You are unique, aren't you? There never has been a person exactly like you before, there isn't now, and there never will be. Maybe! Depending on what's really real in all things cosmological, the odds that there are identical copies of you out there can range from plausible if improbable, to plausible and probable, to in fact near certainty, even certainty. The key issue revolves around the concept of infinity, or near infinity. If one has an infinite number of universes to play around with, and/or infinite time, then every possible history is, sooner or later, somewhere, compulsory.
The idea of a duplicate you or two or three isn't that farfetched. Even on Planet Earth, this tiny speck within the cosmos, you have had, do have, and will have doppelgangers. But those are just look-alikes, not actual duplicates of you down to the nittiest-grittiest detail.
From the outset, some definitions are in order. We have the 'observable universe' which is that part of the entire Universe we can actually see in the here and now. Parts of the Universe that exist, but which light hasn't yet reached us, aren't part of our 'observable universe' - yet. The 'Universe' is all that we can ever know about, regions seen, and regions as yet unseen. Then there is the 'Multiverse' which, if it exists, are a conglomerate of separate Universes, each of which exists as a discrete entity in a three dimensional arena and which we could potentially interact with. Think of separate houses along a street you can visit in turn as separate universes. An overall analogy could be the nucleus part of a liver cell (our 'observable universe'), the entire cell (the Universe), and the grand collection of liver cells - the liver Multiverse as it were. Apart from those, there are parallel (mirror/shadow/alternate) universes which 'exist' - for lack of a better phrase - in other planes of existence and like houses that exist in a time instead of a special sequence, say on the same block of land, one can't easily travel from one to another. There's also the Many Worlds Interpretation variation of parallel universe, and simulated universes.
Firstly, could there be another you or multiple copies of you in the existing Universe? That's plausible, but probably unlikely.
Discussion: The existing Universe could be as near to infinite as makes no odds. It obviously can't be infinite, because it would take an infinite amount of time to expand the Universe to an infinite volume, and we know the Big Bang took place less than 14 billion years ago. And, the Universe can't contain an infinite amount of stuff; otherwise it would have to have an infinite volume to house it all. The fact that our night sky is dark, suggests that there can't be an infinite number of stars and galaxies in our observable universe, otherwise, no matter in which direction you looked, you'd see a star or galaxy and the night sky would be as light as the daytime. However, from our point of view, while not infinite, the Universe is still BIG! And it does contain a lot of stuff. It is within the bounds of possibility that within such a vast space, by chance, there could be a duplicate(s) of you, even more identical to you than any identical terrestrial twin you might happen to have. The odds aren't very high to be honest, but they aren't zero. However, even if an identical copy of you exists elsewhere out there, the probability is far greater that they already have, or someday will. The odds that two copies of you exist right now multiply the odds against by many orders of magnitude. Finally, even if another copy of you exists somewhere out there now, they are in all probability way to far away for the both of you to ever shake hands.
Secondly, could there be another you or multiple copies of you in a cyclic Universe? That's not only plausible, it borders on near certainty.
Discussion: Current cosmological observations suggest that our Universe began some 13.7 billion years ago in a Big Bang. Alas, the expansion of our Universe appears not only not slowing down, but ever accelerating due to something cosmologists and astrophysicists are calling dark energy - which they admit they don't really understand. Anyway, despite dark energy, many cosmologists cling to the concept that eventually the expansion will slow down, halt, and reverse, resulting in ultimately a Big Crunch billions of years in the future. That Big Crunch leads directly to another Big Bang - expansion - contraction - Big Crunch - Big Bang, etc., etc. Thus one has an ever oscillating or cyclic Universe with no beginning and no end. Ah, the concept of infinity (this case in time) rears its head. Since the Universe has already gone through an infinite number of these cycles, as surely as night follows day follows night, anything that could have happened, has happened, and happened an infinite number of times. That includes in infinite number of you, and the life your leading now right down to the last detail an infinite number of times, as well as leading differing lives in every possible variation from the major (marriage, career, children, lifespan, etc.) through to the relatively minor, right down to the highly trivial (like an infinite number of lifetimes absolutely identical to the current one except for one morning when you had an ever so slightly different breakfast cereal). Just think, somewhere in the infinite past, there was a version of you who lived an entire lifetime driving a car and never hit a red light! Again, anything that is within the realm of possibility, even if improbable in the extreme, has happened, and has happened again an infinite number of times. Such is the nature of infinity. The other nice thing about an infinite Universe (whether in time or space) is that all those unsuccessful eggs and sperm, all those failed or un-germinated seeds, all those spores and pollen that never bore fruit, all those lives that never were, all now get their moment in the sun!
There's an interesting variation on the above theme. Most of us are probably familiar with the sci-fi idea of being caught in a time-loop. You repeat an interval of time over again and again, probably until some weird sense of deja vu alerts you that something's not quite right. Expand the idea to the grandest scale possible. Big Bang - expansion - contraction - Big Crunch - Big Bang - expansion, etc. but each cycle isn't a new cycle with a new history and new possibilities rather each cycle is absolutely identical to the one that came before, and the one before that, etc. So, there will be an endless number of you, but there will be no wild new things in your lives, just the same old life, again and again. Maybe that's where we get our now and again sense of deja vu from.
Of course in a cyclic universe, one universe dies before the next is born, so a copy of you in a previous universe is kaput before your universe comes into being, and you will be kaput before the next cycle starts, so there's no meeting of identically like minds.
Thirdly, could there be another you or multiple copies of you in the Multiverse? That's not only plausible, but much more likely than if only our one Universe exists.
Discussion: We live in a Universe that is very friendly to life-as-we-know-it (life-not-as-we-know-it is another can of worms that need not concern us here). That is, it seems that the various physical laws and physical constants are fine tuned to allow our kind of life. If any of those values were slightly greater or slightly lesser, the biophysics and biochemistry that allow organic life forms to exist wouldn't be possible. For example, if gravity were ever so slightly weaker, atoms/molecules wouldn't coalesce into macro-bodies like galaxies and stars and planets. If gravity were ever so slightly stronger, stars would be far more massive on average, and the more massive a star, the shorter it's lifespan, to the point where there wouldn't be enough time for life in a young solar system to develop before the parent star went poof! So, that fine tuning leads to a trio of possibilities.
The first is that we (meaning the Universe's life forms) are just incredibly lucky that our one and only Universe just happened to meet all the Goldilocks criteria that allow us to exist. The second is that there is indeed, an intelligent designer responsible for those conditions. For want of a better word, let's call this intelligent designer "God". (There's an interesting variation on this theme and that is this Universe was created by an extraterrestrial intelligence in another Universe, a feat which might be relativity simple to a highly advanced technology able to manipulate the basic forces of physics.)
The third possibility is that there is a Multiverse. We can all agree that our Universe is a Goldilocks universe. We can also all agree that we can imagine other universes, while superficially akin to ours (it would at least have space and time), have differing values for some of all of the physical properties we associate with ours - differing values for the physical constants, the types and numbers of physical forces and particles, the physical laws that are part and parcel of physics, etc. It's akin to humans - we're all superficially similar, yet each one of us (past, present and future) is unique (even identical twins differ and the same applies to clones as well as nurture affects us as well as nature). So, like we have a multiverse of humans, we could have a multiverse of universes (the Multiverse), some of which, like ours, will be Goldilocks universes, although most won't be because some critical constant(s) or force(s) or particle(s) or law(s) will be different enough not to allow the complexity we associate with life-as-we-know-it.
In other words, there exist dozens, hundreds, thousands, hundreds of thousands, maybe multi-millions or billions (or more) of universes where the physical laws and constants may well be different. That being the case, most universes will be barren of life because their physics, hence chemistry, aren't compatible with life-as-we-know-it. But a few, by chance, will be Goldilocks Universes. It wouldn't surprise anyone that because we exist, our Universe must be a Goldilocks Universe.
How exactly a Multiverse would come about is neither here or there. But there is at least one theory. To help explain various observational cosmological anomalies that would follow a traditional Big Bang, several decades ago the idea was floated that immediately following the Big Bang came a period of ultra-rapid inflation, before the expansion settled down to a far slower rate. Today, inflation is widely accepted as part and parcel of the Big Bang model. However, inflation need not have ceased at the exact same nanosecond everywhere. That is, if inflation continued on at one point, another Universe would quickly form, and if inflation didn't shut down exactly at the same moment, another bubble or pocket or baby universe would bud off, and so on and so on, resulting in a sort of bubble/foam collective of universes - the Multiverse.
The upshot is that lots of universes (a Multiverse), could mean a lot of you! However, distances separating the various copies of you are now even vaster, so again, getting together for dinner and drinks isn't possible.
Fourthly, could there be another you or multiple copies of you in Parallel Universe(s)? It's plausible, but perhaps not all that probable.
Discussion: We've all seen various sci-fi shows where our heroes get propelled into some sort of parallel or mirror universe. The characters they meet are close to, but not identical to themselves. The history they encounter is similar to, but not identical to the history they know. Of course that's for the sake of the plot. A parallel universe could easily contain a parallel you. Unfortunately, sci-fi aside, while there's theoretical reasons to postulate parallel universes, there's no known way of getting to them (and therefore no way of meeting yourself - assuming another yourself exists). But like in the Multiverse concept, if there are multi-billions of parallel universes, that increases the odds of a duplicate you.
Fifthly, could there be another you or multiple copies of you in the 'Many Worlds Interpretation' of quantum physics? That's taken as given!
Discussion: There is a theory known as the Many Worlds Interpretation of quantum physics that each time anything, from fundamental particle to human being, comes to a fork in the road as it were, and has to make a choice(s), both/all forks are taken (something can be, and not be at the same time). To accommodate both/all alternatives, this quantum decision making (in the case of the micro), or macro decision making (in the case of scales we're familiar with), the entire Universe splits, and where we had one Universe, we now have two (or more), one for each fork. Of course when you consider the number of forks that the Universe encounters, well it's been calculated that every second, some 10 to the 100th power of Universes need to be created. (Just think how many hundreds, perhaps thousands of decisions (usually quite trivial, often subconsciously) you make every day. There has to be a new Universe to accommodate every alternative. Of course that means that when you add up all these collected Universes, there must be a lot of you, and a lot of everything else, each one ever so subtly different. In the case of deciding between wearing a green dress or a red dress there are now two Universes - one with you in a green dress; one with you in a red dress. And as in the case of parallel universes, there's no known, even theoretical, way of getting from this (say green dress) one to say another one of them (say red dress) and thus exchanging greetings with your identical self or selves.
Lastly, could there be another you or multiple copies of you as a Simulation? That too is as close to certainty as makes no odds!
Discussion: Do you exist? I mean really, really exist and have a physical reality? That's a pretty dumb question you'll probably ask! The answer is an obvious 'yes'. But, what if I were to suggest that the odds are very high that you have no actual physical reality, and that I have no actual physical reality, and that in fact all terrestrial life, Planet Earth, perhaps the entire observable universe has no actual physical reality! In other words, what if we are a computer simulation!
Let's suppose, for argument's sake, that in the real physical Universe, there exists some tens of thousands of extraterrestrial civilizations which have evolved technology our equal or better; even more advanced than we can conceive of. The odds are high that most would have invented computers - hardware and software. Any one civilization, such as our own, have (to date) produced multi-thousands of computer programs, many of which simulate life forms - think of the hundreds, indeed thousands of computer or video games. No doubt these programs will grow, over time, ever more complex and lifelike until they simulate reality to the same degree as reality itself.
If one advanced civilization produces multi-thousands of individual computer programs that simulate an actual, or imagined, reality, what are the odds that we aren't one of those simulated thousands vis-à-vis being that advanced civilization that actually exists in real reality? How could you know if you were real (hardware), or imaginary (software)? I maintain there's no way of you knowing, at least for absolute sure.
There's only a relatively few actual civilizations, but untold numbers of created false (simulated) realities - what odds we are one of the real ones and not one of the imaginary/simulated many?
Perhaps our concept of 'God' is nothing more than a mythological version of some advanced, but hardly supernatural, extraterrestrial computer programmer! Now as long as nobody hits the delete key!
But of course if there are multiple copies of that computer program containing you then that equates to a lot of you! You could exist hundreds, thousands, hundreds of thousands of times over, all leading perhaps identical, but more likely as not, similar 'lives'. Now you quite obviously could not meet yourself as each piece of software is akin to a one universe - the collection of all the units of that software is akin to a type of multiverse!
Is the idea really so way out in left field that there's not a snowball's chance in hell that it could be right? We have to look to advances in our own terrestrial computing power to determine that. Computer generated simulations are already realistic enough that they are used to train pilots and MDs and other humans in professional activities where mistakes in training, if done in real situations, could be disastrous. Our cinema industry has already produced computer generated virtual reality films, bypassing real actors and real scenery. It's entirely possible to bring back in a sense dead actors to star again in new productions. We've all be awed by computer generated special effects in films that are so realistic that if you didn't actually know better, you'd swear they were real.
Walk into any DVD store and you'll find thousands of video (computer) games and/or simulations that you can run on your PC. Most have 'humans' in various role-playing guises that are software generated and which you interact with. The reality factor is increasing by leaps and bounds. At what point will the software become complex enough such that these simulated 'beings' are advanced enough to have self-awareness? What happens when the computer software programming these virtual 'humans' becomes equal to the software (brains) that program us? What happens when the computer software complexity exceeds that of the human brain? Far fetched? Methinks not. Now just replace our virtual 'humans' with ourselves, and maybe, just maybe, we're the virtual reality in somebody (something) else's actual reality.
That theory is testable. While I can think of no way to prove I'm not a simulated being, one can find evidence that we do live in a simulated universe, and by implication, we too are simulated beings. No software (computer or human wetware - brains) is perfect. If there are any glitches, or software upgrades, they might be detectable as anomalous phenomena in some context or another. Like say one of the physical constants were tweaked and altered ever so slightly (and there is some evidence for that - the fine structure constant for example or the proton-electron mass ratio has apparently changed over astronomical time periods), or say the expansion of the Universe began to accelerate for no real apparent reason (that sounds familiar - recall dark energy). Computer software - from our experience - is always being upgraded and updated. If the same applies elsewhere, we could perhaps notice it if we're a product of that software.
Even though there could be multiple copies of a video game that contains you as a character, it's one you per copy, so again, no meeting yourself. That's not to prevent the creator of the game from including multiple copies of you within the one game - if so; well a conversation between you and copies of you won't be very interesting since you each know what you're going to say before you say it!
Finally, one bright note is evident. Even as you approach your own demise, take heart and rejoice, for somewhere out there, there is another you(s) to carry on, and on, and on, and on, and on! As the sun (once upon a time) never set on the British Empire, so to will the sun never set on you.
By the by, if you want to split hairs, you could insist that any copies of you aren't really identical in that the elementary particles, atoms and molecules making up your twin aren't the same elementary particles, atoms and molecules making you up. The flaw in that argument is that all fundamental particles, like say all electrons, are identical to as many decimal places as you care to measure and calculate.
The idea of a duplicate you or two or three isn't that farfetched. Even on Planet Earth, this tiny speck within the cosmos, you have had, do have, and will have doppelgangers. But those are just look-alikes, not actual duplicates of you down to the nittiest-grittiest detail.
From the outset, some definitions are in order. We have the 'observable universe' which is that part of the entire Universe we can actually see in the here and now. Parts of the Universe that exist, but which light hasn't yet reached us, aren't part of our 'observable universe' - yet. The 'Universe' is all that we can ever know about, regions seen, and regions as yet unseen. Then there is the 'Multiverse' which, if it exists, are a conglomerate of separate Universes, each of which exists as a discrete entity in a three dimensional arena and which we could potentially interact with. Think of separate houses along a street you can visit in turn as separate universes. An overall analogy could be the nucleus part of a liver cell (our 'observable universe'), the entire cell (the Universe), and the grand collection of liver cells - the liver Multiverse as it were. Apart from those, there are parallel (mirror/shadow/alternate) universes which 'exist' - for lack of a better phrase - in other planes of existence and like houses that exist in a time instead of a special sequence, say on the same block of land, one can't easily travel from one to another. There's also the Many Worlds Interpretation variation of parallel universe, and simulated universes.
Firstly, could there be another you or multiple copies of you in the existing Universe? That's plausible, but probably unlikely.
Discussion: The existing Universe could be as near to infinite as makes no odds. It obviously can't be infinite, because it would take an infinite amount of time to expand the Universe to an infinite volume, and we know the Big Bang took place less than 14 billion years ago. And, the Universe can't contain an infinite amount of stuff; otherwise it would have to have an infinite volume to house it all. The fact that our night sky is dark, suggests that there can't be an infinite number of stars and galaxies in our observable universe, otherwise, no matter in which direction you looked, you'd see a star or galaxy and the night sky would be as light as the daytime. However, from our point of view, while not infinite, the Universe is still BIG! And it does contain a lot of stuff. It is within the bounds of possibility that within such a vast space, by chance, there could be a duplicate(s) of you, even more identical to you than any identical terrestrial twin you might happen to have. The odds aren't very high to be honest, but they aren't zero. However, even if an identical copy of you exists elsewhere out there, the probability is far greater that they already have, or someday will. The odds that two copies of you exist right now multiply the odds against by many orders of magnitude. Finally, even if another copy of you exists somewhere out there now, they are in all probability way to far away for the both of you to ever shake hands.
Secondly, could there be another you or multiple copies of you in a cyclic Universe? That's not only plausible, it borders on near certainty.
Discussion: Current cosmological observations suggest that our Universe began some 13.7 billion years ago in a Big Bang. Alas, the expansion of our Universe appears not only not slowing down, but ever accelerating due to something cosmologists and astrophysicists are calling dark energy - which they admit they don't really understand. Anyway, despite dark energy, many cosmologists cling to the concept that eventually the expansion will slow down, halt, and reverse, resulting in ultimately a Big Crunch billions of years in the future. That Big Crunch leads directly to another Big Bang - expansion - contraction - Big Crunch - Big Bang, etc., etc. Thus one has an ever oscillating or cyclic Universe with no beginning and no end. Ah, the concept of infinity (this case in time) rears its head. Since the Universe has already gone through an infinite number of these cycles, as surely as night follows day follows night, anything that could have happened, has happened, and happened an infinite number of times. That includes in infinite number of you, and the life your leading now right down to the last detail an infinite number of times, as well as leading differing lives in every possible variation from the major (marriage, career, children, lifespan, etc.) through to the relatively minor, right down to the highly trivial (like an infinite number of lifetimes absolutely identical to the current one except for one morning when you had an ever so slightly different breakfast cereal). Just think, somewhere in the infinite past, there was a version of you who lived an entire lifetime driving a car and never hit a red light! Again, anything that is within the realm of possibility, even if improbable in the extreme, has happened, and has happened again an infinite number of times. Such is the nature of infinity. The other nice thing about an infinite Universe (whether in time or space) is that all those unsuccessful eggs and sperm, all those failed or un-germinated seeds, all those spores and pollen that never bore fruit, all those lives that never were, all now get their moment in the sun!
There's an interesting variation on the above theme. Most of us are probably familiar with the sci-fi idea of being caught in a time-loop. You repeat an interval of time over again and again, probably until some weird sense of deja vu alerts you that something's not quite right. Expand the idea to the grandest scale possible. Big Bang - expansion - contraction - Big Crunch - Big Bang - expansion, etc. but each cycle isn't a new cycle with a new history and new possibilities rather each cycle is absolutely identical to the one that came before, and the one before that, etc. So, there will be an endless number of you, but there will be no wild new things in your lives, just the same old life, again and again. Maybe that's where we get our now and again sense of deja vu from.
Of course in a cyclic universe, one universe dies before the next is born, so a copy of you in a previous universe is kaput before your universe comes into being, and you will be kaput before the next cycle starts, so there's no meeting of identically like minds.
Thirdly, could there be another you or multiple copies of you in the Multiverse? That's not only plausible, but much more likely than if only our one Universe exists.
Discussion: We live in a Universe that is very friendly to life-as-we-know-it (life-not-as-we-know-it is another can of worms that need not concern us here). That is, it seems that the various physical laws and physical constants are fine tuned to allow our kind of life. If any of those values were slightly greater or slightly lesser, the biophysics and biochemistry that allow organic life forms to exist wouldn't be possible. For example, if gravity were ever so slightly weaker, atoms/molecules wouldn't coalesce into macro-bodies like galaxies and stars and planets. If gravity were ever so slightly stronger, stars would be far more massive on average, and the more massive a star, the shorter it's lifespan, to the point where there wouldn't be enough time for life in a young solar system to develop before the parent star went poof! So, that fine tuning leads to a trio of possibilities.
The first is that we (meaning the Universe's life forms) are just incredibly lucky that our one and only Universe just happened to meet all the Goldilocks criteria that allow us to exist. The second is that there is indeed, an intelligent designer responsible for those conditions. For want of a better word, let's call this intelligent designer "God". (There's an interesting variation on this theme and that is this Universe was created by an extraterrestrial intelligence in another Universe, a feat which might be relativity simple to a highly advanced technology able to manipulate the basic forces of physics.)
The third possibility is that there is a Multiverse. We can all agree that our Universe is a Goldilocks universe. We can also all agree that we can imagine other universes, while superficially akin to ours (it would at least have space and time), have differing values for some of all of the physical properties we associate with ours - differing values for the physical constants, the types and numbers of physical forces and particles, the physical laws that are part and parcel of physics, etc. It's akin to humans - we're all superficially similar, yet each one of us (past, present and future) is unique (even identical twins differ and the same applies to clones as well as nurture affects us as well as nature). So, like we have a multiverse of humans, we could have a multiverse of universes (the Multiverse), some of which, like ours, will be Goldilocks universes, although most won't be because some critical constant(s) or force(s) or particle(s) or law(s) will be different enough not to allow the complexity we associate with life-as-we-know-it.
In other words, there exist dozens, hundreds, thousands, hundreds of thousands, maybe multi-millions or billions (or more) of universes where the physical laws and constants may well be different. That being the case, most universes will be barren of life because their physics, hence chemistry, aren't compatible with life-as-we-know-it. But a few, by chance, will be Goldilocks Universes. It wouldn't surprise anyone that because we exist, our Universe must be a Goldilocks Universe.
How exactly a Multiverse would come about is neither here or there. But there is at least one theory. To help explain various observational cosmological anomalies that would follow a traditional Big Bang, several decades ago the idea was floated that immediately following the Big Bang came a period of ultra-rapid inflation, before the expansion settled down to a far slower rate. Today, inflation is widely accepted as part and parcel of the Big Bang model. However, inflation need not have ceased at the exact same nanosecond everywhere. That is, if inflation continued on at one point, another Universe would quickly form, and if inflation didn't shut down exactly at the same moment, another bubble or pocket or baby universe would bud off, and so on and so on, resulting in a sort of bubble/foam collective of universes - the Multiverse.
The upshot is that lots of universes (a Multiverse), could mean a lot of you! However, distances separating the various copies of you are now even vaster, so again, getting together for dinner and drinks isn't possible.
Fourthly, could there be another you or multiple copies of you in Parallel Universe(s)? It's plausible, but perhaps not all that probable.
Discussion: We've all seen various sci-fi shows where our heroes get propelled into some sort of parallel or mirror universe. The characters they meet are close to, but not identical to themselves. The history they encounter is similar to, but not identical to the history they know. Of course that's for the sake of the plot. A parallel universe could easily contain a parallel you. Unfortunately, sci-fi aside, while there's theoretical reasons to postulate parallel universes, there's no known way of getting to them (and therefore no way of meeting yourself - assuming another yourself exists). But like in the Multiverse concept, if there are multi-billions of parallel universes, that increases the odds of a duplicate you.
Fifthly, could there be another you or multiple copies of you in the 'Many Worlds Interpretation' of quantum physics? That's taken as given!
Discussion: There is a theory known as the Many Worlds Interpretation of quantum physics that each time anything, from fundamental particle to human being, comes to a fork in the road as it were, and has to make a choice(s), both/all forks are taken (something can be, and not be at the same time). To accommodate both/all alternatives, this quantum decision making (in the case of the micro), or macro decision making (in the case of scales we're familiar with), the entire Universe splits, and where we had one Universe, we now have two (or more), one for each fork. Of course when you consider the number of forks that the Universe encounters, well it's been calculated that every second, some 10 to the 100th power of Universes need to be created. (Just think how many hundreds, perhaps thousands of decisions (usually quite trivial, often subconsciously) you make every day. There has to be a new Universe to accommodate every alternative. Of course that means that when you add up all these collected Universes, there must be a lot of you, and a lot of everything else, each one ever so subtly different. In the case of deciding between wearing a green dress or a red dress there are now two Universes - one with you in a green dress; one with you in a red dress. And as in the case of parallel universes, there's no known, even theoretical, way of getting from this (say green dress) one to say another one of them (say red dress) and thus exchanging greetings with your identical self or selves.
Lastly, could there be another you or multiple copies of you as a Simulation? That too is as close to certainty as makes no odds!
Discussion: Do you exist? I mean really, really exist and have a physical reality? That's a pretty dumb question you'll probably ask! The answer is an obvious 'yes'. But, what if I were to suggest that the odds are very high that you have no actual physical reality, and that I have no actual physical reality, and that in fact all terrestrial life, Planet Earth, perhaps the entire observable universe has no actual physical reality! In other words, what if we are a computer simulation!
Let's suppose, for argument's sake, that in the real physical Universe, there exists some tens of thousands of extraterrestrial civilizations which have evolved technology our equal or better; even more advanced than we can conceive of. The odds are high that most would have invented computers - hardware and software. Any one civilization, such as our own, have (to date) produced multi-thousands of computer programs, many of which simulate life forms - think of the hundreds, indeed thousands of computer or video games. No doubt these programs will grow, over time, ever more complex and lifelike until they simulate reality to the same degree as reality itself.
If one advanced civilization produces multi-thousands of individual computer programs that simulate an actual, or imagined, reality, what are the odds that we aren't one of those simulated thousands vis-à-vis being that advanced civilization that actually exists in real reality? How could you know if you were real (hardware), or imaginary (software)? I maintain there's no way of you knowing, at least for absolute sure.
There's only a relatively few actual civilizations, but untold numbers of created false (simulated) realities - what odds we are one of the real ones and not one of the imaginary/simulated many?
Perhaps our concept of 'God' is nothing more than a mythological version of some advanced, but hardly supernatural, extraterrestrial computer programmer! Now as long as nobody hits the delete key!
But of course if there are multiple copies of that computer program containing you then that equates to a lot of you! You could exist hundreds, thousands, hundreds of thousands of times over, all leading perhaps identical, but more likely as not, similar 'lives'. Now you quite obviously could not meet yourself as each piece of software is akin to a one universe - the collection of all the units of that software is akin to a type of multiverse!
Is the idea really so way out in left field that there's not a snowball's chance in hell that it could be right? We have to look to advances in our own terrestrial computing power to determine that. Computer generated simulations are already realistic enough that they are used to train pilots and MDs and other humans in professional activities where mistakes in training, if done in real situations, could be disastrous. Our cinema industry has already produced computer generated virtual reality films, bypassing real actors and real scenery. It's entirely possible to bring back in a sense dead actors to star again in new productions. We've all be awed by computer generated special effects in films that are so realistic that if you didn't actually know better, you'd swear they were real.
Walk into any DVD store and you'll find thousands of video (computer) games and/or simulations that you can run on your PC. Most have 'humans' in various role-playing guises that are software generated and which you interact with. The reality factor is increasing by leaps and bounds. At what point will the software become complex enough such that these simulated 'beings' are advanced enough to have self-awareness? What happens when the computer software programming these virtual 'humans' becomes equal to the software (brains) that program us? What happens when the computer software complexity exceeds that of the human brain? Far fetched? Methinks not. Now just replace our virtual 'humans' with ourselves, and maybe, just maybe, we're the virtual reality in somebody (something) else's actual reality.
That theory is testable. While I can think of no way to prove I'm not a simulated being, one can find evidence that we do live in a simulated universe, and by implication, we too are simulated beings. No software (computer or human wetware - brains) is perfect. If there are any glitches, or software upgrades, they might be detectable as anomalous phenomena in some context or another. Like say one of the physical constants were tweaked and altered ever so slightly (and there is some evidence for that - the fine structure constant for example or the proton-electron mass ratio has apparently changed over astronomical time periods), or say the expansion of the Universe began to accelerate for no real apparent reason (that sounds familiar - recall dark energy). Computer software - from our experience - is always being upgraded and updated. If the same applies elsewhere, we could perhaps notice it if we're a product of that software.
Even though there could be multiple copies of a video game that contains you as a character, it's one you per copy, so again, no meeting yourself. That's not to prevent the creator of the game from including multiple copies of you within the one game - if so; well a conversation between you and copies of you won't be very interesting since you each know what you're going to say before you say it!
Finally, one bright note is evident. Even as you approach your own demise, take heart and rejoice, for somewhere out there, there is another you(s) to carry on, and on, and on, and on, and on! As the sun (once upon a time) never set on the British Empire, so to will the sun never set on you.
By the by, if you want to split hairs, you could insist that any copies of you aren't really identical in that the elementary particles, atoms and molecules making up your twin aren't the same elementary particles, atoms and molecules making you up. The flaw in that argument is that all fundamental particles, like say all electrons, are identical to as many decimal places as you care to measure and calculate.
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