Download Chapter 1-Thinking about the universe

A Briefer History of Time
Will Meldon
Yuska, Biology
3
By Steven Hawking
Chapter 1-Thinking about the universe
At the beginning of the chapter, the book tells a brief story about a scientist who lectured a
group of people about what the universe truly is a vast collection of starts that orbit around the
sun. At the end of his lecture, an old woman stood up and said that what he said was rubbish
and that the world was really a flat disk supported on the back of turtle on top of an infinite
tower of turtles. Although most people would pass this off as ridiculous, they really don’t
know a whole lot more than the woman who thinks were all supported on the backs of an
infinite stack of turtles. Someday we may know much more than we do now and things with
make sense and be reasonable, or they will be as absurd as the turtle theory.
Chapter 2-Our evolving picture of the universe
Although as late as the time of Christopher Columbus, the theory that the earth was flat was
widely accepted as fact but theories that the world was in fact round have existed since 430
B.C. in the times of Aristotle. His arguments were that if the world was completely flat, then
it would not eclipse the moon so completely and that you saw the masts and sails of a ship on
the horizon before you saw the rest of the ship. He also noted that all the stars moved as one
but the planets moved independently leading Ptolemy to create his model of the universe. His
model of the universe consisted of 8 rotating spheres that contained all heavenly bodies with
the earth in the center of it all. Later, Copernicus’ theory that the earth revolved around the
sun was conceived in part due to the discovery that other planets had moons of their own.
Along with Galileo Kepler’s discovery discovery that the planetary orbits were elliptical rather
than perfect circles helped to disprove Ptolemy’s theory. But until Newton, the elliptical orbits
theory could not be explained.
Chapter 3-The Nature of Scientific Theory
Chapter threes primary focus is on the pursuit for the ultimate theory that will explain all
aspects of the universe. But problems arise in that we always break our theories into smaller
parts which give inaccurate results due to the fact that all things in the universe are dependent
on each other. One major problem is unifying the theories of General Relativity and quantum
mechanics. The problem is that the two theories are inconsistent with each other meaning at
least one if not both are wrong in some way or another. Another possibility is that the ultimate
theory governs everything and even says what will or will not happen, the problem there is that
if this is true, the theory itself has already decided whether we find it or not. The only theory
that can really help us is Darwin’s theory of natural selection. Although science has helped us
survive in the past, there is a possibility that it will be our destruction in the future.
Chapter 4-Newtons Universe
The chapter starts with a brief overview of Aristotle’s believe that heavy things fall faster than
light things which was disproved by Galileo and then explained by Newton. Newton’s
theories said that all bodies are attracted to each other and although larger bodies have more
gravitational attraction, they require more force to move which cancels out mass difference
and explains why heavy items fall just as fast as light ones. Another major difference in the
beliefs of Aristotle and Newton are that Aristotle believed the earth was at rest while Newton
realized that everything is moving from someone’s perspective. One thing that they did agree
on was that time was absolute which has been disproved by 20th century physicists.
Chapter 5-Relativity
The concept that travels light travels at a finite speed was first introduced by de Roemer in
1676 when he noticed that Jupiter’s eclipse happened at irregular intervals that happen more
often when Jupiter is close and less often when Jupiter is far away. This was confirmed by
Maxwell with his discovery of the electromagnetic spectrum and electromagnetic fields
however this did not correspond with the lack of a definite form of rest. To reconcile the
theories, the idea of ether was formulated. Ether was a substance found everywhere including
the vacuums of empty space and no matter what perspective you had; you would measure the
speed of light in relation to the ether. Michelson and Morley decided to test this theory. They
realized that the earth was hurtling though ether very fast so their lab must be too. They
decided to measure the speed of light when going at right angles to ether and when going with
the ether and to their surprise, the speeds were exactly the same. With ether disproven,
Einstein came up with the theory of relativity which forces us to abandon the idea that time
and space are definite and separate. To prove that you could not go faster than light, E=MC²
which says that as you increase speed, you increase mass and at the speed of light you would
have a infinite mass which would require an infinite amount of energy to move. The problem
with Einstein’s theory is that according to Newton’s laws, gravity moves at an infinite speed,
which conflicts with the general theory of relativity.
Chapter 6-Curved Space
Einstein’s general theory of relativity suggests that space-time follows a curved path because
of gravity. Things like the earth don’t follow curved paths because gravity makes them but
because of the geodesic which is the nearest thing to a straight path in curved space-time.
Because of this, light can be bent by large masses with larger gravitational pulls. Another part
of the general theory of relativity suggests that time runs more slowly near a massive body like
the earth. This also means that uniform acceleration and uniform gravitational fields cannot be
differentiated and thus, time is unique to everyone and everything as does the universe which
gives it a finite life.
Chapter 7-The Expanding Universe
Because of the vast distance of space, methods like parallaxes and luminosity cannot be used
to classify and measure star distances. Instead, scientists were forced to put the light emitted
by the stars through prisms dispersing it. By looking at what areas of the spectrum are weaker,
they can determine various things about a star. What scientists noticed was that al the stars
spectrums were on the red side of the spectrum, meaning that they were slowly moving away
from us according to the functioning of the doplar effect. Before then, all other physicists
though the universe was static but Friedmann said that it couldn’t be static. With further
discoveries like dark matter, scientists have begun to figure out how the universe behaves.
Friedmann put forth three behaviors that the universe could follow. One involved the universe
expanding slowly then collapsing on itself. The second involves the universe rapidly
expanding forever. And the third has the universe expanding and then eventually slowing
down but never quite stopping. Currently, none of these match observations.
Chapter 8-The Big Bang, Black Wholes, And the Evolving Universe
At the beginning of the universe, the distance between everything was zero and the
temperature was infinite. After the big bang and rapid expansion of the universe, particles
began to lose energy and stick together and eventually succumb to things like strong force and
electromagnetic force. The particles not destroyed by their antiparticles counterparts formed
mostly hydrogen and some other heavy metals. For the next million years, the universe would
have continued to expand uneventfully but eventually, gravitational attraction would have
caused some sections of the universe to collapse. Collapsed galleys would begin to rotate
slowly and then as they began to flatten out, they would start spinning faster and faster till the
section restabilized. This spinning would create spiral galaxies. As time goes on, the helium
and hydrogen clouds in the galaxy would break apart and collapse forming stars which burn
hydrogen into helium. After it runs out of fuel, the star would collapse and become hotter and
more dense and its gravitational force would be too great for even light to get past, forming a
black whole on the surface of which, time has stopped. When this happens to massive stars, it
gives of massive amounts of radiation in super novas. This is why life would not evolve in
areas where super novas were common.
Chapter 9-Quantum Gravity
Marquis de Laplace formulated that the universe was completely deterministic. What was
later proven was that determining the exact position of particles and at the same time
measuring speed accurately was impossible which led to the belief that nothing is certain.
Another aspect of quantum theory is that particles and waves can reinforce and cancel each
other out. What this led to was the discovery that orbiting electrons behave similar to waves
and takes every possible path they can when going to a destination. This also means that
nothing is certain. Although the chance of something happening may be so unlikely you
couldn’t get it to happen by chance in the entire life of the universe, there is still a possibility it
could happen. All this helps lead to the quantum theory of gravity and the probability that the
universe is endless and boundaries.
Chapter 10-Wormholes and Time Travel
To travel in time, one must go nearly the speed of light. When returning from your trip, time
will have gone faster on earth than it did for you. This means that traveling forward in time is
not only possible; it’s just a matter of engineering before we can do it. But as for going back
in time, it’s slightly more complicated. The first possibilities that people could travel back in
time were formulated by Gödel. His mathematic solution to Einstein’s equation allowed time
travel but his universe rotated and didn’t not expand, ours does. To go back in time, one must
go faster than the speed of light, which is supposed to be impossible. But it still is
theoretically possible through the use of a wormhole. A wormhole is a straight tunnel in
curved space that would shorten distances enormously. One particularly damning piece of
evidence that goes against traveling back in time is the fact that no one has ever come from the
future and told us about it and other paradoxes that no one has come back and messed
everything up for us yet.
Chapter 11-Forces of Nature and the Unification of Physics
The quest to find the complete theory for everything in the universe is known as the
Unification of Physics. Although we have made great strides in science in recent years, the
unified theory is still a very difficult thing to achieve. We now know more about particles
than we did before and we also know more about their forces. The four forces are
Gravitational, electromagnetic, weak force and strong force. With the knowledge of these
forces, attempts have been made to unify strong, weak and electromagnetic forces in the Grand
Unified theory which isn’t all that grand nor is it unified. Yet it is still progress towards the
unified theory. The problem when adding gravity is that because of the uncertainty principles,
empty space has particles but cant be included into the formula because their energy cannot be
calculated. Even by canceling out infinities and other factors, the answers still have a very
high chance of coming out wrong and giving you bad info, which is where string theory comes
into play. These so called strings are particles with only the dimension of length and have
lengths running along them. String theory required the existence of ten or 26 dimensions
which were discovered to probably be very very small dimensions that were really curvy.
With the creation of the anthropothic principle, it explains that we are 3 dimensional because
living creatures would not be able to live as well if we were 2 dimensional and on an atomic
scale, electrons would spiral away from their orbits and leave their atoms. All of this leads to
the realization that there could be a unified theory or it could just be infinite overlapping ones.
Chapter 12-Conclusion
As time progresses, we learn more and more about our universe. We learned that certain
regularities exist making it so that spirits aren’t the ones controlling things. We learn more
and more about what we can’t see. Why the universe exists, how it began and what it will do
are always going to be asked but until later, we won’t know what the answers are. Some
answers could be found through divine beings or we could still be on the right track. Even so,
the ultimate quest still is and always will be to find the ultimate unified theory.
The sciences used in this book are Relativity, which deals with things on an enormous scale,
and Quantum physics, which deals with things on an atomic scale.
The book “A Briefer History of Time” by Steven hawking primarily focuses on the
complex nature of the universe we live in. From things on the size of atoms and smaller to
things larger than could be comprehended by a human being, the science of how it works is all
described in the book.
One of the most focused on scientific aspects of this book is Newtonian physics. Although
his other theories are very important in the real world, the one most used that nothing is at rest.
Everything is moving from someone’s perspective. This is very important to the book because
one of the most discussed topics is light speed and if nothing is at rest, than speed is
undeterminable.
Another very important science used in the book is the theory of relativity. Relativity was
conceived by Einstein and it helps prove that you cannot go faster than light. This affects time
travel because the only way to go back in time is to go faster than light, which is impossible.
Einstein and his theories play a major roll in quantum physics and without them; this book
would have had huge amounts of loose ends.
Some of the other Subjects discussed in the book are string theory, wormholes, black holes
and that our universe is expanding. Mathematical equations are used to solve all these theories
and the digits used are often incredibly largest or incredibly small.
The primary of the books focus however, is on the acquisition of the ultimate unified theory
that explains and predicts everything. So far we have unveiled vast amounts of information
and partial theories of how the universe works but were have yet to find the unified theory. A
Although some points in the book make it impossible to ever find it, the ultimate goal of
science and this book is to someday uncover it.