Where are all the extraterrestrials?

Ten areas in which science has work to do

1 No cure yet for cancerOne in four people get cancer, and it is the disease we dread most. Cancer biology is extremely complex and cures have been found for only a few types. More will eventually be developed, but meanwhile we must remember that stopping smoking would essentially eliminate lung cancer (20 per cent of total cancer incidence). Eating vegetables/ grains also reduces risk of cancer significantly.

2 Most of the universe is made up of mysterious dark energyThe universe has been expanding since its origin 14 billion years ago in the Big Bang. The rate of expansion increased noticeably about 6.5 billion years ago, impelled by a mysterious dark energy. This accelerating expansion was discovered in 1998. The nature of dark energy – which comprises about 70 per cent of the universe – remains a mystery.

3 One quarter of the universe is made up of mysterious invisible matterThere is far too little visible matter to account for certain well-established properties of the universe. Invisible matter must therefore be present. The nature of this "dark matter" is unknown, but it accounts for 25 per cent of the universe. So dark energy plus dark matter constitutes 95 per cent of the universe, while ordinary matter, the only kind we understand, makes up only 5 per cent!

4 We still do not know how life arose spontaneouslyScience proposes that life spontaneously arose on earth from lifeless molecules about 3.8 billion years ago. Research in the 1950s demonstrated a few elementary steps that might have been involved, but little progress has since been made in this area, which also has philosophical implications. Philosopher Antony Flew's pessimism that science will ever explain the spontaneous origin of life influenced his recent conversion from atheism to deism.

5 Climate change debate heats upFar from reaching resolution, this debate became more boisterous last month when a security breach at the Hadley Climate Research Unit in the UK released material that raises questions about the accuracy of some of the science underpinning the majority position. This position is that Earth is warming dangerously, with disastrous consequences looming, because of man-made greenhouse-gas emissions. The minority position holds that any warming is caused by natural variations beyond human control. The prediction of future climate is notoriously difficult, but we must be satisfied we are making the right decisions because the stakes are so high.

6 Human embryonic stem-cell research (HESCR) fails to deliver cures so farHESCR began in 1998, but embryonic cells are difficult to control and the issue is fraught with ethical problems. Big claims are made about the potential of HESCR to cure diseases but, to date, no cure has materialised and there is only one clinical trial in the pipeline. Treatments that might arise out of HESCR are five to 10 years away, while more than 70 treatments are established from ethically less fraught research on adult stem cells.

7 The human genome project (HGP) also fails to deliver curesThe HGP, which sequenced all human genetic information, was completed in 2003. One reason why this massively expensive project was completed so quickly was the promise that the resulting information would quickly lead to cures for diseases. However, the genomic search for genetic causes of major diseases has been disappointing. This is a complex area, with several genetic variations in each individual involved in causing common diseases such as cancer. Interaction between genes and environment is also important. Cures will come from HGP, but much more slowly than promised.

8 Theory of quantum gravity not yet formulatedPhysics is divided between two successful but contradictory theories: general relativity and quantum theory. General relativity describes the large-scale universe in terms of continuous space-time and quantum theory predicts behaviour on the atomic/subatomic scale, visualising a grainy world. A successful theory of quantum gravity would combine both theories and would explain the Big Bang and black holes.

9 The mind-body problem remainsScientists believe that the mind is simply what the brain does, and that eventually our understanding of brain biochemistry will explain our thoughts and even our free will. We are a long way from such an understanding. Progress will come in stages, but no milestone was achieved in this decade.

10 No contact yet with extraterrestrial intelligenceIt is likely that intelligent life exists elsewhere in the universe. For the past 25 years, Seti (Search for Extraterrestrial Intelligence) has been listening for radio transmissions from alien life. The extent of progress so far can be compared to sampling the ocean by taking out one glass of water. Contact with alien life would be the greatest historical event, but ET has not phoned yet.

William Reville is associate professor of biochemistry and public awareness of science officer at University College Cork; understandingscience.ucc.ie