杏吧原创

The pursuit of a deeper truth, a fundamental theory that underlies all others, is a powerful motivator in physics. But it鈥檚 not the only one. Equally valid are curiosity and awe at the richness of nature 鈥� at the way seemingly unrelated processes can produce order, beauty and diversity from chaos.

The first motivation is evident in high-energy physics, where the idea of finding a 鈥渢heory of everything鈥� occupies many talented theoreticians. The second is found in fields such as evolutionary biology and astronomy. Until recently the two approaches hardly interacted, but now the discovery of dark energy is creating a marriage of convenience between high-energy physicists and observational astronomers. As with any such marriage, this one presents dangers as well as opportunities.

Dark energy, which seems to be driving the accelerated expansion of the universe, is an area of fundamental theoretical interest for high-energy physicists. To explore it experimentally will require precise measurements of the universe鈥檚 expansion history and the growth of cosmic structure. This requires observational data from large samples of galaxies and supernovae, and astronomers are working with high-energy theorists to design suitable surveys.

The trouble is that physics and astronomy make progress in very different ways. In physics, controlled experiments rule, but astronomers observe whatever nature shows them. I fear that blindly applying physics-style experimental design to astronomical projects risks costly failure, as well as undermining the methodological basis of astronomy and its attractiveness to young scientists and the public.

Astronomical instruments traditionally promote a diversity of uses. The is a classic example of how a new observatory can push the boundaries of what we can observe by extending sensitivity, wavelength coverage or resolution. Hubble has been employed across the astronomical community. The same cannot, however, be said for the (WMAP), which has mapped the radiation left over from the big bang. Like a traditional physics experiment, it was designed and successfully operated by a tight-knit group of scientists to tackle a specific task. Its high-impact results have encouraged many to hope for similar success from dark energy surveys.

This courts disaster. First, it is not possible to predict how accurate such a survey would be, as it depends on factors we are uncertain of, such as the nature of supernovae when the universe was half its present age. If we鈥檙e unlucky it might only marginally improve our understanding of dark energy. The money will have been wasted; astronomers will be blamed.

Even if such projects do help us to understand dark energy, they won鈥檛 advance other areas of astronomy, so putting too much emphasis on them may slow our field鈥檚 development. New observatories enable the discoveries and insights that power astronomy. Supporting dark energy surveys may delay observatories at X-ray, radio, ultraviolet or infrared wavelengths.

Finally, such a shift of focus would run counter to the underlying culture of astronomy. If we move towards large, long-term projects of the kind now dominating high-energy physics, work will be done in big teams and focus on technical tasks such as ensuring data quality. The best young scientists will see little chance of making their mark and may go elsewhere. Prioritising one 鈥渇undamental鈥� question rather than the traditional diversity of issues will also make astronomy less appealing to the general public, undermining taxpayers鈥� support for the expensive facilities we need to pursue our science.

We need to apply a hard-nosed cost-benefit analysis to dark energy projects. We must recognise the cultural differences between high-energy physics and astronomy, and be willing to argue that astronomical discoveries 鈥� that the universe expands, chemical elements were built in stars, black holes exist, planets orbit other stars 鈥� are no less significant for humanity than clarifying the underlying nature of forces and particles.

Any large new astronomical project should be designed to push back frontiers in several areas of astronomy. For example, supernova surveys to trace the expansion history of the universe should also store enough information to explore the mechanism by which supernovae work. And we should ensure opportunities for young scientists by promoting a diverse set of science goals and unambiguously assigning credit to those responsible for the main scientific insights.

If we don鈥檛 do these things, we may lose both the creative brains and the instruments that our field needs to remain vibrant. Dark energy is a Pied Piper, luring astronomers away from their home territory to follow high-energy physicists down the path to professional extinction.

鈥淒ark energy is luring astronomers down the path to professional extinction鈥�