To call our universe, Big, would be an understatement. The Earth itself, where humans evolved, invented tools, developed science, built telescopes… is nothing, absolutely nothing compared to the colossal scale of the universe. It is apparent that universe cannot be comprehended in terms of our usual idea of distance. Hence, Astronomers understand the universe in terms of – Light.
According to the fundamental laws of physics, nothing travels faster than light. Our Sun is 150 million kilometers away from the Earth and it takes light to travel 8 minutes between us. That is Sun is 8 light minutes away from us. Proxima Centauri is the next nearest star to earth other than Sun, and it takes light, 4 years to traverse the distance. Hence, Proxima Centauri is four light years away and we observe that Star as it was four years earlier. Our Galaxy, the Milky Way is one big city comprising millions of such stars. It takes Light approximately 100,000 light years to traverse across the galaxy. Beyond this Galaxy lies more galaxies, the most distant of which are so far away that the light arriving from them on Earth today set out from the galaxies billions of years ago. So we see them not as they are today, but as they looked long before there was any life on Earth.
Scientists have deduced that our ever expanding universe might be 13.8 billion years old. With the latest technology, astronomers were able to observe the light that originated just after the big bang. Probably first images of our universe before Stars and Galaxies were formed. We can observe universe 13.8 billion years back in whichever direction we turn our telescope, putting earth inside a sphere with radius of 13.8 billion light-years and earth being at the center of observable universe.
That doesn’t mean, edge of universe is 13.8 billion light years away. Notice, I stressed on the word Observable. Light from Big Bang took that much time to reach us, in between Universe is constantly expanding also. When that particular photon emitted from the source 13.8 billion light years away was traveling to reach us, universe kept on expanding and the source itself might have moved further. Astronomers estimate, present distance between us and that source of light could be 46 billion light years.
Actually, we have still not understood how Big this universe is, if it has any limit or if its infinite… But we have a fair idea of how big our Observable Universe is.
Following video created by The American Museum of Natural History, takes you from the Himalayas, through the solar system, across the Milky Way and all the way out to the furthest point of the universe we’re currently able to see.
Ponder over your insignificance.