Gravity lenses can make a galaxy-wide Internet possible

As Carl Sagan once said, “The sky is calling to us. If we don’t destroy ourselves, we will one day 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 want them to call home and tell us what they found. The stars are far away, so the probes will have to make a very long-distance call.

We are currently communicating with space probes throughout the solar system via the Deep Space Network (DSN). This is a collection of antenna stations around the world. Each station has one large 70-meter dish and several smaller dishes. Such large radio dishes are necessary because the signals from a space probe are rather weak and become weaker with increasing distance.

If we are going to send probes to other stars, we will need an interstellar communication network. Maybe a whole universe of the Internet. But we still don’t know how to make one. Although we can send powerful radio signals into space, the strength of these signals gets weaker over star distances. Most of what we emit could not be detected after a few light years, given our current technology. Several solutions have been proposed, such as using focused laser light, but a new study looks at using gravity lenses to get the job done.

Radio signals are a good choice for interstellar distances because they can transmit a large amount of data with relatively low power. That’s why we use radio for interplanetary communication. The disadvantage is that because radio waves have a long wavelength, it is difficult to focus in one direction. We can focus a narrow beam of laser light on a particular star, but we cannot easily focus a narrow beam of radio light. And our radio signals will have to be focused to transmit light years.

This new study looks at how radio signals can be focused by the sun or nearby stars. Because stars gravity twist the space around them, light passing near a star can be focused by gravity. This effect can be used to focus radio light in the same way that a glass lens focuses optical light. In this new article, Claudio Maccone did some basic calculations of the kind of bandwidth one might get between the sun and nearby stars like Alpha Centauri and Barnard’s Star. The data rate can be on the order of kilobits / second, which is on the order of the old Internet dial-up days. Not great by modern standards, but certainly enough to transfer usable images and data from another star.