Gas cloud around black holes

[Kamik423]

This is the black hole in the movie interstellar

A friend of mine said, that it is one of the most physically accurate depictions of black holes.

BUT:

since matter moves at light speed at the event horizon, shouldn't the matter just outside of it be near luminal speed as well?

So shouldn't the cloud on one side of the black hole be red and blue on the other?

[SargeRho]

The radiation emitted is pretty much across the whole spectrum, so red and blueshift aren't going to do anything: It'll still be bright white.

[Kamik423]

thanks

[VanFlyhight]

You are right, Kip Thorne actually discusses this in The Science of Interstellar. The dust cloud in reality would red shift and blue shift on opposite sides but for the movie they thought it would confuse the audience rather than think it realistic.

[Darnok]

You are right, Kip Thorne actually discusses this in The Science of Interstellar. The dust cloud in reality would red shift and blue shift on opposite sides but for the movie they thought it would confuse the audience rather than think it realistic.

So instead making educative speech in movie they prefered to change things in way that uneducated person would think "it is working like that"!

Isn't that a harmful influence of movies? I thought media was made so we could communicate and educate faster, not to affirm people in the conviction that their ignorance or ideas, not supported by any evidence or studies, are correct.

[Gaarst]

So instead making educative speech in movie they prefered to change things in way that uneducated person would think "it is working like that"!

Isn't that a harmful influence of movies? I thought media was made so we could communicate and educate faster, not to affirm people in the conviction that their ignorance or ideas, not supported by any evidence or studies, are correct.

You must be new to Holywood...

Anyway, I would care about the black hole redshift if there wasn't all the utter BS with the blackhole in the end... and in the whole movie actually: ever heard of tidal forces ?

[Shpaget]

Darnok, considering the fact that movie fails at depicting basic Newtonian stuff correctly, this really is no surprise.

[AngelLestat]

This is the black hole in the movie interstellar

A friend of mine said, that it is one of the most physically accurate depictions of black holes.

BUT:

since matter moves at light speed at the event horizon, shouldn't the matter just outside of it be near luminal speed as well?

So shouldn't the cloud on one side of the black hole be red and blue on the other?

http://cdn.zmescience.com/wp-content/uploads/2015/02/maxresdefault.jpg

You are right but in the wrong way.

The red shift and blue shift you will see is not by the light that orbit close to the black hole (light can orbit in any direction), is because the black hole is rotating. So all the space is coming in the left and going in right.

something like this:

https://briankoberlein.com/wp-content/uploads/blackhole2.jpg

Edited September 14, 2015 by AngelLestat

[Darnok]

You must be new to Holywood...

I am not "new", I just criticize them for doing that. They won't change it if everyone will learn to accept what they are doing?

If you don't criticize them you are helping them to make more money on things that are common lies.

[Kamik423]

something like this:

https://briankoberlein.com/wp-conten...blackhole2.jpg

thanks for the link, that exactly what i meant

[Jovus]

Actually, given the size of the black hole in question, the red shift is most likely negligible. But even if it isn't, there's enough radiation in the upper and lower bands to compensate. No, the real problem is everyone on board would be dead of gamma ray exposure before the image even registered in their brains.

[GeneralVeers]

since matter moves at light speed at the event horizon, shouldn't the matter just outside of it be near luminal speed as well?

Absolutely, yes--from its own frame of reference.

From ours, much higher up in the gravity well, the matter would appear to be moving much more slowly--if we could see it at all (keep reading).

So shouldn't the cloud on one side of the black hole be red and blue on the other?

Well, not those colors specifically. But blue-shifted on the approaching side and red-shifted on the receding side, yes. However, this blue-shift and red-shift come from the velocity of the orbiting matter. The gravitational pull of the black hole itself exerts an additional red-shift. Just above the event horizon, this red-shift approaches infinity and any object that's there becomes impossible to see.

So instead making educative speech in movie they prefered to change things in way that uneducated person would think "it is working like that"!

Isn't that a harmful influence of movies? I thought media was made so we could communicate and educate faster, not to affirm people in the conviction that their ignorance or ideas, not supported by any evidence or studies, are correct.

Heheh. Keep this in mind: most people who come to this web site probably play Kerbal Space Program--a game that requires an actual brain. So pretty much everybody here has a brain and knows how to use it.

The common people, by comparison, are idiots.

You must be new to Holywood...

Anyway, I would care about the black hole redshift if there wasn't all the utter BS with the blackhole in the end... and in the whole movie actually: ever heard of tidal forces ?

Tidal forces might not actually be a problem; it's known that with a really large black hole, tidal forces are much weaker at the event horizon. Weak enough that a person could pass through safely, if the black hole is massive enough. Though I have no idea how much mass that would be.

The thing that bugged me about Mister Protagonist "dipping my ship below" the event horizon is, apparently, it's not possible to do that. As you approach the event horizon, your frame of reference changes and the event horizon appears to remain below you--even after you cross it! Keep in mind this is just me reading from other sources, but from what I've read, it's impossible to tell when you've crossed the event horizon because nothing unusual happens. There's no flash of light, nothing goes boom. You just continue falling. And as you look up, the universe outside appears the same.

[Kerbart]

(...)

Heheh. Keep this in mind: most people who come to this web site probably play Kerbal Space Program--a game that requires an actual brain. So pretty much everybody here has a brain and knows how to use it.

The common people, by comparison, are [xxxxx].

One might consider this judgemental, yes even elitist. The "common people" ("commoners?" "plebs?" "gepeupel?") in general are not the word you are using there. However most people will not care about these kind of things because quite frankly, the impact on their daily life is about zero. Does that make them [xxxxx] though? One can make the case that anyone unable to make a fire from a few pieces of wood, or without the knowledge how to create a shelter out of leaves and sticks to keep yourself warm and dry during a storm, or without the skill to spearfish, can be listed under the same word you mentioned. And in case those are things you don't need in the city is a reply to that--neither is the knowledge of what you're supposed to see when encountering a black hole. In fact, the chances of getting stuck on an uninhabited island are still infinitesimally larger than that.

[Kamik423]

it's impossible to tell when you've crossed the event horizon because nothing unusual happens. There's no flash of light

Shouldn't there be, or at least you would be able to see a lot of stuff at least on a plane (from your perspective) because all the light emitted by matter crossing the event horizon is still there, orbiting until something crosses its path to be hit. So it would orbit for a very long time. When you come by you should be able to see all that light, shouldn't you?

the brightness would depend on the kind of matter the black hole 'eats', but if it was a star and emitted more light than it absorbs there should be a glow trapped forever inside the EH. If it was just dust and gas, it would be dark.

POINT IS:

you should still be able to see all that matter at once, and tell this way when you cross the EH.

BUT:

This is from my limited understanding of black holes

[GeneralVeers]

One might consider this judgemental, yes even elitist.

Yup. It's both. Judgemental AND elitist.

And also true.

One can make the case that anyone unable to make a fire from a few pieces of wood, or without the knowledge how to create a shelter out of leaves and sticks to keep yourself warm and dry during a storm, or without the skill to spearfish, can be listed under the same word you mentioned. And in case those are things you don't need in the city is a reply to that

I was thinking more along the lines of: if you get in a plane crash or something, and you're OUTSIDE a city.....suddenly the ability to build a shelter and a fire becomes very, very important indeed. Because without those you could end up dead. And this does happen from time to time.

BUT:

This is from my limited understanding of black holes

Mine too.

Shouldn't there be, or at least you would be able to see a lot of stuff at least on a plane (from your perspective) because all the light emitted by matter crossing the event horizon is still there, orbiting until something crosses its path to be hit. So it would orbit for a very long time.

Absolutely--when seen from far outside the event horizon.

But as you close in on the event horizon, that changes. Your reference frame changes; you're moving deeper into the gravity well and the passage of time is changing for you. So, once you get very close to the event horizon, all the light and matter that appeared to be eternally trapped there, no longer is. Anything that was on a straight-down trajectory, for example, will once again appear to be far below you.

the brightness would depend on the kind of matter the black hole 'eats', but if it was a star and emitted more light than it absorbs there should be a glow trapped forever inside the EH. If it was just dust and gas, it would be dark.

Once the black hole grabs the above matter, and starts pulling it in and crushing it in on itself, the compression causes extreme heating. So, whatever kind of matter it used to be, light or dark, no longer matters. That's the source of the radiation black holes emit. You're familiar with the fact that objects glow in visible light when hot enough? That rule holds past the visible spectrum: crush something further, make it hot enough, and it starts glowing in ultraviolet, and eventually X-rays.

[Kamik423]

what I meant:

the glowing (in whatever spectrum) matter passes through the event horizon

--> the photons emitted will stay in orbit AT THE EVENT HORIZON until they hit something

--> if it is glowing (what WedgeAntilles said above) it will emit more light than absorb

--> so in the end the brightness RIGHT AT THE EVENT HORIZON should increase over time

--> when passing through that you should see all that light

right?

[GeneralVeers]

The photon sphere is a dynamically unstable orbit. A tiny bit further away, and the light escapes. A tiny bit further in, and it's adios. The photons only "stay in orbit at the event horizon until they hit something" from our frame of reference, far away from the event horizon. From its own frame of reference (or as we would see if we moved in close) the light doesn't stay in that orbit for long.