From the Sun to Earth
Published on 18 Jun 2021

Why does the sun emit light? How can light travel through space and how long does it take to travel?

The sun is approximately 4.6-billion-year-old. It is a hot ball of glowing gases with around 73% hydrogen and 25% helium, with some heavier elements including oxygen, carbon, neon and iron.

At the core, the temperature is so high at 16 million degree Celsius, sustaining the thermonuclear fusion of hydrogen to helium. The energy produced during the nuclear fusion produces almost all sorts of electromagnetic radiation of various wavelengths and amounts of energy: from X rays to UV lights, visible lights to infrared and radio waves, etc.

The electromagnetic radiation travels in photons, the basic units that make up all light. It travels in space in the form of oscillating waves. Space is vacuum and allows the photons to travel more efficienctly with less loss of energy on the way. The speed of light is at approximately 300,000 kilometres per second in space. The distance from the sun is about 150 million kilometres. So in theory, it would take 8 minutes and 20 seconds for light to travel from the sun to earth.