Are Some Things About the Universe Fundamentally Unknowable? (forbes.com)

StartsWithABang writes: As we peel back the layers of information deeper and deeper into the Universe's history, we uncover progressively more knowledge about how everything we know today came to be. The discovery of distant galaxies and their redshifts led to expanding Universe, which led to the Big Bang and the discovery of very early phases like the cosmic microwave background and big bang nucleosynthesis. But before that, there was a period of cosmic inflation that left its mark on the Universe. What came before inflation, then? Did it always exist? Did it have a beginning? Or did it mark the rebirth of a cosmic cycle? Maddeningly, this information may forever be inaccessible to us, as the nature of inflation wipes all this information clean from our visible Universe.

Comments

Yes, some things are.

[Anonymous Coward]

Forbes's insistence that I drop adblockers, when their ads have been empirically detected dispensing malware, is one of them.

So is StartsWithAWhimper's insistence of posting his blogspam here.

Re:There was no before

[bhartman34]

I'm not saying you're wrong, because I don't know, but that doesn't make logical sense. Everything we have ever known has had a cause. We might not know what that cause is, but there has to be a cause there. It may simply be inaccessible to us. If the universe is everything we have ever known, then it's by definition not possible to know what came before it. But that doesn't mean that there was no before. It just means it's imperceptible to us. If you want to say that it makes no difference if there was a before, that's another matter, but it's not the same thing.

Re: There was no before

[Anonymous Coward]

I hole-hardedly agree, but allow me to play doubles advocate here for a moment. For all intensive purposes I think you are wrong. In an age where false morals are a diamond dozen, true virtues are a blessing in the skies. We often put our false morality on a petal stool like a bunch of pre-Madonnas, but you all seem to be taking something very valuable for granite. So I ask of you to mustard up all the strength you can because it is a doggy dog world out there. Although there is some merit to what you are saying it seems like you have a huge ship on your shoulder. In your argument you seem to throw everything in but the kids Nsync, and even though you are having a feel day with this I am here to bring you back into reality. I have a sick sense when it comes to these types of things. It is almost spooky, because I cannot turn a blonde eye to these glaring flaws in your rhetoric. I have zero taller ants when it comes to people spouting out hate in the name of moral righteousness. You just need to remember what comes around is all around, and when supply and command fails you will be the first to go. Make my words, when you get down to brass stacks it doesn't take rocket appliances to get two birds stoned at once. It's clear who makes the pants in this relationship, and sometimes you just have to swallow your prize and accept the facts. You might have to come to this conclusion through denial and error but I swear on my mother's mating name that when you put the petal to the medal you will pass with flying carpets like itâ(TM)s a peach of cake.

We know there are questions we can't answer.

[JoshuaZ]

We already know there are questions we can't answer. In fact, it isn't that hard to write down questions where barring extreme surprises, we can't answer them even given that they are essentially just simple computations. For example, does 2^(10^(10^500)) +1 have an even or odd number of distinct prime factors? That took two seconds to write down, but unless there's something very weird about numbers close to powers of 2 then we literally lack the computational power in the observable universe to answer that question. So we already have pretty hard physical limits on what we can know. This is just a question of whether there are also hard physical limits to questions that some people happen to care a lot about.

Re:We know there are questions we can't answer.

[JoshuaZ]

Not really. It is possible that there are physical discoveries that we're not expecting that will allow us to do extreme computations, but they aren't that likely to do that much.

Let's use your example of quantum computers. We have strong theorems about what a quantum computer can do compared to a classical computer. In particular, BQP, the class of problems that a quantum computer can do in polynomial time https://en.wikipedia.org/wiki/BQP0 is in PSPACE https://en.wikipedia.org/wiki/PSPACE, the class of problems that a classical computer can do in polynomial space (where polynomial in both cases means polynomial in the length of the input). This means that a quantum computer *cannot* massively extend what one can do much beyond speeding up some calculations, and other theorems show that this is a general pattern. Holevo's theorem and a few other similar theorems say more or less that you cannot use n qubits to simulate n+1 bits https://en.wikipedia.org/wiki/Holevo's_theorem. And in fact, the conjecture strongly is that BQP is *much smaller* than PSPACE.

Now, you might say that you just meant quantum computing as an example. But people have actually thought about what possible computing analogs would make sense that would be even more powerful than quantum computers. So for example, Scott Aaronson has looked at models involving access to a hidden variable http://www.scottaaronson.com/papers/qchvpra.pdf and it turns out that while they are naturally more powerful than quantum computers, again their are pretty strong limits on what they can do.

Moreover, we have pretty good ideas at this point of upper bounds on what physically can be computed and stored in an area. One example of this is the holographic principle https://en.wikipedia.org/wiki/Holographic_principle which puts pretty severe limits on how much information can be stored or presented. And even if the holographic principle is *wrong* (not implausible), and let's say that somehow it isn't just wrong in the obvious way (where the amount of information increases directly proportional to the volume) but in fact does so according to say a 20th power of the volume with a constant out front that in the relevant units is a hundred times as large as that in the holographic bound, one would *still* have nowhere near enough bits to plausibly do this sort of thing.

Frankly, when I give the sort of problem I mentioned earlier, instead of using a small stack of exponentials, I normally use the Ackermann function https://en.wikipedia.org/wiki/Ackermann_function and say something like A(100) +1, which is insanely bigger than the number I used. So even if you don't buy the arguments above, just use a number like that which is easy to specify mathematically and is mindboggingly larger.

If I drop my adblocker

[Deadstick]

...it will be on your foot.

Re:There was no before

[physicsphairy]

Everything we have ever known has had a cause.

I disagree, we are ever in search of causes, precisely because our body of facts great exceeds our body of explanations. Some facts, such as quantum randomness, seem to explicitly exceed our ability to link a previous state to the final state except by statistical description.

Taking it for granted that we can uniquely relate all effects that we have observed with prior causes -- and even that we will never encounter a future exception -- on what basis can we assume this would apply when the universe was in a fundamentally different situation? In fact, we know some of our existing assumptions must break down, and it is one of the standing problems to understand how. But how can you assign a probability to rules like cause and effect under unknown conditions? Inside the scope of a basketball game, you can estimate the probability that a player, or a group of players, will score. What good is that estimate if I tell you their next game will be a newly invented sport with unknown rules?

But I think it's fine to assume things like an ultimate cause or chain of causes. It's not science, because it's not subject to observational inquiry. However, it may still be true. I just don't think it's something we can state as having to be true.

Yes, Ethan

[110010001000]

Yes, Ethan, there is. How can you possibly be making enough money writing your crummy blog with malware ads on it? It is unpossible that you can be making money with it.

Re:There was no before

[readin]

Related to this is the problem of our mental ability to conceive of that which we have never experienced. Can anyone understand imagine a 4D space as more than just a mathematical model? How about the behavior of time as something that dialates? We can do the math, but we can't wrap our minds around the reality because our brains just aren't wired that way. What if the whole "everything has a reason" could be in the same category as the constancy of time - something obviously true but wrong. And because our brain refuses to accept any other conclusion we rationalize things that have no reason by supplying reasons. Even logic might have this problem. If A implies B and B implies C, then A implies true. Obviously and undeniably true according to our brains. Are our brains correct? We have a model of logic is internally consistent and that seems to work for us. We judge everything against that model. If that model is wrong then we'll never know.

Re: There was no before

[ShieldW0lf]

I was referring to the fact that he actually was begging the question, but 'First there was everything' was the question he was begging. Irregardless was thrown in to poke fun at the people who think it's about grammar.

Many things are fundamentally unknowable

[reve_etrange]

There's an infinite number of unknowable facts. I think "fundamentally" is sort of a semantic trick that makes it seems like there's a distinction with a difference even when there might not be one. Exampe: my friend crashed his bike and had retrograde amnesia for a few hours. What caused the crash is unknowable. Although it could have been observed, it just wasn't. There's no way now to go out and capture those photons, long since scattered and reabsorbed, etc. The path he was on has been totally repaved and redesigned. What happened to him is just as unknowable to human beings as esoteric facts about the early universe, the real difference is that bike accidents are mundane and the early universe is interesting.

end game

[swell]

This thought line reminds of two things that keep it in perspective:

1 The TED podcast of January 4 "Have we reached the end of physics?" by Harry Cliff. He points out that there are some things that we can never know (or prove with any foreseeable technology.) Big surprise!

2 Charles H. Duell was the Commissioner of US patent office in 1899. Mr. Deull's most famous attributed utterance is that "everything that can be invented has been invented." Whether this is a correct attribution is irrelevant to this discussion.

It is possible that at some point the rate of new discoveries and ideas will diminish, but history has shown the opposite- a snowballing increase in human knowledge in almost every area. Of course we will never know it all, never be able to prove all that we do know, but we will keep on striving.