Spyman

Lunar variation is how the pull of gravity from the Moon changes when the Moon orbits the Earth and therefor affects us down here differently depending on where it is in its orbit. If the Moon is above you its gravity will pull slightly up on you and counter Earths gravity a tiny bit, but if the Moon is on the other side of Earth than you are then its gravity will pull slightly down on you adding to Earths gravity a tiny bit. One example of this is the tides of sea level caused by a combination of the gravity from the Sun when Earth spins and the gravity from the Moon when it orbits. ---------- An astrounaut standing on the Moons surface looking down at Earth will not fall down to Earth and someone walking here on Earth under the Moon will not fall up to the Moon either. At the surface of the Moon the gravity from Earth is small due to the far distance and the gravity from the Moon is strong since the astronaut is close to it, and it's likewise but opposite for us standing here down on Earth and looking up at the Moon. But gravity gets weaker with distance so there must be a point somewhere inbetween Earth and the Moon where their gravity will negate each other exactly and at that point both the gravity from the Earth and the Moon is equal strong but pulling in opposite directions. This point is one of the Lagrangian points. If the spaceship is parked at the Lagrangian point between the Earth and the Moon then it could float there without being in orbit or burning fuel in its engines to counter gravity. But if the Spaceship gets closer to Earth it will fall to Earth and if it gets closer to Moon it will fall down on the Moon. And since the Earth is bigger and has more mass its gravity is stronger than the Moons so the point where their gravity is equal is closer to the Moon. Yes, that is one of five Lagrangian points.

I thought I did explain my opinion in post #9, but shortly I would summarise my alternative 8 like this: If Aliens have been visiting Earth then they most likely are: "Highly advanced travelers who by a rare chance stumbled upon Earth and took the opportunity to study the unique ecology here".

IMHO, if Aliens have been visiting Earth it is to study the unique ecology here without disturbing it. The Aliens must be highly advanced since they are able to avoid detection and might be so advanced that they could be considered supernatural. With lesser advanced Aliens in an encounter they would either make contact because it could benefit them or not take any chances at all by visiting Earth because we would be able to observe them and might be able to rival their knowledge level in warfare or at least cause them inconvenience enough to avoid us. We have not been around long enough as a advanced civilisation for the possibility that distant Aliens can discover us, as such they don't just "occasionally" stop by, they are either from our neighbourhood of stars or have by lucky chance stumbled upon us. If an Alien race discover us and Earth it is likely a very very rare event, and if they have the means to visit Earth and study I would think that they would be willing to spend an adequate amount of resources to do so, to increase their knowledge. The problem with an earlier and now much more technologically advanced civilisation hiding somewhere in our solar system is that there was a time when it was less advanced and therefor should have left some artifacts on Earth before they moved out, and there are no remnants at all. Why would they first leave Earth but then not continue further and if they stayed why bother to hide from us? Number 4 seems very unlikely. I don't belive it's possible to travel backwards in time and interfere with our past so number 6 is an impossibility for me. The Aliens in alternative 1, 2, 3, and 4 could all be advanced enough to be supernatural and since there is no clear distinction between them and alternative 7, number 7 seems irrelevant. If Earth have been visited then it is not because aliens want asteroids, if they come here they have a reason and the few remnants of asteroids down on Earth is not likely why they came. If they came for the asteroids in our solar system and then discovered us, it is by pure luck and so they could as well have been here for any other reason. Number 1 doesn't cover the nessesary possibilities and focus to much on the asteroids which is unimportant in my opinion. If the early humans in no 3 have evolved so much that they no longer are humans then they might as well be considered as pre-human as in no 4 and otherwise they could as well be like no 5 but hiding elsewhere than on Earth, scratch alternative 3. If they are humans that only have better technology, then I would not call them Aliens, there goes alternative 5. The only option left is alternative 2 which comes very close to my opinion, but it is phrased as if there are several different races of Aliens that visit us when they happen to be passing through our part of the Universe during their journeys. I hardly belive that our solar system is some cind of crossroad for intergalactic travel or that the total amount of Alien races in Milky Way are so huge that there are enough of them to regulary pass through here randomly. Thus I vote for alternative 8 - "Some other option".

Gravity weakens with distance but expansion of space increases with distance, clearly it is obvious that on small scales the gravity will win and clump matter together and on large scales expansion wins and disperses the clumps of matter. The force of Dark energy is thought to act on objects inside our galaxy and even on a nuclear level inside objects too, but the affect is vanishing small when compared to the other forces on that scale. I don't know if I understand your question, according to the theory of relativity, space is highly dynamic and fully capable of both contracting and expanding at an abundance of varied levels in different areas at the same time. These levels are also relative the observers frame of reference. Seems to be a confusion here, entropy needs energy to decrease and will increase for a system not in equilibrium. "The second law of thermodynamics is an expression of the universal principle of entropy, stating that the entropy of an isolated system which is not in equilibrium will tend to increase over time." http://en.wikipedia.org/wiki/Entropy "Since a finite universe is an isolated system then, by the Second Law of Thermodynamics, its total entropy is constantly increasing." http://en.wikipedia.org/wiki/Entropy IMHO I don't think there are any extraction of entropy energy from areas where gravity rules, which then somehows flows towards areas where space is expanding, where it then are expelled to fuel the expansion itself. Any net gain or loss of energy due to changes in entropy are taken care of locally.

If you connect two different springs on one object and then pull apart the strings in different directions you will end up with the object inbetween them in equilibrium and the net sum of forces acting on the object is zero. But that doesn't mean that the strenght of the springs are lesser at the object, they are still acting on the object. The influence of Earths gravity on a spaceship going towards the Moon is negated by the gravity from the Moon and if the spaceship passes the Moon then their gravity are effecting the spaceship added together. But the individual forces of gravity from each body acting on the ship is not changed even if the sum of their forces are.

Imagine that you are holding a rubber band stretched between your hands and balancing a wheel on it. Lets say that the radius of the wheel is such that it takes ten turns for it to travel from one hand to the other. Now if you streach the band to twice its length it would take twenty turns for the wheel to traverse from one hand to the other. Here is the kicker, what happens if you streach the rubber band while the wheel is traversing? Answer: You will end up with three different distances, one for the distance between hands when the wheel starts its journey, second is the distance between your hands when the wheel finishes its trip and thirdly the distance the wheel has traversed on the rubber band, measured in number of turns. ---------- Space is expanding like the rubber band and the speed of expansion is not limited to the speed of light, in fact it is often greater and during the initial phase of the Big Bang it was huge. When it's mentioned that a galaxy is 10 billion lightyears distant, it is the age of the light they are talking about which also is the distance the light has traveled from that galaxy to us, like the wheel. But the galaxy was closer to us when the light we see was emitted and is farther away right now when we are recieving the light. When space expands lightrays traveling through it gets streached too, and that gives them a redshift which astronomers can measure and use to calculate their distance and "displacement" due to expansion relative us. ---------- Here is a good Cosmos calculator you should test: http://www.uni.edu/morgans/ajjar/Cosmology/cosmos.html You need to input these values: Omega=0.27, Lambda=0.73, Hubble=71 and Redshift=1.815 for a galaxy with 10 billion lightyears old light, but you can play around with the redshift and check out different ages for the lightray. If you change the Hubble value you will be able to check different ages of the Universe.

The Big Bang was not an explosion of a massive clump of matter in surrounding space, it was more like every distance between every part in the clump started to grow very fast. Space is expanding equally in all directions. If Big Bang was like an explosion then we could observe the trajectories of other galaxies in the Universe and pinpoint where the center of the explosion should have been, but current observations reveal that everything far away enough to be affected by the expansion are moving away from us equally, in all directions, as if we where in the center of the Universe. Conclusion is that there was no explosion and that space are expanding everywhere and not from a center. The expansion is speeding up with an accelerating rate. In the initial conditions of the Big Bang, the Universe had an extremely rapid exponential expansion during the Inflationary epoch and then it slowed down as if gravity had the upper hand but the speed of expansion has started to accelerate again, which has led to theories of Dark Energy. "Misconceptions about the big bang The key to avoiding the misunderstandings is not to take the term “big bang” too literally. The big bang was not a bomb that went off in the center of the universe and hurled matter outward into a preexisting void. Rather it was an explosion of space itself that happened everywhere, similar to the way the expansion of the surface of a balloon happens everywhere on the surface." http://www.mso.anu.edu.au/~charley/papers/LineweaverDavisSciAm.pdf "The Big Bang The Big Bang is the cosmological model of the initial conditions and subsequent development of the Universe that is supported by the most comprehensive and accurate explanations from current scientific evidence and observation. The Big Bang is not an explosion of matter moving outward to fill an empty universe. Instead, space itself expands with time everywhere and increases the physical distance between two comoving points. Because the FLRW metric assumes a uniform distribution of mass and energy, it applies to our Universe only on large scales—local concentrations of matter such as our galaxy are gravitationally bound and as such do not experience the large-scale expansion of space. Independent lines of evidence from Type Ia supernovae and the CMB imply the Universe today is dominated by a mysterious form of energy known as dark energy, which apparently permeates all of space. The observations suggest 72% of the total energy density of today's Universe is in this form. When the Universe was very young, it was likely infused with dark energy, but with less space and everything closer together, gravity had the upper hand, and it was slowly braking the expansion. But eventually, after numerous billion years of expansion, the growing abundance of dark energy caused the expansion of the Universe to slowly begin to accelerate." http://en.wikipedia.org/wiki/Big_Bang "Dark energy In physical cosmology, astronomy and celestial mechanics, dark energy is a hypothetical form of energy that permeates all of space and tends to increase the rate of expansion of the universe. Dark energy is the most popular way to explain recent observations and experiments that the universe appears to be expanding at an accelerating rate." http://en.wikipedia.org/wiki/Dark_energy "The Big Crunch The Hubble Constant measures the current state of expansion in the universe, and the strength of the gravitational force depends on the density and pressure of the matter and in the universe, or in other words, the critical density of the universe. If the density of the universe is greater than the critical density, then the strength of the gravitational force will stop the universe from expanding and the universe will collapse back on itself. Conversely, if the density of the universe is less than the critical density, the universe will continue to expand and the gravitational pull will not be enough to stop the universe from expanding. This scenario would result in the 'Big Freeze', where the universe cools as it expands and reaches a state of entropy. Some theorize that the universe could collapse to the state where it began and then initiate another Big Bang, so in this way the universe would last forever, but would pass through phases of expansion (Big Bang) and contraction (Big Crunch). Recent experimental evidence (namely the observation of distant supernova as standard candles, and the well-resolved mapping of the cosmic microwave background) have led to speculation that the expansion of the universe is not being slowed down by gravity but rather accelerating. However, since the nature of the dark energy that drives the acceleration is unknown, it is still possible that it might eventually reverse sign and cause a collapse." http://en.wikipedia.org/wiki/Big_Crunch "Theories about the end of universe The fate of the universe is determined by the density of the universe. The preponderance of evidence to date, based on measurements of the rate of expansion and the mass density, favors a universe that will continue to expand indefinitely, resulting in the "big freeze" scenario below. However new understandings of the nature of dark matter also suggest its interactions with mass and gravity demonstrate the possibility of an oscillating universe." http://en.wikipedia.org/wiki/Ultimate_fate_of_the_universe

And the higher gravitational potential, the more quick clocks run. That is not counter-intuitive, that is the same thing that gib65 proposed. Hmm, the text I quoted from the Wiki article is phrased somewhat confusing... This is what I quoted: "Gravitational time dilation is the effect of time passing at different rates in regions of different gravitational potential; the lower the gravitational potential (closer to the center of a massive object), the more slowly clocks run." http://en.wikipedia.org/wiki/Gravitational_time_dilation What they mean to say is that for an object deeper down in a gravity well, where the intensity of the gravity field is greater, the clock will run slower relative for an object at higher altitude, where the intensity is lesser. Further down this is written: "Clocks which are far from massive bodies (or at higher gravitational potentials) run faster, and clocks close to massive bodies (or at lower gravitational potentials) run slower." http://en.wikipedia.org/wiki/Gravitational_time_dilation The wording with "gravitational potentials" is tricky because it is defined to be zero in empty flat space and then grow greater negative closer to and deeper inside massive bodies. "By convention, the gravitational potential is defined as zero infinitely far away from any mass. As a result it is negative elsewhere." http://en.wikipedia.org/wiki/Gravitational_potential Thus "lower gravitational potential" is not where gravity itself is lower or weaker, instead it's where the potential gets MORE negative which is a larger negative value farther from zero, overturned it turns out to be where the gravitational potential is greater. Reversely "higher gravitational potential" is where the gravitational potential is lesser or closer to zero. So it is actually the opposite of what gib65 is saying.

1. The connection between space and time is the speed of light, which is constant for all observers, this gives us the relation that when space is compressed then time is equally slowed down. 2. Gravity itself progress with the speed of light and is not able to exert force through time like you think. Forces can be caused in the past and might act upon us in the future, but right now here in the present there are only present forces acting on present space and time. If the Sun would suddenly vanish it wold take ~8 minutes before the last photon in the stream of light already released from it would reach us and we would be in the dark, similar it would also take the same time before Earth would be free from the last of the gravitational grip and instead of orbiting would take off in a straight path. But we are not able to measure a force of gravity from the Sun where it was 1 hour ago or from where it will be in 1 hour from now and if there are no forces emerging through time from no longer present Suns or from possible future Suns acting on us, then there are not any such forces acting on the Sun itself either. A past object is not pulling or being pulled by its present self and neither is the future self of the same object. Otherwise, if gravity would work across time, it would be possible to build a device that uses gravity as an agency for transfer of information to communicate with both the past and the future.

According to the Theory of Relativity, time will pass slower for a more massive body relative a less massive one. "Gravitational time dilation is the effect of time passing at different rates in regions of different gravitational potential; the lower the gravitational potential (closer to the center of a massive object), the more slowly clocks run. Albert Einstein originally predicted this effect in his theory of relativity and it has since been confirmed by tests of general relativity." http://en.wikipedia.org/wiki/Gravitational_time_dilation

If the difference in advancement is huge they are not likely to come here to pick a fight with us humans. But since their technology to build wormholes is dependent of average stars and they so happens to be building a highway through Milky Way with our Sun in their blueprints as one of many "Cobblestones" in their pavement, we might find ourselves unluckily standing in their way. What could happen to Earth when they build devices of that magnitude, to both harness the Suns output and their wormhole, in our neighborhood? Do we take care to not destroy anthills when we want to build something, do we even notice them when our bulldozers clear the area where a road is going to be built? They don't have to be hostile or aggressive, we could merely not be significant enough for them to notice or care.

"In physical cosmology, astronomy and celestial mechanics, dark energy is a hypothetical form of energy that permeates all of space and tends to increase the rate of expansion of the universe. Dark energy is the most popular way to explain recent observations and experiments that the universe appears to be expanding at an accelerating rate." http://en.wikipedia.org/wiki/Dark_energy

Frankly, I don't see any point in continuing the discussion with you, our communication has failed and I am not interested in playing silly word games. The slices are different and they are separated in time, I am certainly not proposing or asking if time is a physical tangible thing streached between slices and holding them together. I was not asking about causality, or how physics are trying to model the differences from one slice to the other. You are not able to understand my argument nr.3 in post #182 and I seem to lack the ability to explain it properly. We are probably better off accepting that we have different views of the world. Yes, and you were correct - the thread has derailed into a fruitless discussion.

How is the opposite faces of a 3D cube connected in only a 3D coordinate system? The communication and the discussion clearly fails on several levels...

I think you missunderstod the question or at least you failed to explain it. I would at best describe your answer as "bad wording" and at worst as contradicting your earlier arguments. This is how Iggy answered: This are good and straight forward answers, there is no information or objects moving between the slices of time, in this view of a static 4D universe and that is how I did interpret both your arguments about the dimensions. I don't understand the trouble here, your claim is: "You have a 4D object. To change it, you need a fifth dimension in which it can change." and without your fifth dimension there is no movement and that also means that there is no flow of whatever. Either you have movement through time or you don't have movement through time and I think you are the one arguing that there is no movement through time. In your static 4D universe there would not be any movements, so information would NOT be moving. Information would be embedded in the world lines, but there would not be any more "flow" of information between the slices of time than there would be a "flow" of matter moving towards the future. The world lines themselves would also be "sliced" in the time dimesion. Maybe I misinterpret the English language here, but my dictionary says that "flow" is "To move or run smoothly with unbroken continuity, as in the manner characteristic of a fluid." and with that meaning of the word "flow" there is nothing, not matter, not energy and not information either, moving or progressing through time from one slice to another in the 4D world you and Iggy are proposing. Without information describing the shape of a system moving from the past to the future, I don't think you can explain causality that way. But I did not ask about causality so it's somewhat irrelevant to the discussion at hand, unless you are trying to build up an argument I don't understand yet. I don't understand what or why you are arguing here, but I agree that it doesn't matter in which dimension you slice up a static 4D universe, there can not be any connections between the slices anyhow. Without something connecting the slices they are indeed disconnected. No, in a static 4D universe there is no flowing as I understand the meaning of the word "flow". Information are restricted to the same rules as matter and/or energy. No, without something connecting them they are totally separated, they are ordered in a certain way and lies next to each other but there is no connection between them. What do you think the "connection" between the slices consists of?

I am NOT arguing this. Yes, I fully agree. Sure, you can have two 4D objects intersecting somewhere inside a 4D block of spacetime, but there is no flow of information from the past to the present in this view. You don't seem to understand my argument at all, here let me repeat what you said again: "In order for things to move through spacetime you must add another dimension of time." Now I ask once more, how can information move from one slice of spacetime to another slice of spacetime without another dimension of time?

Ok, but it is you and Sisyphus who are the ones arguing that we can not have any movements, changes or progress in a 4D spatial universe without introducing a fifth dimension for the action to take place within. Look here what you have said: Read my post again and then explain in which dimension or how this information from event T1 is moving to T2 if all four dimensions are already "locked" by representing locations. If you are arguing that information can move from T1 to T2 in a 4D spatial universe then you seem to be "imposing another dimension of time". Merged post follows: Consecutive posts merged Sorry Michel but I think the aspects that are being discussed are basic and therefor needed to be solved before we can continue. I would like you to extend this thought and explain more about it.

No, I agree with Sisyphus and Iggy about this: But not to the idea that the Universe can be viewed as stricktly spatial 4D. I am still waiting for Sisyphus or Iggy to continue to explain the following: A slice of a thought has a nonzero time dimension but without a connection with the other slices it is no longer a thought, it is only one single slice in a unobservable serie of different slices. I don't think we are able to have this thought or be aware of it without the changes between the slices being observable. Thus without a serie of actions or a progress of events the slices are doomed to be lifeless in a frozen surronding and not on their own be able to consciousness and be aware of how time flows or be able to perform a calculation. In this universe it seems impossible for a human to think and remember. One slice can not be aware on its own, and for a line of slices to be aware together they need to be connected which they can't be in a *pure* spatial 4D Universe.

I have been stubborn and not able to understand Sisyphus and Iggy, but I was wrong and they are correct. If we treat time as a *pure* spatial dimension then there can't be any movement at all, either in space or time. All objects in such a universe must also consist of four spatial dimensions, they would have length, width, depth, and duration. The Universe would then have a spacetime like frozen jelly, which would be deformed, both compressed and streached, objects inside would look like threads piercing through it. However that 4D view of the Universe also has some problems, or at least I am not able to fully imagine it yet and might still be confused about it: 1) Such an universe seem to me to be absolute, if we were able to step outside of that 4D universe and look at it from outside then even if two observers inside is not able to agree on the order of events, from an outside view it would be possible to imagine a translated version of this universe with a released tension in the jelly and from the relaxed view one could decide which event took place first or last. 2) This universe would also be fully determined, even if observers inside it can't predict the future it would still be there already fixed, to every small detail. If nothing ever changes then the start or end of objects are locked. From an outside view everything would be known and all actions have already happened. 3) Objects inside this universe consists of different "time" slices which are not able to relay information to each other in any direction. From the outside it would be possible to look at a human or a computer and make the observation that it is processing information, as each slice in the row is slightly different. But on the inside where the slices are separated and where each slice is not able to on its own be conscious or perform a series of operations, this row would not be observable, the series of unconnected slices would not be able to notice that they are part of a changing serie. I want to stress this part: A slice of a thought has a nonzero time dimension but without a connection with the other slices it is no longer a thought, it is only one single slice in a unobservable serie of different slices. I don't think we are able to have this thought or be aware of it without the changes between the slices being observable. Thus without a serie of actions or a progress of events the slices are doomed to be lifeless in a frozen surronding and not on their own be able to consciousness and be aware of how time flows or be able to perform a calculation. In this universe it seems impossible for a human to think and remember.

Well, I am trying to defend a concept so of course I appear defensive, but you don't have to worry I don't take it as a personal attack at all. But I disagree, I think both perspectives should be able to fit with each other, they might be viewed from different angels but they should still be in agreement. (Leaving out the representation of such a reality in spacetime diagrams.) Yes the concept tries to unite the two views of time, since in the true world time only has one set of properties, so one of our perceptions must be wrong, we can't have it both ways. You seem to imply that the "intuitive perspective" of movement through time is only a illusion and does not fit with the true physical world. In your physical view, how do you manage to explain that a "slice" of your 4D self is able to be conscious and be aware of how time flows? SPACE - If you move one meter with respect to time, then similar you would also move one second with respect to space. (I thought I was very clear on that in my previous post.) Yes, I agree, but look at your own words: "The same" and then look at the question you asked above. Displacement or movement might be the wrong words for it by definition but those are the only words I have, so I am forced to use them. I tried to explain that since space and time are related, the relation goes both ways. If time dimension can be treated like a spatial dimension, then a 'movement' through time is similar to a movement through space but with changed positions by their relation. There is no need for extra dimensions. Either we move through spacetime or we persist for a duration of spacetime, in the latter objects don't truly move through space either, they are then shaped in such a way that their slices are spread out in different space locations, but the individual slices don't move from one location to the other, they are fixed as firmly in space just like they are in time. Can it be proved scientifically which is true and which is false? But we don't know if objects are truly four dimensional, or if their size in the time dimension is the same as how long we can measure that they last. For instance what happens to your vision of a 4D object when a "slice" of it reaches beyond the event horizon of a black hole? (Where time becomes space and space becomes time.) Can we by experiment measure and verify objects true size in time? (The question is not necessary how long the object lasts.) Also somewhat realted, if objects are 4D with the full duration like you assume, then how do your view fit with the uncertainty principle? When is it determined when the object ends and how is it determined? (Without something progressing through time it seems deterministic.) But you cut the question in half and only answered the first part... Is it possible to determine the properties of time itself?

Accelerating universe The accelerating universe is the observation that the universe appears to be expanding at an increasing rate. In 1998 observations of Type Ia supernovae suggested that the expansion of the universe is accelerating since around redshift of z~0.5. Corroboration In the past few years, these observations have been corroborated by several independent sources: the cosmic microwave background radiation and large scale structure, age of the universe,as well as improved measurements of the supernova and X-ray properties of galaxy clusters. http://en.wikipedia.org/wiki/Accelerating_universe

The question is deeper than how to interpret a spacetime diagram and if you reread my post now that you have gotten your feet wet, you will see that I did not say IA was wrong, I was only trying to be helpful and bring him up to speed in the discussion. It might look wrong and probably is not the best way to visualize this model of spacetime, but that was what Michel was asking for and since he seems to understand it, it served its purpose. I don't think the main thought of movement through time is "nonsensical" but I could be wrong, I will return to this further down. I don't think I understand what you are saying here, first you say it's only a opinion and not a physical difference, which I agree with, but then you say that I am the one having trouble. My perception of time could very well be wrong but then it's not a matter of opinion, then it can be proved by evidence. We are not today able to go into the past or future as we want and by direct observation measure how the dimension of time behaves, if the past and future exists and what or how objects and events are contained. All we have is signals that arrive from here in the present that was emitted in the past. So we are forced to try to deduce from other experiments, like relativity, how the true four dimensional spacetime really are. And btw, you neglected to tell us how you perceive time, am I correct in assuming that you share the view that Iggy has, that there are a infinite amount of Earths for every time the Earth has been to the end of Earth in the distant future? No, nobody is arguing that the Earth didn't exist yesterday, are you arguing that the Earth still exists yesterday? I disagree, I don't think the thought "Change the past" is meaningless, from a philosophical standpoint it is very interesting and we need to ask this cind of questions to push our knowledge further. "Change" could be a difference between two points in time or between two points in space. In a four dimensional coordinate system there is no obvious difference between a displacement from coordinate (1,1,1,1) to (1,2,1,1) as from a displacement from coordinate (1,1,1,1) to (2,1,1,1), besides from different end locations, but in both cases the displacement has been of one unit. Now if I say that the coordinates are (time,length,height,width) and that when a object is displaced in either of the space dimensions it will no longer remain in the old location, then no one will argue, but when I say that the displacement is in the time dimension then suddenly it is "obfuscating". The basic of the question is if the temporal dimension can be treated like a spatial dimension or not and if it is possible to determine the properties of time itself. IMHO, I think the question is valid even if the thought of moving through time will turn out to be wrong. OK, this seems to be a main argument and since I promised to return to it, let's try to determine where/how our views differentiate about the rate of time. I think that it is evident by the concept of the arrow of time and our unique position that always is placed in the present, that there clearly is something progressing. If something is changing it doesn't have to involve extra dimensions, if I move 1 meter then I have moved 1 meter and nothing more, likewise if I move 1 second then I have moved 1 second. In a spacetime diagram you can see the revelance between time and space locations, so you can say that during 1 second you moved 1 meter which will give the speed of 1 m/s during the movement, but you can also say that during the transfer of 1 meter in space you moved 1 second in time. You don't need any extra dimensions to understand that concept, the progress through time have a rate just like a movement through space. I once read that Einstein had said that: "we are all moving through spacetime with the speed of light", or something similar, I can't find and verify the quote, but with the theory of relativity time and space where united in a dynamical 4 dimensional geometry with a rate of time or scale of space that can change depending on frame of reference. If there are two observers at rest with each other, one is in mostly empty space, inside a great void and the other is deep in a strong gravity field, like very close to a supermassive black hole, then they will not be able to agree on how fast time is ticking, they will be able to measure a large difference in their observed rate of time, this time dilation doesn't utilize or need different time dimensions. How is this rate of time different than moving through time at a rate? No, I don't think the rate of time needs another dimension, se above arguments. Not at all, movement is a displacement, a transfer between two different locations. (Speed on the other hand is distance divided by time.) Well, you are now... The concept allows for unobservable changes in the past, but all events that did happen when it were our present, when we passed through that spacetime location, did happen and their consequences are observable today. Lets analyze this comment further: 1) Do you claim that the future is not only determined but that there is a future Earth already there? 2) Here you accept that time has a progression rate but also that it can differ between observers too? 3) For the observer moving close to SOL there will still only be one Earth in this 'tomorrow', he is not able to communicate with any Earths in his yesterday. 4) For the observer on Earth he would seem to arrive at the spaceships 'tomorrow' but he can also only communicate with one spaceship in his present. 5) In both your view and my view there will only be one Earth placed where it should be in each frame, so there is no violation of conservation laws. Well thats a big IF in there and thats why I marked it very clearly in my post which you omitted to quote. IF objects travels through time then it would clearly be a different kind of time than what you think, but in THAT view it is a consistent logicall statement and not a contradiction at all. I am definitely NOT proposing that one objects exists both in the past and at the present simultaneously.

You can put it everywhere in our past without us being able to see it from anywhere in the present. IA the question goes a little deeper than how to read a spacetime diagram... Do you belive that time is a dimension similar to space which we travel through or that our past is frozen stiff with our past selfs and everything included? If we view time lika a filmstrip in a movie, then the objects either can remain frozen in all the pictures or they could travel from frame to frame, leaving old pictures empty. IF objects travels through time you could not go back to Earths 'yesterday' and find 'yesterdays' Earth there, instead you would find an empty location since the Earth had moved on towards the future and is here in the present now. In such a view a spacetime diagram would only show how objects and signals moved through that episode of time and space, and not that the objects still exists in the past spacetime locations nor that the past events still continues to happen in the past. I think Cap'n Refsmmat said it well in post #127: What Michel seems to be asking is: If anything changes in our past, when it already is in our past, would we be able to notice it now in the present? and If we leave our past empty how can we know if 'new' alien objects aren't causing 'new' events back there?

The spaceship flashes with a red light every 0.2 seconds to visualise how light travels outward from it. The laserbeam and objects have their past locations colored in grey to show their paths trough spacetime.

All three observers, located at Earth, in the Spaceship or on the Moon sees the other two continuously. But the images they view are old and came from events in the past, the objects are no longer there, they have continued to the present. Earth observer sees an 0.40 seconds old image of the Ship and an 1.30 seconds old image of the Moon. Ship observer sees an 0.42 seconds old image of the Earth and an 0.88 seconds old image of the Moon. Moon observer sees an 0.90 seconds old image of the Ship and an 1.30 seconds old image of the Earth.