|In astronomy, the parabola features in both the construction of
telescopes and in the motion of comets around the Sun. A
parabola is one of the four conic sections - a plane
intersecting a cone parallel to one edge traces out a
parabola.|| |A parabola has the functional form:| |y = A x2|
|where A is the constant of proportionality.| Parabolas in
Telescope Design ||The parabola is the exact shape required to
focus a plane wave to a single point. Hence parabolic dishes
coherently (i.e. in phase) add electromagnetic radiation at a
point and are central to many telescope designs in both the
optical and radio.| For a parabola of equation y = A x2, the
point of focus lies at ( x = 0, y = A/4). Parabolas in Nature
Curiously a comet falling from a great distance towards the Sun
will trace out a parabolic orbit with the Sun at the focus of
the parabola. This is just a consequence of Newton's laws of
motion and gravitation. Similarly a projectile on Earth follows
a parabolic arc as it falls under gravity.