Spyman

1. Lightwaves get stretched together with space when it expands. "Two different sources of redshift: Top, Doppler shift: the star moving to the left emits light that is blue shifted in the direction of the receiving antenna that the star approaches, and red shifted in the direction of the receiving antenna that the star is leaving. Center and bottom panels: cosmological expansion: The distance between the emitting star and both antennas increases while the light is propagating, increasing the wavelength of the light seen by both antennas. Each panel shows the propagation of light over two periods: in the center panel at time of emission the wavelength is short, and in the bottom panel at time of reception the wavelength has stretched with the expansion of space. Patterned after Koupelis & Kuhn. The reader is cautioned that too literal an interpretation of this figure can be misleading. In particular, the Doppler shift panel is seen from a single inertial frame, that of the two antennas. The cosmological expansion panels are a concatenation of local inertial frames spanning the space between the various locally stationary objects." "As a result, photons propagating through the expanding space are stretched, creating the cosmological redshift. This differs from the Doppler effect redshifts described above because the velocity boost (i.e. the Lorentz transformation) between the source and observer is not due to classical momentum and energy transfer, but instead the photons increase in wavelength and redshift as the space through which they are traveling expands." http://en.wikipedia.org/wiki/Redshift 2. The mechanism how space does expand is not known, but observations confirm that the redshift is increasing with increased distance and that the expansion is accelerating. "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 "Hubble's law describes the observation in physical cosmology that the velocity at which various galaxies are receding from the Earth is proportional to their distance from us." "The law is often expressed by the equation v = H0D, with H0 the constant of proportionality (the Hubble constant) between the distance D to a galaxy and its velocity v." "The most recent observational determination of the proportionality constant obtained in 2009 by using the Hubble Space Telescope (HST) yielded a value of H0 = 74.2 ± 3.6 (km/s)/Mpc." http://en.wikipedia.org/wiki/Hubble%27s_law

Some links you might find interesting to visit: Mars Exploration Rover Mission Wikipedia Planet Mars

Scandanavia is not separated from the continent and since 2 July 2000 the Oresund Bridge between Sweden and Denmark has been opened for public traffic. "The Øresund or Öresund Bridge (Danish: Øresundsbroen, Swedish: Öresundsbron, joint hybrid name: Øresundsbron) is a combined two-track rail and four-lane road bridge-tunnel across the Öresund strait. It is the longest combined road and rail bridge in Europe and connects the two metropolitan areas of the Öresund Region: the Danish capital of Copenhagen and the Swedish city of Malmö. The international European route E20 runs across the bridge and through the tunnel via the two lane motorway, as does the Öresund Railway Line. The construction of the Great Belt Fixed Link and the Øresund have connected mainland Europe to Sweden and the rest of Scandinavia." http://en.wikipedia.org/wiki/Oresund_Bridge

That's not important, it's the idea that counts, think of it more like a thought experiment and not about what cind of signals we have or not. (But did you somehow miss the part about sound going slower than light?)

That seems to be the basis of Iggys arguments, spacetime diagrams are not meant to visualise objects with different presents moving through time at some interval between each other. But whether spacetime diagrams are able to show this or not, can't be used to conclude if objects truly moves through time or not in the real world. Merged post follows: Consecutive posts merged Michel have you ever observed a fast and loud airplane cross the horizon at low altitude? I still carry a faint memory of a small boy, standing beside his father and watching a military aircraft roar very fast across the skye, just above the treetops. The little boy made a remarkable discovery, when he looked towards the sound of the aircraft it wasn't there, it was instead moving ahead of its own sound. The location where the sound came from was empty and the location where the vision came from was silent. When the aircraft had vanished in the distance, the boys father tried to explain to his child that sound and vision travels with different speed through air and since vision is much much faster, the sound only seems to come from an empty place, but when the sound was emitted the aircraft was actually there making the sounds. The boy however was still to young to grasp the concept that sound and vision was also something moving through the air like the aircraft. Now I understand that light travels with such high speed that it seem to be instant for us humans locally down here on Earth, and that when we observe stars moving in space the distance is great enough for the location where we percive the vision of the stars to come from, to be empty when the light reaches our eyes, because during the travel time for the vision the stars has also moved, like with the airplane and its sound. Maybe I am rambling to much but what I am trying to say that a key part of the understanding is that the signals themselves are also progressing through time along their own worldlines, which happens to fit exactly with the lightcone if the signals are photons, but you could also have other signals moving with slower speed too. Sometimes it can help to compare the views, how it could seem to look differnet if the signals would be moving slower or even faster than light, but in reality there would still only be one trajectory from where the object are sending out the signals we recieve simultaneous, but the transmitting takes place at different events from different timestamps and locations. I don't know what else to say, you need to find and ask the question which will enlighten and reveal the information you need to complete your understanding.

Michel even if you are 'completely wrong' it doesn't mean that Iggys view is correct, but you still need to figure out and correct your own troubles.

I am sorry but I don't seem to be able to interpret your answer... [EDIT] Sounds like a normal Universe that we observe today.

What thickness would such shelves typically have then?

But why would we expand human civilization to harsh environments on Earth versus to another planet? It would be even easier and more desirable to expand our cities instead if we don't want to colonize beyond Earth.

Another 'subverse' moving behind or before us in time?

Please do note that you are posting in the Science & Physics section and such discussions are probably more suited to bring up in the Philosophy & Religion section.

I am sorry too Iggy, because I didn't think it would be this hard to reach an understanding, our communication fails miserably and it has reached ridiculous proportions. I would have hoped that we had gone beyond this part by now so we could have an interesting discussion about different models and implications from relativity, but until I am able to interpret you correctly it would only be a waste of time to continue further. You made a very long and hefty reply and after reading it several times, sleeping on it and then reading it again, I can only come to the conclusion that you successfully manages to dance around the subject, occasionally touching it but never truly step out from the shadows into the light and express clearly whether you agree or disagree to the following statement: "The entire physics community has not so far been able to reach a consensus on how time really acts. We are not able, with current knowledge and technology, to by direct observation or by logic conclusions from verified theories distinguish whether objects persists through spacetime or travel through spacetime in the real world." You have to either agree or disagree, you can't have it both ways and you can't have it half way either. (Note that I do not mention any specific models or representations in the above statement.) I think you have a good argument that might put constrains on some models but since we don't manage to pass step one there is no point in commenting on something that probably belong in step three or four...

I'm not interested in proving or disproving the metaphysical or ontological nature of time. I want a very clear and precise answer to this one, because if Iggy is making claims that it is possible to disprove Endurantism by observation, then it would need to be backed up with massive evidence. I've made no "claims that it is possible to disprove Endurantism by observation". You assume that the moving dot diagram is a good representation of Endurantism. That is not the case and that is what I am focusing on. Well Iggy, I don't think that was a good answer, you are still avoiding the main point of the question. You seem to claim that it would be possible to by observation differentiate whether objects travel through spacetime or persist through spacetime and from my understanding that is inconsistent with the current scientific view. I don't care if a diagram of model X is good or bad at representating theory Y and I think I made that clear too in previous posts. Either you agree that it is not possible or you need to explain a possible experiment where the results will falsify or validate how time really acts.

First I want to nail this issue, which is my only disagreement with Iggy: It seems a little vague. A confirmed theory could, at the least, disprove an ontology of time. So that we can get rid of statements like this: From my understanding the entire physics community has not so far been able to reach a consensus on how time really is and/or behaves so theories like Endurantism are concerned valid and not yet disproved. Since it is not disproved by science, it clearly can't have 'inconsistent observational consequences'. I want a very clear and precise answer to this one, because if Iggy is making claims that it is possible to disprove Endurantism by observation, then it would need to be backed up with massive evidence. ---------- Then I will also try to explain the view of moving through time further: and I think I understand Iggy's view and don't really disagree with it, it is a valid view that time is like a dimension in which events occur in sequence where objects and events persist like frames in a film strip. (I will return to this movie analogy later.) No, I am not, I am trying to explain a different view of time, but I seem to fail miserably... I can only se one time and one space dimension in both these two views: The only difference I can see is that spacetime is empty before and after the objects in their paths. TimeB counting to 5 seconds, I can't understand at all. [EDIT] Wait, scratch that, it is supposed to represent the rate of movment through time. But as I mention further down time does flow with a rate, that is nothing new. But time still has a rate and according to relativity it can change between different observers, so movement from one timestamp to another seems to be able to happen, and at different rates too. [EDIT] Look at this diagram from Wikipedia: Note how both the distance of space and rate of time changes. "Changing views of spacetime along the world line of a rapidly accelerating observer In this animation, the vertical direction indicates time and the horizontal direction indicates distance, the dashed line is the spacetime trajectory ("world line") of an accelerating observer. The small dots are arbitrary events in spacetime that are stationary relative to each other. The events passing the two diagonal lines in the lower half of the picture (the past light cone of the observer) are those that are visible to the observer. The slope of the world line (deviation from being vertical) gives the relative velocity to the observer. Note how the view of spacetime changes when the observer accelerates. In particular, absolute time is a concept not applicable in Lorentzian spacetime: events move up-and-down in the figure depending on the acceleration of the observer." http://en.wikipedia.org/wiki/Time No, what I was asking is if we went back in time with a timemachine would we find a Sun there frozen in a timestamp or if the past spacetime would be empty as if the Sun would have moved towards the future at a rate of time. Let me put it this way: If time is like a film strip and space are the frames of each picture, then objects could be 'jumping' from frame to frame towards the future and thus leaving the old frames empty. The present is then the frame where the objects is or the frame that is displayed and the future frames is still waiting but empty. If we had a timemachine and went back to a past frame to look, then it could be empty or it could still contain the objects as they where. We are not looking at two timestamps at the same time or proposing two kinds of time. Until I am able to explain this concept of time it's difficult to discuss the differences and compare consequenses of them with you, hopefully the movie analogy will settle this. ---------- I don't see any more problems with this in the moving through time concept versus the persisting through time concept. Every observer has his own view of reference with his own past/present/future lightcone and while different observers don't agree on either distance in space or rate of time, each of their observations are as valid as another. They might even disagree on the order of events. I would like you to explain more of why you think it would be different problems between the concepts.

"Scientists have come to some agreement on descriptions of events that happened 10−35 seconds after the Big Bang, but generally agree that descriptions about what happened before one Planck time (5 × 10−44 seconds) after the Big Bang will likely remain pure speculation." http://en.wikipedia.org/wiki/Time (Mine emphasis)

Hmm, the discussion has developed a lot during the weekend and left me somewhat behind, I must say that mostly I agree with what Iggy says, but we might still disagree about the concept of moving through time, or we are misunderstanding each other, so I will try to clear up that part. First of all Iggy don't seem to quite look at the moving dot concept like me, and further more Iggy is talking a lot about the meaning of representations in the spacetime diagrams, but I am talking about the real world. So question No:1 is if when Iggy only means in spacetime diagrams and when it's about the real world too? If it is only about the use of spacetime diagrams, symbols and representations, then I think Iggy is correct and there is nothing more to discuss. And question No:2 is if Iggy understand what I mean with moving through time or if Iggy thinks of something different? The diagram in Iggy's post #89 shows a different view of moving through time than what I meant, I don't think objects in the past are moving forward in time behind us. I will try to explain my view once more and hopefully Iggy will understand, even though my english don't seem to be powerful enough, I have a hard time finding the correct words even in my own language. In Relativity space and time are considered dimensions that objects are moving through, and when an object moves from point A to point B it's not hard to see that the object is no longer in point A, so if we consider time dimension to be similar to space then it is possible to view time as if an object moves from time A to time B it will no longer be in time A. I am NOT claiming that time is in that way, all I am saying is that we can't verify if it is or not. [EDIT] Found this at Wikipedia: "Endurantism or endurance theory is a philosophical theory of persistence and identity. According to the endurantist view material objects are persisting three-dimensional individuals wholly present at every moment of their existence. This conception of an individual as always present, is opposed to perdurantism or four dimensionalism which maintains that an object is a series of temporal parts or stages, like the frames of a movie. Some philosophers argue that perdurantism better accommodates the theory of special relativity. The use of "endure" and "perdure" to distinguish two ways in which an object can be thought to persist can be traced to David Lewis." http://en.wikipedia.org/wiki/Endurantism So question No:3 is if Iggy thinks it is possible to verify by observation how time really is? You would think that traveling back in time to see if there is a sun and earth would reveal the truth of this. So, I might go back a couple thousand years and stand next to Cleopatra and find out if the sun and earth are there. That would settle the issue for you. But, how is that different from what Cleopatra saw? Can I not take her word on this? The sun was here yesterday and two thousand years ago and we don't need a time machine to prove it. The consequences of this moving dot idea are shown very clearly in the diagram in my last post. The consequences are incompatible with observation. Well if the Sun and Earth are not there then certainly Cleopatra will not either, no one is arguing that the Sun did not shine in Cleopatra's time, the question is if time is like a spatial dimension in that way that objects in the past can remain there in that past spacetime location or if they move forward in time. How would our observation differ whether there would be a Sun remaining in the past or not? The entire physics community is convinced of that. It is explained in the links I've given through the thread. There is a reason a world line is a line. There is a reason Minkowski made it so. Conservation of energy and all of our human observations demand it. If you are talking about symbols and representations in spacetime diagrams it's fine, but if you are talking about how the science community are looking at time then you are very wrong. There are plenty of views of time, more than the two we are discussing here, several of them are concerned valid by the community. How would the difference wheter the Sun remains in the past or not break conservation laws? I have not said and not implied that past events exist somewhere No you didn't say that but for the sake of the argument, from my point of view you seem to be implying that objects *must* remain in the past, as they where during the event. Which they might very well be, I am only arguing the 'must' part or more precisely whether we can distinguish between if they are or not. And to make it clear, they where evidently there when the events took place, the question is if they still remains there, if we would travel back now. We can prove that the sun was here yesterday and in the distant past with conservation of energy or Noether's theorem or we can prove it through direct evidence. Blue-green algae was using photosynthesis billions of years ago. Again, nobody is arguing that we can't prove that the Sun was here yesterday or in the distant past, the question is if the Sun still exists in the past. Can you prove that time behaves in such a way that it is possible for the Sun to continue to exist in the past? But, regardless, either an object's path through spacetime is a curve or a moving dot. I don't know if the universe is really four dimensional in a philosophical sense, but I know that when it is represented that way with a spacetime diagram an object's path cannot be a moving dot. It must be a line or a curve. The two different representations have different observational consequences. In other words, I don't need to argue that "an object is a line", only that it must be represented that way in 4 dimensional spacetime. I agree with "when it is represented that way with a spacetime diagram an object's path cannot be a moving dot" but we don't know how time is in the real world, object might move through time and leave past locations empty, and that could be represented by moving objects along a path, like a world line. There would not be any differences either in representation nor by obsevation. Well I do have a different meaning, so your diagram is wrong from my point of view. I agree that it's not good to represent time that way, but that doesn't imply that time is a two dimensional construct or that it would not be consistent with observation. How would it be possible to observe such an object, like a timemachine suddenly entering our past? This wording I fully agree with. Agree with the red and black dot can never interact. But in reality objects is separated by space and need only persist for the duration of the time for signals to traverse that separation and they will be able to interact. If there was an object separated by time like in the diagram, say a timemachine, then we could not observe nor interact with it. I fully agree to this. Here again it sounds like we are in agreement and that you only object to the use of symbols an meanings in a spacetime diagram. and Past events don't exist somewhere (by which I mean some place). They existed at a place and time. I existed in the center of central park on December 31, 1999--a place and time--an event--(x,y,z,t). To say that past tangibility exists somewhere would mean to me that I can currently interact with the past event. But, I don't believe that. I can't affect Neil Armstrong walking on the moon. I have not implied that. Past events are not currently tangible. Here it sound that you are arguing against me, 'you existed' in a past spacetime location, but the question is do you still exist there or are you here now or are you both there in the past and here in the present? The past spacetime locations could be viewed as still existing but out of our reach, beyond our observable horizon, how could we then decide, if Neil Armstrong is still walking on the Moon in the past? Past events are not currently tangible but the objects involved in the events are observable now - so have they moved from the past or have the past objects somehow managed to duplicate themself into the present? But that is not the point, the point is if we would have a timemachine and travel back to the event of a past Iggy event, would there be an Iggy object there, frozen in a timestamp or would that past spacetime location be empty now, since you are here in the present now, creating new events? Remember that all I am claiming is that we can't differentiate which is true or false. I fully agree to this and have nothing further to add to your last post.

Well, on March 10, in 1982 the planets Mercury, Venus, Earth, Mars, Jupiter, Saturn and Pluto was on the same side of the Sun, within a 95 degree wide interval, and yet we are still here... Nr.8 in the Link: Ten Notable Apocalypses That (Obviously) Didn't Happen

If you look carefully, you will see that the red spot is always one step behind the black one. The horizontal projection of the red spot upon the time axis maintains a standard gap with the black dot. Then when/where was the red spot at the event of the Big Bang ? My point here is that I don't think such objects exists naturally and if they do exist they can't interact with us in any way at all. The only way to find out would be to use a timemachine but that might not be possible either. So until such objects can be observed or at least explain something in theory, it is more convenient to remove not necessary phenomenon from our models. If you make a thought experiment with a hypothetical timemachine represented by the red spot, that would be fine but assuming that the Universe is filled with objects like that would only seem 'messy'. That's the question. We can only observe, not the present, but a particular part of the past: the light-cone (our light-cone). No no no, I don't think thats questionable. We can observe objects and then calculate where they are supposed to be at the present, later on we can observe them again and check if our model is correct. So far we have NEVER observed any object with trajectories leaving or entering our present to/from the past or the future. I don't think timetravel is completely ruled out but those trajectories is certainly not something that normally happens around us. It is impossible to observe, O.K. And you are probably right, it may be a paradox. But in this case, you have to admit that instead of the object I proposed, the Earth is there. And is this case, Earth's mass is distributed in the past, see the MT surface. If a timetraveler would go back in time and find Earth there as it was, then Earths mass is 'distributed in the past', but it would not make any observable difference on objects in the spacetime diagram. Yes. and no. There would be a difference, because a slice of MT in the past can influence other objects upon the light-cone. See object A in Iggy's first diagram. There is no difference because objects are supposed to influence each other. We are influenced by signals from objects in the past and they in turn are also influenced by signals from objects in their past, which in turn are influenced by signals from objects in their past and so on, there is nothing strange with that and it don't make any difference whether the objects remain in the past or not either, since it is the signals from them that are influencing us, not the objects themself. Let's take a look at Iggy's diagram again and revive what happens: - At event A a Star goes nova, sending out EM and the reconfiguration of mass sends out new strength of gravity. - At event B both the EM and the new gravity strength from the nova reaches Planet X. - At event C both the EM and the new gravity strength from the nova reaches Earth. - At event D we can observe how the EM lights up Planet X and how the new gravity strength affected Planet X. Now tell me in which of the events would either we or the aliens be able to observe or measure more than one of each of the other objects ? And for the third time what would be different if the objects remain in the past or not ? ---------- Iggy consider if EVERY objects move through time towards the future and are not allowed to have trajectories where they leave the present, then the lightrays from the Sun will continue to shine on Earth, since both the Sun, the photons and the Earth would travel towards the future. And even though the Earth was there when our ancestors rised and started to walk, today both the remains of our ancestors and the younger Earth has moved on and are here, in the present. The only difference we would notice are if we used a timemachine to go back and look. ---------- From Iggy's last post I think we can recapitulate our standpoints as follows: - I think it's impossible to distinguish whether objects move through time or remains in the past, without a timemachine or other not yet available technologies or knowledge. (Although I prefer to view objects as "moving dots".) - Michel thinks it is possible to differentiate between the two concepts but doesn't seem to have an idea or be able to explain how that could be done. (Michel tend to conclude that objects are not "lines", but "moving dots".) - Iggy thinks that it is possible to deduce which is correct of the two concepts and is certain that if something occupies a location sometime then that specific place and time is taken forever. (Iggy is convinced that objects are "lines".) All three of us agree that a fixed dot in a spacetime diagram is an event and that the objects either are the world line or moving dots that must follow it. Your turn...

Did you miss my post #80 ? If the Earth 'remains' in the past and someone with a timemachine goes there, what would happen ? A lot of people view time as if they could travel back then they would physically be able to interact with their own old self. Either the timetraveler creates a paradox or the timeline is forced to change, like in the movie Back to the Future.

Farsight, I think the author is actually arguing against the frozen star concept... "Consider a black hole of mass m. The event horizon has radius r = 2m in Schwarzschild coordinates. Now suppose a large concentric spherical dust cloud of total mass m surrounds the black hole is slowly pulled to within a shell of radius, say, 2.1m. The mass of the combined system is 2m, giving it a gravitational radius of r = 4m, and all the matter is now within r = 4m, so there must be, according to the unique spherically symmetrical solution of the field equations, an event horizon at r = 4m. Evidently the dust has somehow gotten inside the event horizon. We might think that although the event horizon has expanded to 4m, maybe the dust is being held "frozen" just outside the horizon at, say, 4.1m. But that can't be true because then there would be only 1m of mass inside the 4m radius, and the horizon would collapse. Also, this would imply that any dust originally inside 4m must have been pushed outward, and there is no known mechanism for that to happen." From your own link: http://www.mathpages.com/rr/s7-02/7-02.htm Did you read and understand the Chapter 6.4 that was mentioned before the text you quoted ? "Therefore, at r = 2m the curvature of this surface is -1/(4m2), which is certainly finite (and in fact can be made arbitrarily small for sufficiently large m). The only singularity in the intrinsic curvature of the surface occurs at r = 0." "and we can confirm that the radial coordinate passes smoothly through r = 2m as a function of the proper time t." From Chapter 6.4: http://www.mathpages.com/rr/s6-04/6-04.htm

Here is another view of the answer from Astrophysicists at NASA: The Question (Submitted August 08, 1997) What is the volume of a black hole? The Answer Our intuitive sense of volume breaks down in the strong gravitational region in a black hole. So while the "size" of a black hole is given by the radius of its event horizon, it's volume is not determined by the usual 4/3*pi*r3. Instead, relativity makes it more complicated than that. As you pass the event horizon, the spatial direction 'inwards' becomes 'towards the future'-- you WILL reach the center, it's as inevitable as next Monday. The direction outsiders think of as their future becomes a spatial dimension once you are inside. The volume of a black hole, therefore, is its surface area times the length of time the hole exists (using the speed of light to convert from seconds to meters). Since a black hole last practically forever, the black hole's volume is almost infinite. (This is also a way of explaining the fact that you can pour stuff into a black hole forever and never fill it up. Another reason why black holes never fill up is that the radius of the event horizon increases as the mass of the black hole increases.) David Palmer and Jim Lochner for Ask an Astrophysicist http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/970808.html

How did the red spot get behind us on the time axis, if it is moving through time with our speed ? You can have objects missing Earth because they are arriving late but the objects are not allowed to have trajectories where they leave the present. A normal object missing Earth would still be in our present time when it is in our past space location. If you have an asteroid moving one day behind us in time entering the Earts spacetime location one day ago, it would have hit Earth yesterday, but it didn't do that yesterday when we where there, so you end up with a paradox. If it's impossible to change what did happen in our past then such trajectories must be impossible for us to observe too. The MT surface don't make any difference since each slice of time can't notice or interact with things outside of their horizon, for every timestamp there would still only be one point mass for each object.

According to current models and observations it is not possible for a physical object to move slower through time than us in our frame of reference. If such an object would exist it would be beyond our horizon and therefor not observable and impossible to interact with. [EDIT] I don't think the "mass-time surface" is adding anything but confusion in the diagrams.

Waiting for you to explain the purpose of the added events...

Ok, nothing new yet, continue...