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Why an astronomical unit is not used to measure distance on earth?
Since 1 AU is roughly equal to 149,597,871 Kilometers, (based on the mean distance between the Earth and the Sun) and the farthest distance between Earth and Jupiter is about …928.5 million Kilometers, we can divide to find the answer of 6.2 AU's. The closest distance between Earth and Jupiter is near 629 million Kilometers. Dividing once again gets us an distance of around 4.2 AU's So, the distance between Earth and Jupiter varies from 4.2 to 6.2 AU's!
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.
The average distance from the Earth to the Sun is the definition of "one astronomical unit" (1 AU). The AU is used to give a ready comparison of distances in the solar system,… mostly the orbits of outer planets or comets. It is equal to about 149,597,871 km or 93,955,807.3 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.
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
1,607,000,000 miles --------------------- Around the Vernal Equinox(es) (beginning of Spring) of the following few years (starting from 2010), the distance between Earth… and Uranus will be approx. 20 + 1 = 21 A.U. Around the Autumn Equinox(es) (beginning of Autumn) of the following few years (starting from 2010), the distance between Earth and Uranus will be approx. 20 - 1 = 19 A.U. Around the end of June/beginning of July of the following few years (starting from 2010), the distance between Earth and Uranus will be approximately 20 A.U. Around the middle/end of December of the following few years (starting from 2010), the distance between Earth and Uranus will be approximately 20 A.U.
There are several methods. For example, for nearby stars, the parallax method is used - the star will change its apparent position, between the two extreme positions of the Ea…rth in its orbit (e.g., now, and 6 months later - a distance of 300 million km.). The greater the angle, the nearer the star. For remote stars or galaxies, they measure the intensity and spectrum of lightn to tell how far the star is. If you see some cars on a road during the night, you can tell how far they are based on how bright the lights are. Pretty easy, because all cars have allmost same road lights. But the problem is that if you're looking at stars in the night sky, if a star is at a certain distance from you its brightness can't really be used as a measure of how far away it is because a bigger star will be brighter and because light gets dimmer the farther it is from you a big star can be a lot farther away than a small star and yet they'll both appear exactly the same brightness. How do you solve that one? This kept astronomers guessing for a very long time until about the turn of last century. A woman in contact with Hubble, after whom the Hubble Space Telescope is named, solved the problem. Her name was Henrietta Levitt and she was looking at star charts. She noticed that some star appeared to get bigger and brighter and then dimmer and weaker. They did it with a regular period. These have now become known as the stellar yardsticks. They're called Cepheid variables. They're stars that swell up and shrink down. Because the period at which they do that varies with the size of the star you therefore know, if you look at how often a star like that is blinking on and off, you know how big it is. Therefore you know how bright it is. Because light follows an inverse square law you can work backwards to work out how bright that star must be and therefore how far away it is. Scientists now use these Cepheid variables when they look at a distant star structure they can use the period of any Cepheid variables that are there to work out how far away those particular entities are. That's a stellar yardstick and it was solved by a lady at Harvard a hundred years ago Read more: http://wiki.answers.com/Q/How_astronomer_measure_distances_among_the_stars#ixzz1hqOtSdAZ
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.
Because it's easier to remember 1 AU than 93,000,000 miles (and a lot less typing) Jupiter is 5 AU from the Sun or 780.000.000 kilometers - which is easier to remember? That…'s why!
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 measures 97 million miles (149,598,000 km). Which is the distance Earth's orbit is around the sun. It may be used to measure the distance to objects tha…t are a significant fraction or greater than the distance from the sun to the Earth.
Because it is a large measurement to measure a large distance (there would be immense amoughts of zeros behind a measurement like that given in miles, yet a lightyear is… much too large). It is simply the right unit to measure distances that large.
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).
Why did astronomers use light years as the units of measurement to express the distance of the stars?
Most likely because of the sheer distance between stars in the universe. It would be impractical to put something like 1000 light years into miles (which would be something li…ke 5,800,000,000,000,000 miles)
The average distance from the sun to Earth, our home planet