[time-nuts] Hunting dark matter with GPS data

[André Esteves]

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

[Trent Piepho]

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.
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[time-nuts] Fwd: HP5061B Ion Current

[Donald E. Pauly]

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
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Re: [time-nuts] Datum GPS Receiver 9390-5537 found

[Yuri Ostry]

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


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[time-nuts] Datum GPS Receiver 9390-5537 found

[Heinz Breuer]

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
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Re: [time-nuts] Time Dilation tinkering

[Bert Kehren via time-nuts]

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 

Re: [time-nuts] Time Dilation tinkering

[MLewis]

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'. :)


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Re: [time-nuts] WTB: GPSDO

[Scott Newell]

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 


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