Friday, April 22, 2011

S is for ... Shapiro Effect

Before I start in on the Shapiro effect, I want to talk about the origin of the Universe.

This could take a while. I hope you packed a thermos.

Actually, the concept of the thermos flask relates to current theories on the origin of the universe, in this way: both are the result of research into thermodynamics, the branch of physics that deals with energy and work. You may recall that the laws of thermodynamics were invoked, post facto, to discredit Orffyreus' perpetual-motion machine. They state, pretty clearly, that that sort of steady state is impossible in nature. The energy in a closed system is constant; but no machine can possibly be a closed system. Its energy comes from outside itself - even if only in the sense that it is manufactured, and so its component materials pre-exist its functioning self (existence precedes essence, in this case at least; the philosophical implications of that assertion, and its contrapositive, are beyond the scope of this blog, however). In general, any two systems in proximity to one another will undergo a heat exchange, until they reach a thermal equilibrium: an example of this can be seen if you leave a cup of hot coffee and a glass of iced tea out in the environment. After a sufficient period of time, the coffee and the tea will be the same temperature as one another: approximately the temperature of the ambient air around them.

Heat exchange occurs via three spontaneous processes: conduction, which is the transfer of heat down a heat gradient through matter, as when putting one end of a metal bar in a fire causes the whole bar to become hotter; convection, which is the transfer of heat within fluids along so-called convection currents, as evidenced by oceanic currents of warm water circulating from the Equator to the Poles; and radiation, which is the transfer of heat energy in the form of electromagnetic waves, as when the heat from the Sun warms the Earth. The Second Law of Thermodynamics reflects, without particularly explaining, an important aspect of this spontaneous heat exchange: it always travels down a heat gradient, so that hotter things spontaneously become cooler over time - in thermodynamic terms, the entropy of the system increases. Viewing the Universe as a vast closed system, within which the Earth is a smaller system, and a single human being a still smaller system within that, the implication of the Second Law of Thermodynamics is that all things eventually fail and die; their energies are lost to the vastness of empty space, and ultimately the Universe succumbs to "heat death." Draw comfort from the fact that we are likely to be struck by devastating asteroids long before that dreadful moment arrives.

Thermodynamics, therefore, has important consequences for our understanding of Time, and in particular its monodirectional linearity from Past, to Present, to Future. Thermodynamics frames this subjective appreciation of the passing of time as a function of increasing entropy in the systems we observe. Of course, if Orffyreus was able to produce his perpetual motion machine for real - he smashed it when Willem 's-Gravesande, a supporter as it happened, tried to examine it to determine if this were so, so we'll never know now (at least not within a monodirectional linear time paradigm) - that has even more important consequences for thermodynamics, but I'm getting ahead of myself.

A thermos flask maintains the temperature of its contents much longer than usual by interposing a vacuum between them and the system containing the flask. Invented by James Dewar - the original patent was for a "Dewar bottle" - it thereby reduces heat loss via conduction or convection, since the fluid in the flask is insulated from the atmosphere around the flask by a vacuum that contains no matter and so has nothing to flow. Radiation can cross a vacuum, but a thermos flask has a highly reflective interior surface that reduces this. In practice, only the inconvenient fact that you have to be able to open the flask to introduce something into it, or indeed to drink something out of it, allows for any heat loss. Perhaps if the Dewar bottle were a Klein bottle, things might be different...

How does any of this relate to the origin of the Universe? Well, since the Universe hasn't already succumbed to heat death, and since we observe Time passing in accordance with thermodynamic predictions, we can conclude that the Universe isn't infinitely old; it exists within a finite Time (although there's a hidden petitio principii there). It had a Beginning; it will have an End. The prevailing cosmological view is that, something like thirteen billion years ago or so, all the matter and energy in the Universe today was condensed into a singularity, a dimensionless point that was tremendously potent and that exploded - the so-called Big Bang - in order to bring the Universe into being. Scientists are very sketchy about what prompted this Big Bang, and about what preceded it (not least because our notions of causality and linear time really hinge on the acceptance of the Big Bang theory and aren't applicable to anything that pre-existed it), but they do agree that it happened and that its force was sufficient to cause the rapid expansion of the Universe and power the formation of atoms, molecules, and eventually whole galaxies of matter. They even posit that most of the matter in the Universe is so-called "dark matter," invisible to electromagnetic radiation: a thermos flask made out of "dark matter" really would be a steady-state system, as long as nobody went and opened the thing. All of this provides a comforting bedrock underneath the scientific laws we build from everyday observations, and so has validity as a worldview on purely pragmatic grounds; but, science being what it is, harder evidence was required to support the theory when it was first proposed.

That evidence was first produced by Edwin Hubble, after whom the most powerful man-made telescope is named. Hubble's observations of massive and very distant galaxies demonstrated a phenomenon called 'redshift' - light perceived from those galaxies far, far away is redder than it ought to be, because the wavelengths of the light are increased. This corresponds to a decreased frequency of the light, or a reduced photon energy, depending on whether one views light as a wave or a particle (of course, like de Broglie, one can reject the excluded middle there and argue that it's both); Hubble reasoned that this redshift could be accounted for by the Doppler effect, which arises whenever there is relative movement between the source of a wave and some observer - you hear it with sirens from moving emergency vehicles, for example. Hubble's explanation for redshift allowed for calculations both of how far away these galaxies were and how fast they were moving, relatively, away from us; and that allowed an indirect estimate of the age of the universe. Also, theoretically, with enough data, the ability to pinpoint the location of the original Big Bang, although that hasn't been the subject of much scientific curiosity.

You'll have noticed this blog wasn't set up to be about the Doppler effect; and, indeed, there's another explanation for redshift that was proposed by Albert Einstein (who was not a fan of the expanding-universe paradigm). In linking classical Newtonian physics to his own theory of special relativity, Einstein's General Theory of Relativity argued that the velocity of light, commonly accepted as a 'speed limit' for the universe and a scientific constant, was in fact only constant absent gravitational effects: gravity bends light, according to Einstein, which is why the massive gravity of black holes make them invisible. Scientists accept the existence of all this massive invisible gravity in the universe - black holes and dark matter and so on - because otherwise the calculations extrapolated from their scientific laws don't tally with the observed amount of matter there is around. Given the choice between invalidating the assumptions of conventional science, and invalidating the universe it supposedly measures, scientists historically and routinely choose the latter, so it's not surprising that they're far happier with dark matter they can't see than a perpetual-motion machine they can see. Happily for conventional science, there is also other evidence out there that supports the assumptions Einstein made.

One of the more important items of evidence on that list was identified by Irwin R. Shapiro (yes, finally, we're about to discuss the Shapiro Effect). He it was who experimentally confirmed the predictions of Einstein's theory in 1964 by measuring a delay of 200 microseconds in radar signals bounced off the planets Venus and Mercury. This demonstration of the delay in electromagnetic radiation due to gravity provides an alternative explanation for redshift - not that the galaxies viewed are moving away from us, but that the light reaching us from them is being slowed by the gravitational pull of the intervening matter. Shapiro's result has been replicated many times since, for example with the transponders on the Mariner 6 and Mariner 7 space probes. The Viking Mars lander left transponders on the surface of that planet, which have also confirmed the Shapiro effect in operation.

There are, of course, a host of scientists in the mainstream who will explain at even greater length than I took here why the redshift phenomenon is still confirmation of the Big Bang hypothesis, and why the Shapiro effect doesn't discredit this evidence. I don't oppose them; I just find it interesting how the edifice of Science selectively disregards valid interpretations of the evidence its methods uncovers.


Heather Henry said...

I've not yet read this post, will come back and do so when it's not 3 am. I did want to let you know that I have an award for you on my bloggity. Happy Easter, friend. Hope it is splendidly groovy!! :)

Heather Henry said...

Hey there, hope all is well with you!