See "Navigation And Communication In The Big Deep," here.
Anderson connects the physics of interstellar communication with the sociology of future history and we learn much more about the Swedish timeline.
Physics
"Aberration and Doppler shift affect radio too. Eventually the transmissions from Luna would enter on frequencies that nothing aboard the vessel could receive. Well before then, however, through one unforeseeable factor or another, when travel time between maser projector and ship stretched into months, the beam was sure to lose her." (p. 47)
I try to avoid excessively lengthy quotations but this is difficult when Anderson's text continues to summarize information in such a condensed form that I am unable to summarize it any further. This passage continues:
"Federoff, who was also the communications officer, tinkered with detectors and amplifiers. He strengthened the signals which he punched Solward, hoping they would give clues to his future location." (ibid.)
The people on Luna receive a message, calculate where it is from, deduce where the ship will be months later and aim their next beam there: an inexact science.
Since this is a breakfast post and since I have things to do and places to be, this communication breaks off here. However, we have neither exhausted the physics nor started the sociology.
7 comments:
Kaor, Paul!
And I was reminded of the problems involved in trying to communicate over interstellar distances when humans had only STL means of traveling. As we see in the Rustum and Directorate stories. In the Technic series, with FTL hyperdrive, people don't bother using radio like that. FAR better to send information, messages, mail, couriers, etc., by FTL.
Sean
Thanks, Paul. I wonder if in actuality:
1) The L C would be sending back a continuous string of pings back to Tera to indicate her "current" position which could narrow her location uncertainty down to a reasonable level.
2) "Elsie" wouldn't be modifying her course very much- more "point and shoot" than "a wondrous balancing of the forces at the atomic level, delicately trimming the sails for the ghostly winds of interstellar space".
3) Wouldn't the exploratory probes have sent a detailed map of the conditions of the flight plan? How much does interstellar space change over a few decades?
-Keith
Keith,
I don't know. You give us another example of thinking about an Anderson text in a way that I had not thought of.
Paul.
A Bussard ramjet, or anything else that can accelerate a spaceship at 10 m/s^2 or more continuously, should be putting out enough hot gas to make the ship conspicuous even over lightyears. So people back at the solar system should know where the ship was when the light left it. So knowing where to point a radio or laser beam to send a message to LC would not be a problem. The problem would be for the people on the LC to detect the message beam through all the noise produced by their drive. Sending a message from LC through all that hot gas would be difficult too.
Would it be feasible to modulate the drive to send a signal?
LC?
Leonora Christine.
Kaor, Jim!
That impresses me, what you said about how it should be possible to locate a Bussard ramjet STL spaceship by tracking its hot gas wake.
Ad astra! Sean
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