Archive for the ‘Universe’ Category

The “big bang” was not an exploding ball of matter

January 13, 2008

Popular accounts of the big bang often describe it as the detonation of a compact ball of matter poised in a preexisting void, with the galaxies compared to fragments flying away from the center of the explosion.

Easy though this image may be to grasp, it is seriously misleading and the source of much confusion: people are inevitably prompted to ask, “Where is the center of the universe?”

If the big bang really had been an exploding ball of matter, then some galaxies would lie deep in the midst of the melee, surrounded on all sides, while others would be located near the edge of the assemblage.  Suppose this were so, and picture the view from a far-flung galaxy.  In one direction would lie the center of the universe; in the opposite direction there would be empty space.  The sky would appear dramatically different depending on which way an observer looked.

That is certainly not what we see from Earth: the universe looks very much the same in all directions.  As far as our telescopes can penetrate, which is about 13 billion light-years, encompassing roughly 100 billion galaxies, matter is distributed uniformly (strictly, it is clusters of galaxies that are distributed uniformly).  There is no evidence for any bunching up around some sort of center or, conversely, for any thinning out toward an edge.

How, then, should we describe the big bang and the expanding universe, given these observational facts?  Cosmologists have struggled to find ways to describe the expanding universe in simple language.  Here’s one attempt:

The big bang happened everywhere, not at one point in space.

A simple analogy that may help is to imagine a very long string of elastic with beads attached at regular intervals.  As the elastic is stretched, the beads move apart.  Every bead extends its separation from its neighbors, so the view from any given bead will be of other beads moving away.  All beads are equal: there is no center bead.

Cosmic Jackpot by Paul Davies

First and second attempts to explain the universe: (1) religion, (2) science

January 10, 2008

Religion was the first systematic attempt to explain the universe comprehensively.  It presented the world as a product of mind or minds, of supernatural agents who could order or disorder nature at will.

Science was the second great attempt to explain the world.  This time explanations were cast in terms of impersonal forces and natural, physical processes, rather than the activities of purposive supernatural agents.

When scientific explanations conflicted with religious explanations, religion invariably lost the battle.  Mostly, theologians retreated to concentrate on social and ethical matters such as spiritual enlightenment, content to leave interpreting the physical universe to the scientists.

Cosmic Jackpot by Paul Davies

Here’s how Einstein judged a scientific theory

December 12, 2007

When judging a scientific theory, his own or another’s, he asked himself whether he would have made the universe in that way had he been God.

Albert Einstein Creator and Rebel by Banesh Hoffmann

An interventionist God, or a hands-off God?

December 4, 2007

MIT professor Alan Lightman was interviewed on NPR recently (starts at 12:15 minutes into the audio file and goes to 13:36). He said something that I found particularly interesting about two different viewpoints about God. I transcribed part of his talk:

  1. There is a kind of religious belief that is completely consistent with science, and this is if you believe in God, and God can be all powerful, as long as God does not intervene once the Universe is created, as long as God can create the laws of nature and the design of the Universe, as long as God then “sits down” so to speak, then that kind of religious belief is completely compatible with science. What science requires is a set of laws of nature or rules that govern phenomena, that are repeatable, that are predictable, that follow cause-and-effect relations.
  2. If, however, you believe in a God that, from time to time, intervenes and violates the laws of nature, for example, a God that can perform a miracle at this instant, that can make this table start floating for no reason, then that kind of belief is completely incompatible with science because then science cannot then make predictions based upon laws of nature, there is some external agency that can act at will in an unpredictable manner, and that would put scientists out of work. Some people call this the interventionist version of religious belief.

Heroic Oversimplification for Modeling our World

October 20, 2007

The invention of deliberately oversimplified theories is one of the major techniques of science, particularly of the “exact” sciences. The biophysicist employs simplified models of the cell, the cosmologist uses simplified models of the universe, and so on.

It may be useful to examine one successful scientific abstraction, to see what it is like and for the sake of the hints it may give us. We choose one which is surely an example of a heroic oversimplification.

Let us assume that we may, in order to study their motions, replace each of the major bodies of the Solar System by a point; that each point experiences a mutual attraction; that we may estimate the attractive force by multiplying the mass of one point by the mass of the other, after which we divide that product by the square of the distance between the points; and that we may neglect all else.

The fact is that this theory, the Theory of Gravitation, has been adequate for predicting the motions of the planets for two and one-half centuries – and this in the face of constant checking by positional astronomers, who, it can fairly be said, carry precision to extremes. The worst strain has come from the orbit of Mercury, which unaccountably drifted from the predicted place by one-fifth of a mil (a foot, at a distance of a mile) per century, thus showing that the theory is rough after all, just as it looks. The improved theory, by Einstein, accounts for this discordance.

The Compleat Strategyst by J.D. Williams

The whole is equal to the sum of the parts … versus … The whole is greater than the sum of the parts

September 15, 2007

The whole is equal to the sum of the parts.

The whole is greater than the sum of the parts.

These expressions represent two very different types of systems.

When someone buys a newspaper at the corner drugstore, it has no effect on my decision to buy a tube of toothpaste at the supermarket. The two events are independent. The whole is equal to the sum of the parts.

If lots of people start buying various products then it may influence others to buy products. This reinforcing behavior may create a boom in the economy. Conversely, if lots of people stop buying products then it may influence others to save, and thus create a recession. The actions by the individuals are dependent. The whole is greater than the sum of the parts.

Systems where the whole is equal to the sum of the parts are called linear systems. Each component is independent of the others.

Systems where the whole is greater than the sum of the parts are called non-linear systems. Each component may influence other components. A non-linear system is a vast web of incentives and constraints and connections. The slightest change in one part causes tremors everywhere else. “We can’t help but disturb the Universe”

— Extracted from Complexity by M. Mitchell Waldrop

Want to build the next “hot” technology? Design it so that it enables complexity.

September 1, 2007

“According to our best experimentally confirmed physical theory, all known stable matter in the universe is made up of three kinds of elementary particle coupled via four kinds of fundamental interaction.” [1]

Imagine, all of life and everything in it emerges from 3 kinds of particles interacting in 4 different ways. Astounding!

I asked a very bright colleague, “What are technologies that survive?” He responded, “Those technologies that enable complexity.” [Complexity is the ability of simple things to be composed to create complex things]

3 kinds of particles interacting in 4 different ways enable tremendous complexity. In fact, it enables the entire universe.

A much simpler example is Legos: these are simple building blocks, from which complex structures can be built.

Let’s take another example.  Suppose there is one road from my home to my workplace.  There aren’t any options in the path from home to work.  Now, suppose a bunch of side-roads are created. Now my options (and everyone else’s options) have expanded considerably. The introduction of the new roads has enabled complexity.

Want to build the next “hot” technology? Design it so that it enables complexity.

[1] Foundations of Complex-System Theories by Sunny Y. Auyang

The imagination of nature is far, far greater than the imagination of man

August 27, 2007

“The imagination of nature is far, far greater than the imagination of man … If you look closely enough at anything, you will see that there is nothing more exciting than the truth … No matter what you look at, if you look closely enough, you are involved in the entire universe.”

The Meaning Of It All by Richard Feynman

Never-ending battle between order creation and order destruction

August 25, 2007

If I leave my home alone, untouched, it soon descends into disorder: dust collects, paint peals off, wood rots, and leaks form. To prevent this degradation I need to periodically dust, vacuum, paint, replace boards, and fix leaks.

Another way to phrase this is: I must put energy and materials into my home to create order.

Still another way of stating it is: when my home is a “closed system” disorder increases. By making my home an “open system” I can import energy and matter into it to add order.

These ideas of closed/open systems and order/disorder are very important.

Here’s an excellent description of these ideas from the book The Origin of Wealth by Eric D. Beinhocker:

The universe itself is a system, and within that largest of all systems, one can define any number of smaller systems. For example, our planet is a system, as is your body, your house, or a bathtub full of water. A closed system is a system having no information flowing into or out of it. The universe itself is a closed system.

Energy might be converted into matter, and vice versa, and energy might be converted into different forms within the system, but the total amount is constant. In addition, the total disorder (entropy) in a closed system is always increasing to its maximum level, as order decays into disorder and the system eventually comes to rest.

The second type of system is an open system, with energy and matter flowing into and out of it. Such a system can use the energy and matter flowing through it to temporarily fight entropy and create order, structure, and patterns. Our planet, for example, is an open system; it sits in the middle of a river of energy streaming out from the sun. This flow of energy enables the creation of large, complex molecules, which in turn have enabled life, thus creating a biosphere that is teaming with order and complexity. Entropy has not gone away; things on the earth do break down and decay and all organisms eventually die. But the energy from the sun is constantly powering the creation of new order. In open systems, there is a never-ending battle between energy-powered order creation and entropy-driven order destruction.

Nature’s accounting rules are very strict, and there is a price to be paid when order is created in an open system. For order to be created in one part of the universe, order must be destroyed somewhere else, because the net effect must always be increasing entropy (decreasing order). Thus, as the sun powers order creation on earth, all of that life and activity creates heat, which is radiated back into space. The heat has a randomizing effect wherever it ends up, thereby increasing entropy. The earth thus imports energy and exports entropy.

Closed systems always have a predictable end state. Although they might do unpredictable things along the way, they always, eventually, head toward maximum entropy equilibrium (at rest, unchanging). Open systems are much more complicated. Sometimes they can be in a stable, equilibrium-like state, or they can exhibit very complex and unpredictable behavior patterns that are far from equilibrium. [Example, sometimes my home is in a steady, unchanging condition. Sometimes I let it go and it becomes very messy. Sometimes I get motivated and get it in spotless shape.] In an open system there may be patterns such as exponential growth, radical collapse, or oscillations. As long as an open system has free energy, it may be impossible to predict its ultimate end state or whether it will ever reach an end state.

Increasing specks of jelly in the peanut butter shows the arrow of time

August 19, 2007

Suppose you watch two time-lapse video clips. In the first video clip you see progressively more and more specks of jelly in the peanut butter. In the second clip you see less and less specks of jelly in the peanut butter.

Which video clip shows forward direction of time? Which shows time in reverse?

Answer: the first video clip shows forward direction of time.

Initially the jelly and peanut butter were separate, i.e. “ordered”. Over time, as the children make peanut butter and jelly sandwiches more and more specks of jelly get into the peanut butter and there is a greater degree of mixing of the two, i.e. it becomes more “disordered”.

There is a general trend in our world toward increasing disorder, e.g. cars rust, buildings crumble, mountains erode, apples rot, and cream poured into coffee dissipates until it is evenly mixed.

In fact, scientists have created a “law” that states that the disorder of the whole universe is increasing. Over time, all order, structure, and pattern in the universe breaks down, decays and dissipates – the ultimate end point of the universe is a random, featureless, homogenized murkiness. It is this increasing disorder that gives time its arrow, e.g. it is the increasing disorder of the peanut butter which enabled you to know which video clip shows the forward direction of time.

Scientists call this disorder “entropy”, and the law which states that the universe becomes increasingly disordered is called The Second Law of Thermodynamics.

— Extracted from The Origin of Wealth by Eric D. Beinhocker