Astronomy and Space articles
by Martin George of the Launceston Planetarium
22 March 2014
Key Big Bang Evidence Found
Earlier this week, the Harvard-Smithsonian Centre for Astrophysics in the USA became
the venue for one of the most significant advances in modern astronomy. It was
announced that astronomers had found key evidence in support of our modern ideas
about the Big Bang, which began the Universe about 13.7 billion years ago.
More specifically, the discovery relates to the part of the Big Bang called inflation, which
was introduced to help explain two significant problems facing the Big Bang Theory.
In a nutshell, the theory states that the Universe began from a tiny point known as a
singularity, which expanded in a tremendously hot 'fireball'. The Universe has been
expanding and cooling ever since.
Key early evidence for the Big Bang was the observation nearly 100 years ago that in
general, the galaxies in the Universe are moving apart from each other. Our
interpretation of this is as an expansion of space itself, rather than the galaxies moving
apart through 'empty' space. Another key piece of evidence was obtained in 1965 with
the announcement of the discovery of the background radiation from the Big Bang,
usually called the cosmic microwave background.
However, there were problems with the idea. Firstly, how could the Universe be similar
everywhere - in particular, at the same temperature? The original idea of the Big Bang
can't explain this, because two widely separated parts of the Universe are moving apart
faster than the speed of light, and have not had time to come into equilibrium with each
other.
The other problem is called the 'flatness' problem: The Universe seems to have just the
right density to expand forever but at a continually decreasing rate. How could this have
worked out so exactly?
In the early 1980s, the idea of inflation took hold. These problems are solved if the
Universe underwent a very rapid period of expansion when it was very young, from being
smaller than the size of a subatomic particle called a proton up to about the size of a
grapefruit. Inflation would have begun when the Universe was about a millionth of a
millionth of a millionth of a millionth of a millionth of a millionth of a second old (that's 10
to the power minus 36 seconds in scientific notation), and lasted until the Universe was
about a thousand times older - but still an unimaginably tiny fraction of a second old.
Inflation solved the problems because it would have 'held' the features of the Universe
together during the expansion to grapefruit size, resulting in the overall similarities
between different parts of the Universe. It also explains the flatness problem - in a sense,
Astronomy and Space articles
by Martin George of the Launceston Planetarium
22 March 2014
ironing out the wrinkles in the structure. As one author, John Gribbin, has so well put it,
it's like the wrinkly surface of a prune becoming a smooth, flat surface when the prune is
placed in water and swells up.
So, what is this evidence? Scientists using an instrument at the South Pole called
BICEP-2, which stands for Background Imaging of Cosmic Extragalactic Polarization,
have made detailed studies of the cosmic background radiation which show exactly the
kind of polarisation effect that the theory predicts. Gravitational waves during inflation
caused oscillations in spacetime that results in the light waves of the radiation oscillating
preferentially in particular directions; this preferential direction is what polarisation is all
about.
Until now, the polarisation relating to inflation had not been observed. But now because
of this breakthrough, champagne corks will be popping - as this effect, long predicted by
the theory, has been observed.
Just like when Armstrong walked on the Moon, I shall always remember where I was
when I heard the news!
Article by Martin George, Launceston Planetarium, QVMAG.
Reproduced with permission of the Mercury newspaper.