Speed measures the distance traveled in a certain amount of time. Scientists use the metric system, thus the speed of light is 300,000 km per sec. This is read as three hundred kilometers per second.
Try This!
* Say the words “One thousand and one.”
It takes about one second to say these words. During this time, light given off by the Sun has traveled about 300,000 km. Even so, this light has not reached Earth yet. The distance from the Sun to Earth is about 8 light-minutes. Light-minutes sounds more like a time measurement instead of distance, but it mean the distance that light travels in a period of 8 minutes. At a speed of 300,000 km/sec, light would travel about 149 million kilometers in 8 minutes.
The Sun is Earth’s closest star. The next closest star to Earth is Proxima Centauri, which is about 4.21 light-years. This distance is equal to how far light travels in 4.21 years, which is equal to 270,000 times the distance between the Earth and the Sun.
The Hubble telescope orbits Earth at a distance of about 600 km above Earth. At this distance, the atmosphere is very thin and objects in space are more clearly viewed. The colorful photo shown is a small part of the Orion Nebula . This nebula [a cloud of gases (mostly hydrogen) and dust] is about 5,500 light-years away from Earth. This means that the photo shows how this area looked 5,500 years ago. This is so COOL!!!
For more information about astronomy, see Janice VanCleave’s Astronomy for Every Kid
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