What’s wrong with
the Universe?
For centuries now
mankind has been pretty sure it knew what the Universe was made of – gas, dust,
stars, planets, galaxies, hamburgers – those were considered to be the main
constituents of the cosmos. Some of the dust and gas may have been a little
hard to see, some of the galaxies were so far away that their light was
incredibly faint by the time it reached the Earth, but essentially we knew what
the raw ingredients were (apart from the burgers but who cared, they tasted so
good).
For the last
hundred years or so we have also had a good working model of the way the
Universe came into existence and how it has evolved since – the famous Big Bang
theory (the scientific hypothesis, not the TV show). This says that at some
point in the past (around 15 billion years ago) the entire Universe came into
existence at a point, exploded outwards and has been expanding ever since. This
latter conjecture has been verified experimentally numerous times by measuring
the so-called red shift of other galaxies as they rush away from each other.
The effect is analogous to the way a train whistle or a siren appears to change
in pitch as the vehicle approaches and then recedes from an observer (a
phenomena known to physicists as the Doppler effect).
Sound waves from a moving vehicle distorted by the Doppler effect (Image credit Charly Whisky) |
Of course in much
the same way as a ball thrown directly upwards on Earth will slow down due to
the effect of gravity as it rises higher and higher, it was understood that the
rate of expansion of the Universe would slow down over time. What would happen
once the rate reached zero was unclear, this depended on how much matter the
entire Universe contained. Nonetheless the slowing of the expansion was taken
as given.
Imagine the
surprise of two separate groups of physicists therefore when studies they were
carrying out to determine the distances to a class of exploding star known as
Type 1a supernovae indicated that the rate of this expansion was not slowing
down, in fact the total opposite, it appeared to be speeding up. This would be
like throwing a ball straight up into the air only to see it speed up faster
and faster and fly off into space! Both groups initially doubted their own
findings and it was only when they became aware of the work of the others that
they were able to accept that they had discovered a new phenomenon, rather than
having made some huge experimental error.
A supernova remnant, or possibly a giant cosmic space pizza (Image credit NASA) |
In fact their
findings are now so well accepted by mainstream science that three of the men
have been awarded this years Nobel prize for physics, usually reckoned to be a
good indication that you are on the right track with your work.
In order to explain
this result a mysterious and so far unobserved mechanism was proposed, currently
going by the name of Dark Energy – the name being chosen to indicate that we
don’t really have a clue what this consists of. It is hoped that future
observations by instruments such as the James Webb Space Telescope (due for
launch in 2018) will shed light (literally) on the answer, until then there are
a range of weird and wonderful ideas being bandied about as explanations.
The sum total of human knowledge about exactly what comprises dark energy |
Of course this is
all great news for physicists, the more cynical amongst us may well feel that
‘discovering’ something huge yet invisible is a great way to guarantee future
employment and funding for massive science projects such as the JWST or the
LHC, but of course physicists are far too naïve and innocent to ever cook up
such a scheme – aren’t they?