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Touching the Sun – Chris Lintott (Gresham College, Jan 2025)
Introduction
In “Touching the Sun,” astrophysicist Chris Lintott takes the audience on an enlightening journey through humanity’s relationship with the Sun. From its cultural symbolism to the cutting-edge science of solar dynamics, Lintott discusses how our understanding of the Sun has evolved—from early theories of gravitational collapse to modern revelations about nuclear fusion, solar storms, and space weather prediction. His lecture emphasizes both the awe-inspiring beauty of our nearest star and its potential threats to our modern technological society.
The Sun in Human Imagination and Exploration
The lecture begins with a simple truth: wherever humanity has gone—on Earth or into space—the Sun remains a familiar, comforting presence. From Mars rover photos capturing sunsets on the Red Planet to children’s drawings featuring the Sun with smiling faces and radiant beams, our relationship with the Sun transcends science. It’s a symbol of life and continuity.
Even in the harsh alien environment of Mars, a Martian sunset with a familiar glow resonates deeply with human observers. It reminds us that the Sun, in its simplicity and warmth, connects all human experience.
Early Scientific Theories and the Kelvin-Helmholtz Dilemma
Before the discovery of nuclear fusion, scientists struggled to explain the Sun’s longevity. The dominant theory in the 19th century was gravitational contraction, formulated into what is now known as the Kelvin-Helmholtz timescale. According to this model, the Sun could only have shone for tens of millions of years—a duration incompatible with geological findings.
Scottish geologist James Hutton’s studies of rock formations at Siccar Point provided stark evidence that Earth’s geological processes—and by extension, the Sun’s lifespan—must have spanned hundreds of millions, even billions, of years. This contradiction set the stage for a major scientific breakthrough.
Fusion: The Sun’s Real Power Source
The discovery of nuclear fusion in the 20th century resolved the age paradox. Scientists learned that the Sun converts hydrogen into helium through fusion in its core, releasing immense energy in the process. This discovery extended the Sun’s projected lifespan to around 10 billion years, aligning with geological and evolutionary data.
Nuclear fusion not only explains the Sun’s longevity but also offers a potential energy source for Earth—if humanity can replicate the process efficiently.
Watching the Sun in Real-Time
Modern technology allows scientists to observe the Sun’s surface in detail. Instruments like the Solar Dynamics Observatory (SDO) and the Solar and Heliospheric Observatory (SOHO) provide ultraviolet and X-ray imagery, revealing a constantly shifting landscape.
Through various wavelengths, solar physicists observe features such as sunspots, bright patches of plasma, and twisted magnetic streamers. Immense loops—each capable of encompassing Earth—are visible rising from the Sun’s surface. These are not static features; they’re part of a turbulent, high-energy system.
Temperatures Beyond Imagination
X-ray and extreme ultraviolet imaging reveal the Sun’s extreme temperatures. Some solar regions, especially those associated with flares and coronal mass ejections (CMEs), can reach several million degrees Celsius.
This intense heat drives solar material into space and creates dynamic structures that change on a minute-by-minute basis. Such events are monitored closely because of their potential to affect technology on Earth.
Comets and the Sun’s Gravitational Pull
The Sun isn’t just emitting material—it also absorbs it. Over the past two decades, scientists have observed thousands of comets falling into the Sun. These events are visible thanks to instruments that block out the Sun’s main disk, allowing faint comets to be seen as they plunge inward.
This continuous inflow demonstrates that the Sun still interacts with its surroundings in powerful, visible ways.
The Threat of Coronal Mass Ejections
CMEs are colossal eruptions from the Sun’s corona that send billions of tons of charged particles into space. When directed at Earth, they can severely disrupt satellites, power grids, and communication systems.
Lintott points out that while CMEs have existed for millennia, their potential for disruption has increased due to our dependence on electronics and space-based technologies.
Stealth CMEs: Hidden Threats
In an intriguing development, scientists like Jenny O’Kane have discovered “stealth” CMEs. These ejections originate in otherwise quiet regions of the Sun and lack the obvious precursors of typical solar storms. Despite their subtlety, stealth CMEs carry enough magnetic energy to impact Earth’s magnetic field.
Their discovery has added complexity to solar forecasting. Predicting their occurrence and impact remains a challenge for solar weather scientists.
Solar Forecasting and Public Safety
Agencies like the UK Met Office now include solar forecasts as part of their services. With multiple solar images taken daily and interpreted in real time, predictions of space weather help protect satellites and power grids.
These efforts underscore the growing importance of space weather as both a scientific and civil concern.
Conclusion: Awe and Responsibility
Chris Lintott ends the lecture with a reflection on the Sun’s dual role. It is, simultaneously, a celestial beacon that inspires art and imagination and a volatile star that can disrupt global systems. Understanding it better helps humanity thrive in a solar-powered world.
Advancements in solar science are ongoing and require international collaboration. The Sun, ever familiar, remains a frontier of active research—one that influences every aspect of life on Earth.