The Naked Scientists

The Naked Scientists Forum

Poll

The experimental results suggest that neutrinos are "Faster than light". Why is that?

Swiss watches are better than Italian watches.
2 (12.5%)
It turns out the Swiss meter is slightly different from the Italian meter.
0 (0%)
Systematic computational error
2 (12.5%)
Neutrinos "tunnel" faster than light through atomic nuclei.
2 (12.5%)
Previously unknown gravitational anomaly
2 (12.5%)
Safely grazing sheepies used magic to speed up neutrinos
1 (6.3%)
Too many adult beverages
2 (12.5%)
The Earth is more curved than we thought
0 (0%)
Any mass with very high energy can travel faster than light.
1 (6.3%)
There is only one neutrino that travels infinitely fast and is thus everywhere at once
1 (6.3%)
A missing delay in electronics or a problem of synchronization with satellites
0 (0%)
It's not the neutrinos that are fast, it's the photons that are slow
1 (6.3%)
Neutrinos are allowed to take shortcuts through one of the other 7 dimensions
1 (6.3%)
The neutrinos were being chased by Zurich gnomes
0 (0%)
Insufficient slide-rule lubricant
1 (6.3%)
Some of the Swiss neutrinos were unknowingly entangled with Italian neutrinos
0 (0%)
Surveyors were beguiled by sheep
0 (0%)
The technicians cocked it up and the scientists are going to make sure they take the heat.
0 (0%)

Total Members Voted: 16

Author Topic: Why don't OPERA Gran Sasso results comply with current knowledge?  (Read 21493 times)

Offline syhprum

  • Neilep Level Member
  • ******
  • Posts: 3823
  • Thanked: 19 times
    • View Profile
I am sure they did it many many times and averaged out varying ionospheric conditions.
It is possible to compute c from measurements of magnetic and electrostatic phenomena how accurately can these be measured and how closely does the the measured value of c compare.
 

Offline imatfaal

  • Neilep Level Member
  • ******
  • Posts: 2787
  • rouge moderator
    • View Profile
I voted for the watches because it's closest to what I think happened: The chronometer wasn't started and stopped accurately enough

It would be a bit embarrassing if it turned out that was the cause, but I suspect it's quite tricky to properly synchronize two clocks at different locations. Anyone know what the procedure is, and how much tolerance is acceptable for this experiment?

Nah - synchronizing the clocks is a comparative doddle (using doddle almost completely wrongly).

Metrology institutes around the world have long established the common view GPS method of synchronization/comparison.  This algorithm and protocol for synchronizing geographically remote clocks is not new and has been exhaustively tested (there remains the possibility that Gran Sasso didnt follow the instructions properly).

I seem to remember that with the upgraded beacons and after the swiss and german metrology institutes (now I bet they are a bunch of fun and hoopy guys) got involved that the max error was single nanaoseconds

Well yes, but how does it actually work? If science was based on "following the instructions", we'd still be hanging from a gumm tree.

Both ends have atomic clocks - whilst one satellite is overhead and both sites are receiving the signal, a record is made of the offset/delay between each clock and the gps signal (which is also atomic clock based)

If you then subtract the delay of Cern from the delay of Gran Sasso you end up with the difference between the two clocks (and the signal time & its error).  As we know the signal propagation time and error very accurately (it is the basis of GPS) we can calculate the difference between the clocks.  Only real error introduced is through differences in atmospheric conditions (which can be covered by repeating regularly and at night/day), or and by the ephemeris error.  The max error for intercontinental long range common view is about 10 nanoseconds - for such a short baseline the major error (ephemeris) is lowered significantly

And frankly Geezer - scientific experimentation is very much about following instructions.  You need to be consistent in your operations; and when one area of expertise has developed a technique and it has been found to be accurate then you use that knowledge.  ie when a group of nuclear physicists want to know how to measure time over a great distance they use a  technique developed by the NIST/USNO, and it is checked and implemented by a national Metrology institute - so in effect they just follow instructions.  So as long as Gran Sasso followed the technique carefully and did not vary the protocol then the validity of the result and more importantly the error has already been shown by experts/academics.
« Last Edit: 03/12/2011 17:31:03 by imatfaal »
 

Offline CliffordK

  • Neilep Level Member
  • ******
  • Posts: 6321
  • Thanked: 3 times
  • Site Moderator
    • View Profile
We already know that the speed of light varies based on the medium.  And there is apparently some interaction of light with local space...  causing the space where the measurement is taken to influence the actual measurement of the speed of light.

So...
if there is an asymptotic maximum speed for particles in local-space, it isn't too surprising to find particles that interact less with what is around them, and thus travel slightly faster than light.

The big question I would have is whether all neutrinos from natural sources distant from Earth travel to Earth at the same speed, or perhaps they are dependent on the relative velocity of the source.
 

Offline Geezer

  • Neilep Level Member
  • ******
  • Posts: 8328
  • "Vive la résistance!"
    • View Profile
And frankly Geezer - scientific experimentation is very much about following instructions.  You need to be consistent in your operations; and when one area of expertise has developed a technique and it has been found to be accurate then you use that knowledge.  ie when a group of nuclear physicists want to know how to measure time over a great distance they use a  technique developed by the NIST/USNO, and it is checked and implemented by a national Metrology institute - so in effect they just follow instructions.  So as long as Gran Sasso followed the technique carefully and did not vary the protocol then the validity of the result and more importantly the error has already been shown by experts/academics.

Fully agree that a lot of it is simply following the instructions, and very rigorously at that. That usually works very well, but when there is an anomaly, everything is up for grabs. Anomalies (real or apparent) force scientists to ask very uncomfortable questions that move science forward.

My only point was that if nobody ever challenged the "instructions", the Earth would still be at the centre of the Universe.
 

Offline Geezer

  • Neilep Level Member
  • ******
  • Posts: 8328
  • "Vive la résistance!"
    • View Profile
Metrology institutes around the world have long established the common view GPS method of synchronization/comparison.  This algorithm and protocol for synchronizing geographically remote clocks is not new and has been exhaustively tested

I'm sure these guys know what they are doing, but I found it slightly disconcerting that the description says things like "A and B, receive a one-way signal simultaneously"

If they know it's simultaneous, why bother? Seems a bit circular to me, but then, I'm well known for being nitpicky.
 

Offline imatfaal

  • Neilep Level Member
  • ******
  • Posts: 2787
  • rouge moderator
    • View Profile
Clifford - not quite sure of the effects you are talking about - could you elaborate?  The problem with measuring neutrinos is that we are so bad at detecting them that we can only be certain of a source in very rare circumstances.  Supernova SN1987a is one such event - as Syhprum explained the neutrinos arrived a few hours before the light did, it is possible we missed the "othersort of neutrino" that were superluminal.  But to work out how fast Neutrinos travel in space we need to know precisely what caused them and when/where that was - and there are precious few opportunities for that.
 

Offline imatfaal

  • Neilep Level Member
  • ******
  • Posts: 2787
  • rouge moderator
    • View Profile
Metrology institutes around the world have long established the common view GPS method of synchronization/comparison.  This algorithm and protocol for synchronizing geographically remote clocks is not new and has been exhaustively tested

I'm sure these guys know what they are doing, but I found it slightly disconcerting that the description says things like "A and B, receive a one-way signal simultaneously"

If they know it's simultaneous, why bother? Seems a bit circular to me, but then, I'm well known for being nitpicky.

Doesn't say they receive the same bit of the signal simultaneously - or that the signals are synchronized.

If Mrs Geezer puts on her favourite Balck Sabbath album at full volume at the other end of the house it is quite acceptable to say that you and she are listening simultaneously - although with the finite speed of sound, combined with the magnificence of geezer manor she might hear each of OO's dulcet tones a few seconds before you. 

In fact if you did a bit of measuring (distance, air pressure, humidity etc) you could tell which of your two clocks is slow.  ie you both look at the clocks in your respective rooms and note the time of the very last bit of Paranoid.

If you clocked it at 15 seconds exactly past the hour, and Mrs G at 10 seconds past exactly - Mrs G is 3.2 m from the stereo and you are 340 m in the other direction (it's a nice dry day at your beach house by the way and about 60F due to the aircon) - after you and Mrs G compare notes; you can work out that your clock is 4 seconds slower than Mrs G's.

Common view relies on a signal being received simultaneously - but possibly not in synch.  The fact that the message is the same - and you can the compare notes afterwards allows you to workout the difference in your clocks without worrying about synchronization.   The common view part allows you to remove the clock on the satellite from the equation - if I haven't screwed up, the above example would still work if your played Ozzie and friends at 45 or 78.  The only sources of error are where the satellites actually are (and we know that fairly well) - and the possibility that one leg of the signal gets bounced around a bit more than the other.  At 734 km baseline these errors reduce to fractions of a second  (2.3ns)
 

Offline Geezer

  • Neilep Level Member
  • ******
  • Posts: 8328
  • "Vive la résistance!"
    • View Profile
Metrology institutes around the world have long established the common view GPS method of synchronization/comparison.  This algorithm and protocol for synchronizing geographically remote clocks is not new and has been exhaustively tested

I'm sure these guys know what they are doing, but I found it slightly disconcerting that the description says things like "A and B, receive a one-way signal simultaneously"

If they know it's simultaneous, why bother? Seems a bit circular to me, but then, I'm well known for being nitpicky.

Doesn't say they receive the same bit of the signal simultaneously - or that the signals are synchronized.

If Mrs Geezer puts on her favourite Balck Sabbath album at full volume at the other end of the house it is quite acceptable to say that you and she are listening simultaneously - although with the finite speed of sound, combined with the magnificence of geezer manor she might hear each of OO's dulcet tones a few seconds before you. 

In fact if you did a bit of measuring (distance, air pressure, humidity etc) you could tell which of your two clocks is slow.  ie you both look at the clocks in your respective rooms and note the time of the very last bit of Paranoid.

If you clocked it at 15 seconds exactly past the hour, and Mrs G at 10 seconds past exactly - Mrs G is 3.2 m from the stereo and you are 340 m in the other direction (it's a nice dry day at your beach house by the way and about 60F due to the aircon) - after you and Mrs G compare notes; you can work out that your clock is 4 seconds slower than Mrs G's.

Common view relies on a signal being received simultaneously - but possibly not in synch.  The fact that the message is the same - and you can the compare notes afterwards allows you to workout the difference in your clocks without worrying about synchronization.   The common view part allows you to remove the clock on the satellite from the equation - if I haven't screwed up, the above example would still work if your played Ozzie and friends at 45 or 78.  The only sources of error are where the satellites actually are (and we know that fairly well) - and the possibility that one leg of the signal gets bounced around a bit more than the other.  At 734 km baseline these errors reduce to fractions of a second  (2.3ns)

Ah! Right, I see what you mean. It might have been better if they had left out "simultaneous" and said "A and B receive the same transmission" or similar.

How accurately do the distances have to be known for this to work, or does it not require any knowledge of distance? Or does the distance measurement depend on a highly accurate common view of time?
 

Offline CliffordK

  • Neilep Level Member
  • ******
  • Posts: 6321
  • Thanked: 3 times
  • Site Moderator
    • View Profile
As far as clocks.
It would be easy enough to put the two clocks together.
Synchronize them.
Separate them and run the experiment.
Bring them back together and verify that they are still in sync.

Or, perhaps have a third physical "master clock", that would be moved from one location to the other.
And, then just repeatedly verify that the "slave clocks" on each end match the master clock.

If jet aircraft affect atomic clocks, then carry them in shielded containers in trucks, trains, or cargo ships on the ground.
 

Offline syhprum

  • Neilep Level Member
  • ******
  • Posts: 3823
  • Thanked: 19 times
    • View Profile
It is not Jet aircraft that disturb atomic clocks but the reduced gravity at altitude and the speed of travel cause time dilation effects which of course you cannot shield against.
 

Offline imatfaal

  • Neilep Level Member
  • ******
  • Posts: 2787
  • rouge moderator
    • View Profile
As far as clocks.
It would be easy enough to put the two clocks together.
Synchronize them.
Separate them and run the experiment.
Bring them back together and verify that they are still in sync.

Or, perhaps have a third physical "master clock", that would be moved from one location to the other.
And, then just repeatedly verify that the "slave clocks" on each end match the master clock.

If jet aircraft affect atomic clocks, then carry them in shielded containers in trucks, trains, or cargo ships on the ground.

Clifford

I think Syhprum has covered most of points in your post - however one other thing, they did move an accurate clock between the two.  I would recommend a quick scan of the experimental write up (Mike helpfully posted it above) you can read about the timing on pages 7-9.  Basically common view synchronization is using a third clock - ie the one on the gps satellite

As Geezer and I mentioned above - when you want great accuracy in a technique you go to those who have great expertise, and the way that the metrologists do this synchronization of clocks is incredibly accurate.  The Atomic clocks spread over the USA are accurate to within 1 ns of each other - bearing in mind that some are in Flagstaff Arizona and others are at sea-level you cannot just move one to another as a clock at 2000m and one at sea-level will run at different rates
 

Offline imatfaal

  • Neilep Level Member
  • ******
  • Posts: 2787
  • rouge moderator
    • View Profile
Metrology institutes around the world have long established the common view GPS method of synchronization/comparison.  This algorithm and protocol for synchronizing geographically remote clocks is not new and has been exhaustively tested

I'm sure these guys know what they are doing, but I found it slightly disconcerting that the description says things like "A and B, receive a one-way signal simultaneously"

If they know it's simultaneous, why bother? Seems a bit circular to me, but then, I'm well known for being nitpicky.

Doesn't say they receive the same bit of the signal simultaneously - or that the signals are synchronized.

If Mrs Geezer puts on her favourite Balck Sabbath album at full volume at the other end of the house it is quite acceptable to say that you and she are listening simultaneously - although with the finite speed of sound, combined with the magnificence of geezer manor she might hear each of OO's dulcet tones a few seconds before you. 

In fact if you did a bit of measuring (distance, air pressure, humidity etc) you could tell which of your two clocks is slow.  ie you both look at the clocks in your respective rooms and note the time of the very last bit of Paranoid.

If you clocked it at 15 seconds exactly past the hour, and Mrs G at 10 seconds past exactly - Mrs G is 3.2 m from the stereo and you are 340 m in the other direction (it's a nice dry day at your beach house by the way and about 60F due to the aircon) - after you and Mrs G compare notes; you can work out that your clock is 4 seconds slower than Mrs G's.

Common view relies on a signal being received simultaneously - but possibly not in synch.  The fact that the message is the same - and you can the compare notes afterwards allows you to workout the difference in your clocks without worrying about synchronization.   The common view part allows you to remove the clock on the satellite from the equation - if I haven't screwed up, the above example would still work if your played Ozzie and friends at 45 or 78.  The only sources of error are where the satellites actually are (and we know that fairly well) - and the possibility that one leg of the signal gets bounced around a bit more than the other.  At 734 km baseline these errors reduce to fractions of a second  (2.3ns)

Ah! Right, I see what you mean. It might have been better if they had left out "simultaneous" and said "A and B receive the same transmission" or similar.

How accurately do the distances have to be known for this to work, or does it not require any knowledge of distance? Or does the distance measurement depend on a highly accurate common view of time?

Two distances involved - not sure which you are asking about. 

Distance to satellite. You do need to know where the satellite is and the distance (and more importantly the error) to each of the base-stations; but the speed of the signal is so damn high that even estimates with high ephemeris error will lead to a nano-second error at such a short baseline

Distance on baseline.  As you know the distance to a common known point (the gps sat) then you do know the baseline - but it is not part of the calculation

I am not aware of the error algorithms - but everything I have read suggested that at over 3000km you need to start being careful of errors close to 10ns.  But 730km is actually quite a short baseline distance for this technique and the max error is 2.3ns.  The subtraction of one data set from the other means that errors are cancelled not accrued - most of the error in a signal coming from a satellite 22000 km away to two posts 730km apart will be the same.
 

Offline syhprum

  • Neilep Level Member
  • ******
  • Posts: 3823
  • Thanked: 19 times
    • View Profile
In the days before telegraphs etc London watch makers had their timepieces synchronised by a courier carrying a watch synchronised at Greenwich to their establishments.
 

Offline Airthumbs

  • Hero Member
  • *****
  • Posts: 958
  • Personal Text
    • View Profile
Bulk jumpers  :o
 

Offline Geezer

  • Neilep Level Member
  • ******
  • Posts: 8328
  • "Vive la résistance!"
    • View Profile
Two distances involved - not sure which you are asking about. 

Distance to satellite. You do need to know where the satellite is and the distance (and more importantly the error) to each of the base-stations; but the speed of the signal is so damn high that even estimates with high ephemeris error will lead to a nano-second error at such a short baseline

Distance on baseline.  As you know the distance to a common known point (the gps sat) then you do know the baseline - but it is not part of the calculation

I am not aware of the error algorithms - but everything I have read suggested that at over 3000km you need to start being careful of errors close to 10ns.  But 730km is actually quite a short baseline distance for this technique and the max error is 2.3ns.  The subtraction of one data set from the other means that errors are cancelled not accrued - most of the error in a signal coming from a satellite 22000 km away to two posts 730km apart will be the same.

Thanks!

What I'm (sort of) getting at is that, for this experiment, both the distance and time have to be very accurately known. However, if I understand properly how this works, the accuracy of the time synchronization depends on a very accurate measurement of the baseline. If the baseline is a bit off I think it will introduce an error into the time synchronization, although it's probably very small.

It's probably highly unlikely that would account for the observed results, but it might be a contributing factor.

BTW, you only know the distance from the satellite to the receiver if they have a common view of time, and the speed of the signal really has nothing to do with it.
 

Offline imatfaal

  • Neilep Level Member
  • ******
  • Posts: 2787
  • rouge moderator
    • View Profile
Two distances involved - not sure which you are asking about. 

Distance to satellite. You do need to know where the satellite is and the distance (and more importantly the error) to each of the base-stations; but the speed of the signal is so damn high that even estimates with high ephemeris error will lead to a nano-second error at such a short baseline

Distance on baseline.  As you know the distance to a common known point (the gps sat) then you do know the baseline - but it is not part of the calculation

I am not aware of the error algorithms - but everything I have read suggested that at over 3000km you need to start being careful of errors close to 10ns.  But 730km is actually quite a short baseline distance for this technique and the max error is 2.3ns.  The subtraction of one data set from the other means that errors are cancelled not accrued - most of the error in a signal coming from a satellite 22000 km away to two posts 730km apart will be the same.

Thanks!

What I'm (sort of) getting at is that, for this experiment, both the distance and time have to be very accurately known.
  Completely - it's the be all and end all

Quote
However, if I understand properly how this works, the accuracy of the time synchronization depends on a very accurate measurement of the baseline. If the baseline is a bit off I think it will introduce an error into the time synchronization, although it's probably very small.
You need to know the 3d coordinates of each basestation very accurately.  This the GPS system, using multiple view, is very good at this and there is a claimed accuracy - that I do not think many experts in the field argue with - of 2cm. This allows you to calculate your baseline.  It also allows you to calculate the errors in the common single view time synchronization of the two clocks

Quote
It's probably highly unlikely that would account for the observed results, but it might be a contributing factor.
The bulk of the acknowledged error - and possibly the source for more - is the measurement from the GPS basestation to the actual receivers.  This was old fashioned manual survey and the 10km is uncertain by 20cm m/l.  But the time difference between estimated arrival and actual arrival was 60ns which dwarfs the error margins .

Quote
BTW, you only know the distance from the satellite to the receiver if they have a common view of time, and the speed of the signal really has nothing to do with it.
  - it means that errors in position of the gps basestations and the ephemeris error of the gps-sat do not translate into large differential time lags that screw up your common view synchronization
 

Offline CliffordK

  • Neilep Level Member
  • ******
  • Posts: 6321
  • Thanked: 3 times
  • Site Moderator
    • View Profile
How easy would it be to move either the transmitter or receiver to New Zealand & repeat the experiment?
 

Offline yor_on

  • Naked Science Forum GOD!
  • *******
  • Posts: 12001
  • Thanked: 4 times
  • (Ah, yes:) *a table is always good to hide under*
    • View Profile
Then you will have to consider tectonic movements too :)
And sheep's getting in the way (or is that kangaroos?)
 

Offline imatfaal

  • Neilep Level Member
  • ******
  • Posts: 2787
  • rouge moderator
    • View Profile
How easy would it be to move either the transmitter or receiver to New Zealand & repeat the experiment?

You could start again from scratch.  You need a hi-power proton synchrotron - a graphite block and a km long tunnel - the tunnel is directional so pointing it through the earth would not be easy.  The receptors are also not moveable.  You could rebuild new ones with a longer baseline - but there is really no need; if the experiment methodology was misconceived then that can be shown in CERN/OPERA, and will also be shown when FermiLab/MINOS give their results next year.  If the accuracy was poor - this can be rechecked with different protocols and other staff.  The error was small compared to the difference found - the problem isn't with significance of results , its the results themselves.  A longer baseline would be great - but not necessary yet.

Then you will have to consider tectonic movements too :)
And sheep's getting in the way (or is that kangaroos?)
Sheep in NZ Roos in OZ
Tectonic movement will not make a difference.  The positions of the GPS basestations is calculated as a point in three dimensional space - the distance between them can be calculated very accurately at an almost instantaneous rate.  The baseline distance is not worked out by plotting each basestation on a globe and then working out the cord distance - the system of GPS-sats create a 3d coordinate system and you can work out a distance. 

You will need to take into account the rotation of the earth - which will affect the position of the basestations - but not the straightness of the neutrino beam. 
 

Offline Geezer

  • Neilep Level Member
  • ******
  • Posts: 8328
  • "Vive la résistance!"
    • View Profile
Two distances involved - not sure which you are asking about. 

Distance to satellite. You do need to know where the satellite is and the distance (and more importantly the error) to each of the base-stations; but the speed of the signal is so damn high that even estimates with high ephemeris error will lead to a nano-second error at such a short baseline

Distance on baseline.  As you know the distance to a common known point (the gps sat) then you do know the baseline - but it is not part of the calculation

I am not aware of the error algorithms - but everything I have read suggested that at over 3000km you need to start being careful of errors close to 10ns.  But 730km is actually quite a short baseline distance for this technique and the max error is 2.3ns.  The subtraction of one data set from the other means that errors are cancelled not accrued - most of the error in a signal coming from a satellite 22000 km away to two posts 730km apart will be the same.

Thanks!

What I'm (sort of) getting at is that, for this experiment, both the distance and time have to be very accurately known.
  Completely - it's the be all and end all

Quote
However, if I understand properly how this works, the accuracy of the time synchronization depends on a very accurate measurement of the baseline. If the baseline is a bit off I think it will introduce an error into the time synchronization, although it's probably very small.
You need to know the 3d coordinates of each basestation very accurately.  This the GPS system, using multiple view, is very good at this and there is a claimed accuracy - that I do not think many experts in the field argue with - of 2cm. This allows you to calculate your baseline.  It also allows you to calculate the errors in the common single view time synchronization of the two clocks

Quote
It's probably highly unlikely that would account for the observed results, but it might be a contributing factor.
The bulk of the acknowledged error - and possibly the source for more - is the measurement from the GPS basestation to the actual receivers.  This was old fashioned manual survey and the 10km is uncertain by 20cm m/l.  But the time difference between estimated arrival and actual arrival was 60ns which dwarfs the error margins .

Quote
BTW, you only know the distance from the satellite to the receiver if they have a common view of time, and the speed of the signal really has nothing to do with it.
  - it means that errors in position of the gps basestations and the ephemeris error of the gps-sat do not translate into large differential time lags that screw up your common view synchronization


I thought I read that they actually did a survey transit to determine the positions. Surely that could introduce some serious errors, or did I get that wrong?
 

Offline CliffordK

  • Neilep Level Member
  • ******
  • Posts: 6321
  • Thanked: 3 times
  • Site Moderator
    • View Profile
You will need to take into account the rotation of the earth - which will affect the position of the basestations - but not the straightness of the neutrino beam. 

Ahhh...  so if you aligned it on the equator, say from South America to New Guinea, then measured the deflection due to the Coriolis effect, you could make an exceptionally accurate real-time geo-clock.  That is, assuming everything could be monitored in real-time.
 

Offline Geezer

  • Neilep Level Member
  • ******
  • Posts: 8328
  • "Vive la résistance!"
    • View Profile
 

Offline imatfaal

  • Neilep Level Member
  • ******
  • Posts: 2787
  • rouge moderator
    • View Profile

I thought I read that they actually did a survey transit to determine the positions. Surely that could introduce some serious errors, or did I get that wrong?

The survey was merely to determine the offset of the detectors and the sources from the two GPS base-stations.  It was about 10km of the total of 730km - but the error in that survey was the vast majority of the entire error of the set up.

re Syhprum's unit post - I hope and pray that, for the sake of scientific dignity, that it doesn't turn out that one bozzo was using mm and the other bozzo was using cm and that if they had both used the same unit the 60ns/18m disappears
« Last Edit: 06/12/2011 10:56:31 by imatfaal »
 

Offline Geezer

  • Neilep Level Member
  • ******
  • Posts: 8328
  • "Vive la résistance!"
    • View Profile

I thought I read that they actually did a survey transit to determine the positions. Surely that could introduce some serious errors, or did I get that wrong?

The survey was merely to determine the offset of the detectors and the sources from the two GPS base-stations.  It was about 10km of the total of 730km - but the error in that survey was the vast majority of the entire error of the set up.

re Syhprum's unit post - I hope and pray that, for the sake of scientific dignity, that it doesn't turn out that one bozzo was using mm and the other bozzo was using cm and that if they had both used the same unit the 60ns/18m disappears

Perhaps the surveyors were distracted by a flock of particularly attractive sheep?

I think I figured the difference comes out at around 27 ppm, so a little bit of extra coax here or even a few kinks in a cable there and Bob's your uncle, although I'm sure they've gone over this till they are completely sick of it.

BTW, it would only take about 6m of cable (even less if it's optical fibre) to account for that time difference.
 

Offline syhprum

  • Neilep Level Member
  • ******
  • Posts: 3823
  • Thanked: 19 times
    • View Profile
BTW I think information travels faster in the type of optical cable used for long distance circuits that it does in coaxial cable. best check
 

The Naked Scientists Forum


 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums