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Using a scientific calculator to calculate values from Light-Year distance equations - Succeed in Physical Science. Also refer to physics, speed of light, velocity, miles, kilometers, seconds, Ron Kurtus, School for Champions. Copyright © Restrictions

# Light-Year Calculations

by Ron Kurtus (29 September 2006)

A light year is the distance light travels in one year of time. You can use our scientific calculator to determine the distance of a light year in either miles or kilometers.

Questions you may have include:

• How many miles is a light-year?
• How many kilometers is a light-year?

This lesson will answer those questions. There is a mini-quiz near the end of the lesson.

## Process

To find the distance traveled, you use the equation d = vt, where

• d = distance in kilometers or miles
• v = velocity or speed in miles/year or km/year
• t = time in years
• vt is v times t

For velocity, we use the speed of light. For t, we use 1 year.

The speed of light (c) is approximately 186,000 miles per second or 299,800 kilometers per second.

Since we are talking about a light-year, we need to find the speed of light in miles/year or kilometers/year. You do that by determining how many seconds there are in a year:

• 1 minute = 60 seconds
• 1 hour = 60 minutes
• 1 day = 24 hours
• 1 year = 365 days (not counting leap years)

Therefore 1 year = 365 * 24 * 60 * 60 seconds

And 1 light-year =

• seconds in a year * 186,000 miles/second or
• seconds in a year * 299,800 km/second.

Note: Since the values of c are approximates, your value for the distance d can be rounded off. You don't need all those digits, since the outcome is also an approximate.

## Calculation

Help on using the calculator

#### Seconds in year

First find the number of seconds in a year by multiplying 365 * 24 * 60 * 60. Press = and then save it to memory (M+).

#### Distance in miles

Multiply (*) by the speed of light in miles per second.

Round off this number.

#### Distance in kilometers

Clear all (AC).

Recall memory (MR) and multiply by the speed of light in kilometers per second.

Round off this number.

## In conclusion

You have determined the distance light travels in a year.

Reader Questions and Feedback | Where can you go from here?

Apply the techniques elsewhere

## Resources

The following resources provide information on this subject:

### Websites

Physical Science Resources

### Flash programmer

The calculator was developed in Macromedia Flash by Atul Dabke in India.

## Mini-quiz to check your understanding

1. How many seconds are there in a year?

365

31536000

365250000

2. Approximately, what is a light-year in miles?

5,865,696,000,000 rounds to 6,000,000,000,000 miles

186,000 rounds to 200,000 miles

586,987,000 rounds to 600,000,000 miles

3. Approximately, what is a light-year in kilometers?

9,461,227,000 km

9,454,492,800,000 rounds to 9,500,000,000,000 km

10,000,000,000,000,000 km exactly

If you got all three correct, you are on your way to becoming a champion in science. If you had problems, you had better look over the material again.

## What do you think?

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## Students and researchers

www.school-for-champions.com/science/calculations/light-year.htm. Please include it as a reference in your report, document, or thesis.

## Where can you go from here?

Physical Science topics

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