That the radiation from the
sun (and from many sequence stars) should be
concentrated into a minuscule band of the electromagnetic
spectrum which provides precisely the radiation
required to maintain life on earth is very remarkable.
Ian Campbell, British Physicist
1
The
sun is probably the one thing we see most often
throughout our lives. Whenever we raise our sight
to the sky during the day, we can see its dazzling
light. If someone were to come up and ask "What
good is the sun? we would probably reply without
even a thought that the sun gives us light and
heat. That answer, although a bit superficial,
would be correct.
But
does the sun just "happen" to radiate light and
heat for us? Is it accidental and unplanned? Or
is the sun specially designed for us? Could this
great ball of fire in the sky be a gigantic "lamp"
that was created so as to meet our exact needs?
Recent
research indicates that the answer to the last
two questions is "yes". "Yes" because in sunlight
there is a design that inspires amazement.
The Right
Wavelength
Both
light and heat are different manifestations of
electromagnetic radiation. In all its manifestations,
electromagnetic radiation moves through space
in waves similar to those created when a stone
is thrown into a lake. And just as the ripples
created by the stone may have different heights
and the distances between them may vary, electromagnetic
radiation also has different wavelengths.
The
analogy shouldn't be taken too far however because
there are huge differences in the wavelengths
of electromagnetic radiation. Some are several
kilometers long while others are shorter than
a billionth of a centimeter and the other wavelengths
are to be found in a smooth, unbroken spectrum
everywhere in between. To make things easier,
scientists divide this spectrum up according to
wavelength and they assign different names to
different parts of it. The radiation with the
shortest wavelength (one-trillionth of a centimeter)
for example is called "gamma rays": these rays
pack tremendous amounts of energy. The longest
wavelengths are called "radio waves": they can
be several kilometers long but carry very little
energy. (One result of this is that radio waves
are quite harmless to us while exposure to gamma
rays can be fatal.) Light is a form of electromagnetic
radiation that lies between these two extremes.
The
first thing to be noticed about the electromagnetic
spectrum is how broad it is: the longest wavelength
is 1025 times the size of the shortest one. Written
out in full, 1025 looks like this:
10,000,000,000,000,000,000,000,000
A
number that big is pretty meaningless by itself.
Let's make a few comparisons.
For example,
in 4 billion years (the estimated age of the earth)
there are about 1017 seconds. If you wanted to
count from 1 to 1025 and did so at the rate of
one number a second nonstop, day and night, it
would take you 100 million times longer than the
age of the earth! If we were to build a pile of
1025 playing cards, we would end up
with a stack stretching halfway across the observable
universe.
This
is the vast spectrum over which the different
wavelengths of the universe's electromagnetic
energy extend. Now the curious thing about this
is that the electromagnetic energy radiated by
our sun is restricted to a very, very narrow section
of this spectrum. 70% of the sun's radiation has
wavelengths between 0.3 and 1.50 microns and within
that narrow band there are three types of light:
visible light, near-infrared light, and ultraviolet
light.
Three
kinds of light might seem quite enough but all
three combined make up an almost insignificant
section of the total spectrum. Remember our 1025
playing cards extending halfway across the universe?
Compared with the total, the width of the band
of light radiated by the sun corresponds to just
one of those cards!
Why
should sunlight be limited to such a narrow range?
The
answer to that question is crucial because the
only radiation that is capable of supporting life
on earth is the kind that has wavelengths falling
within this narrow range.
In Energy and
the Atmosphere, the British physicist Ian Campbell
addresses this question and says "That the radiation
from the sun (and from many sequence stars) should
be concentrated into a minuscule band of the electromagnetic
spectrum which provides precisely the radiation
required to maintain life on earth is very remarkable."
According to Campbell, this situation is "staggering".2
Let us
now examine this "staggering design of light"
more closely.
From Ultraviolet to Infrared
We
said that there was a range of 1:1025 in the sizes
of the longest and shortest electromagnetic wavelengths.
We also said that the amount of energy that was
carried depended upon the wavelength: shorter
wavelengths pack more energy than longer ones.
Another difference has to do with how radiation
at different wavelengths interacts with matter.
The shortest
forms of radiation are called (in increasing order
of wavelength) "gamma rays", "X-rays", and "ultraviolet
light". They have the ability to split atoms because
they are so highly energized. All three can cause
molecules–especially organic molecules–to break
up. In effect, they tear matter apart at the atomic
or molecular level.
Radiation with
wavelengths longer than visible light begins at
infrared and extends up to radio waves. Its impact
upon matter is less serious because the energy
it conveys is not as great.
The
"impact upon matter" that we spoke of has to do
with chemical reactions. A significant number
of chemical reactions can take place only if energy
is added to the reaction. The energy required
to start a chemical reaction is called its "energy
threshold". If the energy is less than this threshold,
the reaction will never start and if it is more,
it is of no good: in either case, the energy will
have been wasted.
In
the whole electromagnetic spectrum, there is just
one little band that has the energy to cross this
threshold exactly. Its wavelengths range between
0.70 microns and 0.40 microns and if you'd like
to see it, you can: just raise your head and look
around–it's called "visible light". This radiation
causes chemical reactions to take place in your
eyes and that is why you are able to see.
The radiation
known as "visible light" makes up 41% of sunlight
even though it occupies less than 1/1025 of the
whole electromagnetic spectrum. In his famous
article "Life and Light", which appeared in Scientific
American, the renowned physicist George Wald considered
this matter and wrote "the radiation that is useful
in prompting orderly chemical reactions comprises
the great bulk of that of our sun."3 That the
sun should radiate light so exactly right for
life is indeed an extraordinary example of design.
Nearly all
of the sun's radiation is restricted to
a narrow band of wavelengths ranging from
0.3 to 1.50 microns. This band encompasses
near ultraviolet, visible, and infrared
light. |
Is the
rest of the light the sun radiates good for anything?
When we look
at this part of the light we see that a large
part of solar radiation falling outside the range
of visible light is in the section of the spectrum
called "near infrared". This begins where visible
light ends and again occupies a very small part
of the total spectrum–less than 1/1025.4
Is
infrared light good for anything? Yes, but this
time it's no use to look around because you can't
see it with the naked eye. However you can easily
feel it: the warmth you feel on your face when
you look up on a bright sunny summer or spring
day is caused by infrared radiation coming from
the sun.
The
sun's infrared radiation is what carries the thermal
energy that keeps Earth warm. It too is as essential
for life as visible light is. And the fascinating
thing is that our sun was apparently created just
to serve for these two purposes, because these
two kinds of light make up the greatest part of
sunlight.
And
the third part of sunlight? Is that of any benefit?
You can bet on
it. This is "near ultraviolet light" and it makes
up the smallest fraction of sunlight. Like all
ultraviolet light, it is highly energized and
it can cause damage to living cells. The sun's
ultraviolet light however is the "least harmful"
kind since it is closest to visible light. Although
overexposure to solar ultraviolet light has been
shown to cause cancer and cellular mutations,
it has one vital benefit: the ultraviolet light
concentrated in such a miniscule band 5
is needed for the synthesis of vitamin D in humans
and other vertebrates. (Vitamin D is necessary
for the formation and nourishment of bone: without
it, bones become soft or malformed, a disease
called rickets that occurs in people deprived
of sunlight for great lengths of time.)
In
other words, all the radiation emitted by the
sun is essential to life: none of it is wasted.
The amazing thing is that all this radiation is
limited to a 1/1025 interval of the whole electromagnetic
spectrum yet it is sufficient to keep us warm,
see, and allow all the chemical reactions necessary
for life to take place.
Even if
all the other conditions necessary for life and
mentioned elsewhere in this book existed, if the
light radiated by the sun fell into any other
part of the electromagnetic spectrum, there could
be no life on Earth. It is certainly impossible
to explain the fulfillment of this condition having
a probability of 1 in 1025 with a logic
of coincidence.
And if all this were not enough, light does something
else: it keeps us fed, too!
Photosynthesis
and Light
Photosynthesis
is a chemical process whose name almost everyone
who's ever gone to school will be familiar with.
Most people however fail to realize how vitally
important this process is for life on Earth or
what a mystery its workings are.
First
let's brush off our high-school chemistry and
take a look at the formula for the photosynthesis
reaction:
6H2O
+ 6CO2 +Sunlight --> C6H12O6 + 6O2
Glucose
Translated
into words this means: Water and carbon dioxide
and sunlight produces glucose and oxygen.
To
be more exact what is happening in this chemical
reaction is that six molecules of water (H2O)
combine with six molecules of carbon dioxide (CO2)
in a reaction that is energized by sunlight. When
the reaction is complete, the result is a single
molecule of glucose ( C6H12O6), a simple sugar
that is a fundamental element of nutrition-, and
six molecules of gaseous oxygen (O2). The source
of all nutriments on our planet, glucose contains
a great deal of energy.
Simple
though this reaction may look, it is in fact incredibly
complex. There is only one place where it occurs:
in plants. The plants of this world produce the
basic food for all living things. Every other
living thing is ultimately nourished in one way
or another by glucose. Herbivorous animals eat
the plants themselves and carnivorous animals
eat plants and/or other animals. Human beings
are no exception: our energy is derived from the
food we eat and comes from the same source. Every
apple, potato, chocolate, or steak or anything
else you eat is supplying you with energy that
came from the sun.
But photosynthesis is important
for another reason. The reaction has two products:
in addition to glucose, it also releases six molecules
of oxygen. What's happening here is that plants
are continuously cleaning up an atmosphere that
is constantly being "polluted" by air-breathing
creatures-human beings and animals, whose energy
is derived from combustion in oxygen, a reaction
that produces carbon dioxide. If plants didn't
release oxygen, the oxygen-breathers would eventually
use up all the free oxygen in the atmosphere and
that would be the end of them. Instead, the oxygen
in the atmosphere is constantly being replenished
by plants.
| For hundreds of millions
of years, plants have been busy doing something
no laboratory has ever been able to duplicate:
Using sunlight, the produce food. A crucial
condition for this extraordinary transformation
however is that the light that the plants
receive must be precisely right for photosynthesis
to take place. |
 |
Without
photosynthesis, plant life could not exist; and
without plant life, there would be no animal or
human life. This marvelous chemical reaction,
which has never been duplicated in any laboratory,
is taking place deep in the grass you step on
and in trees you may not even notice. It once
occurred in the vegetables on your dinner plate.
It is one of the fundamental processes of life.
The
interesting thing is what a carefully-designed
process photosynthesis is. When we study it, we
can't help but observe that there is a perfect
balance between plant photosynthesis and the energy
consumption of oxygen-breathers. Plants supply
glucose and oxygen. Oxygen-breathers burn the
glucose in the oxygen in their cells to get energy
and they release carbon dioxide and water (in
effect, they're reversing the photosynthesis reaction)
that the plants use to make more glucose and oxygen.
And so it goes on, a continuous cycle that is
called the "carbon cycle" and it is powered by
the energy of the sun.
In
order to see how perfectly-created this cycle
truly is, let us focus our attention on just one
of its elements for the moment: the sunlight.
In
the first part of this chapter we looked at sunlight
and found that its radiation components were specially
tailored to allow life on Earth. Could sunlight
also be deliberately tailored for photosynthesis
as well? Or are plants flexible enough so that
they can perform the reaction no matter which
kind of light reaches them?
The
American astronomer George Greenstein discusses
this in The Symbiotic Universe:
Chlorophyll
is the molecule that accomplishes photosynthesis...
The mechanism of photosynthesis is initiated
by the absorption of sunlight by a chlorophyll
molecule. But in order for this to occur, the
light must be of the right color. Light of the
wrong color won't do the trick.
| |
THE
FITNESS OF SUNLIGHT AND CHLOROPHYLL
Plants are
able to perform photosynthesis because
the chlorophyll molecules in their cells
are sensitive to sunlight. But chlorophyll
is only able to use a very limited range
of light wavelengths and those are the
wavelengths that the sun radiates the
most. What is even more interesting
is that this interval corresponds to
just 1/1025 of the whole electromagnetic
spectrum.
In the two
graphs above, the extraordinary fitness
between sunlight and chlorophyll can
be seen. In the upper chart is the distribution
of the light emitted by the sun. In
the lower one is the light under which
photosynthesis will work. The fact that
these two curves are almost identical
is an indication of how perfectly designed
visible light is.
|
A good analogy is that of
a television set. In order for the set to receive
a given channel it must be tuned to that channel;
tune it differently and the reception will not
occur. It is the same with photosynthesis, the
Sun functioning as the transmitter in the analogy
and the chlorophyll molecule as the receiving
TV set. If the molecule and the Sun are not tuned
to each other-tuned in the sense of colour- photosynthesis
will not occur. As it turns out, the sun's color
is just right.6
In
the last chapter we drew attention to the error
inherent in the idea of the adaptability of life.
Some evolutionists hold that "if conditions had
been different, life would have evolved to be
perfectly in harmony with them as well". Thinking
superficially about photosynthesis and plants,
one could come to a similar conclusion: "If sunlight
were different, plants would have just evolved
according to that." But this is in fact impossible.
Although he's an evolutionist himself, George
Greenstein admits this:
One might think that
a certain adaptation has been at work here:
the adaptation of plant life to the properties
of sunlight. After all, if the Sun were a different
temperature could not some other molecule, tuned
to absorb light of a different colour, take
the place of chlorophyll? Remarkably enough
the answer is no, for within broad limits all
molecules absorb light of similar colours. The
absorption of light is accomplished by the excitation
of electrons in molecules to higher energy states,
and the same no matter what molecule you are
discussing. Furthermore, light is composed of
photons, packets of energy and photons of the
wrong energy simply can not be absorbed… As
things stand in reality, there is a good fit
between the physics of stars and that of molecules.
Failing this fit, however, life would have been
impossible.7
What Greenstein is saying
briefly is this: No plant can only perform photosynthesis
except within a very narrow range of light wavelengths.
And that range corresponds exactly to the light
given out by the sun.
The harmony between stellar
and molecular physics that Greenstein refers
to is a harmony too extraordinary ever to be
explained by chance. There was only one chance
in 1025 of the sun's providing just the right
kind of light necessary for us and that there
should be molecules in our world that are capable
of using that light. This perfect harmony is
unquestionably proof of intentional, deliberate
design.
In other
words, there is a single Creator, the Ruler
of starlight and of the molecules of plants
Who has created all these things in harmony
with one other, exactly as is
revealed in the Qur'an:
He is Allah-
the Creator, the Maker, the Giver of Form. To
Him belong the Most Beautiful Names. Everything
in the heavens and earth glorifies Him. He is
the Almighty, the All Wise. (Surat al-Hashr: 24)
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