Capturing 'afterglow' of the Big Bang

Baby pictures are often boring to everyone but for the parents who show them. But if a baby picture of the universe doesn’t inspire your imagination, what can? The European Space Agency recently released the first detailed all-sky images taken from its Planck satellite mission, the latest satellite to probe the ‘afterglow’ of the Big Bang.

This is the radiation coming toward us from all directions from a time when the universe was only 380,000 years old, just after it had cooled sufficiently so that the protons in the hot gas could capture electrons to form neutral hydrogen and the universe then became transparent, and the ambient thermal background of radiation could travel unimpeded to us today.

In the intervening 13.7 billion years or so this radiation has cooled close to 3 degrees above absolute zero and comes in the form of microwaves. In fact for those of us old enough to remember television before cable, when the TV stations went off the air and the screen filled with static, about 1 per cent of the static visible on the screen was due to this radiation from the Big Bang. In spite of this, this signal actually remained hidden until it was accidentally found in 1965 by Robert Wilson and Arno Penzias, who later shared the Nobel Prize for its discovery, which confirmed the Big Bang origin of our universe.

Because this radiation is so cold, it took almost 30 years before a satellite was launched into space by Nasa – to get away from the warm background coming from the Earth and the absorption of radiation in our atmosphere – with a sensitivity great enough to actually image this signal. George Smoot, who along with John Mather was awarded a Nobel Prize for this work, exclaimed that looking at this image was like staring at the ‘face of God.’

This hyperbole can perhaps be forgiven, given the excitement of discovery, but any structure Smoot may have claimed to see was not unlike searches for images of animals in the clouds. The sensitivity of the experiment at the time was barely enough to separate the signal from other random backgrounds in the detector. Another 20 years and now Planck has produced an exquisite picture whose fine-grained detail displays ‘hotspots’ and ‘coldspots’ in this background over the whole sky that represent variations in temperature of less than 1/10,000th of a degree from place to place. These miniscule fluctuations neverthe less reflect small excesses of matter that would later grow due to gravity to form all the structures we observe today – galaxies, stars, planets, and everything they house.

Of more interest is the question of where these lumps of matter and energy came from. We currently have many reasons to think they hearken back to a time much earlier than 380,000 years after the Big Bang, and may have been created a millionth of a billionth of a billionth of a billionth of a second into the history of our universe.
As long as humans have been human, we have been fascinated by cosmic questions. How did the universe begin? Where did we come from? Are we alone? Attempting to answer these questions may not produce a better toaster or a faster airplane, but it is nothing short of remarkable that modern science is revealing facets of our universe that are changing our perspectives on such foundational cosmic questions.

It is too early to assess what new changes will result from the Planck data. When compared with earlier results they seem to suggest a slightly older universe, maybe 13.8 billion years old instead of 13.7 billion years old. And there are intriguing anomalies, as there usually are in data at the edge of our detection abilities. The northern hemisphere of the sky apparently has some larger hotspots and coldspots than the southern hemisphere, and there is one particularly large coldspot in the north that seems out of place.

If history is any guide, most of these anomalies will disappear. It is an unfortunate facet of science reporting that it isn’t often made clear that most anomalies in experiments tend to go away, just as most theoretical ideas turn out to be wrong. Instead of attributing significance to potentially strange results, it is the business of science to try and prove them wrong before we blindly move forward.

I expect we will never achieve answers to all the fundamental questions we may have; each new result breeds new questions, after all. But to live in times such as these, when we are plausibly exploring realms of nature that previously may have been thought to be in the domain of philosophy or theology is for me unbelievably tantalizing.

Looking out at the vast universe, it appears that our own existence in the cosmos may be more capricious and insignificant than we may have thought. But this should not be cause for despair, but rather a source for awe and wonder.