Anthropic means “relating to human beings or their existence.” Principle means “law.” The Anthropic Principle is the Law of Human Existence. It is well known that our existence in this universe depends on numerous cosmological constants and parameters whose numerical values must fall within a very narrow range of values. If even a single variable were off, even slightly, we would not exist. The extreme improbability that so many variables would align so auspiciously in our favor merely by chance has led some scientists and philosophers to propose instead that it was God who providentially engineered the universe to suit our specific needs. This is the Anthropic Principle: that the universe appears to have been fine-tuned for our existence.
Consider protons, for example. Protons are the positively charged subatomic particles which (along with neutrons) form the nucleus of an atom (around which negatively charged electrons orbit). Whether by providence or fortuitous luck (depending on your perspective), protons just happen to be 1,836 times larger than electrons. If they were a little bigger or a little smaller, we would not exist (because atoms could not form the molecules we require). So how did protons end up being 1,836 times larger than electrons? Why not 100 times larger or 100,000 times? Why not smaller? Of all the possible variables, how did protons end up being just the right size? Was it luck or contrivance?
Or how is it that protons carry a positive electrical charge equal to that of the negatively charged electrons? If protons did not balance electrons and vice versa, we would not exist. They are not comparable in size, yet they are perfectly balanced. Did nature just stumble upon such a propitious relationship, or did God ordain it for our sakes?
Here are some examples of how the Anthropic Principle directly affects the livability of our planet:
The unique properties of water. Every known life form depends on water. Thankfully, unlike every other substance known to man, water’s solid form (ice) is less dense than its liquid form. This causes ice to float. If ice did not float, our planet would experience runaway freezing. Other important properties of water include its solvency, cohesiveness, adhesiveness and other thermal properties.
Earth’s atmosphere. If there were too much of just one of the many gases which make up our atmosphere, our planet would suffer a runaway greenhouse effect. On the other hand, if there were not enough of these gases, life on this planet would be devastated by cosmic radiation.
Earth’s reflectivity or “albedo” (the total amount of light reflected off the planet versus the total amount of light absorbed). If Earth’s albedo were much greater than it is now, we would experience runaway freezing. If it were much less than it is, we would experience a runaway greenhouse effect.
Earth’s magnetic field. If it were much weaker, our planet would be devastated by cosmic radiation. If it were much stronger, we would be devastated by severe electromagnetic storms.
Earth’s place in the solar system. If we were much further from the sun, our planet’s water would freeze. If we were much closer, it would boil. This is just one of numerous examples of how our privileged place in the solar system allows for life on Earth.
Our solar system’s place in the galaxy. Once again, there are numerous examples of this. For instance, if our solar system were too close to the center of our galaxy, or to any of the spiral arms at its edge, or any cluster of stars, for that matter, our planet would be devastated by cosmic radiation.
The color of our sun. If the sun were much redder, on the one hand, or bluer, on the other, photosynthesis would be impeded. Photosynthesis is a natural biochemical process crucial to life on Earth.
The above list is by no means exhaustive. It is just a small sample of the many factors which must be just right in order for life to exist on Earth. We are very fortunate to live on a privileged planet in a privileged solar system in a privileged galaxy in a privileged universe.
The question for us now is, with so many universal constants and cosmological parameters defining our universe, and with so many possible variables for each one, how did they all just happen to fall within the extremely narrow range of values required for our existence? The general consensus is that we are either here by fortuitous luck against tremendous odds or by the purposeful design of an intelligent Agent.
Some proponents of the here-by-chance perspective have sought to level the odds against fortuitous luck by hypothesizing a scenario whereby our universe is just one among many in what has come to be termed a “multiverse.” This gives nature many more chances to “get it right,” bringing the odds against its success down significantly.
Imagine innumerable lifeless universes in which one or more of the necessary variables fail to fall within the specific range of values required for life. The idea is that nature would eventually get it right, and apparently has done so as evidenced by the fact that we exist (or so the argument goes). We are the lucky ones whose universe stumbled upon the right combination of cosmological values. The Anthropic Principle is often cited as empirical grounds for the otherwise mathematically hypothetical multiverse.
Intelligent Design theorists hail the Anthropic Principle as further evidence in support of their thesis that life was engineered by a transcendent Mastermind. Not only do biological systems bear the hallmarks of design (the information content of DNA, specified complexity, irreducible complexity, etc.), but the universe which supports and provides a context for life appears to have been designed as a means to that end.
I'll take two on:
Properties of water:
The properties of water are the result of the physical nature of the atoms from which it is made and the interconnections of those atoms to make the molecule H2O, and the interconnections between the molecules of H2O. You can say that the nature of the particles that make up the atoms that make up the molecule determines the physical properties of the substance and you would be correct.
The color of our sun and photosynthesis:
The color of our sun has nothing to do with photosynthesis other than the evolution of plants to take advantage of the color of the sun (which, by the way is more green than any other color). In the beginning of plant life there were other colors of plants and even today there are other colors of plants that have evolved to utilize different colors of the spectrum of the sun. For example there are reddish or purple plants that absorb and utilize more of the red component of sunlight, there are yellow colored plants that take advantage of the yellow component, and there are green plants that utilize the green components. As there is more green component most plants have evolved to utilize this color and are therefore green.
There is a theory that there is an infininte number of universes. Each universe is a probable outcome of an event, some have different physical constants, some have different physical properties, and some have similar constants and properties as our universe. Anything that can happen will happen in one of the universes therefore we could happen and therefore, at least in this one particular (and maybe others as well) universe, we did. This is the Many Worlds Theory, M-Theory, Brane Theory, and String Theory (to some extent).
I believe they are misinterpreting the anthropic principle.
First - their viewpoint only works IF mankind was the goal, not just the result. It is not that the world is so perfectly suited to our needs - it is that our needs developed as they did due to the nature of the world.
Second - the anthropic principle is also closely related to a few other theories, including the biocentric universe, and the limitations of our ability to perceive the universe. That is - we see universal constants as we do - not because they are necessarily so limited, but because it is all we can see.
One summary say it like this:
The anthropic principle states that this (the physical constants supporting life) is a necessity, because if life were impossible, no one would know it. That is, it must be possible to observe some Universe, and hence, the laws and constants of any such universe must accommodate that possibility.
But this is, ultimately a tautology, and not falsifiable.
For my own part, I feel like we are fish in a fishbowl who sees the room outside us (the observable universe) as warped (by our sensory organs and 4 dimensional understanding of the world), and has no concept of anything outside of the room (other dimensions) - it could be anything, and could totally change the nature of reality as we know it, but we have no access to that information.
Science gives us a method to explore what we have access to. Anything beyond that is currently not falsifiable, testable, or known - and must be taken as speculation only (albeit some speculation has better theoretical basis than others).
Ultimately we are left with the question: "why do the fundamental laws of physics appear to take the particular form we observe and not another?" - The anthropic principle, along with multiverse, m-theory and others attempt to provide some basis for forming an answer, but currently, I believe this is unanswerable by science.
No answers that have been provided by religion or philosophy, or metaphysics, have any means of testing the validity...so, I'm ok with "I don't know yet."
True. We percieve the universe as it exists because the universe exists such that we exist, therefore we exist and can therefore percieve the universe as it is. It is circular logic.
You really can't say that if the physical constants were different that some sort of life could not exist because that particular hypothesis isn't testable in our universe.
This reads like the old argument of the watch in the forest rather than antyhing new
Can you clue me in on that one?
The old diest argument. If you find a watch in the desert/forest, you wouldn't assume it happened naturally, you would say someone put it there. Same being for nature or man, why would we assume it just happened if we wouldn't assume the watch did.
I am SO FRUSTRATED. I just wrote a page on this, and got called away on the phone, and when I came back to add reply, my wife had killed the tab because the browser was taking up too much memory. Then I had to start killing tabs for the same reason.
I will try to be succinct because -- argh!
The part here I find value in is the part that is usually called the Anthropic Principle: there are certain constants in the universe, for example the gravitational constant G (something x 10^8 power IIRC -- I'll be damned if I'm looking up the numbers again -- in cgs), mass of a proton (1.67 x 10^-something big), strong nuclear, weak nuclear. Change one fo these by half an order of magnitude (factor of 5), and life cannot form. Not our life; any life. Change G slightly, and your stars can't form, or immediately collapse. Tweak a nuclear force (strong, I think) and no atom can form except hydrogen.
In the absence of info about why the constants take the values they do, we are left with the null hypothesis: all values equally likely. So the likelihood of a life-allowing configuration is approx 0. Take a smaller range, and the likelihood is still insignificant.
Dallas posted a short vid by Sagan saying that although the ancients thought the universe was constructed so as to support life (which it certainly does), we now know that the universe is clearly "Not Designed for Us." A bizarre conclusion from these indisputable facts: out of all the possible universes, almost all of them would have been clearly not designed for us, and we would not exist. We're in one of the few that is not clearly "Not Designed for Us." The ones that, if they existed, would be clearly not designed for us, coudln't have us, or any life, in them.
Here are the possibilities people have come up with for these constants' precise configuration:
* There are an infinite number of universes we can't know, and we're in one of the life-supporting ones. This is something we don't know, and can't know; we can only take it on faith, in the absence of any supporting evidence -- only a wish to believe.
* The constants had to take this configuration, for reasons we don't know.
* Other, which includes "Damned if I know."
I think this is not quite beyond the reach of science; maybe we can fidn a reason the constants had to be the way they are. If not... science can't answer things that happened before, or outside, the universe.
Other parts do not seem valid.
For example, that the sun is yellow. Lots of suns are yellow. It's hardly surprising that this one is; it's a common trait! You may as well be amazed that your parents met. If they hadn't, you wouldn't exist . . . but men and women meet and marry all the time. It's not surprising.
That the atmosphere must be as thick as it is or we'd be irradiated. It's actually the magnetic field that takes care of this.
...and if someone were to say, the dinosaur-killing comet that hit the Yucatan. If it hadn't struck, we wouldn't exist! True, I'd assume . . . but other life in other systems still could. Our own existence does not seem surprising to me, unless it were impossible or all but impossible. But the existence of life at all, in a universe that just happened to have things just right (water can form; carbon can form; stars can form; etc.), does seem surprising, delightful, and interesting.
The hypothesis that a universe that has different physical constants cannot support life is a null hypothesis, it is not testable in any way so it fails as a hypothesis. Such a universe with different physical constants and therefore different physics may be able to support life, but not as we know it. We're bound by the universe that we live in so much that we can't even imagine life in another type of universe. Talk about anthro-centric.
I can imagine a universe filled with nothing but energy that can support a life form made up of nothing but energy, in fact, in a way that is exactly what we are, nothing but energy. Our physical bodies are comprised of what can be called 'frozen' energy in the form of the particles that make up matter. The interactions between the particles is energy.
An awareness that atomic nuclei more complex than hydrogen depend on the strong nuclear force being strong enough to hold protons together is not a null hypothesis, and it most definitely is not "anthro-centric." "Molecule-centric," perhaps, but even if you hated molecules (!), it would still be true.
I think you misunderstand me. Yes the strong force and the weak force work together to form atoms, the electromagnetic force works to form molecules and so on. That is not to say that there wouldn't be other, similar forces working in the alternate universe such that life of some sort could arise. Not necessarily life as we know it but life none the less. But, we can't experiment here as all we have are the forces we have and can't determine what other forces may arise in such a universe. I.E. Not Testable either way.
Have a question for you Will.
Are you aware of anti-matter? Basically it is matter that has opposite charge of 'our' matter. It is available in this universe. Could you see a universe filled with anti-matter (matter being a very small percentage)? Do you think that life could exist there with all other physical 'constants' being the same? Charge would flow from positive to negative, anti-electrons would move in the opposite direction of electrons in a magnetic field , etc. But do you think life could exist in such a universe?