Introduction

Structure
Evolution
Observation
Theory
Cosmic Table
Nature Outlooks

Structure

A structure is made up of interrelated parts functioning as an orderly whole. It is synonymous to the definition of a system. It implies that a force is present to hold all these parts together. There are four kinds of forces in nature:

The gravitational force holds together massive objects in various astronomical systems and makes us earthbound.
The electromagnetic force operates on objects carrying electrical charges.
The weak force, which is responsible for beta decay of the nucleus, operates on microscopic objects in short range.
The strong force, which holds the nucleons together in the nucleus, is stronger than the weak force.

While the gravitational and electromagnetic forces are long range, the weak and strong forces are dominant in the realm of

nuclei and even smaller particles. Note that the origin of friction, viscosity, elasticity, chemical bonding is electro- magnetic in nature. The internal structure of matter shields the electromagnetic force resulting in a residual force, which is weaker than the original. Similar shielding also occurs in the atomic nuclei resulting in a residual nuclear force.

The various structures in the universe are somewhat like a Russian doll. A larger size member would contain smaller ones in decreasing sizes (each with its special properties). However, while the relationship is "one to one" within the Russian doll, the hierarchical relationship is "one to many" in the cosmos. For example, the cosmos contains many superclusters, a supercluster contains many clusters of galaxies, a cluster of galaxies contains many galaxies, and so on. The Russian doll is just a special case of the general hierarchical organization.

Evolution

Evolution is the gradual development of a system from one form to another. For astronomical and biological systems it takes billions and millions of years respectively for their development into the present form. The history of modern science is simply too short to record the changes to these systems. However, with the aid of advanced observational technology, the evolutionary history of the cosmos can be reconstructed from astronomical objects in different stages of development. For the biological evolution, the fossil records and DNA comparison offer some helps to trace the evolution. In the absence of direct evidence, theory often offers some clues. There is no definitive answer to the cause

of formation of orderly or complex structure from a seemingly homogenous environment. One scenario suggests that the initial requirement is the creation of fluctuation to move away from an equilibrium state . Such an open system would exchange matter and energy with its surrounding. Under certain circumstances, the open system reaches a steady state in which it is far from equilibrium and maintains that way as long as there is enough energy to support this naturally "improbable" arrangement. Living organism returns to dust (an equilibrium state) when there is no food (energy) to support the chemical activities within the body.

Observation

Of the five senses in human to receive information about our environment, the sense of sight is the most important. Seventy percent of our sense receptors are devoted to the detection of light. This is not surprising in view of the dominant influence of Sunlight in our life. However, Sunlight occupies only a very small part of the electromagnetic spectrum which could shed information on various objects over the entire range (of the spectrum). It was only in the last hundred years that we were able to construct detectors for the retrieval of such information. Meanwhile we have also built telescopes to view distant

objects and microscopes for investigating the very small. Observation of astronomical objects can now be carried out in space to bypass the atmospheric effects such as infrared absorption, air turbulence, and overcast sky etc. Experiment is a special kind of observation when the objects can be controlled by human manipulation. It can yield knowledge not obtainable in the natural environment. Some phenomena such as the quantum uncertainty, and time dilation cannot be attributed to the poor quality of instrument. They are inherent in natural.

Theory

A theory is a proposition either in plain language (as in Darwin's Theory of Evolution) or in mathematical formulation (as in Quantum Theory). It is used to explain phenomena related to an area of study such as living organisms or atomic particles. It should be valid for all the phenomena in that area plus it has to make verifiable predictions. Even one tiny deviation would raise doubt on the theory, a few more inconsistencies would put it out of business.

There is always some gray areas, for which a theory is unable to explain. It can be due to the lack of data (as in the case of origin of life) or incomplete observation (as in the case of dark energy). As more evidences are gathered, a theory may be modified or expanded to accommodate the new facts. Thus, a scientific theory is open-end, there is no such scientific theory as the final or ultimate theory, at least not yet.

The quality of theory varies, e.g., the quantum theory is based on a more solid footing in the form of mathematical formulation, while Darwin's theory has drawn a lot of criticisms because it can be subject to different interpretations. It is only recently that the Evolution Theory is backup by the more objective DNA sequence.

Some people feel very comfortable by invoking a higher being to explain the unknowns. However, it is just an illusion. It just shifts the problem of explaining to somewhere else. We could keep on asking the same kind of endless interrogations like what is such being? How and where were they created etc.? unless we return to the idea of religion and appeal to an absolute authority without beginning and without end.

While the Eastern culture emphasizes a holistic approach to view the world (see I-Ching), reductionism has been an important thinking in the West ever since Aristotle who mapped out sciences and formulated logic. This approach breaks up complex phenomena into pieces. It tries to understand the behavior of the whole from the properties of its parts. It greatly simplifies the investigation without the complication of external interference. The superscript in column one of Table 01-01 indicates how the universe is partitioned into different fields of study, which are further divided into various sub-fields. Theories in these various domains are often incomplete in the sense that there are parameters, which have to be measured. They may be explainable by the theory in the next level, but the parameters are seldom calculable due to mathematical complexity.

They are called effective theories, and invariably become invalid at smaller length (size) scale. The method to address this kind of problem is called "renormalization". Ideally, the ultimate one associated with the smallest length scale (the Planck length) should be self-contained, it is sometimes referred to as the primary theory (or theory of everything). It will not need external inputs and shall be able to explain all the effective theories. Conversely, the whole becomes not merely more, but is very different from the sum of its parts. It is referred to as the emergent phenomenon, which possesses special properties such as: radical novelty, coherence, supervenience (derived from something), self-organization, manifestation at global or macro level, and the capability to evolve - the living world is a good example.

The scientific tools include measurement, analysis, inference, logic, hypotheses, and theories. Since Isaac Newton invented calculus in the 1690s, the development of differential equation for various physical systems has become a powerful tool for theoretical physicists who are very creative in modeling. For example, the entire galaxy is

considered to be a particle in cosmological model. This is justifiable as long as the size is much smaller than the distance between the objects. Modeling is used to simplify the system in order to arrive at a solvable equation. It usually involves making an assumption; then works out the consequence, which is finally verified by experiment or observation.

The equation should be constrained by invariance under certain operations such as time flow, space displacement, ... Otherwise, there would be just too many choices making it very difficult to select a correct one.
The system is known at certain point in space as well as in time - the so called boundary condition and initial condition.
The parameters in the equation can be adjusted to fit a corresponding physical system. It would be even better if the parameters can be derived from a more fundamental theory.
It offers verifiable predictions.
It passes all tests without exception in its domain of study. Older theory (e.g., Newton's Laws) may not be entirely invalid. It is just superseded by a more general theory (e.g., the General Relativity) applicable to more extensive scope.

It turns out that only linear equation (an equation appears in first degree only for the dependent variable and its derivatives) is suitable for isolated system as envisioned by the method of reductionism. In case it is applicable, it becomes a very efficient tool for compression, which would encrypt voluminous information into a few equations. Nonlinear equations can simulate some complicated systems

in the "real-world", but seldom offer solution in simple form. Other branches of science (such as biology), which are not susceptible to this kind of treatment, have to rely on terminology to shorten the description. Unfortunately it is very difficult for the layman to decrypt the compression, and it has become a communication barrier^¶ between science and the outside community.

^¶Jonathan Knight, Scientific literacy: Clear as mud, Nature 423, 376-378 (2003) - (see reprint)
The problem of reading science papers is getting worse according to a 2017 Nature article : "Science Papers Are Getting Harder To Read" after 14 years's of the same kind of criticism in 2003.

Cosmic Table

There are fifteen topics in this webpage including the Introduction. Following is a table to summarize the remaining fourteen topics, which are ordered in decreasing size of the structure. The table displays the averaged size or a range in size of the structure, the mass or energy of the individual object, the epoch of first appearance (the zero time is at the moment of the Big Bang), the dominant force in holding the system together, and the associated physical phenomena. Since the data involve very large and very small numbers, they are presented in power of ten. For example, 1000 = 10³ and 0.001 = 10^-3 (refer to "Units and Constants" for more information about unit conversions and universal constants). The epoch of first

appearance reflects the evolution of three groups of objects. The first group contains objects of small size from elementary particles to molecules (the micro-world); their evolution occurred at the beginning of the universe. The second group is represented by astronomical objects from stars to superclusters (the macro-world). It is believed that these objects evolved in the "bottom up" process in which smaller units merge and form larger units. Life on Earth belongs to the third group (the living-world including Earth and the organisms living on it), which materialized only recently (on astronomical scale) in the last 4.5 billion years.

Topic	Size	Mass/Energy	First Appearance	Force and Phenomena
Macro-world
Observable Universe^a	1.3x10²⁸ cm ~ 4000 Mpc. (cosmic horizon)	4x10²² M_sun (including dark energy, ordinary and dark matters)	0 sec.	Gravity + Unknown repulsive force; an expanding space in the last 13.7x10⁹ yrs, containing all the mass/energy of this world
Superclusters^a	10²⁶ cm.	10¹⁶ M_sun	11x10⁹ yr.	Gravity; largest scale of lumpiness
Clusters of Galaxies^a	10²⁴ cm.	10¹⁵ M_sun	6x10⁹ yr.	Gravity; galaxies in orbit around each other + dark matter
Galaxies^a	10²² cm.	10¹¹ - 10¹⁴ M_sun	7x10⁸ yr.	Gravity; aggregation of stars, gas, dust and dark matter
Star Clusters^a	10²⁰ cm.	10² - 10⁶ M_sun	5x10⁸ yr.	Gravity; group of stars originated in an interstellar cloud
Planetary Systems^a	10¹⁶ cm.	0.1-100 M_sun	1.8x10⁸ yr.	Gravity; system of non-luminous bodies as by-product in stellar formation
Stars^a	10¹¹ cm.	0.1-100 M_sun	1.8x10⁸ yr.	Gravity; contracting lump of gas with luminosity maintained by nuclear burning
Earth^g	10⁹ cm.	6x10²⁷ gm.	9.5x10⁹ yr.	Gravity; a planet in the habitable zone of the Solar system
Living-world
Multicellular Organisms^b	10⁴ - 10^-1 cm.	10⁷ - 10^-3 gm.	13.5x10⁹ yr.	Residual Electromagnetic force; organisms composed of multiple cells
Unicellular Organisms^b	10^-1 - 10^-4 cm.	10^-3 - 10^-12 gm.	10.5x10⁹ yr.	Residual Electromagnetic force; one cell living unit
Micro-world
Molecules^c	10^-5 - 10^-8 cm.	10 - 10^-3 ev.	3.8x10⁵ yr.	Residual Electromagnetic force; structure formed by combination of atoms
Atoms^c	10^-8 cm.	10 ev.	3.8x10⁵ yr.	Electromagnetic force; system of electrons and nuclei
Nuclei^p	10^-13 cm.	10⁹ ev.	1 sec.	Residual strong force; system of neutrons and protons
Elementary Particles^p	10^-16 cm. >	10^-3 - 10¹² ev.	< 10^-32 sec.	Weak, strong and electromagnetic forces; basic constituents of matter and force

Table 01-01 The Cosmic Table

Note 1 - Field of Study: a = astronomy, b = biology, c = chemistry, g = geology, p = physics.
Note 2 - The Mass M and Energy E are related by the formula E = mc².
Note 3 - 1 M_sun = 2x10³³ gm., 1 ev = 1.77x10^-33 gm.
Note 4 - The energy in "Atom" and "Molecule" refers to the binding energy, which holds the system together.
Note 5 - points to a webpage of that subject.
Note 6 - See animation on "Scale of the Universe".
Note 7 - See a video on "History of the Universe" in one minute.

	Nature Outlooks
[click to link]

This is a link to a very special publication from the Nature magazine. In their own words :

Nature Outlooks tackle topics of scientific, clinical and societal interest, giving a comprehensive picture of the current state of knowledge and the hottest areas of research. They present news features written by top science journalists and commentary pieces from leading academic and industry thinkers. A Nature Outlook might focus on a disease, technological innovation or a field of particularly intense scientific progress. Outlooks target a generalist, scientifically literate audience, while maintaining Nature's strong evidence-based editorial values. As such, Outlooks offer a unique opportunity for sponsors to report their scientific advances in the pages of Nature alongside relevant, independent and accessible content.