Gravitational waves claimed to be detected by aLigo

[Col_Klonk]

How are you getting that? There is every indication that gravity waves travel at (about) the speed of light, but not faster.

Same as radio waves, which already travel at the speed of light.

Depends of the 'medium' of travel... Light speed is not written in stone..

 

[Urwumpe]

Depends of the 'medium' of travel... Light speed is not written in stone..

The speed of light is not, this can be as slow as a pedestrian. The vacuum speed of light is a universal constant, though.

 

[Thunder Chicken]

The speed of light is not, this can be as slow as a pedestrian. The vacuum speed of light is a universal constant, though.

It can be even slower, as slow as a pedestrian sitting on a bench waiting for a bus:

http://www.physicscentral.com/explore/action/light.cfm

And when things exceed the speed of light in a given medium, you get pretty Cherenkov radiation (though if the particles are ionizing and the medium is non-absorbing like air, you are seeing fluorescence and it may be the last thing you ever see).

 

[jedidia]

Depends of the 'medium' of travel... Light speed is not written in stone..

Of course, but when someone talks about the speed of light without any addendum, I generally assume that they are talking about the constant 'c'

 

[Andy44]

It can be even slower, as slow as a pedestrian sitting on a bench waiting for a bus:

http://www.physicscentral.com/explore/action/light.cfm

And when things exceed the speed of light in a given medium, you get pretty Cherenkov radiation (though if the particles are ionizing and the medium is non-absorbing like air, you are seeing fluorescence and it may be the last thing you ever see).

From the Atomic Rockets page:

The characteristic blue glow you've seen in photographs of "swimming pool" reactors is called Cherenkov Radiation. If you the blue Cherenkov glow around an object IN THE AIR (not at the bottom of a swimming pool reactor), you'd better be viewing it through several inches of lead glass or you have already taken a lethal dose, it is far too late to do anything about it, you are already dead. This comes under the heading of "not treating radiation with the respect it deserves."

 

[Urwumpe]

If I remember correctly, if you could photograph such a short event, you could see the ionizing radiation of a nuclear bomb form a thick cloud around the bomb before the case vaporizes and the fireball breaks out.

One of the events which will likely be the last things you could see.

 

[Thunder Chicken]

From the Atomic Rockets page:

Not quite correct. Chernekov radiation is the emission of photons from particles exceeding the speed of light in a given medium. What you see in water (c ~ 0.75 c_vacuum) is low level emission and is mostly absorbed by the water. You can safely stand and watch, or operate over cooling ponds, etc.. It often requires an extended exposure to see it well.

The "blue glow" seen with ionizing radiation events in air (c ~ c_vacuum) is mostly fluorescence of nitrogen, different from Chernekov radiation, emitting photons after shell electrons excited by radiation fall back to their original shell. It is exactly the same principle as a neon sign, except the electrons are excited by radiation vs. an electric field. Alexander Yuvchenko famously opened the door to the reactor hall at Chernobyl and noted the very beautiful blue beam of light shining up into the heavens out of the destroyed reactor core. Had he stopped to watch for a few more moments he would not have survived the night - as it was he absorbed a tremendous dose and was near death for quite some time, but he recovered after a fashion.

This is a old picture of air fluorescence from a cyclotron beam. Not sure even this is a good idea, certainly don't want any part of you in the beam.

Ionizing radiation also converts O2 to ozone (O3). Many of the liquidators of Chernobyl knew when they were in a high radiation environment because the could smell the ozone.

 

[Andy44]

I read somewhere that people involved in criticality accidents often report (before dying, of course) seeing a blue flash at the time of the event. This was thought to be Cherenkov radiation in air, or possibly the fluorescence you describe, but security camera tapes never seemed to show any change in ambient lighting, so it is now thought that the blue flash is actually Cherenkov radiation induced in the fluid inside the victim's eyeballs. Ouch.

 

[K_Jameson]

I was thinking...
...if the modifications of the gravitational fields propagate at c, hypotetical travel technologies as the Alcubierre Drive (a.k.a. "Warp Drive") simply don't work because if we collapse the space between us and... let's say... Alpha Centauri, we need no less than 4.5 years to do so... so, no advantage.

(i'm talking about the theory, not the technical feasibility).

 

[Notebook]

http://sci.esa.int/integral/57655-integral-sets-limits-on-gamma-rays-from-merging-black-holes/

Following the discovery of gravitational waves from the merging of two black holes, ESA's INTEGRAL satellite has revealed no simultaneous gamma rays, just as models predict.

Absence of evidence?

 

[jedidia]

I was thinking...
...if the modifications of the gravitational fields propagate at c, hypotetical travel technologies as the Alcubierre Drive (a.k.a. "Warp Drive") simply don't work because if we collapse the space between us and... let's say... Alpha Centauri, we need no less than 4.5 years to do so... so, no advantage.

The alcubierre drive would not work by just contracting space, but by contracting a little space in front, and expanding it again at the back of the vessel.
It gets rather mind-twisty in that situation, because the speed of light is the same in any reference frame... The question would essentially be, does the warp-bubble in itself constitute a frame of reference? in that case, the delay would be irrelevant, because it is always relative to the velocity the vessel already has. I think we would be breaking the simultaniousness of events at his point, but then again, we're always doing that when FTL comes into play.

In any case, a working alcubierre drive would at the minimum constitute a reactionless drive even if it couldn't go fster than light, so it would still be a tremendous advantage... and a tremendous problem for physics as we know it... :shifty:

 

[RisingFury]

http://sci.esa.int/integral/57655-integral-sets-limits-on-gamma-rays-from-merging-black-holes/



Absence of evidence?

If you saw a gamma ray burst, it could mean that it wasn't two black holes, but other objects - white dwarfs or neutron stars.

And if there's any other mechanism that can ripple space, it'd usually involve high energies...

 

[Notebook]

http://www.bbc.co.uk/news/science-environment-36540254

Scientists have collected a second burst of gravitational waves sweeping through the Earth.

The warping of space-time was sensed on Christmas Day in the US at the Advanced LIGO laboratories - the same facilities that made the historic first detection in September last year.

Back then, the waves came from two huge coalescing black holes.

This new set of waves, likewise, is ascribed to a black hole merger - but a smaller one.

 

[Notebook]

http://www.bbc.co.uk/news/science-environment-40120680

Scientists are reporting yet another burst of gravitational waves.
The signals were picked up by the Advanced LIGO facilities in the US and are determined to have come from the merger of two huge black holes some three billion light-years from Earth.

 

[Notebook]

Gravitational wave hunters bag fourth black-hole detection
By Pallab Ghosh
Science correspondent, BBC News
27 September 2017

http://www.bbc.co.uk/news/world-australia-41420188

 

[Urwumpe]

http://www.bbc.co.uk/news/world-australia-41420188

There are also rumors that the teams have located the fusion of two neutron stars together with HST. But the consensus here is: "PR shortly before the Nobel Prize awards."

 

[Thorsten]

Are "Review Letters" supposed to be fast-tracked early results perhaps?

1) Why does anyone need fast-tracked results? There's a preprint and a press conference, so surely there's no actual need to get information out even faster?!

2) As pointed out above, the devil is in the detail of the background noise reduction - so to properly review this, someone would need to go through the whole procedure independently. It's not a procedure that can be understood properly within 20 days.

So yeah, peer review is broken here. The whole concept of 'Review Letters' produces a string of sexy 'results' which ultimately have a high probability of being false (in my field, 90% of Review Letters turned out to be false later).

I'd prefer a result that gets reviewed properly even if it takes six months over 10 which get blown out quickly for the heck of it. Yet funding agencies love the quick high attention result, regardless of whether it's right or not. So there's that.

It's more story-telling than science these days unfortunately.

 

[mahdavi3d]

LIGO - Virgo Collaboration

Georgia Institute of Technology : Gravitational Waves From Binary Black Hole Merger Observed for 4th Time

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This graphic shows the data from each of the three observatories. The top graph shows the Signal to Noise Ratio - or roughly how significant the detection was. The middle graph shows the "chirp" or frequency shift across time. The bottom graph shows the wave form. Provided by Sudarshan Ghonge

APOD : LIGO-Virgo GW170814 Skymap

original size

Illustration Credit: LIGO- Virgo Collaboration - Optical Sky Data: A. Mellinger

 

[Notebook]

http://www.bbc.co.uk/news/science-environment-41476648

The 2017 Nobel prize in physics has been awarded to three US scientists for the detection of gravitational waves.
Rainer Weiss, Kip Thorne and Barry Barish will share the nine million kronor (£831,000) prize.
The ripples were predicted by Albert Einstein and are a fundamental consequence of his General Theory of Relativity.
The winners are members of the Ligo-Virgo observatories, which were responsible for the breakthrough.

Not the only predictions around here?

 

[Notebook]

16 October 2017
ESA’s Integral satellite recently played a crucial role in discovering the flash of gamma rays linked to the gravitational waves released by the collision of two neutron stars.
On 17 August, a burst of gamma rays lit up in space for almost two seconds. It was promptly recorded by Integral and NASA’s Fermi satellite.
Such short gamma-ray bursts are not uncommon: Integral catches about 20 every year. But this one was special: just seconds before the two satellites saw the blast, an entirely different instrument was triggered on Earth.
One of the two detectors of the Laser Interferometer Gravitational-wave Observatory (LIGO) experiment, in the USA, recorded the passage of gravitational waves – fluctuations in the fabric of spacetime caused by powerful cosmic events.

http://www.esa.int/Our_Activities/S...ees_blast_travelling_with_gravitational_waves