LIGO Press Conference Stream

[RobM77]

For anyone interested, here's a live stream of today's much anticipated LIGO press conference:

https://www.youtube.com/watch?v=zyo4DFr4D4I

This will hopefully go live at 3:15pm GMT.

[RobM77]

That link didn't do anything. Here's one that works:

http://youtu.be/c7293kAiPZw

[Derek Smith]

Text version here:

https://www.theguardian.com/science/across-the-uni...

Two black holes travelling at half the speed of light collide. Puts Eccentrica Gallumbits in the shade.

[RobM77]

And here's the paper:

https://dcc.ligo.org/public/0122/P150914/014/LIGO-...

Quite an amazing discovery Incredibly exciting

[Gojira]

RobM77 said:

And here's the paper:

https://dcc.ligo.org/public/0122/P150914/014/LIGO-...

Quite an amazing discovery Incredibly exciting

Abso-frickin-lutely...

They have just made every book that metions gravitational waves on the planet out of date

But the acceleration curve in the paper is scary..

About .32c to .6c... in just over .2 of a second

[CrutyRammers]

Very big news this, heard it on the way home. Should be able to get working on the hoverboards soon then?

[4x4Tyke]

Some doubts concerning announced results starting to appear

The NS articles are easy reads but are paywalled.

Doubts raised
https://www.newscientist.com/article/mg24032022-60...
https://www.thewire.in/the-sciences/danish-groups-...
https://arstechnica.com/science/2018/10/danish-phy...

Doubters background
http://www.nbi.ku.dk/gravitational-waves/index.htm...

Response to doubts
https://www.newscientist.com/article/2184360-ligo-...

Edited by 4x4Tyke on Monday 5th November 15:02

[Kccv23highliftcam]

4x4Tyke said:

Doubts starting to appear

https://www.newscientist.com/article/mg24032022-60...
https://www.newscientist.com/article/2184360-ligo-...

https://arstechnica.com/science/2018/10/danish-phy...
https://www.thewire.in/the-sciences/danish-groups-...
http://www.nbi.ku.dk/gravitational-waves/index.htm...

Is there just one source and they are all jumping on the bandwagon though....a bit like, you know, it's all over social media so it MUST be right....

[RobM77]

Kccv23highliftcam said:

4x4Tyke said:

Doubts starting to appear

https://www.newscientist.com/article/mg24032022-60...
https://www.newscientist.com/article/2184360-ligo-...

https://arstechnica.com/science/2018/10/danish-phy...
https://www.thewire.in/the-sciences/danish-groups-...
http://www.nbi.ku.dk/gravitational-waves/index.htm...

Is there just one source and they are all jumping on the bandwagon though....a bit like, you know, it's all over social media so it MUST be right....

Yes, that one group at the NBI. They're not doubting the results per se, if you read their statements, they're merely advising caution on LIGO's data cleansing techniques. LIGO are due to respond soon.

[4x4Tyke]

RobM77 said:

Yes, that one group at the NBI. They're not doubting the results per se, if you read their statements, they're merely advising caution on LIGO's data cleansing techniques. LIGO are due to respond soon.

The second New Scientist article covers the response, I gather there are two sceptical groups, the Danish lot and Spanish group. I'll label the links above better.

The Danish group's questions are largely about the analysis, that the signals do not really justify the rather assertive language used by LIGO, they are not saying they are wrong, per say.

This is however how good science is supposed to work, methods and results challenged, constructive critiques raised and challenged back. The idea being the next round of announced experiment results and papers will be more robust until they cannot be challenged in a meaningful way.

[RobM77]

4x4Tyke said:

RobM77 said:

Yes, that one group at the NBI. They're not doubting the results per se, if you read their statements, they're merely advising caution on LIGO's data cleansing techniques. LIGO are due to respond soon.

The second New Scientist article covers the response, I gather there are two sceptical groups, the Danish lot and Spanish group. I'll label the links above better.

The Danish group's questions are largely about the analysis, that the signals do not really justify the rather assertive language used by LIGO, they are not saying they are wrong, per say.

This is however how good science is supposed to work, methods and results challenged, constructive critiques raised and challenged back. The idea being the next round of announced experiment results and papers will be more robust until they cannot be challenged in a meaningful way.

Indeed, yes. I would advise caution though; there are lots of great minds in institutions around the world who accept LIGO's GW detection. The other key principle in science is of course consensus, and as far as I know there is still a consensus for the detection of GWs. The New Scientist do have a tendency to pick up on poorly supported niche ideas and make a storm in a teacup about them - it's why I stopped reading NS years ago.

[Polite M135 driver]

i just wanted to share my favourite LIGO fact.

The accuracy to which LIGO measures the length-change across their inferometer is equivalent to measuring the distance to the nearest star (7 light years or something, ask an astronomer) to a precision equal to the width of a human hair. It's just amazing.

[4x4Tyke]

Perhaps somebody with stronger physics can answer this conundrum I have, presumably this must have been designed into LIGO but I've never seen it explained.

Given cosmologist combine space and time into spacetime,
And we understand gravitational fields stretch time, as per gravitational time dilation,
And the experiment is designed to detect the stretching of space,

So presumably we should expect gravitational waves stretch time over the wave in the same way it is expected to stretch space.

How come this doesn't mask the detection?

Edited by 4x4Tyke on Tuesday 13th November 10:47

[Pobolycwm]

Just my own thoughts here, Space and time do not correlate exactly linearly, they do so along a hyperbolic curve so it’s not a 50/50 trade off between space stretching and time dilating. There may well be a compensating dilation of time corresponding to space stretching as the gravity wave passes through the detector but possibly not enough to “neutralise” each other with respect to the measurement in earth time.
There are some other spooky effects to get in the way, but they are beyond my ability to contemplate what their effect is on a gravity wave detector.

[4x4Tyke]

ash73 said:

Given the distance is derived from the time for a laser to bounce back and forth along each arm (several hundred times), I think it's measuring spacetime not just space.

Yes that is the point of the question. As the wave stretches space, I expect it should also stretch time as well. As it contracts space it should contract time as well. Since time is the metric for measuring the stretching of space and I would expect it to similarly stretch time increase and decrease. It can't change c but surely it does change the rate of time as as per gravitational time dilation and mask or cancel out the difference.