A JOURNEY IN RELATIVITY

BY JULIAN S. HUXLEY

RELATIVITY is in the air. It is so much in the air that it becomes almost stifling at times; but even so, its sphere so far has been the inorganic sciences, and we have heard little of the equally important biological relativity. We have all heard the definition of life as "one damn thing after another": it would perhaps be more accurate to substitute some term such as relatedness for thing.

We live at a certain rhythm in time. We live at a certain level of size in space. Beyond certain limits, events in the outer world are not directly appreciable by the ordinary channels of sense, although a symbolic picture of them may be presented to us by the intellect. When listening to the organ, sometimes there come notes which are on the border line between sound and feeling: their separate vibrations are distinguishable and pulse through us, and the more the vibrations are separable, the more they are felt as mechanical shocks, the less as sound. However, we know perfectly well that all sounds as a matter of fact depend on vibratory disturbance, and that it is only some peculiarity of the registering machinery, in ear or brain, which enables us to hear a note as continuous. Still more remarkable are the facts of vision. As I write I see the tulips in my garden, red against the green grass: the red is a continouus sensation; but the physicists appear to be justified in telling us that the eye is being bombarded every second with a series of waves, not the few hundred or thousand that give us sound, but the half billion or so which conspire to illuminate our vision. With sound, we alter the frequency of the waves and we get a difference of tone which seems to be merely a difference of more or less: but alter the frequency of light waves, and the whole quality of the sensation changes; as when I look from the tulips to the sky. The change of registering mechanism is here more profound than the change in outer

event.

Or again, to choose an example that depends more on size than rhythm, how very difficult it is to remember that the pressure of air on our bodies is not the uniform gentle embrace of some homogeneous substance, but the bombardment of an infinity of particles. The particles are not even all alike: some are of oxygen, others of nitrogen, of carbonic acid gas, of water vapour. They are not all traveling at uniform speeds; collisions are all the time occurring, and the molecules are continuously changing their rate of travel as they clash and bump.

We have only to look down a microscope to convince ourselves of the alteration in our experience that it would mean if we were to become sufficiently diminished. The tiniest solid particles in fluids can be seen to be in a continuous state of agitation-inexplicable until it was pointed out that this mysterious "Brownian" movement was the inevitable result of collision with the fastermoving molecules of the fluid. Many living things that we can still see are small enough to live permanently in such agitation; the longest diameter of many bacteria is but half a micron (a twothousandth of a millimetre), and there are many ultra-microscopic organisms which, owing to their closer approximation to molecular dimensions, must pass their lives in erratic excursions many times more violent than any visible Brownian motion.

If we could shrink, like Alice, the rain of particles on our skin, now as unfelt as midges by a rhinoceros, would at last begin to be perceptible. We should see ourselves surrounded by an infinity of motes; titivated by a dance of sand-grains; bruised by a rain of marbles; pounded by flights of tennis-balls. What is more, the smaller we became, the more individuality and apparent free will should we detect in the surrounding particles. As we became still smaller, we should, now and again, find the nearly uniform bombardment replaced by a concerted attack on one side or the other, and we should be hurled for perhaps double our own length in one direction. If we could conceivably enter into a single inorganic molecule, we should find ourselves one of a moving host of similar objects; and we should further perceive that these objects were themselves complex, some like double stars, others star clusters, others single suns, and all again built of lesser units held in a definite plan, in an architecture reminding us (if we still had

memory) of a solar system in petto. If we were lucky enough to be in a complicated fluid like sea water, we should be involved in the relations of the different kinds of particles. They would be continually coming up to other particles of different kinds, and would then sometimes enter into intimate union with them. If we could manage to follow their history, we should find that after a time they would separate, and seek new partners of the same or of different species. Some kinds of the units, or people as we should be inclined to call them, would spend most of their existence in the married state, others would apparently prefer to remain single, and, if they married, would within no long time obtain divorce.

We should be forcibly reminded of life in some cosmopolitan city like London or New York. If there existed a registrar to note down the events of these little beings' existence, and we were privileged to inspect the register, we should find that each had its own history, different from that of every other in its course and its matrimonial adventures.

If we were near the surface we should find that the outer beings always arranged themselves in a special and coherent layer, apparently to protect themselves against the machinations of the different beings inhabiting the region beyond; for every now and again one would seem to be pulled from the water and be lost among the more scattered inhabitants of the air.

If we could now revert to our old size, we might remember, as we listened to the scientist enunciating the simple formulæ of the gas laws, or giving numerical expression to vapour pressures and solubilities, that this simplicity and order which he enabled us to find in inorganic nature was only simplicity when viewed on a large enough scale, and that it was needful to deal in millions and billions before chance aberrations faded into insignificance; needful to experience molecules from the standpoint of a unit almost infinitely bigger before individual behaviour could be neglected and merged in the orderly average. And we might be tempted to wonder how the personal idiosyncrasies of our human units might appear to a being as much larger than we as we are larger than a molecule-whether kings and beggars would not fare alike, and all the separate, striving, feeling, conflicting personalities, with

their individual histories, their ancestors, successes, marriages, friendships, pains and pleasures, be merged in some homogeneous and simple effect, altering in response to circumstances, with changes capable of expression in some formula as simple as Boyle's or Avogadro's Law.

Almost more startling might be the effect of altering the rhythm at which we live, or rather at which we experience events. If only I were a writer of scientific romances, I could make a mint of money by a story based on this idea of rhythm of living. Let us see. First there would be Mercaptan, the distinguished inventor, who would lead me (lay, uninstructed, Watsonish me, after the fashion of narrators) into his laboratory. There on the table would be the machine-all but complete: handles, coils of wire, quartz terminals, gauges of rock crystals in which oscillated coloured fluids, platinum cogwheels.. dot.. dot.. dot.. dot.. He hardly dared to make the final connections, all clear and calculable though they were. He had put so much of himself into it: so many hopes. . fears.. dots....

Then there would be the farewell dinner party. First, the inventor's voice on the wireless telephone, summoning Wagrom the explorer, Glosh of The Evening Post, Stewartson Ampill the novelist, and the rest of our old friends: then the warm friendly light of the candles, the excellent port, the absence of women, the reminiscences, the asterisks, the dots.

Mercaptan refuses to allow the rest to come into the laboratory, in case something should go wrong. He straps the machine on his shoulders, makes a final connection; his life processes begin to work faster, faster, ever faster. The first effect of course was a change of colour. The blue oblong of the window became green— yellow-orange-red. Meanwhile each wave length of the ultraviolet became blue, and itself ran down the gamut of colour. Then came the turn of the X-rays. By their dim light he groped about, till they too became relatively too slow for his retina. That ought to make him blind, of course-but no! for he came into a state of nearly maximum speed where he perceived a brilliant, phosphorescent light given out by all objects, generated by disturbances of a wave length unimaginably, undiscoverably small. Meanwhile he had passed through an amazing experience

-he had heard the veritable music of the spheres! That had happened when in his acceleration he had, so to speak, caught up with the light waves until they were tuned to his ear's organ of Courti: and all that had been visible in his ordinary life was now to be appreciated by hearing. Unfortunately, as his ears possessed no lens, this universal music was to him of course merely a hideous babel of sound.

At last, as the workings of his body approached the rapidity of light's own oscillations, he entered on a new phase; surrounded on every side by an ocean of waves which lapped softly against his body-waves, waves, and still more waves.

He was in that region not unlike that from which life had escaped when it ceased to be infinitely little, a region in which none of the events that make up our ordinary life, none of the bodies that are our normal environment, have existence any more—all reduced to a chaos of billows, ceaselessly and meaninglessly buffeting his being.

Mi ritrovai

in una selva oscura.

Life is a wood, dark and trackless enough to be sure; but Mercatpan could not even see that it was a wood, for the trees. Yet it was soothing: the very meaninglessness of the wave-rocking released one of responsibility, and it was delicious to float upon this strange etheric sea. Then his scientific mind reasserted itself. He realized that he had magnified his rate of life and was consuming his precious days at an appalling speed. The lever was thrown into reverse, and he passed gradually back to what he had been accustomed to think as reality.

Back to it; and then beyond it. This time he was able to eliminate much of the disturbing effect of his rhythm change on light by an ingenious arrangement. It was an idea of which he was very proud: every alternate light wave was cut out when he doubled the capacity of each process of life, and so on in automatic correspondence. As a result he was enabled to get a picture of the outer world very similar to that obtained in the ordinary accelerations of slow processes that are made possible by running slow taken cinema records at high speed. He saw the snowdrops lift their matutinal heads and drop them again at