THE UNIVERSE

The universe is the whole enchilada. Everything that exists, exists in the universe. Before you start getting into the details about things that happen in the universe, try to think about how big it is. Start with you. You are only a couple of feet long. Compare yourself to a whale, or a dinosaur. They are enormous. Then think about how big your city is and how much space you take up in your state, your country, or your continent. Then imagine the Earth. You're not very big now. Hold on it gets worse.

The Earth is pretty small when you compare it to Jupiter. Jupiter is pretty small compared to the Sun. As you go on, there are millions of suns in our galaxy and thousands of galaxies in the universe. No one really knows how many. There are some scientists and mathematicians with theories, but nobody really knows. We have discovered a few things and you can check them out in the related links.

A SOLAR SYSTEM FROM DUST

Our system of one star and eight planets was born about 4.6 billion years ago. All of the pieces were created at the same time. But wait! It wasn't a big "POOF!" and everything was here. It took billions of years for the entire system to develop. All of the gases, dust, and pieces of the system were around at the start. Eventually a star, eight planets, some smaller dwarf planets (like Pluto), and an asteroid belt developed. There wasn't even a star when the Solar System started out.

START WITH A STAR

The system began as a spinning blob of gases. As the blob spun for millions and millions of years, it began to flatten. It probably looked like that shape for a flying saucer. It was a round, flattened disk with a bulge in the middle. That bulge was the beginning of the Sun. Scientists call that "baby" sun a protosun. The last step for the Sun was the magic that ignited it and caused it to shine. Do you remember that dust and gas swirling around that didn't become the Sun? The disk flattened even more and the planets began to develop.

PLANETS FROM THE PIECES

Eight planets developed and now orbit the Sun. As you move away from the Sun, you will first find four planets, then a group of small asteroids, and four large Jovian planets. There are also objects called dwarf planets that include bodies such as Pluto and Charon. In the past few years, astronomers have started to discover smaller objects beyond Pluto in the Kuiper Belt. The distance from the Sun to the Earth is considered "1" (scientists call that distance an astronomical unit).The average distance to Pluto from the Sun is 39.5. The Voyager probes launched decades ago are just now reaching the outer edges of our Solar System. That edge, called the heliopause, is far beyond the orbit of Pluto.

SOLIDS AND GASES

As the planets developed, two types began to emerge. In our system, we have planets that are mainly made of rock and those that are mainly made of gases. The official names are terrestrial (rocklike) and Jovian (those with gases). Of the eight planets in our system, Mercury, Venus, Earth, and Mars are the terrestrial planets. The Jovian planets include Jupiter, Saturn, Uranus, and Neptune. The Jovian planets are all much larger and have a lower density when compared to terrestrial planets. Astronomers have recently decided that there are objects in the Universe that are larger that asteroids and comets, but smaller than real planets. These dwarf planets also orbit the Sun and include Pluto, Charon, and others discovered in the Kuiper Belt. You may also hear the term trans-Neptunian objects used to describe those distant dwarf planets.

THE SUN IN THE MIDDLE

Everything in the Solar System orbits around the Sun. It's mass is greater than all of the other planets combined. Even though the Sun is huge, it is small when compared to other stars in the galaxy. Even though it is smaller, the Sun provides all of the light for the Solar System. As far as astronomers are concerned, our Sun is named Sol. The entire group of Sun and planets is called the Solar System. If another star were named Andros, that system would be named the Androsian System.

THE SUN'S CORE

There is a core to the Sun as there are in planets. Stars are different because most of that central mass is made of tons and tons of hydrogen (H) and helium (He). The hydrogen is constantly involved in the fusion reactions, which produce extreme amounts of energy (light, heat, radio waves). Did you know that our Sun used to be hotter? Astronomers now classify it as a G2 star. It is middle-aged and starting to cool and die. Don't worry. It's going to take millions of years for it to burn out. For example, a G5 star is very old and close to death.

LAYERS OF MATERIALS

The Sun has different layers in its atmosphere, just like the Earth. Don't get excited, you aren't going to be able to breathe on the Sun. The layers of the atmosphere are huge, swirling masses of plasma at extremely high temperatures. Surrounding the core is a radiative level of plasma. Reactions happen in that layer and churn/stir the next layer, the convective layer. Large amounts of interaction occur in the convective layer. It's constantly spinning the way storms spin on Earth. The outer layer of the Sun's atmosphere is the photosphere. When scientists use special telescopes to look at the Sun, this is the layer they can see.

THE SUN'S INFLUENCE

Everything on Earth is affected by the Sun. The Earth's orientation to the Sun creates the seasons of the year. When your hemisphere of Earth is directed away from the Sun, it is winter. When your hemisphere is pointed closer to the Sun, it is summer. So when you're in the Northern Hemisphere and it's summer, kids in Australia might be skiing. As you learn more about the other planets in the Solar System, you will discover that the same idea works for most of them.

The Sun's energy is spread around the planet, but is focused on or near the equator. That centerline of the planet is where you will find long sunny days, very little seasonal change, and the warmest ocean waters. From the equatorial regions, energy moves north and south as it circulates around the planet. That circulation can happen in the atmosphere or the oceans.

Earth

The third planet from the Sun is your home. The Earth is the only known planet where life can survive. As far as we know, there is no other planet in the universe like Earth. We have a very narrow temperature range that allows water to remain a liquid. Life has developed over millions of years because of that liquid. What else makes us special? Most of our atmosphere is made of nitrogen (N), a relatively inert gas. If we had clouds of sulfuric acid or methane (like other planets), life may have never developed.

A SURFACE THAT FLOATS

There are also huge landmasses on our planet. The rock plates that float across the surface are called tectonic plates. Those plates float on the liquid region called the mantle. The mantle is an area between the core and the crust that is filled with molten rock. It is kept in a liquid state because of the energy given off by the center (core) of the Earth. Scientists have also discovered that pressure increases as you move towards the center of the planet. The core of the Earth has extreme temperatures and pressures that keep the iron (Fe) and other metals liquid and flowing.

MAGNETIC FIELD ARMOR

Flowing metal in our planet helps create something called a dynamo effect. Dynamos create large magnetic fields. In the case of the Earth, the magnetic field protects our planet from space. This protective cover is called the magnetosphere. It shields us from the solar winds and solar radiation. You can see where solar winds and the magnetosphere collide when you see the Aurora Borealis (northern hemisphere) and the Aurora Australis (southern hemisphere).

BUILT FOR LIFE

Although many planets in the Solar System have atmospheres, ours protects us from space and encourages life. With an atmosphere made up of 78% nitrogen (N), 21% oxygen (O), and 0.03% carbon dioxide (CO₂), life has thrived on this planet. Our atmosphere has many layers divided by different temperatures and pressures. The atmosphere also provides the planet with protection. The ozone (O₃) that surrounds Earth filters out ultra-violet light. The density (thickness) of the atmosphere helps to vaporize many solid particles colliding with the planet. As you can tell, the atmosphere serves many purposes.