Re: [time-nuts] New tide gauge uses GPS signals to measure sea level change
On 28 May 2014 14:06, Tom Holmes thol...@woh.rr.com wrote: Which begs the question: just where the heck, exactly, is the center of the Earth given that it is in the 'middle' of a molten and dynamic core. I always thought that the centre was molten. There was something on the TV in the UK a couple of weeks ago which seemed to indicate that the centre is actually solid, although around that it is molten. I did not see it all and was only watching bits of it, but it would appear some female researcher had proven this. The proof appeared to be based on the time of travel of shock wases from earthquakes and the different speed they travel through solid and liquid. Dave. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] New tide gauge uses GPS signals to measure sea level change
On 5/30/14, 2:41 AM, Dr. David Kirkby wrote: On 28 May 2014 14:06, Tom Holmes thol...@woh.rr.com wrote: Which begs the question: just where the heck, exactly, is the center of the Earth given that it is in the 'middle' of a molten and dynamic core. I always thought that the centre was molten. There was something on the TV in the UK a couple of weeks ago which seemed to indicate that the centre is actually solid, although around that it is molten. Molten, but it's a composite material under a lot of pressure, so the transition between liquid and solid isn't like between ice and water. Think cold peanut butter. I did not see it all and was only watching bits of it, but it would appear some female researcher had proven this. The proof appeared to be based on the time of travel of shock wases from earthquakes and the different speed they travel through solid and liquid. Seismic evidence is how they knew it was liquid in the first place. As you get better at doing the models, and getting better time measurements of the seismic propagation with higher performance seismometers, you can get a better model. Combine that with precise orbit determination (using accurate measurements of time and frequency from orbits) which allows accurate gravity models (e.g. GRACE and GRACE-Follow-On) Dave. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] New tide gauge uses GPS signals to measure sea level change
[Structure of Earth's core] jim...@earthlink.net said: Molten, but it's a composite material under a lot of pressure, so the transition between liquid and solid isn't like between ice and water. Think cold peanut butter. Seismic evidence is how they knew it was liquid in the first place. As you get better at doing the models, and getting better time measurements of the seismic propagation with higher performance seismometers, you can get a better model. There was an article in Scientific American back in the early 1970s discussing the structure of the Earth and all the tricks the seismologists used to figure things out. I remember a diagram of the cross section of the Earth with a blizzard of seismic paths, bending and bouncing at each boundary. In that time frame, there was a lot of money for seismic research. It was a key part of the test ban treaties. What did seismologists use for timing back then? -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] New tide gauge uses GPS signals to measure sea level change
On 5/30/14, 3:00 PM, Hal Murray wrote: [Structure of Earth's core] jim...@earthlink.net said: Molten, but it's a composite material under a lot of pressure, so the transition between liquid and solid isn't like between ice and water. Think cold peanut butter. Seismic evidence is how they knew it was liquid in the first place. As you get better at doing the models, and getting better time measurements of the seismic propagation with higher performance seismometers, you can get a better model. There was an article in Scientific American back in the early 1970s discussing the structure of the Earth and all the tricks the seismologists used to figure things out. I remember a diagram of the cross section of the Earth with a blizzard of seismic paths, bending and bouncing at each boundary. In that time frame, there was a lot of money for seismic research. It was a key part of the test ban treaties. What did seismologists use for timing back then? A good wristwatch? Most of the work was done with conventional ink on graph paper drum recorders, and the sync was probably done with some sort of conventional derived from national time reference source: WWV or similar in the US. It's not like you need nanosecond precision when you're looking at propagation times of minutes. P wave propagates at about 5 km/sec S wave propagates at about 3 km/sec That's enough difference that you can tell how far the epicenter is from you in a local earthquake. If it's close (within 10km), you feel the earthquake as a single event, because the P wave arrives in a couple seconds and the S wave is a second later, while the shaking is still going on (unless it's a very small quake). If it's farther away (say 50km), then you feel two separate events (50 sec vs 80 sec). I would say that most people who live in Southern California for a while and are somewhat aware of it can tell the rough distance and magnitude of an earthquake because of this, even if they don't know why. Duration of shaking correlates well with magnitude. The short thump is probably a 2 or 3 (was that an earthquake or a sonic boom or someone dropping a truck load of something), a 4 will maybe be a rumble or a couple sways, a 5 is we're definitely having an earthquake because it lasts distinctly long enough for you to realize that something's going on that's not a short event, and a 6 is in the seems to last forever category. So if you get a crack, thump, rattle followed a few seconds later by the lamps or cupboard door swinging a bit, you say hey, a 3.5 10 miles away The P wave has a distinct crack and feels short to me, and the S (shear, transverse to propagation direction) wave is more the rolling and swaying (depending on the direction of motion). It's kind of like counting seconds between lightning flash and thunder (short duration event, delay, long duration event) In any case, to propagate the 10,000-15,000 km across the earth takes the better part of an hour. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] New tide gauge uses GPS signals to measure sea level change
Which begs the question: just where the heck, exactly, is the center of the Earth given that it is in the 'middle' of a molten and dynamic core. Are the satellite orbits so stable and/or measurable around the center of gravitational pull that the location can be determined from that? Where is the reference point? Is Archimedes fulcrum for moving the planet nearby? This would seem to play into the accuracy of the location of the GPS satellites at any given time-hack. Tom Holmes, N8ZM -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Chris Albertson Sent: Wednesday, May 28, 2014 12:22 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] New tide gauge uses GPS signals to measure sea level change On 5/27/14, 10:24 AM, Brooke Clarke wrote: This is one of the problems I have with the claim that sea level is rising at 2mm per year. i.e. how well can they back out the plate movement in historical tide gauge records? Let's assume they are NOT good at this and are working with factor of two error.All you need to know to see there is a problem is the order of magnitude of the trend. It's like if someone says the house is on fire. We have to get out and then you argue no it's not because you've got the rate of combustion off by a factor of 2.73. Small factors don't change the practical result. 2mm/yr is a small and very conservative estimate. A better one that reflects current conditions is nearly 4mm/yr. But the worry is that the rate is not constant and there is some positive feedback. That seems to be the case but it will take 20 years to really know for sure. BACK ON TOPIC... What does it take to measure ones distance from the center of the Earth accurately enough to detect geological movement in a reasonable amount of time? Measuring distance really is, I think a time nut problem as I bet it involves measuring radio waves. -- Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] New tide gauge uses GPS signals to measure sea level change
On 5/28/14, 6:04 AM, Tom Holmes wrote: Which begs the question: just where the heck, exactly, is the center of the Earth given that it is in the 'middle' of a molten and dynamic core. Are the satellite orbits so stable and/or measurable around the center of gravitational pull that the location can be determined from that? Where is the reference point? Is Archimedes fulcrum for moving the planet nearby? This would seem to play into the accuracy of the location of the GPS satellites at any given time-hack. T There's a group of people around the world who worry about this kind of thing. There's a difference between the barycenter (the center of mass) and the Earth centered coordinate system orgins. In fact, there's somewhat of a dispute going on about whether we should update from WGS84: that coordinate system was defined to be the same (within measurement precision) as the previous origin, but now within measurement precision has gotten smaller, and there's a difference. But that raises a question of whether we need to redo all the state plane coordinate transformations, since they're in terms of WGS84. As to whether the satellite orbits are stable/measurable, the answer is most certainly yes. It was fairly precise measurements of satellite signals in the 60s that led to the changing of the geoid from an ellipsoid to something more pear shaped. Precise measurements of satellite orbits and Doppler rates is how we infer the internal structure of the outer planets. A typical measurement uncertainty is a few cm and a few mm/sec for a probe at Jupiter. One generally does some sort of fit to a gravitational model with some number of spherical harmonic terms (ten or twenty, as I recall). The ephemeris for GPS takes this into account, so if you also account for things like the ionosphere, you can determine your position to cm accuracy (absolute). Note well that the GPS ephemeris doesn't contain all the spherical harmonics and effects.. what they do is reload the ephemeris periodically with fewer terms so that you can use it for a few days (as I recall, for satelites in reasonable orbits (not too low), the uncertainty in satellite position after a day is on the order of meters. Some satellites are particularly stable: QuikScat was in a special orbit, and as I recall, after a year, it was only a few hundred meters from where the year old ephemeris predicted it would be. The orbit height (803 km) had changed maybe 1 km. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] New tide gauge uses GPS signals to measure sea level change
On 5/27/14, 9:21 PM, Chris Albertson wrote: On 5/27/14, 10:24 AM, Brooke Clarke wrote: BACK ON TOPIC... What does it take to measure ones distance from the center of the Earth accurately enough to detect geological movement in a reasonable amount of time? Measuring distance really is, I think a time nut problem as I bet it involves measuring radio waves. Considering that the Pacific Plate is moving north at about 2cm/year, that is easily detectable with GPS and post processing. Somebody in Southern California should be able to measure it without going to too exotic an effort: you need a GPS receiver that can put out the observables in a gipsy file, and then post process through JPL's website. The Ventura Anticline is still rising at about the same rate. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] New tide gauge uses GPS signals to measure sea level change
Thanks Jim. So if, just for fun since this is time-nuts after all, I wanted to make a similar measurement in my back yard here in the relatively stable Ohio, would I be able rig something up to monitor the position changes? Obviously a lot of averaging of GPS position data would be needed but I'm not sure my Z3801 or any of my navigation receivers have the necessary resolution to see even 10 mm. Tom Holmes, N8ZM -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Jim Lux Sent: Wednesday, May 28, 2014 4:54 PM To: time-nuts@febo.com Subject: Re: [time-nuts] New tide gauge uses GPS signals to measure sea level change On 5/28/14, 6:04 AM, Tom Holmes wrote: Which begs the question: just where the heck, exactly, is the center of the Earth given that it is in the 'middle' of a molten and dynamic core. Are the satellite orbits so stable and/or measurable around the center of gravitational pull that the location can be determined from that? Where is the reference point? Is Archimedes fulcrum for moving the planet nearby? This would seem to play into the accuracy of the location of the GPS satellites at any given time-hack. T There's a group of people around the world who worry about this kind of thing. There's a difference between the barycenter (the center of mass) and the Earth centered coordinate system orgins. In fact, there's somewhat of a dispute going on about whether we should update from WGS84: that coordinate system was defined to be the same (within measurement precision) as the previous origin, but now within measurement precision has gotten smaller, and there's a difference. But that raises a question of whether we need to redo all the state plane coordinate transformations, since they're in terms of WGS84. As to whether the satellite orbits are stable/measurable, the answer is most certainly yes. It was fairly precise measurements of satellite signals in the 60s that led to the changing of the geoid from an ellipsoid to something more pear shaped. Precise measurements of satellite orbits and Doppler rates is how we infer the internal structure of the outer planets. A typical measurement uncertainty is a few cm and a few mm/sec for a probe at Jupiter. One generally does some sort of fit to a gravitational model with some number of spherical harmonic terms (ten or twenty, as I recall). The ephemeris for GPS takes this into account, so if you also account for things like the ionosphere, you can determine your position to cm accuracy (absolute). Note well that the GPS ephemeris doesn't contain all the spherical harmonics and effects.. what they do is reload the ephemeris periodically with fewer terms so that you can use it for a few days (as I recall, for satelites in reasonable orbits (not too low), the uncertainty in satellite position after a day is on the order of meters. Some satellites are particularly stable: QuikScat was in a special orbit, and as I recall, after a year, it was only a few hundred meters from where the year old ephemeris predicted it would be. The orbit height (803 km) had changed maybe 1 km. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] New tide gauge uses GPS signals to measure sea level change
thol...@woh.rr.com said: I'm not sure my Z3801 or any of my navigation receivers have the necessary resolution to see even 10 mm. In normal operation (post survey), a Z3801A knows the location and uses that to work out a better time and/or the time with fewer satellites. So you won't be getting any new location data. It might be interesting to set one up in a loop to do a survey, grab the location, then repeat. After a day or week, you could average the locations and/or compute std dev and such. -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] New tide gauge uses GPS signals to measure sea level change
Hal, you bring up an interesting point: Is the receiver in a Z3801 inherently more accurate in position reporting than the receiver in an Adafruit? Somehow I doubt it, if for no other reason than the improvements in technology. (Excluding any programming errors that may or may not exist in the MT3339.) What the Z3801 has that the 3339 doesn't have is code to accurately calculate the PPS timing error based on a fixed position. So, if my reasoning is correct, wouldn't you do better running the Adafruit X number of days and doing an average of the position over that period? Bob From: Hal Murray hmur...@megapathdsl.net To: Discussion of precise time and frequency measurement time-nuts@febo.com Cc: hmur...@megapathdsl.net Sent: Wednesday, May 28, 2014 4:32 PM Subject: Re: [time-nuts] New tide gauge uses GPS signals to measure sea level change thol...@woh.rr.com said: I'm not sure my Z3801 or any of my navigation receivers have the necessary resolution to see even 10 mm. In normal operation (post survey), a Z3801A knows the location and uses that to work out a better time and/or the time with fewer satellites. So you won't be getting any new location data. It might be interesting to set one up in a loop to do a survey, grab the location, then repeat. After a day or week, you could average the locations and/or compute std dev and such. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] New tide gauge uses GPS signals to measure sea level change
I'll have to run a quick calculation on the data it presents to see if it is good enough to use. Tom Holmes, N8ZM -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Hal Murray Sent: Wednesday, May 28, 2014 5:33 PM To: Discussion of precise time and frequency measurement Cc: hmur...@megapathdsl.net Subject: Re: [time-nuts] New tide gauge uses GPS signals to measure sea level change thol...@woh.rr.com said: I'm not sure my Z3801 or any of my navigation receivers have the necessary resolution to see even 10 mm. In normal operation (post survey), a Z3801A knows the location and uses that to work out a better time and/or the time with fewer satellites. So you won't be getting any new location data. It might be interesting to set one up in a loop to do a survey, grab the location, then repeat. After a day or week, you could average the locations and/or compute std dev and such. -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] New tide gauge uses GPS signals to measure sea level change
On 5/28/14, 2:11 PM, Tom Holmes wrote: Thanks Jim. So if, just for fun since this is time-nuts after all, I wanted to make a similar measurement in my back yard here in the relatively stable Ohio, would I be able rig something up to monitor the position changes? Obviously a lot of averaging of GPS position data would be needed but I'm not sure my Z3801 or any of my navigation receivers have the necessary resolution to see even 10 mm. T Sure it can.. you don't do it by averaging lat/lons, though... What you need is to program your receiver to give you the raw observables (someone on the list can point you to how you do this), and then you need to get them in what's called RINEX file format. You submit your RINEX formatted files to JPL's web based GIPSY processing site (wait at least a week or two after you collect your data, so they have the precise GPS ephemeris figured out), and get your geodetic data back. As I recall, given your position, they have post hoc ionospheric calculations from recordings made at high precision receivers near you which they can use to compensate your measurements, etc. I'm oversimplifying a lot of the above process out of ignorance, but basically that's how it's done. I have been told that it's pretty easy to see things like solid earth tides with a fairly simple system. Mind you fairly simple to these guys might mean a high quality choke ring on a geodetic pedestal with a precision invar rod driven into the bedrock within a steel protective casing. but it could also mean a helibowl antenna with the helix wound on a plastic solo cup stuck inside an aluminum kitchen stove burner liner. One of the longest continuously running geodetic receiver stations is at JPL and is basically a DM choke ring sitting on the ground on the edge of a hill. (this is referred to as the Aries Site*, for some reason) http://goo.gl/maps/mXTcK in the lower right corner of the dirt area south of the parking lot area, you'll see a dark dot in the middle of a lighter round thing: that's the antenna. The trailer at the top of the image is where the receiver is, and the coax is running along the east side of the parking lot. Contrary to the copyright date at the bottom, this image is at least 2 years old, because they've moved the trailer away, and the receiver is now in a little building across the street (on the west side of the image). *It might well be that initial testing of ARIES (a VLBI experiment) http://ipnpr.jpl.nasa.gov/progress_report2/42-26/26G.PDF was done up there. There's a couple surveyed concrete pads with steel mounts and benchmarks. The DSN report was from 1975, so it's substantially before my time at the lab (as well as most people around), although there are some familiar names in that paper (Spitzmesser has dozens of GPS related pubs) https://ia600505.us.archive.org/3/items/nasa_techdoc_19840071052/19840071052.pdf has a picture of the smaller 4 meter system (it's more portable than the 9 meter system, and claims better performance because of the liquid helium cooled maser, portable cesium clock, etc.) I guess portable is relative, especially when you talk to DSN folks who think in terms of 70 meter antennas. (For scale..the building in the background of the picture is Bldg 180 at JPL, the main admin building, and is 9 stories tall. A 70 meter DSN antenna is taller than that building) what's fascinating is that today, you can buy, for less than $20, a low noise block converter for 12 GHz (Ku-band) with a noise temperature 20K. But back in the early 70s, pre-GPS days, you had to be a serious time-nut... ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] New tide gauge uses GPS signals to measure sea level change
On Wed, May 28, 2014 at 6:28 PM, Jim Lux jim...@earthlink.net wrote: What you need is to program your receiver to give you the raw observables (someone on the list can point you to how you do this), and then you need to get them in what's called RINEX file format. You submit your RINEX formatted files to JPL's web based GIPSY processing site (wait at least a week or two after you collect your data, so they have the precise GPS ephemeris figured out), and get your geodetic data back. The JPL system says it will do single frequency in the future so for now I think you need a dual frequency(L1/L2) receiver. The Canadian Geomatics group does single frequency and of course you can do your own post-processing. RTKLIB (I think first mentioned here in 2011) seems to be popular. PPP is why I have LEA-6T and NEO-7P receivers. RTKLIB says it can locate my antenna within a 2x5x10 cm volume given a few days of data. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] New tide gauge uses GPS signals to measure sea level change
Hi: Classical tide gauges measure the height of the water relative to the gauge. But since the gauge is attached to a tectonic plate it's elevation is changing. This is one of the problems I have with the claim that sea level is rising at 2mm per year. i.e. how well can they back out the plate movement in historical tide gauge records? The new system uses a pair of GPS antennas one pointed up and the other pointed down at the water. http://www.mynewsdesk.com/uk/chalmers/pressreleases/new-tide-gauge-uses-gps-signals-to-measure-sea-level-change-998041?utm_source=rssutm_medium=rssutm_campaign=Subscriptionutm_content=pressrelease -- Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html http://www.prc68.com/I/DietNutrition.html ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] New tide gauge uses GPS signals to measure sea level change
On 5/27/14, 10:24 AM, Brooke Clarke wrote: Hi: Classical tide gauges measure the height of the water relative to the gauge. But since the gauge is attached to a tectonic plate it's elevation is changing. This is one of the problems I have with the claim that sea level is rising at 2mm per year. i.e. how well can they back out the plate movement in historical tide gauge records? Quite well. This is what geodesy specialists (geodesists?) do for a living. There's guys and gals at JPL who measure the earth's rotational axis to fractions of a cm and sub microsecond (with a lot of averaging and accounting for all sorts of error and offset sources) I would look for instance, at the Topex/Jason things where they regularly measure sea surface height to mm accuracy (that's how they infer ocean temperature and El Nino.. warm water floats on top, etc.) One should also be aware that very precise altimetry has some constraints on the publishable data. Over small time and geographic scales one can see things like the wake of a submarine: the oceanographers call that noise that has to be removed: other people call that signal. In any case, I'd believe a general statement of mm of seal level change over a sufficient averaging interval. What's more important is why it rises (fresh water floats, so if you get a warm summer that melts lots of ice, you can get a layer of freshwater on top of the salt water. Keeping this time nutsy, there is some research on using reflections of gps signals to distinguish (e.g. you get a big reflection from the air/water surface, but you get smaller reflections from the fresh/salt interface, etc.) It's similar to the things you can do with trying to look for the complete correlation graph for a GPS signal, rather than just tracking the biggest peak. The new system uses a pair of GPS antennas one pointed up and the other pointed down at the water. http://www.mynewsdesk.com/uk/chalmers/pressreleases/new-tide-gauge-uses-gps-signals-to-measure-sea-level-change-998041?utm_source=rssutm_medium=rssutm_campaign=Subscriptionutm_content=pressrelease ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] New tide gauge uses GPS signals to measure sea level change
On 5/27/14, 10:24 AM, Brooke Clarke wrote: This is one of the problems I have with the claim that sea level is rising at 2mm per year. i.e. how well can they back out the plate movement in historical tide gauge records? Let's assume they are NOT good at this and are working with factor of two error.All you need to know to see there is a problem is the order of magnitude of the trend. It's like if someone says the house is on fire. We have to get out and then you argue no it's not because you've got the rate of combustion off by a factor of 2.73. Small factors don't change the practical result. 2mm/yr is a small and very conservative estimate. A better one that reflects current conditions is nearly 4mm/yr. But the worry is that the rate is not constant and there is some positive feedback. That seems to be the case but it will take 20 years to really know for sure. BACK ON TOPIC... What does it take to measure ones distance from the center of the Earth accurately enough to detect geological movement in a reasonable amount of time? Measuring distance really is, I think a time nut problem as I bet it involves measuring radio waves. -- Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
