Earth is the only planet in the solar system whose name does not derive from gods or goddesses names.
2. Centre of the Universe
Due to the apparent movements of the Sun and the planets in relation to our viewpoint, ancient civilizations believed in the Ptolemaic system, a description of the cosmos where Earth is at the orbital center of all celestial bodies. It was not until the time of Copernicus (sixteenth century) that it was understood that the Earth is just another planet rotating around the sun in circular paths (Copernican heliocentrism).
3. Natural Satellite
The Moon is the largest natural satellite relative to the size of the object it orbits. However, in real terms, it is only the fifth largest natural satellite. The Moon is in synchronous rotation with Earth, always showing the same face. Our satellite is the only celestial body, other than Earth, on which humans have currently been.
The tides on Earth are mostly generated by the Moon’s gravitational pull from one side of Earth to the other. The gravitational attraction of the Sun on Earth’s oceans is almost half that of the Moon, and their gravitational interplay is responsible for spring and neap tides.
5. Gradually Slowing
Earth is gradually slowing down at approximately 17 milliseconds per hundred years, although the rate at which it occurs is not perfectly uniform. Every few years, an extra second is added to make up for lost time. This has the effect of slowly lengthening our days, in approximately 140 million years the length of a day will have increased to 25 hours.
6. Leap Second
While the Earth’s rotation is slowing, that is not the reason why the extra “Leap Second” is added. The reason for adding a leap second is that the planet does not rotate exactly once every 24 hours or 86400 seconds. The rotation actually takes 86400.002 seconds, so each day have a little difference to ours atomic clock’s. The most recent leap second happened on June 30, 2012 at 23:59:60.
7. Greatest Density
The Earth is the densest major body in the solar system (5.52 g/cm³). Followed by Mercury (5.42g/cm³) and Venus (5.26g/cm³).
8. Magnetic Field
Earth’s magnetic field is believed to be generated deep down in our planet’s outer core, caused by convection of liquid metals, coupled with Earth’s rapid rotation. This field protects the Earth from the effects of solar wind.
9. Solar Wind
The magnetic field serves to deflect most of the solar wind, whose charged particles would otherwise strip away the ozone layer that protects the Earth from harmful ultraviolet radiation.
10. Magnetic Pole
Early European navigators believed that compass needles were attracted to a “magnetic mountain” or “magnetic island” somewhere in the far north. The North Magnetic Pole wanders sufficiently slowly to keep ordinary compasses useful for navigation, but at random intervals, averaging around several hundred thousand years, the Earth’s field reverses and the North and South Magnetic Poles switch places.
It was not until the twentieth century that we had maps of our entire planet. Pictures taken from space have a huge importance in our life, for example, they are an enormous help in weather prediction.
The Earth is divided into several layers which have distinct chemical and seismic properties (depths in km):
1) 0 – 35: Crust (locally varies between 5 and 70 km)
2) 35 – 660: Upper mesosphere (upper mantle)
3) 660 – 2809: Lower mesosphere (lower mantle)
4) 2890 – 5150: Outer core
5) 5150 – 6378: Inner core
13. Inner Core
Earth’s inner core is Earth’s innermost part, it is believed to consist primarily of an iron–nickel alloy and to be approximately the same temperature as the surface of the Sun. Earth was discovered to have a solid inner core distinct from its liquid outer core in 1936, by the seismologist Inge Lehmann. Recent speculation suggests that the innermost part of the core is enriched in gold, platinum and other siderophile elements, that if extracted and poured onto the Earth’s surface it would cover the entire Earth with a coating 0.45 m deep.
14. Outer Core
Earth’s outer core is a liquid layer composed of iron and nickel that lies above Earth’s solid inner core and below its mantle. Convection of liquid metals in the outer core creates the Earth’s magnetic field.
Earth’s mantle constitutes about 84% of Earth’s volume, is the thickest layer of Earth with 2900 km. The mantle is composed of silicate rocks that are rich in iron and magnesium. Convection of the mantle is expressed at the surface through the motions of tectonic plates. In some places under the ocean the mantle is exposed on the surface of Earth.
The crust is the outermost solid shell of Earth’s. Is composed of a great variety of igneous, metamorphic, and sedimentary rocks. The temperature of the crust increases with depth, reaching values of 400 °C at the boundary with the underlying mantle.
17. Geologically Active
Earth is the only planet known to be with active plate tectonics in the Solar System. Earthquakes, volcanic activity, mountain-building, and oceanic trench formation occur along these plate boundaries forming Earth’s landscape.
18. Plate Tectonics
Plate tectonics is a scientific theory that describes the large-scale motion of several separate solid plates which float around independently on top of the hot mantle below. The location where two plates meets is called a plate boundary. Plate boundaries are commonly associated with geological events such as earthquakes and the creation of topographic features such as mountains, volcanoes, mid-ocean ridges, and oceanic trenches.
19. Major Plates
There are (at present) eight major plates:
1) North American Plate – North America, western North Atlantic and Greenland Plate boundaries Earth’s Plate Boundaries delineated by earthquake epicenters
2) South American Plate – South America and western South Atlantic
3) Antarctic Plate – Antarctica and the “Southern Ocean”
4) Eurasian Plate – eastern North Atlantic, Europe and Asia except for India
5) African Plate – Africa, eastern South Atlantic and western Indian Ocean
6) Indian-Australian Plate – India, Australia, New Zealand and most of Indian Ocean
7) Nazca Plate – eastern Pacific Ocean adjacent to South America
8) Pacific Plate – most of the Pacific Ocean (and the southern coast of California!)
Over 70 percent of the Earth’s surface is covered with water. Earth is the only planet in the Solar System with water in its three states of matter: solid, liquid and gas.
Earth’s atmosphere is 78% nitrogen and 21% oxygen, with trace amounts of water vapor, carbon dioxide and other gaseous molecules. The atmospheric pressure on the surface of the Earth averages 101.325 kPa.
22. Orbit Length
The length of time it takes for Earth to orbit the Sun is 365.242375 days. This extra of 0,242375 days a year, which isn’t counted at the end of a year, is balanced with an extra day every four years on 29th February. The next Leap Year will be in 2016.
23. Leap Year
Leap Years are any year that can be evenly divided by 4 (such as 2012, 2016, etc), except if it can be evenly divided by 100, then it isn’t (such as 2100, 2200, etc), except if it can be evenly divided by 400, then it is (such as 2000, 2400).
24. Orbit Shape
Earth’s orbit is not a perfect circle, but is rather an oval-shaped ellipse, like that of the orbits of all the other planets. Earth is a bit closer to the sun in early January and farther away in July, although this variation has a much smaller effect than the heating and cooling caused by the tilt of Earth’s axis.
25. Axial Tilt or Obliquity
Axial tilt is the angle between an object’s rotational axis and the perpendicular to its Orbital plane. Due to the axial tilt of the Earth, which is about 23.4°, the amount of sunlight reaching any given point on the surface varies over the course of the year. This causes seasonal change in climate, with summer in the northern hemisphere occurring when the North Pole is pointing toward the Sun, and winter taking place when the pole is pointed away.
26. Brightest Planet
From a distance, Earth is the brightest planet in the solar system, because sunlight is reflected off the planet’s water.