霍金 腾讯we大会 英语演讲稿
I have been asked to address you today, on the role of earth and humans in the context of the universe. I can best do this by reflecting on humanity’s future, and examining the options for us to explore space for possible habitable planets. My purpose today is to ask you two questions.
One reason is that the earth is becoming too small for us. In the last two hundred years the growth has become exponential, that is, the population grows by the same percentage each year. Currently the rate is about 1.9 per cent a year. This may not sound very much, but it means that the world population doubles every forty years. I will celebrate my 80th birthday in 2022, and in my lifetime, the world’s population has quadrupled.This exponential growth cannot continue into the next millennium. By the year 2600, the world’s population would be standing shoulder to shoulder, and the electricity consumption would make the Earth glow red hot. This is untenable.
But I am an optimist. I believe we can avoid this potential for Armageddon, and the best way for us to do this, is to move out into space, and explore the potential for humans to live on other planets. But what would be the justification. Aren’t there better causes here, on Earth. In a way, today’s situation is like that in Europe before 1492. People might well have argued that it was a waste of money, to send Columbus on a wild goose chase. Yet the discovery of the New World, made a profound difference to the Old. It became a Utopia for the disenfranchised, when other options seemed closed. Spreading out into space will have an even greater effect.
It will completely change the future of the human race, and maybe determine whether e have any future at all. It won’t solve any of our immediate problems on planet Earth, but it will give us a new perspective on them, and cause us to look outwards rather than inwards. Hopefully, it would unite us to face the common challenge.
What will we find when we go into space. Is there alien life out there, or are we alone in the universe. We believe that life arose spontaneously on the Earth, and evolved to be supremely compatible with the Earth’s resources. So it must be possible for life to appear on other suitable planets. But even if the possibility of life appearing on a suitable planet is very small, since the universe is infinite, we can assume that life would have appeared somewhere. If the probability is very low, the distance between two independent occurrences of life would be very large. The Moon and Mars are the most obvious sites for space colonies in the solar system. Mercury and Benus are too hot, while Jupiter and Saturn are gas giants, with no solid surface. The moons of Mars are very small, and have no advantages over Mars itself. Some of the moons of Jupiter and Saturn might be possible. Europa, a moon of Jupiter, has a frozen ice surface. But there may be liquid water under the surface, in which life could have developed. How wan we find out. Do we have to land on Europa, and drill a hole.
Interstellar travel must be a long-term aim. And by long-term, I mean over the next two hundred to five hundred years. However, there is an alternative. Last year I joined with the entrepreneur, Yuri Milner, to launch Breakthrough Star Shot, a long-term research and development program, aimed at making interstellar travel a reality. If we succeed, we will send a probe to Alpha Centauri, out closest star system to the Solar System, within the lifetime of some of you here today. Breakthrough Star Shot is a real opportunity for man to make early forays into outer space, with a view to probing and weighing the possibilities of colonisation. It is a proof of concept mission, and works on three concepts: miniaturised space craft; light propulsion; and phase-locked lasers, a fully functional space probe reduced to a few centimetres in size will be attached to a light sail. Made from meta materials, the light sail weighs no more than a few grams. It is envisaged that a thousand Star Chips and light sails, the nano craft, will be sent into orbit. On the ground, an array of lasers will combine into a single very powerful light beam. The beam is fired through the atmosphere, striking the sails in space, with tens of gigawatts of power. The idea behind this innovation is that the nano craft ride on the light beam. Not quite to the speed of light, but to a fifth of it, or one hundred million miles an hour. Such a system could reach Mars in less than an hour, reach Pluto in days, pass Voyager in under a week, and reach Alpha Centauri in just over twenty years. Importantly, the Star Chips trajectories may include a fly-by of Proxima B, the earth-sized planet that is in the habitable zone of its host star. Alpha Centauri, Only this year Breakthrough and the European Southern Observatory joined forces to further a search for habitable planets in Alpha Centauri. So far, so possible. However, there are major challenges. A laser with a gigawatt of power, would provide only a few newtons of thrust. But the nano craft compensate for this, by having amass of only a few grams. The engineering challenges are immense. The nano craft must survive extreme acceleration, cold, vacuum, and protons, as well as collisions with junk such as space dust. In addition, focusing a set of lasers totalling one hundred gigawatts on the solar sails will be difficult due to atmospheric turbulence. There are serious questions. How do we combine hundreds of lasers through the motion of the atmosphere, how do we propel the nano craft without incinerating them, and how do we aim them in the right direction. Then we would need to keep the nano craft functioning for twenty years in the frozen void, so they can send back signals across four light years. But these are engineering problems, and engineers challenges tend, eventually, to be solved. As it progresses into a mature technology, other exciting missions can be envisaged. And if Breakthrough Star Shot should send back images of a habitable planet orbiting our closest neighbour, it could be of immense importance to the future of humanity.
I hope I have attempted to answer the questions I set at the beginning of my talk, The human race has existed as a separate species for about two million years. Civilization began about ten thousand years ago, and the rate of development has been steadily increasing.
