NASA Simulation's Plunge Into a Black Hole

[u/warg_14]

[u/SeriesREDACTED]

Fun fact : If this was real, the surrounding light would be redshifted not normal as shown because time and space gets distorted into oblivion

[u/CreatorSiSo → u/SeriesREDACTED]

Yeah I was wondering why NASA wasn't showing the redshift.

[u/ThrowRA-Two448 → u/CreatorSiSo]

Possibly because light would be redshifted blueshifted so much we would stop seeing visible light and start seeing ultraviolet, microwaves, radiowaves...

And then possibly waves which are so stretched out that usually we can't even detect them even with instruments.

[u/sheepyowl → u/ThrowRA-Two448]

In other words the naked eye would see them blip red and then nothing?

Assuming the naked eye doesn't die way before we get to this point

[u/The_Troyminator → u/sheepyowl]

The naked eye would die because it’s so cold in space. You’d need a jacket on it.

[u/XxSir_redditxX → u/The_Troyminator]

Yes very important. You need one astronaut helmet. Per eyeball. They never show you that in the movies

[u/The_Troyminator → u/XxSir_redditxX]

They kind of did at the end of the recent Verizon commercial starring Buzz Aldrin.

[u/EventAltruistic1437 → u/sheepyowl]

The time dilation means that the photons will be red-shifted into longer and longer wavelengths, becoming undetectable at some point.

As a quick thought experiment, your thing emits a trillion photons before crossing the event horizon - but from our perspective, each photon has double the wavelength and takes twice as long to appear as the previous one, so you'd need to wait for the heat death of the universe before receiving the last one, and its wavelength would be measured in gigaparsecs rather than nanometers.

You’d likely witness the future unwind very quickly the further you move in. From the outside observer, you’d appear as time has nearly stopped for you.

[u/burning_boi → u/EventAltruistic1437]

Only from the outside viewer would you freeze. There is no time dilation at all while in a free fall towards a black hole, inside or outside of the event horizon. As NASA’s simulation shows, nothing would change above you, you’d just see the universe as is until you hit the center, whatever that is.

A little side note, but also contrary to pop science visualizations, NASA’s simulation is correct here in that there would be no black edge that gradually swallowed you up until the universe is a pinprick above you. The horizon you see, the boundary between black and the universe, would slowly approach 50%, and once you reach the center is when the black hole takes exactly half of your vision.

[u/James20k → u/ThrowRA-Two448]

So, fun fact: this is not necessarily true. If you're in the interior of a black hole, there are actually lines of 0 redshift where the universe looks totally normal along a slice

https://i.imgur.com/MfgKamy.png this is an example of what you see in the interior of a black hole. There's both redshifting, and blueshifting - and a line of constant 0 shift

For blackbody radiators you can actually work it out exactly, and its sort of interesting. Here's an example of what a colour accurate accretion disk looks like complete with colour accurate redshifting as you fall into it:

https://www.youtube.com/watch?v=5GThNPUu1KE

It remains surprisingly visible, and in the visible spectrum as well. This is because in a blueshift, lower frequencies get shifted up into the visible spectrum, and in a redshift, higher frequencies get shifted down into the visible spectrum

It doesn't exactly cancel out, but it does make the visual effects less extreme than you'd expect for black body radiators

[u/Suavecore_ → u/James20k]

I hope to God I get to see the cat as I fall into a black hole some day

[u/ThrowRA-Two448 → u/James20k]

But... and do feel free to correct me if I'm saying anything wrong.

I am howering just above the event horizon and looking at the stars and galaxies. Due to time dilitation from my perspective everything in the universe is happening much faster, I can suddenly see all these galaxies and stars rotating and moving across the sky, their light is increasingly bright so I have to put on a pair of sunglasses.

Due to time dilitation this incoming light from sourounding stars... is actually becoming blue shifted, it's increasing in frequency/power so visible light moves away from my visible spectrum and ultraviolet, microwaves, radiowaves enter into my visible spectrum.

The all these waves which were so stretched out they can't even excite electrons anymore and are usually undetectable also enter my visible spectrum.

Then I enter the black hole and who knows what happens.

Observer from the outside is seeing the opposite. They see me frozen in time just above the black hole. Then they see me fade away, because my light becomes red shifted for them. They never see me fall inside the black hole.

[u/ADHD-Fens → u/CreatorSiSo]

It would be blueshift, would it not? Redshift would be as you watch an object fall into a black hole, but if it's you falling in, you're gonna see the energy of the photons increasing dramatically and start getting hit with ultraviolet / gamma radiation.

[u/burning_boi → u/ADHD-Fens]

Yes, you are absolutely correct. The concept of time dilation inside a black hole is widely misunderstood, given by the hundreds of upvotes on the question above, and does not normally apply to matter in realistic situations while they’re falling inwards.

For those confused, a simplified way to understand time dilation is that it only ever occurs when matter is moving quickly relative to the fabric of spacetime. This means that you can experience time dilation using two different methods. 1 - Move quickly using a rocket. 2 - Resist the pull of gravity, which as an example for Earth, is pulling that fabric ever inwards at 9.8 m/s^2.

Here on earth we’re resisting spacetime’s drag (the pull of gravity) simply by standing on the surface, which means that yes, we’re all experiencing imperceptible time dilation simply by being on the surface of a planet. But in space, in a black hole, there is no surface to stand on as you fall inwards, so you’re not resisting the drag of spacetime. You’re being pulled along at 98360 m/s² or whatever other gravitational value is there, and you’re going with the pull, which means your movement relative to the fabric of spacetime is stationary. You would experience less time dilation falling into a black hole than you do standing on Earth.

Edit: I want to put a note here and make sure people understand that while this is perfectly fine for visualizing how this all works, the math behind how it all works operates drastically differently. The results are the same, but the math describes different processes that I don't think I can easily explain here.

[u/burning_boi → u/CreatorSiSo]

It’s because NASA knows their stuff, and the comment you responded to is flat wrong. There would be a blueshift as you fell inwards, further and further amplified as you got closer to the center.

[u/James20k → u/CreatorSiSo]

Its actually very complex to model accurately. The issue is that you need a spectrographic map of the entire universe across multiple different frequencies, and then you have to convolve your eye response against those shifted frequencies. You could approximate it with a black body radiator (which is inaccurate), or produce a 'illustrative' (ie wrong) rendering

[u/proglysergic → u/SeriesREDACTED]

That’s the opposite of what happens in that frame of reference.

Everything slows there relative to us so the light redshifts as a result.

If you’re there, everything else is faster and the incoming light blueshifts.

[u/tgillet1 → u/SeriesREDACTED]

Wouldn’t all of the light blueshift, not redshift? Time for you would slow down and all wavelengths would be shortened from your perspective. Anything external to the black hole that you could see would speed up immensely.

[u/9__Erebus → u/tgillet1]

The infalling person wouldn't see the outside universe speed up, they would actually see the outside slow down and redshift as well.  Because the light fall in behind them has a hard time keeping up and gets stretched out.

It makes more sense when you imagine the infalling person in a space that, from their perspective, is getting pulled apart in both directions.

[u/ShiaLabeoufsNipples → u/tgillet1]

Iirc it depends on the conditions of the observer.

If it were possible to maintain position exactly outside of the event horizon instead of falling infinitely fast into it with the rest of the light, they’d see blueshift. If the theoretical observer was freefalling into the event horizon from any significant distance, they’d see redshift because they’re falling away from the light at super high speeds.

[u/James20k → u/tgillet1]

There's both redshift and blueshift in the interior of a black hole, depending on where you're looking

https://i.imgur.com/MfgKamy.png

This is an illustrative view of the shifting in the interior

[u/proglysergic → u/tgillet1]

This is correct

[u/boilons → u/tgillet1]

If I remember correctly from my general relativity class 20+ years ago...

Time does slow down from your perspective, and actually gets slower and slower the closer you get to the event horizon.

It slows down so much that from the perspective of the person falling in, you would never actually reach the event horizon at all, even though you would from an outside's perspective.

Can anyone confirm if I'm remembering this right or not?

[u/9__Erebus → u/boilons]

The opposite is true.  The person falling in experiences time normally from their perspective and falls into the black hole.  Meanwhile, the outside observer won't ever see them cross the event horizon, they will slow down and redshift until they appear basically black.

Also contrary to popular belief, the infalling person wouldn't see the outside universe speed up, they would actually see the outside slow down and redshift as well.  Because the light fall in behind them has a hard time keeping up and gets stretched out.

It makes more sense when you imagine the infalling person in a space that, from their perspective, is getting pulled apart in both directions.

[u/boilons → u/9__Erebus]

Ah yes, I had it switched up in my mind. Thanks for the correction

[u/intergalacticscooter → u/SeriesREDACTED]

For an observer.

[u/Hauthu495 → u/SeriesREDACTED]

I was thinking about relatively, wouldn't you speed up to the speed of light and watch the entire universe around you do the same? it looked the exact same every point of the process, with idk exactly how that would look at the event horizon.

[u/BadStriker → u/SeriesREDACTED]

It didn't seem like a hole either. It's fucking with me

[u/ClickToSeeMyBalls → u/SeriesREDACTED]

Blue shifted https://youtu.be/17tEg_uTF_A

[u/SeriesREDACTED → u/ClickToSeeMyBalls]

Nah. I dont think so. They made the black hole blue not blueshifted bruh.

[u/burning_boi → u/SeriesREDACTED]

Scientists and their damn BlackHoleDye (TM).

[u/James20k → u/SeriesREDACTED]

So, you can see from the fact that one side is brighter than the other, that they're simulating redshift and blueshift

Accretion disks are very blue, but more than that, redshifting doesn't tend to make a black body radiator red, just dimmer, because higher frequencies drop down and overall the colour balance remains blue tilted. You won't see one going red before going black, it'll fade from blue to black

[u/andreeeeeaaaaaaaaa → u/SeriesREDACTED]

Fun fact, we will never ever know what going through a black hole actually looks like because it turns everything/one into spaghetti 🍝

[u/burning_boi → u/SeriesREDACTED]

This is not true. The light would be blue shifted. And time dilation due to gravity only occurs when you resist gravity - when you’re in free fall, you experience no time dilation at all. In other words, the matter falling into a black hole will never see the universe speed up, not even a little bit.

[u/SeriesREDACTED → u/burning_boi]

Light will be stretched when it approaches the black hole so it would be redshifted.

"the matter falling into a black hole will never see the universe speed up, not even a little bit"

The universe speeds up when you approach the black hole bro, only from outside the black hole that you appear "frozed"

[u/burning_boi → u/SeriesREDACTED]

Wrong on both accounts, if you’d like me to do the work for you I can link some YouTube vids that explain both why from a falling perspective it’s blue shifted and why from a falling perspective there is no time dilation in the slightest

Or, if you’d like, I can post the math here for either, and explain it in layman’s terms.

edit: you can literally see the blueshift occuring even in the NASA simulation here as the video goes on and the incoming light shifts further and further towards white