If that is a blackhole it wouldnt grow from fist sized to car size by just eating a manor. It wouldnt visually grow at all from eating that tiny little bit of mass.

If our star went blackhole (it wont) it would be the size of earth.

 

I liked the updated one a LOT more.

Can we see Tessa/Harry? Please?

I didn't like Verrine, but Tessa is fucking awesome.

 

That's about right.

However, a real black hole that size would have already absorbed the earth, most likely the moon, and be well on its way to absorbing Mars and Venus.

 

I must agree that Tessa felt overpowered but I don't care that much for fights so it's not a problem for me. And it still is somewhat "realistic". Nicodemus, under influence of Azzeh and Voldemort, barely lost against three opponents at once. Vesper, only half of a year before events of this chapter, in supposedly weakened body, almost managed to kill Harry. And now Harry, after disposing of around twenty Denarians, doesn't receive any important beating. And it seems that his trump card, knowledge of Words, will earn him win in this one. Or would've if it behaved as it was supposed to.

The last information we have about it is that it consumed a quarter of the manor. And that it's bigger than a car. Since we have no way of knowing how big the manor was I don't think estimation is possible. We can estimate it's mass in the beginning though.

So, sphere with diamter around 8cm at the beginning. If it was really a black hole, it's mass would be no smaller than 2.7 * 10^25 kg. No smaller means it can be more. For comparison, mass of Earth equals 6 * 10^24 kg (~4.5 x less).

 

And Harry says he's bad at Transfiguration! He just conjured more mass than the Earth has <_<

 

From its description, it wasn't an actual black hole, but rather some magical effect that has only a loose similarity to it. Well, I suppose it could be bastardized into an actual black hole if the magic is postulated to have some very complicated effects of enormous negative pressure and varying gravitational coupling, but in the end it's just not worth it. The end result it still only recognizable as a black hole only in the metaphorical sense.

There is an ambiguity at to what 'size' means, but that's not quite right by any definition. Let's take the simple case of an uncharged, nonrotating black hole. A black hole 100 times the mass of the Sun would have a Schwarzchild radius of hundreds of miles. In no case is it comparable to a pin.
(a) the singularity itself has no meaningful size, so let's forget about that for the moment;
(b) referring to the region internal to the event horizon, any such black hole has an infinite spatial volume [*], no matter its mass;
(c) it does, however, have a finite surface area of that region (note that the Schwarzschild radius is a derived quantity defined in terms of surface area);
(d) another measure of 'size' is simply its mass.

[*] Or it would without the effects of Hawking radiation, but suffice to say that any black hole that lasts for more than microscopic amounts of time has an enormous internal volume.

Not so. It would only be about three kilometers in radius. Speaking of which, an Earth-sized black hole would be under a centimeter, so a car-sized one represents all the mass of the Earth about a thousand times over.

 

This may be rather simplistic physics on my part, but does that mean that a black hole thus has a very low density? Given that it has a finite mass and an infinite (or so large as to make no difference) volume?

The idea of black holes being low in density is both very counter-intuitive and pretty cool.

 

I'll let it out and tell you that the 'black hole' really isn't a black hole. It's just extreme gravitational pressure sucking everything in. It wasn't meant to be that big, Harry didn't even think it was possible, but if you look closely you'll notice that a little bit of the silvery light of the Sword got sucked in.

Soulfire anybody?

I thought it'd be cool to introduce something from the later books, though it won't really make a difference in the long run. Whether the spell went like that by accident or by divine design is something to think about.

 

Was Verrine's coin consumed by the "gravity spell"? I know you mentioned it was safe early on, but if that spell grows any stronger... It'd be interesting to see what Harry does with either Verrine's or Tessa's coin (give it to Amanda? Hah!).

Tessa IS overpowered since she's doing as well as Voldemort or Vesper against Harry. But I don't mind. Harry's out of challenging enemies to fight it seems.

(I think you're going to get a ton of flak if you post this chapter on ffnet shezza -- people are going to tell you your black hole spell is all wrong, whether you say it's a black hole or not)

 

It would. If you set Schwarzschild's Radius to i.e. event horizon of observable universe, you'd receive minimal density (note 'minimal') so low it could be called vacuum.

 

Absolutely, although it's interesting that large black holes would have a low density even if we pretend that their internal volume is Euclidean--for an uncharged spherical black hole, the Schwarzschild radius is propotional to the mass, so the density would vary as inverse-square of the mass. I think that's what KrzaQ is referring to when he says to set the Schwarzschild radius to something, but using the formula V = (4/3)πR³ for volume of a spherical region is not correct simply because black holes are not Euclidean. Or maybe I'm misinterpreting him.

However, the true volume is much larger because the temporal and radial directions switch over at the horizon--the external lifetime of a black hole becomes a length in the interior region, so the inside of even a non-supermassive black hole can be said to be 1E70 light-years long or thereabouts (note that the diameter of the observable universe is only 1E11 ly). Without Hawking radiation (and if the universe is not closed), black holes would be eternal, so their volume would be infinite.

It gets slightly stranger than that. Isolated black holes are vacuum solutions of general relativity, in the literal sense that wherever one looks in spacetime, there is no mass or energy there (or pressure or anything else). The singularity is sometimes described as a point-mass, but it is not a point in spacetime--it's not 'anywhere' or 'anywhen'.
This may be rather simplistic physics on my part, but does that mean that a black hole thus has a very low density? Given that it has a finite mass and an infinite (or so large as to make no difference) volume?

 

Nice work on this latest update. I really liked most of what happened and I have little to add that has not already been said. Honestly though, I'll have to admit that personally, I'm a little sad to see Verrine gone after all this time. I'm looking forward to what effect the Word might have.

 

Of course. When I read the description, I automatically assumed that it's metaphorical because it didn't act like anything like an actual black hole.

You might want to avoid saying it like that, because now it sounds like you're reversing what you said in the previous sentence. If it was stong enough to affect light that much gravitationally, Harry et al. wouldn't survive being on the same planet, much less in the same bulding/neighborhood.

It's a spell that sucks stuff in, apparently including magic. It looks like black hole in the sense that it's black. It works because the author says it does and it doesn't contradict any element in the story. That's really all that needs to be said about it, and saying more is detrimental--if you try to assign it some particular non-fictional mechanism, such as gravitation, you'll only be shooting yourself in the foot.

 

I'm scratching my head as to why any species/race/creature group would have a Word which would "materialise" into a black hole when laced with magic. The Word branch of magic seems a little overpowered.

Wondering where all the stuff sucked into the black hole that passed through the singularity would exit? Parallel 'verses? Wormhole theory...

 

It must be a blackhole.

It is apparently powerful enough to have an event horizon from which light cant escape.

It has enough gravity in its few meter diameter body to pull matter into it from meters away.

By definition it is a blackhole.

 

I'm too lazy to check, but from what I remember, that's not how Word magic works at all.

The point of Word magic is that no species/race/creature group had a Word which creates a black hole. Rather, the essence of the language itself and the meanings behind the words have power. The older the language is, the longer it has been bouncing around the multiverse and gathers more power to influence. A few chapters ago, Harry slowed down time in a small area with a Word that roughly translated to "what time is it?" Back when the language was actually being used, it was just an ordinary question, but now after eons have gone by, the meaning behind the words have gained power.

EDIT: Okay, I just checked, this is how the Word works:

From Chapter 6

 

It's only a black hole in a similar sense that rubber duckies are ducks. There is some superficial similarity, sure, but seriously equating the two is ludicrous. It can't be muck more than a metaphorical or poetic description of something that compactifies the matter it sucks in.

It absorbs light, therefore it has an event horizon? Seriously?

Even absorbing the entirety of Earth's atmosphere would increase the event horizon of a black hole by a few nanometers. If the effect was gravitational, then
(a) the specific static force of a 1m radius black hole even 50m away is about 1E13 m/s², or equivalent to the surface gravity of a neutron star;
(b) friction from accretion should have heated the infalling matter to an enormous temperature.
Neither effect was observed. A bit ironically, the mere fact that a black surface was visible is evidence that it is not a black hole. Small black holes have worse tidal forces that violently rip apart matter (tidal forces are actually inversely proportional to black hole radius), and that tends to produce immense quantities of radiation.

-- It doesn't suck like a black hole would.
-- It doesn't grow like a black hole would.
-- It doesn't accreting matter like a black hole would, although there are some similarities.
What kind of definition are you using and from where did you pull it?

 

Diverting a bit from the physics discussion...

I think this is a little too convenient, the sword always seems to be there when he needs it and suddenly it isn't. He's disarmed with one spell from Tessa, when he's blocked far stronger stuff from Voldemort (Fiendfyre). Then it basically causes a life threantening situation for Harry?

I'm starting to think that now Harry has destroyed the Order, the Sword doesn't need him anymore. Or it wants to complete the destruction of the Order with Harry's death.

 

It has a gravity so dence light can not escape it. That is the text book definition of a blackhole.

 

Umm...Of course it's convenient, that's the point, it's the Sword of the Cross. Knights who wield the sword are subject to strange coincidences that ensure they are at the right place at the right time. Not only that, there's the whole 'Luck of God' thing which shows there is at least some manipulation by God regarding the events which happen to Knights.

So it's not just convenient, but planned.