Normally I prefer to write about scientific ideas likely to have practical effects on the world in a generation or less. After all, as John Maynard Keynes remarked, "In the long run we are all dead," and a hundred years from now you and I will probably have little interest in science or anything else.

Today I am going to break my usual rule, and describe a development whose impact is likely to be a long way in the future. Let me defer the definition of "a long way." And let me begin a fair distance into the past, in 1924, when a young Bengali physicist named Satyendra Nath Bose sent a letter to Albert Einstein. With the letter was a paper, written in English, that had already been rejected by a professional journal. Bose asked Einstein if the work was any good. Einstein not only thought the work was good, he personally translated the paper into German and arranged for its publication. Then Einstein took the ideas of the paper a step further, and in 1925 suggested the possibility of a strange new state of matter.

The conventional states of matter at the time were solid, liquid, and gas, though a few people were already considering plasmas, which occur at temperatures so high that gas atoms will shed electrons. However, what Einstein predicted would occur not at high temperatures, but rather at very low ones. Cool a gas sufficiently, he said, and it will "condense" to its lowest possible energy level. The atoms in the condensed gas will become indistinguishable, both in practice and in principle. In fact, there will be no separate atoms, just one big one. That conceptual super-atom came to be known as a "Bose-Einstein Condensate."

I describe it as a "conceptual" super-atom because the temperature at which a Bose-Einstein Condensate might form could be calculated, and that temperature was far lower than either nature provided or humans could achieve. There is a least possible temperature, known as absolute zero. Temperatures above that lowest value are measured in Kelvins; so, for example, water freezes at 273 Kelvins and boils at 373 Kelvins. Dry ice, which is solid carbon dioxide and cold enough to "burn" you if you touch it, forms at 195 Kelvins. Helium, which remains as a gas to a lower temperature than anything else, turns to liquid at 4.2 Kelvins. Helium, after many years of effort, had finally been liquefied in 1908, but this was - and is - regarded as astonishingly cold. The temperature of the cosmic background radiation, which is the temperature of "empty" space, is 2.7 Kelvins and not much colder than liquid helium. However, it was predicted that before a Bose-Einstein Condensate could form, the temperature would have to be less than one one-millionth of a Kelvin.

That looked like the end of the story. What Einstein, building on Bose's work, had predicted seemed like an interesting piece of theory, but one that could never become reality. The necessary temperatures were impossibly low.

Scientists, however, are a persistent breed. Over the decades, people chipped away at the problem of achieving lower and lower temperatures. In the 1990s an ingenious combination of methods was devised, using lasers to rob atoms of their kinetic energy, then holding them in a magnetic trap that allowed the more energetic atoms to "boil off" and leave the colder ones behind. Using these techniques, a group in Boulder, Colorado, was finally able in 1995 to do what had for so long been regarded as impossible. They cooled a gas of 2,000 atoms of rubidium (normally a metallic element) to less than a hundred billionths of a degree above absolute zero. The rubidium gas formed the first example of a Bose-Einstein Condensate (now usually shortened simply to BEC).

Other groups soon had similar success, and with larger numbers of atoms. A ten million atom BEC was produced using a gas of sodium atoms, and another with a gas of lithium atoms. In 1998, a BEC was produced using a gas of hydrogen atoms, which was the substance with which the advanced cooling methods were first developed. Now dozens of groups are producing Bose-Einstein Condensates, and routinely they involve millions of atoms. Just last month, a French team produced the first BEC using gaseous helium.

What comes next? In the near-term, meaning the next ten to twenty years, I anticipate nothing better than more experiments, developing BECs of larger and larger sizes and simply studying their properties. However, it was a poet, not a scientist, who provided what I regard as the correct long-term framework for thinking about BECs. Tennyson wrote about "the fairy tales of science and the long result of time." During the twentieth century, time (plus effort) has again and again turned apparently abstract theories of science into the technology that transforms everyday life. I think that eventually Bose-Einstein Condensates, which represent an entirely new state of matter, will have scores or hundreds of practical uses.

In order to say how long this may take, my strongest argument has to be by analogy. The theory behind the laser was produced in 1917 (again in a paper by Einstein). It took until 1960 - 43 years later - to produce the first working laser turning that theory into practice. And it took almost the same length of time to give us today's flood of practical uses, with lasers employed in everything from eye surgery to micro-electronics to CD players to the production of the Bose-Einstein Condensates themselves. The laser and the BEC have deep conceptual similarities. They are both cooperative phenomena. The atoms that make up a BEC, like the photons that make up a laser beam, move and act in exact coordination with each other.

Let us take the similarity between lasers and BECs one step farther, and say that, like the laser, the time from the theoretical prediction of the Bose-Einstein Condensate to its first demonstration will be about the same as the time from that first example to a flood of practical uses. Then the arithmetic would say, prediction of BEC to real-world example, seventy years (1925 to 1995). Another seventy years from first example to a host of uses predicts that Bose-Einstein Condensates will be a common part of the industrial scene by 2065.

This prediction is probably on the conservative side. The rate of technological progress has steadily increased over the past half century, and it is still increasing today. BECs will probably be playing vital technological roles - don't ask me what - by 2050.

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