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tkdguy

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No, gravitational waves propagate at the speed of light. That is actually a part of the direction-finding for the events in the sky: the observatory on the side of Earth closer to the wavemaking event detects it earlier than the others, by interval = (difference in distance along direction to event)/(speed of light).

 

EDIT: In this case, the VIRGO instrument in Italy detected it first, followed 22 milliseconds later by LIGO in Louisiana, followed 3 milliseconds later by LIGO at Hanford.

 

For the neutron star merger announced yesterday, the interval between GW arrival and onset of the light flash is due to the time needed for the hot ejecta to expand to a big enough volume to be detectable by telescopes 40 megaparsecs away.

 

EDIT: Figure 2 here shows the sequence of detections in various means, though it takes some work to grasp everything in that figure.

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How spacecrafts release wastewater could explain Enceladus' jets

 

Wastewater flushed from manned spacecraft could help researchers better understand the icy plumes of water that erupt from the south pole of Saturn's moon Enceladus, according to findings presented at a meeting of the American Astronomical Society's Division for Planetary Sciences. "These observations don't tell us directly what's happening on Enceladus, but they provide a sort of anchor for our interpretations of what we're seeing on Enceladus," presenter Ralph Lorenz said.

[tongue in cheek]

So Enceladus is a spacecraft and we're watching it dump sewage. Hmmmm.

[/tongue in cheek]

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Wait, something here is not right:

Gravity waves are supposedly travelling instantly, not adhering to the light speed limit.

The event was 100 million lightyears away

So the time between us noticing the event via Gravity Observation and seeing anything with all our optical telescopes, should be literally 100 million years (+/- expansion of the universe).

I Think the issue you're having is that Gravity is thought to be instant, ie if I create/move mass here the whole universe notes that, but gravity waves are waves, so they behave the way waves do....though the instant notation may be outdated. I am way out of touch with current physics.

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No, gravitational waves propagate at the speed of light. That is actually a part of the direction-finding for the events in the sky: the observatory on the side of Earth closer to the wavemaking event detects it earlier than the others, by interval = (difference in distance along direction to event)/(speed of light).

 

EDIT: In this case, the VIRGO instrument in Italy detected it first, followed 22 milliseconds later by LIGO in Louisiana, followed 3 milliseconds later by LIGO at Hanford.

 

For the neutron star merger announced yesterday, the interval between GW arrival and onset of the light flash is due to the time needed for the hot ejecta to expand to a big enough volume to be detectable by telescopes 40 megaparsecs away.

 

EDIT: Figure 2 here shows the sequence of detections in various means, though it takes some work to grasp everything in that figure.

 

 

I Think the issue you're having is that Gravity is thought to be instant, ie if I create/move mass here the whole universe notes that, but gravity waves are waves, so they behave the way waves do....though the instant notation may be outdated. I am way out of touch with current physics.

I just read Wikipedia a bit.

Apparently it was asumed to have infinite speed back in Newtonian Physics.

But general relativity predcits speed of light. And chineses scientists found proof for this, using the moon and tides.

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Well, given that the core idea that gives rise to gravity waves is relativity, and a fundamental premise of relativity is that all frames of reference observe the same value for the speed of light, gravity waves have to propagate at the speed of light.

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Actually, this has me thinking: The cosmic speed limit is the speed of light in a vacuum. The actual speed of light drops slightly if it's not in a vacuum.

 

Intergalactic space is really, really close to a perfect vacuum... but not quite. Now I wonder if the gamma pulse (I would guess that's the light from the actual moment of collision) arrived very slightly later than the gravity waves, because space isn't entirely empty.

 

I also wonder to what extent gravity waves behave like other waves. Is a gravity wave bent by the curved space of a gravitational field? Can they be diffracted? (By what?)

 

It's like having a new toy. Makes me wish I were a physicist.

 

Dean Shomshak

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I also wonder to what extent gravity waves behave like other waves. Is a gravity wave bent by the curved space of a gravitational field? Can they be diffracted? (By what?)

Can they be REfracted? If so, do you get Gravity's Rainbow?

 

Lucius Alexander

 

The palindromedary says astronomers have already detected the pot of gold...

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Actually, this has me thinking: The cosmic speed limit is the speed of light in a vacuum. The actual speed of light drops slightly if it's not in a vacuum.

 

Intergalactic space is really, really close to a perfect vacuum... but not quite. Now I wonder if the gamma pulse (I would guess that's the light from the actual moment of collision) arrived very slightly later than the gravity waves, because space isn't entirely empty.

 

I also wonder to what extent gravity waves behave like other waves. Is a gravity wave bent by the curved space of a gravitational field? Can they be diffracted? (By what?)

 

It's like having a new toy. Makes me wish I were a physicist.

 

Dean Shomshak

The hard part is measuring that kind of stuff. Being unable to produce gravity waves ourself makes it really hard to figure out how they behave in a controleld enviroment.

 

What confirmed relativity back in the day, was how starlight managed to "get around" a Eclipsed Sun.

And that only works if gravity waves can not simply pass "through" all mater.

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  • 2 weeks later...

The Nov. 4, 2017 issue of the Economist has two articles on interstellar travelers. The first is about asteroid A/2017 U1, whose trajectory showed that it came from outside the Solar System and is returning to interstellar space. The article incidentally notes that it has not been named yet, and suggests that "Rama" is available and would be appropriate -- after Arthur C. Clarke's novel, Rendezvous with Rama.

 

The second is about proposals to include living organisms on the first interstellar probes. Some organisms, such as the nematode C. elegans, or the tardigrade, can provably survive 20+ years freeze-dried. So, put a few in the CD-sized, laser-propelled probes to Alpha Centauri and see if they can be revived at the end of the journey.

 

 

Dean Shomshak

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15 hours ago, DShomshak said:

The Nov. 4, 2017 issue of the Economist has two articles on interstellar travelers. The first is about asteroid A/2017 U1, whose trajectory showed that it came from outside the Solar System and is returning to interstellar space. The article incidentally notes that it has not been named yet, and suggests that "Rama" is available and would be appropriate -- after Arthur C. Clarke's novel, Rendezvous with Rama.

When hearing Rama, I have to think about the Margarine. Sorry, just can not help myself:

https://en.wikipedia.org/wiki/Rama_(food)

 

15 hours ago, DShomshak said:

The second is about proposals to include living organisms on the first interstellar probes. Some organisms, such as the nematode C. elegans, or the tardigrade, can provably survive 20+ years freeze-dried. So, put a few in the CD-sized, laser-propelled probes to Alpha Centauri and see if they can be revived at the end of the journey

So you want to expose a Tardigrade to Cosmic Radiation? There is that old joke/story that Apes send to space come back super-intelligent and Dogs might become Telepathic.

 

In this case, we might be hoping to get the Spore Hub Drive from Discovery out of it :)

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10 hours ago, Lord Liaden said:

If a preserved organism in a probe we send crashes into another life-bearing planet, we might be responsible for a devastating plague or infestation. Granted, the chances are extremely remote, but still. (It would make for a cool sci-fi story, though.)

In the Tiberium Wars reality of Command and Conquer for a long time it was not clear how the Tiberium first got onto the planet.

 

I do not think the goal is to get them down onto the planet. Just see if even those beings can survive the journey. If something like a Tardigrade can not survive interstellar spaceflight that way, we might have 0 chance ourself.

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20 hours ago, Lord Liaden said:

If a preserved organism in a probe we send crashes into another life-bearing planet, we might be responsible for a devastating plague or infestation. Granted, the chances are extremely remote, but still. (It would make for a cool sci-fi story, though.)

As the article notes, the probe would be moving so fast that the crash would create an explosion of nuclear intensity. Nothing could survive that!

 

(Except maybe a cosmically-irradiated tardigrade-turned kaiju.)

 

Dean Shomshak

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