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undefined
2008-Dec-03, 08:45 PM
Hello. In the Fermi Paradox episode Dr. Gay said that we (humans) search for radio waves emitted by other civilizations but some planets atmospheres might be to thick (or for whatever reason) to allow radio signals to escape into space.


If a civilization on one of these planets were using radio signals wouldn't these signals be piling up on one another in the atmosphere? Could an instrament be used to listen to a transmission released from a source from the long past in this atmosphere? For example, if Earths atmosphere never released radiowaves could i, on this date, tune into a radio broadcast from the 1950's or pick up the broadcast of the Beatles playing on Ed Sullivan?


If X amount of our radio emissions leak out of the atmosphere than are some of these old transmissions still roaming around for detection within our grasp?


My last question out of a select few of many. If another civilization had been broadcasting is it possible that the signal has already passed us? For example, planet 'A' sends a signal towards a planet called 'B'. History of Planet 'A': They used radio signals for 150 years and then moved completely to fiber optic communication. The first waves start to enter planet 'B's range of detection within 5000 years time, relative to planet 'A'. The last wavelength leaves Planet 'B's range of detection in 5500 years. Well, during this 500 year window Planet 'B' was inhabited by dinasaurs who were to busy hunting and gathering instead of developing ways to find radio emmissions from other civilalizations. 70 million years later planet 'B' has the capability to listen to these waves but it is now 70 million years to late and the signal and even the civilization which sent it out are now long gone.

Thanks.


EDIT: I just realized there are other forums for questions like these. I am sorry if this post should be somewhere else.

01101001
2008-Dec-03, 09:58 PM
Welcome to BAUT Forum. Hey, your member name is undefined.

It's OK to ask about the podcasts here in this section about podcasts. There is also a Q&A section for general space and astronomy questions.

For others, the audio is about 17 minutes in, Episode 24, about Fermi, 07-02-19.

From the transcript (http://www.astronomycast.com/astronomy/episode-24the-fermi-paradox-where-are-all-the-aliens/):


What if their communications works in wavelengths that don't penetrate through their atmosphere?


If a civilization on one of these planets were using radio signals wouldn't these signals be piling up on one another in the atmosphere?

That's not how radio works. Radio is electromagentic energy, like light. Impinging on some matter, like an atmosphere, if it could not pass through, it would be reflected away and/or absorbed, heating the matter. It wouldn't pile up like driftwood at the boundary to be sorted through later. Same would go for our radio being partially blocked by our atmosphere.


If another civilization had been broadcasting is it possible that the signal has already passed us?

Sure. It's gone. Too late. Oh well.

WayneFrancis
2008-Dec-04, 02:12 AM
Hi undefined,
As 105 has said if we missed it then we missed it. The drakes equation asked this question is the L. How long a civilization actually tries to communicate is a big factor in finding other life. Many scientist believe there is a very good chance that we might end up killing ourselves in the next 50-100 years. Is this a common trait of life? As intelligent life comes about does it naturally tend to snuff itself out?

Good question, I would hope that if we start getting to that point that we as a race might try to set up something that broadcasts to the universe that we where here and more importantly not to make the mistakes we made.

JustAFriend
2008-Dec-04, 03:01 PM
Some radio waves (the longer wavelengths) will bounce in the atmosphere.
Shortwave listeners used to use the 'skip' to hear long distance transmissions.
AM radio stations could be heard for thousands of miles, sometimes interfering with each other if Station A and Station B were on the same frequency.
Kids used to make low-power Morse Code ham sets (QRP is the term I remember?) to try to work as far as possible with less than one watt of power.

But shorter wavelengths (VHF and up) will go right out and into space.

FM radio, TV and radar are pretty much 'line-of-sight' communications.
I don't remember where the dividing line is but that would put it at somewhere around 30-50Mhz or so that you lose the ability to skip off the atmosphere....