The Light
of Your Eyes
We have
seen how the light coming to us from the sun consists
of just three narrow bands of the electromagnetic
spectrum:
1) Infrared light,
whose wavelengths are longer than visible light
and which keeps Earth warm.
2) A small amount
of ultraviolet light, whose wavelengths are shorter
than visible light and which is necessary for
the synthesis of vitamin D among other things.
3) Visible light,
which makes vision possible and supports plant
photosynthesis.
The existence
of a range of "visible light" is as important
for the support of biological vision as it is
for photosynthesis. The reason is that it is impossible
for a biological eye to see any band of the spectrum
outside that of visible light and a very small
section of near infrared.
To explain why
this should be so, we first need to understand
how vision takes place. It begins with particles
of light called "photons" passing through the
pupil of eye and falling onto the surface of the
retina located at the back of the eye. The retina
contains cells that are light-sensitive. They
are so sensitive that each can recognize when
even a single photon strikes it. The photon's
energy activates a complex molecule called "rhodopsine",
large quantities of which are contained in these
cells. The rhodopsine in turn activates other
cells and those activate still others in turn.1
Eventually an electrical current is generated
and this is carried to the brain by the optic
nerves.
The first requirement
for this system to work is that the retina cell
must be able to recognize when a photon strikes
it. For that to happen, the photon must carry
an exact amount of energy: if it is too much or
too less, it won't activate the formation of rodopsine.
Changing the size of the eye makes no difference:
the crucial thing is the harmony between the size
of the cell and the wavelengths of the photons
coming in.
The only rays of light
that are suitable for biological vision
have wavelengths that fall within the
range of what is called "visible light".
A large part of the energy that is emitted
by the sun falls in that range.
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Designing an organic eye
that could see other ranges of the electromagnetic
spectrum turns out to be impossible in a world
dominated by carbon-based life. In Nature's Destiny,
Michael Denton explains this subject in detail
and confirms that an organic eye can only see
within the range of visible light. While other
models of eyes that could, in theory, be designed,
none of them would be able to see different ranges
of the spectrum. Denton tells us why:
UV, X-ray, and gamma
rays are too energetic and are highly destructive,
while infrared and radio waves are too weak
to be detected because they impart so little
energy interacting with matter... And so it
would appear that for several different reasons,
the visual region of the electromagnetic spectrum
is the one region supremely fit for biological
vision and particularly for the high-resolution
vertebrate camera eye of a design and
dimension very close to that of the human eye.2
Pausing to think about everything
that has been said so far, we come to this conclusion:
The sun radiates energy within a narrow band (a
band so narrow that it corresponds to just 1/1025
of the whole electromagnetic spectrum) that has
been carefully chosen. So finely adjusted is this
band that it keeps the world warm, supports the
biological functions of complex life-forms, enables
photosynthesis, and allows the creatures of this
world to see.
The Right Star, the Right Planet, and the Right
Distance
In "The
Blue Planet" we compared our world with the other
planets of the solar system and found that the
range of temperatures necessary for life exists
only on Earth. The biggest reason for this is
that the earth is just the right distance from
the sun: the outer planets like Mars, Jupiter,
or Pluto are too cold while the inner planets
Venus and Mercury are too hot.
Those who refuse
to admit that there is intentional design in the
distance between Earth and Sun suggest something
like the following:
"The universe is full
of stars, some of them much bigger than the
sun and some of them much smaller. These could
very well have planetary systems of their own.
If a star is bigger than the sun, then the ideal
planet for life would be located at a much greater
distance than the earth is from the sun. For
example, a planet in an orbit around a red giant
at the distance of Pluto could have a temperate
climate like our world has. Such a planet would
be just as fit for life as our earth is."
The claim is invalid in
one very important respect for it ignores the
fact that stars of different masses radiate different
types of energy.
 The
factors that determine the wavelengths of the
energy that a star radiates are its mass and its
surface temperature (the latter of which is directly
related to mass). For example, the sun radiates
near ultraviolet, visible, and near infrared light
because its surface temperature is around 6,000°C.
If the sun's mass were a bit bigger, its surface
temperature would be higher; but in that case,
the energy levels of the sun's radiation would
also be higher and the sun would be radiating
much more destructive ultraviolet rays than it
does.
This tells
us that any star that is to radiate light that
will support life absolutely must have a mass
close to that of our sun. But if there are to
be life-supporting planets orbiting around such
stars, those planets must be located at distances
not substantially different from that between
the earth and the sun.
In other words,
no planet revolving around a red giant, a blue
giant, or any other star whose mass was substantially
different from the sun's could harbor life. The
only source of energy capable of supporting life
is a star like our sun. The only planetary distance
that is suitable for life is the distance between
the earth and the sun.
There is
another way of expressing this truth: The sun
and the earth were each created to be just as
they needed to be. And indeed, in the Qur'an it
is revealed that Allah created everything according
to precise calculation:
It is
He Who splits the sky at dawn, and appoints
the night as a time of stillness and the sun
and moon as a means of reckoning. That is what
the Almighty, the All-Knowing has ordained.
(Surat al-Anam: 96)
The Harmony of Light and Atmosphere
Since
the beginning of this chapter we have been talking
about the radiation given out by the sun and how
it was specially designed to support life. There
is yet another crucially important factor that
we have not yet touched upon: In order for this
radiation to reach the earth's surface, it has
to pass through the atmosphere.
Sunlight certainly
couldn't do us any good if the atmosphere didn't
let it through. But it does; in fact, our atmosphere
is specially designed to be transparent to this
beneficial radiation.
The really interesting
thing is not so much that the atmosphere allows
beneficial sunlight to pass but that sunlight
is the only radiation that it allows through.
The atmosphere lets in the visible and near infrared
light that is necessary for life but it blocks
other forms of radiation that are deadly. This
makes the atmosphere an important filter against
the cosmic radiation that reaches the earth from
the sun and from other sources. Denton has this
to say about the matter:
Atmospheric gases
themselves absorb electromagnetic radiation
immediately on either side of the visible and
near infrared... The only region of the spectrum
allowed to pass through the atmosphere over
the entire range of electromagnetic radiation
from radio to gamma rays is the exceedingly
narrow band including the visible and near infrared.
Virtually no gamma, X, ultraviolet, far infrared,
and microwave radiation reaches the surface
of the earth.3
It is impossible to ignore
the artfulness of this design. The sun sends only
1/1025 of the whole range of electromagnetic radiation
that could be sent, that happens to be the range
that is good only for us, and that is the radiation
that the atmosphere lets through! At this point
it's also worth pointing out that nearly all of
the near ultraviolet that the sun radiates gets
trapped by the atmosphere's ozone layer.
Another point
that makes this even more interesting is that,
like air, water also has an extremely particular
sort of transparency: the only radiation capable
of spreading through water is the range of visible
light. Even near infrared radiation, which penetrates
the atmosphere (and thus provides heat) penetrates
only a few millimeters into water. Because of
this, only a few millimeters of the surface of
the world's oceans are heated by radiation from
the sun. That heat is conveyed in stages to lower
levels and as a result of this, below a particular
depth, the temperature of the seawater is quite
similar all over the world. This of course creates
an environment quite suitable for life.
Another interesting
point concerning water is that the different colors
of visible light are able to travel different
distances in it. Below eighteen meters, for example,
red light cannot penetrate while yellow can reach
depths of up to a hundred meters. Blue and green
on the other hand descend to 240 meters. This
is an extremely important design because the light
that is particularly crucial for photosynthesis
is the blue and green portion of the spectrum.
Since water allows these colors to penetrate more
deeply than the others, photosynthesizing plants
can live up to 240 meters beneath the surface.
These are all
facts of the utmost importance. No matter what
physical law related to light we examine, we discover
that everything has been exactly arranged so that
life can exist. Commenting on this situation,
Encyclopedia Britannica admits how extraordinary
it all is:
Considering the importance
of visible sunlight for all aspects of terrestrial
life, one can not help being awed by the dramatically
narrow window in the atmosphere absorption and
in the absorption spectrum of water. 4
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| Air as well
as water allows the passage of only that
radiation that is necessary for us to live.
All the harmful and deadly cosmic radiation
coming from distant space is caught in this
perfectly-designed filter. |
Conclusion
Materialist
philosophy and Darwinism, which takes materialism
as its source, both claim that human life appeared
in the universe by chance and that it is an "accident"
with no purpose whatsoever. The knowledge that
is being gained through advances in science however
is showing that, in every detail of the universe,
there is a design and a plan whose intention is
human life. It is such a design that, even such
a component as light, which we might never have
thought about before, is so clearly "just right"
that one can't help but be amazed.
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| Although
it blocks all other forms of radiation,
water allows visible light to penetrate
into its depth for many meters. Thanks
to this, sea plants are able to perform
photosynthesis. If water did not have
this property, the ecological balance
necessary for life on our planet could
not have come into being. |
To try and explain
such careful design as "accidental" is irrational.
The fact that all the sun's radiation is constricted
to a narrow band just 1/1025 of the total electromagnetic
spectrum, the fact that the light necessary for
life falls precisely within that narrow band,
the fact that the atmosphere blocks all other
wavelengths of radiation and admits just these,
the fact that water also blocks all other forms
of deadly radiation and permits the passage only
of visible light: Can these really all be coincidences?
Such extraordinary fine-tuning as this can be
explained not by chance but only by conscious
design. This in turn shows us that the whole universe
and all the details of that universe–including
the light of the sun that enables us to see and
keeps us warm–have been specially created and
arranged for us to live.
The
conclusion reached by science is a truth that
has been taught to mankind in the Qur'an for fourteen
centuries. Science shows that sunlight has been
created for us, in other words, that it has been
made to be "at our service". In the Qur'an we
are told that "The sun and
moon both run with precision." (Surat
ar-Rahman: 5) Elsewhere it is stated:
Allah is He
Who created the heavens and the earth and sends
down water from the sky and by it brings forth
fruits as provision for you. ...He has made
the sun and moon subservient to you holding
steady to their courses, and He has made the
night and day subservient to you. He has given
you everything you have asked Him for. If you
tried to number Allah's blessings, you could
never count them. Man is indeed wrongdoing,
ungrateful. (Surah Ibrahim: 32-34)
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