Gatephysics - 2 things that bother me

[Quadhelix]

I remember hearing somewhere (SG1 or SGA) that the gate doesn't actually start dematerializing an object until it has completely passed through the event horizon (which is why Kowalzki's head wasn't cut open in 'enemy within'). Non living objects might be an exception which is why a staff weapon can be seen having it's end cut off in 'Point of View'.

You are misinterpreting something that you heard in "38 Minutes" (SGA 1x03), namely that objects are not transmitted until they have fully passed the event horizon; i.e., until they have been fully dematerialized.

Indeed, in that very episode

While on the subject of Gatephysics, can anyone explain to me how in SG1 they receive GDO codes BEFORE the gates connect?

Production error.


If you want an "in-universe" explanation, then you can imagine that the micro-wormhole used to transmit material forms before the event horizon, and that the IDC can be transmitted through the micro-wormhole. This would, incidentally, explain how the receiving Stargate can know that there is an incoming wormhole before the event horizon forms.

[K^2]

The idea that gravitons "carry" gravity only makes sense within realm of quantum field theory. I don't want to get too deep into concepts of quantum gravity, because there isn't even a complete theory to describe it in a self-consistent matter, let alone there being anyone to understand that theory. More importantly, quantum gravity shouldn't really matter to discussion of the event horizon. Wormhole itself, probably, but not the event horizon. So, lets forget quantum and focus on gravity itself.

If you treat gravity from perspective of General Relativity, there is no such thing as a graviton. Gravity is just an outcome of curved space-time. Event horizon is location where it curves "too much". Anything that contributes to curvature of space-time can shift where the Event horizon is located. Gravitational waves could, potentially, send ripples through it (not event horizon of a black hole, though), but to get gravitational waves, a very large mass must undergo very high acceleration. Note that planet falling into the black hole is not actually undergoing acceleration relative to any inertial frames.

It's a little difficult to pinpoint exactly what sort of event horizon we are dealing with in case of the Star Gate. If it was an event horizon of the wormhole itself, there wouldn't be a buffer. So something interesting must be going on.

[Coremae]

K^2, you need to learn the habit of explaining what your terms mean. For example, the term "metric" probably won't mean much to anyone who hasn't taken a course on General Relativity or differential geometry: just about everything else assumes a metric of diag[1,1,1]. Yes, I know (now) that Special Relativity is an exception, using either diag[1,-1,-1,-1] or diag[-1,1,1,1], but that either wasn't really explained when I first learned it, or little enough emphasis was placed on it that I missed it.



Incorrect: to the best of our ability to determine, gravitons have no size at all. The same is apparently true of all other elementary particles, such as electrons, photons, and quarks.



Well they can't, so neither can you: Bosons get their name from the fact that they obey the Bose-Einstein statistical model, just as Fermions obey the Fermi-Dirac model.

"Force-carrying" particles are called Gauge Bosons because they are bosons and are related to the "gauge" of the force that they carry. I'm pretty sure that K^2 could explain gauges better than I could, but from what I know, the gauge of a force is an alteration to the Potential of the force that is independent of the sources that produce that Potential and that does not affect the field of that force.



Shouldn't the "globules of doing" be the ones that do something?



The general consensus is that the actual wormhole is microscopic: the amount of energy required to make a wormhole even a millimeter across would be absolutely astronomical.



A static black hole would not cause gravitational waves, just as a boat sitting still on a pond would not produce a wake. Black holes do, of course, produce very strong gravitational fields, but not gravitational waves.



Gravitons are a bosons, meaning that they obey the Bose-Einstein statistics, meaning that they can "stack" one on top of the other. Space would not be an issue.

Okay, that's just awesome, now, I have to take a while to get my head in to the game, and i'll have a witty come back, but now, i need to focus, or try to focus, and once that's done---yeah, good times.

Thanks again though, and I do really mean it, you're making me smarter, and making an idiot smarter is the greatest form of charity.

The idea that gravitons "carry" gravity only makes sense within realm of quantum field theory. I don't want to get too deep into concepts of quantum gravity, because there isn't even a complete theory to describe it in a self-consistent matter, let alone there being anyone to understand that theory. More importantly, quantum gravity shouldn't really matter to discussion of the event horizon. Wormhole itself, probably, but not the event horizon. So, lets forget quantum and focus on gravity itself.

If you treat gravity from perspective of General Relativity, there is no such thing as a graviton. Gravity is just an outcome of curved space-time. Event horizon is location where it curves "too much". Anything that contributes to curvature of space-time can shift where the Event horizon is located. Gravitational waves could, potentially, send ripples through it (not event horizon of a black hole, though), but to get gravitational waves, a very large mass must undergo very high acceleration. Note that planet falling into the black hole is not actually undergoing acceleration relative to any inertial frames.

It's a little difficult to pinpoint exactly what sort of event horizon we are dealing with in case of the Star Gate. If it was an event horizon of the wormhole itself, there wouldn't be a buffer. So something interesting must be going on.

wow, just wow. Even though I don't mean to take things off topic, but I'm just thankful that you friends know what i've been trying to understand for far too long, and for some reason, i'm not getting it, maybe it's adhd, maybe it's the fall on the head i received twenty plus years ago from twelve feet, who can say--- maybe i'm just an idiot. Point is though, i'm appreciative, but now i have to watch a few videos, listen to some music and try and formulate a response worthy of these post.

edit: I'm understanding it a bit more now, images are jumbled about in my mind and grasping them and placing them in order is a tedious but incredibly zen like activity.

[Chevron999]

There can be two explanations:
1. The puddle was distorted on the other side so the effect was replicated here; so that anyone going through the wormhole would not get ripped apart by the different shape of the puddle on rematerialization i.e. another safety feature. Or maybe the shape just got duplicated regardless of that .

Possibly...
The gate makes a mirror of the event horizon on the other side, so that anything going thorough the wormhole does not get deformed, when exiting through a miss shaped event horizon, on the other side. The downside would be that they would be ripped apart by the gravity on the other side, so its kind of pointlesss, but the Ancients ALWAYS thought of everything

[K^2]

Event horizon on the other side shouldn't buckle either. Black hole's mass does not actually increase during a collapse. Of course, that basically ruins the premise of the entire episode...

[Chevron999]

Event horizon on the other side shouldn't buckle either. Black hole's mass does not actually increase during a collapse. Of course, that basically ruins the premise of the entire episode...

Indeed... But we don't know the effects a black hole would have on an artifically created wormhole...
Although I'm not a physicist, yet, I thought that a black holes mass would increase, as it absorbed more matter? And this black hole was in a binary system, so would not the black hole eat the star, and increase it's mass from there?

[K^2]

If the planet orbits far from binary, the binary appears as a point-mass (required for stable orbit), so it doesn't matter if it's a black hole + star or just black hole with combined mass. If the black hole is far away from the star, and the planet orbits just the star, then the planet would be ripped away and pulled into a dust cloud long before black hole pulls enough star matter to increase mass by any significant quantity.

There is a factor of falling onto a black hole, but you need to be within something like 3 Schwarzschild radii for the orbit to actually decay at a fast rate. So it's all very strange. The only way it can happen is if something knocks the planet out of star's orbit and sends it towards the black hole.

We can sort of know what will happen to a wormhole in the vicinity of the black hole. We have Einstein's Field Equation, general forms for traversable wormholes, and the curvature of space-time around the black hole. If we treat whatever happens in the wormhole as a perturbation, we can get an approximate solution for wormhole near black hole. Not exact, of course, but it would give you a very good idea of what would really happen.

Has anybody done these computations? I don't know. I know that whoever wrote that episode doesn't understand any of it, though.

[StargateWatcher]

I can't recall any specific mention, although I do recall that episode in which O'Neill infiltrates the NID's off-world gang of thieves in order to recover stolen artifacts and shut them down. When the Asgard arrive at the NID base and things start dematerialising, O'Neill advises them to return to Earth rather than be beamed up and his parting comment to the NID operatives is something like "I'll hold it open." Then we see him arrive on Earth, but here's the thing: I can't remember if he re-materialises completely and then turns around the pushes his arm back into the event horizon (to hold it open because it won't close while matter is still passing through) or if he manages to step through the gate and leave his arm held out behind him so that it hasn't re-materialised yet. I think it was the former (stuck his hand back in) which unfortunately makes the basic functions of the stargate even more confusing! The second option would make more sense.

And of course, there are all those occasions on which the gate was dialed and the iris was closed before the kawoosh. They could get away with that on Atlantis because we don't know if the kawoosh can penetrate a force field, but pretty sure the iris should have been disintegrated.

As for bulging event horizons, the first explanation is that it's more cinematic. The second might be that it was an optical illusion visible only to the human eye and only if you were able to look at it from the side (which, as I recall, is the only camera angle from which we as viewers were shown this effect. All the characters would have been viewing the event horizon from directly in front of it - or above it, considering the direction of gravity at the time).

regarding the viewer's viewing angle affecting the kawoosh effect released: I'm pretty sure viewers viewing it from a frontal angle can also see it b/c in one episode when SG-1 tried escapin from a prison-planet, they were bout to depart thru the gate when the gate activated, they knew the event horizon was about to bulge out, n ducked

[StargateWatcher]

they have mentioned several times on teh show about how the iris works it is only like a few milameters or fractions away from the even harrsion thus stoping the creation of the kawooosh its technobable that has bene mentioned several times

u got me thinkin: how come the event horizon initially forming n bursting out will destroy lving matter but not inanimate matter like the iris-composing trinium?

[Mike.]

The kawoosh doesn't form at all behind the iris because there's no room for anything to materialize there. It's so close to the puddle (3 micrometers) that only things like radio waves and very small subatomic particles can come into existence.