#### Stephen Hawking (University of Cambridge Professor) – My life in physics | Cambridge University Cosmology (Jan 2021)

#### Chapters

#### Abstract

Exploring the Universe: The Legacy of Stephen Hawking in Physics and Cosmology – Updated Article

Stephen Hawking’s remarkable journey in physics and cosmology, marked by his profound contributions despite facing immense personal challenges, stands as a testament to human resilience and intellectual curiosity. From challenging the steady-state theory and refuting the bouncing universe theory to his groundbreaking work on black holes and the information paradox, Hawking revolutionized our understanding of the universe. His work extended to proposing the no-boundary proposal in cosmology, offering new insights into the universe’s origins and its structure, as evidenced by the cosmic microwave background. Hawking’s legacy, encapsulated in his popular science communication, not only advanced our scientific knowledge but also inspired a deeper public interest in the mysteries of the cosmos.

Stephen Hawking’s Early Career and Challenges

A Serendipitous Path to Cosmology:

Stephen Hawking’s cosmological journey began with a fortuitous change in his doctoral supervision at Cambridge, leading him to delve into the then-emerging field of cosmology.

A Diagnosis and a Turning Point:

Diagnosed with a debilitating illness at a young age, Hawking found motivation in his personal life, transforming his prognosis into a driving force for his scientific pursuits.

Major Theoretical Contributions

Unraveling the Mysteries of the Universe:

Hawking’s early work focused on the fundamental question of the universe’s beginning, challenging existing theories like the steady-state model and the bouncing universe concept.

Penrose’s Approach and Singularities:

Collaborating with Roger Penrose, Hawking applied new methods in general relativity, demonstrating the inevitability of singularities and the universe’s origin in a big bang.

Breakthroughs in Black Hole Physics

Black Hole Properties and the Event Horizon:

Hawking’s shift to black hole research led to significant insights into their properties, including the event horizon and the no-hair theorem, simplifying their characterization.

Gravitational Wave Observations:

The detection of gravitational waves offered a practical avenue to test Hawking’s theoretical predictions about black holes, confirming the robustness of his theories.

The Information Paradox and Quantum Theory

Black Hole Entropy and the Information Paradox:

Hawking’s proposal of black hole entropy and Hawking radiation raised the information paradox, questioning the fundamental principles of quantum mechanics.

Combining General Relativity and Quantum Theory:

Hawking sought to harmonize general relativity with quantum theory, using the Euclidean approach to address the singularity problem and predictability issues in cosmology.

Hawking’s Impact on Cosmology

Contributions to Inflation Theory and Precision Cosmology:

Hawking’s work on inflation and the no-boundary proposal provided a framework to understand the universe’s structure, as evidenced by satellite observations of cosmic microwaves.

The No-Boundary Proposal and Inflation:__Dissatisfied with the initial inflationary scenario due to its singularity, Hawking collaborated with Jim Hartle to introduce the no-boundary proposal, a singularity-free space-time using the Euclidean approach__. This proposal predicted a burst of inflation, with tiny departures leading to the structures we observe. __Current observations align with the proposal, but the detection of gravitational waves generated during the rapid expansion phase is yet to be verified__.

Personal Reflections and Scientific Communication

Stephen Hawking’s Reflections:

In his writings, notably “A Brief History of Time,” Hawking emphasized the importance of scientific communication and encouraged public interest in cosmological exploration.

Importance of scientific communication:__Stressed the significance of scientists explaining their work, particularly in cosmology. Urged the public to observe the stars and contemplate the universe’s existence. Curiosity and perseverance are key to overcoming life’s difficulties__.

A Legacy Beyond Science

Stephen Hawking’s enduring legacy in physics and cosmology transcends academic circles, inspiring generations to look beyond our planet and ponder our place in the universe. His life’s work, characterized by overcoming personal adversity and a relentless pursuit of knowledge, not only reshaped our understanding of the cosmos but also highlighted the importance of perseverance, curiosity, and the joy of discovery.

Notes by: Hephaestus