For hundreds of years we humans have been staring off into the vastness of space for varying reasons. Initially man looked at the stars for mythical and spiritual purposes, hoping to derive meaning from what they saw up in the sky that they could then apply to their lives. As time went on we began to discover that the sky could be used as an extraordinarily accurate navigation tool that was used for hundreds of years. Even today celestial navigation is still used by modern technology to guide craft that venture beyond Earth’s atmosphere, a tribute to how useful gazing towards the heavens is.
Perhaps the most interesting part about our constant star gazing is that the more we discover the more we find out we don’t know. The following pie chart shows just how what we can see from Earth makes up a small part of the universe:
In essence the visible universe accounts for a mere 4% of what exists with the remaining 96% being made up primarily of dark matter and dark energy. This idea that the visible universe is so small, even when you consider something like VY Canis Majoris, is something that still amazes me even today.
Consider dark matter, something that we’ve never directly observed. If you take a look around the universe you would begin to notice some strange behaviour that you couldn’t explain if the universe was exactly as we see it. Some of the best examples are effects like gravitational lensing where light coming to us appears to be bent around another object. In the case of a dark matter object we can’t actually see the object doing the bending. Whilst this would traditionally lead to a review of classical physics models (and indeed it has) observational evidence like the bullet cluster are giving strength to the dark matter model of the universe.
Even more curious is the concept of dark energy. As far as we can tell the universe is expanding at an accelerating rate. For this to occur there has to be some form of energy fueling the process and so far it is best explained using dark energy. By its definition dark energy exerts an outward pressure on the universe which is arguably weak, but it is constant throughout the universe. Current models show that previously gravity was overcoming the outward pressure that dark energy was applying to the universe. However as the force that gravity can exert does not increase as the volume of space increases eventually the force of dark energy took over, and caused the acceleration of expansion.
And herein lies the fun of science. We’re constantly finding out how our view of the universe is incomplete and needs to be updated and changed. We’re only really just finding solid data for dark matter (the bullet cluster analysis is barely 3 years old) and dark energy was coined just over a decade ago. One of my most favourite sayings from all my science teachings was :
The most interesting discoveries aren’t usually eureka moments, they’re more along the lines of “That’s not supposed to happen…”
So after millena of gazing up at the stars the biggest mystery about them turns out to be something that we can’t see. Isn’t that just so awesome? It’s like the universe watching us and waiting until we think we have everything figured out and then throwing us a giant curveball.
Maybe I just like it when secrets play hard to get 😉