What is perigee and apogee ?

Answer 1

Perigee, in terms of an orbiting satellite like the Moon, is when the satellite is closest to the planet it orbits, and for the Moon, its perigee distance is 216,500 miles and its apogee distance, the furthest it is from the Earth, is 247,700 miles.....an orbit that is an ellipse. The Moon is gradually moving further away from the Earth.

Answer 2

Readers should be familiar with the terms heliocentrism (Sun at the centre in Copernicus' model) and geocentrism (Earth at the centre in Ptolemy' model) but Paul Braxton (surprisingly for someone with >600 Best Answers) and others are confused between aphelion/perihelion and apogee/perigee: words ending in -helion refer to the sun being orbited by the earth (or, indeed, any planet) and words ending in gee refer to the earth being orbited by the Moon (or, indeed, any satellite).

The moon's orbit around the earth (thirteen times a year) is not a perfect circle but an ellipse. About once a fortnight it is at the furthest point away from the earth it will get on that lunar-month-long journey (apogee) and about a fortnight later it will arrive at the nearest point to the earth it will get on that lunar-month-long journey (perigee).

As can be seen from the table below there are 13 different apogees a year and there are 13 different perigees too, all a bit different in the distances involved.

APOGEE AND PERIGEE IN 2007

Apogee: Jan 10 16:27 404,334 km
Perigee: Jan 22 12:25 366,928 km

Apogee: Feb 7 12:40 404,989 km
Perigee: Feb 19 9:35 361,439 km

Apogee: Mar 7 3:38 405,850 km
Perigee: Mar 19 18:40 357,815 km

Apogee: Apr 3 8:39 406,326 km
Perigee: Apr 17 5:56 357,137 km

Apogee: Apr 30 10:58 406,208 km
Perigee: May 15 15:11 359,392 km

Apogee: May 27 22:02 405,456 km
Perigee: Jun 12 17:08 363,777 km

Apogee: Jun 24 14:26 404,538 km
Perigee: Jul 9 21:39 368,533 km

Apogee: Jul 22 8:44 404,150 km
Perigee: Aug 3 23:53 368,891 km

Apogee: Aug 19 3:29 404,620 km
Perigee: Aug 31 0:14 364,173 km

Apogee: Sep 15 21:07 405,644 km
Perigee: Sep 28 1:54 359,419 km

Apogee: Oct 13 9:54 406,489 km
Perigee: Oct 26 11:52 356,754 km

Apogee: Nov 9 12:33 406,670 km
Perigee: Nov 24 0:13 357,195 km

Apogee: Dec 6 16:55 406,234 km
Perigee: Dec 22 10:12 360,816 km

Answer 3

Orbits that are closed loops all have at least a perigee and an apogee. Since it is possible to derive a formula that links eccentricity to the difference (in distance) between perigee and apogee, then the perfect circle (e = 0) has the same perigee and apogee distance (difference = 0). You cannot distinguish the perigee from the apogee (or, if you prefer, every single point on the orbit is simultaneously a perigee and an apogee). This leaves open orbits: parabolic and hyperbolic. The both have a perigee but no apogee (the distance is boundless). Whatever distance you try to set as that of apogee, you can show that the orbit can go further out. The open orbits definitely do not have an apogee. For the circular orbit, the answer could be ambiguous. The circular orbit does not have a distinct apogee. If the definition of apogee requires you to identify a point as distinct from the perigee, then the circular orbit does not have one. If the definition is simply the furthest point, then the entire orbit is the apogee.

Answer 4

These two words pertain to the orbit of some body around another. For example, a satellite may have an apogee of 500 miles and a perigee of 300 miles. Apogee is that point in an orbit farthest away from the central object while perigee is the closest point. Another example -- in summer Earth is at apogee in its orbit around the sun while in the winter it's at perigee.

Answer 5

Usually for simplification, orbits around planets are just portayed as round. This is just a simplification though, and orbiting objects tend to have a more elliptical path. As such, Perigee is the point on that elliptical path when an object (such as the moon) is closest to the Earth, and Apogee is when the object is at the farthest point of its orbit.
(on edit) @everyone else: Actually, no, that's not generally true. Perigee and Apogee refer SPECIFICALLY to the Earth, the -gee in the words comes from Gaea, the Greek word for Earth. Other terms exist for other bodies, such as Perihelion (for the sun). The general terms when not referring to Earth are "periapsis" and "apoapsis"
http://en.wikipedia.org/wiki/Perigee

Answer 6

It applies to an object in an elliptical orbit around the Earth. Perigee is the closest point of approach to the Earth in the object's orbit, and apogee is the furthest.

Answer 7

Apogee is the part of an orbit that is the furthest from the body around which the object in orbit revolves. The perigee is the point of closest approach.

Answer 8

Perigee is when the moon/satellite is closest to earth in it's elliptical orbit and apogee just the opposite

Answer 9

Perigee is the closest point to another point of an orbiting body, apogee is the farthest.

Answer 10

perigee is the point when the moon is closest to Earth in orbit and apogee is the opposite