The sun has been a major source of light and energy since the beginning of time. It fuels life on Earth by powering plant growth through photosynthesis, by providing us with the heat we need for warmth and by giving us a sense of time.
Each night as the sun sets, our world goes dark. The idea of sheer darkness after the sun goes down is foreign to most of us. That’s because mankind has developed different ways to provide lighting — from fires and torches in 70,000 B.C. to modern LED lighting.
On August 21, a similar celestial event will take place for a brief period when the moon obscures the sun and a moment of darkness blankets parts of North America. It will be the first solar eclipse that will be visible from the continental U.S. since 1918.
While we enjoy the brief period of darkness, we can also take the time to appreciate both the sun and how our sources of light have transformed over time.
Here are seven things to know about our world’s first light source: the sun.
1. The sun is actually white. Yes, the sun is actually white in color and not yellow. That’s because the sun gives off a lot of energy on wavelength scale (of color) from 390 nm to 700 nm, and when you mix all of these colors together, it produces white.
2. The sun emits different kinds of light. The sun’s energy emits three different kinds of light: ultraviolet, infrared and visible light. Ultraviolet and infrared lights are both invisible and a type of electromagnetic energy. Although visible light is also a form of electromagnetic radiation, it is visible to the human eye through a spectrum of colors.
3. Sunlight forms rainbows. All six colors of red, orange, yellow, green, blue and violet are different wavelengths of the sun’s light.
4. Sunlight supports plant life. Plants use the sun’s light for photosynthesis, a process in which plants and organisms convert light into chemical energy for fuel.
5. It takes 8 minutes and 20 seconds for the sun's light to reach Earth. Earth is 150 million km from the sun, and light travels at 300,000 km/sec. When you divide 150 million km by 300,000 km/sec, you get 500 seconds, which is equal to 8 minutes and 20 seconds.
6. The sun can burn you. Exposing yourself to too much ultraviolet light from the sun can kill skin cells, which we often refer to as sunburns.
7. Sunlight can be mimicked by modern lighting technology. LED lighting can be adjusted to mimic the light of the sun and even transition from warm to cool throughout the day.
As you’re watching the solar eclipse on August 21, take a second to think about how far we’ve come — from using the sun’s light and energy to creating electricity that powers man-made lighting.