SEEING THE START
And then there was light. That’s pretty much how our universe sprang into existence – as a point that contained everything and continued to expand through to today, building the first stars and galaxies and stretching light years of distance between them. Despite its name, the Big Bang wasn’t some kind of explosion that spat out matter, energy, time and space. It’s imagined like a balloon that continues to stretch, originally holding an incredibly hot and dense primordial soup that cooled and thinned out over millions to billions of years.
Such an event has opened up a whole deluge of questions. And the only way to attempt to look back in time is to lift missions off the ground to seek answers. Several missions have stepped up to the challenge, most notably the Planck mission – which communicated its final signal in October 2013 – under the joint efforts of the ESA and NASA. Planck built upon and improved observations returned by NASA’s Wilkinson Microwave Anisotropy Probe (WMAP), which after a good nine years of service rests in its heliocentric graveyard orbit. Planck’s main aim was to measure the CMB – the afterglow of the Big Bang that’s encoded with how the universe appeared some 400,000 years after the event. To get the best measurements possible, the mission had to be kept at freezing temperatures, with “a passive cooling and three refrigerators taking it to -273.05 degrees Celsius [-460 degree Fahrenheit], which made it the coolest place in the universe,” says the University of Manchester’s Richard Davis, who led the UK’s involvement in one of the instruments on board the craft. “It also had the lowest noise detectors ever made.”
An important feature of the CMB is that it’s by no means smooth. It’s a mess of different temperatures, and it was from soaking up this relic radiation from its orbit around the Sun that Planck was able to pick out even the most subtle blips in temperature – something the mission did incredibly well. “The fluctuations go down to as low as two microkelvin,” Davis tells us. “Planck surpassed its expectations and in some cases even exceeded its goals, so it has been stunning.”
Indeed, a couple of the many achievements that the space mission has in its arsenal are an all-sky survey that has provided us with one of our best views of the oldest light in our universe as well as a better measurement of the age of the cosmos, dated at 13.8 billion years old – 100 million years more than previously thought. And even though the mission has since been deactivated for almost a decade now, Davis assures us that Planck could still wield the key to understanding more about our infant cosmos while its data continues to be investigated for new discoveries.