Seven scientists are plunging to earth in an overloaded hot air balloon. Six of them must jump out if the balloon is to be light enough for just one to float to safety. But who should be the lucky survivor? This week our great balloon debate kicks off. Over the next four weeks young academics will argue why theirs is the most vital discipline. Next week the social sciences battle it out. The week after it is the humanities' turn.

But which discipline should be allowed to survive? It is up to you. Vote this week for the most important science. Over the next two weeks you can select from the social sciences and the humanities. The survivor from each week (determined by your votes) will go on to argue for his or her entire faculty in the fourth week. That will be our final debate and will appear in the Research Opportunities supplement on February 23. You can vote in three ways: on the Internet, newsint.co.uk. By email, on balloon@thes.co.uk or by fax on 0171 782 3300. Vote for one discipline and add comments if you wish. The science ballot closes on February 8.

PARTICLE PHYSICS The search for knowledge, understanding and truth is a driving human need, intrinsic to our nature and essential for a healthy, vibrant society. What could be more fundamental than probing the very heart of what we see around us? Indeed the ability to attribute the complexity of our universe to a limited number of elementary particles governed by a few fundamental forces, is one of the most significant breakthroughs in knowledge of this century.

Who has not gazed up at the cosmos in wonder? Man is inextricably drawn to the mystery of space. How did the stars and the galaxy form?

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Research in particle physics and astronomy seeks to answer these and further questions, as basic as the origins of mass - yours, mine, the galaxies' - and how the universe came into being. As a physics undergraduate I was intrigued and troubled to hear that most (more than 90 per cent) of the matter in our universe is of unknown form. So when we look at the stars we are seeing but a tiny fraction of what is there; furthermore it is likely that much of this "dark matter" is a different "stuff" to anything we find on earth.

Of course, high energy physics has practical spin-offs, from television to the applications of quantum mechanics. But no other science can match the sheer excitement of our work. Use your imagination and vote for our pure search to understand our origins and the cosmos.

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Gavin Davies, Imperial College London

PHYSICS No one can say that all the paradigm-shifting scientific discoveries have been made. If there are more to come then they will come from physics.

As the great physicist Isaac Newton observed: "To explain all nature is too difficult a task for any one man or even for any one age." We must continue with physics because we simply cannot foretell what practical and cultural developments will spring from the Bose-Einstein condensation, only discovered last November, and the exploration of the nanoworld.

Physics is unique in being able to both support our technological infrastructure and enrich our cultural heritage. Other sciences may lay claim to one but none can lay claim to both. Consider, for example, the law of gravitation: it underpins remote surveying, vital for learning about the earth, communication by satellite and geophysical prospecting. But it also underpins the great adventure embodied in the exploration of our solar system.

If your priority is improved health, consider this: physics is taking over as the science behind medical advances: medical physics has provided us with imaging techniques and scanning devices such as x-ray machines and NMR scanners. In place of the surgeon you will increasingly see the radiologist, mending your organs using little machines that crawl through your blood vessels, monitored by these high-tech imaging techniques. The surgeon's scalpel will disappear in favour of the laser. As for the other sciences, if you vote for molecular biology you must stomach awkward questions about genetic manipulation and animal experimentation; and if you vote for engineering or chemistry you are really voting for physics because physics is their basis.

Mark Watson, Coventry University and Julia Davies, Cambridge University ECOBIOLOGY As we approach the third millennium the human race is engaging in the ultimate balloon debate. Which parts of our ecological life-support system can we afford to lose? Increasingly fragmented ecosystems, exponentially rising human demands and global climate change are threatening habitable limits for life. Understanding how the animals and plants of our ecosystems are put together and how they recycle our air, water and nutrients are the critical questions we must answer. Our future wealth, welfare, and ultimately our survival, is dependent on the living organisms with which we share this planet.

Biological diversity not only provides essential ecosystem services, each species is a potential resource for mankind. The source of food plants, domestic animals, clothing, building materials, energy, control agents for pests and medicinal resources. Biodiversity is essentially a planetary tool kit, the product of a 3.5 billion year experiment in design and adaptation. This kind of large-scale ecological biology tells us how these tools function, what we can use them for and how we might best preserve them.

Given that the costs are tiny but the stakes high, can we afford to let ecological biology be anything less than top priority? It is vital that we secure the integrity of our local and global ecosystems. Improvements in technology alone will not achieve these ends. At the heart of ecology lies the survival of the ultimate vehicle, planet earth, which must carry us all into the next century.

Natasha Loder, Natural History Museum and University of Sheffield ENGINEERING Listen to the others in this balloon, all trying to show that their disciplines produce the most useful scientific discoveries. In fact, none of their discoveries will ever be useful - unless the engineers step in and turn them into something that can benefit society.

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Just remember two things. First, there are piles of scientific discoveries waiting for someone to come along and apply them: at the moment this country needs appliers rather than discoverers. Second, engineering is the harnessing of natural resources: we regularly solve society's problems directly, without needing recourse to these scientific middlemen. You can only vote for one of us - and engineering is the only discipline that could help humanity on its own.

Engineering is directly responsible for health and for wealth generation. Engineering is the road that all sciences must take on the journey to a final product. A world without engineers would be dark, cold and hungry. If you value the light that guides us, the heat that warms us, the food that sustains us or the houses that shelter us, you must vote for engineers. Look up! Look around you! Almost every man-made item you see has been designed by engineers.

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The future will be rosy once the engineers have applied that backlog of discoveries. If you still have any unease about voting for me, remember this: no scientists here could even begin to do their research without an engineer to build their equipment.

Mark Volanthen, Southampton University

CHEMISTRY is the central science. If you disagree with this, you disagree with the consensus of experts in the European Union and in the United Kingdom's Technology Foresight Programme. The EU targets 14 technology programmes for science funding: nine directly involve chemistry. The UK Technology Foresight Programme, which has examined the areas of research most important to the country, has six priority areas: four can be serviced by chemists (the remaining two concern managing new technology).

Chemistry (including pharmaceuticals) is the UK's most successful industrial activity. It makes more than Pounds 4 billion every year.

Vote with the experts, who are ensuring that scarce research funds are being directed to support chemistry. This is recognition that the future of science requires that chemistry, the central science, survives.

The loss of any science department is a tragedy; the retention of chemistry departments is a necessity. This is because it protects and nurtures knowledge in a myriad of other fields.

The universe is almost entirely composed of atoms and molecules. Understanding much of science, including all natural systems, depends upon understanding chemical processes. And understanding these processes holds the key to solving the most pressing problems facing our planet. If you are concerned that we develop alternative energy sources, control and reduce pollution and improve population health with new vaccines and drugs, you must vote for chemistry.

Tim Oldham, Imperial College

MOLECULAR BIOLOGY If we want to make an impact on childhood deaths in the west, half of which are caused by mutations in DNA, then we must support genetics.

Only genetics can get us to the root cause of such diseases and so bring improved and rational treatments. For those of us who make it through to middle and old age our genes influence what we are most likely to die from - be it cancer, heart disease, stroke or dementia.

Let us get back to basics, and as far as the planet's biology is concerned DNA is the basics. Using molecular biology to study variations in DNA means we can identify the very molecules that control how we all develop from single cells to complex multicellular animals. Our genes encode the proteins that tell our cells to grow and divide - or to die, and they encode the antibodies that give us immunity from infectious disease. Genes encode proteins that are involved in forming memory, turn light into vision, and even predispose people to aggression or a desire to seek out thrills in life.

Your DNA is both your making and, often, your undoing - it may even influence whether, when you vote, you are short-sighted or blessed with good judgement.

Wendy Bickmore, MRCHuman Genetics Unit, Edinburgh

MAÉ«ºÐÖ±²¥MATICS is fundamental to science. Indeed, the "scientific method" arguably has its origins with the Greek mathematicians such as Euclid and Pythagoras. Since then mathematics has become ever more important to science. The great theories in physics and cosmology are mathematical, for example the theories of Einstein and Feynman, the major physicists of the 20th century - or those of the cosmologists Hubble and Hawking.

If mathematics were to disappear then science would too, because science cannot function without it. Mathematics is the life-blood of computer science, for example. And the geneticists who are, perhaps foolishly, rearranging the human genome, would be lost without mathematics for analysing their data.

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Mathematics on the other hand could continue successfully without the other sciences, not just as a complete self-supporting science but because increasing use of mathematics is being made in the humanities and social sciences. Finally, do not forget that mathematicians can operate on a fraction of the budget required by the other sciences. In this harsh economic climate, financial considerations cannot be ignored. Mathematics is essentially cerebral and does not need the expensive equipment that other sciences need.

Tony Humphries, Sussex University