(written in 2008)
You must have stumbled across news and pictures of newly found planets and galaxies. These news are often substantiated by real pictures taken by telescopes like Hubble. So say if some planet is found to be 100 light years away from earth , then what it implies is that the photos received by the telescope are 100 years older than what the planet actually is at this very moment and we don’t really know about the ‘present’ stage of the planet or galaxy. We are looking at the planet what it was 100 years ago. That celestial body may not even exist now whose images we are getting. Interestingly, what we are actually doing is we are looking into the past of that planet.
What actually happens is that the rays of light which have departed, if you may, from that planet and carry the image of the planet will continue to exist and travel in the universe regardless of the source . If we obstruct the path of those rays , we get those images. Same analogy can certainly be applied to Earth also. It is definitely possible that someone is watching our past right now by receiving the rays emitted by Earth many years back . So if the rays of light emmited from our PAST PLANET bend their way back to earth after travelling long distances , then certainly we will be able to receive them today and look at our own past .
To get a feel of this idea, assume there is a mirror in the universe 5000 light years away from Earth . Now say, light rays from Earth start their journey towards the mirror right now. Essentially, these rays of light carry images about our current planet . These rays would take 5,000 years to reach the mirror and same amount of time to reach back to Earth after being reflected . So after 10,000 years from now , our future generations can view the Earth as it is now in which we are living. It is almost like viewing the past of planet earth by receiving those rays . So in a way our past is running parallel to us at the same natural pace . This method can reveal different phases of earth’s life which is still very mysterious to us . Now the only thing that seems to be little annoying in this whole discussion is the MIRROR. How can we find a mirror in the universe to reflect the light back to us and hence make it possible for us to view our past . Well, the solution to this is the phenomenon of Total Internal Reflection . If the light totally reflects back not by a mirror but by total internal reflection , then the only apparent problem is also solved . And also there is insignificant intensity loss in TIR . Also for Total Internal Reflection, the universe is the best place as there are many atmospheres (of planets ) and vacuum and gases of varying densities all around the universe. Lets view this hypothesis from a different angle . Assume a twin of yours is standing at some distance from you and you are looking at him/her and perceive some image. Now look into a mirror this time , kept at half the distance of your twin , you perceive the same image as the one of your twin . So if we can look at the images of some planet 100 light years away from us , which we are completely potential of doing at present , then we can certainly look at images of our own planet as it was 50 light years back , so there is no point of intensity loss also . There is one more interesting inference which can be derived in this thought-experiment , when you are looking into a mirror you are not looking at the ‘present you’ but you are looking at your past, though it is a very recent one, a few nanoseconds or so , but still it is your PAST.
Hypothetically, assume that light travels at the speed of few entometers per second (10 to the power 30th fraction of the usual speed of light). What would have happened then. When you would have stood in front of the mirror in your old age , then what you’ll see would be your childhood . Now with the present speed of light , assume you are standing in front of a large mirror in the universe at a large distance from you. Then if you stand in front of it when you are old , the same will happen , you will see your past , probably childhood or youth , depending on the distance. This is because the increased cellestial distance have outweighed the speed of light . Another way to put this would be that if at any time you look into that mirror , you will see everything that mirror has witnessed a long time back, and your next generations will see you no matter you exist or not at that time.
Hence, by receiving light from Earth reflected from varying distances ,we can witness different phases of earth . And if somehow we get a closer look at our planet in these images, we can possibly witness the era of dinaussors, the early age , life of christ , and the evolution of earth and human beings on it .