Gravitational lenses could enable a galaxy-wide Internet

Magnification of a radio signal with gravitational lenses. Credit: Claudio Maccone

As Carl Sagan once said, “Heaven calls us. If we don’t destroy ourselves, one day we will venture to the stars.” And our first emissaries to the stars will be robotic probes. These interstellar probes will be largely autonomous, but we will want to communicate with them. At the very least, we’ll want them to call home and tell us what they’ve discovered. The stars are distant, so the probes will have to make a very long-distance call.

Currently, we communicate with space probes throughout the solar system through the Deep Space Network (DSN). This is a collection of antenna stations located around the world. Each station has a 70 meter large plate and several smaller plates. These large radio dishes are necessary because the signals from a space probe are quite weak and become weaker as distance increases.

When we start sending probes to other stars, we will need an interstellar communication network. Perhaps a galaxy-wide Internet. But we still don’t know how to make one. Although we can transmit powerful radio signals into space, the strength of these signals weakens at stellar distances. Most of what we transmit could not be detected beyond a few light years given our current technology. Various solutions have been proposed, such as the use of focused laser light, but a new study looks at the use of gravitational lenses to get the job done.

Radio signals are a good choice for interstellar distances because they can transmit a good amount of data at relatively low power. That is why we use radio for interplanetary communication. The downside is that because radio waves have a long wavelength, they are difficult to focus in only one direction. We can point a narrow beam of laser light at a particular star, but we cannot easily focus a narrow beam of radio light. And our radio signals will need to be focused so that they are transmitted light years away.

This new study looks at how radio signals could be focused by the sun or nearby stars. Since stars gravitationally warp the space around them, light that passes close to a star can be gravitationally reflected. This effect can be used to focus radio light in a similar way to the way a glass lens focuses optical light. In this new article, Claudio Maccone did some basic calculations on the kind of bandwidth one could get between the sun and nearby stars like Alpha Centauri and Barnard’s Star. The data rate could be on the order of kilobits / second, which It’s on the order of the old days of dial-up internet. Not great by modern standards, but certainly good enough to convey useful images and data from another star.

Cosmic lens reveals faint radio galaxy

More information:
The galactic Internet is possible thanks to the gravitational lens of the stars. arXiv: 2103.11483v1 [astro-ph.GA]

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