This text is an excerpt from Are the Planets Inhabited? By E. Walter Maunders, F.R.A.S. Harper & Brothers London and New York. Available from the Gutenberg Project available at: http://www.gutenberg.org/files/35937/35937-h/35937-h.htm
Is there Life on Other Worlds?
In the beginning there were...Questions.
The first thought that people had about stars was an obvious one: they were lights. There was a greater light to rule the day; a lesser light to rule the night; and there were the stars also.
Next Came Comparisons.
In those days there seemed to be a huge difference between Earth and the stars that shone in the sky. The earth was large, dark, and unmoving, while the stars were small, bright, and seemed to travel. The earth was seen as the fixed center of the universe, although the Copernican theory later disproved that idea.
Read more about the Copernican System hereWe slowly came to the understanding that Earth shares characteristics with other planets.
These similarities are:- Movement
- Shining by reflecting the light of the sun
- Placement in the galaxy
- Appearance from far away
These similarities caused people to wonder if other planets shared Earth's hospitality for life.
What Does "Life" On Other Planets Mean?
As people began comparing Earth to other planets, they began to ask: "Since our planet looks like a star from far away, are the 'stars' we see other planets similar to our own?" People began to wonder if there were other people on other planets doing the same thing they were doing: looking up into the night sky, wondering about other worlds.
About sixty years ago, the idea of a Plurality of Worlds caused a lot of excitement and controversy. The idea has stuck with us ever since. The Plurality of Worlds is the desire to discover alien life forms similar to our own: intelligent beings with corporeal bodies. That is what we mean when we speak of a world being "inhabited." We want more than to discover oceans full of fish on Jupiter, or moss on the moon. We can't speak of other planets being "inhabited" if they're host to animals or vegetation. The most interest we could glean from such planets would be the interest as to whether or not intelligent life might eventually develop.
Space Exploration Must Be Measurable.
We can't hope to discover disembodied intelligences because we would have no way to study them, or prove their existence. We couldn't confirm or deny the idea of spirits or intelligences in the Moon or the Sun, because we would have no way of determining their existence.
Examples of Things We Don't Know Enough About to Study:- Gnomes
- Elves
- Fairies
- Anything beyond sight or touch
The only way we could regard another planet as being inhabited would be if we discovered the following attributes in alien creatures:
- Intelligence
- Physical Form
Can aliens and religion coexist?
Sixty years ago, Dr. Whewell and Sir David Brewster came up with a metaphysical and theological idea regarding life on other planets that was framed by religious ideas. These men developed the idea that God must have made other life forms to inhabit all the wonderful planets he created. If no life existed on these planets, then their very existence would be a waste. So, again, when Dr. A. R. Wallace revived the discussion in 1903, he clearly had a theological purpose in his opening paper, though he was taking the opposite view from that held by Brewster half a century earlier.
Personally, I don't think there's any theological significance to solving the question of life on other planets. If there are many inhabited planets, only a few inhabited planets, or no other planets other than our own that contains beings like us, I don't see how that knowledge would change our religious beliefs. For example: explorers have made their way across the Antarctic continent to the South Pole but have found no “inhabitant” there. Does this have any theological significance? And if this is true of places on Earth, why should it be different with regard to the continents of another planet?
The real question.
The problem therefore seems not to be theological or metaphysical, but purely physical. We can simply ask of each planet we review: “Are its physical conditions, so far as we can tell, capable of supporting life?” The question is not at all as to how life is generated on a world, but as to whether, if once in action on a particular world, its activities could be carried on.
You can't have life without a hospitable environment.
A hospitable environment is a world where living organisms can exist that are comparable in intelligence with men.
We aren't worried about how life first came into existence on any inhabited planet. It is enough that we know that life does exist; and in whatsoever way it was first generated here, in that same way we may consider that it could have been generated on another planet.
Looking for intelligent life.
Right now we don't have to worry about lines between organic and organic substances, or the differences between plants and animals. These are important subjects for discussion, but they do not affect us here, for we are only concerned with the highest form of organism, the one furthest from these two dividing lines.
If we can tell the physical condition of a planet, we can know whether or not life could be supported there.
Living organism defined.
What is a living organism? A living organism may change its substance, but its identity will remain essentially the same. This is only a partial definiton, but it gives a general idea. Small details of a living organism can change without losing the essence of the whole. A good analogy for a living organism would be a river: the river may appear to be unchanged although its water molecules are constantly changing. There is something more in the living organism than the continuity of the whole, with the change of the details.
Read: 12 characteristics of living organismsfurther analogies
The flame and the butterfly (by Max Verworn)
Life is like a flame. Imagine a gas flame with its distinctive butterfly shape. The flame remains constant, and above the burner, at the base of the flame, there is a completely dark space. Surounding this space is a bluish zone that gives off faint light, and beyond the bluish zone, the bright spread of the two "wings" of flame. This flame, like the river, keeps its form even though the gasses taht feed it are constantly changing. There is not only a change of material in the flame, there is a change of condition. Everywhere the gas from the burner is entering inot the energetic combination with the oxygen of the air, with evolution of light and heat. There is change in the constituent particles as well as change of the constituent particles; there is more than the mere flux of material through the form; there is change of the material, and in the process of that change energy is developed.
The steam engine
A steam-engine may afford us a third illustration. Here fresh material is continually being introduced into the engine there to suffer change. Part is supplied as fuel to the fire there to maintain the temperature of the engine; so far the illustration is analogous to that of the gas flame. But the engine carries us a step further, for part of the material supplied to it is water, which is converted into steam by the heat of the fire, and from the expansion of the steam the energy sought from the machine is derived. Here again we have change in the material with development of energy; but there is not only work done in the subject, there is work done by it. But the living organism differs from artificial machines in that, of itself and by itself, it is [Pg 9]continuously drawing into itself non-living matter, converting it into an integral part of the organism, and so endowing it with the qualities of life. And from this non-living matter it derives fresh energy for the carrying on of the life of the organism.