It takes a lot of energy to put something in orbit around Earth, and even more energy to get it free and moving toward another planet. This in an unavoidable consequence of physics as we understand them, and means that moving massive amounts of material from one planet to another, like millions of people migrating out of Earth, or the large-scale mining of the Moon, is always going to be very expensive (mining asteroids would be cheaper, as there's not much gravity to fight against, but we haven't found yet much of use in them).

'Space tourism' to low orbits is already possible and some companies are investing money on its development, but without massive advances in infrastructure and energy production, it's never going to be a mass market, or get very far away from Earth. But we know well that mass isn't the only economically interesting thing that can be shipped around, and some of the most promising applications of space aren't based on moving many objects through the Solar System.

One space-based industry that is showing an unexpectedly fast growth, although still in a very early stage, is space-based energy generation. The basic idea is to put in orbit solar panels, and then send the energy back to Earth by converting it to microwaves, which are turned back to electricity in ground stations. Although space is an expensive location for solar arrays, it avoids the loss of efficiency caused by clouds and other atmospheric effects. California power utility PG&E signed up a contract last April to begin buying space-generated power from startup Solaren Corp. beginning in 2016, and the Japanese government has recently asked local companies to participate in a project that could begin generating energy by 2030. Both of those initiatives are still tentative, but point out to the growing interest in space-based power generation.

So far, the most significant 'commodity' we have brought from space is information about our own planet, and our demand for it doesn't seem to be winding down. If anything, the growing economic and political importance of climate and ecological monitoring, together with the increasing role of satellite imaginery in warfare and security operations, suggest that real-time or near real-time satellite data will continue to be in high demand.

But the deepest effect of space has been in our imagination. Although in a very particular geopolitical climate, both the Sputnik and the Apollo XI mission were epoch-making events. Human spaceflight has lost since then most of its political impact, but discoveries achieved thanks to space-borne scientific instruments are literally changing our view of the universe. Among perhaps the most unappreciated recent revolutions in astronomy has been the detection of planets outside the Solar System or exoplanets. Most scientists had expected them to exist, but the development of methods to obtain information about them from such a long distance is nothing short of astonishing.

The discovery of new exoplanets no longer merit much attention from the press, as the number of known exoplanets exceeds the three hundreds, but as our technology and analysis improves, and new scientific instruments are put in operation, our knowledge of them is growing more quickly, we believe, that it could have been expected. It would be hard to exaggerate the shock to Western civilization that was the discovery of the true nature of the planets in the Solar System, or the importance the view of Earth from space has had in the development of our contemporary concept of the planet as an interconnected ecological and economic system. What will eventually be the full impact of our knowledge of these other planets so far away?