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.No one today criticises SETI because there aren t any aliens.However, it is probably pointless to search the heavens for radiosignals from other worlds (as the SETI project does).It would beequally sensible to look for smoke signals.Radio did not exist on thisplanet a hundred years ago, and it will probably be obsolete a hundredyears from now.If the aliens are out there, and if they communicate atall, they probably do so using gravitons, squarks (supersymmetricpartners of quarks), telepathy, or the power of gptrp.And evenif they are using radio, they will have encoded their transmissions for329 WHAT DOES A MARTIAN LOOK LIKE?optimal efficiency.Lachmann s theorem shows that if so, their messageswill be indistinguishable from black-body radiation.(Imagine a SecondWorld War radio operator picking up one of today s encrypted satelliteTV channels.It would sound like static.) Is this the true meaning of thecosmic background radiation? Is it the buzz of an indecipherable,perfectly encoded, intergalactic mobile phone system? Vogonfone?In the SF and technothriller literature there is a persistent belief thata radio message can become an alien organism usually humanoid,female, and deadly.This scenario occurs, for instance, in Fred Hoyleand John Elliot s A For Andromeda and in the very silly movie Species.Fuel has been added to the flames by the metaphor of DNA as bothmessage and blueprint.The error here is the same as the mostfundamental of the errors in Jurassic Park.Namely, once you are inpossession of the DNA information needed to make a dinosaur, thenyou can make a dinosaur.Not so: we ve seen that one further vital itemof equipment is needed mother dinosaur.As with all information, anappropriate context is needed to access the raw information and turn itinto something with meaning.The binary information on a CD can beturned into Bach or Bon Jovi only with the aid of a CD player.You canstudy the sequence of 0 s and 1 s indefinitely, and not be able to tellwhether the CD is a recording of a string quartet, rock music, or themating cries of the howler monkey.The idea of information being something real is seductive.Itappeals especially to physicists of a fundamentalist turn of mind.JohnArchibald Wheeler s felicitous phrase It from Bit captures the attitude:things from information.In this view, which is an approach toquantum theory, the basic building-blocks of the universe are notmatter, not even quanta: they are information ( bits , binary digits), andthe rules of physics (laws of nature) turn the bits into its things.Theidea behind Wheeler s phrase is that the quantum state of any particle,or system of particles, is analogous to a binary choice between 0 and 1,or between some sequence of bits and some other sequence orsequences.Is this electron spinning in its up state or its down state? Theanswers to enough such questions determine the quantum state of theuniverse: now throw away the electrons and keep only the questionsand answers.Greg Bear made clever use of this idea in Anvil of Stars, whose330 HAVE ALIENS VISITED US?prequel The Forge of God ended with the total destruction of the Earth.The perpetrators of this outrage must be tracked down by a fewsurvivors, to wreak vengeance; it turns out that these destructive aliensare in possession of technology that can flip the bits of fundamentalparticles so that, for instance, one of the human characters, and hership, can be turned into antimatter, leading to a slow death as she isannihilated step by step by particles of ordinary matter in the not-so-perfect vacuum of space. It from Bit could be right.It is certainly a neat and original way toformulate quantum mechanics mathematically.However, it looks more like the standard physicists trick of reifyingmathematical concepts: taking ingredients from mathematicaldescriptions and interpreting them as real things.Examples includesuch basic concepts as energy, momentum, force, entropy.evenvelocity.And, of course, information.However, it is not clear that anyof these concepts is real.Not even velocity.In the real world, objectsmove, and their motion takes time.Mean velocity is a measure of howfar the object moves in a given period of time; velocity is an instantaneous version of this idea, the limiting value of mean velocityover a time interval that becomes as small as we please.No physicist hasever measured a true velocity, because there is a lower limit to the timeintervals that can be studied experimentally; therefore velocity is amathematical abstraction and may not correspond to any real thing.That doesn t stop the concept being useful indeed it is the mainreason why it is useful, because if velocity were a thing then we wouldn tneed the abstraction but it does stop it being physically real.Yes, theconcept has a sensible interpretation in the physical world, but it is notthe same as that interpretation.The same goes for energy, which is a unifying mathematicalconstruct.It was devised when mathematicians pursued Newton s lawsof motion and gravitation, and noticed that the rules become verysimple if a cunning trade-off between velocity and position in a forcefield was formalised into two quantities: kinetic energy , proportionalto the square of the velocity, and potential energy , the gradient of theforce field s landscape.This discovery led to a unifying concept, energy,defined to be the sum of kinetic and potential energy [ Pobierz całość w formacie PDF ] |
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