something fun
The below passage is from "100 Things You Didn't Know You Didn't Know" by John D. Barrow
excellent excellent
Is cosmology on a slippery slope towards science fiction? New satellite observations of the cosmic microwave background radiation, the echo of the Big Bang, have backed most physicists' favourite theory of how the Universe developed. This may not be entirely good news.
The favoured model contains many apparent 'coincidences that allow the Universe to support complexity and life. If we were to consider the 'multiverse' of all possible universes, then ours is special in many ways. Modern quantum physics even provide ways in which these possible universes that make up the multiverse of all possibilities can actually exist.
Once you take seriously the suggestion that all possible universes can (or do) exist then you also have to deal with another, rather strange consequence. In this infinite array of universes there will exist technical civilisations, far more advanced than ourselves, that have the capability to simulate universes. Instead of merely simulating their weather or the formation of galaxies, as we do, they would be able to go further and study the formation of stars and planetary systems. Then, having added the rules of biochemistry to their astronomical simulations, they would be able to watch the evolution of life and consciousness within their computer simulations (all speeded up to occur on whatever timescale was convenient for them). Just as we watch the life cycles of fruit flies, they would be able to follow the evolution of life, watch civilisations grow and communicate with each other, even watch them argue about whether there existed a Great Programmer in the Sky who created their Universe and who could intervene at will in defiance of the laws of Nature they habitually observed.
Within these universes, self-conscious entities can emerge and communicate with one another. Once that capability is achieved, fake universes will proliferate and will soon greatly outnumber the real ones. The simulators determine the laws that govern these artificial worlds; they can engineer fine-tunings that help the evolution of the forms of life they like. And so we end up with a scenario where, statistically, we are more likely to be in a simulated reality than a real one because there are far more simulated realities than real ones.
The physicist Paul Davies has recently suggested that this high probability of our living in a simulated reality is a reductio ad absurdum for the whole idea of a multiverse of all possibilities. But, faced with this scenario, is there any way to find out the truth? There may be, if we look closely enough.
For a start, the simulators will have been tempted to avoid the complexity of using a consistent set of laws of Nature in their worlds when they can simply patch in 'realistic' effects. When the Disney company makes a film that features the reflection of light from the surface of a lake it does not use the laws of quantum electrodynamics and optics to compute the light scattering. That would require a stupendous amount of computing power and detail. Instead, the simulation of the lifht scattering is replaced by plausible rules of thumb that are much briefer than the real thing but give a realistic looking result- as long as no one looks too closely. There would be an economic and practical imperative for simulated realities to stay that way if they were purely for entertainment. But such limitations to the complexity of the simulation's programming would presumably cause occasional tell-tale problems- and perhaps they would even be visible from within.
Even if the simulators were scrupulous about simulating the laws of Nature, there would be limits to what they could do. Assuming the simulators, or at least the early generations of them, have a very advanced knowledge of the laws of Nature, it's likely they would still have incomplete knowledge of them (some philosophies of science would argue this must always be the case). They may know a lot about the physics and programming needed to simulate a universe, but there will be gaps or, worse still, errors in their knowledge of the laws of Nature. They would, of course, be subtle and far from obvious to us, otherwise our 'advanced' civilisation wouldn't be advanced. These lacunae do not prevent simulations being created and running smoothly for long periods of time, but gradually the little flaws will begin to add up.
Eventually, their effects would snowball and these realities would cease to compute. The only escape is if their creators intervene to patch up the problems one by one as they arise. This is a solution that will be very familiar to the owner of any home computer who receives regular updates in order to protect it against new assaults by viruses or to repair gaps that its original creators had not foreseen. The creators of a simulation could offer this type of temporary protection, updating the working laws of Nature to include extra things they had learned since the simulation initiated.
In this kind of simulation, logical contradictions will inevitably arise and the laws in the simulations will appear to break down occasionally. The inhabitants of the simulation- especially the simulated scientists- will occasionally be puzzled by the observations they make. The simulated astronomers might, for instance, make observations that show that their so-called constants of Nature are very slowly changing.
It's likely there could even be sudden glitches in the laws that govern these simulated realities. That's because the simulators would most likely use a technique that has been found effective in all other simulations of complex systems: the use of error-correcting codes to put things back on track.
Tkae our genetic code, for example. If it were left to its own devices we would not last very long. Errors would accumulate and death and mutation would quickly ensue. We are protected from this by the existence of a mechanism for error correction that identifies and corrects mistakes in genetic coding. Many of our complex computer systems possess the same type of internal immune system to guard against error accumulation.
If the simulators used error-correcting computer codes to guard against the fallibility of their simulations as a whole (as well as simulating them on a smaller scale in our genetic code), then every so often a correction would take place to that state or the laws governing the simulation. Mysterious changes would occur that would appear to contravene the very laws of Nature that the simulated scientists were in the habit of observing and predicting.
So it seems enticing to conclude that, if we live in a simulated reality, we should expect to come across occasional 'glitches' or experimental results that we can't repeat or even very slow drifts in the supposed constants and laws of Nature that we can't explain.
excellent excellent
Is cosmology on a slippery slope towards science fiction? New satellite observations of the cosmic microwave background radiation, the echo of the Big Bang, have backed most physicists' favourite theory of how the Universe developed. This may not be entirely good news.
The favoured model contains many apparent 'coincidences that allow the Universe to support complexity and life. If we were to consider the 'multiverse' of all possible universes, then ours is special in many ways. Modern quantum physics even provide ways in which these possible universes that make up the multiverse of all possibilities can actually exist.
Once you take seriously the suggestion that all possible universes can (or do) exist then you also have to deal with another, rather strange consequence. In this infinite array of universes there will exist technical civilisations, far more advanced than ourselves, that have the capability to simulate universes. Instead of merely simulating their weather or the formation of galaxies, as we do, they would be able to go further and study the formation of stars and planetary systems. Then, having added the rules of biochemistry to their astronomical simulations, they would be able to watch the evolution of life and consciousness within their computer simulations (all speeded up to occur on whatever timescale was convenient for them). Just as we watch the life cycles of fruit flies, they would be able to follow the evolution of life, watch civilisations grow and communicate with each other, even watch them argue about whether there existed a Great Programmer in the Sky who created their Universe and who could intervene at will in defiance of the laws of Nature they habitually observed.
Within these universes, self-conscious entities can emerge and communicate with one another. Once that capability is achieved, fake universes will proliferate and will soon greatly outnumber the real ones. The simulators determine the laws that govern these artificial worlds; they can engineer fine-tunings that help the evolution of the forms of life they like. And so we end up with a scenario where, statistically, we are more likely to be in a simulated reality than a real one because there are far more simulated realities than real ones.
The physicist Paul Davies has recently suggested that this high probability of our living in a simulated reality is a reductio ad absurdum for the whole idea of a multiverse of all possibilities. But, faced with this scenario, is there any way to find out the truth? There may be, if we look closely enough.
For a start, the simulators will have been tempted to avoid the complexity of using a consistent set of laws of Nature in their worlds when they can simply patch in 'realistic' effects. When the Disney company makes a film that features the reflection of light from the surface of a lake it does not use the laws of quantum electrodynamics and optics to compute the light scattering. That would require a stupendous amount of computing power and detail. Instead, the simulation of the lifht scattering is replaced by plausible rules of thumb that are much briefer than the real thing but give a realistic looking result- as long as no one looks too closely. There would be an economic and practical imperative for simulated realities to stay that way if they were purely for entertainment. But such limitations to the complexity of the simulation's programming would presumably cause occasional tell-tale problems- and perhaps they would even be visible from within.
Even if the simulators were scrupulous about simulating the laws of Nature, there would be limits to what they could do. Assuming the simulators, or at least the early generations of them, have a very advanced knowledge of the laws of Nature, it's likely they would still have incomplete knowledge of them (some philosophies of science would argue this must always be the case). They may know a lot about the physics and programming needed to simulate a universe, but there will be gaps or, worse still, errors in their knowledge of the laws of Nature. They would, of course, be subtle and far from obvious to us, otherwise our 'advanced' civilisation wouldn't be advanced. These lacunae do not prevent simulations being created and running smoothly for long periods of time, but gradually the little flaws will begin to add up.
Eventually, their effects would snowball and these realities would cease to compute. The only escape is if their creators intervene to patch up the problems one by one as they arise. This is a solution that will be very familiar to the owner of any home computer who receives regular updates in order to protect it against new assaults by viruses or to repair gaps that its original creators had not foreseen. The creators of a simulation could offer this type of temporary protection, updating the working laws of Nature to include extra things they had learned since the simulation initiated.
In this kind of simulation, logical contradictions will inevitably arise and the laws in the simulations will appear to break down occasionally. The inhabitants of the simulation- especially the simulated scientists- will occasionally be puzzled by the observations they make. The simulated astronomers might, for instance, make observations that show that their so-called constants of Nature are very slowly changing.
It's likely there could even be sudden glitches in the laws that govern these simulated realities. That's because the simulators would most likely use a technique that has been found effective in all other simulations of complex systems: the use of error-correcting codes to put things back on track.
Tkae our genetic code, for example. If it were left to its own devices we would not last very long. Errors would accumulate and death and mutation would quickly ensue. We are protected from this by the existence of a mechanism for error correction that identifies and corrects mistakes in genetic coding. Many of our complex computer systems possess the same type of internal immune system to guard against error accumulation.
If the simulators used error-correcting computer codes to guard against the fallibility of their simulations as a whole (as well as simulating them on a smaller scale in our genetic code), then every so often a correction would take place to that state or the laws governing the simulation. Mysterious changes would occur that would appear to contravene the very laws of Nature that the simulated scientists were in the habit of observing and predicting.
So it seems enticing to conclude that, if we live in a simulated reality, we should expect to come across occasional 'glitches' or experimental results that we can't repeat or even very slow drifts in the supposed constants and laws of Nature that we can't explain.