A real alien, what could it look like? The question may seem stupid to some people because to them, the answer is very clear. An alien has a big head with big bulgy eyes, green skin, small legs and arms- to summarize- the picture of a really monstrous creature. This is how aliens are often represented in science-fiction films too. There is in fact a possibility that such an alien race exists in the universe. Scientists are really thinking about the idea seriously.
The appearance of a space creature can really vary. It depends on many factors, but to visualize the basic appearance of an alien, we should take into consideration the 'universal laws'. According to what we know, these laws are applicable to everything in the universe. One of the 'universal laws' says that everywhere life must begin the same way, so the beginning of life on another planet must have the same factors as how life begun on Earth.
Let's look at these 'common factors' to define the basic alien being.
Matter
Matter is everything around us. The trees outside , water, books, computers, rubbish- absolutely everything is matter. It consists of very small particles called molecules which in turn consist of atoms, invisible to the naked eye and even with a simple laboratory microscope. To see an atom, you need a really powerful microscope. By making studies, scientists have found that atoms also do exist on other planets and stars. In fact, only 100 types of atoms exist in the whole universe.
Carbon
Carbon is among the most important element for the existence of life. Although carbon molecules are quite small, they are only the molecules which can join up other molecules like in a long chain. Thus carbon can create many types of molecules. A life-form is made up of hundreds and hundreds of different molecules, being so complex. Only carbon atoms are able to make so many types of molecules to do all the jobs of the body.
Dynamic
DNA
The DNA tissue is most probably the most important molecule in the universe. DNA stands for 'deoxyribonucleic acid' (can you say it? :-) ). It is what make up our genes. Genes are responsible for hereditary characteristics in a person. They are the base itself of the foundation of living things. Nowadays most scientists agree that the DNA structure is unique for all beings, which means that practically all life forms must have DNA tissues. However it may happen that an alien race can live without genes but that's very unlikely.
If DNA is the only molecules which can form living things, then it surely must exist on an alien planet. And for life forms to exist, their environment should be just right; water should be present and the temperature should be neither too cold nor too hot.
All animals cells need oxygen. If the aliens have anything like animal cells, they must live in an atmosphere containing oxygen. All these factors can give us a a few hints about how aliens might look like.
Obvious characteristics of aliens
An alien must breathe, so it must have some kind of organ that acts like the
lungs in our system.
It must have a king of liquid like blood which feeds its cells. It also
needs a heart to pump the liquid.
If the alien happens to be an intelligent being, then its brain may be quite
large enough for a central nervous system. Even animals on Earth have
that.
It must have something like a head which encloses the brain for
protection.
The alien must have sense organs to enable it to see where it is going, smell
and hear. It needs ears, eyes and a nose, even if these may not be quite
like ours.
Finally, to hold things and to move around, it must have limbs like we have arms
and legs. Nevertheless, he may have more two arms, even eight ones such as
the eight tentacles of an octopus on Earth.
You surely must have noticed that an alien can have many things in common with us. However, it is not necessary that it may look just like us. Its shape may quite surprise you if one day you happen to meet one.
If you have read the 'Obvious characteristics of aliens' then you must surely have realized that many types of aliens featured in science-fiction films are mostly unlikely. We'll take some examples:-
1) The blob or slime
The blob has some sort of green slimy jelly as body, with its eyes and a big mouth as one. It has small hands and no feet at all. To move around, it just kind of crawl.
You see, the blob has quite a big problem. It doesn't have a neck. A neck is very efficient. It helps us to see behind us and to shake our head without having to move our entire body. Not having one is not very comfortable and practical.
2) The 'half human-half reptile' alien
Probably you have at least once see this type of alien in a sci-fi film. The 'half human-half reptile' alien is one with some characteristics, like a lizard head and a human body. In fact, it's like two creatures have got mixed up together. Really, it is scary and if you were like Dana Scully from the 'X-files' series, you would agree that the possibility of this type of alien is unscientific. This has more to do with sci-fi films directors than reality.