posted on Aug, 14 2011 @ 08:58 AM
reply to post by Illustronic
You missed a couple of zeros for the radii of the Milky Way but we get your point.
One zero. Thanks for pointing it out. The radius is roughly fifty thousand light-years.
Would the first radio transmission really be the first electromagnetic signatures to leave earth?
The first that could be decoded to show they had an intelligible message contained in them – yes, I believe so. They would be very faint and
difficult to pick up unless one happened to be listening at exactly the right moment.
By the time of the Second World War, however, there were dozens of powerful shortwave transmitters blasting away around the world, using ionospheric
reflection to propagate their signals round the Earth. Much of their output would not have been reflected but simply poured out into space. That was
only the beginning; Earth as a radio source has been growing brighter ever since.
How far do you think these signatures can be detected from?
Exactly as far as they have travelled to date. 1930 really is quite a good year to start counting from, so radio (including radar, TV, etc.)
transmissions from Earth can now be detected anywhere within an globe of space 81 light-years in radius with Earth as its centre. This ‘zone of
detectability’ is, of course, expanding at the speed of light.
edit on 14/8/11 by Astyanax because: of the date.