By Jo Twist
BBC News science and technology reporter
Science and technology have powered huge leaps in understanding but our biggest challenges lie ahead.
Life on Earth has billions of years left before the Sun goes dim
The science of complexity is perhaps the greatest challenge of all, English Astronomer Royal Sir Martin Rees believes.
The biggest conundrum is humanity and how we came to be, he told the Technology, Entertainment and Design (TED) conference in Oxford.
The cosmologist said that in the 21st Century science had changed the world faster than ever before and in many new ways.
"Our century is very, very special," said Professor Rees. "It is the first where humans can change themselves."
Advances such as drug implants may have changed human beings profoundly already - the effects of which we could see this century.
We know more about our Universe, we know how stars are fuelled, how nuclei in atoms act together, and how galaxies are held together by dark matter - huge swarms of particles.
We could trace events back to the early stages of the Big Bang, but we still did not know what "banged", or even if there were multiple "bangs", explained Professor Rees.
There was still a lot of "unfinished business" for humans, he said, particularly in understanding the theory that links the very large and the very small in our Universe - the theory that may lead to understand potentially different dimensions.
Quarter of a second in June
Professor Rees also had warnings for conference participants.
"Bio and cyber technologies are environmentally benign as they offer marvellous prospects, but they will have a dark side," he said.
"One technology may empower just one fanatic to trigger a global catastrophe. We have to accept the risks if we are going to enjoy the benefits of science," he said.
Professor Rees called on scientists and entrepreneurs to take on the responsibility to campaign and alert the rest of the world to both the risks and benefits. Earth, after all, has a long history ahead.
Even those in the field of evolutionary sciences are far from knowing how humanity will change.
Computer models can only go so far when we do not even fully understand how we came about on Earth in the first instance.
We have only existed, as far as we know, for a few billion years.
"If you represent the Earth's lifetime in a single year, the 21st Century would be a quarter of a second in June," said Professor Rees.
We are not even halfway through our allotted time on Earth before the Sun itself burns out.
"Any life and intelligence that exists then will be as different from us as we are to bacteria," he explained.
Our rate of population growth and our addiction to fossil fuels and consumption of resources only adds to the uncertainty about our future.
Life - but not as we know it
One man who is set on trying to unfold the complexity of life, and how we are made up and came to be in order to understand our future, is Craig Venter.
He led the private effort to sequence the human genome - the genetic code that creates life.
His next big challenge is to create living, artificial organisms from a kit of genes, and says he is well on his way. He believes an artificial single cell organism is possible in two years.
"We sequenced 130 genomes this year. The rate of reading the genetic code has changed but we have barely scratched the surface," he told the conference.
Microbes make up over a half of all Earth's biomass. A mouthful of seawater accidentally swallowed sends millions of different bacteria into your gut.
To unravel the complexity of life on our planet in order to understand more about where humans come from, Dr Venter embarked on a round the world ocean voyage to take samples of seawater every 200 miles.
At every stop he found new species. At one location, one barrelful contained 1.3 million new genes and 50,000 new species, he said.
To Dr Venter, these genes are the design components of evolution, the "software that builds its own hardware".
But evolution has only given us so many answers. "We need new methods to understand the biology out there. Only by trying to build it will we truly understand it," he says.
The building blocks of life could help create new life forms
But the aims of his mission are even wider than that.
"We are optimistic we will have a new form of artificial life based on our knowledge of these existing genomes that provides knowledge to go forward to tackle environmental problems," he says.
"We know lots of different pathways and thousands of organisms that live off carbon dioxide and can catch that back from the atmosphere."
The captured carbon can then be converted to biopolymers and other new products, he believes.
There are lots of pathways that can be engineered to convert methane into useful products, too.
Future engineered species could be a source of food, energy, and could help regenerate damaged environments. To Dr Venter, his venture is crucial to understanding our future.
He dismisses fears that if one can create artificial life once the code has been written, then this will open a "Pandora's Box" for those who want to play God or take us to an era of bioterror.
"Almost every major religion requires humans to try to improve society," he says.
One certainty in an uncertain world is clear to Professor Rees: "Whatever happens in this uniquely crucial century will resonate in the remote future and perhaps far beyond the Earth."