THE SUN

Why does it take 20,000 years for light to reach the surface of the Sun from its core, but just 8 minutes to reach the surface of the Earth?

The Sun is a giant ball of plasma that produces light and heat through nuclear fusion. Nuclear fusion is a process where hydrogen atoms fuse together to form helium atoms, releasing enormous amounts of energy. This energy travels in the form of photons, or particles of light.

However, the photons do not have a smooth journey from the core of the Sun to its surface. The core of the Sun is extremely dense and hot, with a temperature of about 15 million degrees Celsius. The photons collide with the atoms and molecules in the plasma, and get scattered in different directions. This makes them take a very long and random path, like a drunken walk. It can take them tens of thousands of years to reach the surface of the Sun. The surface of the Sun, called the photosphere, is much cooler and less dense than the core, with a temperature of about 5,500 degrees Celsius. The photons can escape more easily from the photosphere, and travel in a straight line towards the Earth and other planets. The distance from the Sun to the Earth is about 150 million kilometers, which is also called one astronomical unit (AU). It takes light about eight minutes and 20 seconds to travel this distance.

Therefore, it takes much longer for light to reach the surface of the Sun from its core than to reach the surface of the Earth from the Sun. This is because light travels much faster in empty space than in dense plasma. The speed of light in a vacuum is about 300,000 kilometers per second, but it can be slowed down by interacting with matter. The light we see from the Sun today was created thousands of years ago in its core. We are looking at a snapshot of the past when we look at the Sun. The Sun is constantly changing and evolving, and we can only observe its effects after a long delay.