What makes our atmosphere breathable

There are several different regions or layers in Earth's atmosphere. Each has characteristic temperatures, pressures, and phenomena. We live in the troposphere , the lowest layer, where most clouds are found and almost all weather occurs. Some jet aircraft fly in the next higher layer, the stratosphere , which contains the jet streams and the ozone layer. Temperatures reacj their lowest in the mesosphere , because the there are almost no air molecules there to absorb heat energy.

The sky also changes from blue to black in the mesosphere, because there are so few molecules for light to refract off of there. And fartherst from the surface we have the thermosphere , which is the widest layer of the atmosphere and absorbs much of the harmful radiation that reaches Earth from th Sun. The exosphere represents the transition from Earth's atmosphere to space. Earth is not the only world with an atmosphere. All of the planets - and even a few moons - in our solar system have atmospheres.

Some have clouds, wind, rain and powerful storms. If we were to release all the carbon dioxide now trapped in rocks we would increase the atmospheric pressure by 60 times.

The atmospheric blanket of air around the Earth spreads heat and smooths temperature differences. The early atmosphere on Earth allowed life to begin, but once life flourished it began to change the composition of the atmosphere.

Life began as a simple type of bacteria. These cells learned how to harness the energy of the sun to combine the elements carbon, hydrogen and oxygen into the biomolecules that make up their own fabric photosynthesis.

The early organisms got their oxygen from carbon dioxide in the oceans and their hydrogen from water, breaking the H 2 O molecule and releasing oxygen as a by-product into the atmosphere. By one billion years ago the composition of the atmosphere began to resemble what it is today - mostly nitrogen and oxygen and just traces of everything else, including carbon dioxide. William Reville is associate professor of biochemistry and director of microscopy at UCC. Please update your payment details to keep enjoying your Irish Times subscription.

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Don't have an account? The thermosphere is considered part of Earth's atmosphere, but air density is so low that most of this layer is what is normally thought of as outer space. In fact, this is where the space shuttles flew and where the International Space Station orbits Earth. This is also the layer where the auroras occur.

Charged particles from space collide with atoms and molecules in the thermosphere, exciting them into higher states of energy. The atoms shed this excess energy by emitting photons of light, which we see as the colorful aurora borealis and aurora australis. The exosphere , the highest layer, is extremely thin and is where the atmosphere merges into outer space. It is composed of very widely dispersed particles of hydrogen and helium.

Earth is able to support a wide variety of living beings because of its diverse regional climates, which range from extreme cold at the poles to tropical heat at the Equator.

Regional climate is defined by the University Corporation for Atmospheric Research as the average weather in a place over more than 30 years. A region's climate is often described, for example, as sunny, windy, dry, or humid.

These can also describe the weather in a certain place, but while the weather can change in just a few hours, climate changes over a longer span of time. Earth's global climate is an average of regional climates. The global climate has cooled and warmed throughout history. Today, we are seeing unusually rapid warming. The scientific consensus, as stated by the Intergovernmental Panel on Climate Change , is that greenhouse gases, which are increasing because of human activities, are trapping heat in the atmosphere.

To better understand the formation and composition of Earth, scientists sometimes compare our planet with Venus and Mars. All three of these planets are rocky in nature and are part of the inner solar system, meaning that they are in between the sun and the asteroid belt. Venus has an almost fully carbon dioxide atmosphere , with traces of nitrogen and sulfuric acid. The planet, however, also has a runaway greenhouse effect on its surface. Spacecraft have to be heavily reinforced to survive the crushing pressure 90 times heavier than Earth , and the oven-like temperatures Fahrenheit or Celsius , found at its surface.

The clouds are also so thick that the surface is invisible in visible light.