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?

[otseng]

What we know is that we have not yet been able to examine the universe in great enough detail to know whether there is any evidence for intelligent life elsewhere or not. And that is an entirely different thing from knowing that there is no evidence for intelligent life existing elsewhere.

You mean until we have looked in every crook and cranny of every single planet in the universe, then we can say that according to what we know, that no extraterrestrial life exists?

You statement makes it sound like we currently have reasons to believe that there is no evidence for intelligent life elsewhere in the universe. And that is certainly false.

Do you believe that other intelligent life do exist? On what basis do you ground this?

Our current lack of technological abilities is not sufficient reason to be making conclusions about things we can't yet determine.

As I pointed out in my previous post, it's not just us that would be looking for ETs. If alien intelligent life existed, they could also be attempting to contact/visit us.

[otseng]

You haven't convinced me, but again, I still don't even see why it's relevant that you do.

I'm not asking if I've convinced you. I'm asking if my argument is sound.

Not all flat universes are Euclidean.

Could you give an example of this?

Leaving an infinite number of possible non-zero values, all of which would deny a genuinely flat universe.

The non-zero value is due to the limitations of our measurements, not to actually pointing to a curvature of our universe. Now, it could be that the universe is actually slightly curved because of measurement limitations. But, we have been progressively making more accurate measurements, and they have all pointed to a flat universe. Time will tell in the future as we make more accurate measurements if a flat universe still holds.

Even assuming a center, should we expect not to see isotropy and homogeneity from a non-center location?

Not if everything is moving away from the center.

Suppose we are halfway between the center and the edge. If we look toward the center, things would be moving towards us. If we look on the other side, things would be moving away from us. It would not be isotropic.

Also, if things are moving from the center, it would not be homogeneous. Think of a fireworks explosion. Unless things are constantly being newly generated from the center, it would not be homogeneous.

If we are at the center, then all of the matter of the universe would've expanded from our location. Thus, it can be possible that our solar system formed before distant stars formed.

Still a non-sequitur.

Think of it like colonists moving out from Plymouth Rock. Some colonists moved out to Boston or to Buffalo. It could be possible that colonists created houses in Boston or Buffalo before creating one in Plymouth Rock, but it's not likely. It would be more likely that houses got created first at Plymouth Rock.

[Divine Insight]

You mean until we have looked in every crook and cranny of every single planet in the universe, then we can say that according to what we know, that no extraterrestrial life exists?

In science it isn't meaningful to claim that there is "no evidence" for something if we have no way of testing for that evidence. Typically when we say that we have "no evidence" for something that means that we actually looked in a meaningful way and found none. I don't think the search for extraterrestrial life has been done in a way that would warrant saying that there is "no evidence" for it.

Do you believe that other intelligent life do exist? On what basis do you ground this?

I believe that it's far more likely than not.

I base the evidence on the very simple observation that everything we know about life thus far shows that it only requires the elements that are naturally in abundance throughout the universe.

We can see that the same elements, laws of physics, and natural processes do exist far out into the cosmos. This is an observation we can make. So we have very strong evidence that the chemistry and physics of the universe is basically the same throughout.

We know that life evolved on Earth. Therefore the idea that it could have evolved in other places in the universe seem highly plausible. So plausible that I am confident that it would indeed be inevitable.

As I pointed out in my previous post, it's not just us that would be looking for ETs. If alien intelligent life existed, they could also be attempting to contact/visit us.

Do you have any serious clue just how big the universe actually is?

Do you realize that humans on planet Earth have only been creating radio signals for about 200 years. And that includes going back to the very early invention of radio waves.

Even if the very earliest signals we created managed to be transmitted into space those signals would have only been traveling through space for 200 years. That means that they would only be 200 light years from earth at this very moment.

Our Milky Way Galaxy is 100,000 light years across. So our earliest possible radio signals haven't even hardly left the vicinity of our own solar system yet in comparison with the size of the Milky Way Galaxy.

And that's considering the very earliest possible radio signals we can muster. Any actually attempts to send out signals to other planets or solar systems are far more recent, and have therefore traveled far less distance.

And now think about the Andromeda galaxy. Our closest neighboring galaxy. It is over 2.5 million light years away. Anyone there wouldn't never even know that the earth exists. And if anyone there had sent signals to us they would have had to have sent them 2.5 million years ago.

Also, unless these signals were aimed directly at us they aren't going to be very strong.

Think about this also: How long do civilizations last? And how long are they going to sit around just sending out radio signals? For us to receive a radio signal from some civilization on Andromeda today, they would have had to have been sending that single out 2.5 million years ago today. Look at the timing considerations too.

We not only need to find a signal that is basically pointed at us, but we also need to find one that was pointed at us at a very specific point in time.

You seem to think that if there's life out there we should just hear lots of chatter like we hear on earth radio stations. But that would be a very unlikely coincidence of timing.

If we ever catch a signal from an alien civilization we are going to be extremely lucky. And chances are that the aliens we hear from will have long since become extinct. Or at least the civilization that sent the single will no longer be there and if there is anything still there is a far advanced form of that civilization.

Other words, if we catch a single from a planet that is a mere 2000 light years away (just next door to us within our own Milky Way Galaxy) that single will have been sent toward the Earth at the time Jesus supposedly lived. That's how old that civilization will be today. They will have advanced for 2000 years since they sent that signal. Or maybe died out and become a completely different civilzation

And that would be a civilization that is basically "next door" to us.

If we get a signal from Andromeda, what will have been from 2.5 million years ago. It would be impossible to know whether there is anyone left from that civilization today in Andromeda. And that is just are "closest neighboring galaxy".

Signals from galaxies further away that Andromeda are going to be extreme faint and difficult to detect. It's also highly unlikely that they will be pointed at us. Or the Milky Way in general.

Actually looking at Andromeda might be the best hope since it might make some sense that people living on Andromeda might actually point a signal to the Milky way being that we are one of its closest neighbors too.

In any case, so far we have only been talking about 2 Galaxies ours and Andromeda. But there are hundreds of billions of galaxies in the universe. And detecting intelligible radio signals from them is even more difficult.

This would be like going to the ocean putting in an eyedropper and sucking up some water to put in a test tube to exam it for fish. Chances are that you won't have caught a fish that way.

So should you then conclude that there is "no evidence" for fish in the ocean?

[Goat]

I will also say that 'We don't have any evidence there isn't any (intelligent) life existing elsewhere either'. I would have to say 'We do not have the ability to do an extensive examination of even 1/100,000th of the stars in this galaxy alone , nor can we show that the method we are using is effective).

It's not just us actively looking for ETs. But, ETs have not been contacting/visiting us either. This is expressed in the Fermi paradox.

The Fermi paradox (or Fermi's paradox) is the apparent contradiction between high estimates of the probability of the existence of extraterrestrial civilization and humanity's lack of contact with, or evidence for, such civilizations.

According to this line of thinking, the Earth should already have been colonized, or at least visited. But no convincing evidence of this exists. Furthermore, no confirmed signs of intelligence (see Empirical resolution attempts) elsewhere have yet been spotted in our galaxy or (to the extent it would be detectable) elsewhere in the observable universe. Hence Fermi's question, "Where is everybody?"

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

Too many unknowns, but there are a WHOLE bunch of solutions to it, also based on possibilities (this link is a 'docx' file that I can't get the actual link w

Where is Everybody?
Fifty Solutions to the Fermi Paradox and the Problem of Extraterrestrial Life
Stephen Webb

Stephen Webb is a physicist working at the Open University in England.


Fermi’s Paradox:
Enrico Fermi, in response to a lunch time discussion about extraterrestrials, asked the question “Where is Everybody?� (i.e. where are extraterrestrials). This became known as the Fermi Paradox (1950).
Given the vastness of the universe (around 1022 stars), the age of the universe (13 billion years), and the universal laws of chemistry and physics, many assume that life must be present elsewhere in the universe.
The Fermi Paradox. (1) According to the Copernican Principle, there is nothing special about Earth or humanity, so whatever is true here should be true elsewhere in the galaxy. (2) Following this reasoning, Frank Drake predicted the existence of tens of thousands of advanced extraterrestrial civilizations (ETC) and Carl Sagan likewise predicted perhaps a million ETC. Such estimates are typically based on the Drake Equation (1961). (3) At least some of these ETC’s must be millions or even billions of years more advanced than us. (4) Given some very reasonable assumptions, even one such ETC could colonize the entire galaxy in as short as 2-5 million years or more conservatively 10-60 million years. (5) If ETC’s can spread so rapidly, they should have already reached Earth (or at least we should have detected their existence). Given that there is no definitive evidence (direct or indirect) that we have been contacted by any of these civilizations, then something must be wrong with this chain of reasoning.
If there are a billion ETC’s, then the nearest one would be around 300 light years away. If there are only a thousand ETC’s, then the nearest one would be around 1,000 light years away.


They Are Here:
This class of solutions posits that advanced extraterrestrial civilizations exist and have visited or are visiting. This is the most popular interpretation among the general populous.
1) They Are Here and They Call Themselves Hungarians
A tongue-in-cheek explanation for famous Hungarian scientists (e.g. von Neumann)
2) They Are Here and Meddling in Human Affairs
Flying saucers, UFOs, etc. are extraterrestrial spacecraft
3) They Were Here and Left Evidence of Their Presence
“Face� on Mars, backside of the Moon, etc.
4) They Exist and They Are Us – We are the Aliens!
Panspermia
5) The Zoo Scenario
A no interference “Prime Directive� is in effect
6) The Interdict Scenario
The presence of many civilizations prevents spreading to Earth
7) The Planetarium Hypothesis
We are inside a giant computer simulation (e.g. like movies Matrix and Truman Show)
8) God Exists
They Exist But Have Not Communicated:
This class of solutions posits that advanced extraterrestrial civilizations exist but we have not made contact. This is by far the most popular interpretation among research scientists
9) The Stars Are Far Away
Long travel times between stars because of speed of light limits travel
Possible solutions: generation ships, hibernation, worm holes, etc.
10) They Have Not Had Time to Reach Us
Diffusion model of galactic colonization
11) A Percolation Theory
12) Bracewell-von Neumann Probes
Self-replicating robots explore the universe on behalf of the extraterrestrials
13) We Are Solar Chauvinists
They might favor stars very different from our own sun
14) They Stay at Home …
15) … and Surf the Net
They prefer virtual reality simulations rather than actual exploration
16) They Are Signaling But We Do Not Know How To listen
ET signals might not use light waves, e.g. gravity waves, neutrinos, tachyons, etc.
17) They Are Signaling But We Do Not Know at Which Frequency to Listen
The electro-magnetic spectrum is broad: radio, infrared, visible, x-ray
The period where a civilization is “radio-bright� (i.e. detectable by signal leakage) might be short
Different SETI strategies targeting different portions of the electro-magnetic spectrum
18) Our Search Strategy Is Wrong
19) The Signal Is Already There in the Data
20) We Have Not Listened Long Enough
If ETC’s are be short lived, then detecting them would be difficult
21) Everyone is Listening, No One is Transmitting
22) Berserkers
Berserker probes would eradicate young civilizations to prevent later competition
23) They Have No Desire to Communicate
24) They Develop Different Mathematics
25) They Are Calling But We Do Not Recognize the Signal
26) They Are Somewhere But the Universe Is Stranger Than We Imagine
Aliens transcend physical matter or are exploring alternate universes
27) A Choice of Catastrophes
Perhaps advanced societies always destroy themselves: nuclear or biological warfare, overpopulation, nanotechnology run amok, environmental catastrophes, particle physics disasters, or nearby gamma ray bursts (GRB)
28) They Hit the Singularity
Given Moore’s law (computing power doubles every 2 years), aliens might achieve transcendence prior to exploring the stars
29) Cloudy Skies Are Common
Delayed space exploration because of difficulties doing astronomy
30) Infinitely Many ETC’s Exist But Only One Within Our Particle Horizon: Us
The particle horizon represents the farthest out it is possible for us to observe but the universe might be infinite in extent

They Do Not Exist:
This class of solutions holds that we are alone in the universe—no other ETC’s.
31) The Universe Is Here for Us
If the number of “difficult� steps in the development of advanced life is too large, advance life might not appear before the parent sun becomes too unstable. For perspective, humanity appeared on early about halfway though through the sun’s lifespan
Anthropic principle
32) Life Can Have Emerged Only Recently
Life cannot appear anywhere in the galaxy until certain elements build up to certain levels, so ETC’s would not have started long before life started here.
33) Planetary Systems Are Rare
Some early models suggested the planetary formation required special circumstances and so would be rare but these models have been overturned
34) We Are the First
Life could not appear anywhere until sufficient quantities of certain elements had built up
35) Rocky Planets Are Rare
Some models suggested that rocky planet’s like Earth may requite the action of a gamma ray burster but there are more plausible models that do not require this event
36) Continuously Habitable Zones Are Narrow
The Habitable Zone refers to the distance a planet must be from the sun to maintain liquid water. The Continuously Habitable Zone is the region where liquid water is maintained for billions of years as the parent star changes in luminosity.
37) Jupiters Are Rare
Large gas giant planets may be common but they need to be in the right place and have a circular orbit to allow for habitable planets
38) Earth Has an Optimal “Pump for Evolution�
Extinction events (e.g. asteroidal collisions) make room for new life
39) The Galaxy Is a Dangerous Place
Black holes, supernova, and gamma ray bursts
40) A Planetary System Is a Dangerous Place
Snowball earth, super-volcanoes, and mass extinction events
41) Earth System of Plate Tectonics is Unique
Active plate tectonics is needed to recycle critical elements
42) The Moon is Unique
Our moon is necessary for maintaining stability, however, its formation requires very unusual circumstances
43) Life’s Genesis Is Rare
44) The Prokaryote-Eukaryote Transition is Rare
Prokaryotes are the simplest organisms. Eukaryote cells are the basis for multi-cellar life
45) Toolmaking Species Are Rare
46) Technological Progress Is Not Inevitable
47) Intelligence at the Human Level Is Rare
48) Language Is Unique to Humans
49) Science Is Not Inevitable
Ancient science was developed by the Greeks (c. 500 BC) but modern science appeared late (17th-18th century)
50) Stephen Webb’s Solution to the Fermi Paradox
It is likely that we are alone in the galaxy. Rather than a single solution (cause), it is likely some combination of the above listed solutions. Simple life (i.e. bacteria) may be common but we are likely the only advanced intelligent life.

[FarWanderer]

Not all flat universes are Euclidean.

Could you give an example of this?

I'm just reporting what I learned from the wikipedia "shape of the universe" page:

In a universe with zero curvature, the local geometry is flat. The most obvious global structure is that of Euclidean space, which is infinite in extent. Flat universes that are finite in extent include the torus and Klein bottle. Moreover, in three dimensions, there are 10 finite closed flat 3-manifolds, of which 6 are orientable and 4 are non-orientable. The most familiar is the aforementioned 3-Torus universe.

Leaving an infinite number of possible non-zero values, all of which would deny a genuinely flat universe.

The non-zero value is due to the limitations of our measurements, not to actually pointing to a curvature of our universe. Now, it could be that the universe is actually slightly curved because of measurement limitations. But, we have been progressively making more accurate measurements, and they have all pointed to a flat universe. Time will tell in the future as we make more accurate measurements if a flat universe still holds.

Indeed, the answer remains inscrutable. At least from measurement alone.

Even assuming a center, should we expect not to see isotropy and homogeneity from a non-center location?

Not if everything is moving away from the center.

Suppose we are halfway between the center and the edge. If we look toward the center, things would be moving towards us. If we look on the other side, things would be moving away from us. It would not be isotropic.

You're assuming the earth wouldn't also be moving in accordance to its non-central location. Sure, things from the center would be moving towards us, but we'd be moving away from them yet faster. This would give the appearance that they are moving away from us. The net result would be exactly what we observe.

If we are at the center, then all of the matter of the universe would've expanded from our location. Thus, it can be possible that our solar system formed before distant stars formed.

Still a non-sequitur.

Think of it like colonists moving out from Plymouth Rock. Some colonists moved out to Boston or to Buffalo. It could be possible that colonists created houses in Boston or Buffalo before creating one in Plymouth Rock, but it's not likely. It would be more likely that houses got created first at Plymouth Rock.

Why would it be more likely the houses got created first at Plymouth? And how is said reason applicable to the stars of the universe?

[H.sapiens]

Three jolly sailors from blandon-on-tyne
Went to sea in a bottle by klein.
Since the sea was entirely inside the hull,
The scenery seen was exceedingly dull.

Is that full frontal nerdity?

[Divine Insight]

Full frontal nerdity of geometric absurdity
in topographic perversity with biologic diversity

If only the world obeyed Mr. Klein
and every geodesic was a twisted straight line
we'd finally understand the eternity of time
and our knowledge of reality would be so sublime

[otseng]

In science it isn't meaningful to claim that there is "no evidence" for something if we have no way of testing for that evidence. Typically when we say that we have "no evidence" for something that means that we actually looked in a meaningful way and found none. I don't think the search for extraterrestrial life has been done in a way that would warrant saying that there is "no evidence" for it.

I already brought up the SETI program. Are you saying it is a completely bogus program?

I base the evidence on the very simple observation that everything we know about life thus far shows that it only requires the elements that are naturally in abundance throughout the universe.

As you know, life is not simply just a collection of elements. Though having the proper elements is necessary, it is far from sufficient.

We can see that the same elements, laws of physics, and natural processes do exist far out into the cosmos. This is an observation we can make. So we have very strong evidence that the chemistry and physics of the universe is basically the same throughout.

Sure, we can assume that laws of physics are the same elsewhere, but actually, as we learn more about what is required for complex life, we realize that it requires very specific conditions for complex life to arise. This is summarized in the Rare Earth hypothesis.

In planetary astronomy and astrobiology, the Rare Earth hypothesis argues that the emergence of complex multicellular life on Earth (and, subsequently, intelligence) required an improbable combination of astrophysical and geological events and circumstances. The hypothesis argues that complex extraterrestrial life is a very improbable phenomenon and likely to be extremely rare.

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

Do you have any serious clue just how big the universe actually is?

Actually, I don't, though I know what people claim it is.

You seem to think that if there's life out there we should just hear lots of chatter like we hear on earth radio stations. But that would be a very unlikely coincidence of timing.

I don't think that at all. What I think is that there is dead silence out there.

This would be like going to the ocean putting in an eyedropper and sucking up some water to put in a test tube to exam it for fish. Chances are that you won't have caught a fish that way.
So should you then conclude that there is "no evidence" for fish in the ocean?

Yes, it would be no evidence that we have so far that any other fish do exist.

[otseng]

Too many unknowns, but there are a WHOLE bunch of solutions to it, also based on possibilities

The first seven are sort of silly ("They Are Here and They Call Themselves Hungarians"??).

Eight I would agree with.

9 through 30 have some silly ones ("They Stay at Home… and Surf the Net") with some serious ones ("We Have Not Listened Long Enough").

31 through 50 are actually supported by the evidence that we are finding.

[Divine Insight]

I already brought up the SETI program. Are you saying it is a completely bogus program?

No, it's not a bogus program at all. But it's clearly not able to detect life anywhere in the universe. We'd be lucky to be able to detect an intelligent radio signal from within our own galaxy. Even detecting radio signals from nearby galaxies would be extreme difficult. Especially if they weren't specifically aimed toward us.

Detecting intelligent signals from far off galaxies would be virtually impossible. Detecting intelligent radio transmissions from a far off galaxy would be difficult even if we knew precisely where to look, what frequency it was on, and how it was being transmitted.

Don't forget a radio source is just going to be a pinpoint with a galaxy. And that radio transmission is going to be FAR LESS powerful than a star. Yet we have difficulty even seeing small dim stars that would be far more powerful than a radio signal transmitted by an intelligent species like us.

There's also the time factor. How long as SETI been looking? The institution was only born in 1984 and it certainly didn't have much capacity at that time. So it has only existed for 30 years and much of that time was probably quite crude.

Think about how big the universe is, not only in space, but in time. Our galaxy has been around for 13 billion years. Countless intelligent civilizations may have arisen and died over that period of time. We've only been looking very feebly for signals for less than 30 years.

How does that work out as a percentage? 30 divided by 13 billion = 0.000000002%

So that how long we have been looking for life in comparison with the age of our galaxy. Something like 2 billionths of a percent of the age of the galaxy. Again, this would be like taking a drop of water out of the ocean and claiming there must not be any fish in the ocean because the drop we checked didn't have any fish in it.

I base the evidence on the very simple observation that everything we know about life thus far shows that it only requires the elements that are naturally in abundance throughout the universe.

As you know, life is not simply just a collection of elements. Though having the proper elements is necessary, it is far from sufficient.

You don't know that. If life evolves naturally from these elements then it may very well be the case that all that is required are these elements and a sufficient amount of time given the right conditions. Earth like planets may all become infested with life for all we know.

We can see that the same elements, laws of physics, and natural processes do exist far out into the cosmos. This is an observation we can make. So we have very strong evidence that the chemistry and physics of the universe is basically the same throughout.

Sure, we can assume that laws of physics are the same elsewhere, but actually, as we learn more about what is required for complex life, we realize that it requires very specific conditions for complex life to arise. This is summarized in the Rare Earth hypothesis.

So, given that there are 70 sextillion stars in the observable universe there may be quite many planets that have these very specific conditions.

70 sextillion is 70 thousand million, million, million stars. That's a lot of rolls of the dice.

In planetary astronomy and astrobiology, the Rare Earth hypothesis argues that the emergence of complex multicellular life on Earth (and, subsequently, intelligence) required an improbable combination of astrophysical and geological events and circumstances. The hypothesis argues that complex extraterrestrial life is a very improbable phenomenon and likely to be extremely rare.

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

That's just an unproven hypothesis that makes a lot of arbitrary assumptions. We don't know that those assumptions being made are required for life to arise.

Do you have any serious clue just how big the universe actually is?

Actually, I don't, though I know what people claim it is.

It's beyond our ability to even comprehend in any intuitive sense.

Can you even remotely identify with a number like 70 sextillion of anything?

You seem to think that if there's life out there we should just hear lots of chatter like we hear on earth radio stations. But that would be a very unlikely coincidence of timing.

I don't think that at all. What I think is that there is dead silence out there.

Why would you say that? Looking for a signal from intelligent life is not just a matter of tuning your radio dial to the frequency it might be on. There's actually tons of noise out there and that makes it extremely difficult to detect intelligent signals. It's not going to pop out at you like a mega rock station on the radio.

This would be like going to the ocean putting in an eyedropper and sucking up some water to put in a test tube to exam it for fish. Chances are that you won't have caught a fish that way.
So should you then conclude that there is "no evidence" for fish in the ocean?

Yes, it would be no evidence that we have so far that any other fish do exist.

And it would clearly be wrong too. So obviously the lack of evidence we currently have is meaningless in terms of jumping to any conclusions at this time.

It would be a farce to use that information as an argument that there are not likely to be any fish in the ocean. And in precisely the same way, it's a farce to use our current "lack of evidence" as an argument that there isn't likely to be any life elsewhere in the universe.

This is why I say that it's a "dishonest" argument.