If there are aliens out there, it might not be that hard for them to find us.

That's because experts say extraterrestrial civilisations could map our planet using signals from mobile phone masts - the number of which have grown exponentially over the past 30 years.

They are now the second most powerful source of Earth's radio leakage – behind only military radar transmissions – having overtaken the commercial radio and television station powerhouses of the 20th century. 

To put this into context, each mobile tower emits a radio signal with a power of 100-200 watts, equating to a peak total leakage of four gigawatts from our planet, according to researchers at the University of Mauritius and University of Manchester.

It means that if aliens had a radio telescope equivalent to the £1.7 billion Square Kilometre Array (SKA) being built across South Africa and Australia and due to be finished by 2028, then they should just about be able to detect our 4G activity.

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