A Question about Cosmic Background Noise

[dom_quixote]

Two Radio-Telescopes point to the same empty point in space. Obviously no astronomical signals will be expected to be captured by the two instruments. However, at least the capture of cosmic background noise is expected.

If the two Radio Telescopes have identical signal recorders operating in synchrony, will the background noise pattern of the two instruments be the same?

 

[PeroK]

A telescope points along a direction in space. Not at a single point.

 

[phinds]

Two Radio-Telescopes point to the same empty point in space.

Highly unlikely that there even IS such a place. Google "Hubble Deep Field". Telescope pointed at "empty" region but with long exposure showed thousands of galaxies.

 

[dom_quixote]

How to capture the cosmic background radiation, if wherever the radio telescope antenna points, it finds a star?
My initial idea is to check whether there is agreement in random signals captured by radio telescopes located at different points on Earth.

 

[PeroK]

My initial idea is to check whether there is agreement in random signals captured by radio telescopes located at different points on Earth.

That research project should keep you busy for a while.

 

[Ibix]

The intensity recorded will be the same, give or take atmospheric noise etcetera. I'm not sure there'd be any meaningful phase information, since you're looking at a blackbody that isn't plausibly modelled as a point source.

Probably worth doing a bit of background reading on extended blackbodies before jumping to buying telescope time.

 

[Vanadium 50]

That research project should keep you busy for a while.

We are his research. "Just as PF - we'll do the legwork for you!"

This question is too vague to be answered. What is "empty space"? What does it mean to point to a point and not a direction? What does it mean for noise to be equal? There also seems to be some coinfusion about Olber's paradox thrown in.

We can't answer the question, because it isn't even a question yet.

 

[Baluncore]

If the two Radio Telescopes have identical signal recorders operating in synchrony, will the background noise pattern of the two instruments be the same?

Define "background noise pattern".

Each telescope will have an independent random noise due to the temperature of the receiver. If you cool the receiver sufficiently, the noise floor will be limited by the cosmic background radiation, of about 3 K.
https://en.wikipedia.org/wiki/Cosmic_microwave_background
https://en.wikipedia.org/wiki/Cosmic_background_radiation

Superimposed "in" that will be the sum of all cosmic radio sources that are in the beam of the antenna. With more than one antenna, the phase of signals will be determined by the position of the sources in the two beams. For several widely separated antennas, a map of the distributed source can be made by correlating the signals. The spatial resolution of that map is much finer than the beam-width of the individual antennas.
https://en.wikipedia.org/wiki/Very-long-baseline_interferometry
If correlation of the signals can reveal additional information, then some of the signals must be the same to correlate.

 

[sophiecentaur]

If you cool the receiver sufficiently, the noise floor will be limited by the cosmic background radiation, of about 3 K.

I think what the OP is getting at is whether the background noise can be regarded as from a single source. If the experiment were to be looking at the Sun, for example and the telescopes were almost co-sited then the received signal would have very similar spectra (white noise plus interference )

In the same way, a hot resistor would produce the same waveform for two very cold identical receivers but only if the connecting leads were the same length and if the path lengths for each frequency were the same (equal dispersion). The "waveform" depends on the relative phases of all the spectral components so two identical cables could perhaps produce some level of correlation between the two signals for near equal cable characteristics.

For a real path through space and the atmosphere, I'd expect much less correlation for separated receivers - worse as the separation increases . The atmosphere affects the image quality for large optical telescopes and microwaves are only a 'bit' longer than optical waves (0.5microns to 50mm - say) so any dispersion advantage would be greater but by how much? And radio telescopes have much greater diameters than optical scopes.

I think the answer has to be NO.

 

[Klystron]

...

If the two Radio Telescopes have identical signal recorders operating in synchrony, will the background noise pattern of the two instruments be the same?

Using electromagnetism forum definitions of signal, background noise, and synchrony, while ignoring baseline displacement of your receivers, random noise or "grass" by definition should not be identical.

Edit: I wrote this reply a few hours ago but decided to post in agreement with previous replies.

 

[Baluncore]

I think what the OP is getting at is whether the background noise can be regarded as from a single source.

Your guess is as good as mine. I will wait for the OP to refine their question.

 

[dom_quixote]

That research project should keep you busy for a while.

I'm a Radio Listener and I've been studying this problem for decades.

 

[dom_quixote]

Your guess is as good as mine. I will wait for the OP to refine their question.

I have no way of refining my question. I think I was clear enough in expressing my doubt. Thank you all presented high quality arguments.

 

[sophiecentaur]

while ignoring baseline displacement of your receivers, random noise or "grass" by definition should not be identical.

If the "grass" has been generated by a common source then it will appear the same if both receivers have low enough internally generated noise. The random signals from the source can be looked upon as 'signals' and, with identical transmission paths (losses and dispersion) those signals will be received as being the same.

But there will be many aspects of the two channels / paths which will 'distort' that signal differently.