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# From the Earth to the Sun

Updated on February 28, 2013

## By Joan Whetzel

The world's space programs continually change and evolve as technology . With those changes and the frequent updates in technology and scientific knowledge, the appeal of exploring space becomes more captivating. What better place to begin our fascination with space than with our own solar system - starting with the distance between the Earth and the Sun, how fast light travels in space, and how long it would take us to travel to the sun.

What Is a Light Year?

A light year (ly) is the distance that light travels in a vacuum in one Earth year according to the Julian calendar, which is approximately 5.88 trillion miles or 9.45 trillion kilometers. The light year (ly) measurement is used to calculate galactic and interstellar distances, at least for publications read by the general public. The scientific and astronomical communities prefer the term parsec (3.26 ly) a measurement that can be more easily obtained from and compared with data acquired through observation. These larger measurements are more practical for computing the larger distances like the distance from our Sun to the nearest galaxy known as the Andromeda Galaxy. That distance would measure 21,000,000,000,000,000,000 km or 13048794989999998976 miles. That's the equivalent of 2,219701751e-12 light years or 6,805636508e-13 parsecs - both of these are much easier measurements with which to work.

Light Years Compared to Other Measurements

Use this table to convert between the different measurements - miles, kilometers, light years, parsecs, and astronomical units. Some of the measurements are listed with a negative or positive number at the end. The negative number means 'to the negative power" and the positive number stands for "to the positive power." If the number were to be written out completely, the positive or negative number indicates how many spaces the decimal point will move in either direction. So, for example, for a number ending in +12, the decimal point moves to the right by 12 spaces, making it a larger number. A number ending in a -9, for instance, would mean that the decimal point moves 9 spaces to the left, creating a much smaller number.

The figures in the above table convert to and from a light year based on the Julian calendar year of 365.25 days. Using these measurements, then, the speed of light can be defined as the speed that light travels in one year which equates to 299,792,458 miles per second (482,469,195 km). Also using the measurements in the above table, the average distance between the Earth and Sun can be calculated as approximately 1 Astronomical Unit (a. u.) which equals 92,955,621.3558 miles, 149,597,870.691 kilometers, 5.593407935e-27 light years , or 0.00000484813678172 parsecs. The mile and kilometer measurements seem really huge in comparison to those microscopically small decimals of the light year and parsec measurements.

Light year and light month measurements are usually reserved for objects within the solar system or between nearby stars in the same globular cluster or in the same spiral arm of any given galaxy. A kilo-light-year (approximately the equivalent of 307 parsecs) is the measurement used for measuring between neighboring galaxies or clusters of galaxies. Giga-light-years (about 307 mega-parsecs) measure the distance to super-galaxies or quasars. So with these measurements, the Crab Supernova is approximately 4,000 light years away from our solar system and the Andromeda Galaxy is about 2.3 million light years away. Our own Milky Way Galaxy measures approximately 150,000 light years across.

How Long Would it Take to Fly from the Earth to the Sun?

If we could travel from the Earth to the Sun at the speed of light it would only take us about 8 minutes. However, we don't have the technology to do that, so let's calculate how long it would take using our current technology. Travelling in a fast airplane (like a military jet) at top speed (1500 mph, 2414 kph) it would take about 61, 973 hours, or about 2,582 days. That comes to about 7 years and 27 days. Driving a car at about 60 mph (96.5 kph), it would take about 177 years.

Resources

American Heritage Dictionary. Leap Year.

http://education.yahoo.com/reference/dictionary/entry/light-year

Wikipedia. Light-Year.

NASA. What Is a Light Year and How Is it Used?

Wiki Answers. If it Was Possible to Fly a Modern Jet Plane to the Sun How Long Would it Take to Get There?

Wiki Answers. What is the travel time from earth to sun?

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• Author

Joan Whetzel 5 years ago from Katy, Texas

I used to think it was a made up word too, but it turns out it's a real measurement. Thanks fo reading.

• Russ Moran - The Write Stuff 5 years ago from Long Island, New York

I love quantitative comparisons. It makes science sing. I always thought a parsec was made up for Harrison Ford's role in Star Wars: "She'll do the Kessel run in three parsecs."

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