That is the title of the cover story in this month’s issue of National Geographic. It points out that in our Universe there are billions and billions of stars, most of which have planets, and that we have had billions of years of time since the Big Bang for the development of life. From findings here on Earth, it appears that life can develop in all kinds of extreme environment, hot and cold, acidic and corrosive, so it is almost a complete certainty that there are plenty of life forms throughout the Universe, at various degree of intelligence advancement. We are not alone. The interesting question is: how do they look like?
In many of the contemporary science fiction books and movies, writers usually depict space visitors (or invaders) in various biological forms, such as that in the form of octopus. In my opinion, our space visitors are likely not so.
Let me explain my reasoning as follows:
Even though in theory there can be an almost infinite ways that life forms can evolve in various parts of the Universe depending on the local environment, two things are certain.
Firstly, no matter in which part of the Universe they come from, their technology must still obey the same physical laws as we do here on Earth. In particular, they cannot have spacecrafts traveling faster than the speed of light. Since star systems are separated by distance measured in light-years, that means space travel will require thousands if not tens of thousands of years. Biological life forms have much shorter life cycles than that due to decay and diseases and so not likely to be able to survive that long journey.
Secondly, if they are able to get on a journey traversing the vast space of Universe to reach us, they must be at a much higher level of technology than we do. This is analogous to the situation when the European explorers came to “visit”” the native America a few hundred years ago. So we should be “looking” into our far future (perhaps thousand years from now) to speculate on how they look like.
Here on Earth, life started randomly from simple biochemical molecules and evolved systematically to form biological creatures with increasing level of intelligence. As technology advances further and further, the intelligence generated in the biological life forms is then transferred to mechanical devices called computers and eventually robots, in the name of Artificial Intelligence. At the present time, we already have smart robots that can simulate many human functions, replacing real human workers. Remember that we are now only several decades since the invention of computers. Imagine several thousands years from now, or perhaps ten of thousands of years from now, the intelligence on Earth will be entirely transferred to machines, and intelligent robots will be able to do everything that human does. On the other hand, human in the form biological lives will gradually decline and be phased out as we have used up all the non-renewable energy resources and have generated enough waste to ruin the whole environment. Intelligence on this planet will then only survive in the “brains” of smart robots, as Earth moves into this new phase of intelligence evolution.
It will be those intelligent machines, which I will call “Physical Lives” that will be our space visitors, not biological ones.
In H. G. Wells” famous space invader book “ The War of the Worlds”, the invading Martians are biological life forms and they have “heat rays” that almost wiped out the human on Earth. It is fortunate that they eventually succumb to the “lowly” germs on earth for which they do not have immunity to. For the Physical Life Forms that I mention above, they are not going to have such a problem with germs, and they will have far more lethal weapons than just “heat rays”.
As to how they look like, here are my speculations based on Physical Life Forms. They will have all the physical devices required for intelligent living, such as two eyes and two ears for stereovision and hearing. They will have noses to detect odors for monitoring the environment and sound emitting devices (like our mouths) for audio communication, in addition to some advanced communication devices based on wireless waves. On the other hand, because they use physical energy such as nuclear power or some even more advanced power system (that we will probably discover in the future), they will not need any of our biological internal organs to process food, air and waste, i.e. no need for lung, heart, liver, stomach, bladder, kidney and guts etc. One thing I am not sure is whether they will still have any sex organs. Physical life forms can reproduce in a much simpler way, so that organ is obsolete. However, I think smart robot designers may still want to keep that for pleasure only. In short they will have a must simpler system to operate and maintain. As a result, they can have extremely long life spans, and that is the reason they can survive the long time travel to come to us.
One last note, it is unlikely that these Physical Life Forms will have any religion because of their super-advanced level of science development that should have cleared away most of the supernatural ideas carried over from the previous biological life forms. However, if they still do, the religion will certainly be different from any of those presently practiced here on Earth. Furthermore, if it so happens that they have preaching in their minds for the visit, it could mean great enlightenment for us people on Earth, but much more likely, it will spell a major disaster for mankind.