Just How Ginormous Is the Observable Universe?
Welcome back to an additional cosmic journey where we will be expanding our minds to get a glimpse at some of the universe’s most mind boggling scales. This week we are going to take a journey deep into the enormity of the observable universe- a realm that is so large that when you use your every day understanding of “big”, it feels like a tiny little thing compared to this. Are you ready to see just how big our neighborhood in the cosmos really is? Then let’s start!
The Observable Universe: What Are We Talking About?
The name “observable universe” can be somewhat misleading. It does not indicate the entire universe (which could be endless), but merely the portion of it that we are able to view or, to put it another way, the portion of the universe from which the light has traveled long enough for us to receive the signal since the Big Bang occurred approximately 13.8 billion years prior. Light also travels at a certain speed and therefore we can only visually perceive this light as a type of cosmic photograph coming from an area with both distance and time that our minds cannot possibly grasp.
How big is it, then?
Be prepared for this shocker: The estimated size of the observable universe is about 93 billion light-years. Yes, billion. For example, a light-year is a distance equal to how many kilometers light travels in a year (that would be 9.46 trillion km, or nearly 6 trillion mi) . When we multiply that by 93 billion, we have an expansion so enormous that it’s almost impossible to get your head around it.
The reason for the 93 billion and why the observable boundary of the universe is so much larger than 13.8 billion years is due to the expansion of space itself. Distant galaxies are moving away from us at speeds greater than what light can travel through the distance between them, thus expanding the observable boundary of the universe beyond the “age of the universe” times the “speed of light” calculation.
Peering Into the Cosmic Depths
Countless miracles occur within what appears to be an infinite void: billions of galaxies; each galaxy has hundreds of billion stars; nebulas create new suns; and the mysterious dark matter, which is a part of the cosmic web, holds all of it together. Each time you look through a telescope, you find more complexity, and realize how little you know about the universe.
Here’s another thought that I often think about and really makes me wonder: when we view the galaxies we are viewing them as they existed millions or even billions of years ago – because it takes so long for the light from those galaxies to reach us. In one sense, looking deep into the cosmos is looking into the past, and seeing ancient cosmic history.
Learning from the Limitations
We do have limitations to our understanding of the cosmos because there is light that cannot be seen by us from past the distance of what is called the observable horizon; and things such as dark energy continue to cause the expansion of the universe to increase, therefore increasing its speed and ultimately causing even the parts of the observable universe that are currently accessible to us to move away in the future.
Therefore when you think about the observable universe, I would encourage you to remember that the observable universe is just one part of an incredible larger picture of the cosmic landscape. What a great reminder of the immense scale of existence and how little we know about it.
Wrapping Up
Next time you step outside and gaze upon the stars, think about how vast the expanse of space represents — and the incredible distance that light from each of those stars traveled to reach your eyes. The idea is both awe-inspiring and humbling; it offers a connection to the universe that few other experiences can offer.
Thank you for joining me on this cosmic adventure! I encourage you to continue exploring our world and universe through curiosity, and we will take on another amazing subject in the near future – perhaps one closer to home, but equally as amazing. Look up again and ponder the unknowns.