Dark Energy

Dark energy is a very strange and unknown form of energy that permeates the universe. It accounts for roughly 70 percent of the known universe. About 25 percent is dark matter, and 5 percent is ordinary matter. This is very peculiar, showing that there is more dark energy in the universe than twice the ammount of dark and ordinary matter. Clearly dark energy dominates the universe, but what is dark energy?

Unfortunatly we aren't quite sure. But we can see it's affects on the universe quite clearly.

In 1929, American astronomer Edwin Powell Hubble was observing how light emmitted from distance galaxies shifted towards the red end of the electromagnetic spectrum as it traveled through space. During this time, he noticed that more distant galaxies were more redshifted than closer ones. From this he theorized that the larger degree of redshift in more distant galaxies was because the universe itself was expanding, stretching the wavelengths of light.

More recent observations of distant galaxies found that these galaxies were flying away from each other at an increasing rate. This shows that the expansion of the universe in accelerating. Before this, it was thought the rate of the expansion of the universe was decreasing due to gravity.

So how is dark energy related to this? It is thought that dark energy is what drives the acceleration of the universe's expantion. This was first suggested by Albert Einstein as a cosmological constant, but he later discarded the idea.

There is still much we don't know about dark energy. The idea that it drives the expansion of the universe is just a theory. But new discoveries are being found quite often, and questions are being answered thanks to those discoveries. But until we have a definite answer, we will have to wait and see.

The concept of "Dark Energy" came to light in 1929 when the great astronomer Edwin Hubble published his amazing discovery about the expansion of the universe where he showed that all the distant galaxies are rushing away from us(through the red shift). At that time scientists excepted this discovery on the basis of the belief that may be this expansion is slowing down. But the main twist of the story was the result of the findings of this expansion rate.

The result was "the expansion rate is not slowing down, rather its getting faster and faster" which was really depressing and that was when the concept of "Dark Energy" started to knock.

The ever accelerating universe was a complete different view from our practical universe because according to this if you throw an apple in the space with such an acceleration may be it won't come back!! (don't worry in our real world it is impossible). So the prime question was what the thing is causing this phenomenon. And the answer came from the very known theory "General Theory of Relativity". According to Einstein if the space is filled with an invisible energy, sort of like a uniform, invisible mist, then the gravity generated by that mist would be repulsive, repulsive gravity.

All these years we knew that the gravity does only one thing 'pulls everything together' and now we have come to know that gravity can also push things apart. This is just what we need to explain our observation. Because this repulsive gravity of an invisible energy in space -- we now call it dark energy which contributes 68.3% of the total energy in the present-day observable universe.