On 18 December 2021 I was delighted to be able to Zoom with Martin Rees over his Cambridge kitchen table and to ask about some of the implications of two recent spectacular achievements in space exploration. These are the Parker Solar Probe penetrating – and surviving in – the corona of the sun, and the launch of the James Webb telescope on Christmas Day, which according to Rees is “the most ambitious and the most expensive instrument that any scientist has ever built”. Although operating in the infra-red spectrum, it replaces the Hubble telescope which over the last thirty years has generated so much information about the universe and its origins, and so many wonderful images.

In talking about these events, Rees recalls the famous 1968 picture called ‘Earthrise’, taken by Bill Anders when he was in Apollo 8 orbiting the Moon. He feels that this is still “an iconic picture after more than 50 years, showing the Earth’s delicate biosphere contrasting with the sterile moonscape where a year later Neil Armstrong placed his footprints.” (For our article on the taking of the ‘Earthrise’ image, click here.)

The safe arrival of the Parker Solar Probe in the extended atmosphere of the Sun has been seen by some people as an equally, if not more important, step forward for humankind, as Neil Armstrong’s ‘giant leap for mankind’ on the Moon. It is the closest we have ever come to our sustaining parent star – the source of our light and heat. “It’s still a long way away from the surface of course – about eight million miles. But it’s actually in the corona, and will be taking lots of measurements and pictures to help us understand such mysteries as how solar flares occur, and why there is a solar wind which blows out past the Earth and produces the aurora when it interacts with the Earth’s magnetic field.” (For more on this, see the NASA video below).

Even Professor Rees is amazed by the extraordinary technology which has allowed the creation of these two new probes. “We can now get back clear pictures from Pluto, which is more than 10,000 times further away from us than the Moon!” He explains that “all these spacecraft are remarkable because of the sensitivity of the instruments, and of course the fact that, although they’re sensitive, they can survive in these very alien and hostile environments.” The James Webb telescope can detect a candle a million miles away, and providing it is kept satisfactorily cool by the deployment of its very large sunshield, in its destination solar orbit – which is about a million miles away from the earth – it will be able to look back so far that the wavelengths are stretched by about a factor of 20. “The very youngest galaxies will be observed by its infra-red telescope and that’s why the James Webb is going to be so important. It’ll tell us how soon after the Big Bang these first galaxies separated out, and what the stars looked like at that time.”

As well as looking back in time to the very origins of the universe, the James Webb opens up a new field of astronomy – that of trying to learn more about ‘exoplanets’, that is, planets orbiting other stars like the Sun. It seems that most stars have planets around them, which means that there are literally billions in the entire Milky Way. As Professor Rees explains: “These planets are visible in infra-red, and a small percentage of them are expected to be rather like the Earth, in the sense of being about the same size and at such a distance from their parent star that they have a surface temperature that allows water to exist. These are called ‘habitable planets’, in that they could harbour life. But of course ‘habitable’ doesn’t mean inhabited. To settle whether any of them are actually inhabited is one of the most important scientific questions of all, for which the James Webb may provide some clues. For instance, it’s thought that some of the planets orbiting other stars could be covered entirely with water – they are called ‘water worlds’. One of my colleagues at Cambridge is in a team that’s booked time on the James Webb telescope to look for them.”

The astronomer also mentions that ever bigger telescopes are now being built on the ground. These cannot do the infra-red, but they can collect more light; the new European Extremely Large Telescope (ELT) being built in Chile, for example will have a colossal mirror which is 39 metres across, and will also be able to search for exoplanets when it becomes operational in 2025.

Mentioning his forthcoming book The End of Astronauts: Why Robots are the Future of Exploration, Rees returns once again to the iconic Earthrise picture: “All these observations will just detect the radiation from the planet as a point; they won’t produce a resolved image of the planet. That’ll be much harder. It would need a huge array of telescopes in space. I say in my book that that should be a target for the year 2068, nearly 50 years from now, when we might have a huge space telescope assembled by robots. It would be very nice if a century after the famous Earthrise picture, which was taken in 1968, we could actually have an image of an Earthlike planet orbiting another star. If we think of the likely speed of technical advances, that’s not a crazy aspiration.”

The implications of all this exploratory action in remote exterior worlds, for those of us who aspire to a universal perspective, merit our profound consideration. What difference would it make to our understanding of ourselves to know that there are other intelligent life forms out there? It seems that such knowledge is now considered to be well within the grasp of our children and our children’s children.