There are few encounters between living creatures that would be as severe as those between aliens from a far distant world and ourselves. Of course there have been fictional stories, fictional movies, and even the so-called "non-fiction" writings of people convinced that such an event has already happened. I don't know for sure, of course, but it does seem rather far-fetched to believe such aliens have visited us already.
There are millions of stars within a few thousands of light years of Earth. Most of those stars are able to be home to many planets, and some of those planets might have some conditions which allow life to either evolve from scratch, or to be colonized by preexisting life forms. So the idea that there might be other beings on some planets is not far-fetched at all.
Not all stars would be as homey as our little Sun, which glows pretty much in a stable, medium simmer. Our world benefits greatly from stellar energy from our Sun, but it would not be such a great thing if the Sun were 100 times brighter or larger, or if our orbit was a hundred times closer. Aliens might be imagined to be able to evolve in very extreme conditions compared to our own, yet there seem to be limits where temperatures are measured in thousands of degrees or more, or where the radiation from the star destroys any organic molecule before a life form could ever make use of them.
Plus there is little hope that the laws of physics can be warped in such a way as to prevent space-time and energy relationships from killing any creatures brave enough to attempt a visit to our neighborhood. This presumes that humans in our current state can derive the true laws of physics and the limitations thereof regarding space travel are true. From what I personally know about particle/energy physics, it does seem pretty hopeless to expect anything like "warp speed" or other science fiction concepts. Yet it is not necessarily utterly hopeless. There may be some glaring mistake in our current scientific knowledge which makes our own understanding of physics like that of a small child.
Aliens might have lived for many thousands or millions of years longer than our civilization. It is not a slam dunk, of course, but there are animals on our own planet that have outlived humans by hundreds of millions of years. Plus, if one counts unicellular life forms, then we have been outlived for billions of years. Those simple life forms have not been so successful as humans at technical feats such as reaching the Moon for a short visit and returning alive. Yet, we owe our very lives to the relentless work of those tiny, ancient living things for converting the Earth into a place which can support animals like us. Likewise, there are many other plants and animals upon which we depend for food. This pyramid of life forms is a package deal, without the base at the bottom, there can be no apex supported at the top.
It may be true that humans on Earth are alone in the Galaxy. If this is true, then there is absolutely no hope that we would be visited by any aliens, even if there are such beings on planets around the stars in other galaxies. The closest major galaxy to our own is the Andromeda Galaxy, some million light years away. And most other galaxies are billions of light years away. I am not very keen to spend a billion years in a space ship traveling at light-speed, just to visit a hellish planet where some bacterial or fungal growth has evolved intelligence.
Before jumping to far off galaxies, we would be better off examining our own first. Even within our home galaxy, the Milky Way Spiral, there is a kind of "pleasure zone" or "Goldilocks Effect". where the density of stars is not too high and not too low. We need a dense enough gas presence from which our Sun could be formed (after possibly 1 or more generations of star death.)
We do not need intense amounts of gamma radiation which occurs in denser "boiling" regions of the galaxy where stars are often being swallowed by other stars or where black holes form from heavier and heavier stars.
We would never have evolved on the planets of slow burning small stars that rarely convert their hydrogen fuel into metals and other heavy elements during supernova explosions. That part of the galaxy is more or less "frozen." The elements of life must, at a minimum, involve carbon and hydrogen, and the carbon element is not easily formed without a supermassive star's alchemical fusion death.
So maybe there is a 1/3rd of the galaxy where we could possibly live in, or at least have naturally formed within. Maybe this is true for other beings in the Universe as well. Perhaps the bands can be mapped onto the selection of stars we examine for life signatures. There would be no need to waste telescope time outside of the "life band" of the galaxy. So our efficiency at finding life planets can be multiplied by 3 or more. Other tricks, such as ignoring stars greater than a certain size or temperature, can increase the chances even more. No significant life forms can evolve around a star that can only exist for a few percent of the time that the Sun has existed.
We can only assume that any "real aliens" out there have already discovered such techniques, and perhaps developed greater refinements and much finer tools for the task of finding living planets. That ability would seem to be a evolution technique in itself -- only those beings who can transcend their home planet might survive some life-ending catastrophe that planets often suffer. If the aliens cannot transcend their dying world, they will die along with it.
Aliens could possibly visit our planet -- using "magic" of course -- but only at very great expense. Unless aliens find some manner of using absolutely limitless and costless energy, then any trips from one part of the galaxy to another will require vast cost. For instance, traveling in a 10 ton spacecraft (hopefully enough food, water and fuel for the trip) from the Sun to Alpha Centauri at the speed of light would cost far more than all the energy we have used since the birth of humanity.
Tricks like sucking up waste hydrogen that atomically zips around through otherwise empty space might help save costs. We would only need to take food and water. If we were satisfied only sending some robots, then the costs could be reduced even more, expelling the need for food and water, however still needing some kind of power sources for the robots. Yet, even after reducing everything down to the minimum, the energy costs would be quite high, far higher than all our currently accumulated space launchings combined. Just communicating with these robots would be difficult, since, while traveling at light speed, they would be like photons themselves, reducing the signals to ultra-low frequency grunts, and while stopped in orbit around the target star, the time for a signal to reach us from that star would take many years.
Worm holes, hyperdrives and other exotic science-fiction concepts might someday become possible, or at least less fantastic, and this would mean that not only us, but the aliens, could benefit. In fact, the aliens may have already discovered such truths.
There are millions of stars within a few thousands of light years of Earth. Most of those stars are able to be home to many planets, and some of those planets might have some conditions which allow life to either evolve from scratch, or to be colonized by preexisting life forms. So the idea that there might be other beings on some planets is not far-fetched at all.
Not all stars would be as homey as our little Sun, which glows pretty much in a stable, medium simmer. Our world benefits greatly from stellar energy from our Sun, but it would not be such a great thing if the Sun were 100 times brighter or larger, or if our orbit was a hundred times closer. Aliens might be imagined to be able to evolve in very extreme conditions compared to our own, yet there seem to be limits where temperatures are measured in thousands of degrees or more, or where the radiation from the star destroys any organic molecule before a life form could ever make use of them.
Plus there is little hope that the laws of physics can be warped in such a way as to prevent space-time and energy relationships from killing any creatures brave enough to attempt a visit to our neighborhood. This presumes that humans in our current state can derive the true laws of physics and the limitations thereof regarding space travel are true. From what I personally know about particle/energy physics, it does seem pretty hopeless to expect anything like "warp speed" or other science fiction concepts. Yet it is not necessarily utterly hopeless. There may be some glaring mistake in our current scientific knowledge which makes our own understanding of physics like that of a small child.
Aliens might have lived for many thousands or millions of years longer than our civilization. It is not a slam dunk, of course, but there are animals on our own planet that have outlived humans by hundreds of millions of years. Plus, if one counts unicellular life forms, then we have been outlived for billions of years. Those simple life forms have not been so successful as humans at technical feats such as reaching the Moon for a short visit and returning alive. Yet, we owe our very lives to the relentless work of those tiny, ancient living things for converting the Earth into a place which can support animals like us. Likewise, there are many other plants and animals upon which we depend for food. This pyramid of life forms is a package deal, without the base at the bottom, there can be no apex supported at the top.
It may be true that humans on Earth are alone in the Galaxy. If this is true, then there is absolutely no hope that we would be visited by any aliens, even if there are such beings on planets around the stars in other galaxies. The closest major galaxy to our own is the Andromeda Galaxy, some million light years away. And most other galaxies are billions of light years away. I am not very keen to spend a billion years in a space ship traveling at light-speed, just to visit a hellish planet where some bacterial or fungal growth has evolved intelligence.
Before jumping to far off galaxies, we would be better off examining our own first. Even within our home galaxy, the Milky Way Spiral, there is a kind of "pleasure zone" or "Goldilocks Effect". where the density of stars is not too high and not too low. We need a dense enough gas presence from which our Sun could be formed (after possibly 1 or more generations of star death.)
We do not need intense amounts of gamma radiation which occurs in denser "boiling" regions of the galaxy where stars are often being swallowed by other stars or where black holes form from heavier and heavier stars.
We would never have evolved on the planets of slow burning small stars that rarely convert their hydrogen fuel into metals and other heavy elements during supernova explosions. That part of the galaxy is more or less "frozen." The elements of life must, at a minimum, involve carbon and hydrogen, and the carbon element is not easily formed without a supermassive star's alchemical fusion death.
So maybe there is a 1/3rd of the galaxy where we could possibly live in, or at least have naturally formed within. Maybe this is true for other beings in the Universe as well. Perhaps the bands can be mapped onto the selection of stars we examine for life signatures. There would be no need to waste telescope time outside of the "life band" of the galaxy. So our efficiency at finding life planets can be multiplied by 3 or more. Other tricks, such as ignoring stars greater than a certain size or temperature, can increase the chances even more. No significant life forms can evolve around a star that can only exist for a few percent of the time that the Sun has existed.
We can only assume that any "real aliens" out there have already discovered such techniques, and perhaps developed greater refinements and much finer tools for the task of finding living planets. That ability would seem to be a evolution technique in itself -- only those beings who can transcend their home planet might survive some life-ending catastrophe that planets often suffer. If the aliens cannot transcend their dying world, they will die along with it.
Aliens could possibly visit our planet -- using "magic" of course -- but only at very great expense. Unless aliens find some manner of using absolutely limitless and costless energy, then any trips from one part of the galaxy to another will require vast cost. For instance, traveling in a 10 ton spacecraft (hopefully enough food, water and fuel for the trip) from the Sun to Alpha Centauri at the speed of light would cost far more than all the energy we have used since the birth of humanity.
Tricks like sucking up waste hydrogen that atomically zips around through otherwise empty space might help save costs. We would only need to take food and water. If we were satisfied only sending some robots, then the costs could be reduced even more, expelling the need for food and water, however still needing some kind of power sources for the robots. Yet, even after reducing everything down to the minimum, the energy costs would be quite high, far higher than all our currently accumulated space launchings combined. Just communicating with these robots would be difficult, since, while traveling at light speed, they would be like photons themselves, reducing the signals to ultra-low frequency grunts, and while stopped in orbit around the target star, the time for a signal to reach us from that star would take many years.
Worm holes, hyperdrives and other exotic science-fiction concepts might someday become possible, or at least less fantastic, and this would mean that not only us, but the aliens, could benefit. In fact, the aliens may have already discovered such truths.
