A laymen's guide Gravity, Gravity Waves, LIGO, and how it all works

Mo
Mo
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> The key here is peroidic.

Message 5248 in response to message 5245

> The key here is peroidic. Lots of things probably generate
> gravitational waves. There only a very few that could generate peroidic
> gravitational waves. The most likely that we will be able to do a followup
> detection of is a pulsar in a binary relationship with another massive body,
> like another neutron star.

Ah, okay. That explains it. Thanks, StarCharter!


Look here, brother, who you jiving with that cosmic debris?--Frank Zappa.

Mo
Mo
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Thanks for the link, cIclops.

Message 5249 in response to message 5247

Thanks for the link, cIclops. That lecture is great. I'm passing it on to all the mates I'm trying to convince to join Einstein@home. ;)


Look here, brother, who you jiving with that cosmic debris?--Frank Zappa.

Czar Brent
Czar Brent
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Awesome find cIclops!!!!!

Awesome find cIclops!!!!! WOW

WARNING! DiHydrogen MonOxide kills!

StarCharter
StarCharter
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Mo, You're a writer? What do

Mo,
You're a writer? What do you write?

There are two secrets to life: 1) Don't tell everything you know...

Jennifer
Jennifer
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Can anybody help me out with

Can anybody help me out with these questions?
First, we know that gravitational waves are theoretically supposed to distort or "warp" space and time. For most people, including me, I think that the distortion of space is much easier to understand than the distortion of time. The only way that makes sense to me to describe the distortion of time, is to say that when space is expanded, time slows down to an outside observer. On the other hand, when space contracts, time speeds up. My question is, if time is speeding up and slowing down, then how can we say that gravitational waves travel at the speed of light? How do we measure speed when the two very parameters that define speed are changing?? Along the same lines, how can we measure the period of the gravitational waves?
Second, I liked the explanation given by Ben Owen -- "This is a systematic search of the sky, one location at a time, for any periodic gravitational wave coming from that location. It has to be done for each location because the frequency shifts (Doppler shifts) due to the Earth's motion are different for different sky locations." I want to make sure I am understanding this correctly -- it's not the instrument itself that is searching one location in the sky at a time, correct? (At first, one might think this way since by analogy a telescope searches one point in the sky at a time) LIGO is collecting data all the time and THEN (after the collection is made) the data is being processed for each point in the sky by using Fourier transforms and taking into consideration the Doppler shifts. Am I right or wrong about this? Also, I have been told that there is a phased array antenna in the instrument and that this is how it searches one point in the sky at a time. Can someone explain to me how this works?

Mo
Mo
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Hi SC, > You're a writer?

Message 5253 in response to message 5251

Hi SC,

> You're a writer? What do you write?

Mainly I've written TV screenplays, stage (opera librettos) and short fiction, but currently I'm onto the third draft of a novel (...when I'm not procrastinating online, of course.;)

Cheers,

Mo.


Look here, brother, who you jiving with that cosmic debris?--Frank Zappa.

StarCharter
StarCharter
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> > You're a writer? What do

Message 5254 in response to message 5253

> > You're a writer? What do you write?
>
> Mainly I've written TV screenplays, stage (opera librettos) and short fiction,
> but currently I'm onto the third draft of a novel (...when I'm not
> procrastinating online, of course.;)

I ask because I also write fiction. Do you belong to My Writer Buddy? My screen name there is Acordant. I'd love to read some of your fiction.

There are two secrets to life: 1) Don't tell everything you know...

Mo
Mo
Joined: 5 Mar 05
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> I ask because I also write

Message 5255 in response to message 5254

> I ask because I also write fiction. Do you belong to href="https://einsteinathome.org/%3Ca%20href%3D"http://www.writerbuddy.com/">http://www.writerbuddy.com/">My Writer Buddy[/url]? My screen name there
> is Acordant. I'd love to read some of your fiction.

I'll check it out. Thanks. :)


Look here, brother, who you jiving with that cosmic debris?--Frank Zappa.

barkster
barkster
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Awesome video clip!... even

Awesome video clip!... even if it was from January 2003.

PLEASE tell me there is an updated lecture somewhere I can watch. I'm very curious (if not excited) to know how much progress has been made since then. The accuracy, the results, the technology, the mechanics... it's all good. But looking at the latest "approved talks" slides on the LIGO site without a voice behind them just isn't working for me.

"No, I'm not a scientist... but I did stay at a Holiday Inn Express."

MarkF
MarkF
Joined: 12 Apr 05
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Can anybody help me out with

Message 5257 in response to message 5252

Can anybody help me out with these questions?
First, we know that gravitational waves are theoretically supposed to distort or "warp" space and time. For most people, including me, I think that the distortion of space is much easier to understand than the distortion of time. The only way that makes sense to me to describe the distortion of time, is to say that when space is expanded, time slows down to an outside observer. On the other hand, when space contracts, time speeds up. My question is, if time is speeding up and slowing down, then how can we say that gravitational waves travel at the speed of light? How do we measure speed when the two very parameters that define speed are changing?? Along the same lines, how can we measure the period of the gravitational waves?

Relativity divides all paths into three different types space like, null and time like. The null paths are such that the displaement in space exactly matches the the displacement in time. These paths represent objects traveling at the speed of light. To a distant observer objests on such paths may appear to be moving faster or slower then due to the effects you mention but they are not sinficant in the analsys being done by this project.

Second, I liked the explanation given by Ben Owen -- "This is a systematic search of the sky, one location at a time, for any periodic gravitational wave coming from that location. It has to be done for each location because the frequency shifts (Doppler shifts) due to the Earth's motion are different for different sky locations." I want to make sure I am understanding this correctly -- it's not the instrument itself that is searching one location in the sky at a time, correct? (At first, one might think this way since by analogy a telescope searches one point in the sky at a time) LIGO is collecting data all the time and THEN (after the collection is made) the data is being processed for each point in the sky by using Fourier transforms and taking into consideration the Doppler shifts. Am I right or wrong about this? Also, I have been told that there is a phased array antenna in the instrument and that this is how it searches one point in the sky at a time. Can someone explain to me how this works?

Sounds like you have it right. A signal from a specfic direction in space will have a fixed difference in the arrival time a each of the three observatories. In the type of analsys being done here such time differences are commonly phase shifts. By adjusting for these differences (phase shifting) it is possible to 'focus' on the specfic direction in question.

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