At what speed light travels? How do scientists measure the exact speed?

We may already know that the speed of light is the fastest here on Earth. Scientists believe that there is nothing that could go faster than the speed of light. However, exactly how fast is the speed of light compared to other rates? Also, if the speed of light is so fast, then how did scientists measure its speed? 

These are the common question that may come up once we learned about the speed of light. Aside from this, light itself has several unique characteristics that may catch our interests. 

In our topic, let us look into the characteristics of light, mainly the speed of light.

What is light?

The answer to this question may be a bit obvious since we all know what light is. In simple terms, light is what helps us see through the dark; it is the opposite of darkness as we sometimes say. 

Our world, especially in our modern time, we are surrounded by light.  Our primary source of light is our sun, as it gives us heat and light during the day, and living in our world is unimaginable without it. At night, we still have our human-made light, varying from LED, filament bulbs, fluorescent, and many others. These technologies are what gives us light at night. 

However, these descriptions are shallow compared to what light is. A more profound definition of light is – it refers to electromagnetic radiation that the human eye can detect. There are different types of electromagnetic radiation, wherein they vary from their wavelength. For example, the microwave oven sends out low energy radio waves with wavelengths that we could measure in meters. Then we have the visible light, which has wavelengths that are shorter compared to those of microwaves. The energy from these electromagnetic waves is moving in the speed of light. 

What is the speed of light?

Now that we already have a bit of knowledge about what light is, let us ask the question – what is the speed of light? 

The speed of light is one of the greatest mysteries and wonders of science. The speed of light holds several scientific principles just by studying it. 

For starters, the speed of light travels in a vacuum by 186,282 miles per second or 299,792 kilometers per second. Because of this uncomparable speed, light is undoubtedly the fastest among anything. One way to simply define the speed of light is you can travel around the world seven and a half times in just one second – considering you could travel at the speed of light. 

Because of these extreme lengths, scientists used the speed of light as a unit of measurement called the light-year. Based on our example earlier, a light-year is the distance that light could travel around the Earth in one whole year. Just learning the definition would make us imagine how vast a light-year would be, which is roughly six trillion miles or nine trillion kilometers. This distance is far greater than Earth, and scientists mainly use it to measure the lengths and distance of heavenly bodies. 

For example, our sun is 8.3 light-minutes away from Earth. Wherein its light will take eight minutes to reach our planet. Then we have our moon, which is only 1.25 light-second away from our planet. It means that the moon’s light only takes about one second to reach us.  

How was the speed of light measured?

We already know about the speed of light. Upon realizing its exceptional speed, another question pops up. If the light is so fast, then how do we measure it?

Galileo was the first person to conduct a study about the speed of light. He made his study in 1667; however, it was unsuccessful. 

Just three years after, a Danish astronomer Olaus Roemer made another study about the speed of light. However, this time the study produced significant results. He observed the eclipses of the moons of Jupiter to measure the speed of light. He said that when the Earth is moving away from Jupiter, it increases the duration between eclipses; while moving towards Jupiter decreases its time.

This study was the first successful measurement of the speed of light. After the success of Roemer, various scientists conducted further tests to measure the speed of light.

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