OCT–DEC 2017 AusTRAlIAN QuARTeRlY 21An Astrophysicist –
Prof Geraint lewis
At the beginning of
time, the universe was
compressed into a single
point and, about 13.8
billion years ago, that
tiny speck of everything
exploded and formed
the universe we live into
today.
According to Dr lewis,
from the university of
Sydney, one of the most significant
things to happen in 2017 is the
unprecedented accuracy that we’ve
been able to measure the Hubble
constant – a value of how fast the
universe is expanding.
“We are now in the age of ‘precision
cosmology’ and this ‘local’ measure
of the expansion of the universe is
significantly different to the global
measurement by Planck,” lewis said.
An international team of scientists
lead by Johns Hopkins university,
Baltimore, found that the universe is
expanding five to nine times faster than
expected and measured it to within a
2.4 percent
accuracy.
The team
made their
conclusions
after
measuring
about 2,400
Cepheid
stars in 19
galaxies and, comparing the observed
brightness of both types of stars,
they accurately measured their true
brightness.
The improved Hubble constant
value is 73.2 kilometres per second per
megaparsec - a megaparsec equals
3.26 million light-years. The new value
means the distance between cosmic
objects will double in another 9.8 billion
years.
Although this is some big news, we
need to be careful when reporting the
results since the refined calibration does
not quite match the expansion rate pre-
dicted for the universe from its trajectoryseen shortly after the Big Bang.
“This is quite possibly a miscalibration
somewhere in the analysis – but it
could be indicating something we don’t
understand about cosmology – that we
are living in a void, or that dark energy
has changed its spots, or possibly any
number of speculative ideas,” said lewis.
uncertainty is an important concept
in cosmology and, according to lewis
“some of the most hacks-of-science
stories make me roll my eyes with
a misrepresentation of the results
etc. Stories like [recent reports on
Dark Matter] don’t help as they do
not differentiate robust science from
rubbery speculation,” says lewis.
And what does Dr lewis hope from
his cosmic colleagues in the future?
“Continually better accuracy in
the observations – I really hope the
difference is real as it will point to
something interesting, although we
will probably have to wade through a
mountain of speculative bulldust to get
to the answer!”BETwEEn ThE CRACkSwe are now in the age of ‘precision cosmology’ and this ‘local’
measure of the expansion of the universe is significantly different to
the global measurement by Planck.iMAGE: © NoAA - Flickr