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A light year is a measure of distance, not speed. The word 'year' seems strange, I know. Asking 'how fast is a light year' is like asking 'how fast is a mile?' In a vacuum, light travels about 186,000 miles in one second. The moon is roughly 240,000 miles away, for comparison. So in one second, light from earth would make it most of the way to the moon! Now let light travel for one full year, and you could figure out how far that is. The distance would be called one light year.
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LaoA light-year is defined as the distance that light can travel in 1 year. We can calculate this by multiplying the speed of light by 1 year (or 3.1557*10^7 seconds) to find the distance:
d = c*t
=(2.9979*10^8 m/s)*(3.1557*10^7 s)
=9.4605*10^15 meters
or ~9,500,000,000,000 kilometers
or ~5,900,000,000,000 miles
or ~63,279 au
A light year is a measure of distance, not speed. The word 'year' seems strange, I know. Asking 'how fast is a light year' is like asking 'how fast is a mile?' In a vacuum, light travels about 186,000 miles in one second. The moon is roughly 240,000 miles away, for comparison. So in one second, light from earth would make it most of the way to the moon! Now let light travel for one full year, and you could figure out how far that is. The distance would be called one light year.
"Light Year" is not a speed. It's a length or distance, just like a foot or a mile or a kilometer. It is the distance that light can travel in one year.
The speed of light is about 186,000 miles (300 million km) per second.
At that rate, the distance in one light-year is about:
5,878,700,000,000 miles ("5 trillion 878 million" etc.)
9,460,890,000,000 kilometers ("9 trillion 460 million" etc.)
(This shows you why it would be tough to use miles or kilometers to talk about distances from earth to stars ... the numbers would be too hard to handle. That's why the 'light-year' was invented.)
You might say the speed of light is 1 light-year per year
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How long does it take for a lightyear to travel?
A lightyear is a unit of distance, not time. It represents the distance that light can travel in one year, which is about 5.88 trillion miles.
How big is a lightyear?
A lightyear is a unit of distance and is equivalent to about 9.46 trillion kilometers (5.88 trillion miles). It is the distance that light travels in a vacuum in one year.
Miles in a lightyear?
A lot. 5,878,625,373,184 or around 6 trillion miles to a light year.
How many acres in a square lightyear?
22,116,326,410,348,823,000,000,000,000. That's 22 octillion. I took the exact number of miles in a light-year (5,878,499,810,000), squared it to get square miles, and multiplied by 640 for acres per sq mile.
How many millimeters are in a lightyear?
There are approximately 9.46 trillion kilometers in a lightyear. To convert this to millimeters, 1 kilometer is equal to 1,000,000 millimeters. Therefore, there are about 9.46 x 10^18 millimeters in a lightyear.
