[Jqan Sand (OP)]

Speck Ululations

I submit this topic fully accepting that I am in the position of a fruit fly fascinated by the mysteries of the nature of this universe equipped with the average educational background of the rather impoverished possibilities of any normal drosophila melanogaster. Groucho Marx, a hero amongst us arthropods, has uniquely summed up our fundamental  basket of consternations  with the profound observation "Time flies like an arrow but fruit flies like a banana".
We bugs, as with any specific life form. have been created to deal with the limited challenges and opportunities of our potentials for survival and proliferation equipped with a meagre tool kit of minor sensual spectrums, and thereby, can produce decidedly limited results on the nature of reality.  Nevertheless, since we are amongst the more reasonably successful major current species on this outstandingly insignificant most wonderful planet, it  is worth a try.
Probably, grasping totalities requires initial simplification of the persistent confusions of the apparent general  chaos we must face, which demands the fabrication of simple abstracts which must be the bricks for our attempted architecture of a conjectural universe, this is not an easy matter.
Newton is credited with indicating that his successes can be attributed to the fact that he stood on the shoulders of giants, but a fruit fly perched on the shoulder of the most admirable intellect, still retains the limitations of a fruit fly.
As any common god is well aware, the universe construction hobby must start with a dimension or two to fashion into something interesting and we flies are reasonably happy with the three space varieties which do quite well with bananas. Those of us who have run across Einstein are doubtlessly uneasy with his demand of the inclusion of time as a fourth dimension but his evident success with nuclear weaponry has forced us to admire his skills in advancing the possibilities of ridding the planet of the plague of humanity which threatens planetary life so we grudgingly are forced swallow his temporal speculations.
But now, those of us with internet connections who keep up with string and brane ideas have encountered requirements of a universe of around eleven dimensions which seems to require extensions of perceptions well beyond anything even the most adventurous fruit fly could manage. Those fruit flies that have attained astronaut status bring back tales of their residences in the space station where up and down have vanished but in and out and left and right still remain quite sturdy. Aside from the full eleven-dimensional set, the possibility of a fifth dimension does retain a fragment of possibility. The physicist Lisa Randall has speculated in this area, but no physical evidence has yet proved possible and since she is nowhere in fruit fly academics, there is no solidity yet in these proposals.
Quantum theory, which is now approaching utilities in technology, is the most disturbing area in current physics and that it seems to involve interactions that deny some of the limitations accepted with distances in a four dimensional space-time universe, it remains a major puzzle.
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. 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. When we fruit flies, who have a very fast visual perception, see a projected film, we do not see movement but merely a succession of projected still pictures. 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. What remains a mystery is the direction of the depth of that pit which I suspect is the fourth dimension of time. The limitations of the observer's mind cannot visualize a bent volume although it has no difficulty with a bent surface.
In the theoretical problems contained in dimensional multiplication, there is a consistent resistance to the possibility that there is more than one time dimension. I cannot command any real depths in theoretical physics but if it is possible to find a basis for multiple time dimensions, that may open  possibilities of, not parallel universes, but parallel time pathways within this universe. If time has, at least, two dimensions, time becomes, not an absolute line between the past and the future as in Einstein's four dimensional continuum, but a surface with all sorts of alternate pathways and interconnections. This is a very common idea in many science fiction stories and films but has always been treated as a fantasy. Of course, three time dimensions would permit time to have volume and, by that, voluminous possibilities for variations. Since I have problems in easy conceptualization of all visual aspects of a simple tesseract, the complexities of multiple time dimensions, not to speak of spatial  novelties goes well beyond my visual and temporal imagination.
Nevertheless, some of the oddest items on the internet, such as that describing a visitor to Tokyo from a country that does not exist and a couple of similar totally weird experiences have lodged in my mind inextricably. Of course, the internet is bursting with a plethora of phony UFO photos and other peculiar mendacities, but I have had a personal experience in the same area that refuses to be put aside.
Although I was born and grew up in New York City, I became deeply impressed  with the people and culture of Finland and have lived in Helsinki for the better part of my life. Close by, where I now live, is a wonderful semi-wild huge park called Keskuspuisto (Central Park) with various pathways from the street directly into the park. Two parallel park pathways about a  hundred meters apart go directly into the depths of the park and I am familiar with both of them. Facing the park, a few months ago, I took the path on the right and it looked quite different from my previous experience. The undergrowth on either side of the path was far more dense that normal and when I reached a brook further along I noticed that a tree had fallen into the brook that I had not seen before and next to the path a trash collection can was affixed, not to its own post, but to a nearby tree. A path to the entrance path on the left that normally ran parallel to the brook did not exist.
These differences disturbed me so I retraced my steps on the right path to the entrance of the park and took the left path into the depths of the park to see if things had changed there. There seemed to be no noticeable change there and when I reached the brook which intercepted both paths the path between the entrance paths clearly had the parallel path that I had missed on my previous traverse of the right path.  I took the brook path to the right path which had appeared changed and all the changes had vanished. There was no fallen tree in the brook and the trash can was mounted on its own post as usual and not on a tree, as I had seen about ten minutes before. My subsequent supposition that I had momentarily been on a parallel time line and then returned seems most extraordinary even to me who had experienced it, but I am at a loss otherwise for a more acceptable explanation. I have explored those two paths many times since with nothing out of the ordinary occurring. I am at a total loss for a more reasonable explanation.     
 


 




 

 

[evan_au]

There are suggestions that spacetime gets rather twisted inside the event horizon of a black hole, with space dimensions becoming more time-like (and vice-versa).
- There have been some speculation about the possibility of more than one time dimension.
- But since there have been no recent reports of black holes crashing into Finland, I don't think that could explain your disorientation.

PS: Keskuspuisto looks impressive. I'm sorry I missed it when I was in Helsinki last year...

[Jqan Sand (OP)]

I appreciate your indication of black hole possibility. I have read that black holes come in various sizes and evaporate eventually so they can be somewhat evasive and perhaps, due to their extreme mass, vanish very quickly towards the planet's core where they gnaw on whatever is down there.

[Halc]

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.

[Jqan Sand (OP)]

I appreciate your attempts to clarify the mysteries but since I am something of an old idiot a good deal of it remains puzzling. it seems to me that a film strip quite simply substitutes one element of space for time whether or not it is projected.

[John369]

@Halc, I am very sorry for getting in between, can you please elaborate in simple terms:

1. How more than one dimension of time would result in unpredictability? How would more than 3 dimensions of space be unstable? Suppose a block universe had more than one dimension of time, what would it mean? How would that change anything? Would speed of light limit still be an issue? How would an extra spatial dimension change anything?
2. What is implied by tachyons having 1 dimension of space and 3 dimensions of time? How is its experience different from 3 spatial and 1 temporal being's experience like a photon? What things are tachyons capable of doing?
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? Can a 10 m^3 black hole's inside be bigger than 10 m^3? Is time completely different inside a black hole? Is black hole's interior, actually on a different timeline completely? 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)? 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 for this non-sense, I have bad educational background and was always bad, I want to know more and get a clearer picture) 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?

[Halc]

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.

[Jqan Sand (OP)]

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, I do not claim any innovative concept in this since there is a long history of imaginative writing where parallel universes permit all sorts of variations on a single time line where one individual may split into two or more possibilities to permit variations of experiences, I am not a scientist and have an inherent personal problem with the wonders of mathematics which totally dominates theoretical physics in exploring the mysteries of understanding the nature of our cosmos. The old story by Edwin Abbott titled "Flatland" introduced me many years ago to my limitations of conceiving a universe of more or less dimensions than the one we presume we live in and the current unverified theories of string and brane architecture which demands something in the area of eleven dimensions in this universe seem to indicate much is yet to be understood.  Although a multiple universe cosmos is proposed in the double split experiments where wave or particle patterns indicate most peculiar indeterminacy, 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. 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. The very odd idea might be that if we individuals are conscious of only a select four dimensional aspect of a hugely more complex universe, we may be each multidimensional beings, not with duplicates on other time lines, but one very large being who is conscious of only a four dimensional  cross section of itself and unaware of its multiple dimensional totality, Such a huge being  may cease to exist in this limited time line but the totality of each multi-dimensional being would hardly notice the minor loss. It's a very peculiar idea.       

[Jqan Sand (OP)]

Sorry, I am getting rather old and make silly mistakes.  I referred to "double split experiments" which should be "double slit experiments".

[Halc]

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.

[Jqan Sand (OP)]

I have read speculations that separate universes might have collided with ours  leaving some sort of evidence of the interaction, but none of this has, so far, been observed.

[John369]

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? Do cause and effect even exist macroscopically? Isn't time just a macroscopic increase in entropy with very low probability of entropy dip happening? Would entropy prevent additional time dimensions?

2. What would be the properties of a 4D star? How is the orbit different in that case? 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? Is gravity inseparable from spacetime? Would gravity work irrespective of dimensionality? Would a 4 spatial dimension star still curve a hypothetical 5D spacetime and allow a 4D planet to orbit it?

3. I didn't get the speed of light part. Please rephrase it and what it implies in the context of 2 time dimensions. (Sometimes I think maybe I should have come one or two centuries later which would have been much more interesting because of availability of more information, sorry for asking so many weird things and unknowns, just tell me everything you know, it would be new to me, don't hold back, repetitions are necessary for memorizing too)

4. Please list the properties of tachyons and what they can do. I mean like can they actually travel back in time? What would their light cone be like and how would it allow traveling back in time? 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? Could access to more time dimensions allow all sorts of time travel in a 1 time dimensional universe?

5. So is it safe to say singularity is a point in time just like the big bang being a point in time? Could anything that fell into black hole singularity actually come out scrambled into a de Sitter space/different universe via big bang? 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? Would black hole singularity be infinitely 1D and maybe contain or connect to a 4D 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? 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? The only way to escape from inside a black hole is to travel back into the past, how would tachyons do it and what are its implications and paradoxes like it shouldn't have fallen inside the black hole to begin with?

7. So a hypothetical 3 spatial dimension sphere having its own intrinsic time cannot exist/be contained inside a regular 4D universe? Since its spacetime is intrinsic to it, it would tend to add 3 more spatial dimensions and 1 more time dimension to the overall 4D universe if it were a part of it? Hence it is necessary for it to exist outside it? If it were to exist inside, would it need to have no spatial or temporal dimensions at all? Would it need to be a 0 dimensional singularity if it were to exist inside 4D universe? What is the 0th dimension anyway? Can 0 dimension actually contain within it all the dimensionalities or is it true nothingness? By the way, is our universe even 4D to begin with? 

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?

9. What would be the dimensionality of a being with all its events being simultaneous? Could more time dimensions allow perceiving all of 1D time in its entirety from the point of view of all observers within the block? Could all their worldlines be perceived at once by a single entity with access to more time dimensions and what about more spatial ones?

[evan_au]

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

[Halc]

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’.

[evan_au]

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...

[John369]

Please help me answer these questions:

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? https://www.forbes.com/sites/fernandezelizabeth/2020/10/12/now-time-travel-can-be-paradox-free-thanks-to-math/ [nofollow] Can you explain closed time-like curves in simple terms? Why can't they exist in our universe? If they did exist in some other universe, how would they allow time travel? 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?

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

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? Would traveling faster than light towards the opposite direction something fell inside a black hole allow it to escape since it can now travel back in time?

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?). But what does that even mean? Any matter falling in from the mother universe will disappear from that universe and emerge at the initial t=0 point of the daughter universe thoroughly scrambled, but 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? Or has the mother black hole been evaporated? But such big black hole life times were supposed to be over 1e+60 years, while big bang didn't seem to last that long. How long did big bang last? How and where is big bang happening today?

5. So in our current age, we just don't know what the exact inverse relationship of gravity would be in other spacetime dimensionalities? By the way, 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?

6. Is there something like a 0 dimension? What are the implications of singularity having finite mass over zero volume?

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

8. How would hypersphere be 5D if our 4D universe has time in its interior which is also the interior of hypersphere as per balloon analogy? Then our 4D universe itself is the 4D hypersphere and there would be no need for it to be at the surface of anything. Why is the need for an abstract higher dimension like hypersphere arising?

9. Is this analogy correct: We lived in the chromosomes & the chromosomes are parts of us. But they probably aren't aware of us, neither are all the cells that make us up. 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. (Totally sci-fi but many were inspired by sci-fi and got into science, besides it helps one discover just how many things are unknown and unanswered)

[Jqan Sand (OP)]

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".

[evan_au]

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.

[Halc]

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.

[Jqan Sand (OP)]

To say that we have this sense of moving from the past to the future because we need it, unfortunately in no way contributes to an explanation if what it is. In a block universe something is moving and I have no idea what that might be. When a film is watched or a book read, attention changes with the point of view of the observer, The observer is somehow separate from the book or the film. But we inhabitants are inside the universe, not outside observers. The letters within a book do not move. The frames within a film strip are firmly fixed within the strip although the strip is projected in sequence to something outside the strip. The sense of now seems, somehow, outside the static block universe. I have no idea what that might be.