Hollywood is wrong about aliens. They don't have oddly shaped heads, bulging eyes or even an eerie green hue. Dimitar Sasselov is pretty convinced of that.
He's not even sure we'll know them when we see them. Prof Sasselov, an astrophysicist, thinks that if life exists elsewhere - and he believes it does - it will likely be based on different building blocks than ours, and so may not even be recognisable as life.
A project he's heading at Harvard University, called the Origins of Life, is trying to imagine what life would be like if it were based on different chemicals, conditions and history than we have on Earth. There's no reason life can only form under our set of circumstances, he says - or at least that's what he thinks and hopes the project will eventually prove.
People have been asking questions like "How did we get here?" and "Are we alone?" since the time of Epicurus, around 300 BC, if not earlier. And Sasselov says we probably won't have a definitive answer in the next century either.
But new tools and new data in a range of fields are allowing scientists to get closer to those answers than they ever have before. And major, interdisciplinary efforts like Harvard's Origins of Life project, and similar ones at Arizona State University, the University of Washington, and University College London (which is holding its first symposium on the subject on 11 November), are radically changing the way we search - and what we are likely to find.
Just as Copernicus revolutionised how people viewed themselves and their world 450 years ago, and Darwin did again 150 years ago, so Sasselov says we're getting close to another transformative moment.
"One morning we'll wake up with a fundamentally different view of the world and who we are," he says.
Are we alone?
This is a fertile time to be looking for life on other planets.
The Kepler Space Telescope, launched by US space agency NASA in March 2009, has spotted hundreds of planets with Earth-like characteristics. This finding has energised the field of planetary scientists; if Earth-like planets are common, then it's more realistic to think that life could be, too, says Prof Sasselov, whose book on the subject "The Life of Super-Earths" is due out in January.
He is now helping NASA design the next set of experiments for Kepler, as well as a next-generation telescope.
Kepler's field of view is only about as big as a hand stretched up toward the summer night sky, fingers splayed. The land-based telescope Prof Sasselov envisions could help scientists scan a broader swath, identifying the closest hospitable planets.
Searching for origins
The red and green lasers that Sasselov and his team pulse in the basement of the Harvard-Smithsonian Center for Astrophysics allow them to calculate wavelength shifts that indicate a planet's chemical makeup. Sasselov compares it to using a GPS system, though instead of identifying the planet's position in space, the lasers reveal its position in frequency.
But it will take a lot more than a fancy telescope and some bright lights to answer the origins of life questions. At Harvard, the Origins team also includes a geneticist, a chemist, a geochemist, an environmental chemist, and a palaeontologist - and that's just the steering committee.
The fact that scientists from all these different disciplines are sharing their progress is also big news in science, long famous for its silos. "Most universities are configured along the lines set down by Victorians - chemistry, math, physics and so on," says molecular biologist John Sutherland of the Medical Research Council in Cambridge.
The only way to approach these giant questions, says Prof Sutherland, is for scientists from different disciplines to work together, learn from each other, and suggest solutions that would never occur to people immersed in a single field.
At Harvard, team members share an informal lunch or dinner together once a month, and work meetings every week or two. Team members also have "day jobs" focusing on more short-term research, says steering committee member Andrew H. Knoll, a professor of Natural History who is now using his expertise in the environment of early Earth to help a NASA mission explore Mars.
The Origins project started with about $1m a year in funding, half to buy lab equipment and half to support graduate students. With major equipment purchased, the group now spends about $500,000 a year, mainly on students. Sasselov directs the team - in part because he volunteered, and in part because his pleasant demeanour, scientific enthusiasm and "generosity of spirit" made him a natural choice, Prof Knoll and others say.
Prof Sasselov was born in 1950 in Bulgaria, on the tiny resort island of Nesebar in the Black Sea. He is too young and lived too far from the United States to have strong memories of Neil Armstrong's walk on the moon; he can't remember when the skies first captured his imagination.
The sea that surrounded him was far more interesting, as were the ancient Greek, Roman and Ottoman ruins in which he played and helped his father, an architectural historian, dig. Perhaps growing up surrounded by so much ancient history makes it easier for Sasselov to accept the time-space continuum - the idea that the farther out he looks in space, the more history he sees.
"Not everything is about today and now," he says.
What is life?
As Prof Sasselov peers outward, Harvard Origins co-founder Jack Szostak looks in. The focus of Szostak's lab is to understand how life - which depends on self-replication and Darwinian evolution - emerges from chemistry. For decades, scientists have tried to understand the basics of life by taking existing life and trimming it back to its essence. But their experiments all failed.
In the past decade, origins researchers began to try building it from scratch.
Jack Szostak, a Nobel Prize-winning professor of genetics at Harvard Medical School, first showed how a simple membrane could form from clay available on the early Earth. More recently, he and others have been searching for a simple series of steps that can explain how primitive genetic material replicated itself.
If they succeed, "then, since we know there are probably hundreds of millions of Earth-like planets in our galaxy alone, it would make it seem pretty darn likely that there's life in other places out there," he says.
If lab experiments show that the process of turning chemistry into life is extremely complicated or unlikely to have happened, "then it would be possible that maybe life only started here. Maybe there's only life on Earth."
Prof Szostak and the other Origins researchers say they are nowhere near actually creating life, so they don't think their work poses any ethical concerns. Lawrence Krauss, a physicist who leads the Origins Project at Arizona State University, says trying to figure out how the universe came from nothing doesn't tread on religious ground, either - at least no more than Copernicus and Darwin did.
"Many people say it's a religious question, but I've been trying to say it's a scientific one," says Prof Krauss, whose book on the subject, A Universe from Nothing, is due out in January.
Origins work, like most other long-term "pure science" initiatives will invariably lead to innovations along the way that will help science - and perhaps life on this planet.
"Detecting alien life in the form of an HIV virus in the human patient is not much different than detecting alien life" on another planet, says Steven Benner, a distinguished fellow with the Foundation for Applied Molecular Evolution in Florida, which is searching for alien life forms on Saturn's moon Titan, as well as developing test kits for HIV and hepatitis.
Prof Sasselov says chemists transformed industry, medicine and daily life by mastering chemical synthesis and control. Now the Origins of Life work has the potential to allow biologists to synthesise and control the building blocks of life.
Those spin-off benefits, though, are not what motivate Origins research. "For sure it will spin out all sorts of unexpected technological benefits, which will make money for someone somewhere - but that's not why it's being done," says Prof Sutherland.
Instead of building the metaphorical buildings that most three-year scientific grants afford today, he says, the Origins researchers are constructing a cathedral. It may take them a century to find answers, but what they build will still be standing in a millennium.