Asked by Ralf Watts
This distance actually changes with improving technology. Spacecraft like Voyager 1, which is over 19 billion kilometres (12 billion miles) away, use something called the Deep Space Network of three radio telescope sites to communicate with Earth.
Using these huge radio antennae networks – the largest dishes are 70 metres (230 feet) in diameter – in Australia, Spain and California we can communicate with distant spacecraft. However, low-power transmitters on space missions mean that by the time information arrives from the outer planets, the signal power is 20 billion- times lower than that in a typical wristwatch battery.
By increasing the size and spread of the radio antennae, a weaker signal can be processed, but with the current space network, Voyager 1 has about ten years before the limit is reached.
Answered by Sophie Allan from the National Space Centre
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