[chiralSPO (OP)]

An event (and aftermath) was detected by gravity waves, γ-ray, and IR. It is consistent with two neutron stars colliding!

[jeffreyH]

I would like to know the exact reason for the 20 second delay in detecting the light source.

[chiralSPO (OP)]

My understanding is that the light slows down a little bit as it travels (space is not a perfect vacuum, so the light interacts with the ions, atoms and dust in the cosmos, leading to a decrease in the velocity. I guess the effect is more subtle  for gravity(or nonexistant? is there such thing as permeability/permitivity for gravity?)

Given that it was about 150 Mly away, and the delay was only 20 seconds, that means the space in between has an index of refraction of about 1.0000000000000000000000001 (that's *very* close to 1)

[jeffreyH]

Well to the best of my knowledge you cannot deflect gravity. It also travels unhindered by mass.

[chris]

Is there any reason why this story attracted stupid amounts of hype and uber-"secrecy" around the press announcement?

I knew this was coming out a week ago and yet no one would actually send me a copy of the manuscript, brief me on the announcement etc, meaning that we could not plan ahead or send any team members to the announcement because we had no idea whether it was a story or not.

Anyone care to enlighten me on why they were so OTT about this observation?

[jeffreyH]

Everything is hyped up these days. It gets boring. Maybe they are vying for the Nobel prize. I would rather listen to the NS podcasts. Their press conference was sooooo boring.

[syhprum]

Nature as usual gives the definitive account while The Scientific American gives a very non technical account, the New scientist account is full of errors!

[geordief]

Well to the best of my knowledge you cannot deflect gravity. It also travels unhindered by mass.

You mean gravitational waves? I am not sure if it is correct terminology to speak of gravity
"traveling"

I wonder whether gravitational waves are in fact subject to deflection by massive objects etc


I seem to remember someone recently quoting Einstein to the effect that "gravity causes gravity" which may be relevant.

[jeffreyH]

That just means that the strength of the gravitational field increases. The energy of the gravitational field is inertial in nature.

[evan_au]

Is this the first direct observation of 2 neutron stars colliding?

No, many have been observed via their gamma ray burst (GRB), and some even associated with a visual or X-Ray afterglow.

I would say that this is the first collision of 2 neutron stars where the source of the resulting GRB and afterglow has been positively identified.

See: https://en.wikipedia.org/wiki/Gamma-ray_burst#Afterglow

20 second delay in detecting the light source

It was only 1.7 seconds, so you can add an extra zero to the refractive index of space.

[jeffreyH]

Well there go the media exaggerating again. The report I read said 20 seconds! So I would conclude, on that evidence, that gravitational waves travel at the speed of light.

[Bogie_smiles]

My utmost congratulations and appreciation to all the science professionals, past and present, who have brought these discoveries to we layman science enthusiasts. It marks the end of a "big wait", and builds expectations for more. Wonderful; wow, just WOW.