Some of us blindly accept things the way they are. We exist. It doesn’t matter why, we just do. But for others, such as astrophysicist Duncan Meacher, accepting things the way they are without knowing why will never be enough. Alongside a bunch of other incredibly smart people at Penn State University’s department of physics, Duncan’s work helps humans to understand the state of our universe, its origins and how the forces within it work. space science earth science universe science
The answers to the universe’s big questions are rarely simple, but attempting to wrap our collective noggins around them can be a life-affirming experience. Those same answers also remind us of our relatively tiny place within the mind-blowingly large cosmos we call home. Here’s what Duncan told us when we asked him 10 of the most difficult space questions we could think of. space science earth science universe science
10. How old is the universe?
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We have arrived at this number through several observations over the past century, the first of which came from Edwin Hubble who was able to determine the apparent speed at which distant galaxies appeared to be moving away from us by measuring the ‘redshifting’ of the light that is given off by them. This is analogous to the effect that makes an ambulance’s siren change pitch as it is moving towards or away from you, with light (or sound) waves being compressed (blueshifted) as the source moves towards you or stretched (redshifted) as it moves away. space science earth science universe science
In fact, the space between the galaxies is expanding which produces a cosmological redshift. By measuring the speed of the apparent recessional velocity of the galaxies, Hubble found that the further a galaxy was away from us, the faster it was moving. From this he was able to determine that all the matter in the universe must have, at one time, been a lot closer together. This is because the universe used to be a lot smaller before expanding to the size that it is today. space science earth science universe science
More recent experiments have been able to put tighter constraints on the age of the universe by measuring the cosmic microwave background (CMB). These experiments measured the background temperature of the universe which is produced from the leftover radiation of the Big Bang. As the universe expanded it cooled down until it reached the temperature that we measure today of 2.7 Kelvin (or minus 270ºC). The observations of core collapse supernova, which are the explosive last dying moments of stars that shine brighter than whole galaxies, allow us to measure the distance to the galaxies they’re within. By combining the results of the nearest and most distant observations, we are able to arrive at the age of the universe.