Extraterrestrial Civilizations - Isaac Asimov [115]
Besides, we have no idea how it would be possible to convert matter into photons and then back into matter in such a way as to reproduce all the characteristics of the original matter to the finest details. (Just imagine reproducing a human brain in all its intricacy after it had been dissolved into photons. Some might consider it conceivable, but even those who do can give no hint of the actual method for doing it.)
Then, too, the conversions in either direction would have to be done with very tight simultaneity, for if some conversions into photons are made even a second later than others the photons will be spread out over hundreds of thousands of kilometers, and it might well then be impossible to reconvert them into compact objects.
How might the photons, even if produced in tight simultaneity, be directed in the proper direction, kept from losing order in the long voyage, and then reconverted with equally tight simultaneity?
Granted that 200 years ago the feats of modern-day television might have seemed just as impossible and out of the question, we cannot safely argue that because some things that were thought fantastically impossible have proved possible after all, all things that seem fantastically impossible will be proved possible.
In this book, I have taken the conservative route at all times and accepted nothing without at least some evidence, however slight and tenuous. At the present moment, there is no reason to suspect that a photonic drive can be made practical, and until some evidence to the contrary arrives (and that could be tomorrow, of course) I must say that while I cannot positively rule out a photonic drive, I consider its chances so close to zero that we may reasonably call it that.
Could we avoid the difficulty of conversion and reconversion, and of directing the light beam, by leaving all the particles as particles but somehow removing their mass? A massless ship-and-contents would instantly accelerate to the speed of light and remain at that speed. Once the mass was restored, it would instantly change to its original speed. That seems a much more comfortable situation than conversion into a beam of photons.
Unfortunately, we know of no way of removing mass from any particle, nor is there any indication anywhere that we will ever find a way. And if we did, we would still be traveling only at the speed of light.
So far, all I have suggested brings us to the speed of light, but doesn’t pass us beyond it.
In 1962, however, the physicists O. M. P. Bilaniuk, V. K. Deshpande, and E. C. G. Sudershan pointed out that Einstein’s equations would allow the existence of objects with mass that is expressed by what mathematicians call an imaginary quantity.
Such objects with “imaginary mass” must always go at speeds faster than that of light if Einstein’s equations are to remain valid. For that reason, the American physicist Gerald Feinberg (1933–) named them tachyons from a Greek word meaning fast.
An object with imaginary mass would have properties quite different from ordinary mass. For one thing, tachyons have more energy the slower they are. If you push a tachyon and thus add energy to it, it goes more and more slowly, until with an infinitely strong push you can make it go as slowly