Astronomy Without A Telescope – A Photon’s Point Of View

103 Replies to “Astronomy Without A Telescope – A Photon’s Point Of View”

1. This is the best “down-to-earth” explanation I’ve seen recently. It’s always bugged my when the stars wisk by in Star Trek. Other then the sapce-time discussion, also for the “everything is really far away” argument, since apparent angles change very little even at fast speed. Even using the bubble concept (warping space-time in a bubble, expanding at the front, and condensing at the back, similar to a bubble going upstream in a tube), disant stars should show as a moving point of light not a streak, if they show up at all.

   1. A SOL trip (thought experiment) involves you arriving at your destination immediately after pushing the Go button.

2. The like button is not working…..

   1. Seems to be for me…

      Mary

   2. agreed, the facebook like button does not work … the Disqus one does though

      1. Yeah, it’s been like that for a while.

3. The universe is stranger than we imagine, it may even be stranger than we can imagine.

4. Yo Steve, at the last paragraph, as the context is plural, it should be there are, not “there’s”.

   1. Sorry – trying to sound ‘street’ 😉

5. Yo Steve, at the last paragraph, as the context is plural, it should be there are, not “there’s”.

6. There are two (at least) ways of looking at this. You can think of a force acting on every atom of a spacecraft and its occupants equally so the floor of the vehicle and the passenger experience the same force. Or, you can think of all objects moving in space as following a geodesic. Again there will be no relative forces within that moving inertial frame.

   1. Agreed – the psuedo-force argument is 3+1 thinking, the geodesic argument is space-time thinking.

   2. Geodesics are strange to me, even more so when applied to something as abstract (IMHO) as spacetime.
      I get it that they are good at predicting movement of objects in gravity and all that, but what do they explain? And then I mean as in what do we learn about space and time from them? Finding a graviton would teach us a lot about how space and gravity works. A formula itself does not, it only explains what happens.

      1. Geodesics comes out or general relativity, which is a special relativity consistent theory.

         Special relativity gives you light-cones (how light propagates causally) so spacetime, and equivalence between mass and energy so mass-energy. General relativity connects spacetime curvature (geodesics) with mass-energy (inertia-mass equivalence).

         … that is it, in a nut shell … [/goes away for more coffee.]

7. There are two (at least) ways of looking at this. You can think of a force acting on every atom of a spacecraft and its occupants equally so the floor of the vehicle and the passenger experience the same force. Or, you can think of all objects moving in space as following a geodesic. Again there will be no relative forces within that moving inertial frame.

8. One of the things people do not realize is that we do in fact move at the speed of light. By just sitting in my chair with everything around me largely at rest relative to my position I am in fact traveling at the speed of light. So is everything else. In fact one reason nothing can travel faster than light is because nothing can travel slower than light. The only thing is that there are two different ways of traveling at the speed of light. We and everything with mass does it in one way. Light and massless particle do it another way.

   Relativity is just a form of geometry. In flat spacetime there is a form of the Pythagorean Theorem. In ordinary space, such as planar geometry, the two legs of a right triangle of length x and y compute the distance of the hypotenuse h as

   h^2 = x^2 + y^2.

   In relativity if we consider just one spatial direction x and time t the corresponding equation is

   s^2 = (ct)^2 – x^2.

   This distance for 3 spatial directions (x, y, z) and time t is

   s^2 = (ct)^2 – x^2 – y^2 – z^2

   We consider just one spatial direction and we consider the case of a particle sitting at the origin x = 0. This means this particle is moving along the fourth dimension in this coordinate system at s^2 = (ct)^2. In fact it is moving at the speed of light! So by just sitting in one spot you are moving at the speed of light along this unseen fourth dimension we can only measure with a clock. This is why it is sometimes called a time axis.

   Now let us consider the motion of that particle relative to our rest frame at x = 0. We set the x direction of this particle’s motion as x = vt. Plug this into s^2 = (ct)^2 – x^2 and we get

   s^2 = (c^2 – v^2)t^2 = c^2(1 – ?^2)t^2

   The distance s is called the invariant interval, which is the length of the particle’s path as measured by a clock on that particle’s frame. This time is ? = s/c, and so the time on the particle’s clock and what we measure on our clock at x = 0 is then

   ?^2 = (1 – ?^2)t^2, ? = v/c

   This is the so called time dilation effect, for if we observed this clock on our frame we would see it compute time intervals ?? (time’s between ticks) relative to ours ?t according to this formula with ? = 1/sqrt(1 – ?^2). So assume ?t = 1second and we let ? = .866, or that the particle is moving at 86.6% the speed of light relative to our frame at x = 0. Do the math! And you find that ? = 1/sqrt(1 – .75) = 2, and since ?? = ?t/? it is not hard to see that for every second our clock at x = 0 ticks the particle’s lock only ticks off .5 seconds.

   Now what about the photon itself? We return to the equation above for the interval

   s^2 = (c^2 – v^2)t^2 with v = c == > s^2 = (c^2 – c^2)t)^2 = 0.

   So there is no interval, or equivalently there is no distance associated with a photon path, where that distance would be measured by a clock on the photon’s frame. This is a null frame or a null path. The gamma factor above is infinite, or better said to be undefined as a division by zero. We observers at x = 0 can measure the photon to move at the speed of light, but there is no corresponding measure by any clock on the photon frame.

   These are the two ways of moving at the speed of light. The first of these is called timelike, while the second is called lightlike. There is no way of performing a continuous transformation from one to the other. The blow up of the gamma factor is one main reason, which is that to achieve this it requires an infinite boost, where the Lorentz transformation for this does not have an inverse operation.

   LC

   1. Well we have heard of armchair generals so why not armchair astronomers? This web-site is helpful in understanding the concepts you outline:

   2. Well we have heard of armchair generals so why not armchair astronomers? This web-site is helpful in understanding the concepts you outline:

9. There is so much flawed logic involved in this “thought experiment” that it is difficult to know where to begin. One of the more egregious examples is the statement that implies the accelerating astronaut would be pushed back in their seat. This would only be the case if the astronaut’s spaceship were the source of acceleration, and what the astronaut would be experiencing would be a transfer of kinetic energy at the seat/body interface. This is obviously not the case.

   1. Suffice to say that the whole point of the article is that the accelerating astronaut would not be pushed back in their seat – it’s a free fall.

      If you are looking for flaws, consider the effect of the atmosphere, which would have a braking effect (which might throw the astronaut forward a bit) – in reality a plunge to Earth is not a perfect state of free fall.

10. Here’s a slightly mathematical way to ‘view’ the interplay between space and time.

    We humans live in 3D, x,y,z, each having units of metres.
    We have also some sense of living in time t, with units of seconds.

    We cannot simply ADD metres to seconds to get “spacetime.”
    Just like we can’t ADD litres to kilograms – for – “It does not compute, say the Daleks.”

    But nonetheless, there does exist a way to homologously combine space units and time units, into space_time units.

    Remember Pythagoras’s Law, applied to right-angled triangles ?
    Remember it said : hyp^2 = sideA^2 + sideB^2.
    [“^2” means “to the power of two”, or “squared”]

    If the two sides lay along the y and x axes, we could express this as: hyp^2 = x^2 + y^2.

    And if the axes weren’t exactly straight, because they lay along curved space, we would have to restrict this formula to be true for only itty-bitty lengths, like dx and dy, which are the infinitesimals used by calculus. The we get d_hyp^2 = dx^2 + dy^2
    And we could replace the length along the hypotenuse with some arbitrary length called ‘s’, thus:
    ds^2 = dx^2 + dy^2

    This is always true for right-angled axes, and since we use only x and y, this is in 2D.

    But note how easily it can be extended to 3D, like measuring from one corner of a cube, to the diametrically opposite corner of the cube:
    ds^2 = dx^2 + dy^2 + dz^2
    where x, y, and z are mutually perpendicular, or “orthogonal’, which is mathematics_speak for “at right angles in all dimensions”.

    Now imagine a 4D cube, having 4 orthogonal axes x, y, z, t. You can’t ?
    Don’t worry, humans are limited in imagining things beyond our customary 3D.
    But be reassured, this is indeed the 4space that all humans live in, and perceive (even if time is poorly perceived).

    Now we have to introduce the imaginary number “i”
    (called “j” by electrical people, so it doesn’t get confused with “i” for amperes, which should really be “a”, but that’s another story).

    To indicate that this 4th time axis is ‘orthogonal’ to the 3 other space axes, we multiply time by “i”, and then apply Pythagoras in the same systematic was we have done above. So …
    ds^2 = dx^2 + dy^2 + dz^2 + (i*c*dt)^2

    You will note that the last term has the speed of light (units = metres / sec), multiplied by time (units of secs), and so the multiplied combination has units of metres. Thus all the terms on the right-hand side are in ‘homologous units’ of metres_squared. Thus we are now adding “apples to apples”.

    Hence ds is a tiny bit of “spacetime”, with units of metres (we can take the square root of both sides to get the familiar units of metres – but cosmologists are quite happy to work with units of metres_squared.

    But note that we often use a distance unit of light_years, which is the distance – in metres, or kilometres, that light will travel in one year. Note that ‘years’ have been converted into ‘km’.

    We could just as well use a unit of light_kilometre, which is the time that light would pass in travelling one kilometre. That would convert ‘kilometres’ into ‘years’.

    And thus “space_time”, denoted by “ds”, can be “homologously expressed in units of either light_years, or light_kilometres, and either unit can be added to the other.”

    That is one way of confirming what this article says, at:
    http://www.universetoday.com/87983/astronomy-without-a-telescope-a-photons-point-of-view/
    when it asserts that: “time and distance are just two apparently different aspects of the same thing.”

    All you need is not ‘love’, but Pythagoras.

11. Much of this looks as bad as the New York Times editorial that poo-pooed Goddard’s work because there’s nothing to push against in space. For example, “After all, if they were accelerating, surely they would be pushed back into their seat as a consequence.”: not in the slightest. With gravity, it’s just that the ship and the astronaut are accelerating at the same speed (ignoring tidal effects).

    1. In any context outside of a gravitational field – when the spacecraft is accelerated by a force (e.g. fires its engines – or is pulled forward by a rope), the astronaut will experience an effect of that force (is pushed back into her/his seat).

       You appeal to an invisible force that operates at a distance (Newtonian view of gravity). However, this won’t help you to explain why GPS satellite clocks are set to run 38 microseconds per day faster – to keep pace with clocks on the surface. If you adopt a space-time perspective, you can explain GPS satellites and you no longer need to explain the effects of gravity by appealing to forces.

    2. Out of curiosity what is the math regarding the 38 microseconds?

       1. Einstein’s Time dilation formula. And that is what they measure physically.

       2. Net effect of altitude (clock runs faster) and orbital speed (clock runs slower).

          Try here:
          http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit5/gps.html

          Or podcast here:
          http://www.cheapastro.com/podcasts/CA019_GPS.mp3

    3. I’ve reread some of the replies and another article (q.v.). I found this article to explain nothing. I’m used to the Newtonian notion of velocity, and to the notion of acceleration as the time rate of change of velocity. I have some little idea of special relativity and “velocity” there, but I think it doesn’t deal with accelerated frames of reference. Stating that the ship in free fall is at constant velocity, despite measurements that show it is accelerating, is not explained, so I missed the point entirely.

       http://en.wikipedia.org/wiki/Gravitational_acceleration#In_general_relativity looks like a much clearer and succinct explanation. “The gravitational force is a fictitious force. There is no gravitational acceleration, in that the proper acceleration {link to that article} and hence four-acceleration {link} of objects in free fall are zero. Rather than undergoing an acceleration, objects in free fall travel along straight lines (geodesics) on the curved spacetime.” (With complications about what “time” means.) That at least gives me a vague idea of what’s going on.

12. “Science advocates and skeptics say that we should accept the reality of evolution in the same way that we accept the reality of gravity – but actually this is a terrible analogy. Gravity is not real, it’s just our dumbed-down interpretation of space-time curvature.”

    I don’t think it’s that bad an analogy, actually. Evolution isn’t “real” either. It’s not a process in itself, but a term for the aggregated results of millions of genetic and metabolic and developmental processes at the individual level that, over time, add up to change at the population level. An individual finch is just a finch doing what finches do – it doesn’t perceive itself as a transitional link between its ancestors and its offspring.

    Similarly, a dropped pencil (assume, for this thought experiment, that this pencil is made of sapient pearwood and thus has some self-awareness) doesn’t perceive itself as an object caught in a vast gravitational well extending out to the edges of the Earth’s sphere of influence. It just perceives “down,” and then promptly goes there at 9.81 m/s^2.

    1. Newtonian gravity has been superceded by Einsteinian space-time. Evolution is still current.

       A blindfolded astronaut or the sapient pencil will not be aware they are going down – the whole point of the story is perceptions (experience). Falling you feel nothing, someone else watching from the surface naively assumes you must be experiencing acceleration.

       Nitpicking, but 9.81 m/s^2 is only correct at sea-level.

    2. And due to varying density of earth and the rotation (causing it to be “thicker” along the equator then in between the poles) it varies even more.

    3. It’s not a process in itself, but a term for the aggregated results of millions of genetic and metabolic and developmental processes at the individual level that, over time, add up to change at the population level.

       Congratulations, you have just rejected the whole field of stochastic processes, of which population genetics, the core of the modern synthesis, is a prime example.

       It is much more useful to think of it as a process than as a collection of independent events. Because the fact of the Hardy-Weinerg principle and the Price equation means there is no independence.

       The whole point of population genetics is that selection and drift can fixate genes in the genome, i.e. make one allele or a balance of alleles ubiquitous. (See the links.)

       An individual finch is just a finch doing what finches do – it doesn’t perceive itself as a transitional link between its ancestors and its offspring.

       Well, yes. And this absence of individual perception and agency “purpose”, does it strengthen or invalidate the observation of a process?

       It is orthogonal to it, as shown by examples such as artificial selection. Unless you discuss supernatural agency, naturally.

       1. It is much more useful to think of it as a process than as a collection of independent events. Because the fact of the Hardy-Weinberg principle and the Price equation means there is no independence.

          Fair enough. No organism is an island. Good point. But the fact still remains that evolution is the culmination of interdependent events rather than a process in the true sense.

          When I think of a process – and perhaps this is a misunderstanding on my part – I think of an action with an end goal. DNA replication, for example, is a deliberate process of enzymes unzipping and copying a molecular chain. It’s not always a perfect process, but it is undeniably a process.

          What is the end goal of population evolution? It depends where you draw the arbitrary “population” circle. Are we talking about a particular familial line, or a tribal group, or an entire species, or an entire ecosystem? Yes, one could say the goal is “survival,” but what that means is dependent on where you’ve drawn your population line. Survival for an ecosystem means reaching stable equilibrium, while survival for a nomadic population may mean eating every leaf in that stable equilibrium and moving on.

          Is it useful, for practical purposes, to think of evolution as a process? Absolutely. If we’re trying to prevent antibiotic resistance or identify drought-resistant sorghum crops or figure out the lineage of the baleen whale, it makes complete sense to think of it as a process. But that doesn’t mean it *is* one.

          And this absence of individual perception and agency “purpose”, does it strengthen or invalidate the observation of a process?

          Neither. It is the act of observation that causes the process to emerge. Just like the act of taxonomy causes species to emerge. In nature there are no species. There are just three varieties of other – Mate With, Run From, or Eat.

          We humans taxonomize because our brains like to organize and categorize things. Similarly, we perceive cause-and-effect relationships because our brains are good at doing that. These indeed are products of our evolution – both are critical to our survival. But if we step outside of that human bias for a moment and try and observe nature from nature’s point of view, we see that these taxonomies and evolutionary processes are more our creation than nature’s.

       2. I think of an action with an end goal.

          I suspected that from the argument, which was why I stated the last part of my comment as I did.

          This is called “teleology”. It is a speculation of theology, it can be a useful model for free agents, but it is not a property of processes as such. As in evolution there can be “appearance of design”, for processes we can have “appearance of goals”.

          In math a differential equation describing a process can have initial conditions or boundary conditions. If it has initial conditions it is not “goal directed”.

          This is the case for evolution, btw. We know todays species, we don’t know future species.

          I note you mix ecology with evolution. Not the same theory, not the same processes. Note that in general there is a one-to-one map between theory and process in science since it wouldn’t work well to divide up either system.

          It is the act of observation that causes the process to emerge.

          Sorry, I only do realism.*

          In nature there are no species.

          There are 26 + species concepts in biology. They can be defined and tested.

          Here is part 1 and part 2 of how linnean taxonomy predicts evolution all by itself. (Since evolution predicts embedded sets, and conversely embedded sets predicts the pathways of the process.)

          “OK, so we are eukaryotic, multicellular, bilaterally symmetrical heterotrophs with organized tissues, which develop from a blastula in which the blastopore forms the anus, and which later develops pharyngeal pouches, a notochord, and a postanal tail, and protect their central nervous system with a hard skull and backbone. So, this would make us animals, and more specifically, vertebrates.”

          Evolution appears out of classification, and vice versa, because phylogenies are so constrained. (In fact, that makes them much more certain observations than most of physics observations, though with bad resolution from the spotty fossil record.)

          Really, evolution vs creationism is OT the thread, and OT science. I suggest TalkOrigins for an excellent resource on evolution, species, absence of teleology et cetera.

          ————–
          * We can discuss how realism works, if you will; there is an excellently testable definition for it.

       3. I think of an action with an end goal.

          I suspected that from the argument, which was why I stated the last part of my comment as I did.

          This is called “teleology”. It is a speculation of theology, it can be a useful model for free agents, but it is not a property of processes as such. As in evolution there can be “appearance of design”, for processes we can have “appearance of goals”.

          In math a differential equation describing a process can have initial conditions or boundary conditions. If it has initial conditions it is not “goal directed”.

          This is the case for evolution, btw. We know todays species, we don’t know future species.

          I note you mix ecology with evolution. Not the same theory, not the same processes. Note that in general there is a one-to-one map between theory and process in science since it wouldn’t work well to divide up either system.

          It is the act of observation that causes the process to emerge.

          Sorry, I only do realism.*

          In nature there are no species.

          There are 26 + species concepts in biology. They can be defined and tested.

          Here is part 1 and part 2 of how linnean taxonomy predicts evolution all by itself. (Since evolution predicts embedded sets, and conversely embedded sets predicts the pathways of the process.)

          “OK, so we are eukaryotic, multicellular, bilaterally symmetrical heterotrophs with organized tissues, which develop from a blastula in which the blastopore forms the anus, and which later develops pharyngeal pouches, a notochord, and a postanal tail, and protect their central nervous system with a hard skull and backbone. So, this would make us animals, and more specifically, vertebrates.”

          Evolution appears out of classification, and vice versa, because phylogenies are so constrained. (In fact, that makes them much more certain observations than most of physics observations, though with bad resolution from the spotty fossil record.)

          Really, evolution vs creationism is OT the thread, and OT science. I suggest TalkOrigins for an excellent resource on evolution, species, absence of teleology et cetera.

          ————–
          * We can discuss how realism works, if you will; there is an excellently testable definition for it.

       4. This is called “teleology”. It is a speculation of theology, it can be a useful model for free agents, but it is not a property of processes as such. As in evolution there can be “appearance of design”, for processes we can have “appearance of goals”.

          I think this is actually the argument I was trying to make, albeit less competently. I certainly wasn’t arguing for design, and apologize if it came off that way. This is usually an argument I make AGAINST cdesign proponents, in fact. In evolution we have the appearance of goals, but not actual ones. If that’s enough to deem it a process, I concede on that point.

       5. @The Math Skeptic,

          On the appearance of goals, another said. But does the gamete know the end result at the beginning?

          A Zygote is a Gamete’s Way of Producing More Gametes. — Lazarus Long, from Robert A. Heinlein’s “Time Enough For Love…”

          Mary

    4. More detailed, biologists are inclusive on theory (evolution) while physicists are rather more, but not purely, exclusive (gravitation).

       The modern synthesis replaced “variation+selection”, and more mechanisms such as near neutral theory and evo-devo has been included since.

13. I accept that general relativity defines the concept that gravity is a phenomenon of spacetime geometry. So why are particle physicists talking about the graviton as if there was a need for a particle to transmit the gravitational force? Or am I just barking up the wrong apple tree!

    1. Yes, this is a fundamental schism between GR and quantum physics – quantum physics defines gravity as a force, GR doesn’t.

       Quantum physics works great at the sub-atomic level, but can’t quite manage large scale cosmology. GR can’t quite manage the sub-atomic level.

    2. They are 2 different models of the same thing. Models are never perfect.
       It is like 3 different maps of your city. You can have metro map and you can have a road map. They are both simplifications of reality.

       1. Ha! Good analogy. I have to remember it! 🙂

       2. If both relativity and quantumphysics are simplifying reality, then reality must be rather complex

    3. Though if eternal inflation is correct, inflation can “manage” the latter. (But not by accommodating particles.) So that stretches the comfort zone of these cosmology relevant theories.

       1. The slow roll inflationary model is the “standard model.” The scalar potential might be compared to a slow slope with a half-pipe at one point for skate boarding. The slow roll is the inflationary period and the half-pipe is where reheating occurs. The eternal inflation is an asymmetrical quartic potential with two minima at different energy. The process involves tunneling through the quadratic peak and falling into the deeper potential pit. This involves a tunneling of a pocket universe out from beneath the Planck scale of length. The problem here though is that the Planck scale as probed by looking at the dispersion of photons from distant sources appears to have no fluctuation physics. This presents problems for eternal inflation.

          LC

       2. [Warning: concept packed comment ahead! (I am sleepy.)]

          I’m sure there are several eternal inflation mechanisms. The generic mechanism of Linde has fluctuations kicking the inflation field up. The requirement is very weak, an unbounded potential.

          There is no requirement for specific potentials or tunneling.

          However, if there is tunneling I don’t see how that is a problem. The common interpretation is that it uses Heisenberg uncertainty. So do fluctuations. However, they are not the same process.

          Conversely, if absence of fluctuations would be a problem for predictivity (such as it is) of inflation at planck scales, a similarly smooth gravity at planck scales of black hole physics would have a problem. But black holes exist.

          Btw, what is the connection between fluctuations of todays relaxed spacetime to do with fluctuations of inflation potential? Even if the inflation potential would still be discernible after spacetime emerges, it would be very weak and not at planck energies, wouldn’t it?

          As context: I think it is a stretch to connect particle field fluctuations, which are known to exist (static and dynamic Casimir effect), over semiclassical worldlines of generic inflation to fluctuations of spacetime.

          Somewhere fluctuations seem to disappear from the background. But since spacetime is emergent and worldlines a feature of particle physics I expect inflation could have fluctuations. [This isn’t what I thought yesterday in another thread. You live a little, you think a little.]

          The immediate problem for eternal inflation is IMO that the simplest such models are started to be excluded. Ironically, Planck may kill the idea before observation and theory of planck scales do.

       3. The eternal inflation potential is more natural in some sense than the standard model inflation potential. The slow roll with a quadratic potential “pit” is somewhat “jacked up.” The eternal inflaton potential is an asymmetric quartic potential which is nicely in line with the Coleman nucleation bubble physics. However, the absence of spacetime fluctuations as measured by FERMI and INTEGRAL put these models under pretty strong question.

          The Casimir effect is measured for quantum electrodynamics. The virtual modes of the photon vacuum are restricted to half integer values between two metal plates, whilst outside the modes are a continuum. This means there is a difference in the energy density of the vacuum between the plates, or this is how we interpret this. The Lamb shift is another vacuum energy effect. The quantum field theory (QFT) of this works pretty darn well. However, it begins to hit trouble with the vacuum energy density expected with the standard model. The vacuum energy density should be quite large, on the order of 174GeV^4, which is tied to the Higgs field. This resulted in problems with the cosmological constant early on, where QFT predicted a universe with a much larger vacuum energy density than what our observed universe could be derived from. The accelerated expansion of the universe and so called dark energy put further problems on this idea of the vacuum. Now the LHC is placing exclusion on the Higgs particle, which means we are likely faced with a crisis in our understanding of the vacuum structure of the universe.

          The problem as I see it is that we have been packing all sorts of degrees of freedom into the vacuum. This is analogous to the aether problem of the 19th century, where to understand how an EM wave propagated in space there was imposed some continuous fluid-like field. If this was composed of particles of some sort, partons on atomicules, the number of degrees of freedom was enormous, and was infinite in the continuous limit. Einstein replaced all of this nonsense with a system of symmetries, 3 rotations and 3 boosts. I pretty strongly think that something like this is waiting in the wings.

          LC

       4. Well, some scientists are going to look for such “Planck-scale-effects induced” changes to radiation from distant sources, but that’s to try to prove if the universe’s space is really 3D or just 2D with a “projected” 3rd dimension (due to time getting “tangled up” with the other two).
          I read that on Ars Technica.

14. If we consider about the point of view, as the inhabitant of earth we are able to see the real space object of far distance space within the radius of 150 million kilometers only and next our eyes meet space mirror. For more facts you may visit space mirror mystery website.

    1. Your personal theory of vast distances being illusions and illustrations within some mirror are just that, personal. Please STOP posting your garbage anywhere, period.

       Mary

       1. He keeps creating new accounts and posting; must be resetting his IP too.

    2. Mirror, mirror up in space, who has the dumbest personal ‘theory’ in this place?

       1. The Mystery Mirror Man with multiple accounts and IP addresses.

       2. … I hope it reflects the original comment. Because it looks silly. (o.O)

       3. You mean like THIS? 😉

          But yes, it does reflect the original comment.

       4. … I hope it reflects the original comment. Because it looks silly. (o.O)

    3. That would explain why Andromeda’s always complaining that it looks fat. It’s because of the curved mirror adding .5 trillion solar masses.

       1. Curved mirrors = relatively fat?

       2. Curved mirrors = relatively fat?

15. I recall having read often sentences like “the photons entering our telescopes have been travelling through space for millions of years … “.
    Now, the article points out that neither time nor distance exist from the point of view of any photon. This means that if you travel at the speed of light, you will experience that neither time nor distance do exist for you any more, and this will also apply for the systems of your spaceship. At the speed of light, you are litterally everywhere in the universe at the same moment. You won´t be able to reach a desired destination this way, as it is evident that the concept of destination and time fails for everything travelling at the speed of light.

16. To further elucidate Urbanyeti and Steve Nerlich’s comments, and add something important to the discussion: an astronaut in a spaceship falling toward a planet would not feel a sense of acceleration because both he and the spaceship are accelerating at the same rate (i.e. in free-fall). However, the astronaut would see the planet approaching at an increasing rate and thereby infer a gravitational field. Firing the spaceship’s forward thrusters would further accelerate the vessel but not the astronaut. The interior of the spaceship would contact the astronaut, at which point he would feel “pushed” back into his seat. At this point, energy is imparted to the astronaut, who would then feel he is accelerating at the same rate as his spaceship. That sense of acceleration persists until the thrusters are cut, at which point both the astronaut and spaceship are once again in free-fall.

17. To further elucidate Urbanyeti and Steve Nerlich’s comments, and add something important to the discussion: an astronaut in a spaceship falling toward a planet would not feel a sense of acceleration because both he and the spaceship are accelerating at the same rate (i.e. in free-fall). However, the astronaut would see the planet approaching at an increasing rate and thereby infer a gravitational field. Firing the spaceship’s forward thrusters would further accelerate the vessel but not the astronaut. The interior of the spaceship would contact the astronaut, at which point he would feel “pushed” back into his seat. At this point, energy is imparted to the astronaut, who would then feel he is accelerating at the same rate as his spaceship. That sense of acceleration persists until the thrusters are cut, at which point both the astronaut and spaceship are once again in free-fall.

18. To further elucidate Urbanyeti and Steve Nerlich’s comments, and add something important to the discussion: an astronaut in a spaceship falling toward a planet would not feel a sense of acceleration because both he and the spaceship are accelerating at the same rate (i.e. in free-fall). However, the astronaut would see the planet approaching at an increasing rate and thereby infer a gravitational field. Firing the spaceship’s forward thrusters would further accelerate the vessel but not the astronaut. The interior of the spaceship would contact the astronaut, at which point he would feel “pushed” back into his seat. At this point, energy is imparted to the astronaut, who would then feel he is accelerating at the same rate as his spaceship. That sense of acceleration persists until the thrusters are cut, at which point both the astronaut and spaceship are once again in free-fall.

    1. Yup, as far as I can tell, any explanation of gravity where *all* mass that are accelerated equally (like how the astronout and his ship is accelerated equally) would work just fine. So then the question becomes: what cause the acceleration? The energy has to come from somewhere.
       Particles like the graviton? Or is it NOT acceleration, is there really a space-time that is bent?
       And also, if it’s particles – what’s up with all these relativistic effects like time dilation and spaghettification? And if it’s a bent spacetime, what’s up with orbits around spheres like Earth, how can that be a straight line (according to relativity theory)? By that I means as in if you approach earth from a certain angle from ANY direction, your “straight line” will “converge” with the “orbit line” (you will end up in orbit, from our point of view a circle but a straight line according to relativity theory).

       Etc…

       Physics gets really weird as soon as we go beyond Newtonian physics,

       1. What energy? Permanent magnets accelerate iron without it needing to be a permanent loss of magnetic energy. It is a temporary loss of magnetic field potential, which may be concurrent with a gain in gravitic field potential. (In the simpler newtonian picture.)

          Gravitons are only needed if the field is radiating energy elsewhere, not if it is a local field effect.

       2. Quantum entanglement. Now that’s by far much worse than gravity if you hate “spooky action at distance”.

       3. Maybe gravity and quantum entanglement are equivalent. The universe we observe exists on the boundary of an anti de Sitter (AdS) spacetime. Quantum fields not attached to the boundary are repelled by this boundary into the interior. They follow great arcs as geodesic paths and return to the boundary. This hyperbolic dynamics or arcs can be seen in the tessellation art of Escher in his Circle Limit drawings. If you place a black hole in the AdS the holographic principle is such that the quantum information on the black hole is equivalent to that on the AdS boundary. That is a bit hand wavy for the argument is rather difficult to go through. The quantum information of the system is equivalent to various n-partite entanglement SLOCC groups. Again this is tough to go through, but the moduli space for BPS and extremal black holes are groups with an isomorphism to entanglement groups. Duff, Borsten, Dahanayke, Rubens and others have worked to demonstrate this using the Kostant-Sekeguchi theorem. So the holographic principle of qubit equivalency extends to AdS spacetimes and their boundary.

          The boundary of the AdS is a conformally flat spacetime, which can be a de Sitter spacetime. A de Sitter spacetime is a time dependent conformal spacetime, which gets into some math-thumping to go into, but this spacetime is what obtains in inflationary conditions and with the current accelerated expansion. However, the occurrence of mass breaks conformal invariance and this generates little defects which are “probes” into the AdS interior. This is a source of local gravity. The occurrence of this gravity is then the result of this entanglement structure.

          LC

       4. Uhm… That’s a bit… over my head… 😉

       5. @Natanael L,

          Mine as well, but I have confidence the bottom of the pool is down there somewhere since I am heading for it fast.

          Head in the clouds, feet in the swamps.

          Mary

       6. @Natanael L,

          Mine as well, but I have confidence the bottom of the pool is down there somewhere since I am heading for it fast.

          Head in the clouds, feet in the swamps.

          Mary

       7. There is a certain Stoic quality to this. Thinking about these things keeps my mind off the anthro-sphere and its current disintegration. We seem to be in a lot of trouble. A spacecraft is on its way to Jupiter. There are two possible questions. The first is whether the craft will make it. The next question is whether there will be anyone here to receive the data it sends if it gets there.

          LC

       8. My immediate concerns are starting to trump my mid-term/long-term concerns about the environment.

          I’ve just been laid-off again, the fourth time since this Great Contraction began in ’09. Being very young with limited experience, I’m beginning to appreciate the hardships others of my generation are going through.

          I’m worried about the economy. Particularly, I’m concerned about the long term trend of rising inequality. I don’t understand why this issue isn’t receiving more attention. It seems to me, if this trend towards a Plutocracy continues, we might be in for serious social unrest; much of it likely triggered by members of my generation. May of my friends honestly feel they have nothing to lose anymore; they have no stake in social order.

          Events in Spain, Greece, and Britain might be early warning signs of things to come. The media largely portrays events in Britain as largely opportunistic, spontaneous thuggery and thievery. This may very well be an accurate description, however, it smacks of a reactionary, simplistic response that skims over mounting social/economic tensions.

          I’m worried this tide of street anger may break on the shores of North America in the coming years. I would rather not be painted with the same brush as other riotous youth. However, part of me sympathizes with the idea of street protests. Taking to the streets en masse might be the only way to force those in power to see their best interests aren’t served by stealing the pot while leaving the ship to flounder.

       9. The first thing that has to recognized is that the system is broken. This recent debt limit flapdoodle was really a hijacking of the nation in order to demolish Obama’s Presidency. This was the latest in the program of lynching a black guy who became President, where the same guys railed about his birth certificate. That was all a way of saying “He is not one of us.” Further, all of the money which went into bailing out the financial industry was a way of propping up the elites, and the rest of us are left out on our own. In this debt ceiling debate any mention of increasing the taxes on the top incomes was shelved. To the extent there is a major problem it is largely due to the fact GW Bush increased war spending and chopped the tax rates for the top. It does not take much to see that our system has become a plutocracy. The Democrats and Obama are not terribly effective, and frankly for the most part serve to increase the financial power of those at the top; just not to the full extend the Republicans want..

          There is not going to be a job recovery. Of course people of progressive mind are going to vote for Democrats, or liberal parties in other countries (note the horror of the Cameron Downing Street in the UK), and be then disappointed to see their elected officials move to the center right. What else should we expect? Why in the hell do we continue to believe that the system is ever going to respond to what the majority mandates, when that majority is not just parroting an astro-turf agenda? This is not to say we should abandon voting, or even campaigning, but we should do this more with the idea of preventing the most sociopathic from achieving high office.

          There is only one possible general path out of this nightmare. This does not involve mass protests and the like. The power structure has learned how to weather those, and of late they really have not been effective. The only way out is for people to begin to work out alternatives in their local setting. This might just start by planting a garden in the back yard. This might graduate to community gardens, then setting up neighborhood co-ops, then starting to set aside days where people work to refurbish houses and neighborhood buildings — don’t rely on elected officials to finance “infrastructure,” they wont, never will. This can extend to other things such as cloth and clothes making, woodworking, shoe making, mechanics (cars, appliances, heating etc) alternative energy and other practical crafts. People need to start baby stepping in these directions, where if nothing else a backyard garden can reduce the trips to Wall*Mart and the food power they have over you.

          As the global corporate system sloughs more people off its rolls more people may come to join the alternative economy. There is no ideological principle which is established here, and people work things out on a local “as needed” basis. If this can get going then by the mid 21st century when the energy supplies drop off, events have demolished so much of our current world and the super-elite have retreated to their Versailles palaces (Galt’s Gulch, in the Ayn Rand parlance) the balance will shift to where most people are living in a way less dependent upon them. Eventually industrial and advanced technology will become integrated into this alternative system. As time goes on, maybe this will become integrated into a more coherent national or world system. The elites will find they no longer have the mindless robots (labor) around to support them, and all their economic theory does little to tell them how to make high-tech robots. They are eventually relegated to irrelevance.

          This is a sort of Hari Seldon plan, where under the feet of people running the world a new system is integrated together. Hari Sheldon was the fictional character in Isaac Asimov’s “Foundation and Empire” series who proposed some alternative to the Empire.

          At this time I simply do not see any other possible path out of the nightmare. The alternative is to plunge further in these directions and to eventually become Soylent Green, if not literally certainly at least figuratively.

          LC

       10. There is a certain Stoic quality to this. Thinking about these things keeps my mind off the anthro-sphere and its current disintegration. We seem to be in a lot of trouble. A spacecraft is on its way to Jupiter. There are two possible questions. The first is whether the craft will make it. The next question is whether there will be anyone here to receive the data it sends if it gets there.

           LC

       11. What energy? Permanent magnets accelerate iron without it needing to be a permanent loss of magnetic energy. It is a temporary loss of magnetic field potential, which may be concurrent with a gain in gravitic field potential. (In the simpler newtonian picture.)

           Gravitons are only needed if the field is radiating energy elsewhere, not if it is a local field effect.

       12. According to general relativity, gravitational acceleration is not caused by a force, and as T. Larsson points out, no energy is required. What we perceive as gravity is really due to the geometry of spacetime. Orbiting objects in a “gravitational field” follow geodesic paths (the shortest path between two points). From the perspective of 4-D spacetime, the object follows a geodesic line, constantly falling toward a planet. From our perspective, in which 3-D space and 1-D time are separate, we see the object orbiting around the planet. If you suddenly stop the space shuttle from orbiting it will no longer accelerate around the Earth, it will accelerate straight toward it. In either circumstance, it follows the shortest path available to it. No energy, no force required.

       13. But if no force are required, why does two heavy objects that both stand still start to move against eachother?
           And if they aren’t “accelerating” and it’s just spacetime that is getting smaller, what’s up with the heat and all that’s being generated on impact?

    2. Yup, as far as I can tell, any explanation of gravity where *all* mass that are accelerated equally (like how the astronout and his ship is accelerated equally) would work just fine. So then the question becomes: what cause the acceleration? The energy has to come from somewhere.
       Particles like the graviton? Or is it NOT acceleration, is there really a space-time that is bent?
       And also, if it’s particles – what’s up with all these relativistic effects like time dilation and spaghettification? And if it’s a bent spacetime, what’s up with orbits around spheres like Earth, how can that be a straight line (according to relativity theory)? By that I means as in if you approach earth from a certain angle from ANY direction, your “straight line” will “converge” with the “orbit line” (you will end up in orbit, from our point of view a circle but a straight line according to relativity theory).

       Etc…

       Physics gets really weird as soon as we go beyond Newtonian physics,

19. “Gravity is not real, it’s just our dumbed-down interpretation of space-time curvature.”

    Ah, yes, very interesting. When you jump out of the window of the, say, 5th floor of a building, the “interpretation” will not hurt you, I assume. And pain is an illusion. Come on!

    1. In this case the problem is not with the curvature of spacetime but with electromagnetic forces and electron degeneracy. 😉

20. “Gravity is not real, it’s just our dumbed-down interpretation of space-time curvature.”

    Ah, yes, very interesting. When you jump out of the window of the, say, 5th floor of a building, the “interpretation” will not hurt you, I assume. And pain is an illusion. Come on!

21. “Gravity is not real, it’s just our dumbed-down interpretation of space-time curvature.”

    Ah, yes, very interesting. When you jump out of the window of the, say, 5th floor of a building, the “interpretation” will not hurt you, I assume. And pain is an illusion. Come on!

22. Starlight

    Relativity saves the day, as usual. 😉

    Credit: xkcd.com

    1. general rant–

       I like xkcd of course, who wouldn’t, but…

       The photon does not ‘die’ so we can see some pretty dots. The photon combines with material we have within our eyes and in doing so becomes a part of us for the duration as it were.

       Mary

23. I think you misunderstand how the evolution-gravity analogy is used.

    The analogy makes no comparison between the facts of the theories as you describe, but uses the theory status itself as the basis of the argument.

    When an evolution doubter uses the argument “well evolution is just a theory”, the sceptic gets to smile and point out that “so is gravity, but you don’t doubt gravity’s existence based purely on its theory status”.

    1. I doubt gravity’s existence based purely on its theoretical status.

       I need a ‘that’s the whole point of the article’ button.

    2. I’m not sure what you’re getting uptight about, I wasn’t criticising the article, just saying that in my experience “science advocates and skeptics” don’t say anything like what you suggested. That fact still stands.

    3. Gravity is a law. A law in scientific terms is basically an indisputable, automatically experienced and conceivable concept. Drop something and it falls. Hit something and it breaks in proportion to amount of energy in the force of the hit, etc… Laws are at the ‘beginning’ of the scientific method. They are the building blocks of theories. Theories are ideas (hypotheses) that use a set of laws, arranged in a certain way that can imaginably, when set in motion, achieve a predictable outcome; like a series of lined dominoes knocked over that perform various physical actions such as triggering a series of flags to pop up when a catch is released by a domino hit and so on… Laws are universal and unchanging… theories can always be tweaked and refined to describe these sequences of events in more detail.

       1. Gravity is both a law and a theory; the theory of gravity encompases the laws of gravitation. It is to the theory of gravity we refer when countering the evolution is just a theory argument.

          The theory of gravity contains many aspects which can be tweaked and refined, just as the theory of evolution contains many aspects which can be tweaked and refined. Incidentally, a scientific hypothesis is not the same as a scientific theory.

          But regardless of the specifics, this is not the point that I was making, which was that the evolution-gravity analogy is not used by sceptics and science advocates in the way that the article suggests.

          For the curious, you can read about the difference between laws, theories, hypotheses at http://wilstar.com/theories.htm and find out more about the evolution-gravity analogy at http://en.wikipedia.org/wiki/Evolution_as_theory_and_fact#Evolution_compared_with_gravity

       2. @Jeffrey Scott Boerst,

          I like your way of telling the story. I also like the laws described in I Think We’re All on this Bus, the section on the wall of science. “Push Something Hard Enough And It Will Fall Over.” — Fudd’s First Law of Opposition as well there is “What Goes In, Must Come Out.” — Teslacle’s Deviant to Fudd’s First Law.

          But seriously folks, I’m here all week, don’t forget to tip your wait staff.

          Mary

24. 50 + comments! What have you wrought, Nerlich?

    To take lcrowell’s and Colin Kline’s start and run with it, special relativity permits a perhaps nice POV model of the quantum field. Or I like to think so:

    It is my understanding (disclaimer: no quantum field studies) that if you start with the classical mechanics particle, you go over the classical electromagnetic field picture of Maxwell, to end in the quantum field as a global special relativity property of local particle interactions.

    The photon is the classical field’s way of propagating energy in a Poynting energy flow as radiation. That gives the broad-lobe 1/r2 radiation behavior of EM fields, which supplements the 1/r2 static behavior of infinite range fields from Gauss’s law.

    Since the quantum field is neither particle nor field but a particle field, you can as momentarily forget the photon existence between creation and extinction and see it as a field property of the field.

    Please note that this is not physically accurate _at all_ since it is radiation that propagates, not the field. But it gives a facile (“easifying”?) analogy of the photon as “emitted and then instantaneously reabsorbed”.

    @ Nerlich:

    Science advocates and skeptics say that we should accept the reality of evolution in the same way that we accept the reality of gravity – but actually this is a terrible analogy. Gravity is not real, it’s just our dumbed-down interpretation of space-time curvature.

    It is a good analogy. It is used to reflect the difference between fact, such as existence of gravity, and theory, such as different theories of gravity.

    One use is the one morphics mention. Another is to relate observing evolution between species (populations) as fact with a simple observation of falling things as fact. Then I use to go on to illustrate evolution as the simplified “variance+selection” instead of the modern synthesis, in the same way that you use newtonian gravity instead of general relativity at times.

    I believe you mean it is a terrible description of gravity. But that is not the purpose of the analogy, at all.

    And as always, analogies are faulty but useful illustrations of principles, not precise equivalences. There is no need to protect the beauty of gravity; it stands on its own. (But there is plenty of need to protect the beauty of evolution, for that matter.)

25. If a photon emitted from one of the first stars is observed by a human having travelled for 13 billion years and has changed position, wavelength etc but occurs instantaneously from the photons point of view, does this mean that information is created instantaneously?

    1. @NoviceGaz,

       You ask an interesting question from the point of view of the photon.

       The answer seems to be (from the point of view of the photon) that the non-distance is crossed in no-time.

       A few more thoughts though, since your question is stirring the waters of my magic 8 ball.

       The no distance/no time is also expected to be filled with the accelerated expansion of the space-time which further begs this question -does the photon experience any of the effects of the expansion and the acceleration of that expansion.

       Does the photon actually carry any information, any data, which relates to the trip it has been on for all those years?

       Implied herein is, some data is carried by the photon, more than just what we measure at our end; duration is not an experience that is carried individually by any one photon though.

       There seems to be only a few thing a photon ‘knows’; duration and distance are not among the select few it would seem. The frequency and the energy density are the only two items a photon knows to our measure, if memory serves me well today. Now any group of photons can be tracked via statistical analyses of various types for various purposes.

       The data we extract from those equations may be data which is commonly carried by each, subjected to the whole we have measured, but we would never be able to assign any spec of that to any point of that mass of photons. The group is not quite the whole though, when single photons are measured, this also means the way that measurement takes place, the method, has some impact on that single photon when taken from the whole, or from the group.

       Duration is part of the travel of the photon which it does not experience, hence no tired light, if you would. Our measurements imply that duration has passed, and how the photon has arrived at our ‘door’, the path it has taken. We can’t inform the photon though, it has no place to carry that datum set. It has no ticket for our conductor to punch.

       Distance (already expanded, or that which will be expanding faster) is another thing the photon is unaware of being crossed, hence no foot weary light, if you would. The change which does occur to the photon’s frequency due to the expansion does not impress itself as any change in state, nor as any remembered state in fact, that we can tell. Any changes of state at our end seem to be some part of the original state to the photon, and to us, of course. We assign the most probable cause for that change state, indeed that a state is in change at some point along the path taken is one of many assumptions our theories grant. There are no stations, no crossings, no milk train travels for the photon because if it had a ticket that ticket would be for the express train.

       We conclude these facts from our measurements and those math laden theories freshmen learn to ‘love’.

       We test them and test them, these theories, and it seems the theories hew to, cleave to the line we have traced. When something new comes along, and it does, never fear, it too is added or subtracted and included in out tests.

       The abilities, the nature, of any photon which completes the trip from there to here, wherever there is, is implicit within our grasp of that photon. We can’t measure what we do not ‘see’ as it were.

       This has been fun, try another question, says the magic 8 ball.

       Mary

    2. Very interesting question.

       “Information” is relative a system. Here, photons can be used to encode messages, but it is known that the information is not in the single photon (phase velocity) but in a bunch of them (group velocity). In many situations it is the wave front that encodes the information.

       Stretching light means it will tell you of cosmological redshift. But only if you have several photons, so you can see that in a spectra of stars (absorption or emission lines) or CMB (black body temperature).

       In other words, a single photon doesn’t encode (“experience”) the fact that it has been stretched. That reflects the fact I noted above, that information is relative systems, here the whole physics of spectra vs redshift.

    3. The information is created the moment the photon is emitted – i.e. instantaneously. As far as the photon is concerned that is the end of the story. For us subluminal beings it persists and travels for as long (in both time and distance terms) as is required for the particular circumstances of our observation frame of reference.

       An interesting comparison is quantum entanglement – where information is allegedly transmitted instantaneously regardless of the space-time separating the two entangled particles (hence Einstein’s comment that this represents ‘spooky action at a distance’).

26. Mr. Nerlich’s piece opens-up a fascinating space-time corridor of thought-entry doors:

    Just one that may lie beyond the vanishing point. Read something some while ago, that made me realize that absolutely nothing in “space” is motionless: Earth rotates on its axis, revolves around Sun ( in Moon dance ); the Sun, in turn, moves in its stellar neighborhood.

    Journey farther out from that insignificant local star group, and a larger constellation of groupings comes into perspective, a diverse star field suspended between(?) two huge spiral Arms: Our relatively small local star assembly, itself flowing along with the even bigger regional celestial mass. These scaled-up motions adding-to that of the aforementioned.

    Then, in the realm of the incomprehensibly gigantic, the entire Island Universe of our galactic home, with its vast rotational, Spiral movement. And that, within the even greater swarming motions of the whole “Local Group” of gravitationally related Galaxies. ( Can anyone fallow the curvature of space through all this? )

    Venturing beyond its familiar collective light, we set off into the colossal, fathomless scales of night: Entering the dominion of giants — Galaxy Clusters and Super-Clusters: whole “walls”, “sheets” and “filaments” of galaxies.

    On each quantum leap of scale, one-set of time differentials fades before a larger, enclosing array of space-time measures ( million-year galaxy turn, for example ). And in that journey through these increasingly wide time chambers of space, you have all the compounding, accumulated motions ( if I even grasp the edge of these awesome things ).

    So how fast the Earth, or anything is actually moving ( or anything related thereto ) — in reference-frame of the entire Universe — may be any body’s guess. What is the ultimate point of determination? Is it all, indeed, relative? How superimposed time-layering figures-in, is light years beyond my ken.

    Complex Clockwork assembly came to mind: Motions within motions, times within times. Wheel and gear differentials,
    concentric time cycles: A second turn, a minute spin, an hour revolution — and a billion-year twirl of a Super Cluster Filament!

    Just one, non-technical door of thought that may go nowhere ( did I hear it close behind me? )

27. Problem: translocating the particles/information p that constitute me (or you) to places outside of Earth takes t = too damn long. Solution = nowhere in what we know so far. Suggestion:stop being so smug about it and look again.

    1. We are! It just takes time…

28. As Steve Nerlich points out, when considering a photon’s point of view, the distance it travels and time elapsed are zero: This is a consequence of special relativity. As far as the photon is concerned, the universe is a timeless, spaceless point. This underscores the basic dichotomy between classical and quantum physics. From a quantum point of view, effects like tunnelling, entanglement, and the superposition of states supersede space and time. The photon and the information it bears are “everywhere at once.” However, from our “classical” point of view, space and time do exist. The photon travels 13 billion light-years and takes all that time to deliver its information. So which POV “rules?” According to Steven Hawking and others, it may be that the quantum point of view is fundamental while the “classical” view is secondary: Space and time might ultimately emerge from the decoherence (wave-function collapse) of quantum states. (See Scientific American – June 2011.)

29. As Steve Nerlich points out, when considering a photon’s point of view, the distance it travels and time elapsed are zero: This is a consequence of special relativity. As far as the photon is concerned, the universe is a timeless, spaceless point. This underscores the basic dichotomy between classical and quantum physics. From a quantum point of view, effects like tunnelling, entanglement, and the superposition of states supersede space and time. The photon and the information it bears are “everywhere at once.” However, from our “classical” point of view, space and time do exist. The photon travels 13 billion light-years and takes all that time to deliver its information. So which POV “rules?” According to Steven Hawking and others, it may be that the quantum point of view is fundamental while the “classical” view is secondary: Space and time might ultimately emerge from the decoherence (wave-function collapse) of quantum states. (See Scientific American – June 2011.)

30. Some of the right idea is here, but you need a sign difference between the spatial parts and the (ct)^2 part. This makes the metric pseudo-Euclidean or Lorentzian. With a strictly Euclidean metric there is no situation where ds = 0 without the elements dt = dx = … = 0.

    LC

31. Wow, I didn’t know that there’s no space for a photon.

    >It’s just that they fail to acknowledge their particular context of having evolved on the surface of a massive object, where space-time is all scrunched up.

    Our deficiency at perceiving the 4th dimension (and therefore making wrong assumptions) is maybe more because we can’t move in it at free will, not because it is scrunched up.
    It would make sense for our brain to compute in 4D spacetime if it could alter our speed in time, but in 3D it is more convenient to compute with apparent forces and a constant time.

32. BS

33. You do mean Basic Science, right Tim?

    Mary

Comments are closed.