THE STATE OF COSMOLOGY
The most important theory for the origin of the Universe is the Big
Bang theory. Generally, we accept that the Universe started with a huge
accelerated outward motion from a superdense and superhot stage. Theoretically,
the Universe started from a mathematical singularity with infinite density.
This comes out of solutions of type I or type II of Einstein’s equations.
That is, the initial expansion happened with infinite velocity. The first
scientists to formulate the big bang theory were Lemaitre in 1927 and Gamow
in 1948. Lemaitre based his conclusions not only on Einstein’s equations,
but on the following arguments as well.
The entropy of the Universe increases with time.
Therefore, there must have existed a condition of minimum entropy where
matter had the maximum possible organisation. Lemaitre proposed the idea
of the “primordial atom” which contained all of the matter in the Universe.
The argument about the entropy of the Universe is very important. Indeed,
the increase of the entropy is one of the fundamental characteristics of
the Universe. Gamow (1948) proceeded to investigate the characteristics
of the superdense condition of the first few moments of the Universe. He
concluded that the temperature must have been enormous at this stage. Under
these conditions, the protons and neutrons must have formed the various
chemical elements. He called his new theory the Alpher, Bethe and Gamow
theory.
The Alpher, Bethe and Gamow theory satisfactorily
explains the formation of all the elements up to uranium, by continuously
adding neutrons to increasingly complex nuclei. It soon became clear, however,
that since there is no stable nucleus with mass number 5, the formation
of the elements must have stopped at helium. Thus, cosmic nucleosynthesis
was necessarily restricted to light elements, up to helium. After this
failure, the theory was put aside altogether. The next theory about the
formation of chemical elements was the B2FH theory, so named after Burbidge,
Fowler and Hoyle. According to this theory, all the elements formed in
stellar interiors. In particular the heavier elements were formed during
supernova explosions. However, as Hoyle and Tayler realised in 1964, it
could not account for the amount of helium observed in stars, which constitutes
25% of their mass. It was concluded that helium and deuterium or heavy
hydrogen must have been formed in the early Universe. So, we conclude that
there are two ways by which the elements of matter were formed. Only the
light elements (mainly deuterium and helium) were formed during the first
four minutes after the big bang. Elements heavier than helium formed later
on in the interiors of stars. This process started as soon as the first
stars were formed, and continues today.
Another indication in support of the big bang theory is the estimated
age of the Universe. Independent estimates of the age of the Universe,
based on the expansion of the Universe, the age of the oldest stars in
the galaxies, or the ages of radioactive elements, give numbers of the
same order of magnitude. All three methods agree that the age of the Universe
is between 10 and 20 billion years. If the Universe did not have a beginning,
there would not be an apriori reason for such a good agreement between
these three different calculations.
PENZIAS AND WILSON
In 1964, the engineers Arno Penzias and Robert Wilson were working
with the radio antenna that was communicating with the Telstar satellite.
The satellite was a large aluminized balloon that was supposed to reflect
radio signals back to earth. The radio antenna had to be sensitive enough
to pick up those signals. But they kept getting a faint noise that they
could not get rid of - no matter which direction they pointed the antenna.
It wasn't until they attended a seminar on the big bang theory and that
there might be some light remaining from the explosion that they realized
that their "noise" was the light from the big bang (today called cosmic
background radiation). Before Penzias and Wilson, few believed the big
bang theory. Since their discovery, however, no other view has been acceptable.
This radiation as confirmed by the COBE spacecraft, comes to us from
all directions with the same intensity, in other words (isotropically 0),
and corresponds to the radiation from a black body at a temperature of
approximately 3° Kelvin. The radiation is uniformly distributed in
space, and does not appear to be clumpy, unlike the distribution of matter.
The only credible explanation for this radiation is that it consists of
the photons which filled the Universe during the ‘radiation era’, about
300,000 years after the big bang, early in the cosmic history. No other
plausible explanation has so far been suggested for this radiation. A lot
of effort has been made to try to attribute the microwave background radiation
to galaxies or other sources. Recent observations have shown that the isotropy
of this radiation is amazing and therefore, any non-cosmological origin
of it is highly unlikely. Indeed if this radiation were due to galaxies
or stars, it would appear more intense in certain directions, contrary
to what we observe. It appears that the evidence for the expansive origin
of the Universe is very substantial.
One last piece of evidence is observed in the distribution
of radio galaxies at larger and larger distances. We essentially observe
how this distribution was when the light set off from these galaxies. Since
the Universe continuously expands, we should see higher densities of galaxies,
as we observe further in the past. Radio telescopes can detect these galaxies
and indeed Ryle (Nobel Prize 1974) discovered that the density of galaxies
increases with their distance. More recent observations confirm Ryle’s
result. This provides yet more evidence for the fact that the universe
started from a condition, which was much denser than at present.
Observations of distant galaxies reveal how the Universe was in the
distant past, when the light set off from these galaxies it was in some
cases billions of years ago. Therefore, we have good indications that the
laws of nature are not only universal, but that in general they do not
change with time over a period of billions of years. The whole of cosmology
is based exactly on the principle that the laws of nature are known, or
that it is possible for them to become known. The fact that we have various
theories concerning the Universe means that the physical laws are not entirely
known. The expansion of astronomical observations in space and the improvement
of our experimental devices help us to reject one by one the inaccurate
theories and to come up with more accurate ones which explain the phenomena
of the universe.
In summary, the basic evidence in support of the big bang theory
is:
a) The solutions of Einstein’s equations
b) The observed helium and deuterium abundance.
c) The agreement between the various independent estimates of the age
of the Universe.
d) The microwave background radiation.
HAWKING AND PENROSE
Important advances in cosmology were made in 1969 by Hawking and Penrose,
who showed that any model of the Universe which has the observed characteristics
of (approximately) homogeneity (the same everywhere) and isotropy (visibly
the same everywhere) must start from a singularity. This theory which does
not require absolute homogeneity and isotropy for the model, is one of
the most important achievements in the field of relativity. The general
theory of relativity leads to an initial singularity of the Universe. In
all observational tests to date, relativity has been vindicated. Consequently,
most researchers today work on relativistic cosmology, rather than competing
theories.
An effort had been made to avoid the singular beginning
of the Universe by introducing quantum mechanical phenomena. Such phenomena
are very important when the age of the Universe is less than 10-43 seconds
(Planck time). However as Hawking has pointed out, quantum mechanics does
not seem to eliminate singularities. Thus, the basic singularity theorum
discussed cannot be invalidated by quantum mechanics.
When one exhausts the chain of questions “why…” concerning the Universe,
one arrives at questions which remain essentially unanswered.
a) What existed before the initial explosion?
b) Why is the Universe inhomogeneous on small scales and yet homogenous
on large scales?
c) Why has space three dimensions and time only one?
d) Why are the constants of nature so universal?
e) Why is the Universe as a whole so symmetric and simple, a necessary
requirement for the remarkable progress made in cosmology?
BEFORE THE BIG BANG (New Scientist 3 June 2000)
What happened before the big bang? Try asking a cosmologist this and
they will usually fob you off by saying it’s a meaningless question. Stephen
Hawking famously likened it to asking, “what’s north of the North Pole?”
The big bang, the idea goes, was the ultimate beginning. Time and space
came into being then. There was no before. But this may not be true.
Gabriele Veneziano of CERN, the European Laboratory for Particle Physics
near Geneva says that far from being the beginning, the big bang was merely
an important point in the Universe’s history. This infinite point, known
as a singularity, is a big problem for physicists. The singularity tells
us that our description of the Universe - Einstein’s theory of gravity,
or general relativity - is not applicable in the earliest moments. The
reason is that there is a point known as the Planck time-within
10-43 seconds of the big bang-when gravity is comparable in strength
to the other forces of nature. Because of this, to deal with the physics
of the singularity you have to come up with a quantum version of gravity.
The most common quantum theory of gravity is the string theory. According
to this, the fundamental particles of nature are impossibly tiny “strings”
vibrating in a space of nine dimensions, with all but three dimensions
“rolled up” smaller than an atom. One of the fundamental vibration modes
turns out to be a massless particle that looks just like the hypothetical
carrier of the gravitational force, or, the graviton.
At the big bang, the Universe had maximum curvature,
maximum expansion rate and maximum temperature. The big bang may emerge
not as the beginning but an important turning point in the history of the
Universe. One of the advantages of the string theory is that the pre-big
bang era is automatically inflationary and there is more than enough time
for inflation to equalise the density and temperature of the Universe.
According to Veneziano, the solution of string theory that applies to the
inside of a black hole is exactly the same as the accelerated expansion
that string theory predicts for the pre-big bang era. Our Universe is likened
to a patch of the inside of a black hole. Vezeniano and Gasperini have
shown over the past few years that as the Universe expands towards t=0,
space-time becomes increasingly curved, resulting in a dramatic increase
in temperature and energy density. A split second after time zero, a millimeter
sized, three-dimensional region within this vast expanse could look just
like the superdense, super-hot patch in standard inflation theory of cosmology.
Fortunately, string theory makes several testable
predictions, which are at odds with those of the standard model of inflation.
If Veneziano is right, the Universe should be filled with a chaotic sea
of gravitational waves left over from its trivial past. The waves will
be weak, and the prospects of seeing them with the current generation of
detectors-or even their immediate successors –are not good. However, Veneziano
maintains that third-generation detectors should be able to pick up this
gravitational-wave background. Effects from the big bang should also be
visible in the cosmic microwave background, the afterglow of the big bang.
Veneziano predicts different angular positions of the peaks in the power
spectrum of the cosmic background, compared with standard theories. This
could be tested by the American MAP satellite which has just been launched
(July 2001) or the European Planck probe scheduled for 2007.
COSMIC DEUTERIUM ASSAY
One of the key numbers sought by cosmologists is the ratio of deuterium
(hydrogen 2) to ordinary, hydrogen in the material that emerged from the
Big Bang. The amount of deuterium that was formed in the first few
minutes should tell the total density of baryonic (normal) matter in the
universe. David Tyler (Uni. of California, San Diego) has made the
most accurate measurement to date by analysing hydrogen absorption lines
in a distant quasar with the Keck 10 metre telescope. A primordial gas
cloud along the line of sight to the quasar contains one atom of D for
every 40,000 of H. This implies that baryonic matter totals 4% -
5% of all matter and energy (assuming a Hubble constant of 70 Km/sec/megaparsec).
This finding matches the value now being found independently from MAXIMA
and BOOMERANG.
RECENT ADVANCES IN COSMOLOGY
The proposition of the Big Bang, the literal birth of time and space
some 13.2 billion years ago has been understood, at least in the broadest
outlines, since the 1960’s. But in more than a third of a century,
the best minds in astronomy have failed to solve the mystery of what happens
at the other end of time. Will the galaxies continue to fly apart
forever, their glow fading until the cosmos is cold and dark? Or
will the expansion slow to a halt, reverse direction and send the stars
crashing back together in a final apocalyptic Big Crunch? Some recent
cosmological discoveries have enabled a better understanding of the probabilities
for the future of the universe. These new discoveries bolster the
theory of inflation: the notion that the universe when it was still smaller
than an atom went through a period of turbo-charged expansion, flying apart
(in apparent, but not actual, contradiction of Einstein’s theories of relativity)
faster than the speed of light. Another implication is that the universe
is pervaded with a strange sort of “antigravity”, a concept originally
proposed by and later abandoned by Einstein as the greatest blunder of
his life. The force, which has lately been dubbed “dark energy” isn’t
just keeping the expansion from slowing down; it’s making the universe
fly apart faster and faster all the time.
It gets stranger still. Not only does dark
energy swamp ordinary gravity but also an invisible substance known as
“Dark Matter” also seems to outweigh the ordinary stuff of stars, planets
and people by a factor of 10 to 1. It is not known what constitutes
either dark energy or dark matter; however, astronomers and physicists
have some idea of the possible make up of this matter. Things seemed
lot simpler back in 1965 when Arno Penzias and Robert Wilson provided a
resounding confirmation of the Big Bang theory when they accidentally detected
the leftover afterglow from the Big Bang or the cosmic microwave background
radiation. About 300,000 years after the instant of the Big Bang, the entire
visible universe would have been a cloud of hot, incredibly dense gas,
not much bigger than the Milky Way galaxy is now, glowing white hot like
a blast furnace or the surface of a star.
Because this cosmic glow had no place to go, it
must still be there, albeit so attenuated that it took the form of feeble
microwaves. Penzias and Wilson later won the Nobel Prize for the
accidental discovery of this radio hiss from the dawn of time. The
discovery of the cosmic microwave background radiation convinced scientists
that the universe really had sprung from an initial Big Bang some 13 billion
years ago. They immediately set out to learn more. For one
thing, they began trying to probe this cosmic afterglow for subtle variations
in intensity. It’s clear through ordinary telescopes that matter
is not spread evenly throughout the modern universe. Galaxies tend
to huddle relatively close to one another, dozens or even hundred of them
in clumps known as clusters and super clusters. In between, there
is essentially nothing at all. This lumpiness, reasoned theorists,
must have evolved from some original lumpiness in the primordial cloud
of matter that gave rise to the background radiation. Slightly dense
knots of matter within the cloud – forerunners of today’s super clusters
should have been slightly hotter than average. So some scientists
began looking for subtle hot spots.
Others, meanwhile, researched a different aspect
of the problem. As the universe expands, the combined gravity form all
the matter within it tends to slow that expansion, much as the Earth’s
gravity tries to pull a rising rocket back to the ground. If the
pull is strong enough, the expansion will stop and reverse itself; if not,
the cosmos will go on getting bigger, literally forever. Which is
it? One way to find out is to weigh the cosmos – to add up all the
stars and galaxies, calculate their gravity and compare that with the expansion
rate of the universe. If the cosmos is moving at escape velocity,
no Big Crunch. Trouble is, nobody could calculate how much matter
there actually was. The stars and galaxies were easy to calculate
because you could see them, but it was noted as early as the 1930’s that
something else was out there besides the glowing stars and gases that astronomers
could see. Galaxies in clusters were orbiting too fast; they should
by rights, by flying off into space. Individual galaxies were spinning
about their centres too quickly as well; they should long since have flown
apart. The only possibility; some form of invisible dark matter was
holding things together, and while you could infer the mass of dark matter
in and around galaxies, nobody knew if it also filled the dark voids of
space, where its effects would not be detectable. So astrophysicists
tried another approach; determine whether the expansion was slowing down
and by how much. Brian Schmidt at the Mt. Stromolo observatory in
Australia set out to do this in 1995. The idea was straightforward;
look at the nearby universe and measure how fast it is expanding.
Then do the same for the distant universe, whose light is just now reaching
us, having been emitted when the cosmos was young. Then compare the
two. Schmidt’s group and a rival team led by Saul Perlmutter of California
measured Type 1A supernovae explosions. Type 1’s are so bright that
they can be seen all the way across the universe and are uniform enough
to have their distances calculated. Since the universe is expanding
at a given rate at any one time, more distant galaxies are moving away
from us faster than the nearby ones. So both teams measured the distances
to the supernovas, determined by their brightness, and the speed of their
recession determined by the reddening of their light. Combining these
two pieces of information gave them the expansion rate, now and in the
past. By 1998, both teams knew something strange was happening.
Cosmic expansion should have been slowing down a lot or a little but the
expansion was speeding up. After years of analysing results, the
universe was indeed speeding up, suggesting that some sort of powerful
antigravity force was at work forcing the galaxies to fly apart even as
ordinary gravity was trying to draw them together. Both groups announced
their findings almost simultaneously, and the accelerating universe was
named discovery of the year for 1998 by Science magazine.
For all its strangeness, anti-gravity did have a history, one dating
back to Einstein’s 1916 theory of general relativity. The equations
suggest that the universe must be either expanding or contracting; it simply
couldn’t be sitting there. Astronomers of the day insisted that it
was just sitting there, so Einstein grumbling about having to mar the elegance
of his beloved mathematics added an extra term to the equations of relativity.
Called the cosmological constant, it amounted to a force that opposed gravity
and propped up the universe. A decade later, Edwin Hubble discovered
that the universe was expanding after all. Einstein immediately and
with great relief discarded the cosmological constant, declaring it the
biggest blunder of this life. Even so, the idea of a cosmological
constant was not entirely dead. The equations of quantum physics
independently suggested that the seemingly empty vacuum of space should
be seething with a form of energy that would act just like Einstein’s discounted
antigravity.
The unique properties of a cosmological constant
would make the universe slow down early on, then accelerate. That’s
because dark energy grows as a function of space. There isn’t much
space in the young, small universe so, back then the braking force of gravity
would have reigned supreme. More recently, the force of gravity fell
off as the distance between galaxies grew and that same increase made for
more dark energy.
A combination of recent measurements made by C.O.B.E; MAXIMA; and BOOMERANG
projects has shown that the relative makeup of the universe is one of early
and later lumpiness composed of roughly 5% of baryonic matter, 30% of dark
matter (theoretical particles like the neutralino and axiom), and 65% of
dark energy, some of which may be virtual particles that pop into and out
of existence. The information that has been collected also tells
theorists how the universe is curved. In fact, the new measurements
from MAXIMA and Boomerang tell us that the universe is in fact flat.
Draw a triangle that reaches all the way across the universe and the angles
will always add up to 180 degrees.
According to Einstein, the universe curvature is
determined by the amount of matter and energy it contains. The universe
we live in could have been flattened purely by matter- but the new discoveries
prove that ordinary matter and exotic particles add up to only about 35%
of what you would need. Ergo, the extra curvature must come form
some unseen energy. The flatness of the universe also means that
theory of inflation has passed a key test. Originally conceived around
1980, the theory says that the entire visible universe grew from a speck
far smaller than a proton to a nugget the size of a grapefruit, almost
instantaneously, when the whole thing was less than a fraction of a second
old. This turbo-expansion was driven by something like dark energy
but a whole lot stranger. What we call the universe, in short, came
from almost nowhere in next to no time. One of the consequences of inflation,
predicted 20 years ago, was that the universe must be flat – as it now
turns out to be.
If these observations continue to hold up, astrophysicists can be pretty
sure they have assembled the full parts lists for the cosmos at last: 5%
ordinary matter, 35% exotic dark matter and about 60% dark energy.
They also have a pretty good idea of the universe’s future. All the
matter put together doesn’t have enough gravity to stop the expansion;
beyond that, the antigravity effect of dark energy is actually speeding
up the expansion. And because the amount of dark energy will grow,
as space gets bigger, its effect will only increase.
THE FUTURE OF THE COSMOS
That means that the 100 billion or so galaxies we can now see through
out telescopes will zip out of range, one by one. Tens of billions
of years from now, the Milky Way galaxy will be the only galaxy we are
aware of. By then our Sun will have shrunk to a white dwarf, giving
little light and even less heat to whatever is left of Earth, and entered
a long, lingering death that could last 100 trillion years, or a thousand
times longer than the cosmos has existed to date. The same happens
to most other stars, although a few end their lives as blazing supernovas.
Finally, though all that will be left in the cosmos will be black holes,
the burnt-out cinders of stars and the dead husks of planets. The
universe will be cold and black. Any matter left will eventually
collapse into black holes. By the time the universe is 1 trillion,
trillion, trillion, trillion, trillion years old, the black holes themselves
will disintegrate into stray particles, which will bind loosely form individual
‘atoms’ larger than the size of today’s universe. Eventually, even
these will decay, leaving a featureless, infinitely large void and that
will be that – unless of course, whatever inconceivable event that launched
the Big Bang should recur, and the ultimate free lunch is served once more.
Astronomers and physicists are a cautious crew, and they insist that the
mind-bending discoveries about dark matter, dark energy and the flatness
of space-time must be confirmed before they are accepted without reservation.
There could be surprises to come; an Einstein – style cosmological constant
for example is a leading candidate for dark energy, but it could in principle
be something subtly different – a force that could even change directions
someday, to rein force rather than oppose gravity. Results from new
tests should be within the next few years. The MAP satellite will
collect refined cosmic background data; meanwhile supernova watchers are
lobbying NASA for a dedicated telescope. If the latest results do hold
up, some of the most important questions in cosmology – how old the universe
is, what is it made of and how will it end –will have been answered, only
about 70 years after they were first posed. By the time the final chapter
of cosmic history is written – further in the future than our minds can
grasp – humanity, and perhaps even biology, may long since have vanished.
Yet, it’s conceivable that consciousness will survive, perhaps in the form
of digital intelligence. If so, then some one or something may still
be around to note that the universe, once ablaze with the light of uncountable
stars, has become an unimaginably vast, cold, dark and profoundly lonely
place.
INTERESTING FACTS.
HEAVY ELEMENTS: -
With 60 extra solar planets now catalogued, astronomers can now draw
some conclusions about planetary systems and the stars that host them.
Stars that have giant close-in planets tend to be metal rich (above average
proportions of elements H & HE) particularly in iron. The higher
the metallicity of the star, the higher will be the probability that planet
formation will occur. If we look at the spectra of stars and they are metal
rich, there is a good chance of finding planets in orbit.
MOST EARTHS ARE OLD S&T August 2001 Page 24
Charles Line Weaver UNSW. His conclusion is that the Earth is
a
relative youngster at 4.6 billion years of age. The average terrestrial
planet in the cosmos today is about 6 or 7 billion years old.
Star formation peaked 10-11 billion years ago (assuming a Big Bang
age of 13.4 billion years) and has been declining since.
Most early stars had a low metallicity and another 1.5 billion years
was needed before terrestrial planets could start forming from the waste
products of early Stellar generations. The metallicity of the universe
is still increasing steadily, as stars live out their lives and return
much of their nuclear-fusion products to the interstellar medium.
Earth was born in the greatest numbers 8 billion years ago and since
then, the rate has been tapering off. The average Earth today has
been around 6.4years. Our solar system is younger than ¾ of
the terrestrial planets now in existence.
NEUTRINOS
Results form the Canadian Sudbury neutrino detector that uses heavy
water, have shown that solar neutrinos arrive at the Earth in three types.
Electron neutrinos make up 35% of those that arrive here and the remaining
65% are of both Tau and muon neutrinos, more over they must have left the
sun as electron neutrinos 9 the only kind the sun produces) and changed
flavour along the way. These neutrinos are oscillating and quantum
mechanics states that, neutrinos can oscillate only if they had mass!
Researches had suspected that the total neutrino mass was probably not
the overwhelming contributor to dark matter, but now the Sudbury findings
permit researchers for the first time to set a firm limit; the universe’s
neutrinos make up no more than about 50% of dark matter, probably more
likely around 20%.
MICROWAVE ANISOTROPY PROBE
The MAP satellite will collect data relating to the cosmic microwave
background radiation, however, the satellite will allow astronomers to
examine the subtle markings acquired by the CMB as it traversed billions
of light years to reach Earth. This data will read like a history of our
universe’s evolution. It will take maybe a year and a half to collect
all of the data and interpret it. Look forward to the results in 2003.
MEGA UNIVERSE MAP (New Scientist 17 June 2000)
By measuring the positions of a staggering 106,688 galaxies and their
distances away from us, an international team of astronomers has produced
a three-dimensional mega-map of a swathe of the Universe with a volume
of 13 billion billion billion cubic light years. Their estimate of the
mass of this material supports a growing consensus that the Universe will
continue expanding forever. Using the Two-degree field (2df) spectrograph
at the Anglo-Australian Telescope in New South Wales, the team estimated
the distances to the fleeing galaxies by measuring their red shifts. The
map was made by combining the red shifts with the positions of the galaxies
in the sky. The new map covers 5 per cent of the sky and reaches out 4
billion light years into deep space. It shows large numbers of clusters
and superclusters of galaxies, and huge voids of space that are relatively
empty of stars. No structures are much larger than a few million light
years across. The 2df team was able to determine both the visible and non-visible
mass of the volume they surveyed. According to the results, the Universe
contains only 40 per cent of the mass needed for gravity to stop the current
expansion.
VARIABLE HUBBLE CONSTANT? (New Scientist 28 April 2001)
Our Solar System could be sitting at the centre of an optical illusion
that fools astronomers into thinking that distant galaxies are accelerating
away from us. The conclusion comes from observations that our galaxy could
exist in a particularly empty region of space. Kenji Tomita an astrophysicist
at Kyoto University says there is an alternative explanation. Observations
hint at a wall of galaxies lying between 650 million and 1 billion light
years away from us in all directions. This suggests that the Milky Way
Galaxy may lie near the centre of a local void, or a rarified region in
which galaxies are scarce and space is expanding unusually quickly. The
difference in the expansion rate, or Hubble constant, would explain why
studies of supernovae in distant galaxies seem to point to a speeding up
in the expansion of the universe, Tomita says. Observers in a local void
feel as if the Universe at the present stage is accelerating relative to
older, more remote sources. The void scenario may also explain why a supernova
11 billion light years away appears to have gone off in an era when the
expansion of the Universe was decelerating. This recent observation is
considered by some scientists to be strong evidence of dark energy, demonstrating
that its influence did not overcome the pull of gravity until the Universe
had expanded and thinned out. But Tomita says that the void would produce
the illusion that closer younger supernovae are accelerating and older,
more distant ones are decelerating. However Tomita’s idea faces some serious
challenges, for example that the Hubble constant cannot change by more
than a few per cent across distances of up to 500 million light years,
while Tomita assumes that the constant changes by roughly 20 per cent across
a distance as small as 650 million light years.
MISCELLANEOUS FACTS
Microwave photons: 1000 trillion strike a persons head every second
when outside.
Humans are made up of Carbon, Oxygen, Nitrogen and Hydrogen, the four
most common elements in the Universe.
Supernova Type II explosion =1057 neutrinos released and the total
energy released is 100 times the entire energy output of the Sun over it’s
entire lifetime, however only 1% of the energy is in the form of visible
light. 99% is carried by the neutrinos.
Type I supernovae distribute Iron.
Type II supernovae distribute oxygen.
There are one billion neutrinos in every cubic metre of the Universe.
There are 412 million photons per cubic metre left over from the big
bang.