of spacetime near the singularity, for which "hole" is an apt name from our reference frame. Also, we don't talk about "spitting things out of the black hole".

dragonwriter 9y ago

> Because we found no better analogy, we named them "holes" despite the fact that they are basically the opposite: an object with enormous mass. Strictly speaking, the defining character is enormous density, not mass. And the black hole is arguably a name for an effect of the object, not the object itself; the object itself is (or is in the process of becoming; verb tenses get weird when time gets weird) infinitesimally small, but the “black hole” generally refers to the space bounded by the event horizon.

Santosh83 9y ago
A black hole can literally be considered severely warped spacetime. The high gravity is a consequence of the severe warping, and as for the internal contents, they don't matter to external observers and physics (so far) has very little to say about it.

dahart 9y ago

> Because we found no better analogy, we named them "holes" Are you sure about that? This sounds specious. This requires knowing who named them and why. It sounds like a logical explanation, but history and human events don't follow logic and can't be derived. > We talk about [...] "light cannot escape the black hole" So, light not escaping certain "dark stars" was observed and was a concept before "black hole" was a term. "Dark stars" is one term they were called before the term "black hole". http://curious.astro.cornell.edu/about-us/86-the-universe/black-holes-and-quasars/general-questions/439-who-came-up-with-the-name-black-hole-beginner http://curious.astro.cornell.edu/about-us/86-the-universe/bl... Wikipedia says the name black hole was adopted because it was catchy, which is not because of the value of the analogy. "Dark star" might be a better analogy, and it existed before black hole. https://en.m.wikipedia.org/wiki/Black_hole#Etymology https://en.m.wikipedia.org/wiki/Black_hole#Etymology Having said that, black holes are actually black, and they are literally gravity holes in space. A hole in the ground on earth is only a hole because of gravity, it's a thing you can fall into. Because black holes are things you can fall into if you get too close, because it's doing the exact same thing as a hole in the ground, I'd argue that black hole is not a very good example of a cognitive metaphor. Note also that the best way to demonstrate the intuitive effect of gravity is to show how it acts like a hole. A black hole visualized the same way is a very, very deep pit. https://youtu.be/MTY1Kje0yLg https://youtu.be/MTY1Kje0yLg

InclinedPlane 9y ago
Neither dark star nor black hole are apt "models" for the objects. These are phenomena of space-time, not just of gravity. Light cannot escape a black hole because escaping a black hole is impossible. And it's impossible because the space-time inside an event horizon has no trajectories that go forward in time which go farther away from the singularity. Black holes are like pocket universes with one-way roads connecting them to our Universe, this is why light doesn't leave the inside of the event horizon, the path between there and here only goes one way, unlike the rest of space-time. "Dark star" is also a misleading term in that it implies the object is a star or something physical at all. In fact to us it doesn't matter what the object is inside the black hole, and its structure is essentially unknown to us (at present), because we can't interact with it. We can only interact with the space-time phenomenon that it created, the event horizon.

dsacco 9y ago

> Because we found no better analogy, we named them "holes" despite the fact that they are basically the opposite: an object with enormous mass. No, they actually are holes. We don’t need analogies or metaphors to describe black holes. Their mathematical properties are quite complicated to define and we have to reason about what happens around or inside them using figurative thought experiments, but their action does correspond to our intuitive sense of what a hole is. In particular, a black hole consists of an event horizon, around which various stable and unstable orbits are possible, and within which is a theoretical singularity. The event horizon perfectly corresponds to the mathematical concept of a hole, which is a pure abstraction of our common sense of a hole, not a metaphor. A hole is a lack of points in a dimensional space, which means everything inside the event horizon is as much a hole as a manhole in a street is a hole (information theoretically speaking, the inside of a black hole is nothing). To say a black hole is a hole is not a cognitive metaphor, because space around the event horizon actually does curve down to something that is a physical hole. Instead, here are two examples of cognitive metaphors: 1. A donut is a 3-dimensional space with a topological hole in the middle of it. Suppose I define the mathematical properties of taste and equip it as the only sense you have for investigation. Then the hole of a donut tastes like nothing because it is nothing, in the same sense that we can know nothing about the inside of a black hole because it is nothing. 2. Roll a quarter at an angle down a spherical curvature with a hole in the center. The quarter will gradually descend down the curvature, with each revolution about the center happening faster and faster. Finally, it will simply drop it. This is analogous to deteriorating your orbit around a black hole, until you enter various unstable orbits and finally fall into the event horizon. Obviously these cognitive metaphors, while instructive, are imperfect. For instance, we can see a quarter drop into the hole, but we’d never actually see a shuttle fall into the event horizon. On the other hand, the event horizon is a hole in the same sense that a manhole is a hole. Comparing it to a manhole is another cognitive metaphor; calling it a hole isn’t, because it is one.

nikofeyn 9y ago
does it make sense to you that a "hole" has mass, electric charge, and angular momentum and is completely characterized by these properties?