Why would astronomers be unlikely to use light hours to measure distances outside the solar system?

Answer 1

Very few astronomers and scientists routinely use "light-minutes" or "light-hours" to describe distances within the solar system. AU, "astronomical units", are more commonly used.

The people who DO use light-minutes and light-hours often use it in terms of the communication lag between Earth and space probes within the solar system. So an astronomer would refer to the current (12/1/09) distance from Earth to Saturn as "9.8 AU", while the operator of an instrument on the Cassini spacecraft might call it "81 light-minutes". Because that's how far ahead he has to think to manage an instrument so far away.

Answer 2

Oh, but they do. In most countries outside of the US, kilometers are used as a measurement within the solar system, not miles. The US refuses to give up the bulky English measuring system and adapt the more logical metric system, but this is not the way the rest of the world measures distances.

Outside of the solar system, the distances become so great that we reduce all of the distances from miles or kilometers to light years and parsecs. A light year is the distance a photon of light travels in a year, and it is in trillions of miles or kilometers. This is so vast a distance that we cannot really wrap our minds around it, so we say that the distance a photon of light travels, at the speed of light, is 1 light year. We can handle that mentally.

For example, this time of year Orion is a glorious winter constellation. The bright blue giant star Rigel in the lower right of the constellation (as viewed from Earth) is about 800 light years away. What does this mean, practically? It means that when you look at Rigel tonight, the light that is reaching your eyes left Rigel over 800 years ago. We are looking into the past when we look at the stars, and how far into the past depends on its distance from Earth.

The point is that human minds understand the number 800, but that number converted to hundreds of trillions of miles or kilometers is so vast that we cannot truly conceive of it, which is why light years or parsecs (3.26 LY) are used for measuring distances to stars and other objects outside of our own solar system.

Answer 3

Astronomers are unlikely to use light-hours to measure distance outside or inside the solar system.

The nearest start is light years away and measuring the distance in light hours would suggest a spurious degree of accuracy and result in unnecessarily large numbers.

Within the solar system, astronomers are more likely to use astronomical units (AU) - the mean distance from the earth to the sun - as a unit of measurement.

Answer 4

Astronomers would be unlikely to use light hours to measure distances outside the solar system because it is a very large unit and not precise enough for interstellar distances. Light years, which is the distance light travels in a year, is a more commonly used unit for such vast distances.

Answer 5

It takes years for a ray of light to reach us even from a nearby star such as Toliman.