Good Questions: Drowning by weight, not numbers

William Hartston
Sunday 23 October 2011 06:10

DEATH, time, the weather and some complex relationships are among readers' problems tackled this week, and we begin with a piece of classical wisdom.

Pliny the Elder claims of drowned bodies that male corpses float face upwards and female corpses, more modestly, face downwards. Aldous Huxley wrote an amusing poem on the subject. Is Pliny's statement true? (Brian W Aldiss, Oxford).

Only if Pliny's drowned acquaintances were all slim, small-breasted women and pot-bellied men. Most drowned bodies initially float face downwards, owing to the weight of the arms. Excess fat in breasts and stomach, however - since fat floats - may produce a face-up effect. Since women have a higher proportion of fat than men, and it is mainly on their front, they are more likely than men to float on their backs, especially if they are large- breasted women.

Whatever the sex of the deceased, however, after some time in the water the abdominal cavity is likely to fill with gases of putrefaction, causing a face-down body to flip over.

In Aldous Huxley's poem, Second Philosopher's Song, the speaker, contemplating suicide by drowning, says:

'My Thames-blown body (Pliny vouches it)

Would drift face upwards on the oily tide.'

But if the lady to whom the poem is addressed were to drown:

'Your maiden modesty would float face down,

And men would weep upon your hinder parts.'

Unfortunately Pliny was wrong. Millais gets Ophelia the right way up at the Tate Gallery, but his picture may have caught her as she 'chanted snatches of old tunes' before 'her garments, heavy with their drink, Pull'd the poor wretch from her melodious lay, To muddy death.'

Sources: Bernard Knight, professor of forensic pathology, University of Wales College of Medicine, Cardiff. The Aldous Huxley poem may be found in 'A Choice of Comic and Curious Verse' (Penguin).

In broadcast weather forecasts, much use is made of the terms 'sunny periods' and 'showers', often in combination with each other. Are there any official Meteorological Office definitions of these phenomena? (C R Chandler, Bedale, North Yorks).

These and other concepts are precisely defined, but the Meteorological Office does not spread the word around. So here, for the first time, are some extracts from the Met Office dictionary:

Sunny periods or spells: sunny for an hour or two at a time; all in all more sunshine than cloudiness.

Sunny intervals: broken sunshine for a total of less than half of that theoretically possible in a day.

Sunny: Sunshine most of the time.

Scattered showers: geographically well-spread out, with a small probability (around one in 10) of any one place getting a shower.

Shower: precipitation from a convective cloud (bubble-type, broken cloud), usually lasting 15-20 minutes.

Rain: precipitation from layered cloud.

Morning: dawn until noon.

Afternoon: noon to 6pm.

Evening: 6pm to 10pm.

Night: 10pm to dawn.

Imminent (in gale warning): within six hours.

Soon: In six to 12 hours.

What are the definitions of cousin, first cousin, second cousin, cousin once-removed, etc? (Tom Gaunt, Milton Keynes).

Your aunt's (or uncle's) child is your first cousin. So, most simply, a first cousin is someone with whom you share a grandparent. Second cousins share great-grandparents; third cousins share great-great grandparents, and so on. The son or daughter of your first cousin is your first cousin once-removed. In other words, your grandparent is their great-grandparent (or vice versa). Each further removal involves another generation gap in the family tree.

'Cousin' is used either specifically to mean first cousin (also formerly known as cousin german) or a distant relative of whom one cannot be bothered to work out the precise relationship.

When I look at the small second hand on my wristwatch, it appears at first not to move. Just as I think my watch has stopped, the hand begins to move normally again. This only happens if I have not looked at the watch for some time. Is this due to some delay in the brain's realising what the eye is relaying to it? (A Heckley of Shildon, Durham).

The perception of motion is a complex phenomenon which is by no means perfectly understood. What we know is that two separate processes are involved. If we keep our head and eyes still, a moving object will create a moving image on the retina. Alternatively, we may follow a moving object by moving our eyes and head, in which case the object's image retains a stable position on the retina.

In either case, it is easy to surmise how the brain understands that something is moving - in the first, a moving image is detected; in the second, muscular effort is needed to move eyes and head. But why does the world seems to stay still when we move our eyes and head around?

In some way, the two separate processes of retinal image movement and muscular effort seem to cancel each other out. The question is further complicated by consideration of a simple experiment: Close one eye, then apply gentle pressure to the side of the other one. This passive rotation of the eyeball causes apparent motion in what is being viewed.

The implication of this and other more complex experiments, is that it is not the movement of the eyes that enable us to judge motion, but the commands from the brain to move the eyes.

What may be happening when Mr Heckley looks at his watch is a delay in switching between two motion-detecting systems. First, the eyes move to focus on the watch, then move down to the second hand, positioned above the figure six.

During this phase, indication of motion is given by eye and head movement. With the image of the watch then fixed on the retina, the other system comes into play to detect the motion of the second hand.

Looking again after a short delay may find the brain in the correct modality, so the motion of the second hand is immediately perceived. A longer delay, however, may require the whole process to be gone through again.

Interestingly, some experiments in the 1970s suggested that infants below the age of six months have difficulty connecting a moving object with the same object when stationary. It was claimed that they saw and followed movement, but showed no sign of recognition if the moving object was suddenly substituted by something else.

If object recognition and movement perception are distinct processes, arising at different times in our development, that could also contribute to the problem of watching second hands.

Main sources: Eye and Brain, by R L Gregory; Infancy by J Gavin Bremner.

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