why life is possible only on earth

Why Life is Possible on the Earth? 1. Presence of essential elements:
The earth has essential elements like carbon, hydrogen, nitrogen and oxygen. These elements combine to form proteins- the building blocks of life. 2. Presence of oxygen: Life cannot survive without oxygen. The Earth has a large amount of oxygen in the air. 3. Presence of water: Water is also essential for life. The Earth has vast reserves of water. Water regulates body temperature and also helps in processes like digestion, excretion, etc. 4. Presence of atmosphere: The atmosphere has a protective layer of ozone gas which saves the Earth from harmful effects of ultraviolet radiation from the sun. 5. Temperature of Earth: The Earthвs distance from the sun gives it the right temperature for the development of life-forms. If there were even a ten percent increase or decrease in the distance from the sun, the Earth would have been a cold or hot desert. 6.

Right amount of mass and gravitational force: The Earth has the right amount of mass. This mass produces strong gravitational force. This force holds the atmosphere intact.  1 A GOOD SEAT 2 TEMPERATURE 3WATER SEA  Answer:   Life as we know it is possible on Earth because of its distance from the sun, allowing water to exist in all three states, and in a cycle. If we were closer to the sun (but not as close as Venus), life may still have evolved, but very differently, likewise if we were a little further away.  I think life- supporting planets are common in the universe, but perhaps the amazing biodiversity we see on earth is rare, a result of randomness and luck which has given us a comfortable climate.  Another reason is that the sun is a medium sized yellow star, stable and long lived. Its estimated that 1 in 20 stars are like our sun.  Other factors to consider would be the tilt of earth.

If it had none, there would be no seasons, and the Earth would be a radically different place. The seasons are what drives our ocean currents, which are essential to marine (and all) life. Perhaps the biodiversity would be diminished, if life evolved at all. The same goes for the existence of the moon. Many scientists believe that this unusually large and close orbiting satellite helps stabilize the Earth's axis or rotation. In other words, its gravitational pull has prevented the earth from wobbling on its axis, causing dramatic climate shifts. The moon is also responsible for the intertidal zones, which are vast and diverse ecosystems. Consider also what the climate would have been like if the earth had been tilted at say,45`,and the implications for life. It would have meant that much larger portions of each hemisphere would be subjected to continuous sun in summer, followed by a long, cold and dark winter.

Perhaps only simple organisms (if any) could have evolved in such an extreme environment.  I should add that not all life is directly dependent on sunlight. The alien-like ecosystems found around "smokers" in the deep ocean rely on keimosynthesis, and it is thought possible(even probable) that this kind of life also exists on Jupiter's moon, Europa.  When life began, the sun's energy output was about 20% lower than today, and has been gradually increasing since then, and it is estimated that within a billion years the solar intensity will have increased by about 50% on today's value. The distance to the sun may not be so ideal then, and the Earth may experience a runaway greenhouse effect, like Venus, extinguishing all life.

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