Gravitational Waves

[Telecaster]

For those of you interested in the subject, here's a link to a paper on detecting very low frequency (long wavelength) gravitational waves using "arrays" of pulsars. (Pulsars are extremely dense supernova remnants composed of neutrons smashed up against each other. These objects spin rapidly, emitting twin beans of photons & electrons in the process. When the beams sweep across our field of view we call the objects pulsars due to the pulses of radio light we can detect coming from them. Otherwise we use the term neutron stars.) IMO it's very cool that we should be able to use the precise timing of the pulsar sweeps to, in effect, construct a GW detector in space.

http://arxiv.org/abs/1511.05564

-Dave-

[jeremyrh]

Gravitation has always interested me. As with suction, I realise that it simply doesn't exist: suction is nothing but the other side of pressure, and gravity but the second part of cause and effect: if you jump six feet up in the air, as a measure of vertical distance travelled, you can only complete the action by virtue of its opposite - the return journey downwards, also of six feet. Nothing to do with 'gravity' at all, simply a product of equal and opposite directions. Do you see?

I recommend not getting left behind on Mars.

However, I am reminded of when I went to an interview for a university place. My interviewer, an eminent scientist, drew a circle to represent the Earth and another to represent a satellite, and asked me to add arrows to show the forces acting on the satellite. I drew an arrow to represent its gravitational attraction to the Earth and returned his pencil to him. He asked me what I had forgotten. I replied nothing. He asked me about centrifugal force. I replied that there is no such thing. I did not get a place at the university, but of course by that time I no longer wanted one. The relevance here is that it's not just lay people who get the basics of physics wrong.

[Rob C]

I recommend not getting left behind on Mars.

However, I am reminded of when I went to an interview for a university place. My interviewer, an eminent scientist, drew a circle to represent the Earth and another to represent a satellite, and asked me to add arrows to show the forces acting on the satellite. I drew an arrow to represent its gravitational attraction to the Earth and returned his pencil to him. He asked me what I had forgotten. I replied nothing. He asked me about centrifugal force. I replied that there is no such thing. I did not get a place at the university, but of course by that time I no longer wanted one. The relevance here is that it's not just lay people who get the basics of physics wrong.

And to think that I knew that one too, centripetal being the real deal.

The thing is, though, as with realpolitik, so realphysik reveals itself when you stand beside a car stuck in the mud. I was going to say when the spaghetti hit the fan...

Oh for my lost if misspent youth! Not that, in my defence, I spent much time playing with fans or spaghetti.

Rob C

[Telecaster]

The LIGO folks have another press conference scheduled for tomorrow at 1:15pm US Eastern Daylight Time. 

-Dave-

[Telecaster]

Again, as anticipated, the two LIGOs have seen another black hole merger event. This time on Christmas Day (in the US…December 26 in some other parts of the world). The event was closer, ~1.4 billion light years away, and involved smaller black holes than the one detected last September.

There's been a third merger detection since too, but this one is being called a "candidate." It was likely genuine but the LIGO folks are being cautious as it happened near the limit of the detectors' capability.

The two LIGOs are currently being upgraded, with increased sensitivity, and will go back online this coming September.

http://www.astronomy.com/news/2016/06/ligo-detects-a-second-set-of-gravitational-waves

http://journals.aps.org/prl/highlights

-Dave-

[BJL]

For the curious, there is an official LIGO news site: https://www.ligo.caltech.edu/news/

[Zorki5]

Again, as anticipated, the two LIGOs have seen another black hole merger event.

Another article on this, with a linked video: Second Observation of Gravitational Waves Revealed

This time on Christmas Day (in the US…December 26 in some other parts of the world).

And some other parts have it on January 7th