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How many alien civilizations are there ?


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#121    Harte

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Posted 15 December 2012 - 01:19 AM

View Postbison, on 14 December 2012 - 06:32 PM, said:

Yes, recognized scientists have written quite seriously about the idea. Perhaps the most prominent of these, Dr. Frank Drake. A good, brief outline of the idea is found in chapter 10 of his book: 'Is Anyone Out There'? A space probe could be sent to the distance of the focal point of a star, and moved about at that distance to receive signals from different directions, coming in from the point directly behind the star.
Imagine the distances such a probe would have to traverse in order to make the slightest difference in the direction to be scrutinized.

The vast distances to stars precludes much looking around using this method - assuming current limits on attainable velocities remain in force.  On the other hand, any given position in the galaxy has the potential to "monitor" certain areas in various different directions simultaneously, considering that stars surround all interior positions in the galaxy.

I think that for the forseeable future, manufactured telescopes of different variety will provide more info than any gravitational methods.

Harte

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#122    bison

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Posted 15 December 2012 - 01:55 AM

View PostHarte, on 15 December 2012 - 01:19 AM, said:

Imagine the distances such a probe would have to traverse in order to make the slightest difference in the direction to be scrutinized.

The vast distances to stars precludes much looking around using this method - assuming current limits on attainable velocities remain in force.  On the other hand, any given position in the galaxy has the potential to "monitor" certain areas in various different directions simultaneously, considering that stars surround all interior positions in the galaxy.

I think that for the forseeable future, manufactured telescopes of different variety will provide more info than any gravitational methods.

Harte
                                                                                                                                                                                                              Granted, we probably won't be using this method ourselves, any time soon. The discussion was originally about how far away our own signals could be heard by others. These others might consider even a look at a limited area of space to be worthwhile. Our own Kepler Space Telescope, looking for indications of extra-solar planets, can only examine a small patch of the sky. It has already detected many interesting planets, even with this limitation.


#123    Harte

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Posted 15 December 2012 - 02:05 AM

View Postbison, on 15 December 2012 - 01:55 AM, said:

Granted, we probably won't be using this method ourselves, any time soon. The discussion was originally about how far away our own signals could be heard by others. These others might consider even a look at a limited area of space to be worthwhile. Our own Kepler Space Telescope, looking for indications of extra-solar planets, can only examine a small patch of the sky. It has already detected many interesting planets, even with this limitation.
Yes, and aliens could detect planets like Jupiter, and possibly Earth, in this same way.

What do you suggest, then?  Should we all jump up and wave?

Without a directed signal aimed at them from Earth, the odds that signals from Earth could be recieved by other life forms at such distances are... wait for it,

Astronomical! LOL

Really.  It ain't gonna happen.

Harte

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#124    Kludge808

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Posted 15 December 2012 - 02:38 AM

View Postbadeskov, on 14 December 2012 - 11:43 PM, said:

Edited to add a small blurp I wrote about this some years back.
Bade, you keep aiming me toward cool threads like this and I may have to make you my UM Guide.  ;-)

By the way, does all this discussion mean the voices from the Mothership hiding in the Kuiper belt - or maybe the scattered disk, I never could get where right - might not be from there at all?  Darn!

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#125    badeskov

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Posted 15 December 2012 - 03:06 AM

View PostKludge808, on 15 December 2012 - 02:38 AM, said:

Bade, you keep aiming me toward cool threads like this and I may have to make you my UM Guide.  ;-)

Kludge, old buddy...happy that you like it :) I am flattered, but I think there are much better guides than me - these days I am mostly lurking due to severe time constraints.

Cheers,
Badeskov

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#126    DONTEATUS

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Posted 15 December 2012 - 04:00 AM

I really hope we can all get over what happened today! So Sad,ITs the reason why we dont get that calling card from E.T! :innocent:

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#127    bison

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Posted 15 December 2012 - 03:20 PM

Yes. A moment of silence for the young people, their families and friends. Then let us resolve to work toward the day when such things no longer occur.


#128    bison

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Posted 16 December 2012 - 12:26 AM

View PostHarte, on 15 December 2012 - 01:19 AM, said:

Imagine the distances such a probe would have to traverse in order to make the slightest difference in the direction to be scrutinized.

The vast distances to stars precludes much looking around using this method - assuming current limits on attainable velocities remain in force.  On the other hand, any given position in the galaxy has the potential to "monitor" certain areas in various different directions simultaneously, considering that stars surround all interior positions in the galaxy.

I think that for the forseeable future, manufactured telescopes of different variety will provide more info than any gravitational methods.

Harte
   On the particular issue of the supposed difficulty of moving a space probe about to different positions, in order to reach the gravitational focal points for various star systems: Using our own solar system as a model, the sphere defining the distance of the ideal focal points is about 186 billion miles in diameter.
If we assume that star systems of interest are one degree apart on this sphere, the distance between their focal points should, I believe, be about 162 million miles. At even the very modest speed of one percent that of light, it should take about 24 hours to move from one focal point to another.
One percent of the speed of light does not seem excessively high for a civilization somewhat more technically advanced than our own. If one day were spent monitoring each system, and one day consumed in moving between focal points, over 180 system could be studied each year.

Edited by bison, 16 December 2012 - 12:35 AM.


#129    Harte

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Posted 16 December 2012 - 12:58 AM

View Postbison, on 16 December 2012 - 12:26 AM, said:

On the particular issue of the supposed difficulty of moving a space probe about to different positions, in order to reach the gravitational focal points for various star systems: Using our own solar system as a model, the sphere defining the distance of the ideal focal points is about 186 billion miles in diameter.
If we assume that star systems of interest are one degree apart on this sphere, the distance between their focal points should, I believe, be about 162 million miles. At even the very modest speed of one percent that of light, it should take about 24 hours to move from one focal point to another.
It appears that here you assume that only a change in angle is required.  However, is it not true that the star systems to be observed would need to be at least close to the same distance from the gravitational lens for that to be the case?

Obviously, signals can be corrected for variations, but my original point was that, in order to focus at any desired distance (and not just one distance) it would be necessary to alter the lens - in this case the gravitational field of the Sun.

If you were, for example, observing a star that was 25 LY away, then shifted to one that was 50 LY away, where is the adjustment for the change in distance (and not just degrees of arc?)

Telescopes would do a better job.  How about radiotelescopes mounted on both the north and south poles of every planet in our system, and maybe on a few asteroids?  That's be a nice-sized collector.

Harte

I've consulted all the sages I could find in yellow pages but there aren't many of them. - The Alan Parsons Project
Most people would die sooner than think; in fact, they do so. - Bertrand Russell
Ignorance is preferable to error; and he is less remote from the truth who believes nothing, than he who believes what is wrong. - Thomas Jefferson
Anybody like Coleridge?

#130    MistyW

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Posted 16 December 2012 - 01:01 AM

It's too bad that everything is so far away and far apart..I doubt that during my lifetime we can come up with something that will be able to traverse across thousands of light years..?


#131    Sean93

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Posted 16 December 2012 - 01:50 AM

Billions and Billions
Posted Image

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#132    Kludge808

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Posted 16 December 2012 - 01:51 AM

View PostSean93, on 16 December 2012 - 01:50 AM, said:

Billions and Billions
Posted Image
ROFLMAO!  That was a favored phrase of his.  It ranked up there with "stuff."

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#133    alexb

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Posted 16 December 2012 - 02:03 AM

Okay, I really get quite annoyed with posts like these. (I'm referring to the original post of this thread btw)
The link leads to some kind of pseudo-scientific theory, bringing in all kinds of variables in order to seem scientific. Alas it ignores one very important variable.
I could debunk the whole thing, but I'd like to focus on one specific issue; the sheer size of the universe.
What are the chances there's life out there? Well chances are pretty damn big. There's no denying that. However we can also agree on the fact that relatively speaking, life is rare. It takes some pretty specific circumstances for life to develop. My point is that people tend to forget (or are unable to fathom) how immensely big the universe is. There probably is life out there somewhere, but it's rare, and the chances that alien life is close enough for us to come into contact with it are in my opinion extremely tiny.
And I haven;t even mentioned time. Yeah that;s right time. The universe is billions and billions of years old. So there might be alien lifeforms, but they could have died millions of years ago. We only came to the show some 100.000 years ago, which is hardly a millisecond on the grand scale of things. I just get the feeling a lot of people don't have the right perspective on these things.

Edited by alexb, 16 December 2012 - 02:04 AM.


#134    bison

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Posted 16 December 2012 - 02:48 AM

View PostHarte, on 16 December 2012 - 12:58 AM, said:

It appears that here you assume that only a change in angle is required.  However, is it not true that the star systems to be observed would need to be at least close to the same distance from the gravitational lens for that to be the case?

Obviously, signals can be corrected for variations, but my original point was that, in order to focus at any desired distance (and not just one distance) it would be necessary to alter the lens - in this case the gravitational field of the Sun.

If you were, for example, observing a star that was 25 LY away, then shifted to one that was 50 LY away, where is the adjustment for the change in distance (and not just degrees of arc?)

Telescopes would do a better job.  How about radiotelescopes mounted on both the north and south poles of every planet in our system, and maybe on a few asteroids?  That's be a nice-sized collector.

Harte
     I have been using the term 'focal point' pretty loosely, to mean the minimum distance from a star, at which it can act as a gravitational lens, and the direction diametrically opposite that of the object to be observed.  Gravitational lenses are not completely analogous to optical ones, though. I read that beyond the above minimum distance, there is no specific focal length. It appears that all points farther out are in focus, regardless of the distance of the observed object. The linked article explains this  a bit:   http://www.icarusint...itational-lens/


#135    AsteroidX

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Posted 16 December 2012 - 11:48 PM

Up till now they have not tqaken much notice of us except maybe to observe.

We weill get there attention about the time our radio waves/tv transmissions etc start clogging there waves with old black and white reruns. Itll likely be like a foghorn going off in your ear while your talking on the phone to ET's. They will definently be paying us a visit when the Kardashians episodes arrive.





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