Most people seem to agree there is intelligent life in the universe. We are of course limited to our relative observations, speculations and philosophies with the scientific data on ET intelligent life on any scale truly being zero and our reach into even the Milky Way Galaxy being so tiny. The obvious and most astounding barriers for interstellar travel, exploration, and conquest, as we know them, are technology and the size of the observable universe, with respect to distance and time. Let’s investigate from our perspectives what might be realistic reasoning for another civilization of ET species to make contact.
Technology and advancement of civilization as can be imagined is most likely the basis of how far into space might be traveled, for how long, and why. First, intelligent life must develop and advance sufficiently to where technology is feasible to allow interstellar travel. We have to pose the critical question: why would any civilization begin conquests into space?
Stars have cycles. Stars are formed in clouds of gas and dust, known as nebulae. Nuclear reactions at the center or core of stars provides energy to make them shine brightly for long periods of time. The lifetime of stars is important and is based a lot on the size and mass of the star. Massive stars burn their fuel faster than smaller stars and may last only in the hundreds of thousands of years, while smaller stars can shine brightly for billions of years through nuclear reactions. As the stars age and burn their hydrogen they will expand, cool and change color to become red giants. Smaller stars will undergo a slower transition to death, passing through the planetary nebulae stage as a low mass star towards the end of its life as a red giant. The star will become unstable and pulsate, the outer layers ejected by resulting stellar winds. As the outer layers drift away, the core becomes very bright and hot, which is now the white dwarf stage. White dwarfs no longer experience nuclear reactions and instead utilize thermal storage of energy for all heat and light. Over time this radiates way and the star eventually in theory will become a black dwarf, no longer emitting significant heat or light. The time it takes for a white dwarf to reach this stage is calculated to be longer than the age of the universe, however, so we don’t know of any black dwarf stars at this point. Larger mass stars will experience a violent and very energetic death cycle, a supernova, an explosion scattering their remains across the cosmos. As the star runs out of nuclear fuel, the outer layers collapse into the core and explode out, resulting in an ultra-compact core called a neutron star, or possibly a black hole if the star is truly massive. The materials leftover from supernovas may scatter about nearby clouds of gas and dust and lead to new star formation.
Star cycles clearly show evidence that, intelligent life as we know it, cannot be sustained at one place in the universe indefinitely. Although the time frame is vast, eventually an advanced intelligent civilization must move on and conquest space for the survival of the species, settling on ET habitats such as other celestial bodies such as planets or moons. If the technology is advanced enough, a civilization or species may have other reasons to explore space besides the life cycle of a star. The home planet or moon of an ET civilization may run low on resources viable to sustain such a civilization, therefore seeking resources in space may be required to make interstellar moves.
The possible reasons for interstellar exploration most likely relate to survival of the species, resources to sustain the species, and finally, advancement sufficient enough for general and intentional interstellar conquest. These are the primary reasons that we may come into contact with intelligent ET life, not considering worm holes, parallel universes, parallel dimensions or some other sort of existential planes we don’t understand.
Perhaps specific precious resources to a particular species are limited in the universe in such a way that an ET civilization will explore into space specifically for that resource, be it some element, elements, or combination of. Perhaps finding habitable planets or moons is challenging to the point they are extremely difficult to find for particular ET intelligent species, few and far between over the vast distances in space. It seems we would be hard pressed to find another habitable planet anywhere near our solar system after all. Perhaps a species advances to the point of interstellar conquest for the sake of conquest. What can we imagine would be the point? Well, from our perspectives we can only look to the reason as seeking knowledge of the universe. What is there really to explore then? Indeed, the most significant reason for interstellar conquest outside of resource retrieval or habitation would be to make contact with and study other forms of life and intelligent life in the universe. I absolutely believe that if there is intelligent life navigating the cosmos, planet earth and its life would be of major significance, as would any and all signs of intelligent life.
A common theme in this type of discussion is the thought that advanced civilizations wouldn’t care about our planet or life or resources. The significance of finding any intelligent ET life for any intelligent ET species capable of interstellar travel, would likely be profound and astronomical at best, worthwhile of further inquiry at worst. As soon as Earth is discovered by an intelligent ET species, it’s probable that we would be of importance, for many reasons, similar to how the aspect of us finding other life, no matter how intelligent, is vastly important to us. Some basic reasons being philosophical, scientific, medicinal and technological.
There is always an emphasis on the size of the universe and the time (as we understand it) to travel across galaxies and to other galaxies that is difficult to comprehend. Without the advancement ourselves to any sort of near speed of light travel, and without any true contact with another intelligent ET life yet, it only leaves us to our imaginations. Considering this, we can only imagine other intelligent life and advancements of technology by such life, yet should not rule out the possibility that this planet is already of import to ET civilization(s), or that contact, either direct or indirect, has already been made in the past or is continuous for some other reason.
Personally the historical and contemporary 2nd hand evidence is not enough for me to be confident that this is already the case, as I think true belief in such a subjective topic at this time can only be based on personal experience. But it’s definitely reasonable to believe that it could be happening, now, or that it has in the past, or that at some age or time it will happen in the future. It’s really a matter of chance and time. Whether our species will be here for that is an unknown, as we race towards technological advancements and continue our own efforts to seek more knowledge in the cosmos, will be beat the clock and survive long enough to find out?