Jump to content

Longest Running Thread EVER


Recommended Posts

Re: Longest Running Thread EVER

 

That's one; a couple of others as well.

 

I went to a meeting Saturday where Frank Drake was present and did a lengthy discussion of the famous Drake Equation, and I've got some thoughts rumbling around partly formed from that. Haven't put those into a thread yet.

Link to comment
Share on other sites

Re: Longest Running Thread EVER

 

One point is that the uncertainty in N is dominated by the uncertainty in the most uncertain factors, since it's a simple product. Those are the f sub i (fraction of planets with life on which the life evolves to intelligence) and L (lifetime of a technological civilization, or more precisely, the length of time a technological civilization pours radio waves copiously into space) terms. Drake expects our own civilization's lifetime may be short, not because it will collapse and end, but because we are moving away from large-scale high-powered radio emission. TV stations are being replaced by cable and by satellite TV (the latter emit MUCH less power than the ground stations), and the BMEWS radars are being replaced by systems with much lower emitted power and much larger bandwidth, both of which drastically decrease the "visibility" of a planet to anyone eavesdropping by radio at interstellar distance.

Link to comment
Share on other sites

Re: Longest Running Thread EVER

 

One point is that the uncertainty in N is dominated by the uncertainty in the most uncertain factors' date=' since it's a simple product. Those are the f sub i (fraction of planets with life on which the life evolves to intelligence) and L (lifetime of a technological civilization, or more precisely, the length of time a technological civilization pours radio waves copiously into space) terms. Drake expects our own civilization's lifetime may be short, not because it will collapse and end, but because we are moving away from large-scale high-powered radio emission. TV stations are being replaced by cable and by satellite TV (the latter emit MUCH less power than the ground stations), and the BMEWS radars are being replaced by systems with much lower emitted power and much larger bandwidth, both of which drastically decrease the "visibility" of a planet to anyone eavesdropping by radio at interstellar distance.[/quote']

 

I thought I heard/read that somebody showed that all of our transmissions would fade to the point of being overcome by background static within a "small" distance. And IIRC, that distance was less than the distance to Alpha Centauri, maybe less than half the distance.

Link to comment
Share on other sites

Re: Longest Running Thread EVER

 

Analog TV signals rapidly become demodulated (so that you have no hope of decoding the programming content), but the still have a whopping amount of power in the central carrier frequency (which has a narrow frequency range), and that really stands out against a background. The same thing is true for old-style radar systems, where there was lots of power sent out in a very narrow frequency interval. While the information content in those signals gets lots quickly due to the dispersion in the ISM, the lots-of-power-in-narrow-band characteristic does not. That stands up very well over long distances, and you can hope to detect that over kiloparsec ranges with large radio telescopes.

 

Both of those technologies are changing (or have changed), largely because receiver technology has improved and got cheaper. The ballistic missile radar systems are going broadband with rapid frequency changing, because those are MUCH harder to jam. TV is going digital, which doesn't require the central carrier. Also, old-style central broadcast stations seem to be going away slowly in favor of cable or satellite distribution, both of which release many orders of magnitude less power into space.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Unfortunately, your content contains terms that we do not allow. Please edit your content to remove the highlighted words below.
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...