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How far have our signals traveled?

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posted on Dec, 14 2013 @ 05:05 AM
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ignorant_ape
the theoretical range of RF propogation and its actual rage , at which a coherent signal can be received = light years apart [ pun intended ]


EIRP vs ERP (Equivalent Isotropically Radiated Power vs Effective Radiated Power) is different in space. Its all about the range of frequencies. In certain frequency windows EIRP and ERP are one and the same.




posted on Dec, 14 2013 @ 05:11 AM
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reply to post by JadeStar
 


the inverse square rule is an equal frequency inhibitor , please cite your claim



posted on Dec, 14 2013 @ 05:26 AM
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ignorant_ape
reply to post by JadeStar
 


the inverse square rule is an equal frequency inhibitor , please cite your claim


The inverse square law applies equally to EIRP and ERP.

I take the inverse square law for granted, as do most people who study this subject at any length as it only talks about the power of a signal as it propagates through free space. It says nothing about receiver sensitivity. Nor other inhibitors or magnifiers (ie: the scenario of using a gravitational lense).

I thought you were talking about other inhibitors such as earth layer propagation or scintillation due to ionized gasses in interstellar clouds, etc.

And the inverse square law has little to do with the effect of a gravitational lens.

We're essentially talking about two different things.

I cited Claudio Maccone's paper previously.
edit on 14-12-2013 by JadeStar because: (no reason given)

edit on 14-12-2013 by JadeStar because: (no reason given)



posted on Dec, 14 2013 @ 05:37 AM
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Another fun graphic:



Known star systems within 25 parsecs (81.5 light years)
The diagram displays 2829 objects in 2089 star systems known as of 2012 in the RECONS database.

Stars are colored based on the actual color (Johnson V filter brightness - 2MASS K filter brightness) of the SYSTEM PRIMARY. Numbers denote the number of components in the system; P stands for planets, which are counted separately. The stars are sized by how far above or below the main sequence (how much larger or smaller than a "normal" star) they are.

White circles and line = Celestial Equator (Dec=+00d) and Vernal Equinox (RA=00h00m Dec=00d00m), plotted at 5, 10 and 25 parsecs.

Blue circles and line = Galactic Equator and Galactic center (17h49m -29d00m), plotted at 10 and 25 parsecs.


From: The RECONS database


Within this sphere it is estimated that there are between 510-621 Habitable Earth sized planets. These are defined as:

Earth-size Planet = a planet with a radius between 0.5 to 2.0 Earth radii or a mass between 0.1 to 10 Earth masses.

Habitable Zone (HZ) = the region around a star where an Earth-size planet could support liquid surface water. The size of this region depends on the luminosity and temperature of the star.


SO...... In answer to the original poster, the answer is that around 600 or so habitable worlds would have received signals from Earth since they became powerful enough and high enough in frequency to escape our ionosphere. (Roughly 80-90 years as opposed to 110).

Something else to consider: The most likely thing they would be able to detect would not be radio/TV signals but military search and early warning radars which are much more powerful and directing most of that power outward.


References:

Leconte, Jérémy, Forget, Francois, Charnay, Benjamin, Wordsworth, Robin & Pottier, Alizée 2013, Nature - Increased insolation threshold for runaway greenhouse processes on Earth-like planets

Kasting, James F., Kopparapu, Ravi, Ramirez, Ramses R., & Harman, Chester 2013, ArXiv e-prints - Remote Life Detection Criteria, Habitable Zone Boundaries, and the Frequency of Earthlike Planets around M and Late-K Stars

Kopparapu, Ravi Kumar 2013, The Astrophysical Journal - A Revised Estimate of the Occurrence Rate of Terrestrial Planets in the Habitable Zones around Kepler M-dwarfs

Petigura, Erik A., Howard, Andrew W., & Marcy, Geoffrey W. 2013, ArXiv e-prints - Prevalence of Earth-size planets orbiting Sun-like stars
edit on 14-12-2013 by JadeStar because: (no reason given)



posted on Dec, 14 2013 @ 06:28 AM
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This is all very good. But why haven't we received a television/radio signal/broadcast from the neighbourhood as outlined in this thread. The timeframe spans numerous stars/planets. Surely if we expect them to have received our broadcasts in this span then perhaps we could have expected to have been in receipt of any that they have sent?



posted on Dec, 14 2013 @ 06:59 AM
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I believe JPL is still receiving signals from Voyager? something like half a watt? (no, I don't mean the spacecraft with Gerry Ryan on board) Voyager is just about to enter the Oort cloud I believe? Roughly a light year from Earth.



posted on Dec, 14 2013 @ 07:35 AM
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Krazysh0t
reply to post by boymonkey74
 


Not likely, even if you were in that bubble, our broadcast signals would be indistinguishable from background noise. It is pure fantasy to believe that our broadcast signals would ever be picked up by another civilization. They'd have to be actively searching for the signals and even then they'd probably wouldn't find them.


Correct.
As electromagnetic wave travel into a greater and greater expanse, their power divides until it is beneath the background noise. Not to mention obstacles that absorb (anachoic) those same waves, such a microscopic dust particles, and convert them into heat.



posted on Dec, 14 2013 @ 10:35 AM
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pikestaff
I believe JPL is still receiving signals from Voyager? something like half a watt? (no, I don't mean the spacecraft with Gerry Ryan on board) Voyager is just about to enter the Oort cloud I believe? Roughly a light year from Earth.


Voyager 1 is not yet in the Oort cloud. Scientists think it crossed the heliopause (the boundary where the solar winds pressure is not strong enough to push back the interstellar cosmic radiation) sometime around August of 2012 -- although they didn't realize that it did until the data was fully analyzed a year later. It is about 17.5 light hours way from Earth, which equates to about 0.002 light years.

That also equates to about 125 Astronomical Units (or AU, 1 AU being the distance between the Earth and Sun). The hypothesized Oort Cloud is believed to begin at about (at its nearest) maybe 2000 AU or more from the sun -- almost 20 times farther out than the current location of Voyager 1.

Voyager 2 is not as far out, and has not yet crossed the heliopause. Voyager 2 is about 14 light hours from Earth (about .0015 light years).

Voyagers 1 and 2 will take about 17,000 to 18,000 more years to reach the distance of one light year from Earth.



posted on Dec, 14 2013 @ 10:45 AM
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bally001
This is all very good. But why haven't we received a television/radio signal/broadcast from the neighbourhood as outlined in this thread. The timeframe spans numerous stars/planets. Surely if we expect them to have received our broadcasts in this span then perhaps we could have expected to have been in receipt of any that they have sent?


Because:

1) We don't really have a receiving set up sensitive enough to detect even our own TV/Radio if we were located at the next closest star system, Alpha Centauri. Read the old 1970s Project Cyclops study. That's about the scale of the project you'd have to build to do it. The Square Kilometer Array will be a big upgrade over current instruments for this purpose including Arecibo. However, most of its work will NOT be looking for such signals but rather, traditional radio astronomy.

2) We haven't been looking very long or in a sustained way. Most SETI until recently was done for a few days on borrowed telescopes every few years. Hardly a search at all.

3) We have not covered the frequencies WE use for radio/tv in most SETI searches. LOFAR would do that when it comes online but again, its not a purpose built instrument and it lacks the sensitivity to pick up our own signals at interstellar distances.

4. Look at this graph. This is the search space that SETI has covered in the radio spectrum so far:




5. They may not even be using high powered radio transmitters for such communications anymore. We hardly do compared to 30-40 years ago.

6. They don't exist nearby. As has been mentioned signal strength falls off with distance. The only thing we transmit that could be picked up by OUR receiving technology* at interstellar distances is military early warning radar and the planetary radar at Arecibo and other smaller installations (such as the ones that have been used to send our intentional interstellar messages.).

Contrary to popular belief SETI mostly is looking for intentional beacon signals, obscenely (by our standards) large transmitters (such as what we use for planetary radar) which happen to be pointed in our general direction. Or Type I or Type II civilizations who choose to turn waste energy into radio signals (for whatever purpose, beamed propulsion perhaps?).

We just don't have a sensitive enough instrument to really look for "Galactic TV" if it is no stronger than our own.

Though if we could somehow fly one of our own big radio telescopes out to 550 AU from the Sun, now you're talking!

*Note: There is no reason to believe we've somehow reached the pinnacle of radio sensitivity or that another older civilization hasn't developed a more sensitive receiving set up. What is not distinguishable from noise for us may very well be fairly clear to them.

edit on 14-12-2013 by JadeStar because: (no reason given)



posted on Dec, 14 2013 @ 11:49 PM
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reply to post by JadeStar
 


Thanks for that Jade. Good read.



posted on Dec, 15 2013 @ 07:25 PM
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Good information. Makes you wish for a return message from someone just far enough out of reach to make us up our listening but not close enough for an immediate visit.



posted on Dec, 15 2013 @ 08:18 PM
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I made this video back in November using Celestia. I don't know why I forgot about it since the reason I made it was because this subject often comes up.

In it you see how far our technological footprint in the Galaxy goes out to, not just for radio but for things like city lights and waste heat which also are detectable at interstellar distances.

These are the "fingerprints" that would tell a curious species that not only is life on Earth but that some of that life has technology.


It should be noted that our planet's loudest "signal" that it has life of any sort has be been broadcast not by us humans but by bacteria, microbes, etc for about 3.8 billion years.

Here is how our Earth's spectrum would appear to someone else out there:



Due to the effect these tiny microbes have on the composition of the Earth's atmosphere it is possible that Earth is on many lists of planets with life of any alien species with large scale telescopes out to a 3.8 billion light years distance in any given direction. The size of the telescope they'd need to detect this "signal" would be based upon how far away from us they would be.

That's far enough away that in theory, a civilization in the next galaxy (Andromeda) could have known life existed on Earth for the last billion years if they had a massive array of space telescopes.

However, we now have this technology and could mount such a search for planets with at least simple life using a large space telescope of the kind described by several researchers in these recent videos of session on Astrobiology and Exoplanets in the US House of Representatives:




We could look at planets around most of the nearby stars out to about a 1,000 light year radius, perhaps more depending on the size of the telescope.

Sadly, while we in the above ground world of science wait for such telescopes to be funded, the black budget world likely already has them operating, they're just pointed at the earth rather than at exoplanets as was pointed out 1 minute and 30 seconds into the following video:




Also is possible to detect the waste heat of an alien civilization with a massive telescope, bigger than the largest planned optical/near-IR telescope (E-ELT) using a telescope called Colossus (which would be entirely privately funded by the way.)


The Colossus Telescope Web Site

I even wrote a short story which sort of ties these things together in a sci-fi scenario that may become sci-fact in the next 10 to 20 years or so:

ATS: Astronomers Detect First 'Clear Signs of Civilization' Beyond Earth - How will you react?
edit on 15-12-2013 by JadeStar because: (no reason given)

edit on 15-12-2013 by JadeStar because: (no reason given)




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