2135: M87 Black Hole Size Comparison

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2135: M87 Black Hole Size Comparison

Postby mathmannix » Wed Apr 10, 2019 6:57 pm UTC

Image
Title text: I think Voyager 1 would be just past the event horizon, but slightly less than halfway to the bright ring.

Yeah, Voyager, good luck getting past that event horizon!
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Re: 2135: M87 Black Hole Size Comparison

Postby cellocgw » Wed Apr 10, 2019 7:05 pm UTC

Singularities are really big. You may think it's a long walk.... etc.
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Re: 2135: M87 Black Hole Size Comparison

Postby crystalmeph » Wed Apr 10, 2019 7:22 pm UTC

What's the possibility of using the same VLBI technique to image exoplanets or nearby stars? VLBI basically constructs a virtual telescope with a functional diameter as wide as the two furthest components, so could we do something similar with non-radio parts of the EM spectrum? Could this be used for viewing exoplanets, etc.?

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Re: 2135: M87 Black Hole Size Comparison

Postby SuperCow » Wed Apr 10, 2019 7:26 pm UTC

I assume the orbit of pluto and the location of Voyager 1 are to scale, but the size of the sun and the size of Voyager 1 are not.

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Re: 2135: M87 Black Hole Size Comparison

Postby Moose Anus » Wed Apr 10, 2019 7:33 pm UTC

cellocgw wrote:Singularities are really big.
I mean yeah, it's big, like our solar system is big. But this is a galactic core. It seems really small for something like that. I guess it just shows how incredibly compressed everything is.
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Re: 2135: M87 Black Hole Size Comparison

Postby NotAllThere » Wed Apr 10, 2019 7:46 pm UTC

“Space is big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space.”


Nuff said.
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Re: 2135: M87 Black Hole Size Comparison

Postby rhomboidal » Wed Apr 10, 2019 7:57 pm UTC

Now I'm imagining Voyager 1 and the good robots from Disney's The Black Hole movie battling the bad robot Maximilian in a hellish spacescape. Astronomy is wondrous.

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Re: 2135: M87 Black Hole Size Comparison

Postby Howzers » Wed Apr 10, 2019 7:58 pm UTC

I understand that we're supposed to feel awed by these absurd sizes of things in space but I find the comparisons just stop being meaningful after a while. One unimaginably huge thing is bigger than another unimaginably huge thing. Super?

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Re: 2135: M87 Black Hole Size Comparison

Postby Soupspoon » Wed Apr 10, 2019 8:01 pm UTC

crystalmeph wrote:What's the possibility of using the same VLBI technique to image exoplanets or nearby stars? VLBI basically constructs a virtual telescope with a functional diameter as wide as the two furthest components, so could we do something similar with non-radio parts of the EM spectrum? Could this be used for viewing exoplanets, etc.?

As I understand it, large binocular visual telescopes have been tried with visible interferometry/aperture-synthesis in mind, but at visible wavelengths it's difficult to combine both signals without mechanical 'noise' creeping in along each leg.

(Perhaps the LIGO-mirror dampening methods could be employed, but you might need to mount the firmament-tracking 'scopes in such a device, not just the inward-sending optics at the back end of the individual assemblies. And they already have been adding in adaptive optics and that might steady the image but may not synchronise the steadier images.)

Also, for planet-sized virtual apertures, light has terrahertz frequencies compared to kilo/megahertz for radio, so the Analog/Digital conversion (or equivalent process of storable signal to the one in the radio-telescope long-baseline, even if it was a useful thing to do) would be hugely bandwidth-hungry in the processing.

But I freely admit I'm no expert in optics beyond the basics. I just think it isn't the same problem with the same solution.

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Re: 2135: M87 Black Hole Size Comparison

Postby speising » Wed Apr 10, 2019 8:08 pm UTC

Soupspoon wrote:terrahertz


only on earth.

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Re: 2135: M87 Black Hole Size Comparison

Postby Soupspoon » Wed Apr 10, 2019 8:24 pm UTC

speising wrote:
Soupspoon wrote:terrahertz

only on earth.

*pbbbt*

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Re: 2135: M87 Black Hole Size Comparison

Postby speising » Wed Apr 10, 2019 8:42 pm UTC

if i'm understanding veritasium correctly, the black center is actually 2.6 times the size of the event horizon. that means that Voyager 1 is already way past it. it seems strange that Randall would have such a naive interpretation of the image.

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Re: 2135: M87 Black Hole Size Comparison

Postby Link » Wed Apr 10, 2019 8:44 pm UTC

OH LAWD HE COMIN'.

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Re: 2135: M87 Black Hole Size Comparison

Postby Heimhenge » Wed Apr 10, 2019 8:48 pm UTC

crystalmeph wrote:What's the possibility of using the same VLBI technique to image exoplanets or nearby stars? VLBI basically constructs a virtual telescope with a functional diameter as wide as the two furthest components, so could we do something similar with non-radio parts of the EM spectrum? Could this be used for viewing exoplanets, etc.?


As Soupspoon said, it would be a "similar" process but a WHOLE lot more data intensive. As I understand aperture synthesis, the contributing collectors must have the inter-collector distances measurable to within a half-wavelength to get useful data correlations. With radio waves you have a lot larger margin for error. I'm guessing that with the EHT this was done by timing the individual data streams via atomic clock, assuming the incoming waves are essentially planar, then correcting for known receiver positions on Earth. With optical wavelengths the margin for error becomes much smaller, obviously. But one would think that once all that data is assembled in one place, some kinda AI could twerk the data streams until sufficient resolution emerges for imaging exoplanets.

The radio data was measured in PETAbytes. There was so much data to correlate that, rather then delivering it over the internet, it was faster to just ship the physical hard drives to the correlation facility.

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Re: 2135: M87 Black Hole Size Comparison

Postby Ariphaos » Wed Apr 10, 2019 9:02 pm UTC

speising wrote:if i'm understanding veritasium correctly, the black center is actually 2.6 times the size of the event horizon.


This is correct, when viewing from infinity, the size of a non-rotating black hole's shadow is 3*sqrt(3) / 2 times the size of its event horizon. This apparent size doesn't change much with the black hole's spin (though it does change shape and 'move off center'), but the black hole's event horizon does.

that means that Voyager 1 is already way past it. it seems strange that Randall would have such a naive interpretation of the image.


No, the black hole has an event horizon radius of ~19 billion kilometers, assuming it isn't rotating, which is still beyond Voyager 1's current position.

The shadow we see, as measured along the diagonal in this image, is roughly 50 billion kilometers in radius.

And yes, I signed up just to gripe about XKCD being inaccurate.

Edit: Billion not million, yak.
Last edited by Ariphaos on Wed Apr 10, 2019 11:04 pm UTC, edited 1 time in total.

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Re: 2135: M87 Black Hole Size Comparison

Postby Crawdad » Wed Apr 10, 2019 9:35 pm UTC

speising wrote:if i'm understanding veritasium correctly, the black center is actually 2.6 times the size of the event horizon. that means that Voyager 1 is already way past it. it seems strange that Randall would have such a naive interpretation of the image.


Yes! To be precise, the "last photon orbit," or size of the region from which light cannot come to us from beyond the black hole, is (3/2)sqrt(3) times the event horizon.

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Re: 2135: M87 Black Hole Size Comparison

Postby Mikeski » Wed Apr 10, 2019 11:19 pm UTC

Heimhenge wrote:The radio data was measured in PETAbytes. There was so much data to correlate that, rather then delivering it over the internet, it was faster to just ship the physical hard drives to the correlation facility.

So the Internet hasn't caught up to FedEx yet.

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Re: 2135: M87 Black Hole Size Comparison

Postby 24b4Jeff » Thu Apr 11, 2019 12:16 am UTC

crystalmeph wrote:What's the possibility of using the same VLBI technique to image exoplanets or nearby stars? VLBI basically constructs a virtual telescope with a functional diameter as wide as the two furthest components, so could we do something similar with non-radio parts of the EM spectrum? Could this be used for viewing exoplanets, etc.?


Here is why: to do proper interferometry, it is necessary to add all the signals with phase errors equivalent to a small fraction of a single cycle at the frequency of interest. So: for VLBI at the wavelength of neutral Hydrogen (21 cm, corresponding to a frequency of 1.42 GHz), timing has to be accurate to some parts of a nanosecond - someting that can be done using atomic clocks. To do the same thing at the wavelength of peak visual acuity (about 500 nm, corresponding to a frequency of 6.0E14 Hz), the timing has to be accurate to about 1E-14 sec, that is to say, 1/100 000 nanosecond.
That is several orders of magnitude beyond current technological capability.

There are several other impediments including bandwidth and lack of signal coherence, which I will not bore you further with. But I must comment that analogies with LIGO are completely inappropriate, first because LIGO uses extremely narrowband, correspondingly coherent lasers, and second because there is a physical optical path connecting the mirrors.

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Re: 2135: M87 Black Hole Size Comparison

Postby Soupspoon » Thu Apr 11, 2019 6:44 am UTC

As the sole mentioner of LIGO, that I saw, I meant it only in improving the binocular telescope merging mechanism, to overcome the mechanical variation of separation that must at the very least happen even through the vibrations of each scope as it tracks around the ecliptic during the observation. Possibly also thermal noise.

Unlike LIGO, the beam is not sent multiple times back and forth along deliberately long light-paths (assuming there's no vaguely equivalent compensator to a compensating pendulum relying upon the rebounding light) so LIGO-levels of mirror isolation would produce less beam-path displacement intrinsically within the combining optics to bring the two light-sources together than that deliberately sought to be revealed in a LIGO-arm out of the very fabric of the universe oscillating.

(But first you need to cope with the variations in the throwing of the focal plane out from each rotating monocular input into the combining optics, and in such a manner as to keep the final image-overlaying exactly as coherent or incoherent as needed to refine the final image, and impartially across the visual frequencies too.)


You'd definitely not have any easy method of a world-spanning optical collator across the width of the Earth. Imagine 'piping' the raw light from two polar scopes to overlapping foci on the equator. I daresay there could be an attempt to do it between solar-orbiting spacecraft. Easier to properly station-keep, at Earth-diameter distances, than at two similarly separated points within some Earth orbit with the perturbations of the Moon up high if not the various irregularities of lower Earth orbit. But not easy, still, for other reasons mentioned and otherwise.


It's certainly a problem and a half, and I don't see a solution. But then LIGO, Hubble and various other developments were inconceivable to far greater experts than me (i.e. actual ones, sans armchair!) not too long ago. Maybe continuing lessons from the LBT can shape that future direction.

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Re: 2135: M87 Black Hole Size Comparison

Postby Eebster the Great » Thu Apr 11, 2019 9:15 am UTC

In terms of what we can accomplish in the future that seems implausible to me now, I have to admit that when I was younger, I was convinced that the diffraction limit was somehow unbeatable. Obviously that is false by many orders of magnitude, as both this image and LIGO demonstrate (along with many other superresolution methods). So it gives renewed hope that with enough capital and time and expertise, humans could get astonishingly high quality images of distant objects, like directly imaging planets in other galaxies (may have already happened as early as 96, but is unreproducible).

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Re: 2135: M87 Black Hole Size Comparison

Postby pkcommando » Thu Apr 11, 2019 10:43 am UTC

rhomboidal wrote:Now I'm imagining Voyager 1 and the good robots from Disney's The Black Hole movie battling the bad robot Maximilian in a hellish spacescape. Astronomy is wondrous.

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Re: 2135: M87 Black Hole Size Comparison

Postby Carteeg_Struve » Thu Apr 11, 2019 11:45 am UTC

cellocgw wrote:Singularities are really big. You may think it's a long walk.... etc.


Actually, they aren't. They can get massively tiny (pun intended).

Now the distance from the singularity out to their event horizon, THAT'S BIG.

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Re: 2135: M87 Black Hole Size Comparison

Postby Eebster the Great » Thu Apr 11, 2019 1:17 pm UTC

Singularities can get big in up to one dimension.

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Re: 2135: M87 Black Hole Size Comparison

Postby cellocgw » Thu Apr 11, 2019 2:08 pm UTC

Eebster the Great wrote:Singularities can get big in up to one dimension.


So they can be an infinite line?
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Re: 2135: M87 Black Hole Size Comparison

Postby PM 2Ring » Thu Apr 11, 2019 2:24 pm UTC

From one of the best Stack Exchange Physics pages on singularities, Is a black hole singularity a single point?:
Ben Crowell wrote:A singularity in GR is like a piece that has been cut out of the manifold. It's not a point or point-set at all. Because of this, formal treatments of singularities have to do a lot of nontrivial things to define stuff that would be trivial to define for a point set. For example, the formal definition of a timelike singularity is complicated, because it has to be written in terms of light-cones of nearby points.


I should also mention that a singularity is never in the past lightcone of any observer, even if you've crossed the event horizon of the black hole and are seconds away from reaching its centre (of course, you're probably spaghettified by then, anyway).

Also, we don't know that black holes really have a classical mathematical singularity. We need a theory of quantum gravity to properly model the core of a black hole, and most physicists expect that quantum effects will somehow fuzz out singularities. But even if that's the case, the core of a black hole will be tiny, too small for normal matter particles. Normal GR ought to be an adequate approximation down to proton size and even smaller. Quantum gravity effects probably don't kick in until we get down to the Planck length regime.

For that matter, although we've found plenty of black hole candidates, we still aren't certain that black holes really exist. Although if they don't, then our best candidates, like Messier 87, must be something even more exotic and weird, and they certainly do severely radical things to spacetime in their vicinity. This image of M87 is great evidence that our theories are on-track, but those exotic alternatives still haven't been ruled out yet.

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Re: 2135: M87 Black Hole Size Comparison

Postby Quizatzhaderac » Thu Apr 11, 2019 2:44 pm UTC

Does anybody know how fast it's spinning?

Looking at the photo, the us-ward part of the disc appears about twice as bright as the widdershins part, so on that alone I'd take it to be a lot. However I don't know what kinds of contrast enhancements may have been made.

Ideally, I'd like the answer in terms of Jc/GM2, since that gives us a nice number between 0 (not spinning at all) and 1 (the maximum relativity allows).
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Re: 2135: M87 Black Hole Size Comparison

Postby Soupspoon » Thu Apr 11, 2019 3:50 pm UTC

The asymmetry might just mostly down to the asymmetry of its current* 'meal'. It would be highly unlikely to see a perfect conjunction of the lump-sum of the debris, if it wasn't already eaten enough to be smeared thinly all round the mouth.

* I feel like I should also 'quote' the word "current", to be precise, but that would be confusing enough.

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Re: 2135: M87 Black Hole Size Comparison

Postby Eebster the Great » Thu Apr 11, 2019 4:37 pm UTC

cellocgw wrote:
Eebster the Great wrote:Singularities can get big in up to one dimension.


So they can be an infinite line?

No, but they can be circles of nonzero radius.

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Re: 2135: M87 Black Hole Size Comparison

Postby solune » Thu Apr 11, 2019 4:42 pm UTC

Soupspoon wrote:As I understand it, large binocular visual telescopes have been tried with visible interferometry/aperture-synthesis in mind, but at visible wavelengths it's difficult to combine both signals without mechanical 'noise' creeping in along each leg.


Interferometry has been done in the visual spectrum before, but that was actual interferometry: you move the photons from both telescopes close to each other before observing them. What we're doing now is numerical interferometry where we convert the photons to a numerical signal and then we compute what interference pattern would have been seen if the photons had been sampled on the same receptor.

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Re: 2135: M87 Black Hole Size Comparison

Postby ijuin » Thu Apr 11, 2019 4:50 pm UTC

PM 2Ring wrote:
Also, we don't know that black holes really have a classical mathematical singularity. We need a theory of quantum gravity to properly model the core of a black hole, and most physicists expect that quantum effects will somehow fuzz out singularities. But even if that's the case, the core of a black hole will be tiny, too small for normal matter particles. Normal GR ought to be an adequate approximation down to proton size and even smaller. Quantum gravity effects probably don't kick in until we get down to the Planck length regime.

For that matter, although we've found plenty of black hole candidates, we still aren't certain that black holes really exist. Although if they don't, then our best candidates, like Messier 87, must be something even more exotic and weird, and they certainly do severely radical things to spacetime in their vicinity. This image of M87 is great evidence that our theories are on-track, but those exotic alternatives still haven't been ruled out yet.


Whatever is happening within the event horizon is pretty much irrelevant to what happens outside of it, since the entire point of the event horizon is that it disconnects causality across the horizon. Thus, any mass that fits within its own Schwarzchild radius is pretty much indistinguishable from any other, only retaining the attributes of mass, linear and angular momentum, and electromagnetic charge/field—the “no hair” theorem.

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Re: 2135: M87 Black Hole Size Comparison

Postby da Doctah » Thu Apr 11, 2019 8:43 pm UTC

Carteeg_Struve wrote:
cellocgw wrote:Singularities are really big. You may think it's a long walk.... etc.


Actually, they aren't. They can get massively tiny (pun intended).

Now the distance from the singularity out to their event horizon, THAT'S BIG.


ObFranchiseShift: and they're bigger on the inside.

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Re: 2135: M87 Black Hole Size Comparison

Postby Jesterr » Thu Apr 11, 2019 9:19 pm UTC

Ariphaos wrote:
speising wrote:if i'm understanding veritasium correctly, the black center is actually 2.6 times the size of the event horizon.


This is correct, when viewing from infinity, the size of a non-rotating black hole's shadow is 3*sqrt(3) / 2 times the size of its event horizon. This apparent size doesn't change much with the black hole's spin (though it does change shape and 'move off center'), but the black hole's event horizon does.

that means that Voyager 1 is already way past it. it seems strange that Randall would have such a naive interpretation of the image.


No, the black hole has an event horizon radius of ~19 billion kilometers, assuming it isn't rotating, which is still beyond Voyager 1's current position.

The shadow we see, as measured along the diagonal in this image, is roughly 50 billion kilometers in radius.

And yes, I signed up just to gripe about XKCD being inaccurate.

Edit: Billion not million, yak.


Funny, I signed up for the same reason. The perspective is off, voyager is way to close to the light. Voyager should be just shy of the 1/2 way mark from the sun to the light ring's edge.

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Re: 2135: M87 Black Hole Size Comparison

Postby Quizatzhaderac » Thu Apr 11, 2019 9:28 pm UTC

Soupspoon wrote:The asymmetry might just mostly down to the asymmetry of its current* 'meal'. It would be highly unlikely to see a perfect conjunction of the lump-sum of the debris, if it wasn't already eaten enough to be smeared thinly all round the mouth.
That answer raises two more questions. 1) Does the diet show that much variance on a 3 billion solar mas black hole? (I'd figure it would be a large number of small meals) 2) Is the disk below optical thickness? If not, then we can't really assume brightness and density correlate.
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Re: 2135: M87 Black Hole Size Comparison

Postby Soupspoon » Fri Apr 12, 2019 1:46 am UTC

Quizatzhaderac wrote:That answer raisestwo more questions.
Not by my understanding of what I thought I said, though they are indeed questions.

Incidentally, I'm sure Dr Bowman Bouman has consciously been avoiding telling us that it's full of stars…

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Re: 2135: M87 Black Hole Size Comparison

Postby squonk » Fri Apr 12, 2019 10:09 am UTC

Wow. If that is to scale, then Pluto is HUGE!

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Re: 2135: M87 Black Hole Size Comparison

Postby Xenomortis » Fri Apr 12, 2019 11:36 am UTC

https://en.wikipedia.org/wiki/Messier_87#Supermassive_black_hole wrote:The telescope's astronomers proposed to name the black hole Pōwehi, meaning "embellished dark source of unending creation" in the Hawaiian language.

What terrible calamities befell you, what horrible darkness fills your history, for that to be conveyed in three syllables?
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Re: 2135: M87 Black Hole Size Comparison

Postby speising » Fri Apr 12, 2019 12:25 pm UTC

i'm not sure "source" or "creation" would be something i'd associate with BH's.

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Re: 2135: M87 Black Hole Size Comparison

Postby PM 2Ring » Fri Apr 12, 2019 1:12 pm UTC

Soupspoon wrote:Incidentally, I'm sure Dr Bowman Bouman has consciously been avoiding telling us that it's full of stars…

I bet if there were a video on YouTube of Dr Katie Bouman looking at the M87* image on a computer monitor and saying "My God, it's full of stars!", it would go viral. :D

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Re: 2135: M87 Black Hole Size Comparison

Postby Quizatzhaderac » Fri Apr 12, 2019 5:35 pm UTC

Xenomortis wrote:
https://en.wikipedia.org/wiki/Messier_87#Supermassive_black_hole wrote:The telescope's astronomers proposed to name the black hole Pōwehi, meaning "embellished dark source of unending creation" in the Hawaiian language.

What terrible calamities befell you, what horrible darkness fills your history, for that to be conveyed in three syllables?
English "God" - Creator of the heaven, the world, and man; source of love and justice, maintainer of existence.
Ancient Greek "Khaos" - The first thing to exist, the gaping void holding heaven and Earth unseperated.
Chinese "Tao" - The non thing which creates and orders all thing, of which we can only truly understand things through understand the path that it creates.

After a brief and superficial overview of Hawaiian mythology, it appears "darkness" doesn't connotate "hidden, dangerous, evil", but "spiritual", and (wild guess) "It's finally not so %&(*ing hot outside!"
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Re: 2135: M87 Black Hole Size Comparison

Postby Xenomortis » Fri Apr 12, 2019 5:56 pm UTC

Quizatzhaderac wrote:English "God" - Creator of the heaven, the world, and man; source of love and justice, maintainer of existence.

Queen of the Andals, Breaker of Chains, and Mother of Dragons...

That isn't what the word "God" means in the English language, that is a Judeo-Christian entity.

(But yes, I get that the word question here is also of religious origin.)
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