Bell Review Question1. Name the 8 planets in our solar

system.

2. Name the 4 Jovian and the 4 Terrestrial planets.

The SunEarth’s Primary Source of Energy

The Sun

It has a diameter of about 1,392,684 km, about 109 times that of Earth.

The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields.

Chemically, about 75 % of the Sun's mass consists of hydrogen, while the rest is mostly helium.

Chemically, about 75 % of the Sun's mass consists of hydrogen, while the rest is mostly helium.

Thus generates its energy by nuclear fusion of hydrogen into helium.

Chemically, about 75 % of the Sun's mass consists of hydrogen, while the rest is mostly helium.

Thus generates its energy by nuclear fusion of hydrogen into helium.

Nuclear fusion is the process by which two or more atomic nuclei join together, or "fuse", to form a single nucleus.

The average distance of the Sun from the Earth is approximately 150 million kilometers or 1 AU, (an AU is Astronomical Unit), though the distance varies as the Earth moves from perihelion in January to aphelion in July.

At this average distance, light travels from the Sun to Earth in about 8 minutes and 19 seconds.

The energy of this sunlight supports almost all life on Earth by photosynthesis, and drives Earth's climate and weather.

The Sun is a magnetically active star.

It supports a strong, changing magnetic field that varies year-to-year and reverses direction about every eleven years around solar maximum.

The Sun lies close to the inner rim of the Milky Way Galaxy.

Motion of the barycenter of the Solar System relative to the Sun.

The surface temperature of the sun is about 5,780 K, which is 5,500 °C or about 9900 °F, while at the core it's something on the order of 15 million °C or 27 million °F.

Heating Earth’s Surface and Atmosphere

Radiation is the transfer mechanism by which solar energy reaches our planet.

Shorter wavelengths of radiation are associated with greater energy.

The wavelength of visible light ranges from 0.4 micrometer (violet) to 0.7 micrometer (red).

Approximately 50 percent of the solar energy that strikes the top of the atmosphere reaches Earth’s surface. About 30 percent is reflected back to space. The remaining 20 percent of the energy is absorbed by clouds and the atmosphere’s gases.

Radiation reflected by a surface is called its albedo.

Sample albedos surface Low albedo Typical albedoFresh asphalt 0.04Worn asphalt 0.12Conifer forest 0.15Bare soil 0.17Green grass 0.25Desert sand 0.40New concrete 0.55Ocean Ice 0.5–0.7Fresh snow High albedo 0.80–0.90

Radiant energy that is absorbed heats Earth and eventually is reradiated skyward. Because Earth has a much lower surface temperature than the Sun, its radiation is in the form of long wave infrared radiation.

The atmosphere is heated from the ground up. The general drop in temperature with increased altitude in the troposphere (about 6.5°C/kilometer, a figure called the normal lapse rate) supports this fact.

Through the heating of Earth’s atmosphere by the long wave radiation from the surface and the selective absorption of such radiation; results in what is know as the Greenhouse Effect.

Because of the annual balance that exists between incoming and outgoing radiation, called the heat budget, Earth’s average temperature remains relatively constant.

The radiation balance and thus the temperature of a given place fluctuates with changes in cloud cover, atmospheric composition, and most important, Sun angle and length of daylight.

The End