Thoughts about the Definition of Life - WO Life in the Universe?? When asked what life means to me and do I believe in life elsewhere, I would develop my answer as follows: First I would like to explain why I relate such an answer to where I am. I was fortunate to have been an extraterrestrial for one week during my flight on the US Space Shuttle Challenger at the end of 1985. The experience of the difference between Space and Earth was so overwhelming that I believe sincerely that our views, our culture, our science and our understanding must depend on the Earth's environment, the main elements of this environment being nature, gravity and time. We humans obtain our information from our location in space and time, at least that is what I assume. Our knowledge and science is built upon that information. One could say that our personal view and understanding of things is adjusted to fit the information we receive. This adjustment we could call intelligence. We are obviously rather localised, both in space as well in time. How does our understanding depend on this localisation? Or equally, does the character of our understanding basically express the manner we are localised? Based on this relation, I will then answer the question: 'Is there life elsewhere?' by relating this question to similar questions that could have been asked in the past. What answer would we have got from Ptolemy, about the question: 'Is there another Earth?' Two thousand years ago Ptolemy placed the Earth at the centre of everything. Such a view went along with explaining most of the observations outside the Earth (i.e. the sky) as being directly linked to the Earth. The Earth was seen as the basis, as the centre, and there is obviously only one centre. So the answer would probably have been: 'The Earth is the Earth, the plural of Earth does not make sense'. What if we had asked Galileo: 'Is there another planetary system?' It is only 500 years since Galileo placed the Sun at the centre of the universe, corresponding to his understanding of satellites orbiting a heavy body (from his observations of the moons of Jupiter). Galileo saw our Earth, similar to orbiting satellites and developed the understanding that all the planets were circling around the Sun. His answer would have been something like: 'We see Jupiter, but that is a planet like ours and we see only one Sun!' So how can we expand this reasoning to the question of life? How can we question fundamentals, like the Earth for Ptolemy and the Sun for Galileo? I think today's fundamental is time. We don't question time in the way that Ptolemy would not question Earth and Galileo would not question the Sun. Nowadays we think of ourselves as cosmic. We believe that the laws of physics as we understand them are valid everywhere. We do not question the potential limitations of our views due to our living on the Earth. Although from the geometric point of view we are rather humble and we think of the Earth as orbiting a very common star near the edge of a rather common galaxy, we seem less humble about our position in time. We exist in the present and we go so far as to make convincing statements about when the universe started and how it all relates to our time and our existence. After the geocentric and heliocentric world, we are now in a 'chrono-centric' world. The relationship between our perceived localisation and our understanding of the universe seems apparent. For me this statement seems logical. Once accepted, the intriguing consequence is that a different understanding will result from a change in localisation. So what might happen if humanity occupies outer space? Would the change in environment, in basic forces and in the perception of time, alter everyone's understanding? If my experience in space led me to put forward new theories, would most earthlings believe me? Would I believe them myself on returning to Earth? Well this is the story as I wrote it shortly after my flight: Is Life EARTH-LIKE? Space flight, a most unusual experience Wubbo J. Ockels ESA Scientist Astronaut ESTEC Postbus 299, 2200 AG Noordwijk, The Netherlands "T-36 seconds and counting, automatic sequence start". The Shuttle computers have taken over the countdown. I was sitting already over one and a half hours in the seat, lying on my back because the Shuttle stands on its tail. "So close to launch". Two years in Houston for the basic astronaut training. Three years training and preparation as a backup for the first Spacelab flight. Now, 30th October 1985, sitting in the Challenger. I hope so badly that nothing will come in between me and the flight and that nothing goes wrong. "T-6 seconds, main engine start", I feel the Shuttle coming alive. I count loud 3.. .2.. .1... and then "Yippee", the solids go, and there goes the Shuttle, there goes the D-1 Spacelab, there I go, to space; one feels the increasing speed. Three times the weight on Earth. After two minutes, 40 km high, the two solids are burned out. With a big Jerk they separate and then... nothing! As the Shuttle was already on an almost ballistic track, you feel no gravity any more, only the acceleration of the Shuttle. This acceleration was only 1.2 g at that time, slightly more than I felt during the one-and-a half hours I waited on the pad, standing still! I thought for a fraction of a second that the engines had failed. Fortunately the forces were building up again and a smooth ride for six more minute brought us into Space. The engines stopped and we were weightless. The first thing I did was to take my pen out of my pocket and put it right in front of my nose. It stayed there. "I could move my head around it!" "We are weightless, we are in a no-force environment". Very often before I had tried to imagine weightlessness. Now it was real and… different. One big question came back to me: "Will I, being outside Earth think differently about life?... Is life Earth-like?" I think I found the greatest difference between Space and Earth to be gravity, the unavoidable gravity. The evolution of life took place on Earth and the concept of life was formed on Earth. How general is this concept? The force of gravity to which everybody is exposed all their life is always the same. I was struck by this new sensation of weightlessness, as if I had opened a door and had seen a new colour I'd never seen before, yet so real, only I had no name for it. Of course I had to stop this reflection and start work. Over 70 experiments had to be done, many of them as quickly after the launch as possible, because these experiments were to measure the onset of our adaptation to weightlessness. Some of us got sick and others enjoyed it. It was hard for me not to smile all the time. All of us worked hard and after two days we all felt great. I had no time to think more about gravity and life till the work was done after 110 orbits around the world. During the seven days I got used to the feeling of freedom - no forces, no ties to a floor. When I relaxed and closed my eyes I could even forget my body. This was the purest feeling of rest. All the forces that I felt resulted in movement caused by acceleration. I started to think again about human beings on the surface of Earth. They are always pulled down by an incredible force, or more accurately, pushed upwards by an enormous acceleration. Each second everybody goes 36 km/hr faster. That is 100 km/hr in 3 seconds, 3 million km/hr after one day, almost the speed of light after one year! The brain cannot believe that of course. As the force of gravity is always constant, we ignore it. When we sit on a chair, we sit still. Horizontal forces, however, are interpreted as a change of speed. When we feel a pressure on our back in a car, we go faster. So we have developed different attitudes to horizontal and vertical motions. How far is a friend when looking down at him from a tower 100 metres high? And how close is he when you are on the ground 100 metres away? How striking is the apparent increase in size of the Moon when it is at the horizon such that we apply our 'horizontal' view, and how small does the Moon seem to be at the zenith, straight above us? Is the brain fooling us? Of course! But how does this influence our concept of life, if it does at all? How would we think when perceiving gravity not as a static force, but as a real acceleration going faster and faster upwards? As I said, I had been thinking about this often before the flight, but I could never really convince myself that I felt gravity as an acceleration. The de-orbit burn was completed and the slowed down Shuttle fell back towards the Earth's atmosphere. Looking through the window I saw the clouds coming closer and closer. The speed at which they passed by was incredible. Then, at about 200,000 feet the air drag started to build up. A deep orange glow developed around the nose of the Shuttle. The build-up of force to 0.8g was quite sudden and my head was pulled downward. It took a large effort to lift my arm. I felt at least four times as heavy as I seemed before the flight. It was uncomfortable. Strange effects occurred due to my confused inner ear system. Whatever I looked at moved when I moved my head. I did not like it! The ride down took 20 minutes. The Shuttle touched down smoothly on the runway at Edwards Air Force base. There was a rollout and then stop, silence, but everything was heavy, damned heavy. After we got the go-ahead from our commander, we un-strapped and exercised our leg muscles before trying to stand up out of our seats. Now came one of the most impressive moments of my flight. I stood up and it was frightening. For a few seconds I felt that I had just stepped into an elevator going up at an incredible speed. All my thoughts about my perception of gravity came back immediately. I just perceived it as real acceleration! What does this gravity do to us? We are all so used to it that it must give us a distorted view. We cannot escape it. The first few nights I woke up several times, switched to acceleration, the bed was pushing me upward, speed was building up. Then I switched back to the force feeling. I was tied down by my hands and feet. Somehow suddenly this unavoidable gravity, its incredible speed and the continuous passage of time seemed to fit together naturally. Time, seen as necessary for experiencing change, to come alive. For all of us time goes with the same speed. To reach tomorrow, we all have to wait one day. As if we are on the same wave, forcing us towards the shore. It makes me think of an analogy. On the far side of a lake as flat as a mirror sits a man who is both blind and deaf. He fishes using his sensitive fingertips on a rod and noticing any movement of the water surface. If I want to communicate with him I can throw a stone into the water. The ripples will reach his float. The man will know that I am here. Now suppose I am on a boat which moves at a speed equal to the speed of the ripples which disturb the flat surface of the water. I can throw as many stones as I want into the water, but the lake in front of the boat stays flat and undisturbed. I cannot communicate with it. If I want to see that part changed, I have to wait till I am there. Just as I have to wait for tomorrow, yesterday is already disturbed, like the wake of the boat. If the analogy holds, you will ask yourself: 'What causes the boat to go, where is the engine?' Is the engine gravity? Then gravity gives us the speed at which information travels, like the ripples on the water. But that is the speed of light, 300.000 km/hr. What is then our speed in time? One hour per hour of course. This speed is one. Is it then gravity, is it Earth which pushes us towards the future? Is Earth giving us the sense of time? Do we live the way we live because we are on Earth? Is our concept of time and of life universal or does it depend on Earth? Is life Earth-like? I bet it is. Wubbo Ockels - Head of the ESA Education Office