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Big story ....CERN scientists break the speed of light

24

Comments

  • #52
    osnola ibax
    Registered Users Posts: 2,194 ✭✭✭osnola ibax


    Iwannahurl wrote: »
    A neutrino walks into a bar.

    And doesn't stop.

    A neutrino walks into a bar and says "its ok, im just passing through"


  • #53
    Iwannahurl
    Closed Accounts Posts: 8,156 ✭✭✭Iwannahurl


    osnola ivax wrote: »
    A neutrino walks into a bar and says "its ok, im just passing through"




    No charge then?


  • #54
    roosh
    Registered Users, Registered Users 2 Posts: 2,553 ✭✭✭roosh


    Faster-than-light neutrino claim bolstered

    Interesting article which outlines how they might have accurate measurements.

    I read somewhere that we may have to wait until 2014 before fermilab can test this claim!


  • #55
    Gandalph
    Registered Users, Registered Users 2 Posts: 1,792 ✭✭✭Gandalph


    Enough with all these neutrino jokes.

    I heard them all next week.


  • #56
    Iwannahurl
    Closed Accounts Posts: 8,156 ✭✭✭Iwannahurl


    roosh wrote: »
    Faster-than-light neutrino claim bolstered

    Interesting article which outlines how they might have accurate measurements.

    I read somewhere that we may have to wait until 2014 before fermilab can test this claim!





    "But only time will tell whether the result holds up to additional scrutiny..."


  • #57
    Capt'n Midnight
    Moderators, Recreation & Hobbies Moderators, Science, Health & Environment Moderators, Technology & Internet Moderators Posts: 92,521 Mod ✭✭✭✭Capt'n Midnight


    fontanalis wrote: »
    The barman says, sorry we don't serve time travelers.
    Two time travelers walk into a bar.
    Was it the same person meeting himself ?


  • #58
    Kohl
    Closed Accounts Posts: 130 ✭✭Kohl


    I think this thread has gone off the boil somewhat. Like the actual research story. Mightn't hear anything sensational for a while.


  • #59
    roosh
    Registered Users, Registered Users 2 Posts: 2,553 ✭✭✭roosh


    Kohl wrote: »
    I think this thread has gone off the boil somewhat. Like the actual research story. Mightn't hear anything sensational for a while.
    We might have to wait until 2014!!


  • #60
    roosh
    Registered Users, Registered Users 2 Posts: 2,553 ✭✭✭roosh


    roosh wrote: »
    We might have to wait until 2014!!

    <Insert time travel joke here>


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  • #61
    roosh
    Registered Users, Registered Users 2 Posts: 2,553 ✭✭✭roosh


    Just wondering about how this will be tested? I read that scientists at Fermilab were preparing to test it, but could a different group of scientists not use the same equipment, and run it much sooner?


  • #62
    Morbert
    Registered Users, Registered Users 2 Posts: 3,457 ✭✭✭Morbert


    roosh wrote: »
    Just wondering about how this will be tested? I read that scientists at Fermilab were preparing to test it, but could a different group of scientists not use the same equipment, and run it much sooner?

    Japan would be our best bet. They have a similar neutrino experiment, and data from previous experiments could be comparable to OPERAS. It will only take a few months to see if there is a comparison.


  • #63
    roosh
    Registered Users, Registered Users 2 Posts: 2,553 ✭✭✭roosh


    Morbert wrote: »
    Japan would be our best bet. They have a similar neutrino experiment, and data from previous experiments could be comparable to OPERAS. It will only take a few months to see if there is a comparison.

    cheres.

    but, is there a reason that a different group of scientists couldn't use the same equipment? This is based on reading about the Higgs; I'm just wondering if the Higgs were found would there be the need for independent verification also?


  • #64
    Morbert
    Registered Users, Registered Users 2 Posts: 3,457 ✭✭✭Morbert


    roosh wrote: »
    cheres.

    but, is there a reason that a different group of scientists couldn't use the same equipment? This is based on reading about the Higgs; I'm just wondering if the Higgs were found would there be the need for independent verification also?

    If it is a systematic error in the apparatus, a different group of scientists would still produce the same results. Basically, it needs to be shown that the result is not an artefact of their equipment. There is already a large discrepancy between their measurements and other neutrino measurements from supernovae.


  • #65
    roosh
    Registered Users, Registered Users 2 Posts: 2,553 ✭✭✭roosh


    Morbert wrote: »
    If it is a systematic error in the apparatus, a different group of scientists would still produce the same results. Basically, it needs to be shown that the result is not an artefact of their equipment. There is already a large discrepancy between their measurements and other neutrino measurements from supernovae.

    can the apparatus not be checked for errors, and corrected, or are they fixed in that repsect?

    Would the same apply to the Higgs then as well?


  • #66
    Curly Judge
    Registered Users, Registered Users 2 Posts: 2,708 ✭✭✭Curly Judge


    This about sorry.
    I've spent the day in a neutrino bar.
    I'll have an awful head on me yesterday!


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  • #67
    Morbert
    Registered Users, Registered Users 2 Posts: 3,457 ✭✭✭Morbert


    roosh wrote: »
    can the apparatus not be checked for errors, and corrected, or are they fixed in that repsect?

    Would the same apply to the Higgs then as well?

    They spent month checking and re-checking. But the standard of rigour in science is high.

    The signature of the Higgs field will presumably be far more definitive. There will be less need for immediate repeatability.


  • #68
    del88
    Registered Users, Registered Users 2 Posts: 1,136 ✭✭✭del88


    U.S.-based particle accelerator Fermilab said it would conduct tests that investigate whether neutrino particles can travel faster than the speed of light.
    http://www.rawstory.com/rs/2011/09/26/u-s-lab-to-try-and-break-speed-of-light/


  • #69
    airsofter2012
    Closed Accounts Posts: 17 ✭airsofter2012


    how much does or will this affect us


  • #70
    AlmightyCushion
    Moderators, Education Moderators, Technology & Internet Moderators Posts: 35,100 Mod ✭✭✭✭AlmightyCushion


    airsofter2012 wrote: »
    how much does or will this affect us

    You'll be able to buy a new neutrino based lightbulb that will turn on before you flip the switch.


  • #71
    msihl
    Registered Users Posts: 6 ✭msihl


    Hi guys,

    I'm new to this forum....I recommend the following blog posts by Sean Carroll over at Cosmic Variance:
    http://blogs.discovermagazine.com/cosmicvariance/2011/09/23/faster-than-light-neutrinos/
    http://blogs.discovermagazine.com/cosmicvariance/2011/09/24/can-neutrinos-kill-their-own-grandfathers/

    I guess most people working in the field think that the result will likely not hold up....it would be extremely interesting though if it did. For example, Lorentz invariance could be spontaneously broken.

    Also, space itself can expand faster than the speed of light (e.g. during inflation)


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  • #72
    shizz
    Registered Users, Registered Users 2 Posts: 1,506 ✭✭✭shizz


    msihl wrote: »

    Also, space itself can expand faster than the speed of light (e.g. during inflation)

    This is only relative to the observer. The space itself is not expanding faster than the speed of light. IIRC


  • #73
    msihl
    Registered Users Posts: 6 ✭msihl


    No, that is not correct! (Btw, what does the speed of sound have to do with anything???).
    Read this:
    http://astro.berkeley.edu/~jcohn/inflation.html
    There the effect on horizons (i.e. the boundaries of regions that are causally connected) is explained:

    "A special feature of inflation is its effect on horizons. The horizon demarcates the boundary of causally connected regions, regions that light rays (which travel at the fastest speed that any signal can travel) can reach since the time of the big bang. These regions grow over time, as light has more time to travel, but the expansion of the universe means that over time there is more space to cross as well. When the universe isn't inflating, such as now, regions which are larger and larger come inside the horizon and become causally connected. During inflation, the expansion of the universe wins out. Regions which were causally connected are separated so fast by the expansion of space that a region once in causal contact can have parts of it "pushed out" of the horizon."

    This is what people mean by "space expands faster than the speed of light".


  • #74
    shizz
    Registered Users, Registered Users 2 Posts: 1,506 ✭✭✭shizz


    msihl wrote: »
    No, that is not correct! (Btw, what does the speed of sound have to do with anything???).
    Read this:
    http://astro.berkeley.edu/~jcohn/inflation.html
    There the effect on horizons (i.e. the boundaries of regions that are causally connected) is explained:

    "A special feature of inflation is its effect on horizons. The horizon demarcates the boundary of causally connected regions, regions that light rays (which travel at the fastest speed that any signal can travel) can reach since the time of the big bang. These regions grow over time, as light has more time to travel, but the expansion of the universe means that over time there is more space to cross as well. When the universe isn't inflating, such as now, regions which are larger and larger come inside the horizon and become causally connected. During inflation, the expansion of the universe wins out. Regions which were causally connected are separated so fast by the expansion of space that a region once in causal contact can have parts of it "pushed out" of the horizon."

    This is what people mean by "space expands faster than the speed of light".

    Sorry I was doing an equation involving the speed of sound during reading this haha. I also didn't notice that you meant the initial inflationary period. I was referring to the expansion of the universe where the farther something is away from us that faster it seems to move away, with places apparently moving farther than the speed of light away.


  • #75
    Seifer
    Registered Users, Registered Users 2 Posts: 2,265 ✭✭✭Seifer


    Possible explanation: http://www.technologyreview.com/blog/arxiv/27260/


  • #76
    Iwannahurl
    Closed Accounts Posts: 8,156 ✭✭✭Iwannahurl


    Seifer wrote: »
    Possible explanation: http://www.technologyreview.com/blog/arxiv/27260/




    Super article, thanks.

    As I was reading it I thought it made the OPERA experiment sound like an inadvertent confirmation of Relativity, so I was pleased with the last paragraph:
    If it stands up, this episode will be laden with irony. Far from breaking Einstein's theory of relatively, the faster-than-light measurement will turn out to be another confirmation of it.


  • #77
    Capt'n Midnight
    Moderators, Recreation & Hobbies Moderators, Science, Health & Environment Moderators, Technology & Internet Moderators Posts: 92,521 Mod ✭✭✭✭Capt'n Midnight


    In the period that Einstein was active as a professor, one of his students
    came to him and said: "The questions of this year's exam are the same as
    last years!" "True," Einstein said, "but this year all answers are
    different."


  • #78
    Iwannahurl
    Closed Accounts Posts: 8,156 ✭✭✭Iwannahurl


    A theoretical physicist's wife found him in bed with another woman.

    "Darling," he said, "I can explain everything."


  • #79
    Full.Duck
    Registered Users, Registered Users 2 Posts: 315 ✭✭Full.Duck


    Just been keeping a lazy eye on this, skimmed through the thread. Most posts that give "possible" explanations. So i'm guessing there has still been no concrete proof what has happened here?

    What is the most reasonable explanation so far?


  • #80
    Iwannahurl
    Closed Accounts Posts: 8,156 ✭✭✭Iwannahurl


    Full.Duck wrote: »
    Just been keeping a lazy eye on this, skimmed through the thread. Most posts that give "possible" explanations. So i'm guessing there has still been no concrete proof what has happened here?

    What is the most reasonable explanation so far?




    This is a good one, IMO.


  • #81
    Professor_Fink
    Registered Users, Registered Users 2 Posts: 861 ✭✭✭Professor_Fink


    Iwannahurl wrote: »
    This is a good one, IMO.

    No it isn't. The GPS system already corrects for such relativistic effects. The most likely explanation I have heard so far is that the fact that they only did the geodesy survey twice might fail to detect periodic changes in the earths shape (which do occur).


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  • #82
    Anonymo
    Registered Users, Registered Users 2 Posts: 151 ✭✭Anonymo


    Professor_Fink wrote: »
    No it isn't. The GPS system already corrects for such relativistic effects. The most likely explanation I have heard so far is that the fact that they only did the geodesy survey twice might fail to detect periodic changes in the earths shape (which do occur).

    There are two explanations that I've heard that seem plausible. One is to do with the synchronisation of clocks. To do this you have them in the same place, synchronise and then transport the clocks. However during the transportation you will encounter relativistic effects (this is akin the the integrated sachs wolfe effect in cosmology where you move in and out of potential wells of changing sizes). I can't remember the arxiv reference now but it's by Carlo Contaldi of Imperial who is pretty good. This effect may acount for 20ns of the spurious 30ns.
    The second effect is to do with the assumption that the final distribution of neutrinos is the same as the incident protons. While this is reasonable, the fact that you measure so few of the produced neutrinos means that you may be sampling from the tail of the actual distribution - i.e. the observed distribution is not the same as the actual distribution.


  • #83
    Curly Judge
    Registered Users, Registered Users 2 Posts: 2,708 ✭✭✭Curly Judge


    Anonymo wrote: »
    There are two explanations that I've heard that seem plausible. One is to do with the synchronisation of clocks. To do this you have them in the same place, synchronise and then transport the clocks. However during the transportation you will encounter relativistic effects (this is akin the the integrated sachs wolfe effect in cosmology where you move in and out of potential wells of changing sizes). I can't remember the arxiv reference now but it's by Carlo Contaldi of Imperial who is pretty good. This effect may acount for 20ns of the spurious 30ns.
    The second effect is to do with the assumption that the final distribution of neutrinos is the same as the incident protons. While this is reasonable, the fact that you measure so few of the produced neutrinos means that you may be sampling from the tail of the actual distribution - i.e. the observed distribution is not the same as the actual distribution.


    Those damned statistics again eh?


  • #84
    Iwannahurl
    Closed Accounts Posts: 8,156 ✭✭✭Iwannahurl


    Professor_Fink wrote: »
    No it isn't. The GPS system already corrects for such relativistic effects.




    To what level of accuracy?


  • #85
    Anonymo
    Registered Users, Registered Users 2 Posts: 151 ✭✭Anonymo


    Iwannahurl wrote: »
    To what level of accuracy?

    It's really accurate. It definitely isn't the standard gps error (which they've accounted for in their error estimation by the way). They certainly wouldn't make that type of mistake.


  • #86
    WebGeek
    Closed Accounts Posts: 145 ✭✭WebGeek


    Wasn't general relativity theory proven - I thought science was never wrong? I suppose you don't have all the answers after all.


  • #87
    Seifer
    Registered Users, Registered Users 2 Posts: 2,265 ✭✭✭Seifer


    WebGeek wrote: »
    Wasn't general relativity theory proven - I thought science was never wrong? I suppose you don't have all the answers after all.

    Wow, that's embarrassing :(
    The great thing about science is that it welcomes such questions with open arms. Events such as this provide either the chance to expand our knowledge or confirm what we already know.


  • #88
    Iwannahurl
    Closed Accounts Posts: 8,156 ✭✭✭Iwannahurl


    Anonymo wrote: »
    It's really accurate. It definitely isn't the standard gps error (which they've accounted for in their error estimation by the way). They certainly wouldn't make that type of mistake.



    To achieve this level of precision, the clock ticks from the GPS satellites must be known to an accuracy of 20-30 nanoseconds. However, because the satellites are constantly moving relative to observers on the Earth, effects predicted by the Special and General theories of Relativity must be taken into account to achieve the desired 20-30 nanosecond accuracy.
    http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit5/gps.html


  • #89
    Professor_Fink
    Registered Users, Registered Users 2 Posts: 861 ✭✭✭Professor_Fink


    WebGeek wrote: »
    Wasn't general relativity theory proven - I thought science was never wrong? I suppose you don't have all the answers after all.

    You're wrong on so many levels. No science is ever "proven", there is simply more and more supporting evidence for a particular theory gathered. I don't know what it means for science to be wrong. Do you mean the scientific method? If so, this is hardly a counter example. If you mean instead GR, then firstly superluminal neutrinos don't disprove GR, and secondly no one credible ever said GR cannot be wrong.


  • #90
    Professor_Fink
    Registered Users, Registered Users 2 Posts: 861 ✭✭✭Professor_Fink


    Iwannahurl wrote: »
    To achieve this level of precision, the clock ticks from the GPS satellites must be known to an accuracy of 20-30 nanoseconds. However, because the satellites are constantly moving relative to observers on the Earth, effects predicted by the Special and General theories of Relativity must be taken into account to achieve the desired 20-30 nanosecond accuracy.
    http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit5/gps.html

    That is for the GPS in a car. The GPS cards they used are far more accurate (go watch the CERN lecture, since they went through the GPS in excruciating detail), and use a multifrequency encoding the circumvent the usual limiting factor imposed by the state of the ionosphere.


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  • #91
    Morbert
    Registered Users, Registered Users 2 Posts: 3,457 ✭✭✭Morbert


    Looks like the result has survived the modified experiment, ruling out a few important sources of systematic errors. While I am not holding my breath, I am getting a little excited.


  • #92
    TheMilkyPirate
    Registered Users Posts: 6,017 ✭✭✭TheMilkyPirate


    Morbert wrote: »
    Looks like the result has survived the modified experiment, ruling out a few important sources of systematic errors. While I am not holding my breath, I am getting a little excited.

    Is there many more possible errors?


  • #93
    krd
    Banned (with Prison Access) Posts: 3,455 ✭✭✭krd


    Professor_Fink wrote: »
    That is for the GPS in a car. The GPS cards they used are far more accurate (go watch the CERN lecture, since they went through the GPS in excruciating detail), and use a multifrequency encoding the circumvent the usual limiting factor imposed by the state of the ionosphere.

    Could something be up with the Ionosphere?

    I might given the Cern lecture a look - I'm not so sure I'm up for excurciating at the minute. I don't want to look, but are they averaging the GPS result from the different frequencies. (one of the many things I've forgotten how to do, was the equations for GPS - the one used by cars is accurate to 1 square metre. But I don't remember any parts that took into account atmospheric effects )

    If there was solar flares were more active than usual, could it throw their GPS.

    The most likely explanation I have heard so far is that the fact that they only did the geodesy survey twice might fail to detect periodic changes in the earths shape (which do occur).

    The path is from Cern, Switzerland, to Gran Sasso, Italy- 450 miles (720km) apart. I wonder do things like the temperature of the crust, variations in tension (I think that's enough to cause anomalies in gravity), plus little shifts, would those things add up - or at least mess up the measurements.


    My understanding of relativity: if you took two synchronised clocks from Cern, and transported them to Gran Sasso. One by car, the other by train. The clock travelling by train would be slightly ahead of the clock that travelled by car, once they both reached Gran Sasso. (or do I have that back to front?).

    If you could hear each clock ticking from Gran Sasso, would the clock on the train sound like it was ticking faster?

    Or I have something wrong? This is confusing me. If instead of a clock tick - each clock emitted a sine wave ( say 60 Hz) - which is put through a speaker. I know this is wrong, but I don't understand why. But if, the person in Gran Sasso measured the difference in frequency - would the ratio of observed frequency over 60 Hz give the ratio of time dilation. I know that's wrong, if it was right clocks in aeroplanes, would be out of synch with ground all the time.


  • #94
    AlmightyCushion
    Moderators, Education Moderators, Technology & Internet Moderators Posts: 35,100 Mod ✭✭✭✭AlmightyCushion


    krd wrote: »
    Professor_Fink wrote: »
    That is for the GPS in a car. The GPS cards they used are far more accurate (go watch the CERN lecture, since they went through the GPS in excruciating detail), and use a multifrequency encoding the circumvent the usual limiting factor imposed by the state of the ionosphere.

    Could something be up with the Ionosphere?

    I might given the Cern lecture a look - I'm not so sure I'm up for excurciating at the minute. I don't want to look, but are they averaging the GPS result from the different frequencies. (one of the many things I've forgotten how to do, was the equations for GPS - the one used by cars is accurate to 1 square metre. But I don't remember any parts that took into account atmospheric effects )

    If there was solar flares were more active than usual, could it throw their GPS.

    The most likely explanation I have heard so far is that the fact that they only did the geodesy survey twice might fail to detect periodic changes in the earths shape (which do occur).

    The path is from Cern, Switzerland, to Gran Sasso, Italy- 450 miles (720km) apart. I wonder do things like the temperature of the crust, variations in tension (I think that's enough to cause anomalies in gravity), plus little shifts, would those things add up - or at least mess up the measurements.


    My understanding of relativity: if you took two synchronised clocks from Cern, and transported them to Gran Sasso. One by car, the other by train. The clock travelling by train would be slightly ahead of the clock that travelled by car, once they both reached Gran Sasso. (or do I have that back to front?).

    If you could hear each clock ticking from Gran Sasso, would the clock on the train sound like it was ticking faster?

    Or I have something wrong? This is confusing me. If instead of a clock tick - each clock emitted a sine wave ( say 60 Hz) - which is put through a speaker. I know this is wrong, but I don't understand why. But if, the person in Gran Sasso measured the difference in frequency - would the ratio of observed frequency over 60 Hz give the ratio of time dilation. I know that's wrong, if it was right clocks in aeroplanes, would be out of synch with ground all the time.
    Only if the clock on the train was travelling faster than the one in the car. When side by side both clocks will tick at the same time though. The reason for this is that on the train it's not the clock that is slowing down, it is time itself. The same does happen on planes but the differences are unnoticeable to Humans (we're talking nanoseconds).


  • #95
    old_aussie
    Registered Users, Registered Users 2 Posts: 3,410 ✭✭✭old_aussie


    A total of 15,000 beams of neutrinos - tiny particles that pervade the cosmos - were fired over a period of three years from CERN towards Gran Sasso 730 (500 miles) km away, where they were picked up by giant detectors.

    If their calculations are as accurate as the miles to kilometers conversion above then there is a small problem.


  • #96
    krd
    Banned (with Prison Access) Posts: 3,455 ✭✭✭krd


    old_aussie wrote: »
    A total of 15,000 beams of neutrinos - tiny particles that pervade the cosmos - were fired over a period of three years from CERN towards Gran Sasso 730 (500 miles) km away, where they were picked up by giant detectors.

    If their calculations are as accurate as the miles to kilometers conversion above then there is a small problem.

    I cut and pasted that figure from the Guardian (also known, pejoratively, as the Gaurnaid - for typos and errors)


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  • #97
    krd
    Banned (with Prison Access) Posts: 3,455 ✭✭✭krd


    AlmightyCushion wrote: »
    Only if the clock on the train was travelling faster than the one in the car. When side by side both clocks will tick at the same time though.

    Yes. I was implying that - assuming a train will typically travel much faster than a car. Especially some of those high speed Euro ones. And I'm not sure - but maybe it still stands that Mussolini got the trains to run on time.

    A long time ago, I studied some science at an IT - I'm slowly working back to it. But can't even do some of the simple maths I used. I've been reading up on Einstein's relativity - but I haven't got that far with it. Like I don't understand, yet, why nothing can, or is supposed to, travel faster than light.
    The reason for this is that on the train it's not the clock that is slowing down, it is time itself.

    But time is relative. When it comes to sound. If there is a brass band on a train, and they all play the note D, if the train is going fast enough - people in front of the train, will hear the note E, because the frequency has been shifted up by the Doppler effect (or another way to put it, the wavelength has been shortened) However, on the train, the band still hear the note D - and this is where relativity gets weird - the space and time for the observer, is not the same space and time for the band on the train.


    Now. I know I'm wrong - but I'm not sure how I'm wrong.

    If on the train, there was a clock, with a very loud second tick - and the train was going very fast, but nowhere near the speed of light (don't want to calculate and estimate - I am that rusty) but lets say a few thousand miles an hour. To a stationary observer - within earshot of the clock tick, somewhere well in front of the train - the clock tick would sound like it was going a lot faster than one tick per second - or 1 Hz, if you want to be particular. let's say the train was going fast enough the Doppler effect made the tick 2 Hz. That would be a massive time dilation. You wouldn't be able to take a long car journey on a motorway, without having to reset your watch when you got to your destination.

    Now. I know, that time dilation caused by relativity, is related to light (I haven't worked the proof out myself - hopefully in a few months time - just for the sake of being able to say I've done it - and an irritating curiosity).

    If the train had a light bulb on the front - it was going fast enough - if the observer in front of the train saw a blue light - you could calculate the time dilation based on the observed shift in the wavelength.

    If the time dilation were to be calculated from the Doppler effect with sound (not light) - if would be a massive difference.
    The same does happen on planes but the differences are unnoticeable to Humans (we're talking nanoseconds).

    It's in nanoseconds, because the time dilation is related to light, and not sound. If you consider how I've used sound - the differences become very noticeable. With planes, the difference would be in full seconds, even minutes - I know I'm wrong, but I don't understand why I'm wrong.


  • #98
    AlmightyCushion
    Moderators, Education Moderators, Technology & Internet Moderators Posts: 35,100 Mod ✭✭✭✭AlmightyCushion


    krd wrote: »
    AlmightyCushion wrote: »
    Only if the clock on the train was travelling faster than the one in the car. When side by side both clocks will tick at the same time though.

    Yes. I was implying that - assuming a train will typically travel much faster than a car. Especially some of those high speed Euro ones. And I'm not sure - but maybe it still stands that Mussolini got the trains to run on time.

    A long time ago, I studied some science at an IT - I'm slowly working back to it. But can't even do some of the simple maths I used. I've been reading up on Einstein's relativity - but I haven't got that far with it. Like I don't understand, yet, why nothing can, or is supposed to, travel faster than light.
    The reason for this is that on the train it's not the clock that is slowing down, it is time itself.

    But time is relative. When it comes to sound. If there is a brass band on a train, and they all play the note D, if the train is going fast enough - people in front of the train, will hear the note E, because the frequency has been shifted up by the Doppler effect (or another way to put it, the wavelength has been shortened) However, on the train, the band still hear the note D - and this is where relativity gets weird - the space and time for the observer, is not the same space and time for the band on the train.


    Now. I know I'm wrong - but I'm not sure how I'm wrong.

    If on the train, there was a clock, with a very loud second tick - and the train was going very fast, but nowhere near the speed of light (don't want to calculate and estimate - I am that rusty) but lets say a few thousand miles an hour. To a stationary observer - within earshot of the clock tick, somewhere well in front of the train - the clock tick would sound like it was going a lot faster than one tick per second - or 1 Hz, if you want to be particular. let's say the train was going fast enough the Doppler effect made the tick 2 Hz. That would be a massive time dilation. You wouldn't be able to take a long car journey on a motorway, without having to reset your watch when you got to your destination.

    Now. I know, that time dilation caused by relativity, is related to light (I haven't worked the proof out myself - hopefully in a few months time - just for the sake of being able to say I've done it - and an irritating curiosity).

    If the train had a light bulb on the front - it was going fast enough - if the observer in front of the train saw a blue light - you could calculate the time dilation based on the observed shift in the wavelength.

    If the time dilation were to be calculated from the Doppler effect with sound (not light) - if would be a massive difference.
    The same does happen on planes but the differences are unnoticeable to Humans (we're talking nanoseconds).

    It's in nanoseconds, because the time dilation is related to light, and not sound. If you consider how I've used sound - the differences become very noticeable. With planes, the difference would be in full seconds, even minutes - I know I'm wrong, but I don't understand why I'm wrong.
    I'm on my phone at the moment so I'll be brief and give a better explanation when I have a proper keyboard. Doppler shift is the phenomenon you are talking about and it is unrelated to relativity. The difference in tone is down to compression of the sound wave and not to do with the time dilation effect of relativity.

    On a plane the difference is nanoseconds, not seconds.


  • #99
    krd
    Banned (with Prison Access) Posts: 3,455 ✭✭✭krd


    AlmightyCushion wrote: »
    I'm on my phone at the moment so I'll be brief and give a better explanation when I have a proper keyboard. Doppler shift is the phenomenon you are talking about and it is unrelated to relativity.

    The Doppler effect is related to relativity.
    The difference in tone is down to compression of the sound wave and not to do with the time dilation effect of relativity.

    The tone appears compressed from the perspective of an inertial observer. In reality, there can be no such thing as an inertial observer - we're all moving in space. If you were truly inertial in space, the sound wave would appear to go through all kinds of contortions. From the perspective of the observer who is at the point where the tone is being generated - the wave would appear to move evenly through space - at the same speed in all directions. From the perspective of an inertial observer - listening to a tone coming from an approaching train, the pitch appears higher. How can the wave be compressed in the space of one observer, and not in the space of the other. If there is an observer behind the train, they will hear the pitch as lower - so the wave appears to be stretched out.



    Similarly with light. Light from distant stars, travelling away from us, is red-shifted. The wave length appears to us as stretched out. If you left the star, travelling along side the light, at the speed of light, the wave length would appear to you as constant - it wouldn't appear stretch.

    From the point of the observer on earth. The length of the wave length, appears to be longer. And the time it takes the light to travel a distance of its' wavelength appears to be longer.

    I had a brutal physics teacher at school. lot's of wrong headed ideas (filling my head with wrong headed ideas )- one was the Doppler effect was caused by air pressure of the inertial air mass resisting the the approaching sound wave - forcing the sound wave to compress - like pushing a spring against a wall. Of course that would mean the formula for calculating the frequency change wouldn't make sense.


    On a plane the difference is nanoseconds, not seconds.

    Yes, I know it's nanoseconds. If you read what I said in my post.


  • #100
    shizz
    Registered Users, Registered Users 2 Posts: 1,506 ✭✭✭shizz


    krd wrote: »
    The Doppler effect is related to relativity.



    The tone appears compressed from the perspective of an inertial observer. In reality, there can be no such thing as an inertial observer - we're all moving in space. If you were truly inertial in space, the sound wave would appear to go through all kinds of contortions. From the perspective of the observer who is at the point where the tone is being generated - the wave would appear to move evenly through space - at the same speed in all directions. From the perspective of an inertial observer - listening to a tone coming from an approaching train, the pitch appears higher. How can the wave be compressed in the space of one observer, and not in the space of the other. If there is an observer behind the train, they will hear the pitch as lower - so the wave appears to be stretched out.



    Similarly with light. Light from distant stars, travelling away from us, is red-shifted. The wave length appears to us as stretched out. If you left the star, travelling along side the light, at the speed of light, the wave length would appear to you as constant - it wouldn't appear stretch.

    From the point of the observer on earth. The length of the wave length, appears to be longer. And the time it takes the light to travel a distance of its' wavelength appears to be longer.

    I had a brutal physics teacher at school. lot's of wrong headed ideas (filling my head with wrong headed ideas )- one was the Doppler effect was caused by air pressure of the inertial air mass resisting the the approaching sound wave - forcing the sound wave to compress - like pushing a spring against a wall. Of course that would mean the formula for calculating the frequency change wouldn't make sense.





    Yes, I know it's nanoseconds. If you read what I said in my post.

    From my understanding the Doppler effect isn't relative in the same way time is. It's cause by the moving source producing sound waves closer at each successive stage because the source is moving in the direction of the waves travel. Of course if you were behind the source you would hear a lower tone because each successive wave is produced further away then the last one. Also, of course if you kept in line with the source you wouldn't hear a change in pitch as you are on the side of it or within it so you are always an equal distance away so these changes can't effect what you hear. So yes the sound you hear is relative with your position but it is not linked with Space and time relativity.

    Another way to see how it differs from relativity is, if something was moving a lot faster than you and you could observe someone within that object that was moving that fast, you would see them move a lot slower within it as time for them has slowed down. (obviously exaggerated) But as they move towards you and move away you won't notice any change in how slow they are moving, unless the object slowed down. At least this is how I understand it so Im open to corrections.


  • #101
    opinion guy
    Closed Accounts Posts: 11,001 ✭✭✭✭opinion guy


    baraca wrote: »
    Is there many more possible errors?

    General rule that applies to any and all science: there are always more possible errors.


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