A Biref History of Time

May 18, 2025

A Brief History of Time by Stephen Hawking is a must read and reference book for anyone interested in cosmology. It should be required reading in secondary schools to acquaint the new generations with the COSMOS and the mathematical axioms underpinning it.

Rating: 5 of 5 – Type: Science

TL;DR – The remainder of this paper is almost all excerpts from the book of concepts I wanted to reference later.

My comments are in italics. The remainder of the text is quotes from the book.

St. Augustine

St. Augustine. When asked: “What did God do before he created the universe?” Augustine didn’t reply: “He was preparing Hell for people who asked such questions.” Instead, he said that time was a property of the universe that God created, and that time did not exist before the beginning of the universe.

Theories are not Proofs

Never forget theories are not facts.

A theory is a good theory if it satisfies two requirements. It must accurately describe a large class of observations on the basis of a model that contains only a few arbitrary elements, and it must make definite predictions about the results of future observations.

Any physical theory is always provisional, in the sense that it is only a hypothesis: you can never prove it. No matter how many times the results of experiments agree with some theory, you can never be sure that the next time the result will not contradict the theory. On the other hand, you can disprove a theory by finding even a single observation that disagrees with the predictions of the theory.

Galileo

We visited Florence years ago because I had read a book about the great man. I was not disappointed with Florence.

Galileo, perhaps more than any other single person, was responsible for the birth of modern science. His renowned conflict with the Catholic Church was central to his philosophy, for Galileo was one of the first to argue that man could hope to understand how the world works, and, moreover, that we could do this by observing the real world.

Galileo’s measurements were used by Newton as the basis of his laws of motion. In Galileo’s experiments, as a body rolled down the slope it was always acted on by the same force (its weight), and the effect was to make it constantly speed up. This showed that the real effect of a force is always to change the speed of a body, rather than just to set it moving, as was previously thought. It also meant that whenever a body is not acted on by any force, it will keep on moving in a straight line at the same speed.

Newton

Issac was not a nice man but there is no argument that he stands head and shoulders above all but a handful of other scientists. He formulated the three fundamental laws of motion, the universal law of gravity, invented calculus to explain the orbits of heavenly bodies, and discovered white light split into all the colors of the rainbow just to list a few.

An explanation was provided only much later, in 1687, when Sir Isaac Newton published his Philosophiae Naturalist Principia Mathematica, probably the most important single work ever published in the physical sciences. In it Newton not only put forward a theory of how bodies move in space and time, but he also developed the complicated mathematics needed to analyze those motions. In addition, Newton postulated a law of universal gravitation according to which each body in the universe was attracted toward every other body by a force that was stronger the more massive the bodies and the closer they were to each other.

Hubble & the expanding Cosmos

Edwin Hubble was the greatest astronomer of his time and perhaps anytime.He was a polymath and athlete. He led the University of Chicago to their first Big Ten basketball title. After graduating from University of Chicago he studied jurisprudence and later added studies in literature and Spanish at Oxford. After serving in WWI he studied Astronomy at Cambridge before embarking on a career in astronomy at Mount Wilson Observatory.

But in 1929, Edwin Hubble made the landmark observation that wherever you look, distant galaxies are moving rapidly away from us. In other words, the universe is expanding.

Our modern picture of the universe dates back to only 1924, when the American astronomer Edwin Hubble demonstrated that ours was not the only galaxy. There were in fact many others, with vast tracts of empty space between them. In order to prove this, he needed to determine the distances to these other galaxies, which are so far away that, unlike nearby stars, they really do appear fixed. Hubble was forced, therefore, to use indirect methods to measure the distances. Now, the apparent brightness of a star depends on two factors: how much light it radiates (its luminosity), and how far it is from us. For nearby stars, we can measure their apparent brightness and their distance, and so we can work out their luminosity. Conversely, if we knew the luminosity of stars in other galaxies, we could work out their distance by measuring their apparent brightness.

This means that at earlier times objects would have been closer together. In fact, it seemed that there was a time, about ten or twenty thousand million years ago, when they were all at exactly the same place and when, therefore, the density of the universe was infinite. This discovery finally brought the question of the beginning of the universe into the realm of science.

Hubble noted that certain types of stars always have the same luminosity when they are near enough for us to measure; therefore, he argued, if we found such stars in another galaxy, we could assume that they had the same luminosity—and so calculate the distance to that galaxy. If we could do this for a number of stars in the same galaxy, and our calculations always gave the same distance, we could be fairly confident of our estimate.

In the years following his proof of the existence of other galaxies, Hubble spent his time cataloging their distances and observing their spectra. At that time most people expected the galaxies to be moving around quite randomly, and so expected to find as many blue-shifted spectra as red-shifted ones. It was quite a surprise, therefore, to find that most galaxies appeared red-shifted: nearly all were moving away from us! More surprising still was the finding that Hubble published in 1929: even the size of a galaxy’s red shift is not random, but is directly proportional to the galaxy’s distance from us. Or, in other words, the farther a galaxy is, the faster it is moving away! And that meant that the universe could not be static, as everyone previously had thought, but is in fact expanding; the distance between the different galaxies is growing all the time. The discovery that the universe is expanding was one of the great intellectual revolutions of the twentieth century.

General Relativity & Quantum Mechanics

General Relativity and Quantum Mechanics are the Yin and Yang of science.While Einstein is credited with General Relativity Quantum Mechanics was developed incrementally by a number of scientists including Max Planck, Albert Einstein, Niels Bohr, and Werner Heisenberg.

Today scientists describe the universe in terms of two basic partial theories—the general theory of relativity and quantum mechanics. They are the great intellectual achievements of the first half of this century. The general theory of relativity describes the force of gravity and the large-scale structure of the universe, that is, the structure on scales from only a few miles to as large as a million million million million (1 with twenty-four zeros after it) miles, the size of the observable universe. Quantum mechanics, on the other hand, deals with phenomena on extremely small scales, such as a millionth of a millionth of an inch.

When we combine quantum mechanics with general relativity, there seems to be a new possibility that did not arise before: that space and time together might form a finite, four-dimensional space without singularities or boundaries, like the surface of the earth but with more dimensions. It seems that this idea could explain many of the observed features of the universe, such as its large-scale uniformity and also the smaller-scale departures from homogeneity, like galaxies, stars, and even human beings. It could even account for the arrow of time that we observe. But if the universe is completely self-contained, with no singularities or boundaries, and completely described by a unified theory, that has profound implications for the role of God as Creator.

Einstein and Relativity

There is not much I can say about Albert Einstein. He is the best known scientist of all time. His theories of special and general relativity still hold true even more than 100 years later. For example, we recently measured gravitational waves that he predicted before WWI.

Einstein – Equations are more important to me, because politics is for the present, but an equation is something for eternity.

Albert Einstein’s theory of relativity, developed in two main parts – special relativity (1905) and general relativity (1915) – revolutionized our understanding of space, time, gravity, and the universe.

Special Relativity:

  • The laws of physics are the same for all observers in uniform motion.
  • The speed of light in a vacuum is the same for all observers, regardless of the motion of the light source.

General Relativity:

  • Gravitational time dilation: Time passes slower in stronger gravitational fields.
  • Bending of light: Light rays bend as they pass through a gravitational field.
  • Gravitational lensing: The gravity of massive objects can bend and magnify light from objects behind them.
  • Precession of orbits: The orbits of planets are not perfectly elliptical but precess (slowly rotate) over time, a phenomenon accurately explained by general relativity (e.g., the orbit of Mercury).
  • Existence of black holes: Regions of spacetime where gravity is so strong that nothing, not even light, can escape.
  • Gravitational waves: Ripples in spacetime that propagate at the speed of light, produced by accelerating massive objects.
  • Provides the foundation for our understanding of cosmology and the evolution of the universe.

Light

The fact that light travels at a finite, but very high, speed was first discovered in 1676 by the Danish astronomer Ole Christensen Roemer.

A proper theory of the propagation of light didn’t come until 1865, when the British physicist James Clerk Maxwell succeeded in unifying the partial theories that up to then had been used to describe the forces of electricity and magnetism. Maxwell’s equations predicted that there could be wavelike disturbances in the combined electromagnetic field, and that these would travel at a fixed speed, like ripples on a pond. If the wavelength of these waves (the distance between one wave crest and the next) is a meter or more, they are what we now call radio waves. Shorter wavelengths are known as microwaves (a few centimeters) or infrared (more than a ten-thousandth of a centimeter). Visible light has a wavelength of between only forty and eighty millionths of a centimeter. Even shorter wavelengths are known as ultraviolet, X rays, and gamma rays.

the Big Bang

We lost much when we lost Bell Laboratories including C and Unix. Another example pointed out in this book, Two scientists at Bell Labs discovered cosmic microwave background radiation which was considered important evidence for the Big Bang theory. An interesting bit of information:Initially they thought it was caused by bird droppings on the antenna

In 1965 two American physicists at the Bell Telephone Laboratories in New Jersey, Arno Penzias and Robert Wilson, were testing a very sensitive microwave detector. (Microwaves are just like light waves, but with a wavelength of around a centimeter.) Penzias and Wilson were worried when they found that their detector was picking up more noise than it ought to.

At roughly the same time as Penzias and Wilson were investigating noise in their detector, two American physicists at nearby Princeton University, Bob Dicke and Jim Peebles, were also taking an interest in microwaves.

They were working on a suggestion, made by George Gamow (once a student of Alexander Friedmann), that the early universe should have been very hot and dense, glowing white hot.

Dicke and Peebles argued that we should still be able to see the glow of the early universe, because light from very distant parts of it would only just be reaching us now. However, the expansion of the universe meant that this light should be so greatly red-shifted that it would appear to us now as microwave radiation. Dicke and Peebles were preparing to look for this radiation when Penzias and Wilson heard about their work and realized that they had already found it. For this, Penzias and Wilson were awarded the Nobel Prize in 1978 (which seems a bit hard on Dicke and Peebles, not to mention Gamow!).

According to the general theory of relativity, there must have been a state of infinite density in the past, the big bang, which would have been an effective beginning of time. Similarly, if the whole universe recollapsed, there must be another state of infinite density in the future, the big crunch, which would be an end of time. Even if the whole universe did not recollapse, there would be singularities in any localized regions that collapsed to form black holes. These singularities would be an end of time for anyone who fell into the black hole. At the big bang and other singularities, all the laws would have broken down, so God would still have had complete freedom to choose what happened and how the universe began.

Dark Matter

Scientists believe Dark Matter makes up about 85% of the Universe due to the behavior of galaxies they cannot explain otherwise.

Our galaxy and other galaxies, however, must contain a large amount of “dark matter” that we cannot see directly, but which we know must be there because of the influence of its gravitational attraction on the orbits of stars in the galaxies. Moreover, most galaxies are found in clusters, and we can similarly infer the presence of yet more dark matter in between the galaxies in these clusters by its effect on the motion of the galaxies. When we add up all this dark matter, we still get only about one tenth of the amount required to halt the expansion. However, we cannot exclude the possibility that there might be some other form of matter, distributed almost uniformly throughout the universe, that we have not yet detected and that might still raise the average density of the universe up to the critical value needed to halt the expansion.

Heisenberg Uncertainty Principle

What does all this mean? I am uncertain.

The quantum hypothesis explained the observed rate of emission of radiation from hot bodies very well, but its implications for determinism were not realized until 1926, when another German scientist, Werner Heisenberg, formulated his famous uncertainty principle. In order to predict the future position and velocity of a particle, one has to be able to measure its present position and velocity accurately. The obvious way to do this is to shine light on the particle. Some of the waves of light will be scattered by the particle and this will indicate its position. However, one will not be able to determine the position of the particle more accurately than the distance between the wave crests of light, so one needs to use light of a short wavelength in order to measure the position of the particle precisely. Now, by Planck’s quantum hypothesis, one cannot use an arbitrarily small amount of light; one has to use at least one quantum. This quantum will disturb the particle and change its velocity in a way that cannot be predicted. Moreover, the more accurately one measures the position, the shorter the wavelength of the light that one needs and hence the higher the energy of a single quantum. So the velocity of the particle will be disturbed by a larger amount. In other words, the more accurately you try to measure the position of the particle, the less accurately you can measure its speed, and vice versa. Heisenberg showed that the uncertainty in the position of the particle times the uncertainty in its velocity times the mass of the particle can never be smaller than a certain quantity, which is known as Planck’s constant. Moreover, this limit does not depend on the way in which one tries to measure the position or velocity of the particle, or on the type of particle: Heisenberg’s uncertainty principle is a fundamental, inescapable property of the world.

Black Holes

The theory behind black holes has been around for quite a long time. But it hasn’t been until recently – 1960S – when the work blossomed. The concept is of particular interest to me because the term black hole was not coined until after I graduated from high school.

The term black hole is of very recent origin. It was coined in 1969 by the American scientist John Wheeler

To understand how a black hole might be formed, we first need an understanding of the life cycle of a star. A star is formed when a large amount of gas (mostly hydrogen) starts to collapse in on itself due to its gravitational attraction. As it contracts, the atoms of the gas collide with each other more and more frequently and at greater and greater speeds—the gas heats up. Eventually, the gas will be so hot that when the hydrogen atoms collide they no longer bounce off each other, but instead coalesce to form helium. The heat released in this reaction, which is like a controlled hydrogen bomb explosion, is what makes the star shine. This additional heat also increases the pressure of the gas until it is sufficient to balance the gravitational attraction, and the gas stops contracting. It is a bit like a balloon—there is a balance between the pressure of the air inside, which is trying to make the balloon expand, and the tension in the rubber, which is trying to make the balloon smaller. Stars will remain stable like this for a long time, with heat from the nuclear reactions balancing the gravitational attraction. Eventually, however, the star will run out of its hydrogen and other nuclear fuels. Paradoxically, the more fuel a star starts off with, the sooner it runs out. This is because the more massive the star is, the hotter it needs to be to balance its gravitational attraction. And the hotter it is, the faster it will use up its fuel. Our sun has probably got enough fuel for another five thousand million years or so, but more massive stars can use up their fuel in as little as one hundred million years, much less than the age of the universe. When a star runs out of fuel, it starts to cool off and so to contract. What might happen to it then was first understood only at the end of the 1920s.

Chandrasekhar worked out how big a star could be and still support itself against its own gravity after it had used up all its fuel. The idea was this: when the star becomes small, the matter particles get very near each other, and so according to the Pauli exclusion principle, they must have very different velocities. This makes them move away from each other and so tends to make the star expand. A star can therefore maintain itself at a constant radius by a balance between the attraction of gravity and the repulsion that arises from the exclusion principle, just as earlier in its life gravity was balanced by the heat.

Chandrasekhar realized, however, that there is a limit to the repulsion that the exclusion principle can provide. The theory of relativity limits the maximum difference in the velocities of the matter particles in the star to the speed of light. This means that when the star got sufficiently dense, the repulsion caused by the exclusion principle would be less than the attraction of gravity. Chandrasekhar calculated that a cold star of more than about one and a half times the mass of the sun would not be able to support itself against its own gravity. (This mass is now known as the Chandrasekhar limit.)

This had serious implications for the ultimate fate of massive stars. If a star’s mass is less than the Chandrasekhar limit, it can eventually stop contracting and settle down to a possible final state as a “white dwarf” with a radius of a few thousand miles and a density of hundreds of tons per cubic inch.

Landau pointed out that there was another possible final state for a star, also with a limiting mass of about one or two times the mass of the sun but much smaller even than a white dwarf. These stars would be supported by the exclusion principle repulsion between neutrons and protons, rather than between electrons. They were therefore called neutron stars. They would have a radius of only ten miles or so and a density of hundreds of millions of tons per cubic inch.

Chandrasekhar had shown that the exclusion principle could not halt the collapse of a star more massive than the Chandrasekhar limit, but the problem of understanding what would happen to such a star, according to general relativity, was first solved by a young American, Robert Oppenheimer, in 1939. His result, however, suggested that there would be no observational consequences that could be detected by the telescopes of the day.

The picture that we now have from Oppenheimer’s work is as follows. The gravitational field of the star changes the paths of light rays in space-time from what they would have been had the star not been present. The light cones, which indicate the paths followed in space and time by flashes of light emitted from their tips, are bent slightly inward near the surface of the star. This can be seen in the bending of light from distant stars observed during an eclipse of the sun. As the star contracts, the gravitational field at its surface gets stronger and the light cones get bent inward more. This makes it more difficult for light from the star to escape, and the light appears dimmer and redder to an observer at a distance. Eventually, when the star has shrunk to a certain critical radius, the gravitational field at the surface becomes so strong that the light cones are bent inward so much that light can no longer escape (Fig. 6.1). According to the theory of relativity, nothing can travel faster than light. Thus if light cannot escape, neither can anything else; everything is dragged back by the gravitational field. So one has a set of events, a region of space-time, from which it is not possible to escape to reach a distant observer. This region is what we now call a black hole. Its boundary is called the event horizon and it coincides with the paths of light rays that just fail to escape from the black hole.

The work that Roger Penrose and I did between 1965 and 1970 showed that, according to general relativity, there must be a singularity of infinite density and space-time curvature within a black hole. This is rather like the big bang at the beginning of time, only it would be an end of time for the collapsing body and the astronaut. At this singularity the laws of science and our ability to predict the future would break down.

The event horizon, the boundary of the region of space-time from which it is not possible to escape, acts rather like a one-way membrane around the black hole: objects, such as unwary astronauts, can fall through the event horizon into the black hole, but nothing can ever get out of the black hole through the event horizon. (Remember that the event horizon is the path in space-time of light that is trying to escape from the black hole, and nothing can travel faster than light.)

Black holes are one of only a fairly small number of cases in the history of science in which a theory was developed in great detail as a mathematical model before there was any evidence from observations that it was correct. Indeed, this used to be the main argument of opponents of black holes: how could one believe in objects for which the only evidence was calculations based on the dubious theory of general relativity?

How could we hope to detect a black hole, as by its very definition it does not emit any light? It might seem a bit like looking for a black cat in a coal cellar. Fortunately, there is a way. As John Michell pointed out in his pioneering paper in 1783, a black hole still exerts a gravitational force on nearby objects.

Gravitational Waves

Over 100 years after he proposed the General Theory of Relativity Einstein is proven right again.

General relativity predicts that heavy objects that are moving will cause the emission of gravitational waves, ripples in the curvature of space that travel at the speed of light.

Like light, gravitational waves carry energy away from the objects that emit them. One would therefore expect a system of massive objects to settle down eventually to a stationary state, because the energy in any movement would be carried away by the emission of gravitational waves.

Time Travel

Suppose, however, that the spaceship would have to travel faster than light to carry the news of the race to the Congress. Then observers moving at different speeds can disagree about whether event A occurred before B or vice versa. According to the time of an observer who is at rest with respect to the earth, it may be that the Congress opened after the race. Thus this observer would think that a spaceship could get from A to B in time if only it could ignore the speed-of-light speed limit. However, to an observer at Alpha Centauri moving away from the earth at nearly the speed of light, it would appear that event B, the opening of the Congress, would occur before event A, the 100-meter race. The theory of relativity says that the laws of physics appear the same to observers moving at different speeds.

Marv comment:This makes my head hurt., I don’t understand it at all. Will have to think about it. Since we can’t go faster than the speed of light it is a moot point but if we could I don’t understand it. As you approach the speed of light time slows down. So if you go faster than the SOL time reverses?

That might seem to rule out both rapid space travel and travel back in time. However, there is a possible way out. It might be that one could warp space-time so that there was a shortcut between A and B. One way of doing this would be to create a wormhole between A and B. As its name suggests, a wormhole is a thin tube of space-time which can connect two nearly flat regions far apart.

That might seem to rule out both rapid space travel and travel back in time. However, there is a possible way out. It might be that one could warp space-time so that there was a shortcut between A and B. One way of doing this would be to create a wormhole between A and B. As its name suggests, a wormhole is a thin tube of space-time which can connect two nearly flat regions far apart

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Einstein in Kafkalland

January 20, 2025

Rating: 4 out of 5

Einstein in Kafkaland is a Graphic Comic by Ken Krimstein. It’s one of the 12 non-fiction books I’ve committed to read this year in pursuit of the motto:

Live like today is the last day of your life; Learn like you will live forever.

This is not the first graphic novel I’ve read, but it is the first non-fiction one. The other two I’ve read are The Sandman by Neil Gaiman. It’s like a 10 volume collection and is excellent. The other is The Watchmen by Alan Moore which is most excellent as Bill and Ted would say.

The Story

The main plot of the story: Albert is trying to figure out how to merge Gravity into his Theory of Relativity.

Albert and family traveled to Prague for his new position at German University in Prague on April 1, 2011. They departed back to Zurich July 25, 2012.

While in Prague he meets Franz Kafka.

The book’s author believes Albert formulated his General Theory of Relativity in Prague. His 1911 paper was correct in theory but the equations were not correct. It took him until 1915 to perfect the Theory which was published in 1916.

In Albert’s own words:

In the quiet rooms of the Theoretical Physical Institute of the Prague German University in the Vinicna ulice I discovered in 1911 that the equivalence principle demands a refraction of the rays of light at the sun of a sum that can be observed without knowing that more than a hundred years before a similar conclusion out of the Newton mechanic in connection with Newton’s emission theory of the light was drawn. Also the still not really confirmed consequence of the red shift of the spectral lines I discovered in Prague.

From the preface he wrote in the Czech edition of his book The Foundation of the General Theory of Relativity

The book contained a few interesting characters. I’ll end this review with the list:

Characters

Albert

Our hero along with Franz.

He thinks up stuff about how the Cosmos works

Franz Kafka

An insurance agent that will soon become a great writer.

He is working on his breakout book during this period he wrote The Judgment which is considered his breakout work. He also worked on The Metamorphosis which may be his most well know work during this period

Max Abraham

Out to prove Albert’s theory of relativity is hogwash. Of course he could not.

Mileva

Albert’s wife

Bertha Fanta

Throws a “Salon” where Albert and Franz meet.

They had “Salons” back then where people got together and talked and sometimes played music and maybe sang and did other stuff.

Issac Newton

Comes from the grave to discuss his discovery of gravity with Issac and Franz.

Skeleton

Our story’s narrator – He has graced the astronomical clock in Prague since 1410.

Paul Ehrenfest

Another Austrian physicist visits Albert and gives him some ideas concerning gravity and space-time.

Euclid

Another visitor from the grave, Euclid visits Albert to warn him of shattering the current laws of Physics.

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One hot Summer

September 8, 2023

Today, September 8, the high temperature in DFW was 109. Overall, this is our third hottest Summer in North Texas since we’ve been recording temperatures in 1898 according to the National Weather Service. I find it interesting the local and national TV newscasts state this is the second hottest Summer on record

I’ve lived in the DFW area through all of the 5 hottest Summer:

Year/Avg Temp

  1. 2011/90.5
  2. 1980/89.2
  3. 2023/88.7
  4. 1998/88.3
  5. 2022/88.2

Lack of rain also accompanies hot weather here and this Summer was no exception. If you don’t count the .2 inches of rain DFW received, which we did not we’ve gone over 60 days without rain. (The record is 84 days).

The photo below was taken on one of the walking trails in our neighborhood. A typical August/September day in North Texas and everything is brown except for trees.

Walking Trail

 

Although the temperature was 109 today the humidity was 19%. I felt more comfortable outside in the shade today than at Cardinal games in 90 degree, 90% humidity weather.

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The day the Dinosaurs Died

August 11, 2016

Just finished a fascinating chapter in The Sixth Extinction titled The Luck of the Ammonites, or un-luck as fate would have it. We’ve all heard that the dinosaurs were exterminated by a massive asteroid hitting the Earth and causing Nuclear Winter. However that’s pretty much all I knew. This chapter narrates the rest of the story. Very Interesting!

Back in 1969, Walter Alvarez was fascinated by a thin layer of sediment (dubbed the K-T Layer because it separates the Cretaceous and Paleogene periods) just outside of Gubbio Italy. He was intrigued because of the huge differences in fossils between the layers immediately above and below this area. Later, back in California, he sparked an interest of this anomaly in his father, Luis – a professor at Berkley.

In one of their experiments, they tested the clay samples for iridium, a rare,on Earth, element but abundant on asteroids. The iridium levels were off the charts. They did not know what to make of this anomaly. However, they were able to obtain and test clay samples of the same layers from other parts of the World all with the same results. All had the same extremely high iridium levels.

They tried out numerous theories before settling on the Impact Hypothesis in 1980:

65 million years ago an asteroid 6 miles in diameter crashed into the Earth with an impact of more than a 100 million hydrogen bombs. Debris including iridium from the asteroid spread around the globe causing Nuclear Winter (A Carl Sagan addition) thus resulting in the extinction of 75% of the life on Earth.

The Alvarez’s were labeled charlatans after publishing their theory by the entire scientific community. The prevailing theory was Darwin’s Natural Selection wherein species evolved or became extinct gradually over millions of years.

Thus began the search to find the “smoking gun” – the asteroid crater. The general criteria were 65 million years old and maybe a couple of hundred miles in diameter. No know crater fit the criteria. Finally, on the banks of Texas’ Brazos River scientist came across patterns consistent with a “nearby impact” thereby narrowing the search to the Gulf of Mexico area. Finally, the missing piece, a 100 mile wide crater was located just off the Yucatan Peninsula with the help of drilling samples taken years earlier by PEMEX.

Not only the dinosaurs but over 75% of life on Earth at that time was eliminated. Not only on the surface, but in the air, and in the sea also. Not only animals but plants were not spared execution either. The striking difference in the fossils above and below the K-T layer provide the Great Extinction’s evidence.

If your interested, I recommend The Sixth Extension book. There are also some good resources on the web including:

Almost forgot, Ammonites were a sea creature that became extinct during the K-T Event. Their fossils were numerous in the Gubbio layer.

Notes:

  1. For movie fans the Cretaceous Period follows the Jurassic Period.
  2. How do you get K-T from Cretaceous–Paleogene? Cretaceous is usually abbreviated K for its German translation Kreide (chalk) derived from the Latin “creta” (chalk). The Paleogene Period was created bu splitting the Tertiary Period into two periods: Paleogene and Neogene.

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The Theory of Everything

December 18, 2013

I noticed this book in the science section of a used book store while searching for an inexpensive copy of an astronomy book I wanted.  Of course the title caught my eye – The Theory of Everything.  Wow, it would be really cool to know the theory of absolutely everything!  Sounded too good to be true! Since I was in a used book store the book was cheap.  It was also short and the author was Stephen Hawking the famous physicist.

One thought struck me as odd. I had never heard of the book before even though I minored in physics in college and follow the topic as I have time. I checked Stephen’s web site. The web site does not mention the book although it does list all his books, lectures, and publications.  Finally, I googled “The Theory of Everything” and discovered  the book is an unauthorized publication of some of his earlier lectures.  Stephen, in fact, filed a complaint with the FTC to stop it’s publication which obviously was not successful. However since I had already purchased the book I decided to go ahead and read it

The first chapter covers the evolution of man’s concept of the Universe starting with the Earth being the center of the Universe. Then the chapter progresses through time ending with Hubble’s discovery that the Cosmos is expanding more and more rapidly.

The second chapter continues with the ever expanding universe evolution.  Many scientists believed the universe to be static and worked diligently to disprove Hubble’s ever expanding universe.  In the end however the ever expanding Universe became universally accepted based partial on the work of:

  • Alexander Friedmann who based upon General Relativity showed the Universe should not be static
  • Penzias and Wilson working at Bell Labs discovered the microwave radiation that started as bright light at the moment of the Big Bang
  • Roger Penrose who proposed the concept of the Black Hole.

Chapter 3 delves into Black Holes in depth. It covers the evolution of the Black Hole concept which was first proposed in 1783 although the term Black Hole was not coined until 1969.  A Black Hole is simply a star sufficiently massive and compact that no light can escape from.  White dwarfs and neutron stars are two closely related concepts.  In all three cases this final state of a star is reached when it has burnt up all it’s fuel (hydrogen). The final state is determined by the mass of the star.  Smaller stars become neutron stars; medium stars become white dwarfs; and larger stars become Black Holes.

Chapter 4 reveals that Black Holes ain’t so Black.  Basically, paired particles (one with positive energy and one with negative energy) near the Black Hole’s Event Horizon break apart. The negative energy particle falls into the black hole while the positive energy particle repels away from the Black Hole’s Event Horizon into the Cosmos. To the outside observer the Black Hole appears to be emitting particles.  An interesting effect on the Black Hole itself is the Black Hole loses energy and mass based on E=MC2.  After a long, long period of time the Black Hole would simply disappear.

Chapter 5 outlines several theories on origin and fate of the Universe. The theories discussed are:

  • The Hot Big Bang Model: Assumes the temperature was infinite at the Big Bang and the Universe will cool off though the eons of time until it reaches absolute zero.  However this model raises some troubling questions such as why was the temperature so hot, why is the Universe so Uniform, etc?
  • The Inflationary Model: This model assumes a very rapid exponential expansion at the beginning. At some point in time the inflationary expansion ended much as water transitions from liquid to solid when it freezes.  This model solves some of the more troubling questions of The Hot Big Bang Model.
  • The No Boundary Condition: In this model there is no beginning or end of the Universe.  There are no Singularities where the laws of physics break down.  The Universe has always existed.  This model is analogous to the surface of the Earth.  If we start at the North Pole the Universe is a single point. As we travel to the Equator the Universe expands then contracts as we close in on the South Pole. Then we start all over again in a never ending cycle. The Universe is neither created or destroyed. The Universe just “is.”

The Direction of Time is the subject of Chapter 6. According to Professor Hawking there are three Arrows of Time:

  • Thermodynamic arrow of time: The direction of time in which disorder or entropy increase
  • Psychological arrow of time: The direction in which we feel time pass
  • Cosmological arrow of time: The direction of time in which the Universe is expanding rather than contracting

The core of this chapter is the direction of the first two times is towards what we perceive as the future.  What a surprise!

The Cosmological arrow of time is also towards the future because the Universe is still expanding.  The question to ponder is will time reverse when the Universe stops expanding and begins to collapse?  The professor believes not. However we have 10s of millions of years before that event so whichever case is true we don’t care.

Finally, the last chapter, we are getting around to the title of the book The Theory of Everything (ToE) refers to a yet to be discovered unified theory that explains the Universe. Currently General Relativity and Quantum Mechanics are two mutually incompatible theories that explain the Universe. That is, they cannot both be correct. Depending on the circumstances either one or the other is used. General Relativity considers only the force of Gravity in explaining for understanding the Universe. Quantum Mechanics uses the three non-gravitational forces (weak, strong, and electromagnetic) in understanding the Universe. Scientist hope to discover the ToE to solve this conundrum. I don’t really understand the weak and strong forces. Perhaps Professor Hawking will write a book “The Theory of the Weak and the Strong?”

At the time of the lectures String Theory and Multi-dimensions  were the most likely candidate.  Close to 20 years have passed since Professor Hawking’s lectures. Still, the ToE has not been discovered and remains the main goal of most physicists.

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