Kyo 's Key Ideas from A Brief History of Time
by Stephen Hawking

Later, in 1929, Edwin Hubble discovered that galaxies are moving away from each other, suggesting that the universe is expanding and originated from an infinitely dense point, a concept compatible with the idea of God, according to Hawking.

Hawking highlights science's ultimate goal: to unify all theories into one comprehensive explanation. Currently, scientists rely on two major partial theories: the general theory of relativity, which addresses gravity and large celestial bodies, and quantum mechanics, which deals with the smallest known particles. However, these theories are inconsistent, and the quest for a unifying theory continues to fulfill humanity’s deep desire to understand its origins.

Newton’s concept of motion, forces, and relative distance challenged the notion of absolute space, much like the observations of a bouncing ping-pong ball on a moving train vary depending on the observer's location.

The idea of absolute time was further overturned in 1865 when James Clerk Maxwell discovered light’s wavelengths,

Later refined by Albert Einstein’s theory of relativity, which demonstrated that light’s speed is constant and that massive objects warp space-time. This means neither space nor time is absolute.

Einstein also introduced the cosmological constant, an anti-gravity force to explain the static universe, a notion later abandoned when Hubble showed galaxies moving apart. Russian physicist Alexander Friedmann proposed models of the universe, finite and infinite, and his work supported the Big Bang theory.

Wider acceptance of this theory followed Roger Penrose's studies on black holes, which Hawking extended to suggest a similar origin for the universe.

These advancements dismantled earlier deterministic views, like those of the Marquis de Laplace, who believed that perfect knowledge of the universe's state could predict everything.

Werner Heisenberg’s uncertainty principle, which revealed the impossibility of precisely measuring a particle’s position and velocity simultaneously, further established the probabilistic nature of quantum mechanics.

Scientists then discovered particles like electrons, protons, and neutrons, and Murray Gell-Mann’s 1969 Nobel-winning work identified quarks as their constituents.

Black holes, a recurring theme, illustrate entropy and the laws of thermodynamics. John Michell in 1783 theorized that massive stars could trap light with their gravity. This idea evolved into the concept of event horizons and singularities, where infinite density disrupts physical laws. Hawking’s work demonstrated that black holes emit heat and particles, making them potential energy sources.

Hawking also delves into the universe's origins, rejecting the idea of a singular beginning, positing instead that the universe has no boundary.

Various models describe its early state, with the Big Bang model suggesting that infinite heat and rapid particle movement eventually cooled to form galaxies, stars, planets, and life.

Hawking discusses three arrows of time:

Thermodynamic (disorder increases)

Psychological (memory formation)

Cosmological (universe expansion)

Even if the universe contracts, disorder would still increase, meaning time wouldn’t reverse. Advanced civilizations might manipulate space-time for time travel through wormholes or Einstein-Rosen bridges, but such ideas remain theoretical. The search for a unifying theory, such as string theory, continues. String theory envisions particles as waves on one-dimensional strings, requiring additional dimensions to function.

While incomplete, current theories move closer to explaining existence.

Ultimately, Hawking emphasizes that understanding why anything exists at all would allow humanity to grasp “the mind of God.”