Indeed.
The Moon is much farther away than GPS satellites, yet your iPhone camera can see the Moon just fine.
Take this to the extreme ⌠a WiFi transceiver âdetectsâ (and promptly ignores) the cosmic microwave background, which is the light of the entire universe from when it was a mere third of a million years old; which is to say that it âseesâ âstuffâ thatâs about 47 billion lightyears away. (Not a typo nor an exaggeration. Yes, the universe is âonlyâ a bakerâs dozen billion years old, but space is expanding, so things are farther away than it would take light today to reach them.)
The technological miracle here isnât detecting a far-away source. The miracle is in being heard by a far-away listener. With something thatâs probably not even as âbrightâ as the flashlight on the camera.
Imagine youâre in the middle of Denver. You can see the Rockies really easily from almost anywhere in the city. If somebody put a searchlight on the top of one of the peaks on a clear night, youâd see it without trouble. Now imagine youâre at the searchlight and your friend is in the middle of the city with a flashlight trying to send you a message with Morse code.
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