IF you want to be taken seriously as a scientist, there are some things you simply don鈥檛 do. You don鈥檛 unveil a perpetual motion machine, you don鈥檛 announce that you have travelled through time. And you don鈥檛 even think about controlling the weather with energy beams.
For any scientist caught talking about such things, it usually destroys their chances of a top-flight career. But physicist Ben Eastlund isn鈥檛 hoping for a distinguished career-he鈥檚 got one already. As an expert on electromagnetism, he headed nuclear fusion research for the US Atomic Energy Commission during the early 1970s, acted as a consultant to many multinational companies, and made a personal fortune from a plasma processing technique widely used in industry. He now runs his own physics consultancy in San Diego, California, and in his spare time publishes cutting-edge research in top astrophysics journals. Oh, and he also studies weather modification.
鈥淚 don鈥檛 really have to do this,鈥� says Eastlund, almost apologetically. 鈥淏ut I do have a track record of developing workable solutions to difficult problems, and I hope this is one of them.鈥�
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The millions of people worldwide who live in fear of violent weather might hope so too. From thunderstorms to hurricanes, extreme weather kills thousands every year, and some experts believe the death rate will rise as global warming makes the climate ever more unstable.
In a typical year America is hit by over 1000 tornadoes. Spinning at 500 kilometres per hour, each tornado can kill dozens and inflict millions of dollars of damage. Last year tornadoes in the States broke all the records. More than 70 struck Oklahoma and Kansas in less than 24 hours last May, killing 46 people, injuring another 800 and wreaking over $700 million worth of damage.
But killer twisters may have met their match in Eastlund. And it鈥檚 a bit of a grudge match: his own home in Houston, Texas, has been hit twice by tornadoes. That made him eager to find out more about these meteorological monsters, and to come up with some way of taming them. His answer? Blast them with powerful beams of microwave radiation, generated by huge solar-powered satellite arrays orbiting the Earth.
It is, to say the least, a bold proposal-so bold that even Eastlund has had qualms about putting it forward. The idea came to him in the mid-1980s, when oil exploration company Atlantic Richfield asked him to come up with ways of exploiting a colossal natural gas reservoir in Alaska containing around 30 billion billion joules of energy. 鈥淭he company had originally planned to have a pipeline to take the gas from Alaska down to the US, but that had fallen through, so we looked at various other possibilities,鈥� explains Eastlund.
鈥淚 realised that Alaska was right on the line of sight for any ballistic missile attack from the Soviet Union. So I thought, why don鈥檛 we create a missile shield in the ionosphere using microwave antennas powered by natural gas generators?鈥� By firing microwaves at the ionosphere, explains Eastlund, you can generate a huge cloud of energetic electrons, corralled by the Earth鈥檚 magnetic field. As the ballistic missiles fell through this cloud, the electrons would set off the chemical explosives in the missiles, detonating their nuclear warheads before they could do any harm.
The US Department of Defense, in the midst of its first infatuation with Star Wars-style technology, took a keen interest in Eastlund鈥檚 idea. With its demand for a huge array of antennas 20 kilometres across, capable of zapping the ionosphere with a million megawatts of microwave power, it fitted right in with the spirit of the times.
Taming the beast
But Eastlund realised that such humongous power levels weren鈥檛 the sole preserve of Star Warriors: they are also typical of violent weather phenomena. Even a small thunderstorm packs around 7000 megawatts of power, while a major one-the kind of storm that can unleash a swarm of killer tornadoes-can be ten times more powerful still.
The figures got Eastlund thinking the unthinkable: instead of warding off nuclear attack, his technology might protect the US from more natural born killers. 鈥淲hile I worked on the antenna idea, patents were filed on everything that we might do with it,鈥� Eastlund recalls. 鈥淚 saw that with so much power, it might be possible to heat the edge of the jet stream of high-speed winds that passes right over Alaska, altering its direction. Any scientist that talks about weather modification tends to get laughed at, so I wanted to leave it out of the patents-but I was told to put it in.鈥�
Eastlund鈥檚 reluctance is certainly understandable, given the chequered history of past attempts at controlling the weather. In the 1940s and 1950s, many studies were carried out into the possibility of ending droughts by 鈥渟eeding鈥� clouds with 鈥渄ry ice鈥�-solid carbon dioxide-or particles of silver iodide. The idea was that water molecules would gather around these substances in sufficient quantities that they fell to the ground as sizeable droplets of rain.
Whether cloud seeding actually works is still controversial; the consensus seems to be that seeding does work-sometimes. Rather less certainty surrounds the outcome of perhaps the most audacious attempt at weather modification to date: the taming of a hurricane with just a few buckets of dry ice.
With its vast vortex of wind and rain releasing more energy in a single day than the US electricity grid delivers in a year, a hurricane would seem capable of shrugging off anything mere mortals could throw at it. But in the late 1940s, Nobel prizewinning chemist Irving Langmuir suggested that hurricanes might have an Achilles heel, the energy cycle that spawns them from the hot, humid air over the tropics. Langmuir proposed that only a small change in this energy cycle might be enough to make the whole hurricane unstable.
The butterfly effect
In 1947, he put his claim to the test, flying above a tropical storm and dumping around 100 kilograms of dry ice into it. When Langmuir analysed the evolution of the storm, he insisted that it had changed track after the dry ice had been dropped into it. Sceptics dismissed his claim as a mere coincidence, arguing that it is inconceivable that so little dry ice could have influenced something as vast and powerful as a hurricane. Yet similar experiments in the late 1960s suggested that you could weaken hurricanes significantly by using silver iodide to trigger rainfall at the expense of vicious winds.
Thirty years on, the notion of tiny influences having major effects no longer seems risible. Meteorologists have long since recognised the presence of strong 鈥渘on-linearities鈥� in weather phenomena, which allow-metaphorically at least-the mere flap of a butterfly鈥檚 wings in Kansas to trigger a typhoon over Japan.
It is this kind of reasoning that underpins Eastlund鈥檚 new proposal for weather modification: using microwaves to choke off killer tornadoes. Courtesy of those non-linear effects, Eastlund found he could make do with a lot less power to quash tornadoes than he had initially envisaged. This was just as well, since environmentalists were none too keen on the idea of a huge antenna in Alaska.
鈥淚 chose tornadoes as an initial area of severe storm research because they are in the low range of storm energy turnover,鈥� says Eastlund. What tornadoes lack in power they make up for in their complexity (快猫短视频, 15 May 1999, p 4). They typically begin inside violent thunderstorms in which warm, humid air punches upwards through a layer of chillier air above. The air cools as it rises, and the moisture starts to condense as rain or hail. Now cold and heavy with rain, this air then falls back down, and wraps itself up-partly under the influence of the Earth鈥檚 rotation-until it takes on the notorious twister shape.
The whole process of tornado creation must be quite precarious, says Eastlund, as you don鈥檛 always get tornadoes from storms powerful enough to spawn them. He came to suspect that the cold, rainy downdraft represents a crucial flow of energy, and if he was right, it would turn out to be the tornadoes鈥� Achilles heel. Hit that downdraft with a beam of microwaves, and the resulting heating might cut off the energy flow that allows a tornado to form.
But how on Earth could one pull off such a manoeuvre? By doing it from space, says Eastlund, with Solar Power Satellites. First suggested in the late 1960s, NASA looked at SPSs as a possible alternative energy source, and they鈥檝e gone in and out of fashion ever since. The basic idea is that a network of satellites equipped with vast solar panels, tens of kilometres across, collect the Sun鈥檚 light and convert it into microwaves for beaming down to receiving stations on Earth.
Tornado whacking
Eastlund suggests simply redirecting this energy beam. According to his calculations, even an SPS with relatively small solar panels-a few kilometres across, say-could produce a billion watts or so: easily enough to give a tornado a decent whack (see Diagram, p 28).
Predicting what the effects of such a huge whack might be is, however, far from easy because of all the non-linear effects involved, says Eastlund: 鈥淭he physics of these things is not something you can do on the back of an envelope.鈥� What he really needed was a decent mathematical model of the complex physics of tornadoes-plus a beefy supercomputer to run it on.
Eastlund found them both at the University of Oklahoma, whose Center for Analysis and Prediction of Storms (CAPS) runs one of the world鈥檚 most sophisticated simulations of violent weather on one of the world鈥檚 fastest computers: a Cray C90. Working with CAPS tornado modelling expert Ming Xue, Eastlund modified the simulation to take account of the heat generated by microwaves striking the cold, rain-laden downdraft that lies at the heart of tornado-spawning storms.
The results were extremely impressive: the simulation showed that a blast of microwaves from an SPS might indeed choke off tornado formation. 鈥淲e got rid of the cold, rainy downdraft,鈥� says Eastlund. 鈥淲e鈥檙e not sure why, though. It could be because the heat from the microwave beam slows the fall rate of the downdraft by providing buoyancy.鈥� In short, warm up the cold air and it won鈥檛 drop so quickly. Put enough heat in, and you might halt its descent altogether.
Watch out below
Whatever the explanation, the results of the simulation have given Eastlund enough confidence to present his ideas at a number of international conferences over the past 18 months, and he has also completed a technical paper summarising his proposals for the European Space Agency. He has in mind an array of orbiting SPSs. To spot the rain-laden downdrafts in thunderstorms their radar systems would need a resolution down to a few tens of metres. Each kilometre-sized SPS would then hit the downdraft with a tightly focused beam of microwaves with a frequency between 10 and 100 gigahertz-a frequency range absorbed by water vapour and raindrops-and pack a punch of about a billion watts.
The idea of so much power blasting its way down from the heavens sounds positively menacing. 鈥淚n fact, the power density would be around 1 watt per square centimetre, which isn鈥檛 all that different from what you get inside a microwave oven-though you wouldn鈥檛 want to stick your hand in it,鈥� says Eastlund. But his calculations suggest that anyone standing under the storm would be safe since water in the downdraft will absorb a significant proportion of the microwaves and anything reaching the ground will be too weak to be dangerous.
As for high-flying planes getting between the storm and the beam, the SPS radar would detect these and switch the beam off until the plane had passed. Unfortunately, you鈥檒l have to console yourself that birds are probably better off being fried than torn apart by the vortex of winds.
But these are all fine details on the much broader picture that Eastlund is sketching out. He stresses that he is not claiming to have solved every one of the technical or environmental problems that surround the proposal. 鈥淲hat I really hope I鈥檓 doing now is to put a new direction on the idea of weather modification,鈥� he says. 鈥淲e need to get it to the stage where the idea is no longer laughed at.鈥�
Which is pretty much where Eastlund is right now. Paul Bryant, a physicist with the US Federal Emergency Management Agency (FEMA) in Washington DC, says he finds Eastlund鈥檚 computer simulations pretty convincing: 鈥淚f you can heat the cold edge, it does end a tornado-that I鈥檓 comfortable with.鈥�
What Bryant is less comfortable with is whether a satellite high above the Earth can be trusted to deliver such a powerful beam of microwaves only where it鈥檚 needed. 鈥淧eople are 70 to 80 per cent water, and if you鈥檙e going to do this from orbit, that could be a problem,鈥� says Bryant. 鈥淵ou need a good idea of where the tornado will go, and be able to control the beam so that it doesn鈥檛 hurt people. If you have it ground-based instead, you need a lot more microwave stations, and it becomes a lot more expensive.鈥�
None of these proves the whole idea is doomed, says Bryant-only that there鈥檚 a lot to be sorted out before anyone should think of turning those simulations into a prototype tornado tamer. 鈥淲ith appropriate research funding, it could be done,鈥� he says. Eastlund recognises the need to pay careful attention to the safety aspects, and emphasised this in a paper presented at a joint NASA/FEMA conference in January 1999.
But Terence Meaden of the British-based Tornado and Storm Research Organisation (TORRO), has a more basic problem with Eastlund鈥檚 proposal. 鈥淗ow would he know if his ideas work?鈥� he asks.
It is a deceptively simple question that has dogged the whole notion of weather modification from the outset. You have this great idea about ending droughts, say, or clearing fog or taming tornadoes. So you try it out-and sure enough the rains pour, or the fog vanishes or the tornadoes fail to materialise. But how can you be sure that the success isn鈥檛 mere coincidence? Or in the jargon of science, where鈥檚 your control?
To get around Meaden鈥檚 conundrum you could use computer simulations so sophisticated that they predict accurately what would have happened if the experiment hadn鈥檛 taken place. But Eastlund concedes that when it comes to predicting the exact form and ferocity of tornadoes, not even CAPS and its Cray C90 are up to the job-yet. 鈥淚 wouldn鈥檛 say right now if we could tell whether we had made things worse or better or what,鈥� he says. 鈥淭hat鈥檚 one of the things I鈥檓 looking for funding for.鈥�
Eastlund鈥檚 real achievement so far has been to focus attention on a big loophole in the standard put-down to the idea of weather modification. Sure, tornadoes and the like unleash colossal power via non-linear processes of daunting complexity. Yet, as Eastlund has shown, that very complexity could hold the key to weather modification-for non-linear processes can be transformed by a well-aimed whack.
Whether his plans for a space-based whack will make it off the drawing board remains to be seen. 鈥淎t the moment, I鈥檓 just trying to appeal to those with really good simulation code, so we can get a better understanding of the processes involved,鈥� says Eastlund. 鈥淭hat, and trying to get the National Science Foundation to reply to my e-mails.鈥�