At first glance you might believe that the light year (al) is a measure of time that takes into account the earth year. In reality it is a unit of distance measurement that uses the speed of light as a reference criterion. If you have ever told a friend that you are five minutes from their house, you have already used a time quantity to quantify a length. The distances between stars and other celestial bodies are very large, so astronomers use the light year, since it represents a much larger unit than kilometers. To calculate what a light year corresponds to you simply multiply the speed of light by the number of seconds there are in a year.
Steps
Method 1 of 2: Calculate the Light Year
Step 1. Define a light year
It corresponds to the distance traveled by light in one Earth year. Since the spaces in the universe are huge, astronomers prefer to use this unit of measurement; if it did not exist, discussions about the distances between two stars would have to involve the use of huge and complex numbers.
The parsec is another unit of distance measurement that is used in astronomy; corresponds to 3, 26 al and allows you to further simplify the numbers used in the calculations
Step 2. Write the distance formula
Using the elementary knowledge of physics, you can say that distance equals speed times time: S = v x t; consequently, 1 al is equal to the speed of light for one year of time. Since the speed of light is represented by the letter "c", you can rewrite the previous equation as S = c x t, where "S" is distance and "t" is time.
- If you want to know the value expressed in kilometers of 1 per, you have to find the speed of light expressed in kilometers per second (km / s); if you want to know it in miles, you have to consider the speed expressed in miles per second.
- You need to know how many seconds there are in an Earth year to continue with the calculations.
Step 3. Define the speed of light
Light travels in a vacuum at a speed of 299,792 km / s (equivalent to 186,000 miles per second or 670,616,629 miles per hour). This article considers the speed expressed in km / s and miles per second
For the calculations described in the examples we consider the speed of light equal to 299.792 km / s, which, rewritten in scientific notation, corresponds to about 3 x 105 kilometers per second or 186,000 miles per second, which equals 1.86 x 105.
Step 4. Calculate the number of seconds present in a year
To do this, you need to do a series of multiplications to convert the time units. First, multiply the number of days in a year by the number of hours in a day; then, multiply the product obtained by the number of minutes in an hour and finally by the number of seconds in a minute.
- 1 year x 365 days / year x 24 hours / day x 60 minutes / hour x 60 seconds / minute = 31,536,000 seconds.
- Again, you can rewrite a large number in scientific notation: 3, 154 x 107.
Step 5. Enter the known information into the equation and perform the mathematical operations
Now that you've defined the speed of light and time variables, you can substitute them into the formula S = c x t and solve the multiplication. Write 1.86 x 105 miles per second instead of "c" and 3, 154 x 107 s instead of "t".
- S = c x t.
- S = (1.86 105) x (3,154 x 107).
- S = 5.8 x 1012 that is 5800 billion miles.
Step 6. Calculate the distance in kilometers
In Italy the metric system is used, therefore it uses the value of the speed of light expressed in kilometers per second: 3, 00 x 105. The time remains expressed in seconds because it is not necessary to proceed with any conversion.
- S = c x t.
- S = (3, 00 x 105) x (3,154 x 107).
- S = 9.46 x 1012 that is 9,460 billion kilometers.
Method 2 of 2: Converting Distances to Light Years
Step 1. Identify the distance you want to convert
Before starting you need to make sure that the value is expressed in kilometers (or in miles if you are working with the imperial system). It doesn't make much sense to turn small distances into light years, but you can if you're curious about the equivalent.
- To convert feet to miles, remember that there are 5280 feet in a mile: "x" feet (1 mile / 5,280 feet) = "y" miles.
- To convert meters to kilometers, simply divide the value by 1000: "x" m (1 km / 1,000 m) = "y" km.
Step 2. Determine the right conversion factor
You have to identify the units of measure for the distance you want to express in light years. If you are considering values in kilometers, you must use a different conversion factor than the one you would use to work with miles.
- To convert kilometers into light years you have to use this factor: 1 al / (9.46 x 1012 km).
- To convert miles into light years, apply this factor: 1 to / (5.88 x 1012 miles).
Step 3. Multiply the original distance by the conversion factor
Once you have determined the right one, you can multiply it by the distance data and convert the value into light years; when the numbers are large, it is best to use scientific notation.
- For example: if an object is about 14, 2 x 1014 miles from earth, how many light years is it?
- Use the conversion factor for miles: 1 to / (5.88 x 1012).
- Multiplication: (14, 2 x 1014) x [1 / (5, 88 x 1012)] = 2, 41 x 102 = 241 al.
- The object is located at 241 al.
Step 4. Get help
You can always ask for the support of the teacher and your classmates. There are many online and textbook resources to help you perform these kinds of conversions; if you need it, do not hesitate to use it.
