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Ever since we came up with the theory of the big bang, we been looking for evidence to back it up.
Put simply, The big bang theory is the leading explanation of how the universe came to be,
from an infinitely small but equally high density and temperature point that expanded
in a few billionths of a billionth of a billionth of a second to become all the
matter in the universe we know of now. This conjecture comes about from what
we know of how matter, space time and observations of an expanding universe,
although we some what late to the party being some 13.8 billion years after the event.
But what if we could see more direct evidence from the time there were no stars or galaxies
just the first light from the big bang itself, something which is predicted by our theories?
Well, one ESA satellite the Planck space observatory has done that in
greater detail than we have ever seen before. So this is how Planck did this and what it means
for our understanding of how the universe began and what might have been before the big bang.
The term “big bang” was first used by the English astronomer Fred Hoyle during a
BBC radio broadcast in March 1949 whilst he was describing the difference between the two main
competing theories about the universe, the steady state theory which Hoyle championed
and stated that the universe had always existed and was internal and the expansionist theory.
Fred Hoyle said in the broadcast about the expansionist theory, "These theories were
based on the hypothesis that all the matter in the universe was created in one big bang
at a particular time in the remote past." Although Hoyle never really came around to the
theory that he himself coined, the overwhelming evidence since has shown that the Big Bang theory
is the one that is most likely to have happened. In 1948, the year before Hoyles Big Bang
broadcast, the American cosmologist and scientists Ralph Alpher and Robert Herman predicted that
if there had been a massive expansion, the plasma, which is all the universe consisted
of at the time would have cooled and the first basic atoms of hydrogen and helium formed.
The universe would have gone from the opaque mass of sub-atomic particles to transparent
and that first light would have been able to travel through the expanding universe
ever since and be visible to us now. However, due to the huge expansion of
space that occurred over the last 13.4 billion years, that first light would be stretched so
much that it would be in the microwave region now, so it would be invisible to our normal
optical telescopes and would only be seen by radio telescopes and detectors. Although this
work would become key in the theory of the big bang, at the time it was pretty much ignored.
It wouldn’t be until 1964 some 16 years later before Arno Penzias and Robert Woodrow Wilson
whilst working on satellite communications for Bell Labs discovered an almost uniform background
noise in the microwave spectrum wherever they pointed their horn antenna when they were trying
to fix what they thought was a malfunction. This noise from everywhere was proof of the
first light that Alpher and Herman had predicted. Penzias and Wilson went on to
win a Nobel prize in 1978 for it but work on the CMB or comic microwave background had only
just begun. If it could be studied in detail it could provide an almost direct link to the
history of the universe just after the big bang and possibly point to what may have preceded it.
Although it had been studied, greater detail was needed and it wasn’t until
the 1980s that dedicated satellites were launched to study the phenomenon.
The first was the Soviet RELIKT-1 experiment on board the Prognoz 9 satellite in 1983 which was
followed up the NASA COBE or Cosmic Background Explorer mission which ran from 1989 to 1993.
These showed the scale and amplitude of the CBM and showed large-scale fluctuations
they lacked the resolution to see the details which would be so important.
Further ground and balloon-based experiments gained more detail and a second NASA mission, the
Wilkinson Microwave Anisotropy Probe or WMAP ran from 2001 to 2010 and was 45 times more sensitive
and made further advances providing finer details. The reason why cosmologists and scientists needed
to see the CMB in finer detail was that it was believed that fluctuations in the CMB just after
the big bang led to similar variations in the distribution of gas throughout the universe.
Where gas was denser, more star formations occurred due to the effect of gravity and
the first galaxies formed. If they could get a really high-resolution
image of the CMB it could be compared to the distribution of galaxies we see now.
In 2009, the Planck Surveyor space observatory was launched by the European Space Agency.
This had 3 times the resolution of the WMAP and scanned nine frequency bands to the WMAP’s five.
It was launched by an Ariane 5 ECA heavy launch vehicle and eventually
placed into an orbit near the L2 Lagrange point. Here it rotates around the earth as the earth
rotates around the sun. The Planck satellite also rotates at one revolution per minute,
allowing it to scan the whole sky as it moves around the sun, a similar principle to that
used by the Gaia satellite which I covered in another video which has a link to it here.
Planck uses two instruments to scan a low-frequency and a high-frequency
band from 30 to 830 Ghz though the CMB peaks at 160.2 Ghz.
In order make sure that the instruments can be as sensitive as possible, it was both passively
and actively cooled to maintain a temperature of −273.05 °C or 0.1 Kelvin above absolute zero, this
made Planck the coldest known object in space from August 2009 until its active coolant supply was
exhausted in January 2012 which rendered the high-frequency instrument unusable although the
low-frequency instrument was still working until the mission was terminated on the 3rd Oct 2013.
During it’s time Planck made two all-sky surveys which resulted in the most detailed map of the
cosmic background radiation to date. Due to the amount of data collected it has taken
several years and 3 data releases to get the full information but the results are quite amazing.
The map now pretty much correlates with the positions of filaments and galaxy clusters that
we see on the grand scale and shows the effect of dark matter and dark energy that we can’t see.
The subtle fluctuations seen in the map were imprinted on the deep sky 370,000 years after
the big bang but those fluctuations are thought to be the effect of ripples that arose as early
in the existence of the Universe as the first nonillionth of a second or 10 -30 of a second.
According to the European-led research team the Universe is 13.798 billion-years-old,
and contains 4.82% ordinary matter, that’s all the stuff we can see and that you,
me the earth, stars and galaxies are made out of.
25.8% dark matter and 69% dark energy both of which play a much greater role in the expansion
of the universe than all the ordinary matter. But what it also points to as to what might
have been before the big bang and that is even more interesting.
If there were ripples in the universe after just 10 -30 of a second, its thought that before the
exponential inflation period, there was just a sea, for want of a better word,
of energy and in that sea there were tiny ripples like we the ripples we see on a still pond.
Of course, this is very hard to visualise because if it was just energy there was
no matter and with no matter, there was no mass and without mass, there is no gravity,
time or size. The size of the universe could be smaller than a Planck length and it wouldn’t
make any difference because there is nothing to compare it against and energy has no size.
This something which has been proposed by mathematical physicist Sir Roger Penrose
that could happen in the far, far, far distant future of our universe, when all the stars have
burned out, the black holes evaporated away and the last matter has decayed into photons.
Basically, the universe will be a sea of energy at its lowest point where size and
time no longer exist and maybe this will be the trigger for the next big bang.
The Planck Surveyor has helped us understand more about what is going on in the universe and
showing us until recently hidden information in the form of the CMB from which we can
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