Spectrum wars: The battle for the airwaves

 作者:羊舌湘     |      日期:2019-03-15 05:13:01
Enrico Sacchetti/Millenium Images, UK By Stephen Battersby DECADES ago, the ether was a peaceful wilderness. With a sensitive radio ear, you could just about pick up the faint sounds of nature: the hiss of ancient cosmic microwaves, the delicate drumbeats of spinning neutron stars, the crackle and low whistle of lightning strikes. Then came radio and TV, their hulking transmitters filling the atmosphere with electromagnetic noise. Now they have been joined by mobile phones, GPS receivers, CCTVs, wireless broadband connections and all manner of other stuff, fracturing the once-pristine airwaves into a crazy cacophony. Even cars have Wi-Fi hotspots that can’t be disabled and wireless sensors that constantly communicate their status with the dashboard computer. “There are transmitters in everything,” says astronomer Harvey Liszt. “And they’re mobile.” Liszt works at the US National Radio Astronomy Observatory in Virginia, and he knows the problems this causes. His kind need pin-drop quiet to detect emissions from across the cosmos, produced by interstellar molecules that might be early stages in the emergence of life, or clouds of hydrogen that will soon form stars, or giant galaxies where black holes generate plumes of hot gas. As the airwaves fill up with chatter, that quiet is becoming increasingly difficult to find. Right now Liszt and his colleagues are squaring up to do battle for a fundamental right – their right to silence. The clamour for spectrum space affects us all. It would be no good if your TV signal cut out every time you made a phone call,