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 (-273^o)  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.