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Physics, Astronomy & Cosmology / Re: Does time have more than one dimension?

« on: 19/11/2020 14:19:01 »

I have often wondered about what exactly is it that is moving from the past to the future.

The whole point of spacetime (as opposed to space in time) is that there is nothing that moves from past to future. If there was, then the location of it would define the present, which would be a form of presentism, which is any view that defines a privileged moment in time.

In other words, what is the sense of "now" that we each take for granted, that advances from one moment to the next to define our passage through time?

As you say, it is just a sense, given to you by evolution since without it you’d not be fit to make the predictions needed to survive.

1. Wouldn't being able to draw a loop onto a timeplane allow time travel to the past in a hypothetical universe with more than 1 time dimensions? Isn't paradox free time travel possible?

Depends on what you consider to be time travel. 24 hours ago I experienced Wednesday. Today I experience Thursday. That’s time travel, no?
Under presentism, there is but the one current state of space, and no other state to which one can ‘travel’.  Under a block interpretation, there is no motion, only worldlines, and time travel would I suppose be a worldline that is I guess discontinuous.  I don’t see any inherent paradox in any of that.

What do you mean by there is no backwards in time as there is no forwards in time? What are the implications of time being a volume?

For instance, which way is forwards in space?  If you were locked in a box without windows, how would you determine the direction of forwards?  If space was one dimensional, there’d only be two choices.
Perhaps there is a forwards in time with multiple dimensions.  Any direction with greater entropy (if such a thing is meaningful in this weird place) is forwards and v-v.  There may be several directions which meet this criteria, and locations in time that locally have maximum or minimum entropy and thus lack a choice of both forwards and backwards.

2. How to calculate speed of light in 12 temporal and 8 spatial dimensions?

Yet again, by equating length in all 20 dimensions.  That’s more of a definition than a calculation.  I would have no idea how the operation of ‘calculation’ might proceed with the physics of multiple time dimensions, if it is possible at all in physics where there are not particular solutions to the partial differential equations involved. The inability to meaningfully calculate is a good deal of the reason why an observer is not likely to evolve under such physics.

3. Suppose there is something other than tachyons that travels faster than speed of light, what would its light cone be like and would it allow time travel?

You can make up any story you like. There’s no wrong answer to questions supposing such things.

4. If point in time has no meaning, then what was the big bang? Everything seems to be moving away from everything else, so big bang was probably not a point in space but a point in time(like center of balloon is not on its surface but at its center so big bang time and time dimension in general is the interior?).

You can look at it like that.  The balloon analogy was always meant to be a local analogy, so the universe isn’t really a super-finite surface of an expanding hypersphere.  If it’s radius was 14 BLY, then its circumference would only by 88, small enough to see the entire universe from anywhere since the size of the visible universe is about 92 BLY.  In principle we’d see the same ‘most distant object’ in all directions.
I’ll let Evan answer questions about this ‘black hole cosmology’ about which I know little, let alone buy into. He also gave some excellent replies to 5 and 6.

7. So a clock fell into a black hole in finite time, what happened to the clock then if time ended completely(why would time end by the way)?

Time ending means there is no more process. Nothing to measure.  It can happen for us for instance if the big rip ever happens. It seems unlikely, but if that is the future, then time ends at a singularity just like it began.  But not a point singularity, just a temporal one. It’s a singularity since there is all the equations go to zero or infinities, and there is no meaningful physics as we know it.

Was the clock imprinted onto black hole surface area and led to black hole's growth and would eventually leak out as Hawking radiation?

No imprint. A black hole singularity has no features other than those listed in the no-hair theorem.  Yes, as measured in external time, the mass of the black hole eventually ‘leaks out’ as you put it.
I sort of wonder how a big-rip scenario would handle the black holes existing at the time.

8. How would hypersphere be 5D if our 4D universe has time in its interior

Our universe does not appear to be a hypersphere.  It is best modeled as a flat 4D block of spacetime with local areas of deviation from Euclidean flatness. There’s no ‘interior/exterior’ to it.

Anyway, you said 4D of space, so I figured you were talking about a 4-sphere which has a 4D surface and encloses a 5-ball.

9. Is this analogy correct: We lived in the chromosomes & the chromosomes are parts of us.

We lived in the  chromosomes?  No idea what that means.

But they probably aren't aware of us, neither are all the cells that make us up.

Neither are we necessarily aware of the existence of the larger thing of which we are a part. Don’t assume you’re at the top of that progression.

So it could be some abstract higher dimensionality(maybe more spatial or temporal dimensions) could allow a thing to see all the events across all of space and all of time simultaneously.

Define simultaneously as you use it here then.  ‘Seeing’ is a process, and by definition doesn’t occur ‘simultaneously’.  ‘Seeing’ also seems to require light to go from the thing seen to the observer, and no known photon leaves the universe to get to this ‘thing’ at all, let along all this light converging to a single event.  So that leaves only abstraction, and yes, the entire universe can be considered in abstraction, which is what modeling does.

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Physics, Astronomy & Cosmology / Re: Does time have more than one dimension?

« on: 19/11/2020 09:18:56 »

4. why isn't the big bang happening today since the mother black hole should still be consuming matter and throwing it out into daughter universe at different points in time?

In the context of a hypothetical "Black Hole Cosmology":
- From our viewpoint, we see matter entering the event horizon of a black hole in a big rush during the initial supernova collapse, and then in a steady stream from an accretion disk, possibly with some big spikes when another black hole merges with the first one.
- We know time and space are somewhat mixed up inside the event horizon
- And what happens on the other side of the singularity/Einstein-Rosen bridge/wormhole is anyone's guess, but as an uninformed speculation...
- What if the matter entering a surface in space in our universe (eg the event horizon) appears at a point in time in the other universe (the big bang of this black hole universe)?

5. if gravity changed with distance inversely proportional to r^2.1 or r^1.9, please show how the elliptical orbit would fail rapidly. How does slightest deviation send the planet off orbit or into the star?

There are a number of gravity simulators available on the internet.
This one allows you to set the gravity exponent: http://particlesandbox.com/

This one is even easier to use, and lets you change the gravity exponent "on the fly", without restarting the orbits:
https://testtubegames.com/gravity.html

Play with it, it will help with an intuitive understanding.

6. What are the implications of singularity having finite mass over zero volume?

It means there are a number of awkward infinities.
In practice, we interpret it as saying that our models break down at this point.

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Physics, Astronomy & Cosmology / Re: Does time have more than one dimension?

« on: 19/11/2020 09:09:50 »

Although, as a curious non-scientist, whether time is a one dimensional aspect of Einsteins four dimensional universe, or if it can be two or more dimensions which opens the possibilities of larger variations, I have often wondered about what exactly is it that is moving from the past to the future. In other words, what is the sense of "now" that we each take for granted, that advances from one moment to the next to define our passage through time? It seems to be a mystery rarely questioned. When we read a book or watch a film our attention moves through the book or something mechanical processes each subsequent instant to carry us from one instant to the next. I wonder what engine moves us through that experience, and what are the energies that do this? One of the biggest mysteries to me is the nature of "now".

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Physics, Astronomy & Cosmology / Re: Does time have more than one dimension?

« on: 18/11/2020 20:06:46 »

All I know is that the mass of the black hole is preserved, so from the perspective of the outside, it doesn’t leave our universe.  The mass/energy is radiated back into normal space over finite time, and it would seem that could not be true if anything went to another universe.

In the hypothetical "black hole cosmology", a black hole in our universe forms a new, separated universe in the twisted spacetime inside, after matter hits the singularity.

With Hawking radiation, each black hole has a a large but finite lifetime in our universe. But how large it is in space and how long it lasts in time with the twisted spacetime inside the singularity is anyone's guess.

It's a hypothesis, and unprovable with our current theoretical & experimental techniques.
- Our current theories break down in a black hole
- And perhaps fortunately, we don't seem to have any nearby black holes on which to perform experiments!
See: https://en.wikipedia.org/wiki/Black_hole_cosmology

A universe is not a contained object, at least not by any meaningful definition of ‘universe’.

The same hypothesis points out that our early universe meets the criterion for the formation of a black hole, with us inside it.
- At least this part of the hypothesis has observational evidence supporting it
- It suggests that our universe might be a black hole inside some containing universe
- possibly a containing universe which itself contains many black holes; these would effectively form different universes, from our viewpoint...

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Physics, Astronomy & Cosmology / Re: Does time have more than one dimension?

« on: 18/11/2020 14:19:57 »

Please help me answer these questions:

1. Still can't understand a time plane. How would it eliminate causality? What is meant by circular paths on a time plane?

It means you can draw a loop on a plane, but not on a line.
More technically, for the types of partial differential equations involved in systems of multiple time dimensions, a set of initial data doesn’t determine a unique solution to the system. You can google ‘initial value problem’ for more info on this.

Do cause and effect even exist macroscopically?

Of course.  I step in front of a bus. That causes me to die. Sounds pretty macroscopic to me.

Isn't time just a macroscopic increase in entropy with very low probability of entropy dip happening? Would entropy prevent additional time dimensions?

Time isn’t entropy. The properties of entropy only make for a weak arrow of time, but our physics is time reversible at scales below thermodynamics, which is not always the case.


Evan gives some good answers for point 2.

Even in our regular 4D universe, after an incredibly long period of time, wouldn't the earth still end up falling into the barycenter/sun due to the sun's curving of 4D spacetime?

Earth is actually moving away due to 2 effects, and moving closer due to 2 other effects.  Currently the former effects far outweigh the latter, but yes, gravity wave radiation must win in the end.  That isn’t an example of the orbital instability of which I was talking. It is entirely stable all the way.

3. I didn't get the speed of light part. Please rephrase it and what it implies in the context of 2 time dimensions.

It has nothing to do with the number of dimensions. Spacetime is a bunch of dimensions, some of which are space and some of which are time.  So you can have a meter of time.  The constant c tells you how long a meter of time is (or a second of space), even if there are 12 time dimensions and 8 of space.

4. Please list the properties of tachyons and what they can do. I mean like can they actually travel back in time?

They go faster than light.  That means that one can select an inertial frame where the source of a tachyon event is ordered after the destination event of a tachyon.  That’s time travel in that frame, but not time travel in a different inertial frame that orders those two events differently.  Reference frames essentially are just an abstract ordering of events. There’s no actual preferred orientation of the physical time dimension, so it is at best an abstraction to say that tachyons travel back in time.  Since they don’t exist or at least don’t interact with normal matter, no message can be sent with them, and locality laws are preserved.  One must break locality laws to actually (not abstract) travel back in time.

What would their light cone be like and how would it allow traveling back in time?

They don’t seem to have a light cone at all since they don’t interact with anything. A thing that cannot be measured is the same as a thing that doesn’t exist.

I was assuming a hypothetical observer like a photon(by IIT, even it should have a bit of consciousness but that isn't what I want to discuss here at all so please forget it) which is 3+1 dimensional and how would it differ from spacepoint timecubed tachyons. Just think of a normal person and an advanced species living in more time dimensions. What things would be accessible to that species and what sorts of feats could it achieve? Could it travel back in time and maybe go across full spectrum of universal wavefunction?

I cannot answer how a species can form in a universe with one spatial dimension (the 1+3 one with the tachyons).  There is no ‘backwards in time’ any more than there is a forwards in it since time is a volume there, not a line with an arrow head.

The only way to escape from inside a black hole is to travel back into the past, how would tachyons do it?

I don’t think a tachyon can escape a black hole. That would be physical time travel, not just abstract time travel.

I don’t know the mathematics. I don’t know why tachyons result in such a scenario. Read up on it if it interests you.

Could access to more time dimensions allow all sorts of time travel in a 1 time dimensional universe?

If it is a 1t universe, there doesn’t seem to be more time dimensions to access. Maybe some of the 11+ dimensions of string theory are temporal.  Only 4 are macroscopic, and the others are there but very finite (closed) in scale, so they’re not noticed at the macroscopic level.  Access to that kind of time and space doesn’t really change anything macroscopically.

5. So is it safe to say singularity is a point in time just like the big bang being a point in time?

A singularity is a limit where mathematical laws and physical laws break down. Not all of them are points.  For instance, the event horizon of a black hole is a singularity in some coordinate systems, but not in others.  So only the latter coordinate systems can be used to model what it’s like to fall into one, but it cannot be used to model an observer hovering there because that introduces singularities again, just like trying to do the same thing here on Earth with a device capable of infinite acceleration.

I’m not sure if ‘point in time’ has meaning in a universe without absolute time. Space and time had not yet separated at the big bang, so it simply may not be entirely accurate to model it as a point in time. That’s the singularity talking again. You can’t use normal terms in a place where the rules break down.

Since 1 spatial dimension(the radial one) has become time dimension inside black hole, does that mean the radial dimension actually became infinite in length since time dimension is also infinite?

A clock falling into a black hole reaches the central singularity in a calculable finite time.  Time is not infinite there. It ends abruptly.

Would black hole singularity be infinitely 1D and maybe contain or connect to a 4D universe?

All I know is that the mass of the black hole is preserved, so from the perspecitve of the outside, it doesn’t leave our universe.  The mass/energy is radiated back into normal space over finite time, and it would seem that could not be true if anything went to another universe.

6. Can light never escape from inside a black hole and hence Bob can never send a message to his wife? But how can Bob receive the birth message if upon falling inside, he travels faster than light towards singularity?

He doesn’t fall faster than light.  ‘Down’ is a time dimension now. 
Here’s a Kruskal-Szekeres diagram of a black hole with all our players in it.

The dotted line is the wife in normal space ‘I’ at some fixed distance r from the event horizon.  Blue line is Bob. Region II is the black hole, and red line is the singularity.  Lowest magenta line is the news of ‘I’m pregnant’ which reaches him before he crosses. Not shown is the ‘it’s a girl’ message sent at about t1.8 that reaches him inside.  The t2 message is the last possible light that can reach him.
Last magenta line (from t3) is the news of the first steps, which never reaches Bob.
This comes from a thread debunking the idea that since time freezes at the event horizon, somebody falling in will witness the end of the universe. They don’t.

I didn't get the past light cone part, please rephrase it. Is it related to how I can only see the past due to speed limit?

You can only be causally effected by events in your past light cone. You mostly can only see events on (not in) your past light cone, which is why you cannot see the dinosaurs despite them being in your light cone.  I say mostly.  You can see the dinosaurs with a well placed mirror.

7. So a hypothetical 3 spatial dimension sphere having its own intrinsic time cannot exist/be contained inside a regular 4D universe?

It’s space and time would not be instrinsic. The thing is just an object countained by a universe. A universe is not a containned object, at least not by any meaningful definition of ‘universe’.  I tried to give an example of a simulation of such a thing, but the simulation is still just a contained object or process, not an actual universe. That’s why I think that while it is in principle possible for a universe to be simulated, it is not possible for the universe to be a simulation. The simulation reduces it to a contained thing, and thus not a universe.

8. Is time not intrinsic to a 4D block universe being at the surface of a 4+1D hypersphere that is expanding? So there is no 2nd time dimension to an expanding hypersphere?

The surface of a 4D hypersphere is 3D just like the surface of 3D Earth is 2D.  If radial dimension is intrinsic time, then it expands over time, and that makes it 4D again. I don’t see a 2nd time dimension described.

9. What would be the dimensionality of a being with all its events being simultaneous?

How would it qualify as a ‘being’ if it exists for but an instant?  How would the set of those events be simultaneous if they’re not at the same spatial location? A pair of separated events that are simultaneous in one frame are not simultaneous in another, so they’d have to be all the same event. One event is not a ‘being’.

6

Physics, Astronomy & Cosmology / Re: Does time have more than one dimension?

« on: 18/11/2020 08:22:16 »

2. What would be the properties of a 4D star? How is the orbit different in that case?...Would gravity work irrespective of dimensionality?

I think you are talking about the properties of 4 Dimensions of space, and its effects on gravity & orbits?

The inverse-square law of gravitation (and light) works in a universe with 3 dimensions of space.
- In a universe with 4 dimensions of space, I expect that gravitation (and light) would follow a different law - possibly an inverse cube law?

In our universe, the inverse square law of gravitation exactly balances the kinetic energy of an orbiting mass; the kinetic energy increases as the square of the velocity.
- This allows a smooth, repeatable exchange of energy between kinetic energy and gravitational potential energy
- Which is what you need for a stable elliptical orbit for a life-bearing planet

If you change the way gravity changes with distance:
- For example, instead of the familiar 1/r², you make it 1/r^2.1 or 1/r^1.9
- Then elliptical orbits fail rapidly

Of course, we have no experience with a hypothetical universe with 4 dimensions of space; it is possible that other relationships might change too?

Even in our regular 4D universe, after an incredibly long period of time, wouldn't the earth still end up falling into the barycenter/sun due to the sun's curving of 4D spacetime?

Not directly. In a 2-body Solar System with just Sun & Earth:
- Time dilation would cause slow precession of Earth's perihelion (like happens with Mercury), but it does not dissipate gravitational potential energy or angular momentum.
- Where these are lost is through gravitational radiation, which robs some of Earth's angular momentum, and radiates it away through space at the speed of light
- The amount of gravitational radiation for the Sun-Earth system is around 200 Watts
- So as you say, it would take a very long time.
- This is quite unlike a 1/r^2.1 or 1/r³ gravitational field, where elliptical orbits decay catastrophically.

Relationship with the Three-Body Problem
Ignoring gravitational radiation, in our universe:
- Two bodies in orbit have stable elliptical orbits around their barycenter
- Three bodies in orbit is complex, and there is no general solution (but there are some special cases - 5 of them discovered by Lagrange). In general, the smallest body ends up plunging into the star, or flung off into deep space.
- 9 or more planets is even more chaotic, as indicated by some of the large craters scattered across the Solar system (not to mention the Moon itself). At present, the Solar System is in a fairly stable phase; simulations suggest it should continue for hundreds of millions of years (barring outside influences).
- However, if gravity deviated measurably from 1/r², then even a 2-body system (eg Earth+Sun) would be unstable.

https://en.wikipedia.org/wiki/Three-body_problem

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Physics, Astronomy & Cosmology / Re: Does time have more than one dimension?

« on: 18/11/2020 05:38:38 »

I entered this topic out of my personal confusion with an Einstein block universe where one time dimension and three spatial dimensions configured a universe of absolute cause and effect and no possibility of inabilities to determine a fixed relationship between the past and the future

Einstein was not the first to posit a block universe, and was initially resistant to it.  It being a block had little to do with the sort of hard determinism that you seem to suggest here. Quantum mechanics interpretations seem to be the grounds on which determinism or the lack of it come into play.  The block universe, or a 3D one with flowing time are interpretations of time, and both support both deterministic and non-deterministic physics.

other cosmic investigations seem to conclude that multiple universes are generally too separate to have intimate inter-reactions on the mere mind sets of physics experiments.

If they interact, they're not really separate universes then, are they? Not the way I define the terms anyway.

This seems to leave the possibility of indeterminate outcomes of experiments the necessity of this universe to contain multiple timelines although each of us normally are only aware of our own time line of existence.

There are valid interpretations that have only one
very much determined outcome to any experiment. I personally don't favor them, but that's just a choice of mine. There is no known falsification of them. Yes, there are equally valid indeterminate interpretations as well.

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Physics, Astronomy & Cosmology / Re: Does time have more than one dimension?

« on: 17/11/2020 19:56:54 »

it seems to me that a film strip quite simply substitutes one element of space for time whether or not it is projected.

Yes, exactly.

Can you please elaborate in simple terms:

1. How more than one dimension of time would result in unpredictability?  Suppose a block universe had more than one dimension of time, what would it mean?

Instead of a timeline, you’d have something like a time plane. You can have circular paths on it, which eliminates what we think of as causality. Without causality, things are not meaningfully predictable since they’re not necessarily a function of a nearby state which is considered a ‘prior’ one.

How would more than 3 dimensions of space be unstable?

Things like planetary orbits and formation of atoms only works in 3D.  With more dimensions, the entire universe tends towards either a continuous solid or a haze of meaningless radiation, neither of which is likely to evolve an observer capable of gleaning the rules.
So say we have a planet orbiting in a perfect circle around a 4D star.  The slightest deviation from that perfect circle sends the planet into the star or off into the distance.  That’s not a stable orbit.

Would speed of light limit still be an issue?

Speed of light seems to be a relation between distance in time vs distance in space.  So a pair of events separated only by one nanosecond has the same interval between them as a pair of events separated by about a foot of space. That ratio is the speed of light, whether or not there is actual light in the physics being considered.

What is implied by tachyons having 1 dimension of space and 3 dimensions of time?

I don’t know the mathematics well enough to understand why tachyons are the only solution to such an arrangement. Tachyons are simply physical particles that can move no slower than lightspeed, and have greater (absolute) energy near light speed, just like normal matter.

How is its experience different from 3 spatial and 1 temporal being's experience like a photon?

Not sure what you mean.  A photon isn’t an experiencing temporal being, but a photon can be experienced by such a being.
It is unclear if an experiencing entity can be constructed from only such elementary particles.

 

What things are tachyons capable of doing?

Well, if our universe has any, they don’t seem to interact at all with matter that we can measure, so that sounds an awful lot like not doing anything. They seem not to exist in our universe any more than does real negative mass objects, despite the mathematics allowing them as valid solutions to the equations.

3. Inside a black hole, since radial and temporal dimensions change their roles, does this in any way affect dimensionality of 4D spacetime inside black hole?

No, it’s still 3+1 in there, which is why you can fall in and not know when you’ve crossed the event horizon.  The singularity is now not in some spatial direction, but rather in the future, so it is unclear how that effects tidal forces on you as you go forth. Gravity is not usually described as pulling you into the future, but we can’t really apply our normal concepts to the bent spacetime inside a black hole.

Can a 10 m^3 black hole's inside be bigger than 10 m^3?

It seems so.  What was the time dimension becomes space, and that goes potentially a long way in both directions, so you perhaps have finite space in 2 dimensions but much more in the 3rd, sort of like a long hose, but in 3D. Not sure. I’m not an expert there.

Is time completely different inside a black hole? Is black hole's interior, actually on a different timeline completely?

Not really different. As I said, it’s still 3+1 in there.  The events inside have no simultaneity with events outside using a typical coordinate system like that Earth uses, but other coordinate systems order the events across the event horizon just fine, and show things like certain events on the outside can be measured from somebody inside, but others cannot.  So Bob falls in, leaving his pregnant wife behind forever.  She gives birth and announces it’s a girl, and he gets that message, but he misses the message send showing her first steps since that event is outside the past light cone of any part of his worldline.
Bob of course can send no reply that his wife can hope to get, even after infinite time.

If a hypothetical 3 spatial dimension 10 m^3 sphere(of non-expanding fixed volume existing within a universe) had its own intrinsic time, then from the point of view of the whole universe, is it safe to say the system(sphere + universe) is 3 dimensions of space and 2 dimensions of time, or would that sphere would need to exist outside the universe(and cannot be part of the universe if it had its own time)?

It would be one object existing inside the other.  The spacetime of the internal object would be separate (not interact with) the external spacetime.  Being a contained object, yes, it occupies a swath of external spacetime, but whatever definition you’re giving that space internally has no interaction with external spacetime.
So for instance I can program a cellular automata simulation, and I can make it go as slow or fast as I want (its intrinsic time), or pause it for a month, and those make zero difference to the outcome of the structure.  Not running it at all doesn’t change the structure.  5+7 is still 12 whether or not somebody actually figures it out somewhere.

Because an expanding hypersphere results in 4 dimensions of space and 2 dimensions of time to give it time to expand hence hypersphere is actually 6D?

Sorry, but if it is expanding over time, thats 1 temporal dimension. Where’s the other one?  I counted 5D in all.

What is meant by "Spacetime is one 4D thing, not time that passes and space that doesn't (different things)"? How can we be 4D beings if we cannot know simultaneously all the events that happen at all times at once inside a block universe?

You are aware of all the events on your worldline. You do experience them all.
They’re not simultaneous, since that would make them all at the same time, which is just as silly as your arms and legs all being at the exact same point in space.  You’d not be a 4D thing if all your events were simultaneous.

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Physics, Astronomy & Cosmology / Re: Does time have more than one dimension?

« on: 16/11/2020 12:57:21 »

In dealing with dimensions on a perceptual basis rather than that of mathematical theoretics, one dimension is visually a line, two dimensions become a surface, and three dimensions are a volume. Time, the accepted fourth dimension, is difficult to envision, but by substituting time for one of the three perceptual space dimensions a partial comprehension can be managed.

Yes.  It being difficult to depict 4 dimensions on a 2-D page, some (all but one?) of the space dimensions can often be ignored in order to add time into the illustration.
What physicists mean by time being a 4th dimension is that time has the same ontological status as space and cannot be separated.  The universe is not a thing existing within time, but rather time is part of the universe.  Thus, if there is a lower bound to time (big bang say), then it is meaningless to ponder the state of things a day before the bang similar to it being meaningless to ponder the color of a rock a meter beyond the rock.

Any book describing a series of events has made time one of the dimensions in the length of the book. A movie film strip has flattened space into two dimensions and the third dimension becomes time in the succession of frames to create the illusion of movement.

Good examples, but the physics view is typically a book without a reader, or a film without a projector.  Without the reader or projector,  all the pages/frames have equal ontological status and no frame is the ‘current’ one.  The physics resulting from there being a current frame in the projector leads to certain interesting contradictions.

The attempts  of physicists to popularize Einstein's concepts of how gravity distorts the shape of three dimensional space to cause objects speeding in a gravity field to be captured into orbits around stars and planets is managed by visually  reducing the three dimensional volume of space to a kind of two dimensional trampoline type surface where a heavy object lies at the bottom of a pit created by its gravitational force and a speeding object slides into that pit and is forced into orbit in the distorted space.

The trampoline illustration is useful, but not perfect, and can only be taken so far.
If a speeding object comes from outside and into such a well, it will speed its way out again, not falling into orbit.  To do the latter it needs to lose energy.  Falling into orbit is as expensive (for a rocket say) as leaving it.  Apollo spacecraft expended more fuel going into orbit about the moon than they did leaving it.

What remains a mystery is the direction of the depth of that pit which I suspect is the fourth dimension of time.

The direction is easy.  An event is a point in 4D spacetime, so just define any two successive events.  Drop a ping pong ball on a table.  The first hit on the table is event 1, and the second hit (same spatial location on the table) after the bounce is event 2.  A line drawn through spacetime connecting those two events is oriented in the direction of time.

In the theoretical problems contained in dimensional multiplication, there is a consistent resistance to the possibility that there is more than one time dimension.

The possibility of universes with different numbers of time dimensions exists.  The physics of things would be different, and it seems difficult to have any complexities that would allow the emergence of an observer.
Tegmark put out this chart graphing the nature of various configurations of time and spatial dimentions:

This shows that say 2 time dimensions is quite plausible, but nothing interesting results.  The tachyon universe is somewhat interesting, but has only 1 dimension of space and 3 of time.

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Physics, Astronomy & Cosmology / Re: How does past, present, future exist at once? What is block universe?

« on: 01/11/2020 21:27:59 »

I don't know, nobody does. I still will try to define it. It's 'energy',  and 'energy' is a coin of exchange. the way it works is called 'entropy' From that we go to relativity in where the only thing we can define is your local model. If that agrees with mine and others, we have a 'fact'. The same goes for any 'repeatable' experiments you create.
=

It's about building a world image. In relativity all models are local, they build up to a 'global' model in where we state this will be valid for all times, and at all places. In quantum theory that's not enough. that's where 'many worlds' come in

Block universes comes in various shades. The thing joining them is the idea of 'time' not having a arrow. And free will may exist or not in such a universe. As long as we define the choices as being 'infinite' in it.

11

Physics, Astronomy & Cosmology / Re: How does past, present, future exist at once? What is block universe?

« on: 29/10/2020 13:05:41 »

2. Please explain eternalism and block universe in simple terms. Sorry I was always dumb and I am unable to understand this.

Simply that all events have equal ontological status. No slice of time is the preferred 'present', and lacking this preferred moment, the preferred moment cannot move, so time isn't something that flows. Thus any coherent discussion of a block view must avoid references to the present that doesn't exist, or else the statement will make no sense. You cannot mix the two views.

3. Is our 4D universe flat and exist on the surface of 5D hypersphere? Is the hypersphere expanding?

This does not seem to be the prevailing view, and is not the eternalist stance. An expanding hypersphere as you describe seems to add a 4th spatial dimension (to get 5D from 4D) and a second dimension of time (to give it time to expand).  A block universe cannot be 'doing' anything since time is intrinsic to it. The block universe is not an object existing in time, as that would be a second kind of time.

4. Is it really impossible to see the present of a distant planet?

Under block universe, there is no present, here or on the other planet. We need to reword the question.
So is it possible to see an event on the distant planet that is simultaneous with the viewing event here on Earth? No, the finite speed of light forbids that. We could send messages faster than light, which is impossible.

Could some abstract higher dimensional perspective(eg. God/programmer) see all of simultaneously existing time since 3D beings can only see time as being very subjective?

Under a block view, we're 4D beings, having length, width, height, and duration. Light does not 'exit' the universe, so if there is something external to the universe considering it, 'seeing' would be the wrong word to use since light (information of any kind) does not go from anywhere to this external point. Yes, the structure could be considered mathematically, and if it is hard-deterministic, all the states could be known if the initial condition was known.

12

Physics, Astronomy & Cosmology / Re: How does past, present, future exist at once? What is block universe?

« on: 29/10/2020 12:52:47 »

How can past, present and future exist all at once?

By a definition of 'all at once' that is different from 'all at the same time'.  The phrasing you use for that is considered correct, but the reference to past, present, and future belongs to a different interpretation. There is no past, present or future in a block interpretation. Past and future (and ambiguous) are just relations between pairs of events, none of which is 'the present'.

Many light years away, alien lifeforms would still be seeing dinosaurs on earth since only dinosaur earth light has had time to reach alien lifeforms so far, but how can earth's future be seen?

Again, there are no events that are 'the future', and confusing statements will always seem to arise whenever you phrase a question in terms that assume a presentist view, so best not to.  The year 2021 can be seen by humans that live then.  The dinosaurs cannot because there are no humans at the same time as them.

How is future also predetermined?

There is no 'the future'.
The state of any particular point in time is not necessarily determined by prior events. Much depends on the interpretation of QM used. I for one don't buy into determinism, but there are interpretations that do. If it is determined, then the future of any given event (say the next-year future of Earth, 1950) is completely determined by the laws of physics, which cannot involve true randomness, else it wouldn't be deterministic.

Determinism or not has nothing to do with the presentist/etermalist interpretations of time, since either interpretation of time can be paired with deterministic or non-deterministic physics.

Does it have to do with special relativity and light cones?

Not really. It (and the principle of locality) has to do with quantum mechanics.  SR (notably the principle of relativity) contribute to the suggestion of the block interpretation of time since for any given event, if that event is objectively 'the present', then multiple distant events can be simultaneous with the one event depending on the frame of reference of choice (see Andromeda paradox), and hence either none of those distant events is 'the present' (contradicting presentism), or only one of the frames of references is the correct one (contradicting the principle of relativity on which SR rests).  Hence SR suggests a block view.

13

Physics, Astronomy & Cosmology / Re: How does past, present, future exist at once? What is block universe?

« on: 29/10/2020 08:48:20 »

2. Please explain eternalism and block universe in simple terms. Sorry I was always dumb and I am unable to understand this.

Don't feel too bad about it - this is beyond what we currently know, and all we have to work with are hypotheses rather than evidence.

The Block Universe is a hypothesis coming from the direction of Einstein's relativity.
The Many-Worlds hypothesis comes at the same question from the direction of quantum theory and Schroedinger's equation.
Which one is true (or both, or neither) is currently unknown.

As I see it, the Block Universe at least provides a mental model for 4D spacetime.
- It is hard to imagine a 4-Dimensional object when all our experience is 3D
- But I have seen the Block Universe concept used to compress the hard-to-imagine 4D down to 3D which is easier to picture in more concrete terms.
- For example, it is hard to imagine the orbit of a planet in 4D spacetime= 3D space + 1D time.
- However, by taking a slice of space in the orbital plane of a planet = 2D space you compress 3D space down to 2D space
- By adding in time, you change to 3D spacetime = 2D space + 1D time
- So we can imagine the circular orbit of a planet in 3D space
- and we can then picture the same planet taking the path of a spiral along the time axis in 3D spacetime. 

See: https://en.wikipedia.org/wiki/Eternalism_(philosophy_of_time)

14

Physics, Astronomy & Cosmology / Re: How does past, present, future exist at once? What is block universe?

« on: 29/10/2020 08:45:59 »

Please help me answer these questions:

1. How can past, present and future exist all at once?

They can't, by definition of "all at once"

, but how can earth's future be seen?

It can't because the light that signifies it hasn't been emitted.

How is future also predetermined?

to the extent that classical mechanics and the completeness of your information allows - i.e not very far!

Does it have to do with special relativity and light cones?

no

2. Please explain eternalism and block universe in simple terms. Sorry I was always dumb and I am unable to understand this.

it seems to be about perception and interpretation of time and nothing much to do with the mechanics of the universe.

3. Is our 4D universe flat and exist on the surface of 5D hypersphere? Is the hypersphere expanding?

if that's how you want to model it, and your model is explanatory and accurately predictive, stick with it.

4. Is it really impossible to see the present of a distant planet?

obviously what you see is what happened when the light was emitted. 

Could some abstract higher dimensional perspective(eg. God/programmer) see all of simultaneously existing time since 3D beings can only see time as being very subjective? Are we even 3D?

Very confused thinking here. Time is what separates sequential events. If you can distinguish between before and after, you have a consistent timeline. An omnipotent being with fairly unlimited patience could unscramble an egg, but why would he have scrambled it in the first place?   

15

Physics, Astronomy & Cosmology / Re: How does past, present, future exist at once? What is block universe?

« on: 29/10/2020 08:12:13 »

To answer questions 1 and 2, you need to understand two basic principles.

The first principle is the principle of relative simultaneity due to the limited maximum speed of energy transfer, the speed of light in the vacuum. From the point of view of Einstein, this is the limit of causality. Therefore, two simultaneous events are relative to your place in space and time. Think of two different observers looking at lightnings and one sees two of them at the same time while the other sees them happening one after the other. As it is define as the speed of causality, it implies that there is no definite simultaneity.

The second principle is the conservation of information which can be related to the conservation of energy, though they are not necessarily equal. This principle just says that the information of the structure of the universe cannot be destroyed. It means that if you have the mathematical solution to the entire universe and a complete set of variables and parameters, you can predict the future and reconstruct the past (supposing you have the right computer).

According to Einstein, and this is probably true, if you could see the entire Universe from your own perspective and take a picture of it and you learn from it all information content of every particles and pieces of it, you could know everything, past and future. But it is true for any observer, even though their passage of time is different. As there is no preferred spatial coordinate or time, you cannot distinguish what is real and what is not apart from your own perspective. When you consider that all massive particles are observers and they have all their own perspective which must be equally real, then you have the Block Universe. Remember that you must exclude the possibility of an absolute time reference, an absolute simultaneity and faster than light causality. General Relativity does not respect the principle of the conservation of information due to the singularity at the center of black holes in his equations. Einstein knew his theory was not complete and no black holes were observed at the time. Most physicists think information is conserved and there is a limit and therefore no real singularity. Personally, I think Einstein went too far by eliminating these possibilities and the necessary limits are the keys to find the correct answer. The now has a special meaning in cosmology, this is where the symmetry of the expansion is conserved and energy is always conserved locally in General Relativity.

16

Physics, Astronomy & Cosmology / Re: What happens inside a black hole, and how do black holes evaporate?

« on: 27/09/2020 18:07:35 »

What happens to 'space' inside is that it conforms to gravity and 'shrinks'. And so do you and your meter stick, as defined from a outside far away. Not to you locally defined though. The same goes for the time component, as from a outside it 'slows down', and as the inside is a singularity the 'center' should be a place where a outside observer would say that your clock has stopped, as far as I see. And the same should then go for your 'size' as a guess. Aka, you 'disappeared'

Is that correct?

Space curvature causes gravity, which can be viewed as the elongation of space not the contraction. I understand Infinite space time curvature inside a blackhole, does not mean space shrinks to nothing.

No one knows what goes on inside a black hole, lots of speculations exist. To an outside observer the blackhole might appear to be small, but to someone inside, it might appear very very big. The blackhole itself likely rips apart molecules transforming them into photons creating a photon star inside the event horizon. 

17

Physics, Astronomy & Cosmology / Re: What happens inside a black hole, and how do black holes evaporate?

« on: 27/09/2020 15:05:18 »

More on the sci-fi parts of the topic:

5. If 1 earth mass negative mass could be made in the future, would that completely evaporate 1 earth mass black hole(lifetime 5.6e+50 years) in mere seconds?

’Evaporate’ is a poor choice of words, which implies a slow process. ‘Negate’ would be better.  Yes, putting the two together results in zero mass, and the black hole is gone.
Getting it there is a trick. F=GMm/r² so since m is negative, so is F.  The black hole will be repelled by the thing approaching it and it would result in a chase of sorts. Best to drop smaller bits in from all directions so the black hole has balanced forces acting on it and doesn’t particularly try to get away.

Not sure how you would handle a blob of material made of negative mass. Can’t exactly grab it with tongs.

Are there any leading research currently that hints at how to produce negative mass?

I think that would be big news, so no.

If somebody in the future could collect the negative side of materializing particle pair

Particle pair creation makes two zero mass virtual particles. Positive/negative energy must be imparted to them to make them non-virtual. I’m no expert at the quantum mechanics involved in this, so I can’t say how this works, or probably why it cannot be done. I mean, something falls into a black hole and reduces its mass, so it seems that it must survive as a real thing long enough to do that.

For me, if the observer A's all atoms can be rearranged into the exact configuration from surrounding environment, then that would be his identity.

If the atoms are from the surrounding environment (such as with swampman), how is that observer A’s atoms?
OK, so you don’t mean moving observer A’s atoms to a new place (which can be done by walking), but using different atoms.  OK, so you’ve built a clone, and you say ‘that would be his identity’ which is kind of a vague statement. Does that mean that if some atoms are arranged into a John369 up on Mars using surrounding Mars material, then you are now on Mars? How does the not-you still on Earth feel about that? Who is that person now? Is he driving a stolen car now?
This is what I mean by needing to define identity. There should be clearer answers to such questions if I am to comment coherently about an escape from a black hole.

So assuming a futuristic quantum teleportation device attached to observer A, if that observer A disassembled inside event horizon and reassembled outside into exact configuration as before(from surrounding molecules), he would have escaped from inside black hole with his identity intact. Would this work?

Quantum mechanics does not allow information transfer to the past. Teleportation of sufficient resolution is possible in priciple, but only forward in time at up to light speed, not to the past.  You’ve been talking about swampman and Boltzmann brains, both of which are chance things, not information transfer.  It would be by total accident that a copy of you is produced outside an event horizon that exactly matches some state in the future of you inside the event horizon. There is no way for the future person to be part of the cause of this accident.

18

Physics, Astronomy & Cosmology / Re: What happens inside a black hole, and how do black holes evaporate?

« on: 27/09/2020 14:26:10 »

if the observer A goes inside of the black hole, would he see that inside the event horizon, there are photons of light everywhere?

Depends if there is anything emitting them, but there probably are since infalling material glows plenty on the outside, and I see no reason for that not to continue on the inside.

Would they be blue shifted or red shifted under the influence of such high gravity?

Depends on the source of light.  If you look back at Earth, it will be red shifted. If you are in a clould of small lights falling in with you, the lights to the front and back will be red shifted and the ones to the sides blue shifted.

Would the black hole's inside not be black at all but brimming with past light photons?

As I said previously, you can’t tell when you cross the EH.  Things look pretty much the same inside as just outside.  It slowly changes sure.  The have a nice video of what it is like to fall in, but the video only uses light from outside the black hole, not any of it generated by material falling in with you, so there is an area depicted as black, and it grows as you continue to fall.

The grid lines are hard to ignore, but you don’t see those of course as you fall.
No, there are no stars in black holes, so the usual view of points of light here and there goes away. So while light can come from any direction, there probably isn’t a whole lot emitting light except for the general glow that you get from hot material spread all over the place, which in turn is a function of how much material our black hole is ingesting besides you at the moment.  The black hole at the center of our galaxy is a notorious light eater.

Would it be bright white light or outside visible spectrum?

Light from outside red shifts as you fall (the video doesn’t show that), but as what was visible light fades to red, stuff that was in the blue range becomes visible.  So it would appear different, distorted, and not the usual colors. I would not call it bright because light gets dimmer as you red shift it.

2. I am still unable to get the implications of all future light cone pointing towards singularity, please give a few more examples. Inside event horizon, can the observer A theoretically do millions of different actions like do reading, play chess, yoga etc. but would be bound to fall into singularity? Meaning, he can do other things except for falling into singularity?

Yes to all.  The singularity is not a spatial location inside, but a temporal one. It cannot be avoided any more than you can avoid getting to tomorrow. The singularity is an end to time, and thus it is not meaningful to ask what happens one second after hitting the singularity.

3. If singularities have infinite density, then why would overall density of black hole be finite, like 2e+30 kg/m^3?

The singularity has finite mass over zero volume.  The overall density of the black hole is finite mass over nonzero volume. Volume is typically computed as the volume of a sphere with radius the same as the Schwarzschild radius. Hence the difference in density calculations.

Since there are a lot of black holes and micro black holes in the universe, does that imply there are brief periods of infinite density and infinite gravity regions everywhere?

Each back hole has such a singularity, yes. No micro black holes has ever been confirmed. They are a theoretical possibility.

4. Can cuboidal and other shaped black holes be simulated(like fixing 8 vertices and all directions inside cuboid point towards a center that would be the singularity)?

Sure, you can assign 8 points in space to define a cube, but then you’d need to rearrange matter such that all future light cones of events on the surface of this cube point entirely inward and past light cones point entirely outward. There seems to be no possible arrangement of matter that can achieve this geometry.

What shapes can a rotating charged black holes be? Why are most of planets, stars, black holes spherical? How is it related to gravity?

Rotating black holes are somewhat oblate, just like any spinning planet. Sea level at the equator is about 40 km further from the center of Earth than at the poles, so Earth is not a sphere. It is related to gravity because matter is always pulled to the lower energy state (downhill), and a cube shape ball of liquid would not be able to support the weight of the 8 mountains.
Black hole event horizons are roughly sphereical not for the same reason a planet is. A sphere is defined by a fixed radius of constant gravitational potential from the black hole mass.  Any fixed radius from a point object is going to define a sphere, not a cube.

19

Physics, Astronomy & Cosmology / Re: What happens inside a black hole, and how do black holes evaporate?

« on: 26/09/2020 14:28:19 »

Concerning faster than light escape from a black hole:

6. Would quantum teleportation on a large scale work from inside a black hole? Hence observer A's all of particles disassembling inside event horizon and reassembling far outside on a fixed machine? Shouldn't the Boltzmann scenario work here even if very rarely?

You'd have to define identity first. If I build a swampman of you, is it you? Identity seems to have a pretty clear legal definition only because humans cannot yet do that sort of thing (other things can). If I put McCoy into a transporter, is it him that is beamed to the planet below, or just a fax of him?

I am unable to understand how tachyons could escape from black holes. What is meant by them traveling along space-like geodesics?

It means that multiple points along its worldline are separated in a space-like manner. The interval between them is negative.
So I have a meter stick (a classic space-like object). The tachyon worldline can be at both ends at once (in some inertial reference frame). No object moving at or below light speed can do that.
A tachyon cannot interact with normal matter (similar to dark matter), else locality would be violated. OK, there are quantum interpretations that deny the principle of locality, so I suppose those interpretations would allow interaction with tachyons.

What happens to blackbody radiation emitted by observer A? Do they also not make it away from the singularity since all future is towards singularity and getting away from singularity means getting into the past which is impossible?

A's entire future light cone ends at the singularity, and any light from him is no exception to that. While he is outside the EH, he can still send light back to B.

Is this what would prevent even teleportation and entanglement with particles outside event horizon?

Teleportation is communication, and not possible at > c.  Entanglement is not communication, and so pretty much irrelevant.

20

Physics, Astronomy & Cosmology / Re: What happens inside a black hole, and how do black holes evaporate?

« on: 26/09/2020 13:59:35 »

Is it possible to determine just how much amount of negative mass would be required to evaporate an earth mass black hole?

-6e24 kg should do it.

7. Would gravitational force/tidal acceleration from an earth mass black hole really be on the scales of quadrillions~quintillions m/s^2? Why is the entropy so high?

An arbitrarily high acceleration (as measured by something 'hovering') can be had near the event horizon of a black hole of any mass.  As for entropy, I have no idea what you mean.

Would magnetic field be high around a black hole, greater than magnetar?

A black hole has charge and angular momentum, the former of which has no reason to be large. So I'd think no. The magnetic field around black holes is almost entirely due to motion of its accretion disk(s).

What is meant by surface tides measured in m/s^2/m? If surface tide value is 1e+21 m/s^2/m, does that mean an object standing at 1 meter distance from surface of black hole would experience gravitational force of 1e+21 m/s^2?

It means a difference of 1e21 m/s² between the one altitude and the other as measured by a hovering thing, with both points somewhat away from the event horizon. The acceleration is arbitrarily high at the event horizon, and not so elsewhere, so the tidal force must also be infinite there.
As measured by something falling in, there is no gravitational force at all (per equivalence principle), but there still is a finite tidal force, which is dependent on the mass of the BH.

Time to singularity comes out to be 4e-11 seconds, is this really true? Observer A would be gone and encoded into black hole 2D surface in such a short amount of time? Is effective density being 2e+30 kg/m^3 really true? Does it break at singularity?

You're mixing reference frames here. I'll take your word for the 4e-11 figure, but that's proper time for the falling thing. There is no surface on which anything gets encoded in that frame. In external coordinate time, the event horizon is the singularity and a falling thing never reaches it in any amount of time.

8. Is it possible to calculate how much the black hole surface area would increase if an object with suppose 1 earth mass falls inside a black hole?

Sure. You can compute the Schwarzschild radius from mass1, and mass1+Earth, so you just take the difference of those two. Area from a radius is easy enough.

Would that mass simply be added into black hole's total mass? And hence an increase from 9.8 cm^2 to 39.5 cm^2 if a 1 earth mass object falls into 1 earth mass black hole resulting in 2 earth mass black hole?

There you go. Easy, no?

9. Could black holes come in different shapes? Why are all black holes alike(uncharged non-rotating variety only)? Please explain what prevents a cuboid shaped black hole.

A cubeoid doesn't have constant radius, or more to the point, constant potential. Yes, a rotating one isn't perfectly spherical, and its singularity isn't a point.

10. What are future and past light cones? What are the effects near event horizon and near singularity?

Look up what they are on wiki or something. It is really basic, and I've no idea of your level of understanding if you have to ask that. Future light cone of an event at the event horizon is entirely within the black hole, so the radial direction becomes the temporal dimension, whereas it was a spatial dimension (up/down) on the outside. Hence the singularity is in the future of A regardless of what he does. The past light cone reaches outside the black hole, so he can see a finite set of events in the universe in his past, just like we can here on Earth.

In the case of near singularity, does all future of observer A point towards singularity?

Anywhere inside the event horizon, yes.

Is this what is resulting in the observer A paradoxically sending signal into the past?

What past? Yes, he can send a signal in the direction that was 'the past' on the outside, since that dimension is no longer a temporal one to him. There is no paradox in this. He is not sending a signal to any events in the past light cone of any event on the outside of the event horizon, so there is no way to spin this as a paradox.

Can observer A only interact with the past near singularity which can never happen?

No observer can effect anything outside his future light cone, by definition. The singularity is in that cone, so it will happen, but events in his past cannot be effected by him. Maybe you mean ‘the past’ of something else. The question is unclear.

Just what are the implications of one spatial dimension becoming time-like and time becoming space-like? How would that change something?

It would not be noticed. There is still 3 space and one time. Like goes on like normal until the tides start getting stupid.

Does that mean observer A can only interact with 2D space now and all future light cone time pointing towards a single future, singularity? Did observer A became 2D and got encoded onto the surface?

Mixing frames again. Only in B's frame does A stay on this surface. He's contracted, but still very much 3D there.

So basically, observer A can still move his hands in 2 dimensions but is inevitably going to fall into singularity?

He doesn't notice the difference, remember?  The world is still 3D to him, and he moves just fine for a while.
In B's frame, time stops for infalling things, so there is no moving of A's hands at all.