The Theory Of Everything By Stephen Hawking Book Summary

Stephen Hawking delivered a series of lectures titled “The Theory of Everything.” These lectures aim to provide an overview of what is thought to be the universe’s history. He provides a history of how science has understood the universe as a result. He also provides a thorough explanation of what happened right after the Big Bang. Hawking also discusses the subject in cosmology for which he is best known: the study of black holes.

the theory of everything book summary — The Theory of Everything

Table of Contents

The First Four Principles of the Universe

Aristotle
As early as 340 BC, Aristotle contemplated the possibility of a spherical Earth. He discussed two theories that suggested Earth was spherical in his work On the Heavens. First of all, he had noted that moon eclipses were brought on by Earth’s position between the Sun and the Moon. This implied that the Earth was round since its shadow on the Moon was constantly circular. The Pole Star lies lower in the sky when seen in the South, as Aristotle discovered throughout his travels. Once more, this suggests that the Earth is spherical rather than disc-shaped. Aristotle’s theories were incorrect even though his conclusions were accurate.

For instance, he thought the Earth was fixed and that the Sun, Moon, planets, and stars all revolved in a circle around it.

Ptolemy
On top of these concepts, Ptolemy expanded throughout the first century AD. He developed an entire cosmological theory with Earth at its core. The Earth was surrounded by eight spheres that included the Moon, Sun, stars, and five planets. Mercury, Venus, Mars, Jupiter, and Saturn were the only five planets that were recognized. Once more, Ptolemy’s theory contained obvious errors. He did, however, expand on Aristotle’s theories and offer a system that can forecast the locations of structures that are visible at night rather accurately. This thesis was widely embraced by the Christian Church, in part because it posited the Earth as the centre of the cosmos.

Copernicus
Nicholas Copernicus proposed a far more straightforward theory of the universe in 1514. Copernicus was a priest from Poland. He then released his design under an assumed name out of concern for a heresy charge. The Sun was supposed to be motionless in the universe’s centre, according to Copernicus. Planets and the Earth orbited the Sun in a sphere. This concept was not really considered until almost 100 years later. Galileo Galilei and Johannes Kepler began publicly endorsing this hypothesis at this moment. Copernicus’ theory that the Earth is not the centre of the cosmos was supported by the freshly invented telescope. Galileo noticed that Jupiter has many moons in its orbit.

This meant that not every celestial body needed to revolve around the Earth. Yet, some people continued to assert that the Earth was not the center of the cosmos. They claimed that the moons of Jupiter took incredibly convoluted trajectories around Earth, indicating that they circle Jupiter.

Newton
Newton’s Mathematical Foundations of Natural Philosophy was published in 1687. According to Hawking, this is conceivably the most important physical science article ever published. Newton offered a hypothesis for the motion of bodies in space and time in this book. A novel concept of universal gravitation was also explained by this theory. According to Newton, every celestial body in the universe is drawn to every other celestial body. The gravitational force increases with body size. Newton continued by demonstrating how gravity causes the Moon to orbit the Earth in an elliptical pattern. The Earth and the planets also orbit the Sun in elliptical patterns due to gravity.

These developments had been made before the 20th century, but there was still no sign of a cosmos that was growing or contracting. It was widely believed that either the universe had a finite age or that it had a stable state for all time. But some academics questioned the viability of a static, unending cosmos. For instance, Heinrich Olbers argued that in an endless, static universe, almost every line or side would finish on the surface of a star. As a result, even at night, one would anticipate that the entire sky would be as bright as the Sun. Only if the stars did not shine forever could this conclusion be avoided.

For example, they could have turned on at some finite time in the past.

The Expansion of universe

Many Galaxies
The Milky Way contains both the Sun and the surrounding stars. There was a long-held belief that the Milky Way contained the entirety of the cosmos. Edwin Hubble, however, showed that the Milky Way was not the only galaxy in 1925. He discovered numerous other galaxies separated by enormous distances. He had to determine the size of these vacant areas in order to demonstrate the validity of his theory.

Based on brightness, one can determine a star’s distance to Earth. The luminosity of a star and its distance from the Earth determine its brightness. Hence, if we know a star’s luminosity, we may use the apparent brightness to determine how far away it is. Hubble said that when stars were close enough for us to measure them, their luminosities were constant. We could presume they had the same luminosity if we discovered similar stars in another galaxy. Hence, we could determine how far away that galaxy is. If numerous stars in the same galaxy reported the same distance, we may reasonably be confident that our estimate is accurate.

This is how Hubble determined the separations between nine galaxies. We now know that there are 100,000,000,000 galaxies that can be seen by current telescopes, with our galaxy being just one of them. Each galaxy has a hundred billion million stars.

Increasing Universe

Hubble noticed that all of the galaxies he saw looked to have been redshifted. For astronomers, the concept of redshift is crucial. We can use it literally to mean: Stretching the light’s wavelength causes it to appear to be shifted towards the red end of the spectrum. These galaxies are all going away from us, so that’s what that means. Each galaxy also migrated away from us at a different rate depending on its distance. A galaxy travelled away from us more quickly the further it was from us. This discovery is one of the great intellectual breakthroughs of the 20th century, according to Hawking.

The Universe’s Cause and Destiny

Hawking was invited by the Vatican to a cosmology meeting in the 1980s. The Catholic Church understood that it should not obstruct scientific advancement after it silenced Galileo. Therefore they thought that a better strategy would be to consult with numerous cosmology specialists. Despite this, the Pope advised Stephen Hawking not to research the big bang. The big bang was seen by the Pope as the beginning of creation. Hawking refused to give in to this demand.

Big Bang’s Trendiest Model

This model presupposes that the cosmos can be described by Friedmann’s model.
The temperature of matter and radiation is falling due to the universe’s expansion. The average energy of the particles is measured by temperature. The particles move so quickly at high temperatures that they are not drawn to one another. Yet, the particles begin to agglomerate as they cool.
The universe had no size at the time of the big bang, hence it was probably extremely hot. The radiation would have had a lower temperature as the cosmos grew.
Despite this, the big bang would have happened at a temperature of roughly 10,000,000,000 degrees. The temperature of H-bomb explosions is this.
There were some protons and neutrons as well as photons, electrons, and neutrinos in the universe.
The temperature decreased as the universe continued to expand. The pace at which electron pairs were being produced would have decreased below the rate at which they were being destroyed by annihilation.
The temperature would have dropped to one million degrees within 100 seconds. The hottest stars have a temperature similar to this. Protons and neutrons would not have enough energy to escape the powerful nuclear forces at this temperature.
Together, these protons and neutrons. They created the heavier hydrogen and helium atom nuclei as well as trace amounts of lithium and beryllium.
The creation of helium and other elements would have ceased after a few hours of the big bang. The universe kept growing for the next million years or more.
The temperature eventually dipped to a few thousand degrees. The electromagnetic pull between the electrons and the nuclei was too strong for them to resist. They would have begun fusing to create atoms.
The universe kept growing and became cooler. Areas that were a little bit denser were slowed by greater gravitational attraction. This draw halted the expansion and brought about a recollapse. The atoms rotated as they collapsed due to the gravitational pull of matter outside of these zones.
The portions that were collapsing grew smaller and began spinning more quickly. They eventually span quickly enough to counteract the pull of gravity. This is one hypothesis for the origin of the disk-shaped revolving galaxies we observe today.

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