# In a manner similar to how the light year is defined, define a "car day'' as how far a car will travel in one day (24 hours) moving at a speed of 105 kilometers/hour (65 miles/hour). How far would...

**In a manner similar to how the light year is defined, define a "car day'' as how far a car will travel in one day (24 hours) moving at a speed of 105 kilometers/hour (65 miles/hour). **

**How far would a "car day'' be in kilometers? **

**How many ''car days'' across is your home state (specify if it is the north-south size or the east-west size)?**

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### 1 Answer

A "light year" is commonly interpreted as a measure of time, but it is actually a measure of distance; the distance that light (or more properly, a photon of electromagnetic radiation in a vacuum) travels in one year. This is a large number, and we need it to be a large number in order to conveniently describe the vast distances in the universe.

One light-year is approximately 9.5 trillion kilometers, or 9.5 x 10^12.

The car is traveling a distance of 105 kilometers in an hour. There are 24 hours in a day, so we multiply 105 by 24 to find the total distance traveled; 105 x 24 = 2520km. This is the length of a "car day".

My home state, California, measures approximately 1200km from its north to south end. We can already tell that this distance is less than one "car day". We only need to find the ratio between the two, via division.

1200 / 2420 = .496 car days.

You could drive from one end of the state to the other in half a day. This seems like a ridiculous proposal, but remember that you're supposedly travelling at a constant 105kph, in a straight line, for 12 hours...not very likely for the average human.