Seven-Tenths (3 page)

Over the port stern will go a magnetometer to measure magnetic variability in the Earth’s crust, and down in the lab is a gravimeter to record differences in its gravitational field. This machine looks,
and is, expensive. It is suspended in a cradle mounted in computer-controlled gimbals, dipping and tilting so it appears to be the one thing in the lab which is constantly in motion, whereas it is really the only thing aboard remaining utterly still while the ship gyrates about it. At supper the conversation turns to where might be the best place on Earth for setting high-jump records, a particular spot with significantly weaker gravity. All the best ones seem to be covered by a couple of miles of water. In response to a remark of mine which betrays real ignorance about gravity, Roger says kindly:

‘I suppose one always imagines the surface of the oceans as basically flat. Ignoring waves and local storms, of course – they’re just “noise”. But apart from its being curved to fit the surface of the globe, one thinks of the sea as having to be flat because at school we’re told water always finds its own level so as to be perfectly horizontal. On a small scale that’s pretty much true, though when I was about ten I remember being surprised when someone pointed out that all rivers are tilted, and if you row upstream you’re also rowing uphill as well as against the current. Anyway, since gravity varies from place to place it acts variably on the sea, too. When you start using instruments like the ones aboard this ship you really appreciate how the ocean surface actually dips and bulges all over the place. It shows up best from space.’

He explains that by having enough satellites in orbit making passes over the same area, day after day for months on end, it was possible to build up a mean reading for the height of the sea’s surface at that spot. It took a long time because there was a good deal of ‘noise’ to be discounted: wind heaping, sudden areas of low atmospheric pressure which could suck the sea upwards as if beneath a diaphragm, even very low-frequency waves with swells so long they might take half a day to pass. But if the satellites went on measuring the same spot for long enough such fluctuations would even out and a geodetic point be established: a mean distance to the sea’s surface as measured from the centre of the Earth. By building up enough geodetic points it soon became clear that the oceans were anything but flat.

‘What’s more, if you match this up with the underlying features on the seabed, you’ll find that the surface of the sea broadly mimics
the topography underneath. And the reason for
that
is fluctuations in gravity, which depends on the density of the crustal material.’

It is a pretty notion, that the sea follows the Earth’s crust like a quilt laid over a lumpy mattress. It is also odd to think that to some extent the depths of the oceans can be read from space. Over a plate of steak and kidney pie (the galley makes no concessions to the tropics) I presume this means that sometimes a ship has to go uphill and downhill.

‘Certainly. But the “hills” are so slight you’d never know. We’re talking a few tens of centimetres here, spread out over kilometres. Sure, a ship often has to go uphill, though it won’t be using any more energy. All points on the hillock’s surface have the same gravitational potential, obviously.’

This is not obvious to me, and nor is it any more so after Roger has explained it several times in different ways. I tell myself that physics is humiliating not when it defeats the intellect but when it confounds the imagination. This makes me feel better. Giving up on me, he reverts to a sort of ‘Ripley’s Believe It or Not’ mode suitable for lay company. Roger is himself a geologist and in describing the planet gives the impression of talking about a beach ball under-inflated with water: labile, plastic, sagging and crinkling and bulging. It is not only the oceans which respond tidally to the Sun and the Moon; the Earth’s surface does as well, rising and falling twice a day. When the Moon is directly overhead it is pulled up by half a metre.
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What is more, this elastic crust seems to have a frequency of its own at which it resonates. A Russian geologist, S. L. Soloviev of the Moscow Institute of Oceanology, recently made seismograms of micro-earthquakes under the Tyrrhenian Sea. Using bottom seismographs (developed from nuclear explosion detectors originally designed to enforce the Test Ban Treaty), Soloviev began picking up a distinct, ultra-low frequency oscillation which he
thought was most likely the fundamental frequency of the Earth’s crust itself.

That night I go to bed with my head full of marvels. In the course of the evening I had also learned that the sea levels at either end of the Panama Canal were different by nearly half a metre, and the same went for the sea on either side of the Florida Peninsula. This was caused by things such as the heaping effect of wind and the Coriolis force. But I am most captivated by the idea of the Earth’s crust vibrating at an ascertainable frequency since it would theoretically be possible to calculate the precise note. True, it would probably not be a pure tone because there would be all sorts of harmonic interference from irregularities such as mountain ranges. Yet it ought to be possible to determine the fundamental note of the planet, the music of our spheroid.

I also wonder at the notion of the sea’s surface modelling the plains and mountains, chasms and basins beneath the keel. It is not hard to believe this at the moment since we are all being thrown about our bunks by the
Farnella
’s plungings as if she were ploughing across rough country. We have reached the foothills of the Necker Ridge. More than 2 miles below us a mountain chain thrusts steeply upwards. I bang about in my wooden trough and tell myself this is just ‘noise’.

Next morning the sea is quieter. The ship heaves to and a certain tension comes over the scientists as one by one the precious instruments are carefully deployed. Launchings and retrievals are the moments when damage is most likely and although there are several workshops aboard for mechanical and electronic repairs our sailing patterns are planned to the nearest nautical mile for the next several days. Worries revolve around personal responsibility for the correct functioning of machines. The spectre of disgrace and delay flits about the ship until everything is safely in the water and the test readings are monitored. In the end these anxieties are probably rooted less in codes of professionalism than in the huge expense of modern oceanography. Great sums of money are being lowered delicately into the ocean. Any delays would be tantamount to damage, chunks of money becoming dislodged and drifting down to the
seabed where they would dissolve and be lost for ever. Even the crew seems less laconic while all this is going on. When we are under way again there is a feeling that the
Farnella
is more in the hands of scientists than seamen and the crew can now be found in odd corners reading copies of the Hull
Daily Mail
which were flown out in bundles to the shipping agent in Honolulu. Shipboard life settles into routine. It is still curious to be in the Pacific in a British ex-trawler with a television in the lounge showing video-cassettes of highlights from last season’s Hull Kingston Rovers matches. Not to mention the cuisine. At the same time we are, as an IOS zealot proudly says, ‘at the leading edge of geophysical seabed surveying’.

The issue of who is really in command of the ship is interesting, as is the whole idea of a joint survey paid for by the US Government using a significant proportion of British equipment and scientists. In a legal sense the Captain has full and final responsibility for the ship. Yet it soon becomes plain that his actions are largely determined by the exigencies of the survey, which is costing the American taxpayer such a pretty penny. It is the USGS which has chartered the vessel and hired GLORIA and so calls the tune. On the other hand the scientist formally in charge of this particular cruise is a Briton, one of GLORIA’s original developers at IOS. At the same time one of the young American women aboard is responsible to her government for completing this leg of the survey. … All this interweaving of authority is glossed for me as ‘A joint effort. Absolute cooperation and consultation. Democracy in action like you wouldn’t believe.’ This is emphatically not science for the sake of science, a matter of drifting about the Pacific like the old
Challenger
in the 1870s, sounding here and dredging there at whim. This is time-and-motion science, with a given area of blank map to be filled in a given time. And the whole issue, for very cogent reasons of physics, hinges around the matter of navigation.

As is all too clear to anybody swimming in circles looking for a lost boat in the middle of the ocean, one has no position in water. When mapping the seabed from a moving ship, therefore, accurate navigation is of crucial importance. Without the ship’s position
being known from one second to the next the most beautiful chart of peaks, ravines and plateaus would be useless. The only thing known would be that they were down there somewhere. Establishing the ship’s course along lines as straight as possible (always allowing for the Earth’s curvature) requires much work, not least because the swathes GLORIA maps must lie next to each other without gaps or wasteful overlapping. On the chart table in the lab is the dot of Johnston Island, a pencil circle whose diameter represents 400 nautical miles inscribed about it. High up in its top left-hand quarter a chord shows the first leg we have just started. Next to it is written the estimated time at which we should come about for the return pass, each leg getting longer as we eat downwards into the circle. If all goes well, by the end of a fortnight we should have hatched off about a quarter of the total area.

While the lab computers flicker with the instruments’ returning signals, various repeater gauges give the ship’s speed through the water, its speed over the ground, the wind speed and any consequent degree of yaw. If to remain on a straight course against a quartering wind and current the
Farnella
needs to sail crabwise, GLORIA’s angle will also be fractionally oblique to its correct path. The result is that its signals will no longer be exactly at right angles to this course and the map will be distorted. Information on all these factors is fed into the computers, which correct for them. In order to determine the ship’s position at any moment the
Farnella
uses GPS or Global Positioning System. This depends on satellites and eventually, provided there are still spare slots in an already overcrowded geostationary orbit, the system will cover the Earth and in theory allow a person anywhere on the planet’s surface to determine his position to within a few metres. This would not be of the slightest use to a lost swimmer looking for his boat.

Bored with the sight of bright red digital figures flickering their decimal points on display panels, I wander off in search of sound. Down in the forward hold, above the banging of the ship’s forefoot into wave troughs, the chaffinch-like chinking of the 10 kilohertz ‘fish’ can be heard through the steel hull. Up on the stern deck there is a sharp cracking sound every ten seconds, the higher frequencies
of the air gun’s detonations being transmitted back up the compressed air hose. In the water astern white puddles dimple and churn to mark the boilings of released air. They follow the ship with the measured pace of footsteps.

Very occasionally from a chance position down in the hull, at some freak acoustical window, it is possible to hear GLORIA’s peculiar yodel. The instrument emits a correlation signal; instead of a single bleep its pulses take the shape of a whistle which swoops up and down. This is so the echo will be unmistakable, the electronic ears listening for its return being tuned to exclude all other signals. Even so, knowing how to read the GLORIA trace as it emerges from the plotter is a matter of much experience. Since parts of the signal are making a round journey of 60 kilometres or so, while others may travel only 5 (that edge of the fan nearest the ship) the returning echoes become mixed up with the fresh outgoing pulses, even with still fainter returns from previous signals. There may also be leakage and scattering, with stray echoes reflected back down from the water’s surface.

How different the
Farnella
is from the old
Challenger
! The real distinction between this kind of oceanography and all that went before is not merely that the technology has changed, and with it the techniques for analysing data. It is that the scientists themselves are using different senses. Nobody is actually listening to these signals returning from unexplored regions laden with information. The lab is filled, not with the hollow pinging familiar from submarine war film soundtracks, but with the click and whir of plotters and jocular bouts of repartee. No one now wears headphones and a rapt, faraway look, attentive in ambient hush. For all that modern oceanography relies so much on acoustic techniques, it is machines which do the listening. When I flip a switch on a panel which feeds through a tiny speaker the actual noise of the signals, the American technician Bob sets his face into that expression which in TV shorthand stands for displeasure. ‘That sound gives me a headache,’ he says. ‘It’s so goddamn monotonous.’ I refrain from babbling about hidden subtleties, since they are still there; it is just that they are on an inked printout.

Allowing electronic devices to replace our senses while reducing so much information to visual imagery must have its consequences. Generally speaking, under-used faculties tend to atrophy. It has long since become a cliché in the pages of
The Lancet
and the
BMJ
to wonder whether the old-fashioned, pre-war family GP with his training in how to watch, to listen, to smell, touch and even taste may have understood more about his patients’ health than does his modern counterpart with his reliance on laboratory techniques and diagnostic machinery. Perhaps in dealing with the natural world at an electronic remove scientists in certain disciplines may also risk missing as much as they learn. How many naturalists nowadays have the artist’s eye, like the great nineteenth-century scientists who so lovingly sketched their specimens in the field? It is not only sensibility but memory itself which atrophies, since the need for attentive observation is less. The camera takes the place of the eye, the recorder of the ear, the computer of the memory. A laconic finger on a keyboard summons up data, an image. Less need, less time now for Edward Lear’s scrupulous parrots or Audubon’s American birds, for the hundreds of sketches made aboard the
Challenger
or for anatomical drawings as fine as Jan van Rymsdyk’s of the human uterus. Nor is there much call for writing that describes specimens as Philip Gosse described
Cleodora
, a tiny snail known as the sea butterfly, which floats in tropical oceans. ‘A creature of extreme delicacy and beauty … The hinder part is globular and pellucid, and in the dark vividly luminous, presenting a singularly striking appearance as it shines through its perfectly transparent lantern.’
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