Long Distance Call

E.T. managed to call home with a Speak and Spell, buzzsaw blade, and an umbrella. The reality of interstellar communication is a bit more complicated. Space is really, really big. The power needed to transmit a signal across the void is huge. However, rather than using super high power transmitters, recent research by Stephen Kerby and Jason T. Wright shows that we could make use of a natural signal gain boost built into solar systems – the gravitational lensing of a solar system’s star. Networking a series of stars as nodes could get signals across vast tracts of the Milky Way. And we may be able to detect if our Sun is already part of an alien galactic communication network.

Distant Satellites at the far reaches of the solar system may use the natural focusing of light by the Sun to communicate across space – c. NASA

Like a heavy ball placed on a trampoline, a massive object such as a star will cause space itself to curve creating a “gravity well.” Both mass and energy travelling through curved space will follow that curve. For example, our orbit around the Sun is literally the Earth following the curve in space made by our star’s mass. As light travels through space, its path also follows these curves causing the light to bend. The effect is similar to how light is bent by a glass lens which is why the bending of light due to gravity is called “gravitational lensing”. Like a lens, stars can focus a distant source of light, such as a radio signal, greatly boosting signal gain or likewise focus an outgoing signal for better transmission. Gravitational lensing is also visible to our telescopes called “Einstein Rings” as it was Einstein’s work on relativity which demonstrated mass curves space.

Depiction of a gravity well – the warping of space created by a massive object like a planet. The Moon travels through the Earth’s gravity well keeping it in orbit – c. NASA

An “Einstein Ring” created by Luminous Red Galaxy LRG 3-757 – the centre red point in the image. The horseshoe shape encircling the galaxy is a more distant galaxy behind LRG 3-757 in the background. The incoming light of the more distant background galaxy is being bent AROUND LRG 3-757 in the foreground due to gravitational lensing allowing us to see the more distant galaxy though it is
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