/sci/ - Science & Math

Reading threads like these literally makes me dumber. OP, I award you no points, and may god have mercy on your soul.

The three points lie on the plane. Construct two vectors: one pointing from (0,0,0) to (3,3,0) and one from (0,0,0) to (0,2,2). The cross product of these vectors will be perpendicular to both of them (and therefore also to the plane). You can use the original normal vector, the new one, and the cross product to find the cosine of the angle between them.

>>4297493
You can do the calculation yourself:

<div class="math">\frac{d^2 x^{\mu}}{d \tau^2} + \Gamma^{\mu}_{~ \alpha \beta} U^{\alpha} U^{\beta}=0</div>

You can look up the Christoffel symbols for the Schwarzchild (or even Kerr) metric on google. They shouldn't be hard to find.

>>4296556
Mass/energy/momentum tell spacetime how to curve. Things then follow "straight" worldlines through that curved spacetime.

>>4296561
What would you accept as an answer to a why question? If I told you that energy warps spacetime because blah blah blah, you would still probably say "thats HOW it works, not why." There is no answer to the question because haven't allowed any room for it.

>>4296530
>>4296531

I don't know what these idiots are talking about, but we have a very good idea of how gravity works. The stress-energy tensor is equal to a differential equation of the metric tensor. Objects then follow geodesics through the space defined by the metric tensor.

>>4282219
No, they're younger.

>>4281698
That's what we've been saying the entire time...

>>4281669
That... makes no sense.

>>4281583
Photons don't have a rest frame. Everything you just said makes no sense.

>>4281573
Yes they are. You will be able to lower the chain up to the horizon by allowing it to freefall, but as soon as you start to put any tension on it the chain will break.

>>4281556
No. Try to come up with a way of doing this; you can't.

>>4281566
Forget the rubber sheet analogy. It's retarded and will only serve to confuse you.

>>4281528
"Stationary" is a relative term. A particular reference frame would need to be specified in which the rod remains stationary.

Regardless, it is a non-physical object that will only serve to generate good troll physics.

>>4281535
>Tital forces at the EH are not strong enough to rip the chain apart.

That's where you go wrong. They are ALWAYS strong enough to rip the chain apart. Even at the horizon of a supermassive BH the tidal forces will rip the chain apart as soon as you start trying to resist freefall motion.

>>4281493
I'm not really sure what the question is. The singularities combine, if that's what you're asking.

>>4281504
>'universal stillpoint',
>/tg/'s infamous Absolutely Immovable Rod

I'm not familiar with these.

>>4281472
You're applying naive Newtonian ideas to black holes. Do you know what extrapolation is?

>>4281464
Yes, I'm aware. You still can't "uncross" the horizon. Freefall objects experience maximal proper time, so resisting gravity will actually reduce the proper time between crossing the horizon and reaching the singularity.

I'd like to know where you got this idea from in the first place.

>>4281431
No, the correct statement would be that the singularity lies in the future of every worldline withing the horizon. An object CANNOT be "propelled" back outside the horizon. In fact, resisting the pull of gravity will only make you die faster.

>>4281420
No, because that's correct.

>>4281367
Not everything is relative. Perhaps you'd like to explain what you mean.

Anyway, the name comes from Galileo's Principle of Relativity. I suppose a more appropriate name for GR would be "General Covariance."

>>4281341
No. The ship needs to accelerate to get back to earth, so it can no longer claim to be an inertial reference frame. The ship experiences less proper time than someone on earth.

Look up the Twin Paradox for more information.

>>4281332
"Metric engineering," as it's called, usually requires some form of negative energy. I'm not even sure if negative energy is physically meaningful.

>>4281292
GR is internally consistent as far as I know. It is incompatible with QM because it assumes spacetime is an infinitely differentiable (smooth) manifold.

>>4281294
It used to annoy me, but I've since stopped caring. Nobody wants to be a buzzkill. Besides, listening to imaginative (though frequently naive) ideas can be inspiring.

>>4281261
Nothing. That's perfectly valid from the rest frame of the spaceship.

>>4281262
It's a pseudo-force in the context of general relativity. In the context of other theories, it is still a force.