The Slowness of the Speed of Light

A Nasa scientist has created these animations to show how to change the perception of the human dimension by looking at the dimensions of the Cosmos, without even going too far: showing how long a ray of light travels the circumference of the Earth, the Earth- Moon distance, and the Earth-Mars distance. Here are the journey times traveling at 299.792 km per second, which is the maximum possible speed.


Traveling at speed’s light on Earth would be too much fast: in a second the light goes around the equator 7 and a half times, neither the time to think about where to go that you have already arrived. Modern supersonic aircrafts take several hours to take a ride around the planet. Also the Space Shuttle, out of the atmosphere, took over an hour. 


To reach the Moon, light takes just over a second (1.3 seconds light). A trip more comfortable than the Apollo missions, which took three days. From the Moon, the astronauts in contact with the Earth had to wait more than two seconds to receive an answer: in a second their voice (converted into radio signal) arrived on Earth, and then, if there was someone ready to give a quick answer , another second before receiving the answer.


The Earth-Mars distance depends on the position of the two planets, on their respective orbits. In this animation is depicted the best scenario: the moment when Mars is closer to the Earth, only 54.6 million km. Our ray of light always travels at its fixed speed, from beginning to end, but the distance begins to be relevant: it takes more than 3 minutes to reach its destination. This means that after sending a command from the Earth to the rovers we have on the Red Planet, we must wait at least 6 minutes to see if and how the command was executed. From the Sun, a ray of light reaches the Earth in 8.317 minutes (on average, because the Earth’s orbit is slightly elliptical, the distance changes according to the period). To get Neptune (the outermost planet of the Solar System, after the expulsion of Pluto from the family of the planets) the light takes more than 4 hours, while a signal that started from Voyager 1 would take over 20 hours of light to reach up to us.

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