Notices
Results 1 to 37 of 37

Thread: Unobservable Universe Will Come Into View (eventually)

  1. #1 Unobservable Universe Will Come Into View (eventually) 
    Time Lord zinjanthropos's Avatar
    Join Date
    Dec 2005
    Location
    Driving in my car
    Posts
    5,751
    Well a good chunk anyways, but it will take time according to this article:

    https://www.forbes.com/sites/startsw...h=2bb67b7ff827

    Excerpt:
    The expansion rate began large, but has been decreasing as the Universe expands. There's a simple reason for this: as the Universe expands, its volume increases, and therefore the energy density goes down. As the density drops, so does the expansion rate. Light that was once too far away from us to be seen can now catch up to us.
    This fact carries with it a huge implication for the Universe: over time, galaxies that were once too distant to be revealed to us will spontaneously come into view. It may have been 13.8 billion years since the Big Bang occurred, but with the expansion of the Universe, there are objects as far away as 46.1 billion light-years whose light is just reaching us.
    I always thought once galaxies disappeared from view during expansion >C that they'd be gone forever. I doubt humanity will be around to see galaxies reappear but it does sound like the universe has a lot of time ahead for itself. Some huge numbers in the trillions re un/observable galaxies.

    Makes me wonder about current age of the universe and whether it's still just a baby. I guess I should have entitled thread as unobservable coming back into view. IOW's won't be the first time they could've been observed from our vantage point.


    All that belongs to human understanding, in this deep ignorance and obscurity, is to be skeptical, or at least cautious; and not to admit of any hypothesis, whatsoever; much less, of any which is supported by no appearance of probability...Hume
    Reply With Quote  
     

  2.  
     

  3. #2  
    Forum Freshman
    Join Date
    Feb 2012
    Location
    Upstate NY
    Posts
    84
    Quote Originally Posted by zinjanthropos View Post
    The expansion rate began large, but has been decreasing as the Universe expands.

    This is incorrect, the expansion rate is now increasing. So over time more far away galaxies will idea from sight.


    Reply With Quote  
     

  4. #3  
    Time Lord zinjanthropos's Avatar
    Join Date
    Dec 2005
    Location
    Driving in my car
    Posts
    5,751
    Quote Originally Posted by Origin View Post
    Quote Originally Posted by zinjanthropos View Post
    The expansion rate began large, but has been decreasing as the Universe expands.

    This is incorrect, the expansion rate is now increasing. So over time more far away galaxies will idea from sight.
    That’s why I’m posting. Has something happened to change physicists’ thinking?
    All that belongs to human understanding, in this deep ignorance and obscurity, is to be skeptical, or at least cautious; and not to admit of any hypothesis, whatsoever; much less, of any which is supported by no appearance of probability...Hume
    Reply With Quote  
     

  5. #4  
    Forum Freshman
    Join Date
    Feb 2012
    Location
    Upstate NY
    Posts
    84
    Quote Originally Posted by zinjanthropos View Post
    Quote Originally Posted by Origin View Post
    Quote Originally Posted by zinjanthropos View Post
    The expansion rate began large, but has been decreasing as the Universe expands.

    This is incorrect, the expansion rate is now increasing. So over time more far away galaxies will idea from sight.
    That’s why I’m posting. Has something happened to change physicists’ thinking?
    Nope.
    Reply With Quote  
     

  6. #5  
    Forum Radioactive Isotope
    Join Date
    Feb 2009
    Posts
    4,941
    I think acceleration can decrease without distance between galaxies decreasing over time.

    Distances can still increase even if acceleration decreases over time.
    Reply With Quote  
     

  7. #6  
    Forum Freshman
    Join Date
    Feb 2012
    Location
    Upstate NY
    Posts
    84
    Quote Originally Posted by geordief View Post
    I think acceleration can decrease without distance between galaxies decreasing over time.

    Distances can still increase even if acceleration decreases over time.
    That is correct. However, the distances between the galaxies is increasing at an increasing rate according to observation.
    Reply With Quote  
     

  8. #7  
    KJW
    KJW is offline
    Forum Professor
    Join Date
    Jun 2013
    Posts
    1,691
    Quote Originally Posted by Origin View Post
    Quote Originally Posted by zinjanthropos View Post
    That’s why I’m posting. Has something happened to change physicists’ thinking?
    Nope.
    This is incorrect. Accelerated expansion of the universe was discovered in 1998. Prior to that, the expansion of the universe was assumed to be decelerating due to the gravitational attraction of the matter in the universe.
    There are no paradoxes in relativity, just people's misunderstandings of it.
    Reply With Quote  
     

  9. #8  
    Forum Radioactive Isotope
    Join Date
    Feb 2009
    Posts
    4,941
    Quote Originally Posted by Origin View Post
    Quote Originally Posted by geordief View Post
    I think acceleration can decrease without distance between galaxies decreasing over time.

    Distances can still increase even if acceleration decreases over time.
    That is correct. However, the distances between the galaxies is increasing at an increasing rate according to observation.
    I am sure you are correct.I didn't go through the article in question very thoroughly but it seemed to be suggesting that parts of the universe presently unobservable (because of expansionary recession at a speed greater than that of light) might ,in the course of billions of years become observable again.

    I wonder what possible mechanism might lead to that effect?
    Reply With Quote  
     

  10. #9  
    Forum Freshman
    Join Date
    Feb 2012
    Location
    Upstate NY
    Posts
    84
    Quote Originally Posted by KJW View Post
    Quote Originally Posted by Origin View Post
    Quote Originally Posted by zinjanthropos View Post
    That’s why I’m posting. Has something happened to change physicists’ thinking?
    Nope.
    This is incorrect. Accelerated expansion of the universe was discovered in 1998. Prior to that, the expansion of the universe was assumed to be decelerating due to the gravitational attraction of the matter in the universe.
    Huh? I was not addressing the history of the discovery. I was only pointing out that the article cited was incorrect that the rate of expansion was slowing down.
    Reply With Quote  
     

  11. #10  
    KJW
    KJW is offline
    Forum Professor
    Join Date
    Jun 2013
    Posts
    1,691
    Quote Originally Posted by Origin View Post
    Quote Originally Posted by KJW View Post
    Quote Originally Posted by Origin View Post
    Quote Originally Posted by zinjanthropos View Post
    That’s why I’m posting. Has something happened to change physicists’ thinking?
    Nope.
    This is incorrect. Accelerated expansion of the universe was discovered in 1998. Prior to that, the expansion of the universe was assumed to be decelerating due to the gravitational attraction of the matter in the universe.
    Huh? I was not addressing the history of the discovery. I was only pointing out that the article cited was incorrect that the rate of expansion was slowing down.
    Oh ok. It seemed to me (based on your reply to zinjanthropos) that you thought physicists have always thought the expansion of the universe is accelerating.
    There are no paradoxes in relativity, just people's misunderstandings of it.
    Reply With Quote  
     

  12. #11  
    Forum Freshman
    Join Date
    Feb 2012
    Location
    Upstate NY
    Posts
    84
    Quote Originally Posted by KJW View Post
    Oh ok. It seemed to me (based on your reply to zinjanthropos) that you thought physicists have always thought the expansion of the universe is accelerating.
    OK.
    Reply With Quote  
     

  13. #12  
    Time Lord zinjanthropos's Avatar
    Join Date
    Dec 2005
    Location
    Driving in my car
    Posts
    5,751
    Light travels along the geodesic, the curvature of space time I think. In physics is there a word for the distance between two objects if you shortcut the geodesic? I’ll call it the tunnelling distance, a straight line between the ends of an arc segment. As the universe expands does the geodesic distance expand at a greater rate than the tunnelling distance or does it even occur at all? Maybe you guys can clear up a misconception of mine.
    Last edited by zinjanthropos; December 19th, 2020 at 03:27 PM.
    All that belongs to human understanding, in this deep ignorance and obscurity, is to be skeptical, or at least cautious; and not to admit of any hypothesis, whatsoever; much less, of any which is supported by no appearance of probability...Hume
    Reply With Quote  
     

  14. #13  
    Forum Radioactive Isotope
    Join Date
    Feb 2009
    Posts
    4,941
    I thought that the geodesic was the "straight line" when spacetime is curved by gravity.

    Very much subject to correction,I don't think that your "straight line between the ends of an arc segment" actually exists.

    Sounds an interesting concept ,though.

    It reminds me a bit of those wormholes they talk about where the so called "fabric" of spacetime is stretched to breaking point and it is hypothesized that there could be some kind of a pathway.
    Reply With Quote  
     

  15. #14  
    Time Lord zinjanthropos's Avatar
    Join Date
    Dec 2005
    Location
    Driving in my car
    Posts
    5,751
    Quote Originally Posted by geordief View Post
    I thought that the geodesic was the "straight line" when spacetime is curved by gravity.

    Very much subject to correction,I don't think that your "straight line between the ends of an arc segment" actually exists.

    Sounds an interesting concept ,though.

    It reminds me a bit of those wormholes they talk about where the so called "fabric" of spacetime is stretched to breaking point and it is hypothesized that there could be some kind of a pathway.
    Ya, I guess a wormhole fits the bill. Shortcut through what, I don’t know. Come to think of it....isn’t that what all matter in motion does....tunnel through space time? Don’t think we’re sliding along something.
    Last edited by zinjanthropos; December 19th, 2020 at 06:34 PM.
    All that belongs to human understanding, in this deep ignorance and obscurity, is to be skeptical, or at least cautious; and not to admit of any hypothesis, whatsoever; much less, of any which is supported by no appearance of probability...Hume
    Reply With Quote  
     

  16. #15  
    Forum Radioactive Isotope
    Join Date
    Feb 2009
    Posts
    4,941
    Maybe the idea of a wormhole is (and so your "tunnel" description may be appropriate) that when quantum effects apply then tunnelling occurs (not that I would be very au fait with that)

    So when the spacetime becomes extremely curved as in the region of the singularity posited in a black hole then maybe that is a region where phenomena obey quantum rules.

    So maybe that is why tunnelling is imagined to occur under those circumstances and maybe the situation would be as you describe (joining the ends of the arc segments of the geodesics)

    Not a shortcut through anything just a way of linking two points.(quantum entanglement comes to mind ,though not in any particularly helpful way)
    Reply With Quote  
     

  17. #16  
    Time Lord zinjanthropos's Avatar
    Join Date
    Dec 2005
    Location
    Driving in my car
    Posts
    5,751
    If a wormhole is a path to another region of the universe then what what would the pathway consist of? Artists depict some sort of tube or funnel but something tells me it would be nothing like that. Would it be the area coming to you or vice versa?
    All that belongs to human understanding, in this deep ignorance and obscurity, is to be skeptical, or at least cautious; and not to admit of any hypothesis, whatsoever; much less, of any which is supported by no appearance of probability...Hume
    Reply With Quote  
     

  18. #17  
    Forum Radioactive Isotope
    Join Date
    Feb 2009
    Posts
    4,941
    Well I imagine the actual "pathway" as non existent .

    I think this might be an example (or a near cousin) of the "spooky action at a distance" phenomenon that I know so little about.

    I hope you have already learned that my expertise here and in other areas is pretty non existent.

    Let's hope one of the others can provide a more meaningful contribution(although I think the question itself is speculative and may require that long awaited theory of quantum gravity in order to address it better)
    Reply With Quote  
     

  19. #18  
    Time Lord zinjanthropos's Avatar
    Join Date
    Dec 2005
    Location
    Driving in my car
    Posts
    5,751
    Quote Originally Posted by geordief View Post
    Well I imagine the actual "pathway" as non existent .

    I think this might be an example (or a near cousin) of the "spooky action at a distance" phenomenon that I know so little about.

    I hope you have already learned that my expertise here and in other areas is pretty non existent.

    Let's hope one of the others can provide a more meaningful contribution(although I think the question itself is speculative and may require that long awaited theory of quantum gravity in order to address it better)
    I figure I know the least of anybody here so that qualifies everyone else as a sage. My biggest problem is finding the right words for what I’m trying to say or ask. Probably just jibber-jabber for some of the more learned.

    However I think this next question could be understood....if objects can pass through a naturally formed wormhole then light should also have no problem zinging it’s way from one part of the universe to another, so can we differentiate between wormhole light and natural starlight? I figure if natural wormholes occur then a portion of the observable universe might have its light origins elsewhere in the universe.
    All that belongs to human understanding, in this deep ignorance and obscurity, is to be skeptical, or at least cautious; and not to admit of any hypothesis, whatsoever; much less, of any which is supported by no appearance of probability...Hume
    Reply With Quote  
     

  20. #19  
    Forum Radioactive Isotope
    Join Date
    Feb 2009
    Posts
    4,941
    Well I imagine light might pass through one of those wormholes but then again might there be matter that was more elemental than light and would that get through instead?

    (Actually ,now I think this wormhole effect seems a bit similar to the "talking out of one's sphincter " phenomenon that one can easily lapse into when out of one's deapth

    Not sure how one could keep a watch out for wormhole in the sky.

    Would it be a steady stream of energetic particles coming from one particular direction?

    Might the stream be so weak as to be undetectable?

    Any idea where might be a good place to look? (Wikipedia?
    Reply With Quote  
     

  21. #20  
    Time Lord zinjanthropos's Avatar
    Join Date
    Dec 2005
    Location
    Driving in my car
    Posts
    5,751
    Quote Originally Posted by geordief View Post
    Not sure how one could keep a watch out for wormhole in the sky.
    For all I know we could be travelling thru a wormhole or be on the outside looking straight down the throat of one right now.
    All that belongs to human understanding, in this deep ignorance and obscurity, is to be skeptical, or at least cautious; and not to admit of any hypothesis, whatsoever; much less, of any which is supported by no appearance of probability...Hume
    Reply With Quote  
     

  22. #21  
    Forum Radioactive Isotope
    Join Date
    Feb 2009
    Posts
    4,941
    It seems to me that wormholes are hypothesized to exist where spacetime curvature is extreme.(intense gravity)

    That ,too my mind makes them very small even if possibly very energetic.

    Also I doubt if any "traveling" could be involved.

    It feels like it would be a case of "one moment an object is here and the next it is somewhere else" with the objects being minuscule and elementary.

    But ,I have no clue as to what is actually hypothesized about them in any serious way (if there is a serious way)

    I am not sure if there are any discussions on science forums about wormholes.I have never come across one


    All I have seen is the occasional article in popular scientific magazines.

    I haven't heard any new evidence over the past 10 years or so casting any light on the subject ,but I have not been paying special attention either.
    Reply With Quote  
     

  23. #22  
    Time Lord zinjanthropos's Avatar
    Join Date
    Dec 2005
    Location
    Driving in my car
    Posts
    5,751
    When a beam of light from a distant star travels through space it is probably deflected a few times by other gravitational fields so by the time it reaches your eyes the path it took was not a straight line. When astronomers use this light to calculate distance to the star I wonder if they take deflection into account. Seems to me the measured distances are longer than if starlight was a straight beam. Maybe they don’t think it makes a big difference or maybe there isn’t a difference, idk.
    All that belongs to human understanding, in this deep ignorance and obscurity, is to be skeptical, or at least cautious; and not to admit of any hypothesis, whatsoever; much less, of any which is supported by no appearance of probability...Hume
    Reply With Quote  
     

  24. #23  
    Forum Radioactive Isotope
    Join Date
    Feb 2009
    Posts
    4,941
    That is interesting. I have an idea it could be answered in different ways.

    Imagine if there was a small black hole between the Sun and the Earth and a pulse of light emanated from the Earth in the direction of the Sun ,spun around the Black Hole for some time ,was spat out again in the same direction of the Sun and then reflected back from the Sun to the Earth where it was recaptured by the original apparatus that had emitted it originally.

    It would be received later than an identical pulse of light that managed to avoid the Black Hole (that one would take about 16 minutes)

    The distance between the Earth and the Sun is 8 light minutes so I am not sure how that distance would be measured by the pulse of light that got held up by the Black Hole.

    I suppose if the existence of the Black Hole was already known as well as the amount of times the pulse went around it then it might be apparent that the Sun-Earth distance was in fact 8 light minutes.

    If the Black Hope's existence was unsuspected then they might think that the Sun was further away than expected.
    Reply With Quote  
     

  25. #24  
    Time Lord zinjanthropos's Avatar
    Join Date
    Dec 2005
    Location
    Driving in my car
    Posts
    5,751
    Quote Originally Posted by geordief View Post
    That is interesting. I have an idea it could be answered in different ways.

    Imagine if there was a small black hole between the Sun and the Earth and a pulse of light emanated from the Earth in the direction of the Sun ,spun around the Black Hole for some time ,was spat out again in the same direction of the Sun and then reflected back from the Sun to the Earth where it was recaptured by the original apparatus that had emitted it originally.

    It would be received later than an identical pulse of light that managed to avoid the Black Hole (that one would take about 16 minutes)

    The distance between the Earth and the Sun is 8 light minutes so I am not sure how that distance would be measured by the pulse of light that got held up by the Black Hole.

    I suppose if the existence of the Black Hole was already known as well as the amount of times the pulse went around it then it might be apparent that the Sun-Earth distance was in fact 8 light minutes.

    If the Black Hole's existence was unsuspected then they might think that the Sun was further away than expected.
    Can't see why light wouldn't pinball its way across spacetime or even be held up briefly as your fictitious scenario suggests. I can only think scientists measure it because that's how long it takes regardless of obstacles in its path.

    from wiki:
    The main disk of the Milky Way Galaxy is about 80,000 to 100,000 light-years in diameter, about 250,000 to 300,000 light-years in circumference, and outside the Galactic core, about 1,000 light-years in thickness.
    I think its called Gravitational Lensing, stand to be corrected.

    So light from a source directly behind the Milky Way from our vantage point, and if it were possible in a straight line, would travel approx 100,000 lys to get to Earthbound observer. However if the beam of light goes halfway round the Milky Way to me then it travels an extra 50,000 lys approx. I wonder if the beam that goes through the Milky Way might even travel farther than going around, idk.

    I'm probably doing something wrong because I really don't know if the effects of other gravitational fields make that much of a difference on a universal/galactic scale or if scientists already take affects into account. Trillions of galaxies out there and light from the farthest observable may be affected on its journey to us, can't see how it isn't.
    All that belongs to human understanding, in this deep ignorance and obscurity, is to be skeptical, or at least cautious; and not to admit of any hypothesis, whatsoever; much less, of any which is supported by no appearance of probability...Hume
    Reply With Quote  
     

  26. #25  
    Forum Radioactive Isotope
    Join Date
    Feb 2009
    Posts
    4,941
    Think you are right and that any trajectory could be up to infinitely long. So it is statistical the way that they measure the distance as those long pinball trajectories are vanishingly rare.
    Reply With Quote  
     

  27. #26  
    Time Lord zinjanthropos's Avatar
    Join Date
    Dec 2005
    Location
    Driving in my car
    Posts
    5,751
    Strictly layman, donít think Iím that correct, I donít know enough to claim anything

    If true then I wonder if we could observe the same galaxy in more than one place in the sky? Catch light thatís travelled different distances because of what its light rays may bump into along the way. Donít know what or if anything lies between us and the fleeing galaxies that might affect distance measured.

    https://astronomy.com/magazine/ask-a...-obscure-light

    excerpt:
    dark matter does have mass and its gravity can influence matter and light. So, dark matter does contribute to a phenomenon called gravitational lensing, in which a galaxyís mass ó including both its normal and dark matter ó causes the space-time around it to curve. As light from an object in the background, such as a more distant galaxy, encounters this curved space-time, it appears to bend, which distorts and can even multiply the image of the background object
    Should multiply be magnify....confusing to me.
    Last edited by zinjanthropos; December 23rd, 2020 at 12:48 PM.
    All that belongs to human understanding, in this deep ignorance and obscurity, is to be skeptical, or at least cautious; and not to admit of any hypothesis, whatsoever; much less, of any which is supported by no appearance of probability...Hume
    Reply With Quote  
     

  28. #27  
    Forum Radioactive Isotope
    Join Date
    Feb 2009
    Posts
    4,941
    Quote Originally Posted by zinjanthropos View Post
    Strictly layman, don’t think I’m that correct, I don’t know enough to claim anything

    If true then I wonder if we could observe the same galaxy in more than one place in the sky? Catch light that’s travelled different distances because of what its light rays may bump into along the way. Don’t know what or if anything lies between us and the fleeing galaxies that might affect distance measured.

    https://astronomy.com/magazine/ask-a...-obscure-light

    excerpt:
    dark matter does have mass and its gravity can influence matter and light. So, dark matter does contribute to a phenomenon called gravitational lensing, in which a galaxy’s mass — including both its normal and dark matter — causes the space-time around it to curve. As light from an object in the background, such as a more distant galaxy, encounters this curved space-time, it appears to bend, which distorts and can even multiply the image of the background object
    Should multiply be magnify....confusing to me.
    I wouldn't rule out "multiply"

    Look here. I managed to google it down

    http://en.wikipedia.org/wiki/Strong_...tional_lensing

    and (illustration) http://en.wikipedia.org/wiki/Gravitational_lens

    I don't suppose "we could observe the same galaxy in more than one place in the sky" but maybe I am wrong
    Reply With Quote  
     

  29. #28  
    Time Lord zinjanthropos's Avatar
    Join Date
    Dec 2005
    Location
    Driving in my car
    Posts
    5,751
    Quote Originally Posted by geordief View Post
    Quote Originally Posted by zinjanthropos View Post
    Strictly layman, don’t think I’m that correct, I don’t know enough to claim anything

    If true then I wonder if we could observe the same galaxy in more than one place in the sky? Catch light that’s travelled different distances because of what its light rays may bump into along the way. Don’t know what or if anything lies between us and the fleeing galaxies that might affect distance measured.

    https://astronomy.com/magazine/ask-a...-obscure-light

    excerpt:
    dark matter does have mass and its gravity can influence matter and light. So, dark matter does contribute to a phenomenon called gravitational lensing, in which a galaxy’s mass — including both its normal and dark matter — causes the space-time around it to curve. As light from an object in the background, such as a more distant galaxy, encounters this curved space-time, it appears to bend, which distorts and can even multiply the image of the background object
    Should multiply be magnify....confusing to me.
    I wouldn't rule out "multiply"

    Look here. I managed to google it down

    http://en.wikipedia.org/wiki/Strong_...tional_lensing

    and (illustration) http://en.wikipedia.org/wiki/Gravitational_lens

    I don't suppose "we could observe the same galaxy in more than one place in the sky" but maybe I am wrong
    Einstein's Cross multi-image was very interesting. An amateur skywatcher might think there's more than one.

    Let's say light from a deep space galaxy fades from view. Gone forever so we think. Light from that same galaxy could still be out there, wending its way toward us, simply delayed getting here. In that respect we could see a galaxy again, long or shortly (in geological terms) after it's disappeared....more of a question than a statement from me.

    Until today i had never heard of multiple views of a single light source in space but it seems astronomers have, yet never hear it mentioned. Probably wouldn't have understood it anyway, even if I did hear it
    All that belongs to human understanding, in this deep ignorance and obscurity, is to be skeptical, or at least cautious; and not to admit of any hypothesis, whatsoever; much less, of any which is supported by no appearance of probability...Hume
    Reply With Quote  
     

  30. #29  
    Time Lord zinjanthropos's Avatar
    Join Date
    Dec 2005
    Location
    Driving in my car
    Posts
    5,751
    Hey geo, just thought of something. Take two different lengths of fibre optic cable, splice their ends together and place a source of light at one end and an observer at the other, then turn on the light. I’m able to block light in either cable so it only travels through one length or the other, so I switch it back and forth. One on, one off. How would observer know how far away the light source is? Would an observer get two different measurements?
    All that belongs to human understanding, in this deep ignorance and obscurity, is to be skeptical, or at least cautious; and not to admit of any hypothesis, whatsoever; much less, of any which is supported by no appearance of probability...Hume
    Reply With Quote  
     

  31. #30  
    Forum Radioactive Isotope
    Join Date
    Feb 2009
    Posts
    4,941
    So ,if one length of cable goes around the Earth 100 times and the other goes around once....

    It should at first be possible to work out which path the light took but then again ,after a while perhaps it could have been either.

    There might be different ways of working out which path was taken but if both paths are 100% efficient (no leakage,pure vacuum etc) then I don't see the distance travelled by the light is a clue in itself.
    Reply With Quote  
     

  32. #31  
    Time Lord zinjanthropos's Avatar
    Join Date
    Dec 2005
    Location
    Driving in my car
    Posts
    5,751
    Quote Originally Posted by geordief View Post
    So ,if one length of cable goes around the Earth 100 times and the other goes around once....

    It should at first be possible to work out which path the light took but then again ,after a while perhaps it could have been either.

    There might be different ways of working out which path was taken but if both paths are 100% efficient (no leakage,pure vacuum etc) then I don't see the distance travelled by the light is a clue in itself.
    I wonder if Einstein could have done some interesting stuff with fibre optics.

    Imagining two separate cables of different lengths, each with one end at light source and other at observer. Don’t know how the observer could tell that he/she is looking at the same source.
    All that belongs to human understanding, in this deep ignorance and obscurity, is to be skeptical, or at least cautious; and not to admit of any hypothesis, whatsoever; much less, of any which is supported by no appearance of probability...Hume
    Reply With Quote  
     

  33. #32  
    Forum Radioactive Isotope
    Join Date
    Feb 2009
    Posts
    4,941
    Hm,I might have taken liberties with the two cables.

    Since those light waves are not following a geodesic in spacetime but actually bouncing off the inner surface of the fibre optic cable I now think that the "source" of the light that the observer sees in that circumstance is actually the last point of the cable that the light bounced off before it enters his or her eye/recording device.

    I have heard it explained with mirrors that the ingoing photon is absorbed by the surface and a new one is (re)emitted

    That may be garbled ,but if the fibreoptic cable is bent ,(as is needed in our scenario) then you can't look from one end to the other and see the original source of the light.

    Whether it is possible to replace the cable with a pinball machine made up of a Hampden Court of small black holes as a thought experiment from hell,I can't say but it would be more along the lines you were suggesting .
    Reply With Quote  
     

  34. #33  
    Time Lord zinjanthropos's Avatar
    Join Date
    Dec 2005
    Location
    Driving in my car
    Posts
    5,751
    Since those light waves are not following a geodesic in spacetime but actually bouncing off the inner surface of the fibre optic cable I now think that the "source" of the light that the observer sees in that circumstance is actually the last point of the cable that the light bounced off before it enters his or her eye/recording device.
    We can't observe light in a fibre optic cable and thus particles of light are observed when it emerges from an end. If light not observed then it emerges as a wave. So light travelling the geodesic of space is also bouncing around? I'm thinking light particles/waves on the inside track wouldn't travel as far as a photon on the outside track so some jostling might take place?

    From a viewing perspective, one cannot see a light stream traveling through a cable, no different than observing light in space. Did I just learn something here.....a wave of light can’t be observed?
    Last edited by zinjanthropos; January 3rd, 2021 at 10:19 AM.
    All that belongs to human understanding, in this deep ignorance and obscurity, is to be skeptical, or at least cautious; and not to admit of any hypothesis, whatsoever; much less, of any which is supported by no appearance of probability...Hume
    Reply With Quote  
     

  35. #34  
    Suspended
    Join Date
    Feb 2021
    Posts
    7
    thanks
    Reply With Quote  
     

  36. #35  
    Time Lord Paleoichneum's Avatar
    Join Date
    Oct 2008
    Location
    Washington State, USA
    Posts
    5,364
    So was your purpose in making this post simply to reach the link filter threshold?
    If more of us valued food and cheer and song above hoarded gold, it would be a merrier world. -Thorin Oakenshield

    The needs of the many outweigh the need of the few - Spock of Vulcan & Sentinel Prime of Cybertron ---proof that "the needs" are in the eye of the beholder.
    Reply With Quote  
     

  37. #36  
    Bullshit Intolerant PhDemon's Avatar
    Join Date
    Feb 2013
    Location
    Newcastle-upon-Tyne, UK
    Posts
    5,561
    Yep I reported a post as a bot or a twat...looks like it's option 2..
    Reply With Quote  
     

  38. #37  
    Genius Duck Dywyddyr's Avatar
    Join Date
    Jan 2013
    Location
    Scunthorpe, UK
    Posts
    11,961
    He's gone.
    "[Dywyddyr] makes a grumpy bastard like me seem like a happy go lucky scamp" - PhDemon
    Reply With Quote  
     

Similar Threads

  1. Replies: 4
    Last Post: October 21st, 2010, 03:53 PM
  2. A new view for the universe
    By nwaogu in forum Astronomy & Cosmology
    Replies: 4
    Last Post: February 7th, 2006, 09:11 AM
Bookmarks
Bookmarks
Posting Permissions
  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •