We know that the Sun is approximately 150 million kilometers away from Earth; it is a massive ball of plasma with a diameter of 1.39 million kilometers.
All celestial bodies in the Solar System revolve around the Sun. According to the law of universal gravitation, the mass of the Sun is about 1.891 × 10³⁰ kg, equivalent to 200 billion gigatons. As the only star in the Solar System, its massive size results in an internal temperature of around 15 million degrees Celsius and a pressure of 300 billion atmospheres. In the process of nuclear fusion, about 600 million tons of hydrogen are fused into 596 million tons of helium every second, with 4 million tons of matter being directly converted into energy and released. This energy provides light and heat to Earth.
The mass of the Sun is approximately 1.891 × 10³⁰ kg, equivalent to 200 billion gigatons.
Today, astronomers speculate through stellar evolution models that the Sun was born about 4.6 billion years ago when a massive molecular cloud collapsed. In its early days, the initial position of the Solar System was merely a cold nebula drifting in the universe. One day, it was disturbed by some kind of turbulence (a supernova explosion), causing the nebula to condense into a dense region. Under the influence of gravity, this dense region began to collapse. More and more nebulae gathered, ultimately reaching the conditions necessary for nuclear fusion to form the Sun.
According to stellar evolution models, we not only understand how the Sun was born but also its lifespan. Since the Sun is a G-type main-sequence star, the hydrogen it contains can burn for nearly 10 billion years. To date, scientists estimate that the Sun has been burning for 4.6 billion years, meaning that the Sun today has nearly 5 billion years of lifespan remaining. After approximately another 5 billion years, the fuel will be depleted, leading to the final stages of the star’s life, transitioning into the era of red giant stars. During the red giant phase, as fuel becomes increasingly scarce, the energy generated by the core will no longer be sufficient to maintain hydrostatic equilibrium, and the volume will expand 200 times, at which point Earth will be engulfed by the red giant star.
So, will humanity survive another 5 billion years? In reality, this is not likely!
We know that in the core of the Sun, a massive amount of hydrogen is gradually being converted into helium nuclei, which will lead to an increase in core density and pressure, causing the hydrogen burning process to accelerate, and the intensity and temperature of the Sun will rise. It turns out that the brightness of the Sun will increase by about 10% every billion years, and this 10% increase is enough to cause the oceans and lakes on Earth to evaporate and disappear, resulting in wildfires on the surface, leading to the extinction of life! Earth will no longer be a habitable area in the Solar System, and habitable zones will shift outward, meaning that humanity currently has only 1 billion years left.
However, it must be said that 1 billion years is a very long time for our lifespan. With the advancement of science today, humanity’s footprint may have spread to every nook and cranny of the Solar System, and they may be able to travel to other planets and even venture beyond the Solar System to explore the deeper cosmos.
So in a billion years, we have plenty of time to escape from Earth!
