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How many light years old are you?. So If light years aren’t a measurement of time, then what do they measure?

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Presentation on theme: "How many light years old are you?. So If light years aren’t a measurement of time, then what do they measure?"— Presentation transcript:

1 How many light years old are you?

2 So If light years aren’t a measurement of time, then what do they measure?

3 What is a Light Year? What does a light year measure? A light year is the distance light travels through space in one year! Light travels at a speed of 186,000 miles per second or 300,000 kilometers per second, which means it can travel around the Earth 7 times in a second! Figure out how many miles light can travel in a light minute, light hour, light day, light week, light month and light year.

4 What is a Light Year? One Light year = 5,879,000,000,000 miles or 10,000,000,000,000 km. So light travels 5,879,000,000,000, miles or almost 10,000,000,000,000 km in one year. The approximate conversion from light years to km is light years x 10,000,000,000,000 km

5 Why measure distances in light years? Astronomers use light years instead of kilometers to measure interstellar distances because the amount of kilometers would be such a ridiculous number that it would be hard to understand. What unit of measurement would you use to measure the distance around the world? Kilometers or millimeters? Explain! For the same reason light years are used to measure the distances between stars instead of miles/kilometers because interstellar distances are so vast.

6 Putting light years into perspective At 55 miles-per-hour, it would take over 50 million years to get to Proxima Centauri! You can never see Proxima Centauri as it is now, only as it was 4 years ago. Proxima Centauri is approximately 40 trillion km away or approximately 4 light years.

7 Putting light years into perspective The Andromeda Galaxy is the most distant object you can readily see with the naked eye. The light your eye is receiving left the galaxy about 2 million years ago. If the galaxy disappeared by some mysterious means, the people on Earth wouldn’t know for another 2 million years

8 Putting light years into perspective When you look out into space, you are looking back in time. There is absolutely no way to know exactly what an object out in space looks like right now!

9 Putting light years into perspective It is impossible to know exactly what an object looks like in the present because it takes TIME for the light to reach our eyes. It is not instantaneous When astronomers spot an explosion on the sun, they’re not seeing it in real time; the light from the explosion takes 8 minutes to get to Earth. Your picture should reflect this point

10 Why is it currently impossible to travel outside of our Milky Way Galaxy?


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