# Question Corner: Geometry of lines

## Why do two parallel lines appear to meet at an infinite distance?

Kabir H. Biswas

College of Health &Life Sciences

Doha, Qatar

In flat space, two parallel lines never meet, however, they appear to meet at very distances for the same reason due to which objects appear smaller when they are at a distance than when they are closer. In order to understand this, we may consider that the space between the two lines are filled with thin but equal sized objects (another set of infinitely large number of lines) perpendicular to the lines themselves. Now, when we look at the perpendicular lines, the size of those lines decreases due to an increase in the angle of vision. Therefore, one of those lines that is located infinitely farther from the observer will appear to be a point object and this, the distance the between the parallel lines appear to be zero.

## This week’s questions

Why are people with high blood pressure discouraged from doing exercises that involve lifting weights (isotonic)? What is the mechanism by which aerobics, walking and swimming help in reducing blood pressure?

What is the best way to increase battery life - charge them only when they have almost drained or when it drops below a certain percentage?