Why Is Earth the Only Planet With Life

For thousands of years mankind has looked up at the moon and the stars and wondered if there are other habitable zones out there. While our planet system provides ideal human living conditions, no one knows for sure if earth is the only planet with life.

The night sky

Once the sun goes down, many people enjoy gazing at the night sky, sometimes with the aid of a telescope. Depending on whether you live in the city or a rural area, between 2,000 and 6,000 stars are visible to the naked eye. Scientists, astronomers, and private citizens all speculate over the theory that because there are so many stars that are visible from Earth, what about the ones we can’t see and that are outside our planet system? Life might exist on other planets, but we can’t prove it.

A breakdown of space

The size of the universe makes proof difficult to obtain.

  • Our planet system, better known as earth, is part of a solar system that has multiple planets and stars.
  • This solar system is part of a galaxy that contains billions of solar systems.
  • The universe in turn holds billions of galaxies.
  • Scientists today believe that there are several universes.

Add it all up, and there are trillions of stars. Many of them could be similar to earth.

Life on earth

Whether or not there are other life forms in the universe is unknown to scientists. What they do know is that of all the habitable zones, our planet system has ideal living conditions for humans.

  • Temperature. Although the earth’s temperature varies between -58 degrees and 122 degrees, the average temperature has been between 50 and 68 degrees for 3.5 billion years.
  • Gases. Earth’s atmosphere is made up of 21 percent oxygen, 78 percent nitrogen, and 0.03 percent dioxide. This layer of gases allows for a constant temperature. Should oxygen levels drop, there would be no life on earth. Should levels exceed 25 percent, all life would be destroyed by fire.
  • Greenhouse effect. The trees and plants on Earth create this stable temperature by releasing oxygen and water vapor. Vegetation also absorbs heat from the sun and limits the albedo effect.
  • Water. All living things need water to survive. Not only do humans, animals, and flora need drinking water, but the water in earth’s oceans is needed to trap heat from the sun and distribute it around the world. Water is also the metabolizing agent that’s responsible for breaking down nutrients and minerals in all life forms and then converting them into energy.

Life elsewhere

While the human race might not exist outside of Earth’s planetary system, that doesn’t mean that there are no other habitable zones for other life forms. Not only the volume, but the sheer size of a number of stars and planets, are enough to create doubt. Jupiter, for instance, is the largest planet in our solar system and is estimated to be 1,321 times bigger than Earth. Magnetic readings from the Galileo satellite suggest that one of Jupiter’s 17 moons, Europa, might have an ocean of liquid water covered by ice.

When you gaze up at the sky or browse images from space online, it’s hard to imagine that earth is the only planet with life. If it is, then what is the purpose of all the other trillions of stars that exist beyond our planet system?

© 2015 Life123, Inc. All rights reserved. An IAC Company