| This weeks
FactFile is taken from 'Cassell's Laws of Nature'
by James Trefil! See details of the book at Amazon.com
or Amazon.co.uk
2621/ The term "acid
rain" has been in the scientific vocabulary since the
middle of the 19th century, when British scientists noticed
that air pollution in the industrial Midlands was causing
the rain to become more acid than normal. It was not until
the latter part of the 20th century, however, that acid rain
became well recognized as an environmental threat.
2622/ Chemists use a
quantity called pH (for 'power of hydrogen') to describe the
amount of hydrogen ions in a fluid. By convention, the pH
of pure water is taken to be 7.
2623/ Normal rain is
itself acid, even in the absence of factories. This is because
as raindrops form and fall, they dissolve carbon dioxide in
the air and react with it to produce carbonic acid (h2co3).
Pure rain, falling through unpolluted air, will be a fluid
with a pH of 5.6 by the time it hits the ground. Human activity
is the cause of most of the acid rain that falls, but there
are natural sources as well, from volcanoes and lightning
strikes to the actions of bacteria. Generally, if we were
to shut down all the factories and stop driving cars and trucks,
we would expect the pH of rain to be about 5.0. Most scientists
now define acid rain as having a pH lower than 5.0.
2624/ If you flip a coin
ten times in a row, the odds are 1024 to 1 against getting
all heads.
2625/ The existence of
antiparticles was first predicted by Paul Dirac in a paper
published in 1930. The easiest way to visualise how Dirac's
theory works is to imagine a level field. If you dig a hole
in the field, there will be two things there - a hole and
a pile if dirt. Think of the pile of dirt as the normal particle,
and the hole, or the "absence of a pile of dirt",
as the antiparticle. If you shovel the dirt back into the
hole, both hole and pile disappear - the equivalent of the
process of annihilation - and you are left with a level field
again. The first actual detection of an antiparticle was by
Carl Anderson in 1932, who received a share of the 1936 Nobel
Prize for Physics. He is probably the only person in history
who got a Nobel prize before he got a permanent university
position!
2626/ William Henry Bragg
(1862-1942) and William Lawrence Bragg (1890-1971) were English
physicists and the only father-and-son team to be jointly
awarded a Nobel prize (for Physics in 1915) for research into
the way that X-rays scatter from crystals. Both Niels Bohr
(1885-1962) and his son Aage Niels Bohr (1922-) won the Nobel
Prize for Physics, though for different work. Niels in 1922
and Aage in 1975. You can see all the winners of the Nobel
prize for Physics here.
2627/ Explaining the
Catalytic converter in your car... The catalytic converter
in your car is a fine mesh made of the metals palladium and
platinum through which the exhaust of the car's engine passes.
The metals catalyze a number of chemical interactions. First,
they absorb carbon monoxide, nitrogen monoxide, and oxygen,
and each nitrogen monoxide molecule is broken into its constituent
atoms. The carbon monoxide is combined with an oxygen atom
to produce carbon dioxide, while nitrogen atoms combine to
form nitrogen molecules. At the same time, the extra oxygen
allows hydrocarbons that were not burned in the car's cylinders
to burn completely into carbon dioxide and water. In this
way, an exhaust stream that contains carbon monoxide (a lethal
poison) and substances that lead to Acid Rain, as well unburned
fragments of the original molecules in the gasoline, is converted
into a relatively innocuous mix of carbon dioxide, nitrogen
and water.
2628/ The first person
to see a cell was the English scientist Robert Hooke, who
was curious about why cork was so buoyant. In 1663 he was
looking at a thin slice of cork under an early microscope.
He found it to be divided into tiny compartments that reminded
him of the small rooms occupied by monks in a monastery, so
he named them cells.
2629/ The amount of heat
needed to melt or boil a substance is called the latent heat
of fusion or latent heat of vaporization, respectively. It
can be very large: it requires 420,000 joules of heat energy
to raise 1 kilogram of water from 0ºcentigrade to 100ºcentigrade,
but 2,260,000 joules to convert that same kilogram of water
at 100ºcentigrade to a kilogram of steam at 100ºcentigrade.
2630/ It is one of the
wonders of chemistry that a violently reactive substance like
sodium and a highly poisonous gas like chlorine combine to
give us ordinary table salt.
2631/ The human body
is at its lowest ebb at around 3 or 4am (what one poet has
called the 'dark midnight of the soul'), and people are more
likely to die at this time than at any other.
2632/ The best analogy
for deterministic chaos (or chaos theory) is white water on
a rapidly flowing section of a mountain stream. If you set
two leaves in motion next to each other on the upstream side
of the white water, they will most likely be widely seperated
by the time they reach the downstream side. In a system like
this, a small difference in the initial conditions (the position
of the leaves) can result in a large difference in the outcome.
2633/ A rainbow is created
when sunlight hits raindrops in the air. The light is refracted
when it enters the raindrop, is reflected off the back surface,
and is then refracted again when it re-emerges from the front.
This is why we see rainbows when there is rain falling in
front of us and the Sun is at our back. Because of dispersion,
each colour of light is concentrated around a different angle,
which is why we see the colours arrayed in an arc.
2634/ For a beam of light
from a distant star that just grazes the Sun, Einstein predicted
that the deflection would be 1.75 seconds of arc (about one
two-thousandth of a degree), whereas Newtonian physics predicted
just half that. Thus the measurement by Sir Arthur Eddington
(1882-1944) during the 1919 total solar eclipse of a deflection
of 1.6 arc seconds was a triumphant experimental confirmation
of the theory of general relativity.
2635/ One of the best
studies of natural selection in action was carried out on
an insect called the peppered moth (Biston betularia).
Living in central England, these moths were most often found
on lichen-covered trees. The lichen in this area is light-coloured,
and the moths that matched the lichen were less likely to
be seen by predators. During the 19th century central England
became heavily industrialized, and much of the moth's home
territory became severely polluted by smoke and soot. The
tree trunks turned black, a significant change in the moth's
environment. The moth population started to change, with darker
colours being favoured in polluted areas. Eventually, entire
populations turned black. The change took place just as evolutionary
theory predicted - the small number of dark moths in the normal
population gained an enormous competitive advantage because
of the change in the environment, and gradually their genes
came to dominate.
2636/ The story of the
peppered moth isn't over yet, though. Starting in the 1960s,
air pollution controls began to be instituted in England,
and the soot accumulation in the Black Country began to decrease.
In response, the moth population has started to shift back
to light from dark - a result that would, once more, be predicted
from Darwinian arguments.
2637/ One reason ocean
driftwood is so highly prized for use in fires is because
during its time at sea the wood absorbs many materials, and
these materials impart a variety of colours to the flames
when the wood is burned.
2638/ Carl Friedrich
Gauss (1177-1855) - amongst other things - studied the mathematics
of probability and statistics, and was the first to write
down the expected distribution of random points around an
average value. The so-called bell curve or normal-distribution
that resulted from his calculations is also known among scientists
as the Gaussian distribution.
2639/ The density of
the Moon is about 3.6 times that of water - about the density
of the rocks in the Earth's outer layers. But the density
of the Earth is about 5.5 times that of water (the Earth's
core is made of heavy iron and nickel). In essence, the Moon
is like the Earth without its core.
2640/ The biggest greenhouse
effect we know of is on our sister planet Venus. The Venusian
atmosphere is almost all carbon dioxide, and the planet's
surface is a steamy 475 degrees centigrade as a result. Climatologists
believe that we have escaped this fate because of the presence
of oceans on the Earth. Because of the oceans carbon is taken
out of the atmosphere and stored in rocks such as limestone,
thereby pulling carbon dioxide out of the atmosphere. Venus
had no oceans and all of the carbon dioxide injected into
its atmosphere by volcanoes stayed there. Consequently, on
Venus we see an example of what is called a runaway greenhouse
effect.
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facts...
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