Statistics: Posted by Hornblower — 22 Feb 2018 16:01

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EDIT: The video:

Statistics: Posted by midtskogen — 22 Feb 2018 14:07

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How does that break the symmetry? I'm gonna guess, unless I am wrong, that you mean a changing orbit over time. Wouldn't two spiraling-inward planets still have this symmetry regardless?

Watsisname wrote:

Qr Bbpost The geometry of space-time is Minkowskian. This is not in itself hyperbolic, but it does have important features of hyperbolic geometry. To see this, it is useful to start in the space-time of special relativity. Expansion of space over time is just an extension of that, where the spatial component grows with time.

I guess what I mean is... If I looked farther out, all the way to the universe's horizon, would it not appear anti-hyperbolic? The farther away things are, the larger they appear, and the less space there is? And then if I look "inwards", referring to a negative distance in spacetime where the distance away from me still grows but referring now to a future time coordinate, would the future horizon now look exponentially larger? The future horizon, to clarify, being what you would see if you saw further in time the farther you looked (negative distance). For me, a flat spacetime refers to a Euclidean-flat, the angles add up to 180 and follow Euclidean rules, "flat". Hyperbolic being that the angles do not add to 180, less than, and the observed phenomena is more space over distance. When I say anti-hyperbolic, I mean at least, where the phenomena is the reverse, where you get less space over a distance. So for me, more space over distance sounds like hyperbolic, yes its Minkowski space but our universe is not eternal so its size changes over time, and if you include time in the definition of flatness, it does not sound flat.

Statistics: Posted by Terran — 22 Feb 2018 09:25

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Statistics: Posted by Watsisname — 21 Feb 2018 22:18

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Qr Bbpost But if some property is discovered or theorised that prevents the ultimate collapse, that wouldn't kill general relativity if it doesn't affect the properties outside, would it?

No, but depending on where/how the collapse is halted, it may be more or less surprising and difficult to reconcile with general relativity. Suppose for example that the collapse is somehow halted just after forming the horizon of a supermassive black hole. This would be a serious contradiction to principles of GR, because the space-time curvature at that point is still very weak. Nothing terribly exotic is happening to the space-time there, so GR should still be perfectly valid in predicting continued collapse.

Whereas what we expect is that GR's core assumptions (like space-time being smooth on all scales) must break down near the singularity condition, since they contradict principles of quantum mechanics. It would not be too surprising at all if this turns out to be how singularities are removed.

In either case (whether something surprising happens that requires revising general relativity, or if the expected turns out and we develop GR into quantum gravitation), I would not say that GR is killed so much as

Terran wrote:

Sure, although I am not sure how useful that would be for understanding a black hole's properties. In addition to the volume not being invariant, it is generally also not time-independent. In particular, you could choose to define the

Terran wrote:

The geometry of space-time is Minkowskian. This is not in itself hyperbolic, but it does have important features of hyperbolic geometry. To see this, it is useful to start in the space-time of special relativity. Expansion of space over time is just an extension of that, where the spatial component grows with time.

The space-time of special relativity is flat (the spatial component of it is Euclidean) with a time component that does not merge with it in a Euclidean way (so it is not like Euclidean 4D space). It has the metric ds

The quantity ds

Another key property of the space-time interval is that it is invariant. All observers agree on the space-time interval between two events. So if you measure space and time coordinates of events and build a space-time map, and then move into a different reference frame, the space and time coordinates of events will change, but they must change in a specific way in order for the space-time interval to remain the same. That transformation will be along hyperbolas. To see this, think of the curves generated by y

We might ask of other types of space-times, like for the large scale expanding universe (FLRW metric), or around a spherical mass distribution (Schwarzschild metric), or a rotating black hole (Kerr metric). The

Terran wrote:

Qr Bbpost Finally, is there a symmetry in gravity-bound systems? Two planets orbiting for instance, if we traced out their past and future, wouldn't reflecting over the time axis not change anything?

Absolutely, provided there are no damping mechanisms (gravitational wave emission, for instance).

Statistics: Posted by Watsisname — 21 Feb 2018 19:39

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Statistics: Posted by DoctorOfSpace — 21 Feb 2018 14:57

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Qr Bbpost It was theorized as a solution to an outstanding problem in the standard model, and it was verified by experiment. That's as close to necessary and reasonable as anything gets.

My concern is that all they did was predict a particle and observe it, and did not verify its properties. So far what I have read on the Higgs mechanism, there is a lot of talk, a lot of math, but I see nothing saying "look, this is what it does", just "this is what it should do"... What's concerning to me about that is that they could easily get the properties of a particle and the circumstances of its stability mixed up, being able to predict a particle, but not its properties. As in, like correlating a planet's orbit in a resonance with its composition, sure it can be accurate, "there is this resonance, so a planet should be at this distance", and it could align with composition being that different materials exist differently depending on its distance to the star, but the correlation is actually two separate things. Just concerned, thats all.

Watsisname wrote:

Qr Bbpost If you recall from special relativity that simultaneity is relative, this means that different observers have different notions of what constitutes a simultaneous slicing of the space-time. They will have different definitions for "constant time" slice with which to define the volume enclosed, and for a black hole they will yield different answers. It may even be zero!

Hmm... Would it be possible to find the volume for every possible observer?

Watsisname wrote:

Qr Bbpost I don't mean for this to sound condescending, but what's more likely is that you don't understand it at a sufficiently technical level to be able to make sense of it.

I do not. But I hope someday I will! Believe it or not physics is my worst subject, partially due to the fact that I only use algebraic notation in my math and cannot comprehend the other notations (which people around me seem to get immediately :/), but this is also why I am so persistent. But something about this is different, often my mistakes would be not realizing something, or looking at things incorrectly, but something about the Higgs mechanism feels off. Aside from the weird natures of the time variable neutrinos and some how defined difference between a Photon and Gluon, I fundamentally do not understand the Higgs field. The boson itself is reasonable, what it does seems to contradict too much for me. Perhaps, by learning more, I will come to understand its nature and comprehend its existence, but out of everything, it is the most strange. The very process which the universe came into existence would make far more sense than the Higgs field, which could be said that since it has happened it is consequential to some process, that, at some level, makes sense. I just am concerned that we might be seeing the right things but saying the wrong perceptions, idk :/

And as always, leaving off with a question...

Is spacetime hyperbolic? I asked the question on stack exchange but got ill reception on it... I think either people misunderstood my question, or I misunderstood their answers... But what I mean by hyperbolic, is not the actual geometry of space, but rather of space over time. If the universe exponentially expands, if observed past to future at once, would it not appear to be hyperbolic? Less space back in time and more space forward in time?

Finally, is there a symmetry in gravity-bound systems? Two planets orbiting for instance, if we traced out their past and future, wouldn't reflecting over the time axis not change anything? It should be the same system if it was right handed or left handed in time, so would this be a real symmetry or can it be violated?

Statistics: Posted by Terran — 21 Feb 2018 10:16

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The reason general relativity predicts a singularity at the center is that, once a horizon forms, nothing can prevent continued collapse. Where this prediction probably breaks down is on a scale where quantum gravitation effects become important for describing the curvature, which will be extremely close to the singularity point anyway.

Statistics: Posted by Watsisname — 21 Feb 2018 08:31

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It was theorized as a solution to an outstanding problem in the standard model, and it was verified by experiment. That's as close to necessary and reasonable as anything gets.

In science it is not justifiable to dismiss an experimentally verified model just because you think it doesn't make sense. I don't mean for this to sound condescending, but what's more likely is that you don't understand it at a sufficiently technical level to be able to make sense of it. Neither do I, for that matter! I have not studied the Higgs Mechanism formally and much of it goes beyond my comprehension. My understanding is probably about as good as yours.

Terran wrote:

You can attempt to construct any type of model that you want. That is the joy of theorizing. But if you want confidence that your model usefully and accurately describes nature (and especially if you want to convince other people that it is useful and accurately describes nature), then it must meet the following criteria:

1) It must be mathematically rigorous such that it makes specific, potentially falsifiable predictions.

2) Those predictions must then be verified by experiment.

Terran wrote:

Qr Bbpost Would the real volume of a black hole be smaller than that which is found using the schwarschild radius?

Possibly unexpected answer: There is no real value for the volume enclosed by the event horizon of a black hole! It is not an invariant quantity.

If you recall from special relativity that simultaneity is relative, this means that different observers have different notions of what constitutes a simultaneous slicing of the space-time. They will have different definitions for "constant time" slice with which to define the volume enclosed, and for a black hole they will yield different answers. It may even be zero!

So this particular question does not have a meaningful answer. (Rather, the answer is a good lesson on principles of relativity). That might be unsatisfying, because I think the motivation for your question is to understand how the curvature affects common geometric properties like volume. So let me reframe your question to try to help. It turns out that although the volume enclosed in a black hole is not invariant, the surface area of the event horizon is! (The event horizon is a null surface, so it is invariant to space-time transformations and all observers agree on its value).

The horizon area of a black hole is

Notice that 2GM/c

Recall from the earlier discussion of "reduced circumference" that the radial coordinate

That, I think, is the clearest way to see the effect of the curved geometry on the space. There is more radial distance between nearby spherical shells around a black hole than you would think from the Schwarzschild coordinates.

Statistics: Posted by Watsisname — 20 Feb 2018 16:46

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Statistics: Posted by Himself — 20 Feb 2018 15:05

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Qr Bbpost This model (The Higgs Mechanism) has been verified by experiment, for which the team won the Nobel Prize. It may seem like it makes no sense, but it correctly describes and predicts nature!

My problem with it is that it both is unnecessary and unreasonable. If particles were to "naturally" be "trying" to move at the speed of light, but their fields are interacting with the Higgs Field, "slowing" them down, it would have to be absorbing an infinite amount of energy. To say it "just does that" feels wrong.

Here is a possible way to describe mass and everything without invoking fields. Lets just say that there is something called a "time rate" which effectively is the rate of time which passes for a system described. Now lets propose it has two components, your local time rate (which is the rate in time in your general location dependant on the curvature of spacetime) and then a multiplier. This multiplier changes the maximum time rate away from its "0-value" (effectively light speed), this is dependant on "mass". Kinda like a time drag (but with a medium being spacetime and without a field). This decreased time rate for this particle effectively acts as a gravitational field, which can be used to calculate its mass. All of the particle's properties, along with its mass, can be described in a way that is no different from saying its one particle or another. For if you place an electron and a positron next to each other, or any other particle, but no time passes, they effectively are massless, and no different from each other. Particles get their identities and properties by the paths they trace through time in systems, being part of its own identity as much as it is the name of the particle, like a shape. I don't know why only certain energy quantities and system arrangements would only be stable for a handful of particles rather than a bunch, probably thats where the quantum stuff kicks in. But thats so far what I have, which would not require a Higgs Field Medium.

Heres an abstract one... Is it possible (rather, allowed) for me to describe nothing as a particle? As in... Could I say a nothing-on is a massless particle, with some spin number which it looks the same no matter which direction you look at it, has no charge, and perhaps some other properties... Maybe saying that it can carry certain energy levels that equates to certain particles being in that location, it can (like a photon) have a type of mass that allows for it to be considered as a singularity under the right conditions, and so on?

And one final one... Would the real volume of a black hole be smaller than that which is found using the schwarschild radius? As in, if we just consider that the volume an event horizon takes up, just from the schwarschild radius, we would just find the "euclidean" volume. But if we consider volume, not the space the black hole takes up, but rather the actual volume inside the black hole. Would it be less than or more than the euclidean volume. To clarify, volume, being the amount of space that can be moved through, and which the distance between each point is measured in the same scale of unit, being that spacetime is warped, how does this affect the internal volume?

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Statistics: Posted by Terran — 20 Feb 2018 09:45

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To explain: the neutron star merger was detected by 3 gravitational wave observatories, which provided smaller uncertainty for the location of the source on the sky: down to 28 square degrees. This is still a pretty big swath of sky, but

The other benefit, and what you are probably remembering, is that this event also had a fairly close distance as determined by the waveform: a luminosity distance of 40Mpc, with an uncertainty of +8 and -14. (So it could be anywhere between 26 and 48Mpc). A big uncertainty, but not very far away. There aren't so many galaxies that lie in that volume of space. So it was not difficult to determine a match with the electromagnetic counterpart (kilonova).

For comparison, the first gravitational wave event had a luminosity distance of 410Mpc with uncertainty of +160 and -180 (between 230 and 570 Mpc!) and region on the sky of 600 square degrees.

Statistics: Posted by Watsisname — 19 Feb 2018 15:39

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I might be remembering incorrectly, but didn't they say that the galaxy was identified because it has the right distance?

Statistics: Posted by midtskogen — 19 Feb 2018 11:46

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