withstand difficult conditions and even survive without food for
many weeks, yet we die quickly without air to breath or with
direct exposure to unusually high or low temperatures. It is thanks
to eons of
Darwinian evolution that we are perfectly designed for
but perhaps we should not be too casual about the extraordinary good
fortune that brought us to this point.
We all know that:
every one of us is an emotional-intellectual island connected to
that 'everything else' by the complex interaction of our five
Then we have skin sensitive enough to tell us
about shape and texture, a mouth that accurately differentiates
between different chemical substances we are about to consume in the
form of taste and we have an air inlet that can pick out the
presence of a specific molecule within a million others in the
atmosphere as the sense we call smell.
These points of stimulus combine to give life to the most
remarkable array of aspects of self. Love, fear, loathing,
compassion, laughter and countless other emotions make us special
and m ark us out as entities that are utterly different to the rest
Those with religious faith turn to their interpretation of God to explain the unexplainable and the more scientific amongst us turns to the Anthropic Principle.
The good old 'Anthropic Principle' is
less there to help us answer the BIG question than to avoid having
to deal with it. It accepts the vanishingly tiny probability of
human existence by stating that the rules of the Universe that
produced us have to be exactly as they are or we would not be here
to perceive them.
The miracle of
life on Earth is due to our narrow temperature band that provides us
with liquid water and, as we have explained, it is the Moon that is
responsible for maintaining the perfect tilt that provides our
benign climate. But amazingly, it was the very act of the Moon's
creation that produced the first link in the chain of events that
would lead the Universe to make you!
Although having obtained a PhD in astronomy at a very
early age, Wegener was
particularly interested in geophysics, a field of study that was in
its infancy at the time.
was, at the time, no reasonable explanation as to how such a state
of affairs could have com e about. It had been postulated that the
solution to this puzzle had to be land bridges that must have
existed in very ancient times and that had allowed both plants and
animals to move between continents. However, there were many examples that could not be explained in this way.
He also found that if
the continental shelf is studied, rather than the apparent coastline
shaped by current sea level, the fit is often very much better.
Later in his life he wrote about this process of logical deduction.
Wegener spent a considerable period collecting further examples of extended flora and fauna and the available evidence continued to support his early theory.
For example, he found the fossils of plants and creatures in places
where the climate must have been significantly different
when they were alive and flourishing, such as fossilized cycads -
ancient tropical plants found as far away from the tropics as
Spitsbergen in the Arctic.
He suggested that this supercontinent had broken up and had begun to drift apart 300 million years ago.
He called the process 'Continental Drift' and although he wasn't the first to suggest that there had originally been a single continent, he was able to provide substantial evidence to back up the claim. Wegener first published his findings and his hypothesis in his book The Origin of Continents and Oceans.20
Although it was brilliantly argued, his ideas were not widely accepted at the time. A flood of scientific indignation broke over Alfred Wegener.
This happened for a couple of reasons: firstly, his theory was revolutionary, which inevitably clashed with the conservative tendencies of other experts; and in addition, although Wegener was certain that continental drift must have taken place, he had no theory as to how or why this might have happened.
The best he could
suggest was that the continents, influenced by centrifugal and tidal
forces as the Earth spun on its axis, were simply ploughing their
across the surface of the planet.
The truth of the matter is that Wegener was wrong in terms of his suggested mechanism, but quite correct in his basic assumption. Rather than ploughing their way across the planet's surface, the continents 'float' on what is known as the 'asthenosphere', the underlying rock of our planet.
This is under so much pressure and becomes so incredibly hot that it
acts more like thick treacle than solid rock.
An earlier position held by many experts had been the 'contraction theory'. This suggested that the Earth had begun its life as a molten ball and that as it cooled it had cracked and folded up on itself.
This folding, the theory
suggested, was what had created mountain ranges. The real problem
with the contraction theory was that all mountain ranges should
therefore be of the same age and it was rapidly becoming apparent
that this could not be the case. Wegener had suggested that
mountains were constantly being created as landmasses came into
contact, exerting unbelievable pressure and pushing up land at or
close to the points of contact.
In 1929 Arthur
Holmes, a physicist at the Imperial College of Science in London
suggested that the mantle of the Earth undergoes 'thermal
convection'. The Earth's mantle is that region immediately below the
outer crust. It extends all the way down to the Earth's core. Its
composition varies with increased pressure and temperature but it
makes up the biggest part of the Earth.
process takes place with porridge that is boiling in a saucepan.
Holmes was quite taken with Wegener's idea of continental drift and
suggested that the tremendous pressures caused by thermal convection
could act like a conveyor belt. This might cause the continents to
break apart and to be 'carried' across the surface of the planet.
By the 1960s there was a greater understanding of the 'oceanic ridges'-regions where, it was being realized, Holmes' thermal convection might actually be taking place. It was also realized that oceanic trenches occurred, together with arcs of islands, close to the continental margins. All of this meant that convection was not only probable but certain.
other scientists, R. Deitz in
1961 and Harry Hess in 1962 separately published similar hypotheses
based on mantle convection currents, and continental drift becam e
So large are the mid-oceanic ridges that they are higher than the Himalayas and are more than 2,000 kilometers wide. Associated with the ridges are great trenches that bisect the length of the ridges and which can be as deep as 2,000 meters. The greatest heat flow from the ocean floor takes place near the summit of the mid-oceanic ridges.
There are also far m ore
earthquakes on and around the ridges than are experienced elsewhere,
showing these to be geologically active areas.
It was discovered that, either side of the m id- oceanic ridges, it was possible to detect these past reversals in the Earth's magnetic field. The conclusion was that new material was constantly being thrown up on the ridges and was being pushed outwards on either side.
The reversals of the magnetic field demonstrated that this
process was ancient but that it was still taking place.
The trenches are
generally long and narrow and they are often associated with, and
parallel to, continental mountain ranges. In addition they run
parallel to the ocean margins. There is great seismic activity
associated with the deep-sea trenches, indicating that they too are
associated with the process of seafloor spreading and that they are
directly related to the oceanic-ridges.
new material spreads outwards until it makes contact with a
continental plate and will then be 'subducted' beneath the
continent. The lithosphere at this point sinks back into the
asthenosphere, where it once again
Probes sent to these planets have now shown conclusively
that plate tectonics do not take place on any of our companion
worlds, making it a strictly Earth-bound phenomenon, at least as far
as our own solar system is concerned.
There is a growing body of evidence to show that in both cases the answer is almost certainly the Moon.
What is m ore, it is now being suggested that
without plate tectonics the Earth may not have proved to be a
suitable haven for life at all.
As we have
seen, the Moon is definitely made of the same stuff as the Earth,
but not all of the Earth. Rather the composition of the Moon closely
resembles the material in the Earth's crust, without many of the
heavier components, such as iron, that make up the Earth's core.
There did not seem to be any other possibility,
so it is now regularly taught as though it is a fact. The major
problem of the Earth's current speed of rotation was tentatively
explained away by proposing a second impact from the opposite
direction occurring quite soon after the first.
If the Double Whack theory as correct, the
Moon should be made up of three different sets of material, but it
is not. It is made of Earth rock alone.
He points out that on Venus, for example, the same sort of forces are at work but the crust of the planet is so thick, the stresses within the crust simply cancel each other out, with the exception of a few wrinkles here and there.
Hoffman has noted that if the seventy per
cent of Earth crust that was destined to become the Moon was
returned to the Earth, it would 'fill the ocean basins with
It's a fact, though, that what we term as being 'intelligent life', such as our own species, has developed on land.
The use of fire would not be possible in a watery habitat and the
use of tools, one of the factors that is generally accepted as the
starting point of our advance, is also a dry land phenomenon.