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Comment by sandworm101 | Hacker News Reader

I do like the evolution of black hole illustrations. They change every few years, mostly based on depictions by hollywood, the latest being Interstellar. The current trend, the symetrical ufo-shape, is scientifically more accurate than the previous whirlpool but isnt perfect. It doesnt show the red/blue shifting. If you were actually looking at one with human eyes, you would probably see a rainbow effect. One side would be blue/white other red/black, with variations inbetween. But every attempt at such rendering just doesnt look as intimidating or magnificent.

It is like dinosaurs on TV. Over the years they have gone from naked lizards, to having feathers, to being almost furry, and now back to naked again as hollywood balances science with audience expectations.

This sort of thing. https://twitter.com/redshift3d/status/1156595374183854080?s=...

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The idea that Interstellar "taught" us what black holes look like is way overblown and oversold. John-Pierre Luminet and others were drawing black holes back in the 1970s.

https://blogs.futura-sciences.com/e-luminet/2018/03/07/45-ye...

https://blogs.futura-sciences.com/e-luminet/2019/05/23/40-ye...

https://blogs.futura-sciences.com/e-luminet/2019/06/12/40-ye...

> The current trend, the symetrical ufo-shape, is scientifically more accurate than the previous whirlpool but isnt perfect. It doesnt show the red/blue shifting.

A bit of a technicality, but the frequency shifting would only occur for rotating black holes but not non-rotating black holes. However, as far as I understand, non-rotating black holes are assumed to not exist in reality.

> idea that Interstellar "taught" us what black holes look like is way overblown

Teachers don’t invent mathematics when they teach addition, they distribute known knowledge. Interstellar absolutely taught many people a more-accurate image of a black hole. They did not discover Doppler beaming or the accretion disk’s wrap around, sure, but I haven’t seen that claim made explicitly as much as heavily implied.

Taught was maybe a bad word choice. If you watch the promotional materials for Interstellar, you get a strong implication that they were the first to show what a black hole looks like, but that is not the case. People have picked up on that on that vibe and think that the tech behind the movie gave us the first pictures. There certainly was an evolution there, but it wasn't the start of it.

No doubt Interstellar popularized and helped re-energizze discussions about black holes, especially since it came out just before LIGO started making discoveries, which propelled things even further.

If we are getting an image, it is a rotating black hole. The light we see came from somewhere and didn't fall straight into the event horizon. Therefore it imparted some rotational energy as it dipped in and out. Therefore, any black hole emitting anything more than hawking radiation has at least some angular velocity.

> Therefore, any black hole emitting anything more than hawking radiation

What else does a black hole emit besides Hawking radiation?

> Therefore it imparted some rotational energy as it dipped in and out.

You're bringing up an interesting point. So any photon passing by a Schwarzschild black hole should actually set the BH in motion/rotation. Then again, I would expect these effects to cancel each other out, given a somewhat random distribution of incoming photons?

https://www.wolfram.com/customer-stories/academy-award-visua...

This has better background on it.

They did do some test renders for Interstellar with better fidelity. You can see some in this article [1] or in the paper they wrote on their renderer. They were simulating film response rather than human retinal response, but it’s probably close enough.

[1] https://cerncourier.com/a/building-gargantua/

Incredibly beautiful - I wonder how (and how long) it will be that we can get better real images of black holes, the most extraordinary objects we know to exist.

Current best bet is using our sun as gravitational lens, but with current technology it would take 2-3 decades to get satellites far enough (few times further than New Horizons is currently) for that to be possible.

Gravitational lensing is one option, but another is the Terrascope concept whereby the Earth's atmosphere would be used as a refractive lens. In theory, any atmosphere would do. It may even be possible to use Jupiter's outer atmosphere. As refraction is stronger than gravitational lensing, such schemes would not require multi-decade trips out focal points at edges of the solar system.

https://arxiv.org/abs/1908.00490

Can you explain why gravitational lensing is important?

It allows for star-sized telescoped, lenses bigger than stars that can focus objects very far away.

The best bet in our lifetimes will be by luck. There is a chance that gravitational lensing of a distant object might give us a glancing view of a black hole if thing line up just perfectly. But the chances of this happening, and that we actually are looking at the right place/time, are very very small.

It will be very tricky to get better images. Black holes are very small and very far away.

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