WHICH IS OLDER THE EARTH OR THE SUN

WHICH IS OLDER - THE EARTH OR THE SUN?

There are many theories about the origin of the solar sys­tem. For the past twenty-five years the new theory leans toward saying:

The planets originated about the same time that the sun formed. The older concept about the solar system, namely, that the planets are younger than the Sun, introduced many ideas difficult to explain. Newer theories say, in brief, that the solar system originated in nebula - a huge cloud of gas, mostly hydrogen and cosmic dust. The cloud became den­ser by condensation, with the future sun at the-center and various miniature condensations eventually to become plan­ets.

The large future sun became a true star, and the minor condensations, ultimately losing heat, became cold planets.

The outer planet in our solar system that has not known satellite is Pluto. No satellites of Pluto have been discov­ered. Uranus has five satellites and Neptune two. Kuiper discovered the fifth satellite of Uranus in 1948 and the sec­ond of Neptune. Among the four inner planets, neither Mer­cury nor Venus has a satellite. Mars has two and the Earth only one - the Moon.

One form of motion of the Earth affects the seasons over a span of about 13,000 years. The word involved in describ­ing this motion is precession. As the Earth spins on its axis, the north pole points to a certain star, but like a spinning top, the earth wobbles. It takes 26,000 years to complete one wobble that is, the axis executes a circle about a vertical line while the tilt of the axis is still maintained at 231/2 degrees.

During the precession - sometimes referred to as the precession of the equinoxes - the axis gradually points to different stars. In one half of a precession, (3000 years) in that part of the Earth's orbit where we now have winter we shall then have summer.

Most of planets orbiting around the Sun lie in a plane close to that which the Earth follows - the ecliptic plane. One planet however, is way out in its inclination to the eclip­tic plane. That planet is Pluto.

Pluto is inclined 17 degrees to the plane of the ecliptic, and Mercury is inclined seven degrees. But all other plan­ets vary between less than one degree and about three de­grees in following the same plane of orbit the Earth does.

The more elliptical the path of the orbit of a planet be­comes, the greater the eccentricity of the orbit. The inner planet that has the lowest eccentricity, the closest approach to a circular orbit is Venus.

The orbit of Venus is almost circular. Its eccentricity is only .007 in contrast to the Earth's .017 eccentricity. Mercury's orbit is very elliptical with an eccentricity of .021 exceeded only by Pluto with .0249 - the highest among all the planets.

According to some modern theories, the Sun may last for ten thousand million years or longer. During this long time interval the Sun will get hotter. On our time scale of life, we shall not notice any increase. But near the end of time for the Sun, the increase in the intensity of radiation may scorch the Earth and boil the ocean away. It then may take a few million years for the atomic fires to die out.

Eclipses of the Sun and Moon are rare even though you might expect the possibility of one each a month. The line up of the Moon, Earth and Sun is infrequent because the Moon's

orbit plane about the Earth is tilted about 5 degrees to that of the ecliptic plane of the Earth's orbit. In one year there are more solar than lunar eclipses. There can be no more than seven total eclipses a year. Sometimes we do not get a full quota.

Whenever there are five solar eclipses in one year, there is a minimum of two lunar eclipses. If a lunar eclipse occurs, everyone on the Earth sees it, but when a solar eclipse occurs, the shadow cast by the Moon falls across the Earth's sur­face in narrow belts so that few see the phenomena.

Early in 1979 one planet will trade places with4 another planet in order of its distance from the Sun. The exchange will last about twenty years. The planet which will be su­perseded temporarily in this exchange is Neptune. Neptune is the eighth planet in the distance from the Sun.

Because of its great eccentricity, Pluto at its nearest approach to the Sun will be inside of Neptune's orbit by more than 60 million miles. Thus for this twenty year period Pluto will be planet number eight, and Neptune, number nine. There will be no danger of collision when the exchange occurs since Pluto is inclined about 15 degrees to the orbit plane of Neptune.

The average distance of the planet Neptune from the Sun is thirty times the distance of the Earth from the Sun. The intensity of the Sun's radiation on Neptune compared to the Sun's radiation on the earth is 1/900th as great.

Of the nine planets, the one which may have been a sat­ellite of another planet before it became independent is Pluto. All the planets beyond Mars except Pluto rotate at a rapid rate, varying from about 10 to 16 hours.

In 1956 Kuiper calculated the period of rotation of Pluto to be 6.23 days. This longer period is probably due to the fact that Pluto was once a satellite of Neptune and retained its rotation when it became an independent planet.

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