Why earth tilted

Or e-mail us from our website, www. First of all, let's be sure we're clear on what the earth's axis is. Basically it's an imaginary stick going through the center of the earth, if we define the center as "the point around which it rotates.

Now picture a stick going right through the center of the earth. If the earth weren't tilted, it would rotate like that as it revolved around the sun, and we wouldn't have seasons—only areas that were colder near the poles and warmer near the Equator. But the earth is tilted, and that's why the seasons happen.

When the Northern Hemisphere is pointed toward the sun, it gets more hours of sunlight. Temperatures rise, and you get summer in New York, while it's darker and cooler "down under" in Sydney. Six months later, the reverse is true, and it's the Southern Hemisphere that experiences summer. The degree tilt also explains why changes in daylight during the seasons are very dramatic near the poles which are flooded with sunlight all day long in summer and get virtually no light in mid-winter but barely perceptible near the equator where the sun shines more or less equally throughout the year.

Getting back to why the axis exists, it's mainly the result of the rough-and-tumble environment of the early solar system. We know that the birth of the Sun created a new source of gravity in the young Solar System. The tidal forces between the young sun and the rest of the nebula the Sun was born from created further instability in the gases and dust left in the nebula.

This allowed for the steady formation of the planets. Groundwater is stored under land but, once pumped up for drinking or agriculture, most eventually flows to sea, redistributing its weight around the world. In the past 50 years, humanity has removed 18tn tonnes of water from deep underground reservoirs without it being replaced.

Some scientists argue that the scale of this impact means a new geological epoch — the Anthropocene — needs to be declared. Most scientists think that that rubble, in time, became our Moon. As Earth orbits the Sun, its tilted axis always points in the same direction.

It is summer in June in the Northern Hemisphere because the Sun's rays hit that part of Earth more directly than at any other time of the year. It is winter in December in the Northern Hemisphere, because that is when it is the South Pole's turn to be tilted toward the Sun. And, believe it or not, aphelion when Earth is farthest from the Sun occurs in July, and perihelion when we are closest occurs in January. For those of us who live in the Northern Hemisphere where it's summer in July and winter in January, that seems backwards, doesn't it?

That just goes to prove that Earth's distance from the Sun is not the cause of the seasons.