What can I do at home, to observe such processes? Or is it way beyond
any imagination to participate in any such experiments?

Volker

Am 25.01.2017 um 06:15 schrieb Hal Murray:

….. errr … would not that be the right end of the ADEV curve? …..:)

Back in the 1980’s these guys were after sub 1x10^-15 bumps over path
distances like Earth to Jupiter. Not sure what they are after these days.

Bob

First, a picky - but important - point. There is a difference between
"gravity waves" and "gravitational waves". When you go to the beach and
watch the waves crash on the shore, that's an example of a gravity wave.

Now, onto the far more interesting topic of gravitational waves and my pet
topic, pulsars.

Pulsars most likely give off gravitational waves. The rotate at a rate
anywhere from 1/12 Hz to 716 Hz. The brightest (in a radio sense) and one
of the closest pulsars is the Vela pulsar which rotates at 11.18677266 Hz
(as of a few days back). This frequency is in the sensitivity bands of
Advanced LIGO and Advanced VIRGO, but the gravitational waves from Vela are
probably too "faint" to be detected. But there is still no harm in trying.

Jim Palfreyman

On 25 January 2017 at 16:15, Hal Murray hmurray@megapathdsl.net wrote:

LIGO is a billion dollar experiment, involving thousands of PhD's so it will be some time until you can do that sort of stuff alone at home, or with your family.

Jim Palfreyman has mentioned before what it would take to do Pulsar measurements as a home experiment. Search for the old threads or he can jump in to remind us why it can't or hasn't been done yet. See also the thread a month ago about a DIY H-masers since you'll want some of them on hand before you start.

It's worth spending time reading anything about LIGO. The experiment is out-of-this-world clever, complex, sensitive. And it actually works! Unlike the particle physics tree, which seems to be nearing the end of bearing fruit, LIGO is at the very beginning of an entirely new way to study the universe.

/tvb

On 1/25/17 6:58 PM, Tom Van Baak wrote:

I wonder if there are ways to do this kind of science in a massively
parallel way.. rather than the "one big awesomely high performing
instrument" you have a million mediocre instruments...

Of course, I know that doesn't always work, otherwise we could just buy
1000 cheap crystals and tell the maser folks to peddle their wares
elsewhere <grin>

But, as in many other endeavors, there's a limit to "how big/fast/good"
a single device can be, and you have to go to multiple devices - there's
always complexity and a learning curve, but eventually there is success:

One big power grid tube is better than many smaller ones, but
eventually, you hit the maximum size tube, and if you need more power
there's nowhere else to go but multiples.

Scientific computation hit the "single processor" wall, ultimately
resulting in the development of modern Beowulf cluster computers, which
in turn forced the development of new algorithms and reformulating the
underlying problem to allow such large clusters to be useful (Amdahl's
law, and all), and now things like exascale computing are becoming reality.

I've thought about whether one could do amateur radio Venus bounce or
Mars bounce, with a distributed transmitter/receiver system, timed by
GPS, so that you can do coherent processing.

I can't recall what I said before, but it has been done in the backyard
before. There's good news and bad news. The good news is that all the
software for processing your data: coherent dedispersion, folding, moving
all arrival times to the solar system barycentre, Einstein delay, Shapiro
delay, fitting, analysis etc is open source. You need DSPSR, PSRCHIVE, and
TEMPO2 and a unix machine to run them on.

The bad news:

Vela had a declination of -45 10 35 which means it's not visible very often
for you northerners. The second brightest pulsar has a similar declination.
After that, forget it - they are too faint.

Observing of individual pulses requires around a 20+ m radio telescope with
a receiver cooled to 20K (at ~1400 MHz). However using the above software
you can fold your data on the latest pulse period (which I can provide if
needed) and this then brings things down to a possible level:

You'll need a dish that can track. One that is 2 m across might just work.
Frequency choice is important. The lower the frequency the stronger the
pulse, but also multipath scattering smears the pulse out. Around 1400 MHz
is a good choice for removing the scattering, but may be too faint for
small dishes. If you went with ~600 MHz that could work - but do check any
local RFI.

If you didn't track, but just waited for the pulsar to pass through the
beam, you'd get about 2 minutes of data. That might be enough to fold and
get a signal.

It'd be a long, but awesome, project to work on.

The really cool part is that Vela glitches (speeds up) in rotation ~3 years
by around deltaf/f =10^-6 and you could measure that. It just glitched in
December (and I was observing at the time!), so you have another 3 years to
get building.

As to timing, any half decent GPSDO would be fine.

Oh, almost forgot, you'd also need a sampler.

Jim Palfreyman

On 26 January 2017 at 13:58, Tom Van Baak tvb@leapsecond.com wrote:

On Wed, Jan 25, 2017 at 1:35 AM, Volker Esper ailer2@t-online.de wrote:

It's not exactly direct observation, but you can participate by
joining the Einstein@Home project to use your computer's spare CPU
cycles to search for events in LIGO data (as well as radio and gamma
ray telescopes):

https://einsteinathome.org/

Henry