A light year is a measure of distance equal to how far light travels in one Earth year. Because distances across the universe are so large, astronomers use light years. Without light years, discussing the distance between two stars would require the use of large, unruly numbers. Another measure of distance you may come across when learning astronomy is the parsec. It is equal to 3.26 light years. It is another way to simplify the numbers used to calculate and discuss astronomical distances. Using the common physics formula, distance equals rate times time or d = r x t, you can calculate how long a light year is: Light Year = (speed of light) x (one year). Since speed of light is represented by the variable “c”, you can rewrite the equation as d = c x t, where d is the distance of a light year, c is the speed of light and t is time.  If you want to know the distance of a light year in kilometers, you will need to find the speed of light in kilometers per second. If you want miles, you will need the speed of light in miles per second. You need to know the number of seconds in one Earth year for this calculation. Light in a vacuum travels at a velocity of 186,000 miles per second. This is the equivalent of 299,792 kilometers per second or 670,616,629 miles per hour. Here we will use the velocity in miles-per-second. For this calculation we will use the speed of light, c, equals 186,000 miles per second. This can be rewritten in scientific notation as 1.86 x 105 miles per second. To find the number of seconds in a year, you will do a series of multiplications by conversions units. To convert years to seconds you will multiply the number of days in a year times the number of hours in a day, times the number of minutes in an hour, times 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, we can rewrite this large number using scientific notation as 3.154 x 107. Now that you have defined the variables for speed of light and time, you can plug them into the equation d = c x t and solve for the distance of a light year. Replace c with 1.86 x 105 miles per second and time with 3.15 x 107 seconds.  d = c x t d = (1.86 x 105) x (3.154 x 107 seconds) d = 5.8 x 1012 or 5.8 trillion miles. If you wanted to calculate in kilometers, simply replace the speed of light with the speed in kilometers per second: 3.00 x 105. The time in seconds remains the same because there is no conversion required.  d = c x t d = (3.00 x 105) x (3.154 x 107 seconds) d = 9.46 x 1012 or 9.5 trillion kilometers.

Summary: Define the light year. Write the formula for distance. Define the speed of light. Calculate the number of seconds in a year. Plug variables into equation and solve. Calculate the distance in kilometers.


Take a tape measure and measure the distance from one corner to its diagonal, and then measure the diagonal between the remaining two corners. If you were to string lines across the corners you measured, they would form an "X". That's all there is to it! If your measurements do not equal one another, adjust the assembly until the diagonals equal one another.

Summary: Measure the diagonals from all four corners of the room. Know that if the measurements equal one another, your room is square.


Wood fillers are thick pastes that usually come in round tubs. Use a small putty knife to apply the filler into the depressions created by your screw heads, as well as any knots or imperfections in the wood. Scrape away the excess filler, as this will make sanding easier later.  Follow the product’s instructions for application and drying times. You can leave the screw heads exposed if you like, especially if you may want to remove the ladder-stairs later. Use a piece of fine-grit (150-180 grit) sandpaper or an equivalent sanding block. Rub the entire wood surface with light and even pressure. Keep sanding until the wood feels smooth to the touch.  If you’ve applied wood filler, wait until it’s completely dry before sanding it. You may need to sand a bit more aggressively to smooth out excess filler. For your safety, wear a dust mask and eye protection when sanding. If you’re painting the wood, apply a primer first and then 1-2 coats of your chosen paint. If you’re staining the wood, apply a small amount in an inconspicuous area first to check the color. Then use a brush or rag to apply the stain, and wipe away the excess with a cloth. If you want the structure to retain a natural look, it’s still advisable to apply a clear wood sealant, using the same techniques as you do for staining.
Summary: Apply wood filler to cover the depressed screw heads (optional). Lightly sand the entire ladder-stairs structure. Stain or paint the ladder-stairs to match the bunk set.