Question

Why are light-years more convenient than miles, kilometers, or astronomical units (AU) for measuring the distances to stars and galaxies? (Select all that apply.)

A. because in viewing a distant galaxy, the distance in light-years to the galaxy tells us how far back in time we are viewing the galaxy because light-years are the units astronomers have been using since the beginning of modern astronomy and are used only to be consistent with historical convention
B.because distances between objects in the universe are very large compared to the distances between objects on Earth and in our solar system,
C. measuring distances between objects in the universe in miles, kilometers, or astronomical units would require using very large numbers
D. because only light-years can provide an accurate measurement of how far light travels across the universe

Answer 1

Light-years are used to measure cosmic distances due to the impracticality of using smaller units like kilometers or miles for the vast distances involved, and because they reflect both distance and 'look-back' time.

Step-by-step explanation:

Light-years are more convenient than miles, kilometers, or astronomical units (AU) for measuring the distances to stars and galaxies because of several important reasons.

• Distances between objects in the universe are very large compared to those on Earth and the solar system, making light-years a more practical unit.
• Using miles or kilometers would involve extremely large numbers that are cumbersome to work with.
• Because light travels at a constant speed, measuring in light-years allows us to understand the distance in terms of the time it takes for light to travel, connecting distance with the 'look-back' time in the universe.

Indeed, when we talk about distances in light-years, we're also considering how far back in time we are looking. For instance, the Andromeda galaxy, being 2 million light-years away, means we are seeing light that left it 2 million years in the past.

Answer 2

a,b,c

Step-by-step explanation:

The light years is the length units that by now we use to measure the distances in universe. They are the biggest from the ones that were mention.

A light year is equivalent to 9.46 trillion km. An astronomic unit is equivalent to 150 million kilometers.

Also for practice is better to use light years than mention a distance in million or trillions of km from the Earth or another point in the universe.

Another use of the light years is that we an imagine the time (and the distance) that take to observe a universal body from its place to the Earth, like another star, planet, galaxy, etc.