Invisible Stars - GPS Declassified: From Smart Bombs to Smartphones - page 72

Cook: ( shaking head and peering out the window ) You send a lieutenant on
deck for your observations?
Commander: Coast Guard cadets still learn celestial navigation, but the fact
is this equipment can provide all the navigation information we need.
Cook: What species of instrument is this? It looks like a small map on fine
paper held up to a bright window.
Commander: That is our electronic chart display. It's a video screen—a pic-
ture that changes—connected to a computer—a calculating machine—that
stores all of our maps and plots our course using gps—the Global Position-
ing System. gps can tell us our latitude, longitude, bearing and speed.
Cook: Indeed! The work of a sextant, a watch, a compass, and a log-line?
You mean this machine can take observations of the moon and stars, cal-
culate the distance, and search the lunar tables for you?
Commander: Not exactly. The information comes from the sky, but not from
natural bodies. It comes from machines called satellites that are very, very
high overhead—like tiny stars that orbit the earth, same as the moon.
Cook: Your language is quite new to me, and I am confused. It is midday.
No stars are visible.
Commander: Well, these are too small to see, even at night.
Cook: What use are invisible stars?
Commander: We don't need to see them. The satellites transmit electro-
magnetic frequencies—um, radio signals that our equipment uses to deter-
mine our position. Radio signals are very rapid vibrations that our
instruments detect with their antennas, which for them are like our ears,
but these are not sounds anyone can hear.
Cook: You steer your ship with sounds you cannot hear from stars you can-
not see?
Commander: I guess that is one way to describe it.
As this hypothetical conversation illustrates, understanding any form of
technology relies on a base of knowledge about scientific advances that pre-
ceded it. The knowledge base—or at least an awareness of capabilities, if not
a technical understanding of them—increases with each generation. Soon peo-
ple take advances for granted. The principles of navigation using latitude and
longitude have not changed, but Captain Cook would lack the knowledge base
to readily grasp the workings of gps. Meanwhile many casual users of gps
devices are ignorant about navigation methods, yet they readily adopt gps