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In the past few years, we have been hearing a lot about global warming and about how it affects the weather. The future does not seem too bright. However, have you ever taken the time to think about how wonderful our dear Earth is? Have you noticed how unique and perfect it is?

Our planet is really fine tuned to host life. It orbits around the Sun at an average of 150 millions kilometers. This is the perfect distance to keep a viable temperature. Just compare the Earth to the 2 closest planets: Venus and Mars . On Earth, the minimum temperature ever recorded was -88°C, the maximum was 58°C and the mean temperature is 14°C. On Mars, where scientists believe life may have been possible in the past, the minimum temperature ever recorded was -87°C, the maximum was -5°C and the mean temperature is -46°C. On Venus, which orbits only 42 millions kilometers closer to the Sun than Earth, the average temperature is 462°C. As you can see, both Mars and Venus could not currently bear life. Venus is far too hot and its atmosphere is actually filled with toxic gas. Mars is actually close to having a viable temperature but it is a bit too cold. The Earth is therefore at the right distance from Sun: if it was a bit closer, it would be too hot and if it was a bit further, it would be too cold.

Another great thing about our planet is its rotation speed: it rotates every 24 hours (actually 23 hours, 56 minutes, 4.091 seconds). Just think about how life would be if it was rotating slower, like some other planets (Venus’ rotation is the slowest lasting 243 days). Nights could last so long that the temperature would drop very low and everything would become an icy desert. Then the Sun would rise and the day would last just as long and it would become incredibly hot. Life with such a climate may not be exactly impossible but it would sure be hard. Also the human body needs rest every night and if days and nights were longer I don’t think it could bear with sleeping only at night.

Surrounding our planet is the atmosphere which is just as perfect. It is composed at 21% of oxygen, which is the exact proportion humans and animals need to breathe. With less oxygen breathing would be harder. More oxygen would be dangerous as breathing an high concentration of oxygen for too long is toxic. Also, the higher concentration of oxygen, the easiest combustion occurs. Therefore, with more oxygen, anything could set on fire much more easily. The carbon dioxide concentration around 1% is also just perfect. A larger concentration would be poisonous to humans and animals. However plants and trees need carbon dioxide to achieve photosynthesis and 1% if just enough for them. Also, high in the atmosphere is the ozone layer that acts as a natural shield against the Sun’s deadly radiations making life on Earth possible. The whole atmosphere also acts as a shield against the thousands of meteoroids that cross Earths’ orbit. Thanks to the atmosphere almost all of them burn completely before reaching the ground. It also prevents the heat from the Sun from simply being reflected on the Earth’s surface and getting lost in space. The gases composing the atmosphere keep a good part of this heat so the temperature does not get too low at night.

The location of our Solar System in the Milky Way and in the Universe is also the best we could hope for. We are located in an external arm of the galaxy where stars are further apart from each other. Therefore, the closest star to Earth apart from the Sun is so far away that it has no gravitational effect on the Sun or the Earth. This allows for all planets in the Solar System to have a very stable orbit around the Sun. This stability could not be achieved closer to the galaxy’s core where stars are closer and gravitational forces are very strong. Also, more stars means more radiation. We are far enough from other stars not to receive any significant amount of radiation from any except the Sun. The Earth has a good shield against this radiation but it would not be as efficient against a larger amount of radiation.

Our Sun is also the best star to hang around. Unlike many other stars, its combustion is very stable and it has a very long life. This means it can provide us with a constant amount of energy for a very long period. And this energy it gives us as heat and light is just the perfect amount. Also, many stars are part of a pair or group of stars orbiting one around the other. This is not the case with our Sun. If it was, no planet could have a stable orbit around the Sun as it would be constantly attracted by other stars.

Our Solar System has 8 planets: 4 inner planets and 4 outer planets, also known as the giant planets. Those giant planets are many times larger than Earth and have a strong gravitational field. If they were closer to Earth, their gravitational field could affect its orbit. However they are orbiting far enough from the Earth to have no bad effect. They are actually quite useful as they act as an outer shield from external celestial bodies they could eventually collide with Earth. Their strong gravitational fields keep most of those bodies from ever reaching the Earth.

Earth’s closest neighbor, the Moon, is not only beautiful at night, but it also has an important effect on life on Earth. Its gravitational field has a key role in tides which are essentials to maintain ocean currents that keep our climate. The Moon’s gravity also acts as a stabilizer on Earth’s axial inclination to keep it at 23.5°. If it wasn’t for the Moon, the axial inclination would vary a lot. Since seasons come from the Earth’s axial inclination, a variable inclination would mean extreme seasons differences and no stability at all.

It really is amazing how everything around us is made so perfectly to allow us to live on this planet. Life is not only possible but it comes with and incredible variety and complexity. Our good old Earth is really a sweet home that we have to take care of.