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Hikers, photographers, hunters, golfers, home astronomers, and nature lovers, if you have ever wondered how far away you are from a given object, estimating that distance may be easier than you realized. The length of your arm is roughly ten times the distance between your eyes. With this fact in mind, you can measure the approximate distance between yourself and almost any object.
Steps
Place yourself at a good vantage point. To estimate distance, you need a clear line of sight. Try to stand in a high place, like atop a hill or a few floors up in a building. If this isn’t possible, try to find a spot where no other objects are in between you and the object you are focusing on.
Estimate the horizontal length of the object. Here are some standard lengths that may help you:- Most average-sized cars are between 12 and 15 feet long.
- Mailboxes are usually around 1.5 feet long.
- Mature tree trunks are typically between 1 and 2 feet wide.
- The standard length of a trailer pulled by a semi-truck is 50 to 65 feet long.
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Hold your right arm out in front of you. Aim your arm toward the object, and try to keep it as straight as possible. Point your thumb up.[1]
Close your right eye. Keep standing as still as possible.
Align the left edge of your right thumb with the right edge of the object. Try to keep your head and arm perfectly still.[2]
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Switch eyes. Keeping perfectly still, close your left eye and look through the right eye. Your thumb will appear to have “jumped” to the left. This “jumping” phenomenon is called “parallax.”
Estimate how far the left edge of your thumb jumped. Did your thumb jump 3 times the length of the object? Half the length? Keep this number in mind. For example:[3]- If your thumb jumped 3 times the length of a building that you believe is 100-feet-long, then it jumped 300 feet.
- If your thumb jumped half the length of a 14-foot-long car, then it jumped 7 feet.
Multiply that number (the jump) by 10. This will give you the approximate distance you're looking for. For example:[4]- If your thumb jumped 3 times the length of a 100-foot building, or about 300 feet (91 m), then you would multiply 300 by 10 to conclude that the building is about 3,000 feet (914 m) away from you.
- If your thumb moved half the length of a 14-foot-long car, or about 7 feet (2 m), then you would multiply 7 by 10 to conclude that the car is about 70 feet (21 m) away from you.
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Community Q&A
- QuestionHow might astronauts use parallax?
Community AnswerTo find out how far away planets and stars are, or find the angle between two objects and find the distance between them.
Tips
References
About This Article
If you’ve ever wondered how far away you are from a given object, you can estimate the distance with your thumb and eyes. Start by holding your right arm out in front of you, pointing it toward the object you’re measuring to. Point your right thumb up and close your right eye. Keeping as still as possible, line up the left edge of your right thumb with the right edge of the object. Then, close your left eye and look through your right eye, which will make your thumb appear to have moved to the left. Estimate how far it looked like your thumb jumped. For example, if it looked like it jumped 3 times the length of a building that you think is 100-feet-long, then it moved 300 feet. Next, multiply the number from the jump by 10 to get the approximate distance you’re looking for. So, if your thumb jumped 300 feet, you can conclude that the building is about 3 thousand feet away from you. To learn how to calculate the length of basic objects, keep reading!
Reader Success Stories
"I had to judge a distance to be licensed for a school bus. Having no idea how far 500 feet ahead of me was holding me back. Using your method made me nail it! Thank you from a future bus driver."..." more
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