Priyantha Hettige
People are asking – Are there any other worlds like ours
out there – with life and people – or are we alone in the universe?
We
know that the stars we see are large, hot and dangerous; and the many
exo-planets,” we have found so far orbiting those stars, are rocky bodies,
varying from barren and fiery hot to extremely cold. Space is just a few
degrees above absolute zero (-273o) So, what are the
requirements for life to exist on a planet – and will it be like us?
Many
instruments and telescopes have been sent into space to get information about
our surroundings in space. We are learning about our Solar System, our galaxy
and even the stars and galaxies in the wider, great cosmos. We are looking
further and further out into the universe. There are many people, world-wide,
interested in learning about what is out there: astronomers and scientists of
course, but also people such as school science teachers and even fictional film
makers. We see our sun, the stars and galaxies above, and wonder what they
are?” Slowly the Astronomical community from all around the world are giving us
answers and our knowledge is increasing.
We
can now reach to the moon, but can we travel further and land on another,
hospitable planet outside our solar system? Some people think we should leave
earth because of all the damage and pollution we have created here – we need a
new home! The hunt for a new planet to call home” is on!
So
now, looking for habitable planets has become a major activity among certain
groups, and by using telescopes and cameras, people have found thousands of
planets orbiting their suns – but, unfortunately, until now, they all have one
or more drawbacks which makes life on them impossible.
What
are the conditions needed for life to survive, grow and develop? Well, if we
take our planet as an example, it seems a whole range of particular, and
demanding conditions are needed, all occurring simultaneously, as follows:
REQUIREMENTS
FOR LIFE TO SURVIVE AND FLOURISH:
The first
requirement is to find a planet which circulates its host sun in its habitable
zone, the so called Goldilocks Zone” – not too hot, not too cold.
A second
requirement is to find a rocky planet with water – again, not too little
but also not too much, so as to allow some dry land for habitation.
A third
requirement is to find a planet with breathable atmosphere, without poisonous
gases. Our type of life needs enough oxygen and neutral nitrogen with no
poisonous gases mixed in.
A fourth
requirement is that the host sun should not be violent. Most suns are
violent, and some are extremely violent. For example, the current thinking is
that all suns shed their outer layers occasionally. Millions and trillions of
tons of red-hot molten rock are blasted out into space which we call a Nova”.
These cataclysmic occurrences happen to all suns, the frequency ranging
from once a year, to just once in millions of years – we are still studying the
stars, suns in our universe, and learning about how the different types
function.
Also,
we know that all suns occasionally blast out smaller ejections of hot rock and
dust which we call Coronal Mass Ejections (CMEs). These are lesser events but
very dangerous, too, and can damage anything nearby. Our earth has experienced
these and they can, and do, knock out local electric power grids in places.
Luckily for us, our sun is fairly stable and only occasionally flings out large
CMEs, (But look at planet Mercury – the closest to our sun – it has been
thoroughly trashed!) However, our sun has allowed life to form over thousands,
if not millions of years, allowing our development and for us to become
conscious of our world, the Solar system, and now, even the Universe!
The fifth
requirement is protection from all the harmful rays coming from
the sun and also, on occasions,
coming from the cosmos or universe (space). Some planets have a liquid iron
core deep inside. If this rotates it can create a magnetosphere and this will
act as a magnetic shield to ward off those harmful rays. These rays are small
particles of matter, chiefly protons and electrons, but also harmful Gamma
rays.
A sixth
requirement is for a suitable gravity. Our planet has gravity. We don’t know
exactly how this arises, but this should not be too strong, too.
Another,
seventh most helpful feature is that we live on a sphere formed by
tectonic plates. These float on the hot liquid rock below and move around with
the edges grinding and rubbing up against each other. These plate movements
renew land surfaces grown old which also help life to renew and exist. At the
junctions of these plates are volcanos which also spew out lava with bad gases.
Our planet and its surface is impermanent, so providing new rocky landscapes
for life to grow and develop on.
An eighth
requirement is protection from plunging rocks – comets, meteors and, asteroids.
If a planetary system has orbiting rocks or asteroids which may descend and
strike a habitable earth, there needs to be other planets located in suitable
positions which can help shield it from such comets and asteroids.
These
eight rather specific requirements as given above, are for supporting life on
any planet. To find another planet which has all these eight features will be
very difficult. You can get a small feel for the immensity of the task if you
see all these factors lined up to form a probability – a miniscule probability
– but to our delight there are billions and trillions of stars with planets in
orbit, which can give us hope of finding one or even two, benign, kind
environments similar to ours!
And
what if we finally find a planet with attractive life-supporting features –
will we travel there only to find a civilization already in occupation – with
helicopter gunships and drones hunting down escaped prisoners? The more things
change, the more they stay the same”, is the saying.
OUR
PERSPECTIVE:
The
truth is we see our sun as normal: it is our world, it is all we see, after
all. But there are clues that, on the contrary, it is special. Astronomers have
categorized stars. Our sun is a ‘G’ type Dwarf, occurring in 2.7 percent of all
suns. It is unusually quiet. It flares (Novas) rarely, other stars flare more
frequently, and perhaps, a thousand times greater. Could our star be very
special – allowing life to develop over millions of years? Also, we think
we have all the requirements on earth for life to survive – but could there be
alternatives to our form of life?
Our
Earth’s orbit is in our sun’s Goldilocks Zone, and we even have a moon that
stabilizes our rotation. It prevents wild oscillations and gives us gentle
tides. Our Moon is too large to have been captured naturally scientist say.
Also, its rock and materials are different from those of Earth. It is
positioned at the exact distance to fully eclipse the Sun, exactly – an almost impossible,
billions-to-one chance occurrence. Someone has done this.
Our
planet is billions of years old. It has a long and as yet unknown history! We
are not alone in the universe – the moon tells us so!
Do
you think we are alone? 15/12/2020
PH.