Sections
Everyone has their own take on things and their own nuances.
But on the other hand, the instructor doesn't think there is anything unusual or eccentric---just somewhat philosophical---like Omar Khayyam (1048--1123): see see the figure below (local link / general link: omar_reading.html).
See Carl Sagan (1934--1996) the figure below (local link / general link: carl_sagan.html).
Whole books are written about what science is: e.g., A. F. Chalmers' (1939--) What is this thing called Science? (1999).
And artworks often illustrate science: see the adjacent figure (local link / general link: vermeer_geographer.html).
But how about: Science:
The study aims at a complete understanding which includes being able to predict the evolution of systems of the objects to the past and the future insofar as intrinsic randomness allows.
The understanding is in terms of theories---whose statuses cover a large range:
Because science studies objective things there is an absolute gold standard---the objective things themselves---against which theories in science can tested.
This permits the scientific method---which is illustrated schematically in the figure below (local link / general link: sci_method.html).
In particular, note that though the objective things are a GOLD STANDARD, any particular experimentation/observation can LIE.
You should be as cautious about believing an experimentation/observation at the frontier of current understanding as about believing a SPECULATIVE scientific theory.
In many cases, experiments have to be confirmed, often many times, before you can be sure people arn't just making errors.
Think of cold fusion for example.
Some people thought they'd seen it for a little while before all the errors in their experiments were elucidated.
But on the other hand, "extraordinary claims require extraordinary evidence" quoting Carl Sagan (1934--1996): but others said similar things earlier: e.g., Marcello Truzzi (1935--2003)).
Science is thus PROGRESSIVE-TO-A-SINGLE-OBJECTIVE-GAOL in that it approaches an objective goal---the exact knowledge of objective reality.
Not all human endeavors are PROGRESSIVE-TO-A-SINGLE-OBJECTIVE-GAOL like science---NOT in the same sense anyway.
For example---an important example---art.
An artist may progress is realizing his/her vision.
Technique may progress: e.g., if you aim at painting with photographic realism, you can get closer.
But in general no: art is NOT PROGRESSIVE-TO-A-SINGLE-OBJECTIVE-GAOL.
For further elucidation, consider the figure below (local link / general link: lascaux_horse.html).
Context decides on which "system" is meant---as usual.
System and its special case physical system are explicated in the figure below (local link / general link: system_environment.html).
Of course, there can be systems of systems and whole hierarchies of systems.
In fact, everything is part of a hierarchy of systems.
For a big example, the Earth has a place in a hierarchy of physical systems as illustrated in the figure below (local link / general link: earth_hierarchy.html).
If the systems in a hierarchy of systems are natural systems, then usually they can analyzed using the concept of emergence.
We discuss emergence in section Emergence below.
Physics, in brief, is the science of matter and motion.
One way of dividing physics is into two broad fields: fundamental physics and applied physics:
Fundamental physics is the study of very general laws and very general results (which are derived from those general laws). The general laws and results can be more or less fundamental (more or less general) and are always (or almost always) expressible as mathematical formulae and they relate physical quantities: e.g., velocity, mass, energy, etc.
Having mathematical formulae means exact relationships exist at least as ideal limits that can be closely approached.
Applied physics which is the science of applying the general laws and results of physics to solving particular (physical) systems. The systems may be natural (e.g., stars) or artificial (e.g., lasers).
As an example of applied physics, see the animation of Archimedes' screw in the figure below (local link / general link: archimedes_screw.html).
The two fields---fundamental physics and applied physics---actually CANNOT be completely separated---there is NO hard line between them---for example, a result may straddle the line between being considered a very general result and just being the solution of an important special-case problem.
There is no hard line among people either:
Those relatively few physicists who work mostly in fundamental physics---they are the great brains---also often work in applied physics.
Often in astronomy, fundamental physics and applied physics are pursued with the same facilities---this certainly true in astronomy as illustrated in the figure below (local link / general link: vlt_laser.html).
An important goal of fundamental physics ever since physics emerged from general philosophy in Classical Antiquity is the search for the true, ultimate, really, really fundamental fundamental physical theory.
For a representative of ancient Greek philosophy, see Aristotle (384--322 BCE) in the figure below (local link / general link: aristotle.html).
Nowadays people tend to call the fundamental fundmental physical theory the Theory of Everything (TOE)---which is NOT a good name since the fundamental fundamental physical theory is NOT a theory of everything in the opinion of the herd yours truly follows.
For toes, see see the figure below (local link / general link: toe.html).
In fact, the usually-discussed TOE excludes the 2nd law of thermodynamics, and so is NOT even a theory of all physics.
The (usually-discussed) TOE is just the fundamental theory of fundamental particle physics (which includes quantum field theory). Now that's a lot, but it does NOT include 2nd law of thermodynamics (and so in a sense does NOT include thermodynamics).
So as shorthand, we will usually just say TOE-Plus for the grand-total fundamental fundmental physics theory which includes TOE, thermodynamics, and anything else considered physics.
But TOE-Plus is NOT really a theory of everything---in the opinion of the herd yours truly follows. We discuss more on this point when we discuss emergence below in the section Emergence.
Does TOE-Plus actually exist?
In a sense, TOE-Plus must exist since there must be some minimum set of physical laws that describe the part of reality marked off as fundamental physics---but there is no guarantee that the TOE-Plus will have only a few elegant axioms---but physicists hope so.
Do we have the fundamental fundamental physical theory (AKA TOE-Plus), a minimum set of consistent physical laws, now?
Overwhelmingly, most physicists would say NO for several reasons.
We discuss two such reason here:
A longstanding reason is that our best theory of gravity is Einstein's general relativity (see illustrative figure below: local link / general link: spacetime_curvature_earth.html), but general relativity is NOT consistent with quantum mechanics (the theory of microscopic particles) which is arguably the best verified of all physics theories---your cell phone and all modern electronics would NOT work if quantum mechanics were NOT a highly accurate theory.
Why don't we have an adequate theory of quantum gravity.
The region where quantum gravity is necessary to describe reality is very inaccessible experimentally as discussed in the figure below (local link / general link: gravity_two_spheres_animation.html).
We hope one day to access adequately that realm in some way.
We do NOT know what two basic ingredients of cosmology are.
We call these ingredients dark matter and dark energy---but those are names for our ignorance.
We only know some of their effects on cosmology, the large-scale structure of the universe, and galaxies.
From those effects, we can calculate, probably pretty accurately, the amounts of mass-energy of dark matter and dark energy.
Quantum field theorists have their reasons for thinking there is dark energy that is real energy form.
We take up dark matter and dark energy in IAL 30: Cosmology.
Now the effects of dark matter and dark energy are of fundamental importance, and thus so are dark matter and dark energy.
Since we don't know what dark matter and dark energy are, we obviously do NOT have TOE-Plus.
So the hunt for TOE-Plus continues---and hopefully when we find it, it will consist of a few elegant axioms---which doesn't mean that it will be easy to understand---they probably won't be easy to understand.
Form groups of 2 or 3---NOT more---and tackle Homework 0 problems 2--10 on science and physics.
Discuss each problem and come to a group answer.
Let's work for 5 or so minutes.
The winners get chocolates.
See Solutions 0.
Before trying to define emergence, it useful to say that emergence makes intelligible a very well understood fact:
So to a degree, everyone understands emergence even if they don't know the name.
One narrow definition from Wikipedia:
Emergence is the property of reality that there are important theories---important sets of rules---that are somewhat independent of other important theories and often hold in multiple contexts including imagined other realities.
These theories are exact in some ideal limit which in some cases can be reached trivially, in some cases can approached arbitrarily closely at least in principle, in some cases can approached pretty closely, and in some cases are only crudely reached in reality, but still give useful order-of-magnitude results or at least understanding.
A theory where NONE none of the above specified conditions holds is NOT an important theory and is usually useless.
These theories can be called emergent theories when you want to emphasis emergence, but otherwise just calling them important theories is best.
Emerging from the broad definition, there are two kinds of emergent theories:
However, emergent theories can switch from Kind 1 to Kind 2 in a logical sense though they remain Kind 1 in a historical sense since they were first discovered as Kind 1.
The switching process is actually pretty common in physics.
An important example is Newtonian physics which is historically Kind 1, but switched to logically to Kind 2 when it was found to be derivable from the theory of relativity: it is the low-velocity, low-gravity limit of the theory of relativity.
Another important example is classical electromagnetism: historically it is Kind 1, but it derivable from quantum electrodynamics which was discovered later in time.
Classical electromagnetism is illustrated in the figure below (local link / general link: maxwell_equations.html).
It's NOT very useful as an axiom since very little can be deduced from it alone.
The real work/fun is in obtaining important emergent theories:
Despite its lack of obvious use in developing theories, yours truly thinks yours truly's broad definition is a useful perspective.
It's relatively merit-based about important theories---it does NOT say everything is really physics or everything is really the misnamed TOE-Plus.
All of mathematics is sort of a grand heap of an emergent theory.
But to be general, yours truly likes to include it.
Of course, much of modern mathematics has very little application in understanding physical reality.
It's just part of conceptual reality---concepts are real things.
A trivial, artificial example of an emergent theory is chess---illustrated in the figure below (local link / general link: chess_animation.html).
One can make chessmen out of wood, plastic, or nothing---you can just play a game in your mind with some practice.
Chess does depend on 2-dimensional Euclidean geometry---and so in that limited degree depends on an aspect of physical reality---so it's NOT totally independent of physics---just mostly so.
What does chess emerge from?
A combination of random chance in the history of games and what human psychology thought of as making an interesting board game.
However, we can imagine chess or something very like it being developed by intelligent beings in other realms of existence.
Yours truly tends to agree with Michel de Montaigne (1533--1592) about chess.
One remarkable emergent theory---which is has arguably been proven empirically---is the scientific method---see figure below (local link / general link: sci_method.html). It should work in any rational reality---or so yours truly tends to believe.
Yours truly actually believes that the scientific method is proven theoretically in a sense by Bayesian analysis. However that is a long story which is we will NOT give though we discuss Bayesian analysis a bit in section Bayesian Analysis.
Note insofar as scientific method is proven by Bayesian analysis, it is NOT an independent theory, but is based on the mathematical logic of Bayesian analysis---so it emerges from deduction NOT as in independent aspect of reality.
Psychology, human and in general, is certainly governed by some emergent theory.
This emergent theory is clearly only partially understood---despite the efforts of the scientists and the sages---see figure below (local link / general link: confucius.html).
But in the opinion of many, we probably will someday, maybe even relatively soon.
After all our brains are made of physical components obeying the laws of physics and chemistry, and neuroscience uses those laws to understand the how the brain works.
But as we would now say, the brain is the hardware and the mind is the software physically realized in the hardware.
I think no one doubts there can be minds with quite different hardware: i.e., artificial intelligence (AI) and extraterrestrial intelligence.
And no one can rule out the possibility of intelligences in other realms of reality where the physics is quite different from our own.
Moreover, the particular laws of psychology obeyed by a particular intelligence would also depend on the historical development of that intelligence which is at least partially independent of physics.
The upshot of this discussion is that the laws of psychology are independent to a large degree from physics.
They do constitute an emergent theory as aforesaid.
Evolution (by natural selection) certainly happens to physical bodies.
We deduced laws of evolution (including the laws of heredity) from observations of biota. The actual origin of life is still far from fully elucidated---but there's hope.
But the laws governing evolution are independent of physics.
One can imagine evolution applying to entities in other realms of reality with different fundamental physics.
Evolution is an emergent theory.
We know it is true as a procedure because it works on the computer.
The theory of evolution by natural selection in computer calculations is used to find optimum solutions to problems where one treats the solutions as breeding entities.
The techniques are called the genetic programming method and the genetic algorithm method.
Both techniques have seen considerable development and may well become even more important than they already are in scientific research, design, and solving everyday problems.
In fact, genetic programming large language models (LLMs) have combined to make a very powerful solution finding technique (see Jean-Baptiste Mouret, 2024, Nature, "Large language models help computer programs to evolve"; Alhussein Fawzi & Bernardino Romera Paredes, 2023, "FunSearch: Making new discoveries in mathematical sciences using Large Language Models).
Some would argue that the theory of everything (TOE) is the example par excellence of a NON-emergent theory---the theory from which every other theory applying to physical reality can be derived.
But yours truly like to think of TOE as just another emergent theory.
A good reason for thinking this way is that there may be regions outside of the observable universe where different "TOEs" apply.
But even if we found the truly "universal TOE" it would still just be emerge from reality like other emergent theories.
In any case, yours truly would still likes to call TOE an emergent theory (using the broad definition) since yours truly thinks of it as a Platonic ideal and does NOT like singular exceptions to the rule that all important theories are emergent theories.
Some other semi-relevant considerations:
There is an important fundamental physical law which everyone agrees is part of physics---the 2nd law of thermodynamics which we discuss in the next subsection---which everyone admits is independent of TOE as usually discussed.
Those emergent theories still exist as Platonic ideals even if their application our reality required random events.
The 2nd law of thermodynamics is universally acknowledged law of physics:
The maximum entropy state is thermodynamic equilibrium---which is a timeless state at the macroscopic scale---nothing is changing---temperature, pressure, phase, heat energy content, etc. are NOT changing---and temperature is uniform---temperature is a measure of thermodynamic equilibrium among other things.
At the microscopic level, atoms and molecules are moving around, but that has NO macroscopic effect.
In fact, thermodynamic equilibrium is a dead state. Parts of living organisms are in thermodynamic equilibrium, but overall they CANNOT be that and be alive.
The 2nd law of thermodynamics has been called entropy arrow of time since the 2nd law of thermodynamics is one of the few time-asymmetric physical laws (see Wikipedia: Entropy as an arrow of time).
We can also imagine the 2nd law emerging in alternative realities with alternative physics. In fact, it is hard to think of a complex alternative alternative reality (one consisting of large numbers of entities) where it does NOT hold.
Recall, I used the nonce word TOE-Plus to include the totality of physics including the 2nd law of thermodynamics.
Also in fact, it is hard to think of a living room where 2nd law does NOT hold in a qualitative sense. If you just let everything fall where it will in your living room, you would soon be living in a state of maximum entropy: i.e., total squalor.
Achieving total squalor in Japanese living room might take awhile. See the figure below (local link / general link: living_room_japanese.html).
One aspect of the quantitative nature of 2nd law of thermodynamics is that entropy (in an exact physics) is precise measure of messiness in physicsy sense---the most concise formula for entropy is simple enough---see tomb of Boltzmann in the figure below (local link / general link: ludwig_boltzmann.html).
You can make a reverse heat energy flow (e.g., in refrigerators), but that takes outside manipulation.
Stars are providing a flow of heat energy in the form of electromagnetic radiation (i.e., photons) to space.
In our current understanding of cosmology, the stars will NEVER succeed in heating up the physical components of space (particles and electromagnetic radiation (EMR)) to stellar temperatures on average.
Emergence and emergent principles are, in fact, everywhere.
When you think about it, you always knew it.
So the neither theory of everything (TOE) nor TOE-Plus is a theory of everything.
Recall TOE is really a theory of particle physics independent of all natural history.
Now TOE, it is reasonable to say, sits at the bottom of The Hierarchy of the Sciences (see section The Hierarchy of Sciences below), but building up the rest of the hierarchy needs a whole lot of emergence involving all kinds of other laws (e.g., 2nd law of thermodynamics evolution by natural selection) which seem just as fundamental to the herd yours truly follows.
From the point of view of emergence, TOE is NOT the only fundamental set of laws---there are lots of others.
We won't do that much in the lectures, but we should keep emergence in mind.
To finish, I emphasize that the above discussion is somewhat idiosyncratic to the instructor.
Others might put things differently or disagree, but I do NOT think my view on emergence is eccentric. I believe, I'm just following a herd.
In fact, in yours truly's opinion Bayesian analysis is the scientific method quantified and the proof of the scientific method. See subsection Bayesian Analysis and the Scientific Method below.
It finds a lot of use in many sciences: e.g., cosmology, economics, epidemiology, medicine, particle physics, psychology, sociology, etc.
So it's an important science topic and we do NOT discuss it elsewhere in IAL---and this is the philosophical-historical-tragic-comical-poetical introduction to astronomy and science in general---and some students will encounter it sooner or later---and so we discuss it here.
In detail, it's hard to understand---but we won't do that---and hard to apply---but there are computer packages.
Bayes' theorem is really simple: it is easier to prove than to remember.
It is a relation between P(A|B) and P(B|A). To explicate:
P(AB) = N_(AB)/N = [N_(AB)/N_(B)]*[N_(B)/N] = P(A|B)P(B) ,where N is all events. But clearly
P(AB) = N_(AB)/N = [N_(AB)/N_(A)]*[N_(A)/N] = P(B|A)P(A) .Thus Bayes' theorem
P(AB) = P(A|B)P(B) = P(B|A)P(A)or asymmetrically
P(A|B) = P(B|A)P(A)/P(B) or P(B|A) = P(A|B)P(B)/P(A) .And that's all there is to it.
So, for example, if you know P(B|A), P(A), and P(B), you know P(A|B).
Bayes' theorem is simple. Bayesian analysis is NOT. So we won't expand on its mathematical detail here.
But it is used to judge the probability that theories are true as aforesaid.
What the Devil you say. Isn't a theory true or NOT?
For Himself, see the figure below (local link / general link: dore_satan.html).
But Bayesian analysis deals in truth to your knowledge.
If yours truly flips a coin and hide it under a hand, is it heads or tails?
In an absolute sense, it's one or the other and yours truly even knows it which it is.
But to your knowledge it's fifty-fifty.
Bayesian analysis allows you to estimate---and in practical cases, it is almost always just an estimate---the probabilities of theories.
But Bayesian analysis is NOT just a one-off.
It is a way of updating the probabilities of theories using Bayes' theorem.
In fact, there is nothing unusual about updating the probabilities of theories.
Qualitative Bayesian analysis is what every one has done forever---"This is probably true based on everything we know now." etc.
But actual Bayesian analysis has a lot more math and computer number crunching to it.
The updating probabilities of theories by Bayesian analysis is, in fact, how the scientific method is quantified by Bayesian analysis. The fact that in the ideal limit Bayesian analysis should lead to true theories is the proof of the scientific method. Yours truly explicates the updating procedure and the proof of the scientific method in An Educational Note on Bayesian Analysis.
Bayes' theorem was discovered in the 18th century and many of the basic techniques of Bayesian analysis were worked out in the 1950s by Sir Harold Jeffreys (1891--1989).
To explicate, Bayesian analysis is most useful when you have theories A that only make statistical predictions. Then you accumulate large sets of data B (e.g., petabytes or exabytes) and calculate P(A|B). The storing and calculating requires lots of computer power.
The conditional probabilities P(A|B) allows you to rank the theories A and hopefully eventually come to a conclusion which theory A is true.
Using Bayes' theorem, you update your probabilities as more data is accumulated.
As aforesaid, Bayesian analysis finds a lot of use in many sciences: e.g., cosmology, economics, epidemiology, medicine, particle physics, psychology, sociology, etc.
The need for Bayesian analysis was less in the old days when there were easier things to discover requiring simpler and fewer theories and much smaller data sets.
A further explication of Bayesian analysis is given in the aforementioned An Educational Note on Bayesian Analysis.
In cosmology, we have a wealth of accurate/precise data compared to what we had before circa 1992---we call our time the golden age of cosmology or the age of precision cosmology.
But there are quasi-endless cosmological models that fit the data more-or-less well. The data is mostly statistics and the cosmological models predict a probability of obtaining those statistics.
How does one rank these cosmological models in order of likelihood?
Using Bayesian analysis. It gives us P(A|BK): the probability of cosmological model A given statistics B and background knowledge K.
Alas, many uncertainties come into all Bayesian analysis, and so the ranking of cosmological models is NOT decisive so far. But at least it suggests which models are favored, and so are worth further development.
For some time, the Λ-CDM model (AKA concordance model) has been more-or-less top dog, but no one would be too surprised if it was outranked someday.
For a top dog, see the figure below (local link / general link: wolf.html).
We discuss it in here in IAL 0 because it's a bit philosophical and does NOT fit anywhere else in IAL.
The term anthropic principle was coined in 1973 though the idea of such a thing goes back to 1904 (see Wikipedia: Anthropic principle: Origin) and perhaps earlier in a vague sense.
The anthropic principle has been controversial: some argue that it is trivial or worthless as a scientific principle.
Part of the problem is that there are different versions of anthropic principle (see Wikipedia: Anthropic principle: Variants).
However, it seems a basic anthropic principle has gained traction and is of some importance in modern astronomy and physics.
Put as an aphorism, the anthropic principle states:
See Orson Welles (1915--1985) observing in the figure below (local link / general link: orson_welles_chimes_at_midnight_a.html).
The essence of the anthropic principle is "we exist" = A implying B must exist. Put mathematically, we have A and we know P(A|[not B]) = 0, and so B exists: i.e., P(B|A) = 1. There is a bit more mathematical description and the connection to Bayes' theorem in the A-principle file.
What's B? Any of a vast number of things that are necessary for us. We'll give some examples below.
But "we exist" = A can be specified more precisely. Possible A values roughly in order of increasing generality are:
Interestingly, there is historically a forerunner of the anthropic principle in Aristotelianism. To explicate, Aristotelianism considers A to be a final cause of B since B exists, among other things, to make A possible.
This Aristotelian teleological point of view is useful in some contexts (e.g., things designed by intelligence or evolution), but probably NOT many others.
An example from evolution is that animal flight (i.e., A) is the final cause of wings (i.e., B).
In the subsection below, we give an example of the application of the anthropic principle.
There were more examples once, but enough is enough.
Probably the most famous example of the use of anthropic principle was in the discovery of the triple-alpha process in 1952.
Recall, the term anthropic principle was coined in 1973. So only retrospectively has the term been applied to this discovery.
The story in point form:
In 1952, the Big Bang theory (then very rudimentary compared to today) and the steady state universe were considered the most---maybe the only---viable cosmological models.
In other words, an anthropic principle argument argued for the triple-alpha process---and, as aforesaid, this was before the expression anthropic principle was coined in 1973 (see Wikipedia: Anthropic principle: Origin).
The properties of the winners of a lottery are quasi-unique due to random peculiarities, but there are always winners of a lottery.
The foregoing in yours truly's opinion shows that the anthropic principle is a useful scientific principle.
Given B (something related to technologically advanced human society as we know it), we can explain in a sense the existence of A if P(B|not A) = 0 or P(B|not A) is close to 0.
The sense being that:
The anthropic principle also sometimes allows you to infer the existence of A even if you didn't know that A existed before. So it can be a discovery tool as famously shown by the discovery of the triple-alpha process (see the above section Anthropic Principle Example: The Triple-Alpha Process).
If you extend the anthropic principle with Bayesian analysis, then you may be able to estimate the conditional probability P(A|B) and decide whether A is likely to exist and be worth looking for if you do NOT already know of it.
There are criticisms of the anthropic principle (Wikipedia: Anthropic principle: Criticisms), but yours truly thinks those are mostly directed toward more extravagant claims for it than those discussed here.
In IAL, we occasionally refer to the anthropic principle.
The branch theories can be regarded as approximations to the exact fundamental theory of physics, theory of everything (TOE), which is as yet unknown, PLUS important some emergent principles (e.g., 2nd law of thermodynamics)---recall yours truly calls this grand-total fundamental fundemental physics theory TOE-Plus faute de mieux.
But following the herd yours truly follows---which includes one of yours truly's gurus, Robert Laughlin (1950--) (see Laughlin, 2005, p. 31)---the truer perspective is to view the branch theories as exactly true emergent theories.
More than yours truly would like to give now.
But yours truly could say that it seems to yours truly the more fruitful perspective for yielding scientific progress in physics.
It also is the perspective that is more general in that allows the branch theories to fit into the general category of emergent theories. "More general" is often taken to be "truer" in science.
But you can often get very close to those limits and often very easily. So close that often NO discrepancy between experiment and branch theory can be detected.
The great exactness of the branch theories is extremely valuable. It is what has allowed how great progress in understanding the universe and in developing technology---despite NOT having TOE-Plus.
In fact, we can repeat ourselves and say---going beyond physics----that emergence allows us to understand much about reality without having to know everything about reality.
The 2 figures below (local link / general link: physics_branches.html; local link / general link: physics_branches_related.html) illustrate schematically the relationships of the branches of physics.
There are many other ways of dividing physics up into fields and sub-fields.
We are NOT going into all that.
Where does astronomy fit in to physics.
Nowadays almost everyone agrees that astronomy should be classified as a field of physics.
Rather astronomy makes uses of all branch theories discussed above plus a lot of other physics theories of a less-grand sort---in fact, it uses pretty much all the physics we know.
It applies these theories to the study the large objects of the universe and many of their smaller constituents too.
But astronomy is also fundamental physics since it includes cosmology: the science of the universe as a whole on large scales.
Cosmology is partially applied physics, but it also fundamental physics because it is, among other things, about the reality out of which all physics arises.
In fact, it seems likely that cosmology and TOE are so deeply connected that one CANNOT be fully understood without understanding the other. We will NOT go into why at this moment.
The figure below (local link / general link: cosmos_history.html) is a preview of cosmology which we take up in IAL 30: Cosmology.
Form groups of 2 or 3---NOT more---and tackle Homework 0 problems 7--14 on physics, emergence, and physical sciences.
Discuss each problem and come to a group answer.
Let's work for 5 or so minutes.
The winners get chocolates.
See Solutions 0.
The point in doing so is to understand how the sciences are related.
But to reiterate the theme of the section Emergence, there are many important emergent theories which emerge from reality and are at least somewhat independent of each other, and so the bottom of the hierarchy does NOT dictate everything else in it.
Yours truly orders, very undefintively, the sciences in the hierarchy:
Why this ordering?
However, as one goes up the hierarchy, historically there were fewer emergent principles that were mathematical in formulation. But there has been advances making the originally non-mathematical emergent principles mathematical or at least more precise, and thus more like mathematical formulations.
Then physics generally since the branches of physics follow directly from TOE-Plus.
What changes going up the hierarchy above physics? Less dependence on physics and more on emergent theories that are NOT classified as physics.
The transition from physical sciences to the life sciences is a key point for "less dependence on physics" at least in the judgment of tradition.
Nevertheless, the life sciences do depend on physics and there is even a well defined field of physics called biophysics.
Old-fashionedly, one would say there is really a lot "less physics" when you get to psychology. For example, just try deriving the Oedipus complex from physics alone---a very uncomfortable proposition. For the Oedipus complex, see the figure below: local link / general link: sigmund_freud.html).
However, in the modern age, biophysics is playing a role in neuroscience, and thus in psychology.
But these fields have their own emergent theories which are, however, often rather subjective---but there is a valiant attempt to make history a mathematical science---see the figure below (local link / general link: historia.html).
Maybe one day, history will be considered a science without qualification---and an art with a bit of qualification.
In the broadest sense, astronomy is the study of all extraterrestrial phenomena and some terrestrial phenomena too.
Earth is a planet, and so, qua planet, is a fit subject for astronomy.
Astronomy and mathematics have always been closely allied since astronomy makes deep demands on mathematics---predicting eclipses, etc.---and mathematics often progressed in response to those demands.
In fact, up to just a bit later circa 1600 the leading astronomers, mathematicians, and astrologers were often the same people and the terms astronomer and mathematician were often considered synonyms and also often considered synonyms for astrologer.
Why did astronomers and mathematicians and people believe in astrology? It was so ancient and offered an explanation for all the crazy things people do. And for astronomers, it paid the bills.
But there were always people including many astronomers who didn't believe in astrology or believed it was demonic.
Johannes Kepler (1571--1630), a leading astronomer and mathematician of the Scientific Revolution (c.1543--c.1687), is a transitional case: he started out with a profound belief in astrology while admitting its practice was often fraudulent, but by the end of his life seems have just seen it as a way to pay the bills.
Galileo (1564--1642), on the other hand, never believed in astrology---but he was required to teach it since it was required for medical students. Just ask yourself, would you trust a doctor who couldn't prescribe for you based on your horoscope.
After 1800, there was a bit of a parting of the ways, and only a fraction of mathematicians remained astronomers.
Certainly, after circa 1800, leading mathematicians stopped being leading theoretical astronomers. The mathematicians abandoned us.
Examples of people who were both leading astronomers and leading mathematicians are Ptolemy (c.100--c.170 CE) (the greatest theoretical astronomer of Classical Antiquity: see figure below: local link / general link: ptolemy_armillary.html), Omar Khayyam (1048--1123), Isaac Newton (1642/3--1727) (see figure below: local link / general link: newton_principia.html), Pierre-Simon Laplace (1749--1827), and Carl Friedrich Gauss (1777--1855).
Astronomy is often cited as the oldest, empirical exact science---empirical meaning based on observation---exact meaning using quantitative measurements.
This is all just point of view.
How old is astronomy as an exact science?
In a very elementary way, it may go back tens of thousands of years in the Paleolithic. For some explication, see the figure below (local link / general link: sapien_neanderthal.html).
Many ancient cultures all over the world constructed such astronomical monuments.
The most famous is Stonehenge---see the figure below (local link / general link: sullivan_stonehenge_003_remains.html).
In alignment astronomy, you just record where objects rise or set over the horizon as seen from some specific place: e.g., the center of Stonehenge.
Note the Stonehengers (AKA Neolithic Britons) were NOT literate, and so could NOT record their sky lore any other way, but in astronomical monuments.
Stonehenge and other astronomical monuments from around the world were almost always NOT observatories. They probably served multiple cultural functions and recording sky lore was probably a minor function in most cases.
For the alignment astronomy (probable and unlikely both) embodied in Stonehenge, see the Stonehenge map in the figure below (local link / general link: stonehenge_map_refined.html).
On the other hand, the literate ancient Mesopotamians---Sumerians from sometime in the 3rd millennium BCE and Babylonians from roughly the early 2nd millennium BCE until circa the 2nd century CE---have left extensive astronomical texts of observations and calculations.
The most advanced of the texts come from circa 400 BCE--circa 100 CE (Neugebauer, 1969, p. 30).
The texts are on clay tablets. See the exmaple in the figure (local link / general link: sumerian_gods_tablet.html).
Such predictions are presented in ephemerides (singular ephemeris) which are tables of predictions.
What of Babylonian physical/philosophical cosmology? See the figure below (local link / general link: babylonian_cosmos.html).
The ancient Greeks (circa 600 BCE--circa 400 CE) also practiced astronomy and---as you might have guessed---invented various philosophical and mathematical models of the cosmos.
For Ancient Hellas (AKA Ancient Greece) illustrated by the Acropolis of Athens, see the figure below (local link / general link: acropolis.html).
Of course, almost nobody else in the world had heard of Aristotelian cosmology until after circa 1800.
See the cartoon of Aristotelian cosmology in the figure below (local link / general link: aristotle_cosmos.html).
The eventual main competitor was the geocentric Ptolemaic system of Ptolemy (c.100--c.170 CE).
Ptolemaic system was in many respects based on Aristotelian cosmology, but Ptolemy described the motions of the astro-bodies using epicycle models (which we will describe in IAL 4: The History of Astronomy to Newton) rather than with compounded celestial spheres, but he still kept the celestial spheres for other purposes at least in some fashion.
The Ptolemaic system did give pretty accurate predictions of celestial motions for its day (unlike Aristotelian cosmology which was at best gave qualitative predictions) and Ptolemy and his true disciples believed that it was at least approximately a viable physical model of the cosmos.
However, the pure Aristotelians argued that the Ptolemaic system was essentially a mathematical calculational device and NOT an actual physical model of the cosmos---and they were largely right about that---but they were largely wrong in believing Aristotelian cosmology had more physical content.
For many centuries up to into the 17th century, it seems that Aristotelian cosmology and the Ptolemaic system managed to coexist even within individual minds albeit uneasily.
In the course of the 16th and 17th centuries---which is the time of the Scientific Revolution (c.1543--c.1687)---we have the transformation from Aristotelian cosmology and the Ptolemaic system to the Copernican heliocentric solar system and then to the quasi-infinite universe of Newton---see the figure below (local link / general link: newton_apple.html).
Certainly, in Aristotelian cosmology and the Ptolemaic system, the physics of Earth and the Heavens are different.
We CANNOT do experiments on stars, galaxies, etc.
But experiments on Earth do reveal aspects of the physics of outer space.
In fact, the unification of terrestrial and celestial physics is what has vastly increased the intelligibility of the universe.
Further astronomy history can be found in IAL 4: The History of Astronomy to Newton and, of course, Wikipedia's History of Astronomy.
Form groups of 2 or 3---NOT more---and tackle Homework 0 problems 11--17 on emergence, physical sciences, and astronomy.
Discuss each problem and come to a group answer.
Let's work for 5 or so minutes.
The winners get chocolates.
See Solutions 0.