It's kind of fascinating to look at many of Earth's characteristics and vital information all together in one place. It's even more intriguing to have information about Earth's beginnings, neighborhood, and home galaxy in the same place. And, in a kind of humorous way, it's humbling to get a clearer perspective on where our place is in this universe after all!
Rather than looking at our galaxy and the universe as extensions of Earth, this new ecology.com feature lets us look at our planet a little bit differently, more like Earth as a part of the grand design and evolution of the universe. It's the world we live in, the place we all call home. As you start reading through the information and numerous links, you will have at least a better understanding of what and where "here" is and how we are all connected.
Earth is located in the outer edge of our galaxy, called the Milky Way, about 28,000 light years from the galactic center. It is part of a Solar System that includes eight other known planets, and the only known planet with the ability to sustain life as we know it. The Milky Way is one of billions of spiral galaxies in the universe. (Image: NASA, Galaxy M83, similar size and shape to the Milky Way)
Earth at a Glance: Fast Facts
Age
About 4.54 Billion years
Location
In the Solar System, on the outer edge of the Milky Way, about 28,000 light years from the galactic center (Source: European Space Agency). It takes the solar system 225 million years to make one full trip around the Milky Way.
A medium sized, yellow star. Scientists call it a G2 star. It is the largest object in the solar system and contains 99.8 percent of the solar system's mass. It is located in the center of the solar system.
Distance from the Sun (average)
About 93.1 million miles (also one Astronomical Unit or AU). It is the third planet from the Sun.
Farthest Distance from the Sun:
94.5 million miles.
Closest Distance to the Sun
91.4 million miles.
Speed through Space (around the sun)
18.4 miles per second or about 67,000 miles per hour.
Solar Orbit
It takes Earth 365.2422 days to orbit the sun. This is the basis for the year.
It takes the Earth 23 hours, 56 minutes and four (4) seconds to make one complete 360° rotation.
Rotational Tilt
23.5° on its axis, a straight line through the planet from the North Pole to the South Pole. The tilt is in relation to Earth's near circular orbit around the sun.
One Earth Unit. This measurement is relative to other objects in the universe. Earth's gravity is the force that pulls objects toward the center of the Earth and is measured by the Earth's mass. Gravity is what gives objects their weight. Without gravity, the Earth's spin would fling everything on the planet out into space! See Earth's Weight (Mass), below.
14.7 pounds per square inch at sea level. This is the measure of force exerted on objects by the weight of the air. Many times gravity and atmospheric pressure are considered one and the same thing. Actually, they are not! In fact, it is the Earth's gravitational pull on the atmosphere that gives weight to the atmosphere. The atmospheric pressure decreases above sea level, and it increases below sea level.
Earth's Weight (Mass)
5.972 sextillion (1,000 trillion) metric tons. That's 5,972,000,000,000,000,000,000 tons! Actually, scientists prefer to refer to this measurement as the Earth's mass instead of weight since weight is the result of Earth's gravitational pull on another object. And the Earth cannot pull on itself! As the Earth orbits the Sun, it is weightless. If the Earth were placed on the Sun, it would weigh more than if it were placed on Jupiter, the largest planet in the solar system but much smaller than the sun. Yet, Earth (or any other object for that matter) would have the same mass regardless of where it is located.
Earth's Size, Distances & Surface Features
Equatorial Diameter
7,928 miles
Polar Diameter
7,901 miles
Circumference
24,907 miles
Surface Area
197 million square miles
Surface Data
70.8% covered by water, 29.2 % covered by land
Mt. Everest
Artist's depiction of the Chicxulub impact crater. (NASA)
Highest Point
29,028 feet above sea level, Mount Everest, formed 60 million years ago, located on the border of Tibet and Nepal in the Central Himalayas in southeast Asia.
Lowest Point (on Land)
1,320 feet below sea level, Dead Sea, located on the border between Israel and the West Bank to the west and Jordan to the east. It is so salty -- the saltiest on Earth -- that it is unable to support any type of life.
Deepest Point on Earth
35,802 feet, Challenger Deep, Marinas Trench in the Pacific Ocean. The water pressure there is over eight tons per square inch.
Largest Impact Crater
Chicxulub crater, about 125 miles wide and 7.5 miles deep, buried under several hundred meters of sediment. It is located off of Chicxulub, Mexico, on the northern coast of the Yucatan peninsula. It was created about 65 million years ago by an asteroid that collided with the Earth and subsequently caused the extinction of 70% of the world's species, including the dinosaurs. Only two other such craters in Canada (Sudbury) and South Africa (Vredefort) may be larger.
The Earth's surface and interior are wrapped by its atmosphere. Its atmosphere is made up mostly of nitrogen and oxygen, with dust particles, clouds and microbes (living microscopic organisms) floating throughout. The atmosphere protects the Earth from harmful and lethal radiation and impact from small asteroids and other space matter, as well as it provides conditions essential for human and plant life (air, climate).
The thinnest and coolest layer of the Earth's surface and interior. It is composed of the least dense calcium (Ca) and sodium (Na) aluminum-silicate minerals. The crust is rocky and brittle because it is relatively cold. This makes it particularly fragile during earthquakes. It is from 0-51 miles thick, and is thinnest under the oceans (from 0-6 miles).
The largest of the layers, it is about 1,792 miles thick.. Composed mostly of iron (Fe), magnesium (Mg), aluminum (Al), silicon (Si), and oxygen (O) silicate compounds. It is relatively flexible, unlike the crust, so it flows instead of fracturing.
Consists of two layers - inner (solid) and outer (molten). Mostly iron with some nickel (Ni), the core layers total about 2,166 miles thick. Its temperature is estimated at 5-9,000°F.
So hot that it is molten, with about 10% sulfur, about 1,410 miles thick. It is 98% responsible for producing Earth's magnetic field as it spins around the solid inner core.
78% nitrogen, 21% oxygen, 1% other content (including greenhouse gases). The element Argon makes up about 93% of the other content, with carbon dioxide - the primary greenhouse gas, accounting for a little over 3%. Argon is an odorless and inert (inactive) gas that is commonly used in incandescent and fluorescent light bulbs to protect the filament.
Vital to maintaining Earth's climate and life-sustaining warmth. The Sun's heat is trapped within Earth's atmosphere by the greenhouse gases, mostly carbon dioxide, which enters the atmosphere through the planet's natural carbon cycling and increasingly from human-caused pollution. The increase of carbon dioxide gases in the atmosphere is believed to have caused the Earth's average temperature to rise from 60°F to 61°F in the last few decades.
There is currently no comprehensive catalog of all the know species of plants and animals on this planet. Some scientists estimate about 10 million species of organisms (including humans) live on Earth. Estimates range from as low as two million species to as high as 100 million.
Species classified to date
2.1 million species
Most Unclassified Species
Invertebrates (animals without a backbone), such as insects, worms, sponges, crustaceans, mollusks, spiders, etc.
Total Endangered or Threatened
According to The International Union for Conservation of Nature, a.k.a. The World Conservation Union (IUCN), the number of known threatened species has reached 16,119 (as of their recent study in May 2006). This includes one in three amphibians and a quarter of the world’s coniferous trees, on top of the one in eight birds and one in four mammals known to be in jeopardy. The ranks of those facing extinction are joined by familiar species like the polar bear, hippopotamus and desert gazelles, ocean sharks, freshwater fish and Mediterranean flowers. IUCN documented its findings in its Red List of Threatened Species published in November 2007.
At Left: The U.S. Florida Panther, one of 1,849 species protected under the U.S. Endangered Species Act of 1973. At Right: Amazon Rainforest
Extinct Species
99.9 percent of all Earth's species living at one time or another have become extinct. Without extinctions, we -- humans -- would not be here. There is no known estimate of how many species of living things have become extinct today or since animals first began to appear on Earth in the Cambrian Period, some 600 million years ago. According to the World Resources Institute, 100 species become extinct every day due to tropical deforestation. It is the rainforests that contain more than half of all living things, and there are many species that we never discovered which have succumbed to extinction.
Most Massive Known Extinction
There are five periods of mass extinctions recognized by scientists. The most massive extinction occurred 250 million years ago at the end of the Permian Period when between 75% and 97% of Earth's species are estimated to have died out. Perhaps the most recognized mass extinction occurred 65 million years in the late Cretaceous Period when an asteroid slammed into Earth's surface, resulting in the ultimate loss of 70% of the world species, including the dinosaurs. The current period, called the Holocene, may see the greatest mass destruction of species ever due to anthropogenic or human causes.
Extinction Cycles
Scientists have determined that mass extinctions are a part of Earth evolution of life forms and are indicative of changes taking place within the planet. They estimate that mass extinctions take place about every 26-28 million years. At the same times, existing and new species evolve and replace or add to the current surviving species.
Last Known Extinction
Species are becoming extinct every day.
First Appearance of Animals
Late Proterozoic Era (600-550 million years ago). These were soft-bodied multicellular animals. The first animals with hard parts appear in the Cambrian period from 543 to 488 million years ago.
First Appearance of Plants
Estimated to be about 700 million years ago for land plants and 1.3 Billion years ago for land fungi (Source: Penn State University). Plants originally evolved in the oceans before drifting to land. Before the arrival of plants, Earth was a rocky, barren land mostly covered in ice.
Human Population
6.67 Billion people (estimated), growing at a current rate of about 50 million people per year.
Human Life Expectancy
About 80 years on average for women, 78 years on average for men. Before 1900, few people lived to the age of 70, with an average life expectancy of 47. In prehistoric times, the average life span was about 18.
Oldest Living Single Organism
King's Holly, a 40,000 year old Tasmanian Bush. It is older than the last ice age.
Oldest Living Things
Ancient bacteria (bacillus strain ) found 2,000 feet below the ground in New Mexico, US. They are 250 million years old.
Oldest Multi-Cellular Animals
Sponges. They evolved over 600 million years ago and many different types live today.
Largest Living Animal:
Blue Whale
Largest Living Land Animal
African elephant
Smallest Living Organism
Some scientists consider nanobes to be the smallest living organisms. They are 20-150 billionths of a meter, and are smaller than any known bacteria, spore or other single-celled organism. The smallest of the single-celled animals is the amoeba.
Continental Drift, species extinctions, species evolution, Earth's rotation (slowing), climate changes, global warming, atmospheric changes, solar changes, surface changes (earthquakes, volcanoes), desertification, temperature changes, ice cap recession. Our galaxy is also moving closer to the Andromeda galaxy at a speed of 21 miles per second due to the gravitation force between them. Andromeda is the closest galaxy to Earth, about 2.3 million light years away.
Leading Environmental Issues
Global warming, deforestation (rain forests) and habitat loss, water pollution and potable fresh water, air pollution, energy and energy resources, human population growth, species protection and diversity (plant and animal), land use, food production.
The International Astronomical Union recognizes a total of 11 planets -- eight planets and three dwarf planets. The eight are the first usual planets and the dwarfs are Ceres, Pluto and Eris. NASA, as well as a number of other organizations, still lists the traditional nine planets, including Pluto.
One (1), circles the Earth in about 27 days and eight hours. No known life. All other planets, except for Mercury and Venus, have moons. At least 91 other moons are attached to other planets in the Solar System.
Inner Planets
The inner zone of planets which are comprised mostly of rock and metal.
Mercury: The second smallest planet. Although closest to the sun, it is not the hottest planet.
Venus: Slightly smaller than Earth, and the brightest object in the night sky after the Sun and the Moon. Venus has the hottest sustained temperatures of all the planets due to the high level of carbon dioxide (a greenhouse gas) in its atmosphere.
(Earth): The largest of the inner planets, and the only one capable of sustaining life as we know it.
Mars: Most similar to Earth of all the planets, with polar ice caps, seasons, clouds and fog, but colder. Recently found to have underground water. Still, Mars is unable to sustain life as we know it.
Outer Planets
The gas giants, formed from icy particles and leftover gas.
Jupiter: The largest planet, contains most of the solar system's mass not taken up by the sun.
Saturn: The second largest planet, with its famous rings that stretch over 600 million miles from edge to edge.
Uranus: The third largest planet, the only one of which rotates on its side.
Neptune: Found in 1846, it is the fourth largest of the planets and the outer most of the gas giants.
Pluto. Not a gas giant, reclassified in 2006 as a dwarf planet by the International Astronomical Union (IAU). Pluto is smaller than Earth's moon and is composed of nitrogen ice and rock, and is sometimes closer to the sun than Neptune.
In addition to its 1,286 total listings, the U.S. recognizes 558 non-U.S. species, including 268 mammals, 181 birds, 79 reptiles, 11 fishes, nine amphibians, two clams, four insects, three plants and one snail. The U.S. also has 555 specific approved recovery programs, some of which cover more than one species.
To review the current US Fish & Wildlife Service's Summary of Listed Species by groups, click here…
Did You Know?
Other planets have been discovered orbiting other stars in the Milky Way, the closest being about 42 light-years away. They range in size from Earth-size to several times the mass of our own Jupiter. It is possible that some of these planets may harbor the right elements to support life.
The massive size of Jupiter makes it a kind of body guard for our planet. Its gravitational pull is so enormous because of its size that it will attract objects flying in space away from Earth. However, as our geologic history tells us, Earth is still vulnerable to such impacts. Sixty-five million years ago, a large asteroid or comet crashed into the Earth's surface, resulting in the extinction of about 70% of the world's species.
The largest height variation between the highest mountain and the deepest point in the bottom of the ocean is about 12 miles.
The Solar System has orbited the center of the Milky Way about 20 to 21 times since it formed about 4.5 billion years ago.
Most of Earth's land masses are in the northern hemisphere. There is no particular reason for this, and scientists consider it a coincidence.
The Earth's solid iron inner core, which was discovered by seismological methods in 1936, is estimated at being roughly the size of the moon. It rotates because it is surrounded by a much larger liquid outer core and together the two form a giant electrical motor.
By the year 2025, Earth could lose as many as one fifth of all species known to exist today. In recent centuries, hundreds of species have disappeared, almost always as a result of human activities. The passenger pigeon, one familiar example, was a source of food until excessive hunting and habitat loss caused its extinction in 1914.
Earth's atmosphere has more free oxygen today than it did when Earth formed. While the early atmosphere was mostly carbon dioxide, more than three-quarters of Earth's atmosphere is now nitrogen, and most of the rest of it is oxygen. Chemical reactions locked much of the early carbon dioxide inside rocks, while plants produce the oxygen for our present-day atmosphere.
The Earth's core was formed early in the creation of the planet as heavier molten iron sank toward the center. As the planet cooled, some molten iron began to solidify to create the core which is kept solid by enormous pressure.
Earth's oldest fossils date to roughly 3.5 billion years ago and consist of bacteria microfossils.
The Earth is some 318 times less massive than Jupiter.
Is Earth gaining weight? At the present rate, Earth gains about 40,000 metric tons each year from space debris that bombard our planet. Yet it loses an amount so small (atmospheric gases, etc.) as to not really warrant any serious consideration. So, will Earth's weight gain have an impact on its orbit, relative mass (gravitational pull) or any other properties? Although 40,000 metric tons a year sounds like a huge gain, when you compare it to the immense size of Earth, it dwindles to a meager 0.000003 of one percent of the Earth's mass. The impact is insignificant.
One (1), circles the Earth in about 27 days and eight hours. No known life. All other planets, except for Mercury and Venus, have moons. At least 91 other moons are attached to other planets in the Solar System.
