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Simply put: The distances are too great to measure in standard Earth units. Imagine measuring the length of a flight from London to Singapore in widths of sand instead of k…ilometers or miles. Astronomers use light years (ly) to measure distances in space because space is simply so large. Light travels very fast, so it can easily be used to measure distances without resorting to large scientific notation numbers. Inside the solar system, they use the astronomical unit (AU). It is the distance from the Earth to the sun. For example, 1 AU = 149,598,000 kilometers = 92,955,887.6 miles 1 ly = 9.4605284 × 1012 kilometers = 5.87849981 × 1012 miles
It depends on the distance they are measuring. For things very very close in space they use kilometers. For things a bit farther away, like planets, they use Astronomical un…its (au). For things way out there, like stars, they use light-years.
Because the inch, foot, meter, kilometer, and mile are all too small, and the light year is too big. All of those produce inconvenient numbers when used to measure dista…nces in the solar system. Mercury's average distance from the sun is: 36,000,000 miles 57,900,000 kilometers, 0.000006124 light year 0.387 AU. Pluto's average distance from the sun is: 3,670,000,000 miles 5,910,000,000 kilometers 0.0006247 light year 39.46 AU.
Any standard unit of length will do, but really it just depends where you live. In the U.S. miles are typically used, in which case the distance is roughly 240 million miles. …In most other countries and the scientific community the metric system is preferred, giving us about 384 million kilometers.
An Astronomical Unit is the Average distance the Earth is from the sun
The most common is the light year, which is the distance that a beam of light will travel in one year, and is approximately 10 trillion kilometres (or about 6 trillion miles).… Another unit of inter-stellar measurement is the parsec. One parsec is equal to about 3.26 light years (31 trillion kilometres, or 19 trillion miles).
We can calculate the distance between two starts by using "parallax". The method parallax means triangulating the distance using geometry. Using basic geometry you can relate …the two stars with the angles they make. Think of it as a triangle. If you know the distance between two points in a triangle and the angle betwee those two points, you can calculate the distance for all three segments.
Light years It sounds like a unit of time but it is actually a unit of distance. It is the distance light travels in one year.
For the same reason that the odometer in your car measures distances in miles ... we choose a unit that gives reasonable numbers for the distances we're measuring. It's mu…ch easier to remember that you drive 6.2 miles to work, than it is to remember that your job is 392,832 inches from home. It's much easier to remember that Pluto's average orbital radius is about 39.2 AU, than to remember that Pluto averages about 3,647,240,000 miles from the sun. And once you turn your attention out and away from the solar system, it'll be a lot more convenient to talk about the nearest star at 4.4 light years distant, than to try and remember that Proxima Centauri is about 63,211.8 AU away, or 25,866,280,000,000 miles.
An Astronomical Unit (AU) is a unit of measurement equal to 149.6 million kilometers, the mean distance from the center of the earth to the center of the sun.
Astronomical units for closer objects in our solar system, such as other planets, comets and such like and light year for other stars and galaxies which are much, much further… away. It's like comparing the distance of objects in your room using meters and the distance to a city several miles away. For the same reason you use inches, not miles, to describe the length of your shoe, and miles, not feet, to describe the distance from your house to the library. Technically, you can use any old unit of length you want, to describe any length or distance. But it only makes sense to pick the unit that will produce a convenient number for the length or distance you're trying to describe. That way, you wind up with a number that's a lot easier to writer, to remember, and to tell other people about. For example, if you're talking about the wavelength of red light, you could say that it's 0.000000000236 mile, and you'd be perfectly correct. But nobody would remember that after you told them about it, and you'd be much better off telling them that it's 380 nanometers. If you're talking about the distance to the moon, you could say that it's around 15,080,000,000,000 millimeters. You'd be perfectly correct, but again, if you walked up to anybody and told them about it, their eyes would glaze over and they'd forget it as soon as they heard it. It would be much more convenient for you and everrybody else if you said the moon is 238,000 miles away, or even 0.0026 AU. And if we're talking about the distance from me to the nearest star past the sun, how would you feel if I told you that it's 15,707,000,000,000 kilometers ? Most likely not as comfortable as if I told you that it's 4.3 light-years, although they're both correct. It's all a matter of picking the unit that gives you the most convenient number. That way, you give yourself a break, and make it a lot easier to remember the number, write it down in your notebook, and tell other people about it. Which is a big part of exactly what Astronomers must always do.
Parallax is the method that astronomers use to measure the distance from the sun to the earth.
On the surface of the Earth, miles used to be the traditional measure, but now displaced by the SI system with kilometres. An exception is in aviation, where horizontal distan…ces are still measured in miles, and altitude measured in thousands of feet. This is to avoid confusing numbers between these two dimensions. There will still be many ships which measure speed in knots, and distance in nautical miles.
Usually light-years, or parsecs.
They use light years, the distance light can travel in 1 year. It's equivalent to 5878499810000 miles.