Light and Sound Speed

Light speed, light is the fastest thing that science knows till today. Light speed in vacuum is 186,282 mi/s (about 300,000 km/s) and it equal to 670,616,629 mi/hour. It means if you travel in light speed, you can move around the earth 7.5 times in one second.

Scientists use the speed of light to measure the distance between places in the space (light-year). Light-year is simpler that it seems to be. For example, moonlight reaches our eye in 1 second, that is mean the distance is 1 light-second, the sunlight reaches our eye in 8 minutes, so the distance is 8 light-minutes. Light from the nearest star system Alpha Centauri needs approximately 4.3 years to reach earth, so the distance is 4.3 light-years. In simple language, it's the time that light needs to arrive.

Sound speed, sound is not fast as the light. Sound speed is about 340 m/s (0.2 mi/s). Temperature can affect the speed of sound. For example, 340 m/s is at 15 Celsius (59 F), if the temperature increased, sound speed will increase too. At 35 c (95 F)  sound speed will be about 352 m/s (0.22 mi/s). Also, sound speed is varying depend on the carrier, if the sound moves through liquids like water, then its speed will be about 4 times its speed in air.

One of the benefits of comparing light to sound speed is calculating a roughly distance between two points. Since light has an extreme high speed, so it needs about zero second to arrive to our eye ( time is ignorable). For example, when we see a thunderbolt, we hear the sound after couple seconds from seeing the light (because light is faster), all we need is counting the different seconds and multiply the number by 340, we will have the distance to the thunderbolt. In wars, they use this technique(counting the seconds between light and sound of the enemy’s guns) to discover enemy places at the night.

 work cited

             Howell, Elizabeth. "What Is the Speed of Sound?" LiveScience. TechMedia Network, 31 May 2013. Web. 24 July 2016. <http://www.livescience.com/37022-speed-of-sound-mach-1.html>
             NASA. "Ask Us." NASA's Cosmicopia. NASA, 29 Dec. 2006. Web. 24 July 2016. <http://helios.gsfc.nasa.gov/qa_gp_ls.html>
             Redd, Nola Taylor. "How Fast Does Light Travel? | The Speed of Light." Space.com. Space.com, 22 May 2012. Web. 24 July 2016. <http://www.space.com/15830-light-speed.html>.