Cosmology and the mediocrity principle

[otseng]

The mediocrity principle is the philosophical notion that "if an item is drawn at random from one of several sets or categories, it's likelier to come from the most numerous category than from any one of the less numerous categories" (Kukla 2009).[1] The principle has been taken to suggest that there is nothing very unusual about the evolution of the Solar System, the Earth, humans, or any one nation. It is a heuristic in the vein of the Copernican principle, and is sometimes used as a philosophical statement about the place of humanity. The idea is to assume mediocrity, rather than starting with the assumption that a phenomenon is special, privileged or exceptional.[2][3]

http://en.wikipedia.org/wiki/Mediocrity_principle

Current cosmology assumes that the mediocrity principle is true. Our solar system, the earth, and humans are not special. But, is this assumption true? Why or why not?

[Danmark]

A true statement would be, "based on the evidence so far, at this point, we simply can't say whether other sentient life exists or not."

Now that's a true statement.

You did not address the example of unicorns.

Instead of alien sentient life, let's replace it with something else. Suppose we talk about unicorns instead. We have no evidence that any unicorns exist. Can we say that none actually exist? Or do we have to say, "based on our current knowledge we are simply unable to be able to determine whether any unicorns exist or not"?

Should we also say, ""based on the evidence so far, at this point, we simply can't say whether unicorns exists or not"?

The proper question is not whether 'unicorns exist or not,' but what is the evidence they might have existed. If there is no evidence the unicorns have existed, why should we posit they might have existed? With no evidedence at all that 'X' exists or has ever existed, why should X even be the subject of inquiry? If I claim to believe in the great flying spaghetti monster or Allah, or any other entity no matter how fanciful or arbitrarary, why should such belief or claim even be examined?

[Divine Insight]

A true statement would be, "based on the evidence so far, at this point, we simply can't say whether other sentient life exists or not."

Now that's a true statement.

You did not address the example of unicorns.

Instead of alien sentient life, let's replace it with something else. Suppose we talk about unicorns instead. We have no evidence that any unicorns exist. Can we say that none actually exist? Or do we have to say, "based on our current knowledge we are simply unable to be able to determine whether any unicorns exist or not"?

Should we also say, ""based on the evidence so far, at this point, we simply can't say whether unicorns exists or not"?

The unicorn example is profoundly different.

For one thing if you are asking if we can say whether or not unicorns exist in the universe, the answer is no. We can't say, because we can't exam the entire universe.

Can we say that no unicorns exist on planet earth? I think we can say that with a very high degree of confidence since it's likely that if there were any unicorns on earth someone credible would have seen one by now and documented its existence.

The lack of evidence for unicorns on earth is pretty profound precisely because the earth is within our reach to explore thoroughly.

What you seem to be failing to understand (or refusing to acknowledge) is that it is simply not possible for us to explore the entire universe for signals from sentient life forms.

SETI hasn't even made a thorough search of our own galaxy. Much less the galaxies within our local group. It's extremely unlikely that we would even be able to detect signals from far off galaxies at all.

Don't forget, even an advanced civilization isn't going to be sending signals with the power of an entire star. So we're talking about some pretty faint signals. That may not have even been transmitted in our particular direction.

Not to mention all the different frequencies to listen in on. All the different methods of modulation, etc. SETI may have actually missed signals in places they have already looked simply because they weren't looking for the right technology or means of modulation, etc.

The universe is simply too vast for us to draw any conclusions about the existence of other sentient life based upon our "current knowledge".

This is why "Based on our currently knowledge we cannot say whether other sentient life forms exist in the universe".

It's simply misleading and incorrect to say "Based on our current knowledge there is no other sentient life forms in the universe". That is actually claiming that we have knowledge that there is no other sentient life forms. Which is simply not true.

The real truth is that currently we simply do not possess the knowledge of whether or not there is other sentient life forms in the universe.

I think it's safe to say that we currently possess knowledge that there probably aren't any unicorns on planet earth. Or if there are they are very rare and they are being kept well hidden.

In fact, technological aliens might have reasons to want to hide. They might have made their communication systems very stealthy so that they can pinpoint a transmission very focused toward only the people they want to hear it. If that's the case, then we would never overhear transmissions unless we just happened to accidentally be in the line-of-sight of their transmissions.

This type of technology might also be used for the sake of power efficiency. Why broadcast a very wide signal that will dissipate and become weak quickly when you can broadcast a highly directed laser beam aimed directly at the point you are attempting to communicate with?

We simply may not even have the technology available yet to even detect highly advanced communications. All of the work SETI has been doing so far may simply be too archaic to detect highly advanced signals.

[Divine Insight]

A true statement would be, "based on the evidence so far, at this point, we simply can't say whether other sentient life exists or not."

Now that's a true statement.

You did not address the example of unicorns.

Instead of alien sentient life, let's replace it with something else. Suppose we talk about unicorns instead. We have no evidence that any unicorns exist. Can we say that none actually exist? Or do we have to say, "based on our current knowledge we are simply unable to be able to determine whether any unicorns exist or not"?

Should we also say, ""based on the evidence so far, at this point, we simply can't say whether unicorns exists or not"?

The proper question is not whether 'unicorns exist or not,' but what is the evidence they might have existed. If there is no evidence the unicorns have existed, why should we posit they might have existed? With no evidedence at all that 'X' exists or has ever existed, why should X even be the subject of inquiry? If I claim to believe in the great flying spaghetti monster or Allah, or any other entity no matter how fanciful or arbitrarary, why should such belief or claim even be examined?

I suppose also, how a person defines "unicorns".

I just looked up a definition and found:

Unicorn - a mythical animal typically represented as a horse with a single straight horn projecting from its forehead.

So in this definition it's actually defined as a mythical animal.

Other than that it appears to just be a horse with a single horn projecting from its forehead.

Could there have actually been horses that had a single horn projecting from their head? Possibly. But no one has found any evidence for one on planet earth. And the main point of consideration is that the earth has been examined fairly closely. That doesn't mean that a fossil of a horned horse might not still be found. So in that sense, it is still open to the possibility that perhaps a 'unicorn' did exist at one time.

We can't really say with absolute certainty that horned horses never existed on earth. All we can say is that we haven't found any evidence for them and the earth has been examined pretty thoroughly.

But the universe as a whole has not been examined thoroughly and that's really the big difference here.

[FarWanderer]

Do you have any particular reason to believe the initial mass of the universe was "produced" by the universe, or, even assuming that it was, that it was finite?

Where did I say the universe was produced by the universe?

Nowhere. I think you misread, unless you actually equivocate "initial mass of the universe" with "universe".

Although instead of "mass" I should have written "matter/energy".

2) Yes, infinite matter/energy would imply infinite size, but since when have I accepted that the universe must not be of infinite size?

What are your arguments for an universe of infinite size?

Your presupposition that I even have such arguments is incorrect, and it demonstrates that you weren't been paying attention when I expressed my position on this.

I know that you stated you have no arguments for an infinite universe. Yet, I have given arguments for a finite, so wanted to give you another chance. If you have no arguments for an infinite universe, and I do have arguments for a finite universe, would you agree that it is more reasonable to accept a finite universe?

Wow. Wow. That's ludicrous. Absolutely not. Do you honestly think that putting forth bad arguments makes your position more tenable?

All you've offered is circular arguments and your own personal intuition. Your score is 0. You have established no advantage for your position.

For my part I'm just pointing out that all your "evidence" amounts to nothing more than intuition and fallacious logic.

I don't think it's fallacious to accept a finite universe, in light of the fact that you nor anybody else is arguing for an infinite universe and I have already given arguments for a finite universe.

I'm perfectly capable of putting forth opposing arguments of equally fallacious caliber to yours, but I'm not going to.

Because it would be stupid.

My problem with your universe has never been that it's finite; it's that it has an arbitrary border.

Yes, there would be a boundary with a finite universe. Does it intuitively seem absurd? Perhaps. But, I think it naturally follows from a finite universe.

It doesn't even follow. A torus universe is finite and has no border.

But more than that, you are begging the question. If an arbitrary boundary is agreed to be unintuitive, then it'd be reason to believe the universe isn't of a structure that'd have one.

Can we agree that science does not affirm the existence of t=0?

I can agree that science can make no claims when the age of the universe was less than 1 Planck time.

OK. Can you agree that science can make no claims as to whether any "less than 1 Planck time" even exists?

Most of them. You, for example

If you're only referring to myself, I do not count as most apologists.

I believe that my use of "for example" implies there are others.

Any time a theist says "science cannot explain X therefore there's a supernatural cause" they are assuming that no unknown natural explanation for X exists.

You will find that most apologists make this claim in some way or another. Well, at least most apologists in the field of natural theology. I suppose "most" does not apply to apologists in general.

In order for this statement to be true, you have to assume the non-existence of any natural explanation, even an explanation we are unaware of.

If there's a current naturalistic explanation, I'm willing to entertain it.

If there were a current naturalistic explanation, it wouldn't be an explanation we are unaware of.

And if you are assuming there exists no natural explanation we are unaware of, well, then you are assuming science has a complete understanding of how the natural world works.

This goes back to what Divine Insight was saying. Sure, science might have an explanation in the future. But, we cannot appeal to the future and say, "Well, science one day will have an explanation for it." or "One day science will find evidence for aliens."

I'm not saying science has a complete understanding of the natural world. Far from it, I believe science only has a limited understanding of the natural world. Many more things will be discovered by science in the future. But, we don't know exactly what those things will be at the present time. We don't even know if science will ever be able to many questions that we currently have. I'm not even saying we should stop scientific pursuits. We should learn as much as we can. But, to say that science will have the answers is based on faith.

Yeah I know all this. That's why I never claimed that there actually is an unknown natural explanation.

You, on the other hand, have to assume there isn't one in order to make your argument.

If you insist that you don't think science has a complete understanding of the natural world, then please retract your argument that matter escaping a black hole would indicate a supernatural cause.

We are already discussing the merits of the cosmological principle, which if true would have the metric expansion of space as the best explanation for our observations.

If the cosmological principle is true, sure, metric expansion of space is probably the only way to explain things. But, there are some things I find problematic with the metric expansion of space. What is causing it? Is space uniformly expanding at every single point in the entire universe at the exact same rate? If so, what can account for that?

As I understand it, the dark energy model has an answer for all those questions. Although, like any explanation, it raises new questions. I personally find the concept of dark energy quite weird at first glance, but I'm not really in a position to judge.

In any case, the more important point is that the answers aren't required. We don't need to know the cause of a phenomenon to know it exists.

You are free to argue the merits of the visible universe comprising most of the complete universe.

If there is no metric expansion of space and the universe is approximately 15 billion years old, the radius of the universe cannot be more than 15 billion light years.

And if there is, then the radius can be larger. What's your point? Do our measurements of the most distant galaxies indicate they are no more than 15 billion light years away?

By the way, if the speed of light limited how fast things can move away from Earth, things would not ever disappear from the Hubble Sphere. And the expansion of the universe would not be accelerating. In fact, without a metricly applied cosmological constant pushing things along, expansion would be decelerating on account of gravity.

We do have measuring techniques and have done quite a lot of measuring in a variety of distances and directions, and through all of it I've never even heard of a density pattern that occurs with respect to Earth, so I'm pretty sure none exists.

Yes, this could be a test of my model. If my model holds that the universe is heterogeneous, then density would be a function of distance and not of direction.

Aaaand, have we not measured the distance of a large number of galaxies? What of those measurements? Have they shown the density pattern your scenario predicts?

Any and all "evidence" for God would be just as good as evidence for aliens.

I don't know what you mean by this. You mean aliens can also account for the origin of the universe?

Wasn't really thinking about the origin of the universe... but sure, why not?

Doesn't make any sense to me. Do you want to explain how aliens can account for the origin of the universe?

They used advanced technology to create a universe so they could live in it.

[Unhand Me Sir]

It sounds obvious that something that is not infinitely old must have a beginning, but no boundary theories in which there is no point time=zero have been around for 30 years.

Could you go into more detail about this?

Sure, and sorry for the delay. The idea was proposed in 1983 by Stephen Hawking and James Hartle.

The idea is that a lot of technical problems can be resolved by allowing time to be represented by a complex number rather than a real number. This adds a dimension to space-time by making time a 2-dimensional quantity. The Big Bang is a singularity viewed in real time, but viewed in complex time it isn't. This space-time is finite in extent but has no boundary.

Hawking's analogy is with a sphere - it's finite but it has no edges. The singularity in real time is like the point of a cone, impossible to smoothly include in the rest of the geometry. In complex time it becomes like the north pole of a sphere - an origin but also a point on the sphere like any other. This removes problem of a singularity at which the laws that apply everywhere else break down.

Treating time as a complex variable was already a standard tool in quantum mechanics, where the mathematics can be made precise. It isn't yet precise in this context - like string theory it's more a hope that one day it might be.

Challenged on what complex time could mean, Hawking tends to dismiss the question and say that as a positivist he's only interested in developing mathematically consistent theories that correspond to observed data.

[otseng]

The proper question is not whether 'unicorns exist or not,' but what is the evidence they might have existed. If there is no evidence the unicorns have existed, why should we posit they might have existed? With no evidedence at all that 'X' exists or has ever existed, why should X even be the subject of inquiry?

Sure, valid questions. Is there any evidence that aliens have existed? If there is no evidence that aliens exist or have existed, why should aliens be a subject of inquiry?

[Divine Insight]

The proper question is not whether 'unicorns exist or not,' but what is the evidence they might have existed. If there is no evidence the unicorns have existed, why should we posit they might have existed? With no evidedence at all that 'X' exists or has ever existed, why should X even be the subject of inquiry?

Sure, valid questions. Is there any evidence that aliens have existed? If there is no evidence that aliens exist or have existed, why should aliens be a subject of inquiry?

Actually I disagree with Danmark on this one. We have mythological claims that unicorns have existed. Those claims are worth looking into whether the result is to validate them or invalidate them.

I think it's funny that unicorns are often used as an example something that no one believes in. Christians should certainly believe in unicorns since they are mentioned in the Bible quite often.

I think the question of aliens is a bit different. It's not that we have any reputable reports of aliens, but the simple fact that we exist in this universe should be reason enough to suspect that other life may have also evolved.

After all, why should we be so arrogant to believe that we're the only example of life in the universe? It seems to me that to jump to the conclusion that we are special in a universe as vast as what we see before us is actually the unwarranted conclusion.

Also, why would a creator have even bothered creating such an enormous universe just to have us as pets?

Who would go out and buy or build billions upon billions of aquariums just to keep their gold fish in only one aquarium?

Even our single galaxy would have already been overkill for that.

But to have created hundreds of billions of galaxies just to create a bunch of sinners on one speck of dust doesn't make a whole lot of sense. And supposedly according to both the Old Testament and the New Testament only a very few of the billions of people on this speck of dust called Earth are going to be worth saving.

Seems like an awful big universe just to grant a handful of sinners amnesty for their sins.

That just doesn't seem like a very compelling answer to the riddle of reality to me. Carl Sagan certainly felt this way as well, he often said, "The Stage is far too large for the Biblical Plot".

Note: I realized that I keep bringing up the Biblical picture, but let's face it, is there really any reason to believe that we are somehow "special" outside of a paradigm like the biblical picture?

Is there any genuine scientific, secular, or rational reason why we should believe that we are somehow special in a universe as vast as what we find ourselves in?

I don't see how any scientific, secular, or rational reason can be given to suggest that we should believe that we are special.

[otseng]

For one thing if you are asking if we can say whether or not unicorns exist in the universe, the answer is no. We can't say, because we can't exam the entire universe.

The lack of evidence for unicorns on earth is pretty profound precisely because the earth is within our reach to explore thoroughly.

I don't think we can ever explore the entire universe (or even the earth). But, I would agree that if we did explore every single place in the universe (or earth), then we can then definitely say whether something exists or not. But, that is quite a high bar to reach, which I think is an unpractical level.

I don't think we need to reach the point of conclusiveness to make a claim. I believe one can reasonably make a claim based on available evidence, until new evidence is presented to the contrary. In my epistemology, I would simply say that based on the lack of any evidence for unicorns, they do not exist.

I believe this is also how most atheists think. They believe that they will not believe in something if no evidence exists for it. Since they believe that no evidence exists for God, then God does not exist. If they used your line of reasoning, they cannot say if God exists or not since they cannot explore the entire universe, let alone outside the universe.

Your line of reasoning is at least consistent. You make no claims of God or aliens or unicorns since we have not explored everywhere. So, it's a reasonable position to take.

For atheists, I do not find it consistent. Atheists believe God does not exist since they believe no evidence exists. But no evidence also exists for aliens, yet none, as far as I know, would claim that no aliens exist.

What you seem to be failing to understand (or refusing to acknowledge) is that it is simply not possible for us to explore the entire universe for signals from sentient life forms.

Yes, I understand that. And yes, I fully acknowledge that we can only explore a limited part of the entire universe.

Here is really my only point. We think that other intelligent life exists not based on any evidence, but only on the mediocrity principle.

We have a small set of data of the universe. Out of this small set of data, there is no evidence for aliens. There remains a large set of data that could point to the existence of aliens. But, what is the justification that evidence do exist in the unexplored set of data? I maintain it's only because of the assumption of the mediocrity principle. There is no way that we are special, so other life must exist.

In fact, technological aliens might have reasons to want to hide.

I think it's quite presumptuous to guess the motivations of things we don't even know exists.

[otseng]

I suppose also, how a person defines "unicorns".

Actually, in the back of my mind, I was thinking of the unicorn fish.


http://en.wikipedia.org/wiki/Naso_(genus)

[otseng]

Do you have any particular reason to believe the initial mass of the universe was "produced" by the universe, or, even assuming that it was, that it was finite?

Where did I say the universe was produced by the universe?

Nowhere. I think you misread, unless you actually equivocate "initial mass of the universe" with "universe".

Although instead of "mass" I should have written "matter/energy".

Whether you meant mass or matter/energy, where did I ever say or imply that the mass/matter/energy of the universe was produced by the universe?

My problem with your universe has never been that it's finite; it's that it has an arbitrary border.

Yes, there would be a boundary with a finite universe. Does it intuitively seem absurd? Perhaps. But, I think it naturally follows from a finite universe.

It doesn't even follow. A torus universe is finite and has no border.

I'm referring to a flat, Euclidean, finite universe. A torus universe is not flat and Euclidean.

Can you agree that science can make no claims as to whether any "less than 1 Planck time" even exists?

If 1 Planck time exists, then we don't know if less than 1 Planck time exists?

Any time a theist says "science cannot explain X therefore there's a supernatural cause" they are assuming that no unknown natural explanation for X exists.

It's only assuming that based on current understanding, no viable naturalistic explanation exists.

You, on the other hand, have to assume there isn't one in order to make your argument.

Never said that. All I've said is that currently there is no viable naturalistic explanation.

If the cosmological principle is true, sure, metric expansion of space is probably the only way to explain things. But, there are some things I find problematic with the metric expansion of space. What is causing it? Is space uniformly expanding at every single point in the entire universe at the exact same rate? If so, what can account for that?

As I understand it, the dark energy model has an answer for all those questions. Although, like any explanation, it raises new questions. I personally find the concept of dark energy quite weird at first glance, but I'm not really in a position to judge.

Dark energy and dark matter are another example of ad hoc explanations to me.

Even if dark energy was the cause of the metric expansion of space, it still does not answer the question if every single point in the entire universe is expanding at the exact same rate.

In any case, the more important point is that the answers aren't required. We don't need to know the cause of a phenomenon to know it exists.

If you're referring to the metric expansion of space, I would not classify it as a phenomenon, but an assumption.

You are free to argue the merits of the visible universe comprising most of the complete universe.

If there is no metric expansion of space and the universe is approximately 15 billion years old, the radius of the universe cannot be more than 15 billion light years.

And if there is, then the radius can be larger. What's your point?

Yes, if there is metric expansion of space, the universe can be much larger than 15 billion light years in radius.

All I'm saying is that if there is no metric expansion of space, it cannot be larger than 15 billion light years in radius.

Do our measurements of the most distant galaxies indicate they are no more than 15 billion light years away?

Depends on what you mean by measurements. We cannot really directly measure distances on that scale. Many assumptions have to be made to calculate very far distances.

Need to go, we can talk more about this later.