(2) the end of the universe, (A) big expansion and cool down to nothing, (B) no more expansion and cool down to nothing, (C) contraction back to another big bang, (D) something else very different?
This question is far more philisophical than anything. Personally I subscribe to Camus' Absurdism[1] -- that our yearning for meaning and purpose is ironic given how uncaring and lacking in meaning our universe is.
> (2) the end of the universe
There are several theories[2], but from my understanding we need to better understand "dark matter" and "dark energy" (scare quotes because those names are really silly, since we know effectively nothing about either).
In particular, it appears that we live in a flat universe but the evolution of the universe becomes more complicated with the cosmological constant terms in the evolution equations (believed to correspond to dark energy). Effectively, the cosmological constant can be seen as an energy density that remains constant throughout the universe which means that the amount of dark energy increases as the universe expands. I believe we discussed the current theories in my second-year cosmology course, but I can't recall the conclusion (it wasn't taught very well).
But I don't understand how the question "what is the purpose of X" can be anything but philosophical. Science is primarily concerned with creating models of reality and testing the predictive power of those models. The "purpose" of something is not really a meaningful concept in that context.
... unless by "purpose" you mean cause? As in, what caused our universe to exist? That is also not really a meaningful question, because time began with our universe so it's not clear what the concept of "before our universe" actually would refer to. Physically, I believe the currently popular theory is that the progenitor for our universe was an anti-matter explosion caused by the spontaneous creation of a matter+anti-matter pair (which happens all the time in a perfect vacuum due to Heisenberg's uncertainty relation -- \Delta E \Delta t \ge \hbar/2). There are several unsolved problems with this theory, the biggest one being how does it explain that there is a clear imbalance between the amount of matter and anti-matter in our universe.
> But I don't understand how the question "what is the purpose of X" can be anything but philosophical.
Again, my guess is that this depends on how much we know. Or, there about has to be a purpose. And eventually as we learn more there should be some clues about what that purpose is. So I'm wondering if we know that much yet?
A first little clue is the speed of light speed limit that so far seems to say that we are quite isolated from the rest of the universe. So, somehow having us isolated was deliberate. Then, what might be the purpose of having us so isolated?
Then there's the 3 K background radiation. That's one heck of a clue. What might be the reason for giving us such data? To answer, what can we do with it? If we note what we can do with the 3 K data and that seems really special, e.g., we wouldn't be able to do that without the 3 K data, then what is so special we can do with the 3 K data might be a clue for the purpose of letting us have that data.
There's the Heisenberg uncertainty principle. So, it keeps us from being as in an 1890 view of physics, mechanistic. We are stopped at that level by some dice rolling. So, why? When we see how that stops us, we might get a clue of a purpose.
All of that is very thin stuff, but maybe we are on the way to discovering enough to start to conclude what the purpose is.
One point is our existence and our abilities: First cut, how the heck to look at the basic physics and guess the chemistry, then, especially the biology, and, astounding, how the biology developed into us. That's some amazing laws of physics that let that happen, maybe ensured that it would happen. So, what the heck is the purpose of us being here, our existing? That is, we're the most special and amazing thing we know of in the universe. So, if there is a purpose, then it looks like we are a key part of it. So, just what the heck might be what we are to do with our abilities to understand the universe? Then, do we get a hint of the purpose from what we can do? That is, is the purpose the special stuff we can, or will be able, to do? For that if we look ahead, just how much might we be able to do? Build Dyson spheres? Okay, then what would that enable?
We don't see other planets flashing light signals at us from
their Dyson spheres. So, why not? Sure: There are other, better forms of long distance communications, and every planet with a Dyson sphere knows this. So, soon we should discover this better means of communications. So, where the heck to look for those better means. Then when we find them, what would that enable us to do in the universe that would be special? Communicate only? Or both communicate and travel? Or, if long distance travel is possible, then why ever bother to travel; just send robots and have them send back the communications so we can view it. Then does that communications give us a clue about a purpose; that is, suppose we could send robots and they would communicate back; what might we discover that begins to suggest a purpose.
Or, generally, as a meta argument, if we find some things that look really, really special that finally, with our development, we can do that seem to impact, explain, discover, reveal the universe, then maybe our doing that is the purpose of the universe.
I fully agree this is very thin stuff. Still I have to suspect that as we learn more, maybe 1 million years from now, we will begin to guess at a purpose.
Or, if there is no purpose, then this is one heck of a big show for nothing!
> Or, if there is no purpose, then this is one heck of a big show for nothing!
It isn't really. The universe all falls out of a very few, very simple rules playing themselves out - and the more we study it the smaller and simpler that set of basic rules is. Physically it's pretty big, sure, but the Kolgomorov Complexity is actually pretty small, and that's the kind of measure you need to use when considering how good a given explanation is.
Kolmogorov complexity isn't directly related to physics (and I would argue it also falls into philosophy in this case), but what GP was saying is that the complexity of the universe far exceeds the complexity of the laws that govern it. So really the laws of physics are very simple if you consider how complicated the systems they produce are.
You can fit the laws that govern the entirety of particle physics on a single page. Add another quarter-page for general relativity and you have all of the laws required to run our universe (on paper).
Why does there have to be a purpose? The rest of your post is discussing philosophy, but I'll indulge anyway.
> A first little clue is the speed of light speed limit that so far seems to say that we are quite isolated from the rest of the universe. So, somehow having us isolated was deliberate.
What makes you think it was deliberate? The derivation of the speed of light comes directly from Maxwell's equations (which just describe how electric and magnetic fields interact).
Relativity further extends that idea by "simply" noticing that the propagation of light can only work if the waves travel at the speed of light relative to the observer. Thus all light must be travelling at the same speed no matter the speed of the observer, which gives you the entirety of special relativity (that predicts that no information can propagate faster than the speed of light).
I'm not sure which part of the above you could claim is deliberate. We live in a local universe (it takes time for information to travel) and thus light must have a speed. It doesn't actually matter what the speed of light is, the same derivation would apply as long as the speed is finite. Are you saying that the fact that our universe is local is deliberate?
> Then there's the 3 K background radiation. That's one heck of a clue. What might be the reason for giving us such data?
What makes you think it's data? It's literally just the echo of the big bang and comes from the random thermal motion in the "early days" of the big bang. The reason it's 3K is that it has been cooling since the big bang and that's the temperature it happens to be today. If it were any other temperature, would that also be a clue?
> There's the Heisenberg uncertainty principle. [...] We are stopped at that level by some dice rolling.
Quantum mechanics isn't dice rolling. It is true that there cannot be a local hidden-variables theory of QM, but QM still has incredible predictive power when discussing the probabilities of experiments. It is possible in the future that a non-probabilistic view of QM will emerge, it just cannot be both hidden-variables and local.
> So, what the heck is the purpose of us being here, our existing? That is, we're the most special and amazing thing we know of in the universe.
If ants could think, they would probably think they're the most amazing thing they know of in the universe. The only reason we think we're so amazing is because we have no competitor to compare to.
> Or, if there is no purpose, then this is one heck of a big show for nothing!
I don't think that life has an intrinsic purpose. In particular, it personally feels very selfish to claim that my existence is somehow meaningful to something as enormous as the universe. It just feels like unjustified hubris.
I'm trying not to be philosophical and wondering if by now we have enough data so that we can talk about purpose without being philosophical. Sure, that we have that much data now is a long shot!
> What makes you think it was deliberate?
It looks like it might be a deliberate case of our being denied information that might let us see behind the curtain, that is, see more of how the universe is working.
> (that predicts that no information can propagate faster than the speed of light).
How we get from special relativity to that, I want to check out in detail.
Also there is the EPR "spooky action at a distance". Sure, the usual statement is that this does not permit communications faster than the speed of light, but I've seen no careful, detailed argument and want to check this out.
Also, for what I started with, a photon through a beam splitter, the wave function then in two parts, and then later the wave function parts separated by some large distance, if we have photo detectors for each part of the wave function, then the usual argument/assumption is that at most one detector will get a signal from that photon. So, instantly, across light years, the other half of the wave function is destroyed. But in principle we could detect when the detector got a signal because the other half of the wave function would suddenly not exist and would not have its effect on gravity. We're talking the gravity of half a wave function of a photon; right, small. But in principle ....
> Quantum mechanics isn't dice rolling. It is true that there cannot be a local hidden-variables theory of QM, but QM still has incredible predictive power when discussing the probabilities of experiments.
Two high energy photons cross paths, there at the same
time. Maybe they generate an electron-positron pair, and maybe they don't. That's a roll of the dice.
> It is possible in the future that a non-probabilistic view of QM will emerge, it just cannot be both hidden-variables and local.
I saw the Bell's inequality part of the MIT introductory QM lectures. After that lecture, I wanted to see a much, much more careful presentation. Yes, yes, yes, I've heard what 99% of the physics community believes; I took more than enough physics to see how such beliefs are passed out. What I want to know is what the heck the truth is, including about far out possibilities, and for that at least I want the arguments, and the math, about the old stuff, solid.
> If ants could think, they would probably think they're the most amazing thing they know of in the universe. The only reason we think we're so amazing is because we have no competitor to compare to.
Not quite the "only" thing: We have axiomatic set theory as our foundation of math, and there we have pushed hard on its rough edges, e.g., what is decidable. Likely ET can't do better.
Then building on set theory, we have math, and just from the Whitehead-Russell stuff we know how that can be verified by just mechanical means, e.g., just symbol substitution. And we know that some new results can be obtained also just by mechanical means. And I have to doubt that ET can do better in the framework -- for specific math results, sure, ET can be 1 million years ahead of us.
So, basically, we seem to know how solid reasoning goes. I'm guessing that ET can't do better on the techniques of solid reasoning, that is, ET can come up with terrific theorems we have not found yet but is still limited to the same framework I just outlined.
And, ET will have seen all our basic physics and will have to agree with at least 99% of it, no matter how sloppy the MIT QM course is. ET can't disagree with that 99%. For that part of physics, we and ET are in agreement.
So, in some fundamental ways, at least the frameworks, methods, paradigms, we are about as good as there can be.
That's some of why we look special.
And it's some of why we seem to be approaching limits on what we or ET can know about the universe. So, if there is a purpose, then we are seeing about all the evidence there can be about what that purpose might be.
So far, we don't see a purpose. But I was asking if there is some more info that lets us start to guess a purpose?
> The reason it's 3K is that it has been cooling since the big bang and that's the temperature it happens to be today. If it were any other temperature, would that also be a clue?
My point about the 3 K radiation is not that it is not 2 K (as apparently eventually it will be) or 4 K (as apparently it once was) but that it is to us for photons a wall we can't see past. Also the timing is curious: 3 K is darned cold, and it took some astounding detectors to study it; in some years, the temperature will be 2 K, 1 K, etc., and need still more astounding detectors. So, at 3 K, we've come along at about the right time. When big, seemingly independent things agree in time, it looks suspicious. So, we have to suspect that the wall was deliberate. I'm willing to set that guess aside because people are talking about seeing gravitational waves from before the time of the origin of the 3 K radiation -- so the 3 K radiation is only partly a wall. And by analyzing the 3 K radiation, e.g., taking the spacial power spectrum and understanding the acoustic aspects, maybe we can get some clues about before that radiation.
Still, to me, that there is this wall of 3 K radiation, in surprising senses uniform, is one heck of a situation. I'm not, but some people got all wound up and called it the face of God! If there is a purpose, maybe from the shockingly surprising 3 K radiation we can get a clue. Uh, maybe shocking conclusions, e.g., a purpose, need shocking data so that from shocking data maybe we should look for shocking conclusions, e.g., a purpose!
Alright, I'm just going to focus on the physics in your comment.
> How we get from special relativity to that, I want to check out in detail.
It's a fairly trivial derivation once you get past the fact that Newtonian mechanics doesn't work at relativistic speeds (the big insight Einstein had was his conviction that Maxwell was correct and Newton was wrong). You do it in second-year physics courses (at least, that's when I did it). You can even do it intuitively. If light always propagates at c, no matter what speed you're travelling at, then the Lorentz transformations are the only way that different reference frames are able to agree on measurements.
> Also there is the EPR "spooky action at a distance". Sure, the usual statement is that this does not permit communications faster than the speed of light
To be fair, this is actually quite hard to wrap your head around. There are definitely papers on the topic if you want to read them, but the effective reason why you cannot communicate using entangled particles is related to the distinction between the phase and group velocities. A phase velocity can be faster than the speed of light, but it carries no information (without also knowing other properties of the wave which travel slower than the speed of light). The orientation of the two particles is (effectively) their relative phase but you can't actually communicate information using it.
> Maybe they generate an electron-positron pair, and maybe they don't. That's a roll of the dice.
Again, currently we do not have a way of predicting the outcome of an individual experiment, but there's no reason to believe that we will never be able to do so.
> We have axiomatic set theory as our foundation of math
... which gives us Godel's incompleteness theorem. Maybe ET has a far more sophisticated basis of mathematics that doesn't permit Godel. I don't know, but it's a bit odd to claim that axiomatic set theory is somehow the holy grail (it has its own problems such as the requirement of the Axiom of Choice).
> Still, to me, that there is this wall of 3 K radiation, in surprising senses uniform, is one heck of a situation.
We know why that happened though, it's because of inflation.
For EPR, as I understand it from my too crude reading, there is an event and two particles are created and fly off in different, maybe from conservation of momentum, opposite directions. So, the two particles are a QM system with one wave function which, however, is in two parts that are separating rapidly.
As I understand the usual interpretation of the wave function, there is no, say, definite spin. We don't know what the spin of either particle is, and neither does the wave function or anything else. That is, a definite value of the spin just doesn't exist yet.
Then we measure the spin of one of the particles, and that measurement gives us a spin that apparently was determined just at our measurement. Then the wave function of the two particles has to change, and the other particle has its wave function but if we measure its spin we will get what we are supposed to, say, opposite, from what we measured from the first particle. So, the fixing of the spin of the particle we measure second was somehow transmitted faster than the speed of light. Just what was transmitted faster than the speed of light we don't know about, can't detect, and is not physics in any usual sense. Still, say, if we were trying to write a computer program to simulate this, as soon as the first measurement was made, we'd have to stop the simulation clock of the universe, go the other particle, on the simulation clock, infinitely fast, fix that particle's spin, and then continue the simulation. Strange stuff.
But, sure, that doesn't tell us how to do communications with EPR "spooky action at a distance".
I don't yet know enough QM to make well informed questions about more. I should watch the MIT QM course lectures through to the end (hold my nose on how he does his math) and pick out the more important things they are saying about how wave functions behave, when there are interactions and the wave functions disappear, etc.
Yes, pretty much need to assume the axiom of choice, and some of its consequences are tough to swallow.
> Again, currently we do not have a way of predicting the outcome of an individual experiment, but there's no reason to believe that we will never be able to do so.
Right. So, if we could so predict, what surprising things could we do with that? So, we are being forbidden to do such things. Why? Does this provide a clue about purpose?
Right, this is a long way from physics at least now.
For why SR says that information cannot be transmitted faster than light, IIRC what you said about the Lorentz transformations can say that just information, of any kind, sent any way, known to current physics or not, would permit a case of time travel or seeing into the future or some such, and we don't want to believe in that.
Yes, there is physics, say, the standard model, and first cut it looks quite simple. But the consequences are astounding beyond belief. E.g., we couldn't look at the standard model and see how DNA would work and what it would do, for green plants, earth worms, ..., humans. Heck, just looking at the standard model, we might guess that the universe would be just a fog of hydrogen or something else so simple. Even if we looked at the standard model long enough to conclude that galaxies and stars would form, some stars would explode and create some of the periodic table (the rest created otherwise), condense to planets, it's still tough to see why the planets would be more than, say, just Mars. But, no, DNA happened and after a billion or so years, we happened. That looks so astounding it looks suspiciously like part of a purpose. But you are right, that's not physics yet.
The best idea I've heard about a purpose for the universe is the theory that it evolved to create black holes which contain 'child' universes inside. That would mean the purpose of the universe is the same as the purpose of life in general.
(1) the purpose of the universe,
https://news.ycombinator.com/item?id=14570170
(2) the end of the universe, (A) big expansion and cool down to nothing, (B) no more expansion and cool down to nothing, (C) contraction back to another big bang, (D) something else very different?