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Science, we are repeatedly told, is the most reliable form of knowledge about the world because it is based on testable hypotheses. Religion, by contrast, is based on faith. The term 'doubting Thomas' well illustrates the difference.
It is possible that a scientific discovery will be made that humans will later regret because it has awful consequences. The problem is, we probably would not know in advance and, once the discovery is made, it cannot be undiscovered.
The language of chemistry simply does not mesh with that of biology. Chemistry is about substances and how they react, whereas biology appeals to concepts such as information and organisation. Informational narratives permeate biology.
The vast majority of terrestrial species are in fact microbes, and scientists have only begun scratching the surface of the microbial realm. It is entirely possible that examples of life as we don't know it have so far been overlooked.
Perhaps the best motivation for going to Mars is political. It is obvious that no single nation currently has either the will or the resources to do it alone, but a consortium of nations and space agencies could achieve it within 20 years.
Science can proceed only if the scientist adopts an essentially theological worldview. ..even the most atheistic scientist accepts as an act of faith the existence of a law-like order in nature that is at least in part comprehensible to us.
"Are we alone in the universe?" This is a question which goes back to the dawn of history, but for most of human history it has been in the province of religion and philosophy. Fifty or something years ago, however, it became part of science.
Most life on Earth is microbes. we've only just scratched the surface of the microbial realm. Probably less than .1% of microbes have been classified let alone cultured or had their genes sequenced, so really that microbial realm is a mystery.
I think if we're going to send messages to the stars then it needs a great deal of thought that it's something that should involve the entire not only scientific community, but the entire world community. We need to think very carefully indeed.
When I was a student almost nobody thought there was any life beyond Earth. Today it's fashionable to say that there is life all over the place, that the universe is teeming with it, but the scientific facts on the ground haven't really changed.
For me, science is already fantastical enough. Unlocking the secrets of nature with fundamental physics or cosmology or astrobiology leads you into a wonderland compared with which beliefs in things like alien abductions pale into insignificance.
In the 1990s I began to study the prospects that life could spread from Mars to Earth or maybe Earth to Mars and that maybe life began on Mars and came to Earth, and that idea seemed to have a lot of traction and is now accepted as very plausible.
No planet is more earth-like than Earth itself, so if life really does pop up readily in earth-like conditions, then surely it should have arisen many times right here on our home planet? And how do we know it didn't? The truth is, nobody has looked.
Should we find a second form of life right here on our doorstep, we could be confident that life is a truly cosmic phenomenon. If so, there may well be sentient beings somewhere in the galaxy wondering, as do we, if they are not alone in the universe.
Clearly, some creative thinking is badly needed if humans are to have a future beyond Earth. Returning to the Moon may be worthy and attainable, but it fails to capture the public's imagination. What does get people excited is the prospect of a mission to Mars.
Cosmologists have attempted to account for the day-to-day laws you find in textbooks in terms of fundamental 'superlaws,' but the superlaws themselves must still be accepted as brute facts. So maybe the ultimate laws of nature will always be off-limits to science.
Imagine a civilisation that's way in advance of us wants to communicate with us, and assist us in our development. The information we provide to them must reflect our highest aspirations and ideals, and not just be some crazy person's bizarre politics or religion.
We know that within the solar system is very unlikely there will be anything more advanced than microbial life, but if we think outside the solar system and then, the distances are, of course, immense, then there could be Earth-like planets with more advanced form of life.
The birth of science as we know it arguably began with Isaac Newton's formulation of the laws of gravitation and motion. It is no exaggeration to say that physics was reborn in the early 20th-century with the twin revolutions of quantum mechanics and the theory of relativity.
Most research into life's murky origin has been carried out by chemists. They've tried a variety of approaches in their attempts to recreate the first steps on the road to life, but little progress has been made. Perhaps that is no surprise, given life's stupendous complexity.
The way life manages information involves a logical structure that differs fundamentally from mere complex chemistry. Therefore chemistry alone will not explain life's origin, any more than a study of silicon, copper and plastic will explain how a computer can execute a program.
Very, very slowly, the dwarf remnants of what was once our mighty sun will cool and dim, until it embarks on its final metamorphosis, gradually solidifying into a crystal of extraordinary rigidity. Eventually it will fade out completely, merging quietly into the blackness of space.
Searching for alternative life on Earth might seem misconceived, because there is excellent evidence that every kind of life so far studied evolved from a common ancestor that lived billions of years ago. Yet most of the life that exists on Earth has never been properly classified.
Traditionally, scientists have treated the laws of physics as simply 'given,' elegant mathematical relationships that were somehow imprinted on the universe at its birth, and fixed thereafter. Inquiry into the origin and nature of the laws was not regarded as a proper part of science.
No intelligent supervisor, no mystic force, no conscious controlling agency swings the molecules into place at the right time, chooses the appropriate players, closes the links, uncouples the partners, moves them on. The dance of life is spontaneous, self-sustaining, and self-creating.
Astonishingly, in spite of decades of research, there is no agreed theory of cancer, no explanation for why, inside almost all healthy cells, there lurks a highly efficient cancer subroutine that can be activated by a variety of agents - radiation, chemicals, inflammation and infection.
The temptation to believe that the Universe is the product of some sort of design, a manifestation of subtle aesthetic and mathematical judgment, is overwhelming. The belief that there is "something behind it all" is one that I personally share with, I suspect, a majority of physicists.
A permanent base on Mars would have a number of advantages beyond being a bonanza for planetary science and geology. If, as some evidence suggests, exotic micro-organisms have arisen independently of terrestrial life, studying them could revolutionise biology, medicine and biotechnology.
Mathematics is not something that you find lying around in your back yard. It's produced by the human mind. Yet if we ask where mathematics works best, it is in areas like particle physics and astrophysics, areas of fundamental science that are very, very far removed from everyday affairs.
It is hard to resist the impression that the present structure of the universe, apparently so sensitive to minor alterations in numbers, has been rather carefully thought out...The seemingly miraculous concurrence of these numerical values must remain the most compelling evidence for cosmic design.
No attempt to explain the world, either scientifically or theologically, can be considered successful until it accounts for the paradoxical conjunction of the temporal and the atemporal, of being and becoming. And no subject conforms this paradoical conjuction more starkly than the origin of the universe.
The development of artificial intelligence may well imply that man will relinquish his intellectual supremacy in favor of thinking machines. With oceans of time available for future innovation, there seems to be no reason why machines cannot achieve and surpass anything of which the human brain is capable.
An argument often given for why Earth couldn't host another form of life is that once the life we know became established, it would have eliminated any competition through natural selection. But if another form of life were confined to its own niche, there would be little direct competition with regular life.
Although gravity is by far the weakest force of nature, its insidious and cumulative action serves to determine the ultimate fate not only of individual astronomical objects but of the entire cosmos. The same remorseless attraction that crushes a star operates on a much grander scale on the universe as a whole.
Cancer cells come pre-programmed to execute a well-defined cascade of changes, seemingly designed to facilitate both their enhanced survival and their dissemination through the bloodstream. There is even an air of conspiracy in the way that tumours use chemical signals to create cancer-friendly niches in remote organs.
Cancer is not something confined to human beings. It's found in all multi cellular organisms where the adult cells proliferate, so it's widespread in the biosphere. It's a phenomenon that is deeply related to the history of life itself, so by studying cancer I think we can illuminate the history of life itself and vice versa.
Until now, physical theories have been regarded as merely models with approximately describe the reality of nature. As the models improve, so the fit between theory and reality gets closer. Some physicists are now claiming that supergravity is the reality, that the model and the real world are in mathematically perfect accord.
So how can we test the idea that the transition from nonlife to life is simple enough to happen repeatedly? The most obvious and straightforward way is to search for a second form of life on Earth. No planet is more Earth-like than Earth itself, so if the path to life is easy, then life should have started up many times over right here.
Through my scientific work I have come to believe more and more strongly that the physical universe is put together with an ingenuity so astonishing that I cannot accept it as a brute fact....I cannot believe that our existence in this universe is a mere quirk of fate, an accident of history, an incidental blip in the great cosmic drama.
If you get a drill and drill down 5km beneath the ground, it's teeming with life - millions of tiny living fossils. They resemble the earliest life forms and suggest that life started under the Ground. The bible talks of Eden as a sunny parkland with white fluffy clouds, but it probably ascended from the region that we now associate with Hell.
If we're thinking about old civilizations, those that formed a long time ago and there were stars and planets around long before Earth even existed, then these are going to be towards the center of the galaxy. That is the place to look if you think there are ancient civilizations that have made beacons or some other way of attracting our attention.
We could tell them [alien civilization] things that we have discovered in the realm of mathematical physics, but there is stuff that I would like to know. There are some famous problems like how to bring gravitation and quantum physics together, the long-sought-after theory of quantum gravity. But it may be hard to understand the answer that comes back.
The burgeoning field of computer science has shifted our view of the physical world from that of a collection of interacting material particles to one of a seething network of information. In this way of looking at nature, the laws of physics are a form of software, or algorithm, while the material world-the hardware-plays the role of a gigantic computer.
Science may explain the world, but we still have to explain science. The laws which enable the universe to come into being spontaneously seem themselves to be the product of exceedingly ingenious design. If physics is the product of design, the universe must have a purpose, and the evidence of modern physics suggests strongly to me that the purpose includes us
The problem here is that a civilization that is 1,000 light years away doesn't know we exist. They don't know that we have radio telescopes here on Earth because they see Earth as it was 1,000 years ago. Nothing can travel faster than light, so however good their instruments they can't see in affect the future. So there is no particular reason they should be sending us messages at this time.
I suppose my interest in looking for life elsewhere in the universe really dates back to my teens. What teenager doesn't look up at the sky at night and think am I alone in the universe? Well most people get over it, but I never did and though I made a career more in physics and cosmology than astrobiology I've always had a soft spot for the subject of life because it does seem so mysterious.
It's worth remembering that all technology leaves a footprint. For example, our own technology is leaving a footprint in terms of global warming, which could be detected from a long way away. One assumes that a very advanced civilization that has been around maybe millions and millions of years would have an even bigger footprint that might extend beyond its planet to its immediate astronomical environment.
Wheeler hopes that we can discover, within the context of physics, a principle that will enable the universe to come into existence "of its own accord." In his search for such a theory, he remarks: "No guiding principle would seem more powerful than the requirement that it should provide the universe with a way to come into being." Wheeler likened this 'self-causing' universe to a self-excited circuit in electronics.
Supposing we knew that up there is some alien civilization and it's sending radio signals our way we should not tell the public where that is. We could say that we've picked up a signal, but we should not tell them where for the simple reason that anybody could commandeer a radio telescope, set themselves up as some self appointed spokesperson of mankind and start beaming all sorts of crazy messages back to the aliens.
I should say we know that there are many, many other Earths out there. We're almost certain that there will be upwards of a billion Earth-like planets in our galaxy alone, so there is no lack of real estate where life might happen, but what we don't know is how likely it is given the real estate, given a wonderful pristine planet like Earth how likely is it that life will pop up inhabited? We don't know the answer to that.