[time-nuts] Hunting dark matter with GPS data
People in the list may be interested in replicating the work... Cheers, Aife http://www.sciencemag.org/news/2017/01/hunting-dark-matter-gps-data Hunting dark matter with GPS data By Adrian ChoJan. 30, 2017 , 2:30 PM WASHINGTON, D.C.—A team of physicists has used data from GPS satellites to hunt for dark matter, the mysterious stuff whose gravity appears to hold galaxies together. They found no signs of a hypothetical type of dark matter, which consists of flaws in the fabric of space called topological defects, the researchers reported here on Saturday at a meeting of the American Physical Society. But the physicists say they have vastly narrowed the characteristics for how the defects—if they exist—would interact with ordinary matter. Their findings show how surprisingly innovative—and, in this case, cheap—methods might be used to test new ideas of what dark matter might be. “It is so interesting and refreshing and exciting, and the cost is basically zero,” says Dmitry Budker, an experimental physicist at the Johannes Gutenberg University of Mainz in Germany, who was not involved in the work. “It’s basically the cost of the students analyzing the data.” Astrophysicists think that dark matter makes up 85% of all the matter in the universe. Yet so far they have inferred dark matter’s existence only from its gravitational pull. For decades, many physicists have tried to directly detect a promising candidate for particles of dark matter, so-called weakly interacting massive particles, or WIMPs. But enthusiasm is waning as ever-more-sensitive detectors have failed to find the particles floating through our galaxy and passing through Earth. So many physicists are thinking more broadly about what dark matter might be. For example, instead of a new subatomic particle, dark matter could be something far bigger and weirder: macroscopic faults in the vacuum of space called topological defects. Topological defects are best explained with an analogy to magnetic materials such as nickel. Nickel atoms act like little magnets themselves, and below a certain temperature, neighboring atoms tend to point in the same direction, so that their magnetic fields reinforce one another. But that orderly alignment can suffer defects if, for example, atoms in different regions point in different directions. When this happens, the regions meet along a craggy surface called a “domain wall,” which is one type of topological defect. There can be pointlike and linelike defects, too. A similar thing might happen in space itself. Some theories predict that empty space is filled with a quantum field. If that field interacts with itself, then, as the infant universe expanded and cooled, the field may have taken on a value or “phase,” which would be a bit like the direction in which nickel atoms point. Regions of space with different phases would then meet at domain walls. These domain walls would have energy and, through Einstein’s famous equivalence, E=mc2, mass. So they would generate gravity and could be dark matter. Now, Benjamin Roberts and Andrei Derevianko, two physicists at the University of Nevada in Reno, and their colleagues say they have performed the most stringent search yet for topological dark matter, using archival data from the constellation of 31 orbiting GPS satellites. Each satellite carries an atomic clock and broadcasts timing signals. Receivers on Earth use the timing information from multiple satellites to determine how far it is from each of them and, hence, its location. To use those data to search for dark matter, the researchers had to invoke another bit of speculative physics. Theory suggests that within a topological defect, the constants of nature will change. In particular, the passing of a topological defect should fiddle with the so-called fine structure constant, which determines the strength of the electromagnetic force and the precise frequency of radiation that an atom will absorb or emit as an electron in it jumps from one quantized energy level to another. But an atomic clock works by measuring just such a frequency. So were a GPS satellite to pass through a topological defect, the defect should cause the satellite’s atomic clock to skip a beat. One jump in one atomic clock wouldn’t be proof enough for topological defects. So the researchers looked for a stronger signal, the wave of time shifts that would sweep across the whole 50,000-kilometer-wide GPS network if Earth passed through a large domain wall as the galaxy rotates in its cloud of dark matter. Combing 16 years of GPS data, they found no evidence of a shift greater than half a nanosecond, Roberts told the meeting. They placed limits on the number of such topological defects and how strongly they interact with matter—limits that are up to six orders of magnitude more stringent than ones set by previous studies of supernova explosions. The researchers haven’t yet reached the limitations set by the clocks’ noise, Roberts reported,
Re: [time-nuts] Four hour cycle in GPS NMEA jitter
On Thu, 2017-03-23 at 08:28 +1300, Kiwi Geoff wrote: > On 3/22/17, Trent wrote: > > https://goo.gl/photos/JZhBbFKFzkBAykti6 > > Why would a GPS module produce jitter with a pattern like this? > > Trent, I decided to R.T.F.M.(read the fantastic manual ;-) > > It looks like that in your Telit module, there is a mode called > > --- > Client Generated Extended Ephemeris (CGEE) That sounds very promising! Your FM is better than my FM, the "JN3 Hardware User Guide" revision 2, which has nothing in it about extended ephemeris mode. > CGEE data is always generated for a prediction interval of three days: > - Consists of 18 blocks of 4-hour EE data blocks > - Updated when a newly visible satellite is acquired I'm indoors with a poor view of the sky, so I'm be surprised if new satellites don't come into view throughout the day. > - Updated when new broadcast ephemeris is received from a tracked > satellite and the current EE data block is nearing expiration That explains the peak every four hours, assuming the EE data blocks are synced to start at UTC (n*4):00 and not device power on. > - On average, it takes 1.2 seconds per satellite for the receiver to > calculate CGEE That would easily explain the few outliers at the 4 hour mark. But std.dev. sure appears to increase for about 2 hours up to the 4 hour mark, then rests back to a lower value for about 2 hours before increasing again. See attached graphs. It's even more apparent when I overlay each hour period on the same X axis. That doesn't seem to fit the description of CGEE mode, but then again we don't really know the algorithms used in the GPS receiver. It's possible that a calculation involving a 4 hour EE data table takes longer, and thus produces more jitter in competing threads like NMEA output, when the computation is using the end of the interval vs the beginning. E.g., a linear search for a line in the table to use. > >From a quick glance at the manual, it looks like this mode can be > turned off with: > > AT$GPSIFIX=0 Unfortunately, the GPS's design as part of the IRU means I can't write to it :(. I'd really like to try that and see what happens. Obviously the proper fix is to get PPS working and I've known that all along. I'm really more interested in the WHY of the four hour cycle. I think turning off CGEE will be the only way to know if that's the sole explanation, or if there is more at play. ___ 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] Fwd: HP5061B Ion Current
https://www.febo.com/pipermail/time-nuts/2017-March/104374.html The design on the voltage and current limiter is complete but not breadboarded yet. We are getting a little more time on our HP5061B beam tube after beefing up the +3,500 Volt power supply. We have the frequency control R4 turned all the way up to 1900 cps with beam tube ion pump load. We have a shunt across the ammeter so it can measure 100 μA full scale instead of 50μA. We dare not disconnect the load because voltage limiting is not operational yet. Continuous lock light is lit. Note that lock is normal at over 3 times what the book said was normal cesium turn on point. If we could go to +3,500 Volts, the current would likely be 100 μA. I calculate that lock would be normal at 1 mA ion pump current. time μA voltage 08:46 56 3,620 09:46 70 3,400 11:25 72 3,360 12:58 76 3,300 We just got in our second HP5061B yesterday It's ion current was only 14 μA but we haven't checked the voltage on the +3,500 V supply yet. It appears to have a problem with the -2,500 V supply. πθ°μΩω±√·Γλ WB0KVV ___ 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] Datum GPS Receiver 9390-5537 found
Hello, Friday, March 24, 2017, 19:09:14, Heinz Breuer wrote: H> Google directed me to website in Russia for a download but a H> window popped up asking me to enter my phone number. This was H> suspicious and I left immediately. Usually it may be translated as "some server in .ru domain located on a abuse-tolerant hosting somewhere in South Korea or Ukraine". ;) I was unable to find that on Google, but there is little chances that they really have something. Usually such websites "expose" a lots of keywords to search machines just to get some hits and "feed" visitors with a pile of spam and links to porn and online gambling sites. Sometimes even worse, like planting worms as "free fast downloaders" or something similar. If there was really something promising - email me a link, I'll look there (cautiously). ;) 73! Yuri. -- Best regards, Yuri mailto:y...@ostry.ru ___ 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] Datum GPS Receiver 9390-5537 found
Hello, I was lucky on eBay and won a Datum 9390-5537 GPS receiver. Condition is unknown and there was no documentation with it. I would appreciate a manual for it either on paper or pdf. I will of course cover all expenses. Google directed me to website in Russia for a download but a window popped up asking me to enter my phone number. This was suspicious and I left immediately. vy 73 Heinz DH2FA, KM5VT Von meinem iPhone gesendet ___ 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] Time Dilation tinkering
Around 2000 when Offshore Navigation went Bell up because of GPS, I purchased more than 50 Cesium Standards most HP 5061A but also some FTS units. Most HP units went in a crate to Germany, kept a few, but kept all FTS units. I did take one FTS on the plane from Miami to Frankfurt operating, fascinated by what HP had done. This was before my time nuts days and had no way to measure any thing, but it fit nicely in a carry on with wheels about 50 lb, 20 lb 12V 18 A batteries, 20 lb FTS 5000. No problem at security, while waiting for boarding had it plugged in the Admirals Club and on arrival plugged it in to the 12 V of the rental car. Having a life long Platinum 5 Million Mile card and First Class may have helped. Having twice in the last 30 years moved my lab to and from Germany I have carried some pretty heavy and large equipment on board with no problem ever.I still have the Samsonite suit cases that fit 19 inch instruments. Bert Kehren In a message dated 3/23/2017 12:00:34 P.M. Eastern Daylight Time, eb4...@gmail.com writes: Not mentioning that the clock traveled in a passenger seat (even with the seat belt fastened). The vision of a big box with cables and a good sized clock ticking (it was a Patek Philippe movement in early HP Cesiums) frightened some passengers and the person accompanying the clock had to give a lot of explanations. The use of the word "atomic" worsened things somewhat. (Memories from Apollo flights good times) Regards, Ignacio, EB4APL El 23/03/2017 a las 12:33, Bob Camp escribió: > Hi > > Back before GPS and similar systems, hauling Cs standards on commercial aircraft was > a bit more common than it is today. One of the critical tricks of the trade was knowing where > each power outlet was on a specific plane and how close it was to this or that seat. The next > trick was knowing how to talk the crew into letting you plug the gizmo in the seat next to yours > into that outlet. Sometimes the magic worked and other times you had to depend on your > battery pack. Needless to say, getting through the over ocean travel process with a dead > standard was not good news. > > Bob > >> On Mar 22, 2017, at 10:59 PM, Bob Bownes wrote: >> >> It's not getting one past the airport authorities that's the issue. It's getting one that's powered up past them. ;) >> >> Written from about 10,000'. :) >> >>> On Mar 22, 2017, at 20:15, Tom Van Baak wrote: >>> >>> Chris Albertson wrote: Why drive up a mountain? >>> "Because it's there" ;-) And because there's a paved road, and it's free, and there's a place to stay overnight, and the mountain doesn't move. Plus a car makes a good portable time lab; you can share the experience with family or students or visiting time nuts; and a number of technical reasons. >>> >>> But most importantly: you can remain at altitude as long as you want -- in order to accumulate just enough nanoseconds of time dilation to meet your experiment's S/N goal -- without running into (or much worse, going beyond) the flicker floor of your clocks. >>> >>> There are several different ways to measure time dilation with atomic clocks. Some notes here: >>> http://leapsecond.com/pages/atomic-tom/ >>> >>> Take the clock with you inside the pressurized cabin of a commercial airliner >>> Yes, and this has been done many times. The first (1971) and most famous of all traveling clock relativity experiments is: >>> https://en.wikipedia.org/wiki/Hafele%E2%80%93Keating_experiment >>> >>> For vintage hp flying clock articles see: >>> https://www.febo.com/pipermail/time-nuts/2013-January/073743.html >>> >>> Two modern examples are described here: >>> >>> "Time flies" >>> http://www.npl.co.uk/news/time-flies >>> >>> "Demonstrating Relativity by Flying Atomic Clocks" >>> http://www.npl.co.uk/upload/pdf/metromnia_issue18.pdf >>> >>> /tvb >>> >>> - Original Message - >>> From: Chris Albertson >>> To: Tom Van Baak ; Discussion of precise time and frequency measurement >>> Sent: Tuesday, March 21, 2017 7:12 PM >>> Subject: Re: [time-nuts] Time Dilation tinkering >>> >>> "flight" there is the word.Why drive up a mountain? Take the clock with you inside the pressurized cabin of a commercial airliner next time you are on one of those 10 hour trans=pacific flights. You be taller then any mountain and it is actually cheaper then a weather balloon. >>> >>> Can you get a Rb clock past the TSA x-ray machine. Maybe if you ask first. There must be a way to hand cary specialized equipment. >>> >>> On Tue, Mar 21, 2017 at 7:03 PM, Tom Van Baak wrote: >>> >>> But attached is one of the first plots where I put a SA.32m in a home-brew vacuum chamber and pulled down to a few inches of Hg for a few hours to simulate the low pressure of a flight up to 50 or 90,000 ft. For a high altitude relativity experiment -- where you'd like your clock to remain stable
Re: [time-nuts] Time Dilation tinkering
Rather than commercial passenger flights, it used to be one could get connections and fly along on transport, ferry or private flights, typically for a (no-frills) low fee. There are also flights made for testing equipment at altitude, including radio, satellite, imaging or other sensing equipment. Rather than hiring such, if it could be demonstrated that your experiment wouldn't interfere with their test/survey/experiment instruments, you may find someone sympathetic to letting you tag along. Local universities may know of sympathetic companies or pilots. Or check with local flying instructors or inspectors, who seem to know everything that's going on. (A friend once had to accompany an imaging package on a Lear Jet. With three hours rented and his tests completed in one, he got to sit at the controls and buzz around the north until they had to return.) The above would not only let you bring your powered experiment package along to altitude, but not create a panic when commercial passengers or cabin crew saw blinking lights or some such. And imagine if you're seen hooking up a cable to a device and collecting data into a laptop... And you could even be in trouble if seen doing anything with numbers that wasn't obviously accounting. On 22/03/2017 10:59 PM, Bob Bownes wrote: It's not getting one past the airport authorities that's the issue. It's getting one that's powered up past them. ;) Written from about 10,000'. :) ___ 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] WTB: GPSDO
At 03:52 PM 3/22/2017, Nick Sayer via time-nuts wrote: Just a little side query For those using one of these sorts of splitters with a Thunderbolt, have you seen anything odd? My thunderbolt *insists* on being on the DC Pass port. If you put it on a DC Mine doesn't. I just swapped ports around so that the tbolt isn't powering the antenna, and it's still tracking, but it is now complaining about an open antenna. My splitter is a 4 way DirecTV with DC pass on one port. F connectors FTW. (Before I had an outdoor timing antenna, I used the TAPR Motorola ANT1A. It must not pull enough current, because my tbolt would go in and out of antenna open alarm.) -- newell N5TNL ___ 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.