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No ET! Ever?
RE: No ET! Ever?
(February 18, 2017 at 2:30 pm)Rhondazvous Wrote:
(February 18, 2017 at 2:01 pm)Jehanne Wrote: It's much worse than that; it was not even written by those whom Jewish and Christian traditions say who wrote it, and even after it was written (upwards of a millennium "after the mythological event date for some of the Old Testament), it got changed and modified century after century.

Fixed it for youWink

Good fix.
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RE: No ET! Ever?
(February 18, 2017 at 1:00 pm)Jehanne Wrote:
(February 18, 2017 at 7:11 am)Mr Greene Wrote: I did hear one estimate of there being 1,000,000 civilized species in the Milky Way. 
Even if there were that many each would have on average over a 100 cubic light-years to inhabit without encroaching on another.

As for where to point an antenna; the Galactic plane would seem like a reasonable start.

[Image: is?FoGvJ9J6Nm-yvJbfr3-LGWbA1aOBAEBL5eLK7...height=163]

But, they would be pointing it at a moving target that is going at 675 times the speed of sound, and then, they would also have to track that target across intergalactic space.  In addition, the radio signal, even if it was a laser, could end-up being scattered away by the zillions upon zillions of atoms, molecules, dust particles, etc., scattered throughout intergalactic space.  In addition, the energy requirements, given the inverse law, would still be enormous, likely, the entire energy output of the US over the course of a year, assuming, that ET wanted their signal to picked-up by something other than the Arecibo telescope, which means, of course, that Arecibo would need to be looking at the right spot at the exact time.

P.S.  Arecibo is not equipped to pick-up laser light.

Your moving target over interstellar distances is effectively static; the stars are in pretty much the same positions as when they were observed by the Greeks / Ancient Chinese.
Quote:I don't understand why you'd come to a discussion forum, and then proceed to reap from visibility any voice that disagrees with you. If you're going to do that, why not just sit in front of a mirror and pat yourself on the back continuously?
-Esquilax

Evolution - Adapt or be eaten.
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RE: No ET! Ever?
(February 18, 2017 at 3:31 pm)Mr Greene Wrote:
(February 18, 2017 at 1:00 pm)Jehanne Wrote: But, they would be pointing it at a moving target that is going at 675 times the speed of sound, and then, they would also have to track that target across intergalactic space.  In addition, the radio signal, even if it was a laser, could end-up being scattered away by the zillions upon zillions of atoms, molecules, dust particles, etc., scattered throughout intergalactic space.  In addition, the energy requirements, given the inverse law, would still be enormous, likely, the entire energy output of the US over the course of a year, assuming, that ET wanted their signal to picked-up by something other than the Arecibo telescope, which means, of course, that Arecibo would need to be looking at the right spot at the exact time.

P.S.  Arecibo is not equipped to pick-up laser light.

Your moving target over interstellar distances is effectively static; the stars are in pretty much the same positions as when they were observed by the Greeks / Ancient Chinese.

That's false:

[Image: 8aGTbAw.gif]

And, the above is not accounting for the proper motion of stars throughout the Galaxy.  And, so, if you wanted to send a message from 100 light-years away using a directional antenna, here is the formula that you would use:

[Image: inversesquare_eq1.gif]

After that, you (or I), am going to have to convert lumens to watts:

[Image: Lumens-vs-Watts-Conversion-Formula.jpg]

Assuming 15 lm/watt, here is what I get:

1 light-year = 9460730472580800 meters

100 light years = 946,073,047,258,080,000 meters

1,000,000,000 watts = 15,000,000,000 lumens

D ^ 2 = 8.950542107481892730061252864e+35 meters squared

B = L / (4 * pi * D ^ 2)

   = 1.333619862188475648988125129197e-27 lumens / meter squared

   = 8.8907990812565043265875008613135e-29 Watts / meter squared

Sensitivity of Arecibo radio receiver:  10−26 watts per square meter.

And, so, Arecibo may be able to pick-up a very strong signal if it was looking at the right spot and the exact moment in time.
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RE: No ET! Ever?
(February 18, 2017 at 1:00 pm)Jehanne Wrote: But, they would be pointing it at a moving target that is going at 675 times the speed of sound, and then, they would also have to track that target across intergalactic space.  In addition, the radio signal, even if it was a laser, could end-up being scattered away by the zillions upon zillions of atoms, molecules, dust particles, etc., scattered throughout intergalactic space.  In addition, the energy requirements, given the inverse law, would still be enormous, likely, the entire energy output of the US over the course of a year, assuming, that ET wanted their signal to picked-up by something other than the Arecibo telescope, which means, of course, that Arecibo would need to be looking at the right spot at the exact time.

P.S.  Arecibo is not equipped to pick-up laser light.
Details. Details.

It's one thing to say something couldn't possibly exist. But to say something couldn't possibly be done is to cut off the future before we get to it.
The god who allows children to be raped out of respect for the free will choice of the rapist, but punishes gay men for engaging in mutually consensual sex couldn't possibly be responsible for an intelligently designed universe.

I may defend your right to free speech, but i won't help you pass out flyers.

Those who can make you believe absurdities, can make you commit atrocities.
--Voltaire

Nietzsche isn't dead. How do I know he lives? He lives in my mind.
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RE: No ET! Ever?
Rhonda! Haven't you been watching the movies!
Do you really want ET to find us!?

Maybe that IS our next extinction level event!
Put it this way, they didn't get here on diesel electric! Hehe
No God, No fear.
Know God, Know fear.
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RE: No ET! Ever?
(February 18, 2017 at 7:43 pm)Rhondazvous Wrote:
(February 18, 2017 at 1:00 pm)Jehanne Wrote: But, they would be pointing it at a moving target that is going at 675 times the speed of sound, and then, they would also have to track that target across intergalactic space.  In addition, the radio signal, even if it was a laser, could end-up being scattered away by the zillions upon zillions of atoms, molecules, dust particles, etc., scattered throughout intergalactic space.  In addition, the energy requirements, given the inverse law, would still be enormous, likely, the entire energy output of the US over the course of a year, assuming, that ET wanted their signal to picked-up by something other than the Arecibo telescope, which means, of course, that Arecibo would need to be looking at the right spot at the exact time.

P.S.  Arecibo is not equipped to pick-up laser light.
Details. Details.

It's one thing to say something couldn't possibly exist. But to say something couldn't possibly be done is to cut off the future before we get to it.

Arecibo is a radio telescope, and so, it would have to be redesigned.  There are, of course, optical searches for ET going on:

http://www.planetary.org/blogs/bruce-bet...earch.html

Of course, the shorter the wavelength of light that one uses for interstellar communication the more likely that it will get absorbed and/or scattered by interstellar matter.
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RE: No ET! Ever?
(February 18, 2017 at 4:20 pm)Jehanne Wrote:
(February 18, 2017 at 3:31 pm)Mr Greene Wrote: Your moving target over interstellar distances is effectively static; the stars are in pretty much the same positions as when they were observed by the Greeks / Ancient Chinese.

That's false:

[Image: 8aGTbAw.gif]

And, the above is not accounting for the proper motion of stars throughout the Galaxy. 

    

That picture you show reflects the precession of equinox.   It does nothing to change the relative positions of each star, nor increase the difficulties of targeted transmission to stars. Also, I believe the ancients regarded the heavens as being immutable in the celestial sphere, not immutably oriented with respect to earth. So the ancient's concept of where stars are would be relative to other stars, not to their location relative to the horizon. So the idea that stars seen by the ancient Greeks and Chinese would still be in pretty much the same positions is accurate. Proper motion would have made very little difference for most stars in the intervening 2000 or so years.
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RE: No ET! Ever?
(February 18, 2017 at 11:43 pm)Anomalocaris Wrote:
(February 18, 2017 at 4:20 pm)Jehanne Wrote: That's false:

[Image: 8aGTbAw.gif]

And, the above is not accounting for the proper motion of stars throughout the Galaxy.  And, so, if you wanted to send a message from 100 light-years away using a directional antenna, here is the formula that you would use:

[Image: inversesquare_eq1.gif]

After that, you (or I), am going to have to convert lumens to watts:

[Image: Lumens-vs-Watts-Conversion-Formula.jpg]

Assuming 15 lm/watt, here is what I get:

1 light-year = 9460730472580800 meters

100 light years = 946,073,047,258,080,000 meters

1,000,000,000 watts = 15,000,000,000 lumens

D ^ 2 = 8.950542107481892730061252864e+35 meters squared

B = L / (4 * pi * D ^ 2)

   = 1.333619862188475648988125129197e-27 lumens / meter squared

   = 8.8907990812565043265875008613135e-29 Watts / meter squared

Sensitivity of Arecibo radio receiver:  10−26 watts per square meter.

And, so, Arecibo may be able to pick-up a very strong signal if it was looking at the right spot and the exact moment in time.

That picture you show reflects the precession of equinox.   It has nothing to do with earth's motion or proper motions of target stars and therefore does nothing to increase the difficulties of targeted transmission.

Your original claim was, "the stars are in pretty much the same positions as when they were observed by the Greeks / Ancient Chinese." (emphasis mine).

In any case, the proper motion of the Sun around the center of the Galaxy (at nearly 700 times the speed of sound), would be sufficient to cause a narrow band radio transmission to miss the Earth, not to mention the Earth's motion around the Sun (around 60 times the speed of sound).
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RE: No ET! Ever?
(February 18, 2017 at 11:50 pm)Jehanne Wrote:
(February 18, 2017 at 11:43 pm)Anomalocaris Wrote: That picture you show reflects the precession of equinox.   It has nothing to do with earth's motion or proper motions of target stars and therefore does nothing to increase the difficulties of targeted transmission.

Your original claim was, "the stars are in pretty much the same positions as when they were observed by the Greeks / Ancient Chinese." (emphasis mine).

In any case, the proper motion of the Sun around the center of the Galaxy (at nearly 700 times the speed of sound), would be sufficient to cause a narrow band radio transmission to miss the Earth, not to mention the Earth's motion around the Sun (around 60 times the speed of sound).

I suspect the diameter of the earth's orbit around the sun would be way smaller than the dispersion diameter of radio or laser signal pulse or beam sent to us from the likely distance of any technologically comparable civilization.  So earth's motion around the sun doesn't matter.  Either much of the solar system will be illuminated by the signal, or it won't be.  Conversely the motion of the earth around the sun also won't make our transmission miss the target for the same reason.

The proper motion of stars caused by our and the star's independent orbit around the Milky Way isn't a real tough problem.  We can detect the proper motion of some near by star being caused by the small pull of  planets.   We can also measure the radial motion of the star to an even higher degree of precision, thanks the efforts put into exo-planet searches over the last 25 years or so. So we can define the motion of nearby stars in 3 dimensions to extremely high degree of accuracy and precision.

The main problem is the measuremeant of the absolute distance to the star.  We don't have the ability to measure stellar distances to a comparable degree of accuracy.   So we can't tell with anything close to the same degree of precision how long it will take exactly for a signal to reach the target star.  Hence unless we blanket the sky with signals, it would be very tough for us to send any short pulse signals in such a way that it would arrive at the same place and time as the target.
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RE: No ET! Ever?
(February 19, 2017 at 12:02 am)Anomalocaris Wrote: Hence unless we blanket the sky with signals, it would be very tough for us to send any short pulse signals in such a way that it would arrive at the same place and time as the target.

As I pointed out earlier, the Wow signal may have been such an interstellar beacon:

Quote:Other hypotheses include a rotating lighthouse-like source, a signal sweeping in frequency, or a one-time burst.

https://en.wikipedia.org/wiki/Wow!_signa...27s_origin

Again, in a radio transmission, one is faced with either a directional antenna (such as AM radio) or an omnidirectional transmission (such as FM).  The Sun is omnidirectional, but per Einstein's famous E = m * c^2, there is no way that we or anyone else in the Universe will ever be able to generate the equivalent energy of 10,000,000 nuclear bombs per second.  And, so, a directional transmission is the best bet, but the more narrow the transmission (such as a laser), the near certain result is scattering and/or defection of the beam while it propagates the tremendous distances of interstellar space, and given the 300 or so billion stars in the Galaxy, where does one point the beam to?  In addition, someone on the receiving end has to be listening, and we, as a species, are simply not doing that.  The Ohio State Big Ear telescope is now a golf course!

And, so, the conclusion that ET is nowhere to be found because ET does not exist is at least premature.
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