I have a simple question.
Why is the telescope still collecting data?
By end of seti classic most the related sky was scanned more than three times.

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I have a simple question.
Why is the telescope still collecting data?
By end of seti classic most the related sky was scanned more than three times.

Chris,
Thats actually a very good question. And i don't have the answer, but i will hazard a guess.

I suppose its still collecting data because if the Aliens did not transmit a message yesterday, they might transmit one tomorrow. In short, that is my guess!

But really you are right to question why do they need to keep recording. If you put the SETI@home search in the context of "Time", then if there are any aliens transmitting messages, we should have a recording of that message at this stage. So really if SETI has 3 recordings of the same piece of sky, it should be able to scan the same three recordings for "differences" and spot the repeating signals.

Or they should be able to keep examining the same three sets of data in greater detail as the computers get bigger and faster.

In essence, if there are ET signals to detect, they are there "today", right now. Maybe SETI needs to look closer at the data we have. But in saying that, i think many of the work units get run multiple times when they want to look at something specific.

John.

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I have a simple question.
Why is the telescope still collecting data?
By end of seti classic most the related sky was scanned more than three times.

We, humanity, have spent a sum total of 1679 seconds intentionally transmitting a message for ET to hear. If ET is like us we are going to have to listen for a long time before we happen to have the telescope pointed in the right direction and tuned to the right frequency before we hear them.

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All telescopes, from gamma rays on, explore the sky night and day in the hope of discovering some new phenomenon. The last supernova in our Galaxy exploded in 1604 and is overdue now. There should be one every 200 years according to statistics, but I have little hope of seeing one with my eyes. So Arecibo is only doing its duty as a good sentinel. Recently also Einstein@home has started crunching Arecibo data in the hope of discovering couples of pulsars orbiting each other, I am crunching those data too, besides SETI data.
Tullio

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... Why is the telescope still collecting data?
By end of seti classic most the related sky was scanned more than three times.

Part of the 'test' for whether a signal might be artificial or not is whether that signal is 'persistent'. That is, once seen, is the signal still there unchanged a few days later or a few years later?

Interference is usually transient. If the signal persists, then that becomes something worth investigating further!

Also note that Arecibo 'looks' at the sky with a very very narrow beamwidth. That is great for great sensitivity. However, it means that only a very small region of the sky is looked at at any moment. Scanning the whole sky a few times over gives an ever increasing chance of stumbling across something that may have been missed previously.


I just hope that the ET signal is not obliterated by the (terrestrial) radar blanking...

Keep searchin',
Martin

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See new freedom: Mageia Linux
Take a look for yourself: Linux Format
The Future is what We all make IT (GPLv3)

By radar blanking, I believe you either mean that certain frequencies persistently used by Earth radars are automatically eliminated from the range of frequencies scrutinized, or that these radars interfere with certain frequencies that they attempt to monitor at Arecibo. Is either of these correct? Do you know which frequencies are affected? Michael

The problem with the old seti was that it was restricted to where others were pointing the telescope. So seti ended up looking at certain areas of the sky a whole lot and other areas very little. Also the old seti had a semi restrictive look at the sky. since Arecibo is a valley, the telescope can only look at certain areas of the sky.

With multibeam we are getting 6 different areas of the sky being scanned at the same time. I can only assume the multibeam can now look further around than the regular telescope could.

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In a rich man's house there is no place to spit but his face.
Diogenes Of Sinope

any thoughts that a signal purposely sent might be rotating... sort of like a lighthouse?

I this case,.. you might need to be listening to a spot in the sky just as the "lighthouse" focus was passing through. And this would require covering the sky many many more times to find repeating signals from the same place.

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when you consider that any signal from space is likely coming from a spinning body much like earth you have to take into account the gaussian affect of both objects spinning. I had thought that the seti@home project has taken this into consideration. discussion on their abilities to detect have been discussed extensively, here.

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In a rich man's house there is no place to spit but his face.
Diogenes Of Sinope

when you consider that any signal from space is likely coming from a spinning body much like earth you have to take into account the gaussian affect of both objects spinning. I had thought that the seti@home project has taken this into consideration. discussion on their abilities to detect have been discussed extensively, here.

My understanding is that the gaussian shape that is assumed is for Arecibo scanning across a continuous (non-scanning) source. Any scanning narrow beam, like you get from a "lighthouse", would appear as a very brief pulse in any case. Far far too fast to be seen as a gaussian.

The de-chirps allow for a wide range of doppler shifts to allow for the motion of our planet on which Arecibo sits, and additionally for the assumed motion of any ET source.

Part of the detection for ET is to see if any of the signals detected have been deliberately anti-chirped at source to simulate an artificially stationary source...


In short, I'm sure that anything non-natural or 'unusual' that might be found will get chased up!

Keep searchin',
Martin

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See new freedom: Mageia Linux
Take a look for yourself: Linux Format
The Future is what We all make IT (GPLv3)

I am no radio expert.. but a radiating signal like our television signals that travel into space in all directions lose power very quickly and will become faint... most likely undetectable by anything but the closest star systems.

It seems that a signal purposely sent would need to be a focused narrow band singal..

sort of like the difference between a light bulb and a laser...

which is why i used the lihgthouse example. If you are sending out a powerful focused narrow band signal to travel long distance.. you either need to be rotating it like a lighthouse (so you have a chance of someone getting the message)... or have tons of them, from many sources, going in multiple directions to be continuous.. which I think it unlikely. It could explain why the WOW signal appeared/disappeared the way it did.

But in this case.... the current method of searching would take potentially 100's of re-scans of the sky until you found multiple indentical signals from the same location.. and they would show up as single very powerful pulses. And might even be thrown out as most likely being radar or something man made.

I guess i've been thinking and come to 3 conclusions after so much looking;

1) there's no one to find close enough for us to find them

2) there's no one trying to be found

and I think more likely

3) we are trying to find an ant in a bee hive. ( in other words.. were doing it wrong)

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I am no radio expert.. but a radiating signal like our television signals that travel into space in all directions lose power very quickly and will become faint... most likely undetectable by anything but the closest star systems.

It seems that a signal purposely sent would need to be a focused narrow band singal..

sort of like the difference between a light bulb and a laser...

which is why i used the lihgthouse example. If you are sending out a powerful focused narrow band signal to travel long distance.. you either need to be rotating it like a lighthouse (so you have a chance of someone getting the message)... or have tons of them, from many sources, going in multiple directions to be continuous.. which I think it unlikely. It could explain why the WOW signal appeared/disappeared the way it did.

But in this case.... the current method of searching would take potentially 100's of re-scans of the sky until you found multiple indentical signals from the same location.. and they would show up as single very powerful pulses. And might even be thrown out as most likely being radar or something man made.

I guess i've been thinking and come to 3 conclusions after so much looking;

1) there's no one to find close enough for us to find them

2) there's no one trying to be found

and I think more likely

3) we are trying to find an ant in a bee hive. ( in other words.. were doing it wrong)

I wouldn´t say we are doing it wrong.
I compare our search to the discoveries made 400 years ago by --->Peter Ustinov met Galileo Galilei
with a simple pair of polished glasses set together and that had an (almost) immediate effect onto knowledge and thinking.
We just need more time and more scientific advances/improvements/innovations/funds!?!?
And maybe some theological faith?!?

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I am no radio expert.. but a radiating signal like our television signals that travel into space in all directions lose power very quickly and will become faint... most likely undetectable by anything but the closest star systems.

It seems that a signal purposely sent would need to be a focused narrow band singal..

sort of like the difference between a light bulb and a laser...

which is why i used the lihgthouse example. If you are sending out a powerful focused narrow band signal to travel long distance.. you either need to be rotating it like a lighthouse (so you have a chance of someone getting the message)... or have tons of them, from many sources, going in multiple directions to be continuous.. which I think it unlikely. It could explain why the WOW signal appeared/disappeared the way it did. ...

Better still, have a rotating source sending out very short but very powerful pulses. You can get much farther for your power for that case.

If so... Lets hope that Astropulse is sensitive enough and Arecibo scans enough repeats of the sky for us to pick up the required multiple pulses...


Keep searchin',
Martin

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See new freedom: Mageia Linux
Take a look for yourself: Linux Format
The Future is what We all make IT (GPLv3)

2 issues;

• 1. A signal like the "WOW" one does not necessarily mean nothing if it is not detected again. Let us consider a message like the one sent out by Arecibo at 1MW. It was sent only once and not repeated. If an ETI receives that signal and it too comments "WOW" at their end and then not find the same signal again; does it mean that the Arecibo message is nothing?
  
• 2. Looking at the Arecibo message again, that message was sent over 3 minutes. During that 3 minutes, how many arc seconds had the Earth rotated? After one light year, that same message would have spanned over how many arc minutes or even arc degrees? On that premise perhaps, the "WOW" signal was just a small part of a one time message?
  

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