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.
The nearest star is some 4.2 light years away, and that distance was known to within an accuracy of better than 0.1 light year. For a star measured as 20 light years away, the distance estimate is accurate to within a light year or so. For stars 50 light years away, the margin of error is perhaps 5 to 10 light years. Beyond 100 light years, the parallax is so tiny it cannot be measured accurately, and astronomers resort to more indirect methods to find the distances to the stars.