Why do astronomers use a different form of measurement than we are accustomed to using?

Answer 1

Because the distances are so incredibly far that to express them in miles or (god forbid) feet, inches etc would be incomprehensible. It would just be a wall of numbers.

The closest star to our solar system is about 4 and a half light-years. Or roughly 50 trillion miles. To travel on earth as far as it is to get to the nearest star (out of about 300 billion stars in our galaxy alone) you would have to go around the world roughly 2 billion times.

So rather than saying a galaxy is 9,394,000,000,000,000,000,000 miles away, they say it's X number of astronomical units, or X amount of lightyears away.

Answer 2

Due to the (almost incomprehensible) vastness of the observable Universe, science has developed a variety of measures to help us quantify distances between space-borne bodies such as planets and stars.

A common measure is the 'light-year', which is defined as the distance light travels in one year. Another standard measure is an 'astronomical unit' (AU), which is equivalent to the distance between Earth and our Sun (approximately 93 million miles).

These standards relate to distance measurements (how far is a given object from a given point), but astronomers also try to measure mass (weight), brightness, speed, and density, for example.

Answer 3

light years are a much more managable unit once you're talking distances of that scale. a light year is about 9.5X10^15 m. it's so much easier to use light years, especially when you're talking millions and billions of light years! but for calculations we don't use light years, it's just something that's easy to understand and compare.

Answer 4

Some of the units are:

Kelvin to measure the temperatures: of stars and intergalactic space, since that is an absolute scale, and avoids the use of negative values.

Light-year, the distance travelled by light in vacuum (but near enough the same in space) are used for distances because all earthly measures are simply too small. Even with light years, astronomers need to work with thousands and millions.

A solar mass is used as a standard measure for stellar masses.

Some of the units are:

Kelvin to measure the temperatures: of stars and intergalactic space, since that is an absolute scale, and avoids the use of negative values.

Light-year, the distance travelled by light in vacuum (but near enough the same in space) are used for distances because all earthly measures are simply too small. Even with light years, astronomers need to work with thousands and millions.

A solar mass is used as a standard measure for stellar masses.

Some of the units are:

Kelvin to measure the temperatures: of stars and intergalactic space, since that is an absolute scale, and avoids the use of negative values.

Light-year, the distance travelled by light in vacuum (but near enough the same in space) are used for distances because all earthly measures are simply too small. Even with light years, astronomers need to work with thousands and millions.

A solar mass is used as a standard measure for stellar masses.

Some of the units are:

Kelvin to measure the temperatures: of stars and intergalactic space, since that is an absolute scale, and avoids the use of negative values.

Light-year, the distance travelled by light in vacuum (but near enough the same in space) are used for distances because all earthly measures are simply too small. Even with light years, astronomers need to work with thousands and millions.

A solar mass is used as a standard measure for stellar masses.

Answer 5

The whole purpose for choosing one unit instead of another unit is to avoid

running into inconveniently large or small numbers.

That's why the light year was invented. Using miles, the nearest star outside

the solar system is 25,280,000,000,000 miles away, and the present radius of

the observable universe is about 82,301,800,000,000,000,000,000 miles. These

numbers are obviously inconvenient to write down, remember, and tell others

about, so a larger unit was needed. The light year is handy, because just one

of them takes care of 5,878,700,000,000 miles.

Would the light year be a convenient ruler to use for the distances to planets ?

Let's see:

Pluto's orbital distance from the sun averages about 4,557,000,000 miles.

We might be able to use miles, but let's look at a couple of other units before

we choose one.

How about the light-year ? Pluto's orbital distance from the sun averages about

0.000775 light year. That's not too convenient.

How about the Astronomical Unit ? Now Pluto's orbit averages about 49 AU.

Which unit do you think produces the most convenient numbers for distances

within the solar system ?

Answer 6

Because for distances within the solar system , kilometers or miles becomes a very large and unwieldy measure, and AU has the advantage of representing relative distances within the solar system easily, in a way that the other units do not.

Answer 7

Some of the units are:

Kelvin to measure the temperatures: of stars and intergalactic space, since that is an absolute scale, and avoids the use of negative values.

Light-year, the distance travelled by light in vacuum (but near enough the same in space) are used for distances because all earthly measures are simply too small. Even with light years, astronomers need to work with thousands and millions.

A solar mass is used as a standard measure for stellar masses.

Answer 8

Its a convenient scale for measurements between stars.

Answer 9

They measure distance because they want to know. That's what's astronomy is all about: knowing about the Universe.