The unseen universe

The most incomprehensible thing about the world is that it is comprehensible – Albert Einstein

Not so long ago, when I was in school, we were told about the six blind men trying to describe an elephant. Now decades later, learning about the universe as my passion, I have come full circle to the story of the blind men, now exploring the universe.

As astronomers we explore the universe to sight new indications. To do this, we need light in the wavelength ranging from 300 nm to 700 nm (nanometre). This forms a small part of the large band of energy called the electromagnetic waves known to us as light.

Yes! Light is not limited to the seven colours as commonly understood, in fact light is colourless. It is the brain that associates a particular energy stimulus to a colour to differentiate and enjoy the assortment of the world around. The light that most of us say “we see” is called the visible part of the electromagnetic (EM) spectrum or visible light. Meaning,  we do not see light, but the effect of light. Thereby the entire EM spectrum cannot be sensed by us. In some sense we are all blind.

To explore the nature of the EM spectrum one could take both hands close to the ears and cover them without touching them. After a minute of holding one would experience some amount of heat. This is due to the infrared (IR) part of the EM spectrum that is emitted by the body. Almost all bodies on this planet emit IR light.

If this is true, one could see IR light using a thermal camera, where everything would appear hot or cold. Similarly, there are other parts of the EM spectrum that our eyes are not sensitive to, like gamma radiation, X- Rays, UV radiation, micro and radio waves. Meaning, there are many that we have not seen. Hence astronomers build technologically advanced equipment that sense these waves and inform us on the nature of the source emitting them.

For example, white dwarfs predominantly emit X rays, Gamma ray bursts that occurred close to the beginning of the universe and the cold edge of the universe emit in the microwave region and mostly all galaxies emit radio waves.

Do not sway by these examples. They are just 0.000000000000000000000000000001 part of the universe that we think we know.

If the universe is considered to be a sphere of radius 14 bly (billion light years) or 13654000000000000000000 km one can calculate the volume of this sphere using the equation for volume and figure out the size of the universe. Over whelming are the sizes and the nature of things that make the universe. Cosmologists today believe that 90% of the universe does not emit any light and is hence dark. This could actually put us to thinking, have we really seen the universe?

 

– Sriraghavan S M

President, Education & Collaborations

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