by Laura Knight-Jadczyk
In the previous post,
we talked about the beginnings of cosmology as described by Paul Davis. Davies took on the task of ‘Explaining the
Universe’ which means describing the Standard Model and how it came to be. We learned that there appears to be no
‘center’ to the universe and everywhere you look, the space between galaxies
gets bigger and bigger as time goes by.
Thus, there is the expanding balloon analogy which says that the
universe can be finite without having a center or an edge. It also makes us realize that, whatever the
‘Big Bang’ was, it wasn’t exactly an explosion the way we think of explosions.
Davies tells us that a
telescope is a ‘timescope’, that when we observe images of distant galaxies, we
are seeing them as they appeared long before Earth existed. That is due to the fact that it takes time
for the visual to reach us at the speed of light.
As light traverses the expanding universe its wavelength stretches along
with the stretching space. ….The amount of red shift depends on how long ago
(and hence how far away) the light was emitted.
Working back towards the big bang, the red shift gets bigger and bigger.
… Going much farther back in time (and out into space), we reach the epoch from
which the CMB emanates. … CMB has
travelled to earth relatively undisturbed since about 380,000 years after the
big bang. Before that time the
temperature was too high for atoms to exist because the electrons would have
been stripped away from the nuclei by the intense heat, i.e. the atoms were
ionized. Physicists refer to a gas in
this state as plasma. Plasmas scatter
light strongly and so they are opaque: that is why we can’t peer inside the
sun… when WMAP detects the CMB, it is in
effect seeing as far back in time as is possible… No ordinary telescope or
microwave antenna, however powerful, can penetrate the glowing fog beyond.
Going in another, but
related, direction for a moment: I read an interesting article the other day: James Webb telescope discovers earliestgalaxy in the known universe — and its shockingly big . In
this article we are told:
According to new research, astronomers using the powerful infrared
telescope have revealed what appears to be the two earliest, most distant
galaxies in the known universe, dating to just 300 million years after the Big
Bang.
Besides being exceptionally old, the newly discovered galaxies — named
JADES-GS-z14-0 and JADES-GS-z14-1 — are also unusually large for such an early
time in cosmic history, according to the discovery paper published May 28 to
the preprint server arXiv. With the larger of the galaxies measuring an
estimated 1,600 light-years across, the discovery adds to a mounting pile of evidence that the earliest galaxies in the
universe grew up much faster than leading theories of cosmology predict to be
possible.
That is interesting enough, but here is another problem I read about recently: Astronomers say we may live at the center of a cosmic void 2 billion light-years wide that defies the laws of cosmologyAstronomers say we may live at the center of a cosmic void 2 billionlight-years wide that defies the laws of cosmology which says:
· Evidence suggests that our galaxy is inside a cosmic void, a vast expanse of relatively empty space.
· According to our laws of cosmology, however, this void should not exist.
· New research says that such a void may explain unusual behavior in nearby galaxies.
According to a growing list of evidence, we live in the crosshairs of a
giant cosmic void — the largest ever observed. Astronomers first suggested such
a void in 2013 and the evidence for its existence has been stacking up ever
since.
But the kicker is that this giant void shouldn't exist in the first
place. If it does exist, that means something is probably amiss with our
understanding of the cosmos.
According to a fundamental theory of cosmology called the cosmological
principle, matter in the universe should be uniformly distributed on very large
scales.
The reason this matters is that by assuming uniformity, scientists can
apply the same laws of physics to nearby objects as objects at the fringes of
the early universe. In other words, everything operates under the same
universal laws. …
However, multiple observations over the last decade suggest that matter
in the universe may clump into regions of high- and low densities, meaning it's
not so uniform, after all.
"By now it's pretty clear that we are in a significant
underdensity," Indranil Banik, a postdoctoral research fellow at the
University of St. Andrews, told Business Insider.
"There's a few people that are still opposed to it to a limited
extent. For example, some people have correctly argued that such a void
shouldn't exist in the standard model, which is true. That unfortunately
doesn't prove it's not there," he added.
Banik co-authored a paper published late last year in the peer-reviewed
journal Monthly Notices of the Royal Astronomical Society that suggests we may
live near the center of this void — called the KBC void — about 2 billion
light-years across. Wide enough to fit 20,000 Milky Way Galaxies in a row
stretching from one end to the other. …
The KBC void isn't totally empty. It can't be, because we live in it.
But, if Banik and his colleagues' calculations are correct, the void would be
about 20% emptier than space outside its border.
That may not seem like a big deficit, but it's enough to cause some
confusing behavior in our local cosmic neighborhood, according to the recent
study.
In particular, nearby stars and galaxies are moving away from us faster
than they should be. Cosmologists have a value, called the Hubble constant,
which they use to help describe how fast the universe's expansion is
accelerating.
The Hubble constant should be the same value wherever you look, whether
it's close by or very far away. The problem is that the galaxies and stars in
our local neighborhood appear to be moving away from us faster than the Hubble
constant predicts, essentially defying our law of cosmology that describes how
the universe grows and evolves.
Astronomers can't agree on what's causing this discrepancy in the Hubble
constant, and the contention has become known as the Hubble tension.
Banik and his colleagues suggest that the void could be a solution
because high-density regions with stronger gravity outside the void could be
pulling galaxies and stars toward them.
Banik argues that these outflows could explain why cosmologists have calculated
a higher value for the Hubble constant when looking at nearby objects. Stuff
moves faster in the void, flying out of our empty region towards crowded outer
space.
New research suggests the KBC void is a 2 billion light-year-wide
expanse of relatively empty space, and our galaxy sits right near the center of
it. Pablo Carlos Budassi / Wikimedia Commons
© Pablo Carlos Budassi / Wikimedia Commons
Back to our main
topic. According to the Standard Model,
which Davies is describing, light can have travelled at most 13.7 billion years
and we cannot see beyond that point and so, for a while, it was said that the
universe is that old. (Well, getting older every second!) Nowadays, we can see much further thanks to
the Hubble telescope. Apparently Hubble
can see at least 28 billion years back in time.
We also have to keep in mind that even as light is moving across the
universe, space itself is expanding ahead of it and therefore, travel time is
greatly extended.
Scientists have
estimated that the observable universe contains about 1050 tons of visible matter which combines to
create a powerful gravitational field which warps the geometry of space. “So, what is the shape of space,” Einstein
asked himself in 1917. Because
gravitation warps the geometry of space, in Einstein’s mathematical model of
the universe, this warping, averaged over billions of light years, makes space
a hypersphere. According to Einstein, one can set off in one direction and keep
going and going and end up back where you started. The universe is unbounded, but finite.
As Davies says, we don’t know what lies over the cosmic visual horizon but it is probably more of the same, especially considering the Einstein cosmic balloon model. That being said, what is inside the balloon? What is inside Einstein’s ‘hypersphere’?
Well, apparently, we can’t know that because we are trapped on the 3 dimensional surface of the sphere. And the same holds true for the ‘exterior’ of the balloon. We really are like the beings in the novella “Flatland” only it’s a little more complicated because we are 3D beings in a 3D world, and we are talking about hyperdimensions basically all around us. Paul Davies thinks this is irrelevant:
Try to put yourself in the position of a pancake-like creature
restricted to life on the surface of a round balloon. The pancake might conjecture about what lies
inside the balloon (air, empty space, green cheese…), but whatever there is
doesn’t affect the pancake’s actual experience because it cannot access the
space inside the balloon, or receive any information from it. … the pancake doesn’t need a god’s eye view
of the balloon to conclude that its world is spherical – closed and finite, yet
without boundary. The pancake can deduce
this entirely by observations it can make from the confines of the spherical
surface: the sphericity is intrinsic to the surface, and does not depend on it
being embedded in an enveloping three-dimensional space. How can the pancake tell? Well, for example, by drawing triangles and
measuring whether the angles add up to more than 180’. Or the pancake could circumnavigate its
world. In the same vein, humans could
deduce that we are living in a closed, finite, hyperspherical Einstein space
without reference to any higher-dimensional embedding or enveloping space,
merely by doing geometry within the space.
So, the existence or otherwise of an ‘interior’ or ‘exterior’ region of
the Einstein universe, not to mention what it consists of, is quite simply
irrelevant. But if you would like to
imagine inaccessible empty space there for ease of visualization, they go
ahead. It makes no difference.
Yet, Davies then
begins to discuss other dimensions than the 3 we experience. Since we can’t see them, they must be
hidden. But how? According to Davies, there are two ways. The first was suggested by Oskar Klein in the
1920s. His idea was to consider a hose
which, from a distance, looks like a line.
When you get closer, the ‘line’ turns out to be a two-dimensional sheet
rolled into a tube. A point on the line
would then turn out to be a circle around the circumference of the tube. His suggestion was that what we take to be
points of 3D space are actually little circles going around a 4th
dimension. This ‘rolling up’ of
dimensions is called ‘compactification’ and there is no limit to the number of
extra dimensions that can be compactified though there are a variety of ways
they can compactify. The different
shapes that can result are referred to as ‘topologies’. The more dimensions, the more possible
topologies. So, when talking about the
shape of space, you have to specify how many ‘large’ (i.e. seen) dimensions
there are, and how many are compactified (i.e. unseen).
The second way that
extra dimensions might be hidden from view would be if we are trapped in the
three dimensions we observe and are not able to move in the extra
dimensions. Such trapping would also
trap light since we cannot see the 4th dimension. The idea that we are prisoners in our 3D
reality emerges naturally in what are known as ‘brane theories’. There it is suggested that our 3D universe is
a ‘three brane’ embedded in four space dimensions.
Davies concludes that there seems to be a
reason that nature has decreed that we live in a three dimensional world
(however many hidden dimensions there are).
According to English mathematician, Gerald Whitrow, if space had four
dimensions and the laws of gravitation and electromagnetism remained unchanged,
the inverse square law would become an inverse cube law, and the Earth would
have spiraled into the Sun long ago along with many other disasters. Life would
be impossible in space with any more ‘large’ dimensions than three. So, as Davies notes: three dimensions are ‘just
right’ like baby bear’s porridge was for Goldilocks.
To be continued .......
"The world is a (3 + 1)-dimensional metrical manifold; all physical field-phenomena are expressions of the metrics of the world. (Whereas the old view was that the four-dimensional metrical continuum is the scene of physical phenomena; the physical essentialities themselves are, however, things that exist “ in “ this world, and we must accept them in type and number in the form in which experience gives us cognition of them: nothing further is to be “comprehended” of them.) We shall use the phrase “state of the world-aether” as synonymous with the word “ metrical structure,” in order to call attention to the character of reality appertaining to metrical structure ; but we must beware of letting this expression tempt us to form misleading pictures."
"Let us start this paper with a personal but meaningful story that has oriented my research during the last forty years or so, since the French ” Grandes Ecoles ” created their own research laboratories. Being a fresh permanent researcher of Ecole Nationale des Ponts et Chauss´ees in Paris, the author of this paper has been asked to become the scientific adviser of a young student in order to introduce him to research. As General Relativity was far too much difficult for somebody without any specific mathematical knowledge while remembering his own experience at the same age, he asked the student to collect about 50 books of Special Relativity and classify them along the way each writer was avoiding the use of the conformal group of space-time implied by the Michelson and Morley experiment, only caring about the Poincar´e or Lorentz subgroups. After six months, the student (like any reader) arrived at the fact that most books were almost copying each other and could be nevertheless classified into three categories:• 30 books, including the original 1905 paper ([9],[23]) by Einstein, were at once, as a working assumption, deciding to restrict their study to a linear group reducing to the Galilei group when the speed of light was going to infinity. It must be noticed that people did believe that Einstein had not been influenced in 1905 by the Michelson and Morley experiment of 1887 till the discovery of hand written notes taken during lectures given by Einstein in Chicago (1921) and Kyoto (1922).• 15 books were trying to ” prove ” that the conformal factor was indeed reduced to a constant equal to 1 when space-time was supposed to be homogeneous and isotropic.• 5 books only were claiming that the conformal factor could eventually depend on the property of space-time, adding however that, if there was no surrounding electromagnetism or gravitation, the situation should be reduced to the preceding one but nothing was said otherwise.The student was so disgusted by such a state of affair that he decided to give up on research and to become a normal civil engineer. "
Branes seem like a good idea for having universe states for worldlines to connect between and extra dimensions seem like a good idea for having enough basis vectors to make things with. Branes commonly seem to have two extra worldsheet dimensions as part of what to float in and they seem suspiciously like the two extra conformal ones you use a lot.
ReplyDeleteThe two extra kind of create four extra as in a 4-complex spacetime including 3-complex space aka that hypersphere with a 3-dim surface and a complex-dim inside. A degenerate metric could be something we haven't thought about if you hadn't already for 4th density. No idea what 5th density could possibly be.
From my discussion on another platform:
ReplyDeleteHi
@Ark
. I started looking at this and saw it was the second part of a discussion, so I started reading through Part 1. I've now read about half of it. I'm delighted to see Laura is flagging up a book by Paul Davies. I haven't read this particular one, but he was probably foremost among the writers that first fired my fascination with fundamental physics, when I was a teenager in the late 1980s/early 1990s.
...
I think there's something that Laura highlights which I agree with: that there are prevailing narratives which are hangovers from theology. In my view, one of the most persistent of these is anthropocentric language and thinking - the (often unconscious) assumption that humans are the pinnacle of the development of life on Earth, that humans are the only "truly intelligent" beings, far superior in all types of intellect to any other lifeforms, and even that humans are the only creatures with "consciousness"
....
When it comes to "consciousness", we can only discuss it in a meaningful way if we have an understanding of what we mean by the term. I think the question that Laura's blog post begs is: what is consciousness - what does the word actually mean? The Cambridge Dictionary defines it as "the state of understanding and realizing something", or "the state of being awake, thinking, and knowing what is happening around you".
...
Ark
Hi T,
I will share your post with Laura. As for quantum mechanics (or quantum field theory if you prefer) I think that the crucial concept that you are referring to is that of "observation". I do not consider quantum theory as "self-consistent", because "observation" does not have its counterpart in its mathematical formalism. I think consciousness (whatever it means) is involved in setting up the problem to observe then "observe", then give a "meaning" to this observation. Also: quantum theory needs "probability", and to talk meaningfully about "probability" some conscious selections must be done. Selecting what is "essential" and what "can be neglected". Of course we can program a computer to do the experiment, but then conscious mind is involved in the programming.
And concerning Laura's post, the Goldilocks Enigma is in the logically connected series that started with "Wednesday, March 6, 2024 Why? The Purpose of the Universe",