1

New Theories / Re: Can conscious thought act on matter?

« on: Yesterday at 18:19:23 »

Then again: Can conscious thought act on matter?
 What do you expected? 😂

 Proof? Ok.

 My brain thinks.
 My brain move my hands.
 My hands shape a ball made of Clay.

The clay wasn't necessary. The hands moved. That's enough to illustrate the point. I totally agree. The question was asked in a classical manner, and that's a classical answer.
So the question now is, what's all the fuss? Who would deny that?

2

Physics, Astronomy & Cosmology / Re: Why is the Barycenter Equation expressed in terms of mass?

« on: Yesterday at 06:09:19 »

The further the Earth/Moon barycenter from the center of the Earth, the greater the Earth’s ‘wobble’ due to the moon.
Given r=a/(1+(m1/m2)) then, apparently, the Earth’s barycentric wobble should increase as the Moon moves away from the Earth.

That it does.

But surely- as the Moon moves further away from the Earth- the force of gravity between them should reduce with the square of the distance- so, shouldn’t this reduce the Earth’s wobble?

The gravity between the two does decrease with distance, but that only reduces the acceleration of each object. It also increases the orbital period, so it undergoes that acceleration for a longer time, which accounts for the greater total distance traveled (the wobble). So if the moon doubles the distance it has to travel, so must Earth, even though the force drops to a 4th that of the closer orbit.

Should the equation for the barycenter not be expressed in terms of the force between the bodies?

No. The force between the two is equal an opposite, but the barycenter is not halfway.

As the Moon continues to move away from the Earth, at some point (Hill Sphere?) shouldn’t the barycenter start to move back towards the center of gravity of the Earth?

Given just a two body system, there is no hill radius, and the barycenter is always a fixed ratio of the total distance divided by the respective masses, or a little over 1% of the total distance. That means if the moon was a light year away (but still orbiting), the barycenter would be just over 1% of a lightyear from the center of Earth.

Of course Earth does have a finite hill radius because there are more than two bodies in the universe, so if the moon gets far enough away, it will just simply cease to orbit Earth and will make its independent way around the solar system, and there won't be a barycenter between the two at all.

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Physics, Astronomy & Cosmology / Re: Is the inverse square law only approximately correct in general relativity?

« on: 26/06/2022 02:58:44 »

Suppose it was something else like Beta particles being emitted isotropically by the source.   Why would that not follow the 1/r2 law for the bombardment intensity received on the surface of a sphere held at a constant metric distance (a radius) r from the source?

Presuming you didn't do anything funny like put detector/source at different potentials, the inverse square law would work given this constant r (say both held at opposite ends of a stick).  Space expansion would make no difference. Dark energy probably would, but that counts as 'something funny' just like gravity does. Dark energy would put tension on the stick. Space expansion would not.

If we assume that the particles are traveling at (say) c/10, then there will be an event horizon beyond which these particles will not pass, because space will be expanding faster than c/10 by the time they got there.

OK, but if distant detector is held at constant distance from this emitter, it will cross over that 'event horizon' (towards us) and the particles will get to it.

What you're talking about isn't the event horizon, it's the Hubble radius, the distance where Hubble's law yields c. The event horizon is a little further away from that, and it has to do with acceleration, and is not a function of the current expansion rate like the Hubble radius is.  So a beta particle moving at 0.1c would get at most a 10th of the way to the Hubble radius, and would take an infinite time to do so.

This event horizon will be much smaller than the event horizon for light (which defines the limits of our observable universe).

The light event horizon is about 16 BLY away. Current radius of the visible universe is about thrice that, so they're very different things. The latter is all the material in the universe which at some past time might have had a causal impact on a given event (Earth, here, now).  The event horizon is the comoving distance of the nearest current event from which light can never reach here in any amount of time.

After all, the size of our observable universe is not at a fixed distance - it expands at the speed of c.

The Hubble sphere expands at c (by definition). The visible universe expands at somewhat over 3c, which is why we can see galaxies that are currently about 32 BLY away (comoving distance).  The event horizon is barely expanding at all.

so (in principle) there are distant galaxies that people on Earth could see today, but
 which will not be visible in 10 billion years

Hate to disagree, but new galaxies become visible over time. The most distant ones were not visible several billion years ago, even if one used the best telescopes. Yes, the galaxies cross beyond the event horizon, but that doesn't mean we can't see them any more than we stop seeing somebody falling into a black hole.

The inverse square law is about the intensity received at a distance, r, from the source.   That is a physical distance, so it is determined by the metric.   It is not determined by reference to a difference in the values assigned to locations in the co-ordinate system we commonly use to describe an expanding universe.

Just so, yes.

The usual co-ordinates used in an expanding universe are the called the co-moving co-ordinates.  Galaxy 1 can have fixed co-moving co-ordinates and it's tempting to say it has a fixed position.   Galaxy 2 can also have fixed co-ordinates and we can be tempted to say it has a fixed position.

Right. The rate that a given galaxy changes its coordinates is called peculiar velocity, and the peculiar velocity of almost all objects is quite low, a few percent of c at best.

If you posit some particle that travelled at c/10 (and didn't slow down)

In an expanding metric, the paricle will slow down without some force maintaining its peculiar velocity. Newton's laws only work in a static metric.

4

Just Chat! / Re: Test of the Poll system

« on: 23/06/2022 01:41:44 »

I've never put in a poll, not finding them particularly useful, but not for lack of knowing how.
I've modified a poll (to add a reasonable option to a list of all unreasonable ones), but that's it.

You suggests using one to reduce the number of replies, or at least reduce the need to read them, but unless you read them all to tally a count of opinions expressed, it doesn't save much time. Most people (myself included) don't vote in most polls.
Science doesn't work by popular opinion, especially on this site which has more than its share of dissenting voices.

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Physics, Astronomy & Cosmology / Re: Does The Gravity Of A Black Hole Travel Faster Than The Speed Of Light ?

« on: 22/06/2022 02:00:15 »

Space and the way things behave in space follows the physical laws of science.   Changing co-ordinates can't change that.

Agree, but this contradicts what you said before. I had needed (and got) some clarification before knowing which one was the contradictory one. It concerns your alternate metric with T  =  x + t.

Consider dropping a scientist and well stocked lab into some arbitrary place and time in the Universe. 
...
Specifically, they can choose to use some arbitrary co-ordinates but they will know and can tell that the metric isn't Minkowski in those co-ordinates - it it will only take them a few experiments to determine that.

This suggests that the 'way things behave in space' can be changed by a coordinate change. They're apparently performing experiments to empirically demonstrate an abstraction (their alternate choice). No experiment will show that, because as you say, the choice of abstraction can't change the way things physically (empirically) behave. One can tell the metric isn't Minkowskian simply with a pencil and paper. The experiments will all be unaltered by the choice.

We seem to have a fundamental disagreement about the line between arbitrary abstraction and objective (and classical) physical fact.

However, some co-ordinate systems make things seem unnatural when expressed in those co-ordinates.   E.g. Objects move around in circles in some some co-ordinates but physically they are always obeying Newton's laws, it's just that the chosen co-ordinates don't describe an inertial frame.

Newton's laws are local simplifications and what might be a natural coordinate system for local description will be inevitably entirely unnatural for one's larger purpose. Yet again, we're not discussing local physics here, so choosing a nice neat local CS is inappropriate (not a natural choice). Most of your post focused on this 'LIF', but the 'L' there makes it unnatural for a non-'L' description unless spacetime remains effectively flat between observer and measured event, which in this scenario is not at all the case.  Your scientist with the well stocked lab isn't considering anything in the lab, and he isn't even taking any actual measurements. The question wasn't 'what will the distant observer measure?'.

That Schwarzschild time, t, isn't unimportant or arbitrary to the scientist.  That co-ordinate t is what they will experience as local time (if they hold still).

This is wrong. How does one 'experience' any kind of abstract time?  One experiences proper time. That's the only time that's physical. One does not 'experience' the time for some worldline not in one's presence.

     There's no disagreement here.  The original sentence had the phrase "if they hold still" in it and the distant scientist is located on a surface of constant radial co-ordinate r, their entire worldline is on that surface.   For the distant scientist, the proper time interval they experience (between two events in their worldline) = the difference in the Schwarzschild co-ordinate time, t, between those two events.[/quote]OK, I see what you mean. The same could be said worldline a meter above the event horizon, despite the objective massive dilation of the lower time relative to the distant time.
Yes, in answering 'when does the rock cross the EH?', I was using time T (not t) to express the simultaneity since T is not singular. It may take some arithmetic, but one can very much compute distant-observer-t from a given T, even if T isn't something the guy's clock on the wall measures.

As shown on the Kruskal diagram (which was produced in paintbrush and took what seemed like hours before you criticize it again for not showing irrelevant details like the singularity).

Fantastic job then. I never managed reasonable curves with the primitive tools I have. I'd have just grabbed one from the web.

Anyway, the event with the rock crossing over the EH is never in the past light cone of the distant scientist

Of course not. It wouldn't be an EH if it was.

  So that event never causes an effect for the distant scientist.

None claimed.

This is getting to the crux of matter:   We orbit around Sagittarius-A* which seems to be a big black hole, so we are that distant scientist, following a worldline that lies (more or less) at constant Schwarzschild radius r.   Is it possible for that black hole to engulf a rock and grow, so that it's mass parameter is now larger, during a finite amount of time for us scientists?

Hard to say, since the question is abstract, not physical. Your scientist might pick a metric that is singular at the EH, but that metric cannot actually describe the situation. The LIF doesn't work when there's gravity involved at all. The Schwarzschild metric doesn't work in anything but a static black hole. Even the distant orbiting thing violates that if it has any mass.
So I think I discussed this before. Absent a metric describing an infalling mass, one has to simply approximate and imagine it, possibly giving wrong answers. More below, but your comments are on point.

Will the mass parameter of Sgr-A ever change in my lifetime?

If it didn't, it wouldn't have a mass parameter in the first place. Based on that alone, you have only two choices, a singular infalling metric that either allows mass at all, or one that doesn't. The rock (and everything else in its history) goes in or it doesn't. Keep in mind that the question isn't physical. It is strictly an abstract one unless one asserts physicality to a particular abstraction.

(Assuming that I do not ever get off planet earth and do something like travel fast or travel toward the black hole etc).   It makes little practical difference if the gravity we experience from the centre of the galaxy is always caused by a black hole of Mass parameter M plus a small rock close to the event horizon with mass m,   or if eventually we just experience the gravity from a Black hole with mass parameter M+m.

A black hole with no mass at all, but a lot of crap almost in it is (must be) empirically indistinguishable from a black hole of mass <a lot of crap>. Thus we will very much experience M+m because m is there, inside or not. What we experience isn't abstract.

However, there is a small difference, one is symmetric, the other is not.

Yes!  That's a huge problem with plan B above (it all stuck on the surface).  Suppose we start with a solar mass black hole (about 3km).  Now we take a concrete cylinder 100m in diameter and massing 100 stars. It's a super-long cylinder. We jam that thing into the small black hole and it all sticks to the non-rotating surface in one place. That puts all the mass off to one side, not centered at all. That would violate the whole no-hair thing. The black hole (after the bar thrown in) is still stationary in the frame of the system CoM, (which is nowhere near where the small black hole was at first). Where is the mass? All on the one side, or centered on the radius?  It can't be the former since an off-center mass would be empirically detectable, not just an abstraction. Right?  No? My logical seems a little naive/Newtonian, so maybe I'm just doing the mathematics wrong.

So maybe a tiny mass gets stuck, but the next tiny mass (on the same side??) grows the EH, swallowing the first. You drop in a big rock, and all but the trailing bit gets in, at least relative to this chosen metric.

6

Physiology & Medicine / Re: The crucial ingredients of CBD:

« on: 21/06/2022 17:41:25 »

I'm just waiting for the spam advertising.

Already deleted. Already banned. It was in the signature.

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Physics, Astronomy & Cosmology / Re: Is the inverse square law only approximately correct in general relativity?

« on: 20/06/2022 06:14:01 »

Any idea what distances such a thing would happen at?

It's kind of like asking when normal velocity addition stops working and when relativistic addition must be used. It depends on the precision you want, but right away if you want infinite precision.

For the small scale (the black hole example), we talk about 'local' tests, that say there isn't one to distinguish acceleration from gravity. So the answer to the question is the distance needed to distinguish the two cases, which of course depends of the precision of your instruments.

On the large scale, I would say 'far enough that dark energy is measurable'. That means I have two small pebbles held apart at distance X by a rigid rod, far away from gravity sources. Now you let go of the pebbles. In inertial space, they'll stay put per Newton's first law. But dark energy will accelerate them apart (and normal space expansion will not). If you can measure that, the inverse square law is also probably measurably off. Dark energy messes up all the formulas, and is the primary reason inertial frames (and their rules) cannot be global.

8

Physics, Astronomy & Cosmology / Re: Is the inverse square law only approximately correct in general relativity?

« on: 20/06/2022 03:57:30 »

It's an approximation, a leftover from Newtonian physics.
It falls apart at extremes. For instance near a black hole, the inverse square law has your weight (force required to maintain a constant altitude) approaching some finite quantity, where in reality, at the EH, no force is enough to do that.

It also falls apart for great distance since spacetime isn't Minkowskian at the largest scales. There cannot be a global inertial frame, and the inverse square law I think is a property of an inertial frame.

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That CAN'T be true! / Re: Does the IVO thruster violate Newton's third law?

« on: 19/06/2022 23:54:22 »

Inertial propulsion is the "graal" everyone try to discover because it can be achieved without any loss of mass.

This is a claim of reactionless thrust, not 'inertial propulsion'. And the word is 'grail', not 'graal'.

But if you can retrieve electrical energy (from the sun or from nuclear reaction...), you can always recharge your battery.

Indeed. If I had reactionless thrust, I could use it to generate more electricity than it costs, so no sunlight or nuclear reactor needed. The world energy problem would be solved. Isn't magic great?

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Physics, Astronomy & Cosmology / Re: Does The Gravity Of A Black Hole Travel Faster Than The Speed Of Light ?

« on: 19/06/2022 16:19:32 »

   As you have implied in several earlier posts, the distant scientist cannot change the way her local space behaves or the laws of physics in her local space just by changing her co-ordinates.

But you are doing this in your prior posts, implying that 'the way space behaves' is a function of your frame dependent abstraction, and not a function of the physical geometry of the spacetime.

However space isn't Mnkowski space in those new co-ordinates.

Here you changed your coordinate system and suggests that somehow the spacetime is different, but when I do the same and you say it hasn't changed. You need to be consistent. Is spacetime being locally Minkowskian an abstract choice, or are you referring to the fact that the physical spacetime is locally flat such that a Minkowskian metric can be meaningfully mapped to it?

So I agree that spacetime hasn't physically changed, but my choice of abstract coordinate system does assign simultaneity to different events, and it is that simultaneity which is under scrutiny here.

They can use Kruskal co-ordinates (T,R, Ω)

I was using (T,X).  There is an r and t that corresponds to Schwarzschild coordinates, but those are different coordinates. The rock reaches the event horizon in finite time T as illustratred in your picture. The singularity has been omitted from your picture, but the rock also reaches that in finite time.

However they can't escape the fact that  R=T is a surface where the Schwarzschild co-ordinate time, t is specified by  t = +∞  and   Schwarschild r = +2GM.

That's right. Different coordinates are singular there, which is why I didn't choose them.

That Schwarzschild time, t, isn't unimportant or arbitrary to the scientist.  That co-ordinate t is what they will experience as local time  (if they hold still).

This is wrong. How does one 'experience' any kind of abstract time?  One experiences proper time. That's the only time that's physical. One does not 'experience' the time for some worldline not in one's presence.

The event where the rock crosses the EH never falls inside a past light cone for an observer on the blue line of constant Schwarzschild radial co-ordinate r shown.

Of course not. It's a physical (coordinate independent) fact that and event on the event horizon cannot causally effect one outside that horizon. Light cones (physical) do not define simultaneity (abstract).

That's fine.   Everyone agrees that there is an event with the rock on the event horizon.

Not the people using the x,y,z,t or say the cosmic coordinates. There are people that very much disagree that the rock physically crosses the EH, and that the experience of falling in would be cessation of existence right there. That's a crock of course, it leading to inconsistencies.

11

New Theories / Re: Can conscious thought act on matter?

« on: 18/06/2022 16:22:31 »

This mean, the people can change the result of the quantic experiment (making the wave function collapse !), only by thinking about it, elsewere on earth, as if some experimentator would direct interact with the phenomenon at the place of the experience.

This is just decoherence, the effect of which travels at a good percentage of light speed. If it was 'caused' by some specific distant guy thinking about it, then they must have been able to show that the same system would remain in superposition (not collapsed) indefinitely if this one distant guy was not thinking about it. They've demonstrated no such thing.

There are plenty of examples of systems actually kept in superposition for extended times, despite the system being thought about continuously by the people setting up the experiments.

No, I have not watched the video. You-tube videos are not evidence of anything. If you haven't posted the actual claim here, then it isn't important enough to discuss.

12

New Theories / Re: Can conscious thought act on matter?

« on: 18/06/2022 14:55:33 »

and a New Experiments Show Consciousness Affects Matter.

This is pretty trivial to demonstrate, even without all the superfluous capitalized words.
If consciousness could not affect matter, then you'd not be able to type a description about it. That was trivial, not requiring '(many years of very impressiv tests)' at all.

team explain how they have prooved (many years of very impressiv tests) that someone can act on some quantum phenomenon

Likewise, if I observe a normal distribution of light in an experiment, I paint my house one color, but if I observe an interference pattern (a quantum phonomenon), then I paint the house in stripes. I have thus acted on some quantum phenomenon, and it again didn't require 'very impressiv tests'.

So perhaps nobody is being clear as to what extraordinary thing is actually being done beyond what I've described above.

13

Physics, Astronomy & Cosmology / Re: How would we know whether space,time or spacetime were continuous or discrete?

« on: 18/06/2022 06:06:41 »

a computer simulation... implementing one would typically need to implement a state to keep track of. That means no spacetime. Presentism. Faster-than-light causality. Objective state.  All the things I detest.

You seem to be imagining a computer simulation run on a uniprocessor, in which a single processor needs to access the entire state of the universe.
...
The fastest computer architectures tend to be grid computers, which only have really fast communication with their immediate neighbors,
- A 2D grid CPU has 4 immediate neighbors
- A 3D grid CPU has 6 immediate neighbors
- A 4D grid CPU has 8 immediate neighbors
- And yes, researchers have investigated 5+D grid CPUs with 10+ immediate neighbors

I made no mention of an architecture optimized for speed. A simulation has no inherent speed requirement and can be implemented by a guy with pencils and a lot of paper if you want, or worse, by a Turing machine. Even say a 3D grid architecture with millions of processors per dimension would still require a model of:
Presentism. Faster-than-light causality. Objective state.  All the things I detest

It would be interesting to attempt a program that modeled locality, state expressed as entanglement/decoherence, and maybe even a way around the presentism. That last one is admittedly the hardest one to ditch.
 

However, the last uniprocessor to be dubbed "fastest in the world" was the Cray 1, which only held the title until 1982, when it was overtaken by a multiprocessor computer (also from Cray).

For the record, a Cray 1 (I've seen one) was a SIMD machine, which means single instruction but operating on hundreds of data elements at once, so it's very parallel despite apparently being classified as a uniprocessor by somebody. It is thus a fantastic vector processor for crunching simulations of things like the weather, but it would not be particularly good at chess, which would better be served by some sort of cloud configuration.

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Physics, Astronomy & Cosmology / Re: Does The Gravity Of A Black Hole Travel Faster Than The Speed Of Light ?

« on: 18/06/2022 02:49:18 »

Kindly accept my apologies below where I seem to be objecting to things that are perhaps not important here.

Suppose one person is using the co-ordinate system  (x,y,z,t)   which just turns out to be a set of co-ordinates that behave much as you'd expect.  Specifically, their space is locally Minkowski space in those co-ordinates.
    Another person can choose to use different co-ordinates with this transformation between the co-ordinate systems:
a =x  ; b = y  ;  c = z
T  =  x + t
   So that their co-ordinate system will be written as  (a,b,c,T)  with  a,b,c exactly the same as x,y,z.

OK, so you've assigned different coordinates to those same events using a system with non-orthogonal axes in which light moves at infinite speed in one (and only one) direction (which makes for an interesting sync convention). It indeed doesn't conform to the Minkowski metric, but the space itself is no different, just different abstract coordinates assigned to the physical events. The mathematics got more awkward, but not impossible.

The scientist should have no difficulty identifying a suitable, natural set of co-ordinates because space won't be Minkowski space in very many co-ordinates.

I didn't suggest anything not 'suitable'. In fact, I chose one far more more suitable. There's questions (about objective events) that cannot be asked using those coordinates, but which can be asked using different ones. That makes the 'different ones' a better choice for this scenario.

Specifically, they can choose to use some arbitrary co-ordinates but they will know and can tell that the metric isn't Minkowski in those co-ordinates - it it will only take them a few experiments to determine that.

This is an interesting assertion: that one can empirically test for an abstract choice of coordinate system without first begging the choice.
I can define a meter to be the length of my toaster, but I'm not sure if I've proven anything by measuring that light speed is now about a billion meters per second (assuming the second hasn't been redefined as well), since I need to beg the new definition of the meter to empirically make this measurement.

They will pick up a stop watch and set it going,  they will say to themselves "that is time flowing in the positive direction".

Ah. Presentist scientists. The stopwatch demonstrates no such thing. Sorry. Just pointing out that they're begging a philosophical conclusion and have not demonstrated anything scientific yet. You can't discuss a black hole using a model where time is something that flows. Any such model denies the existence of the thing.

For example they can pick up the stop watch again and try it but it doesn't record the passage of T,  it only records the passage of t.

If they hold it still relative to the x axis, it measures T. The Minkowskian guys don't get an accurate measurement of t either if the watch is moving. Funny that watches don't measure coordinate time.


My point was the poor utility of said Minkowski coordinates or perhaps Schwarzschild coordinates when considering what's going on with our infalling observer. You seem to be explicitly avoiding that point, concentrating on nice little local experiments instead. Your choice of coordinate system is far more suitable for those purposes, but those purposes are not the topic of this thread.

A scientist at a distance from a black hole (where the rock was heading into) can choose to use Kruskall co-ordinates but that doesn't mean that the scientist won't experience an infinite amount of time pass before the rock reaches the EH. I don't see that there needs to be an objective reality here.

Hey, this comment was on point. Yay!
No, there's never an objective answer to 'what time is it here simultaneous with remote event there?'. Relativity of simultaneity doesn't allow that. But you can ask for instance if an observer is falling into a black hole and looking back at the distant lab with a bright clock showing, what time does he see on that clock when crossing the EH? What is the very last time he sees period?  Both coordinate systems listed above cannot answer that, thus giving rise to the misconception that the infalling observer sees billions of years of the outside universe as he falls in (sees distant clocks speed up) which of course is backwards. He sees them slow down, but never stop.
As for our distant scientist using Kruskall co-ordinates, it very much does mean that he'll experience finite time until the rock crosses the EH. That's what those coordinates are for. He'll of course not see that event ever, but seeing it is an objective measurement, not something coordinate dependent.

I know you (Halc)

Nit: Everyone knows who you're talking to, it being implicit in the quotes to which you're replying. You don't need to do that every time you use a pronoun. Sorry, I'm sounding grumpy now. Don't take this as hostility.

to phrase that another way, are you sure that you (Halc) aren't trying to be the absolutist and suggesting that there would be an objective reality.

Classically, there are objective events. Its only getting down to the quantum level where I would suggests a lack of objective reality. A rock/laser/observer falling into a black hole is a classic scenario. Unruh radiation is not.

15

Physics, Astronomy & Cosmology / Re: How would we know whether space,time or spacetime were continuous or discrete?

« on: 16/06/2022 00:39:23 »

About the dots. I’ve had little time to respond to all that’s been said, but here I go.

I mentioned all the dots being sort of ‘socially distant’ so no pair of them was too close to each other, but it would be better if it was truly random. If we did the nice even but not regular distribution, then a significant Lorentz transform of the dots will bring some dots into far closer proximity. So we once again have a preferred frame where this does not occur, and the point of the random dots was to avoid the preferred frame. So true random, not just somewhat random like the pattern of sheep on your pajamas.

And then there’s the counterfactual thing. The dots (occupied by something or not) seem to be something that exists entirely absent any measurement. This goes against everything I normally prefer. It totally violates locality. I brought up a computer simulation simply because implementing one would typically need to implement a state to keep track of. That means no spacetime. Presentism. Faster-than-light causality. Objective state.  All the things I detest.
I don’t think a convincing computer simulation could ever be done, at least not implemented with the physics we know. So if it’s done, it’s done via higher (more powerful) physics than we can know.

When you measure some quantum object, there is a certain probability that it will be found at one position or another (or one time or another), according to Heisenberg's uncertainty principle.

The principle allows arbitrarily high precision to say position, but at the expense of knowing its momentum. It’s not something you can measure twice if you got it really precise the first time. Then again, I think Planck (not Heisenberg) put hard limits on this precision, and that precision is probably far more coarse than these ‘dots’.

Your proposed construction of discrete events for a discrete spacetime by randomly sprinkling them like dots onto a piece of paper is a little awkward and I'm not sure it achieves very much. 

I actually agree with this. I was just tasting the idea mostly.

This is roughly what you seemed to be suggesting:
     Sprinkle events like dots almost at random on a piece of paper and (just for good measure?) also hold the paper at some random angle to randomise it a bit more, then have time up the vertical and space on the horizontal.

I said that. In reality, a Lorentz transform must be used to rotate the paper. It isn’t Euclidean like paper is.

You suggested trying to start with horizontal lines across the page that are representative of lines of constant time.   However the events don't usually lie nicely on a straight line, so you allow some wiggling up and down to make sure you pass through the nearest dot to what would be a horizontal line.

Sure. ‘Nearly simultaneous’ (if that has any possible meaning) relative to this local frame. Gets pretty ambiguous. How do you decide which dots are near enough and which are at different times? The more picky you get about that, the more distant the possible spatial locations available at that ‘time’, and as time progresses not a whole dot forward, some dots are no longer close enough to the new ‘time’, but others still are. Event A simultaneous with B (in this given frame), and B with C, but A not simultaneous with C. All very contradictory.

Any vertical line that passes through a dot is an x-axis location we can have.

Eventually. Technically dots and lines have no width, so it will be an arbitrarily long time before a random line drawn anywhere ‘hits’ anything. So now we need a ‘close enough’ value that is less than the minimum distance. Another contradiction.

Now we see a problem...  Assuming the sprinkle remains of consistent density and random across every time slice, and time extends up the page indefinitely, then we will always be able to find another possible x-axis location as close as we like to the first one we started with.   Overall the entire x-axis could be divided up into so many lines that it is just a continuous range of possible x-values again.    That's no good, we want some discreteness in our spacetime.   So we're not going to divide the x-axis up as finely as we can... we're just going to do it fairly finely.
    How finely?  As much as you like, just not so much it becomes continuous.

Say it’s a meter apart (a min distance). Sprinkle dots a meter apart (in a grid or randomly) and draw lines randomly through each one perpendicular to a random time axis. It will still be sliced up arbitrarily fine as there is nowhere you can choose an x that doesn’t get arbitrarily close to some dot somewhere. So don’t know where you’re going with this. Only way to avoid this is a flat regular grid perfectly lined up (the preferred frame), in which case you can walk between the trees indefinitely without every getting close to one.

I kind of lost you after that, but it already seems to doom the dot idea.

16

Physics, Astronomy & Cosmology / Re: Does The Gravity Of A Back Hole Travel Faster Than The Speed Of Light ?

« on: 15/06/2022 23:19:34 »

Apologies in advance for disagreeing.

There's no disagreement about frames of reference and co-ordinate systems.

There is if I'm choosing one that isn't singular at the event in question, and you are choosing a different one.

   However, the Schwarzschild co-ordinates (r, θ, φ, t) used by the distant observer aren't just "abstract"[/quote] They very much are abstract. That coordinate system is an abstract assignment of those four values to events, and nothing more. The exact same physical spacetime can be assigned different values using a different choice of abstract coordinate system.

(r,θ,φ) will be a natural spherical spatial co-ordinate system for them (centred at the black hole admittedly rather than being centred on themselves which is a bit unusual but not totally bizarre).

r is not spatial inside the event horizon, and events separated only by t are not time-like separated.

Not when the question is about what happens for the distant observer.

Relativity of simultaneity says that the local time (at the distant observer) at which a distant event (object crosses EH) is coordinate system dependent. So there is no correct answer to the question unless you're an absolutist, in which case you should use the absolute foliation and no other. The coordinates you've chosen certainly do not qualify as an absolute foliation, but then I'm not suggesting one that serves that particular purpose any better.

For the distant observer (holding constant r,θ,φ ), an infinite amount of time must pass before the rock reaches the horizon.

Yes, if you choose the coordinate system you indicate, then the infalling thing never gets to the EH. That's probably a problem since I can think of a few contradictions that result from that, but the absolutists do actually posit something like that, denying the existence of black holes altogether. Coordinates of r <= r_s are not valid coordinates of any real event. Maybe you can get around this by suggesting the EH reaches out due to a 2nd thing dropped in later, but there'd need to be an infalling metric describing it to be sure if this works or not. As I said, the absolutists deny this effect and say the material moves outward as the BH gains mass. I don't know if they've produced a metric satisfying the field equations that supports this, but they're already in denial of relativity, so they probably don't think they have to.

The rock will reach the horizon when co-ordinate t =∞

Not if the BH evaporates before then.

No.   You're deliberately trying to slip something past people here by tacitly switching to the time experienced by the rock.

I'm not.  Everybody already knows what the rock-time will be. That's a physical thing, not frame dependent. The frame of the rock is also a poor choice. I was thinking something like Kruskal–Szekeres coordinates where events for neither the distant observer nor the infalling object are ever singular along their worldlines. OK, the infalling object eventually reaches the central singularity (which might be a line or a plane), but it does so in finite time for everybody. No infinities.

I knew "the last photon" would be mentioned before your reply appeared,  it was just bound to be mentioned.   I think the usual model assumes the emission of individual photons from the rock is random

Yes. I also assume the rock had a light beacon on it, perhaps a well aimed laser. Lots of photons, but there's always a last one.

Then the time when the last photon is received can't be predicted and the distant observer can't be sure that this was the last photon, there could always be one more.

Totally agree. The Kruskal–Szekeres picture of the exact same geometry doesn't suggest otherwise. Said 'last photon' is a physical thing, not an abstraction after all.

Regards ES. Always an interesting conversation. Thank you for that.

17

New Theories / Re: Dark Matter: Energy produces mass or is it submitted to it?

« on: 15/06/2022 15:50:07 »

Is the mass on matter, at any giving instant on time, presented on the interior of the atomic structure?

This was the only question I could find.
Most of the post was not understandable, perhaps due to being a non-native English speaker.

For an atom, most of the mass is due to binding energy of the components. If you feel a need to give that a precise location, I'm good with binding energy being in the 'interior' of the atomic structure.

Or the mass of matter is constantly "given" to it by dark matter on the future frame?

The mass of an atom has nothing to do with dark matter since an atom is not dark.

By that I mean, how one does proof, that the mass of any giving atom, at any giving instant, at any given frame of existence, is not given to it, from the next frame of existence?

Existence doesn't come in frames, certainly not adjacent slices of time, which this wording seems to imply.

Well, I like where that post was heading.

You do? Your post perhaps should be its own OP. It seems to convey that you've actually learned some physics, and the language for that matter, both absent in the post to which you replied.

18

Physics, Astronomy & Cosmology / Re: Does The Gravity Of A Black Hole Travel Faster Than The Speed Of Light ?

« on: 15/06/2022 13:37:00 »

is there a  way to know how large Sagittarius A was when it formed ?

It was probably one or more stellar black holes, most of which are born perhaps twice the mass of our sun. It gets larger by having other mass fall in (which is in abundance in the galactic center, especially in the early formation years.

Sgr-A might have formed a bit larger than a typical supernova event, maybe a stealth event like the dark event Evan describes where a mass just 'blinks out' rather than explodes. Suppose you have a really big star, and it's happily burning away and keeping itself un-holely through that combustion. But rather than quickly using up its fuel and going supernova, the new fuel dumps in far faster than the star can burn it, and eventually it gets so massive that even the fusion going on in its core cannot prevent the gravitational collapse. It blinks out in seconds, and probably produces a black hole massing maybe 20-100 solar masses. That's still way smaller than it is today. It got that big by consuming dust, whole stars, other black holes, and even the occasional galaxy. Andromeda's central black hole will definitely eat Sgr-A in about 20-30 billion years. It's about 10 times the mass of Sgr-A.

...and then.....ewe have TON 618....... 66 TRILLION sol mass !!..... 66000000000 !!!! how is this possible ? did it swallow a few galaxies ?

Lots of them I think. There are insanely large black holes at the centers of superclusters like (from small to large) Virgo, the Great Attractor, and the biggest one 'nearby', the Shapley attractor.

From what I understand it takes a long long time(millions of years ?).....just for one sol's worth of mass to be gobbled up by a black hole.

Sgr-A is a known slow eater (at least currently), but nowhere near that slow. A well-aimed star will just fall straight in, so one can consume a star in moments. Most stars are not well aimed, so if they get too close they just get torn apart and distributed into the accretion disk, some of which is slowly consumed by the black hole below, but the energy released by the infalling stuff adds kinetic energy to the atoms left behind, so much of the material gets shot away at the polar jets.

what kind of commencement did TON 618 have and how large would it have been  when it was ' born '

Probably the same as any other. Probably the larger 'blink out' birth of 20-100 solar masses (a guess). It probably happened earlier than almost any other black hole since for it to get that big today, it had to be near the center of an obscene density of material where stars form quickly and grow too large before they can burn almost any of their fuel. There were probably many such large-but-infant black holes formed, all of which merged after not too long. Determining which one was the original TON 618 itself is like trying to figure out which exact puddle is the head of the Thames river (without a map showing which one they picked).

19

Physics, Astronomy & Cosmology / Re: Does The Gravity Of A Black Hole Travel Faster Than The Speed Of Light ?

« on: 15/06/2022 03:41:49 »

The rock never reaches the black hole event horizon IF the space in that region retains its Schwarzschild geometry.

I didn't say that at all. It not reaching the EH is an artifact of an abstract labeling of the crossing event in the 'frame of the distant observer' which just happens to be singular at the point of contention, making it a very poor choice to answer the question. That abstract coordinate system happens to assign infinity to the EH events, and thus no event outside is after the crossing. But that's just an abstraction, not a physical barrier to the object going in. Choose a coordinate system that isn't singular at the EH and the object goes in without any fuss, in finite time according to everybody.
Schwarzschild geometry has nothing to do with any of that. The metric simply fails to describe a black hole with material infalling, but it gets really close to describing a tiny infalling thing.   

 

Obviously that narrative is very different from the usual version of what happens when something falls towards a black hole and is said to never reach the event horizon - as far a distant observer is concerned.

It all depends on the coordinate system chosen by said distant observer. I can similarly choose a coordinate system where I cannot reach the next room due to a singularity along the way, but I don't actually notice anything when I go there.

I was only stating that this is at least one way that it can happen in a finite amount of time.

How long it takes is a purely abstract duration, not a physical one. Physically, it falls in without fuss, but physically there are no objective time coordinates to events, so the question of how long it takes is essentially meaningless. The proper time is not meaningless.

LIGO have strong evidence for black hole mergers and they do seem to happen in a finite amount of time.

The gravitational waves quickly die down from its peak, well below the ability of LIGO to detect them. But it's the same as any light emitted near the event horizon: it never stops arriving, being red-shifted arbitrarily long. The merger, as observed by a perfect LIGO sensitive to all wavelengths, will be (classically) observed for nearly forever. But that's an observation, not what's actually going on. Observations are physically objective, and are not frame dependent.

So: Very few photons, severely red-shifted: The rock would not "float" near the event horizon, it would just disappear.

Yes, since the image isn't classic, but is quantum. At some point the last photon is emitted that will reach the observer in question. Ditto for the last graviton detected by the perfect LIGO.

20

Physics, Astronomy & Cosmology / Re: Does The Gravity Of A Black Hole Travel Faster Than The Speed Of Light ?

« on: 14/06/2022 21:52:56 »

If you throw a rock into* a black hole does it's mass parameter ever increase?   (does it "get bigger"?)
*into --->  perhaps I should have said towards the black hole, it hasn't actually gone in yet.

This mass parameter is frame dependent, but from your distant viewpoint, the mass/energy it gains from KE is balanced by the PE mass/energy lost from it being at an ever lower potential. So no. A 1 kg rock dropped into a black hole increases the BH mass by 1 kg.

If there is somebody falling in locally with the rock who is in possession of some kind of mass-measuring device, the rock won't change mass along the way. This is a very different frame, but same answer.

So how do black holes get bigger - other than through black hole mergers?

Relative to a distant frame, they grow. A rock never falls into a Schwarzschild black hole, but a BH with a rock dropping into it doesn't conform to the Schwarzschild metric. I'm unfamiliar with the name of a metric describing a mass falling in. Surely somebody must have worked it out.

Your implication that black holes can grow only through mergers suggests that none exist, since it takes two to make one. I do think there are absolutists that suggest the non-existence of black holes since they very much do contradict descriptions in absolute terms.  In order to do this, I think they must suggest that matter stuck on the 'surface' of nothing must actually move outward despite lack of force pushing it that way. Not sure if the people who actually know their physics are on board with that. I've never seen a formal absolutist theory presented as a replacement for GR.
Violation of conservation of baryon number is also a contradiction with such a theory.