The fastest robotic spacecraft (250,000 km/h).A car traveling on the open road (100 km/h).To visualize distances in space, it's also helpful to have a few real-world examples to imagine how fast you would need to travel to get somewhere. 1 light-year (ly) is the distance that a photon of light can travel through the vacuum of space in one Earth year, approximately 9.5 trillion km (5.9 trillion miles).įor more information, review the lesson measurement units in space.1 astronomical unit (au) is the average distance from the Sun to the Earth, approximately 150 million km (93 million miles).Tom Young, B.S.To understand distances in space, you should know about common measurement units such as the astronomical unit (au) and the light-year (ly). How about this: the edge of the universe is about 15 billion light years away from us! Can you even imagine how many miles away that is? The closest star to us is about four light years away. Now that you know what the distance is that light travels in one year you can also know the distance between objects in the universe.
Working eight hours per day at a rate of one number per second it would take you two hundred thousand years to get to number 5,865,696,000,000! This gets you across the United States two billion times which at our average speed of 60 miles per hour, would take nine trillion years! You can tell already that this is going to be huge! That number is 5,865,696,000,000. So, we take these two very large numbers and multiply them together to see how many miles light can travel in one year. This many miles means you could go back and forth across the United States over one thousand times! At 60 miles per hour it would take you 60 years! This many seconds is an even larger number than the number of miles light goes in one second! It would take you three years to get to number 31,536,000 if you could write one number per second for eight hours per day. Each hour has 60 minutes and each minute is 60 seconds long. In one year there are 365 days of 24 hours. If you did this going an average speed of 60 miles per hour you will need one year and three weeks! But light can do this same thing in one second! If you go back and fourth across the US 66 times you will have traveled 186,000 miles. Light travels at 186,000 miles every second! That is a huge number! If you were to write one number per second for eight hours a day without stopping to eat or to rest your hand it would take you six and a half days to get to number 186,000! And to think light travels that many miles in only one second! Another way to think about how large this number is, is to think about how many times you could go back and fourth across the United States. When you ask such a question in relation to a light year both meanings are important!Ī light year is the distance between two points in space that it would take light to travel when the distance between the two points in time are one year. The word 'long' can be used to mean both distance between two points in space as well as two points in time. This is a great question! I especially like the way in which you asked it. Gregory Ogin, Physics Undergraduate Student, UST, St. We can calculate this by multiplying the speed of light by 1 year (or 3.1557*10^7 seconds) to find the distance: What is a light-year and how long is 1 light-year?Ī light-year is defined as the distance that light can travel in 1 year.
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