OUR love affair with Einstein is over. This time last year, we were celebrating his legacy as part of World Year of Physics. We couldn鈥檛 get enough of black holes, gravity and space-time. Less than two months later, NASA announced that it was postponing most of its 鈥淏eyond Einstein鈥� cosmology programmes to help pay for space shuttle flights. It is a decision that could have devastating consequences for our understanding of the cosmos.
NASA鈥檚 decision to divert $3.1 billion from its science programme marks a spectacular U-turn. Only last September the agency鈥檚 chief, Mike Griffin, vowed not to take 鈥渙ne thin dime鈥� from the science budget to pay for human space flight. Now NASA is aiming for 16 shuttle flights to complete the construction of the International Space Station, and one to service the Hubble Space Telescope. Aside from Hubble, the benefits to science will be next to nothing.
That is in stark contrast to Beyond Einstein, a series of missions designed to answer the most pressing questions in cosmology. What powered the big bang? What happens at the edge of a black hole? And just what is this dark energy that is speeding up the expansion of the universe? Central to the programme are two missions: a flotilla of four X-ray telescopes known as Constellation X and the LISA gravitational wave observatory.
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This month, the two missions have gone from hero to zero. NASA had called them flagship missions, while the US National Academy of Sciences recommended them in its decadal review of astronomy in 2001. Now the missions are 鈥渄eferred indefinitely鈥�, according to the latest budget request.
NASA is asking Congress for $135 million less for the Beyond Einstein programme (over a period of seven years) than it did last year. Unless NASA reverses this trend, there will only be enough money for one of the flagship missions. Constellation X and LISA will have to slug it out with each other, and may miss out altogether.
Gravitational wave research has the most to lose because it probes the cosmos in a fundamentally new way. We have learned huge amounts about the universe by studying electromagnetic radiation at every wavelength from gamma rays to radio waves, yet more than 95 per cent of the universe is invisible to our telescopes. Black holes, cold stars and dark energy emit no light. Imagine what we might discover if we could study the vibrations stirred up by the universe鈥檚 heaviest and fastest-moving objects.
鈥淚magine what we鈥檇 discover from a study of the universe鈥檚 heaviest and fastest objects鈥�
While Einstein鈥檚 general relativity predicts gravitational waves, which alternately stretch and squeeze space-time, no one has detected them directly. Hardly surprising when you realise what the job involves. A gravitational wave sparked off by the implosion of a star in a supernova is thought to stretch space-time by an amount less than 100,000 times the size of an atomic nucleus. To try to detect this vibration, researchers have already built giant L-shaped detectors, the largest of which are the twin 4-kilometre-long LIGO experiments in Washington state and Louisiana.
There are no guarantees that LIGO will spot anything. Even so, there are good reasons for moving the search into space with the LISA observatory. For a start, the sensitivity of any detector improves with size. LISA is certainly large: its three spacecraft will orbit the sun 5 million kilometres apart. And out in space they will escape the background shudder of Earth鈥檚 gravity. So LISA should be able to detect waves from sources that are known to exist.
Beyond Einstein is not the only project to lose out in NASA鈥檚 2007 budget request to Congress. Other casualties include missions to detect and study Earth-like planets (see 鈥淶oom with a view鈥�) and to bring rocks back from Mars. Astrobiology has taken a huge hit too, prompting planetary scientists and astrobiologists to start mobilising their supporters to sign petitions and write to Congress. And rightly so.
Experience shows that direct action works. When NASA announced in 2004 that it was axing a mission to repair the Hubble space telescope, there was an outcry. Amateur astronomers petitioned both houses of Congress, newspapers ran editorials about Hubble, and the US National Academies publicly criticised NASA鈥檚 decision. The agency reversed its stance: this year鈥檚 budget includes money to send astronauts to Hubble, pending the space shuttle鈥檚 return to flight. The Gravity Probe B mission too was saved at least seven times from cancellation by intense political lobbying.
So far there is little sign of action from cosmologists about LISA. This is worrying. With no one shouting for LISA, there is a danger that NASA鈥檚 funding will slip further, along with the planned launch date in 2014. And while the European Space Agency could pick up the $1 billion tab for LISA, there is no certainty that it will.
The good news is that NASA鈥檚 budget request to Congress is just that 鈥� a request. There is much political manoeuvring to be done before it is finalised. Gravitational wave researchers still have time to win the hearts and minds of people. But they had better be quick.
