What is noise?

Steve
Steve
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Topic 192301

Once upon a time there was a race of beings that could see in gravity waves and hear in ultra violet. When the looked into the heavens they saw only the binary white dwarfs nearby, couldn’t detect there own sun, and saw other gravity wave sources within a few hundred thousand light years of there home. The sky was fairly bleak by our standards, but still fairly populated with gravity wave sources.

One day, a scientist in the community suggested that there was another (dark energy/matter) out there affecting the rotation of the skies as they viewed them, and said: “I bet there is another source out there we cant see, it probably happens in the 400 to 700 nm wave length, lets develop a device to detect it. So they all pitch in (after great debate about the cost) and develop an ordinary earth pair of binoculars with false color images in gravity wave format, the point them at the sky and the result is “WHOA there are millions of hits on this wave length – it must be noise� So they canceled out all the NOISE and waited around for a supernova with only a pair of binoculars.

I know it’s a goofy analogy, but it makes me wonder what Noise is.

FalconFly
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What is noise?

Very nice analogy :)

I'm not 100% certain, but from what I know :

In Radio Astronomy, noise is identified/defined as such, because it appears to be 'everywhere'. It doesn't have any distinct direction and (apart from the big bang theory) no identified source.

I must agree though, that having a 'deep ear' into the Noise to see if there are any patterns (right within the noise levels) would be an interesting idea.

The amount of computational resources needed would be quite insane though, as one would not search for 'events' that stand out, but rather content-analyze the 'whole thing', full-time.

(pure speculation=on)
It might also be that the "noise" (or a good portion of it) is a local Product from our Sun.
Ever since the Voyager Spacecraft encountered the "Termination Shock", the reports about its instruments recordings indicate a high possibility that the entire Solar System is buried in a bubble full of its own Radiation/Particles emitted from the Sun. Who knows, maybe that's a good source for omnidirectional noise (travelling back from the boundaries of the termination shock bubble)

http://en.wikipedia.org/wiki/Termination_shock

Another explanation would be, that the Noise is the product of Particles and Radiation emitted from Stars over the course of uncountable Billion years, while being constantly interacted with by (Electro)Magnetic and Gravitational fields, as well as Particle/Particle, Particle/Energy and Energy/Energy collisions. I imagine the Result of that being "quite" random appearing to us listening to it for just a few decades on a limited amount of frequencies and locations.

Here's a good illustration about what Science thinks about it :
http://en.wikipedia.org/wiki/Noise_%28Big-bang%29

Mike Hewson
Mike Hewson
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RE: Once upon a time there

Quote:

Once upon a time there was a race of beings that could see in gravity waves and hear in ultra violet. When the looked into the heavens they saw only the binary white dwarfs nearby, couldn’t detect there own sun, and saw other gravity wave sources within a few hundred thousand light years of there home. The sky was fairly bleak by our standards, but still fairly populated with gravity wave sources.

One day, a scientist in the community suggested that there was another (dark energy/matter) out there affecting the rotation of the skies as they viewed them, and said: “I bet there is another source out there we cant see, it probably happens in the 400 to 700 nm wave length, lets develop a device to detect it. So they all pitch in (after great debate about the cost) and develop an ordinary earth pair of binoculars with false color images in gravity wave format, the point them at the sky and the result is “WHOA there are millions of hits on this wave length – it must be noise� So they canceled out all the NOISE and waited around for a supernova with only a pair of binoculars.

I know it’s a goofy analogy, but it makes me wonder what Noise is.


LOL! It's always curious to phrase it in such terms. What if I had radio antennae for ears etc...

Several aspects I can think of:

- noise is the stuff I'm not interested in. There's a list of disturbances that will register on my apparatus, so I'll try to select the energy mode that I am curious about. Call the rest noise. This may include coupling effects, rampant at LIGO, between modes that we denote as separate. Nature knows better....

- noise is that aspect of my intended energy mode which is random or without preference in the direction of whatever it is I want to demonstrate. In the LIGO's we are certainly interested in photon numbers at the dark port - and those responding to a differential spacetime disturbance along the arms particularly. However there is a limit to accuracy, as per quantum mechanics, in photon arrivals despite any management of other causes. That is called 'shot noise' but you might want to label it 'shot variation'. It's reducible ( as a ratio/fraction ) by upping the laser power, but then you'll start the mirrors swinging due to the higher momentum transfer from the beam to the mirror masses. Roughly speaking the resonant cavity part of the interferometer wants to expand if you shove more power into it. That will be sensed as path differences at the dark port, so for our purposes that's not a full win......

Cheers, Mike.

( edit ) BTW I have a Canon printer called 'Laser Shot LBP 3000'. :-)

I have made this letter longer than usual because I lack the time to make it shorter. Blaise Pascal

Simplex0
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I think they originaly

I think they originaly regarded this to be just 'noise'
http://en.wikipedia.org/wiki/Cosmic_microwave_background_radiation

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