Twinkle Twinkle Little Star
How I wonder what you are?
All your light from the world so high
Why isn’t it visible in the night sky?
Okay, this was my attempt to poetically state the Olber’s paradox :)
Olber looking at the night sky started wondering, and came up with a reasonable paradox of his times that, considering all the light being continuously received from all the stars of the universe from all the directions in the night sky, the night sky should have been indeed much brighter than broad daylight! But what we see is a dark sky on a new moon night. So where has all the light from all those stars that have been shining for so long gone?
Now this was a paradox given the fact that there are billions of stars shining out there in the sky. But for me an even more bigger paradox is the fact that even today we have some books which give a WRONG answer to this paradox!
One of the textbooks I read some years ago said that the night sky is not glowing with star light because light has a finite speed and the universe is not old enough(?) for the distant star light to reach us!!! Doesnt it mean that sometime in the future when that distant star light reaches us, then the night sky will begin to glow like broad daylight? Totally wrong answer :)
Another astronomy quiz book said that the stars have a finite age and die out before their light can have any impact on the brightness of the night sky! Well, but then stars live for a few billion years atleast and going back in time few billion years ago, all that light would be reaching us now (because light travels with a finite speed) and yet the night sky is not bright enough! :)
The truth is that the night sky is indeed glowing very brightly, except that we are not able to see it :) What we need to realize here is the fact that universe is expanding, and the light as it travels in this expanding universe is getting red shifted, i.e stretched. The farther the light has traveled, the more red shifted it is, and we humans can only see light in the visible region of the electromagnetic spectrum which is between 400 nanometers to 800 nanometers. As the light gets redshifted, it becomes infrared, and then the radio waves, the micro waves, etc. All these rays fill up the entire night sky, of course even the day sky! Ask the hubble telescope and it will tell you that Olber was indeed right and night sky is full of light :)
In fact there is this cosmic microwave background radiation which is present all over the universe, and is the brightness that dates back to the immediate aftermath of bigbang!
As the universe continues to expand, the star light moving around in the universe is also expanding resulting in an increase in its wavelength, and hence the star light shift from high energy ultra violet and x-rays to visibe range and then to low energy radio waves.
It is like having a bus completely packed with passengers, and then expanding the bus to the size of New Delhi and then you see that the distance between the two adjacent passengers is few kilometers! If you had eyes which could see only those passengers who are not more than 10 meters away from their neighbor, then in this expanded bus you wont be able to see any passengers at all!
So to conclude, if we had eyes which could see the entire electromagnetic spectrum, then there would have been no Olber’s paradox because we would be seeing a bright night sky, filled with infra red radiation, radio waves, micro waves etc.
Also, another fact is that in the outer boundaries of the visible universe, (where visible means not just the light we can see, but any form of electromagnetic radiation), the universe is expanding so rapidly that the expansion is faster than the speed of light, and hence we have a cut off boundary there and that light will not be able to reach us, nor will light from our region will be able to cross over into the other side of that superluminal expansion!
Another question that arises now is how to see or know about what is happening in those parts of the universe that are beyond the superluminal boundaries? Since as of now we are stuck with ‘nothing can travel faster than light’ assumption, isnt it true that there are isolated universes being created within our own big bang universe?
Probably we will have to wait till we develop the wormhole technology to create space-time shortcuts to connect to those other sides of our universe. Or probably we can even simply wait for some intelligent life on that other side of the universe to develop this technology and then come over here to meet us, just like I have! Yes, I am from that other side of the universe, and have my wormhole opening currently parked in the Himalayan region, anybody interested to crossover? The password to open that worm hole is, oh sorry, our alien character set is not supported by any browsers here on earth, and hence is not printable ;)
Olber, Olber Yes Papa..
Open your Eyes
Ha Ha Ha!