Oral route. Many drugs can be administered orally as liquids, capsules, tablets, or chewable tablets. Because the oral route is the most convenient and usually the safest and least expensive, it is the one most often used. However, it has limitations because of the way a drug typically moves through the digestive tract.
Measuring Distances to Stars. Astronomers use several techniques for discovering how far away an object is. The first is called trigonometric parallax and is based on geometry, but it is only good for up to about 500 light-years.
That distance - the length from the Earth's center to the Sun's center - is known as an astronomical unit or AU. One AU is one trip from the center of the Earth to the center of the Sun. Astronomers took (and still take) advantage of this distance to help them measure how far away stars are from the Earth.