- 4069 - MYSTERIES
IN ASTRONOMY? ASTRONOMY
- mysteries. No physicist would
dare assert that our physical knowledge of the universe is near completion. To
the contrary, each new discovery seems to unlock a Pandora's box of even
bigger, even deeper physics questions.
Here are some astronomical mysteries.
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---------------------
4069 - MYSTERIES
IN ASTRONOMY?
- These are big mysteries that astronomers and
I am trying to solve. In our family I
tend to work on these big problems and my wife works on the rest. She takes care of those lesser problems that
we tend to encounter in our daily lives.
Here is the list I am working:
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- It all starts when in 1900, the British
physicist Lord Kelvin is said to have pronounced: "There is nothing new to
be discovered in physics now. All that remains is more and more precise
measurement." Within three decades, quantum mechanics and Einstein's
theory of relativity had revolutionized the field. We still see new discoveries looming that
lord Kelvin did not anticipate.
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- What is dark energy? No matter how astrophysicists crunch the
numbers, the universe simply doesn't add up. Even though gravity is pulling
inward on space-time, it keeps expanding
outward faster and faster. To account for this, astrophysicists have proposed
an invisible force that counteracts gravity by pushing space-time apart.
-
- They call it “dark energy“. In the most
widely accepted model of dark energy, it is a "cosmological constant",
an inherent property of space itself, which has "negative pressure"
driving space apart. As space expands, more space is created, and with it, more
dark energy.
-
- Based on the observed rate of expansion,
scientists know that the sum of all the dark energy must make up more than 70
percent of the total contents of the universe. But no one knows how to look for
it.
-
- What is dark matter? Evidently, about 84 percent of the matter in
the universe does not absorb or emit light. "Dark matter," as it is
called, cannot be seen directly, and it hasn't yet been detected by indirect
means, either. Instead, dark matter's existence and properties are inferred
from its gravitational effects on visible matter, radiation and the structure
of the universe.
-
- This shadowy substance is thought to pervade
the outskirts of galaxies, and may be composed of "weakly interacting
massive particles," or WIMPs. Worldwide, there are several detectors on
the lookout for WIMPs, but so far, not one has been found. One recent study
suggests dark mater might form long, fine-grained streams throughout the
universe, and that such streams might radiate out from Earth like hairs. But, who knows?
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- Why is there an arrow of time? The fact that you can't un-break an egg is a
common example of the law of increasing “entropy“. Time moves forward because a property of the
universe called "entropy," roughly defined as the level of disorder,
only increases, and so there is no way to reverse a rise in entropy after it has
occurred. You can’t unbreak an egg!
-
- The fact that entropy increases is a matter
of logic: There are more disordered arrangements of particles than there are
ordered arrangements, and so as things change, they tend to fall into disarray.
But the underlying question here is, why was entropy so low in the past? Why
was the universe so ordered at its beginning, when a huge amount of energy was
crammed together in a small amount of space?
The cosmos is expanding ever since.
-
- Are there parallel multi-universes? Astrophysical data suggests space-time might
be "flat," rather than curved, and thus that it goes on forever. If
so, then the region we can see is just one patch in an infinitely large "quilted
multiverse."
-
- At the same time, the laws of quantum
mechanics dictate that there are only a finite number of possible particle
configurations within each cosmic patch , which contains 10^10^122 distinct
possibilities.
-
- So, with an infinite number of cosmic
patches, the particle arrangements within them are forced to repeat ,infinitely
many times over. This means there are
infinitely many parallel universes: cosmic patches exactly the same as ours ,
as well as patches that differ by just one particle's position, patches that
differ by two particles' positions, and so on down to patches that are totally
different from ours.
-
- Why is there more matter than
antimatter? The question of why there is
so much more matter than its oppositely-charged and oppositely-spinning twin,
antimatter, is actually a question of why anything exists at all. One assumes
the universe would treat matter and antimatter symmetrically, and thus that, at
the moment of the Big Bang, equal amounts of matter and antimatter should have
been produced.
-
- But if that had happened, there would have
been a total annihilation of both: Protons would have canceled with
antiprotons, electrons with anti-electrons (positrons), neutrons with
antineutrons, and so on, leaving behind a dull sea of photons in a matter less
expanse.
-
- For some reason, there was excess matter that
didn't get annihilated, and here we are. For this, there is no accepted
explanation. The most detailed test to date of the differences between matter
and antimatter confirm they are mirror images of each other, providing exactly
zero new paths toward understanding the mystery of why matter is far more
common. Thank God it turned out that
way.
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- What is the fate of the universe? The fate of the universe strongly depends
on a factor of unknown value: Ω, Omega, a
measure of the density of matter and energy throughout the cosmos. If Ω, Omega, is
greater than 1, then space-time would be "closed" like the surface of
an enormous sphere.
-
- If there is no dark energy, such a universe
would eventually stop expanding and would instead start contracting, eventually
collapsing in on itself in an event dubbed the "Big Crunch." If the
universe is closed but there is dark energy, the spherical universe would
expand forever.
-
- If Ω, Omega, is
less than 1, then the geometry of space would be "open" like the
surface of a saddle. In this case, its ultimate fate is the "Big
Freeze" followed by the "Big Rip": first, the universe's outward
acceleration would tear galaxies and stars apart, leaving all matter frigid and
alone. Next, the acceleration would grow so strong that it would overwhelm the
effects of the forces that hold atoms together, and everything would be
wrenched apart.
-
-
If Omega, Ω = 1, the universe would be “flat“,
extending like an infinite plane in all directions. If there is no dark energy,
such a planar universe would expand forever but at a continually decelerating
rate, approaching a standstill. If there is dark energy, the flat universe
ultimately would experience runaway expansion leading to the Big Rip.
Regardless how it plays out, the universe is dying. Happy New Year you do not have much to look
forward to.
-
- How do measurements collapse quantum wave
functions? In the strange realm of
electrons, photons and the other fundamental particles, quantum mechanics is
the law. Particles don't behave like tiny balls, but rather like waves that are
spread over a large area. Each particle is described by a "wave
function," or “probability distribution“, which tells what its location,
velocity, and other properties are more likely to be, but not what those
properties are.
-
- The particle actually has a range of values
for all the properties, until you experimentally measure one of them, its
location, for example, at which point
the particle's wave function "collapses" and it adopts just one
location.
-
- How and why does measuring a particle make
its wave function collapse, producing the concrete reality that we perceive to
exist? The issue, known as the “measurement problem“, may seem esoteric, but
our understanding of what reality is, or if it exists at all, hinges upon the
answer.
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- Is string theory correct? When physicists assume all the elementary
particles are actually one-dimensional loops, or "strings," each of
which vibrates at a different frequency, physics gets much easier.
-
- String theory allows physicists to reconcile
the laws governing particles, called quantum mechanics, with the laws governing
space-time, called general relativity, and to unify the four fundamental forces
of nature into a single framework.
-
- But the problem is, string theory can only
work in a universe with 10 or 11 dimensions: three large spatial ones, six or
seven compacted spatial ones, and a time dimension. The compacted spatial
dimensions, as well as the vibrating strings themselves, are about a billionth
of a trillionth of the size of an atomic nucleus. There's no conceivable way to
detect anything that small, and so there's no known way to experimentally
validate or invalidate string theory.
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- Is there order in chaos? For example: Physicists can't exactly solve
the set of equations that describes the behavior of fluids, from water to air
to all other liquids and gases. In fact, it isn't known whether a general
solution of the so-called Navier-Stokes equations even exists, or, if there is
a solution, whether it describes fluids everywhere, or contains inherently
unknowable points called “singularities“.
-
- As a consequence, the nature of chaos is not
well understood. Physicists and mathematicians wonder, is the weather merely
difficult to predict, or inherently unpredictable? Does turbulence transcend
mathematical description, or does it all make sense when you tackle it with the
right math? It all comes down to the
math. Was math invented or discovered in
the first place?
-
- Do the universe's forces merge into one? The universe experiences four fundamental
forces: electromagnetism, the strong nuclear force, the weak interaction (also
known as the weak nuclear force) and gravity.
-
- To date, physicists know that if you turn up
the energy enough, for example, inside a particle accelerator , three of those
forces "unify" and become a single force. Physicists have run
particle accelerators and unified the electromagnetic force and weak
interactions, and at higher energies, the same thing should happen with the
strong nuclear force and, eventually, gravity.
-
- Even though theories say that should happen,
nature doesn't always oblige. So far, no particle accelerator has reached
energies high enough to unify the strong force with electromagnetism and the
weak interaction. Including gravity would mean yet more energy.
-
- It isn't clear whether scientists could even
build one that powerful; the Large Hadron Collider (LHC), near Geneva, can send
particles crashing into each other with energies in the trillions of electron
volts (about 14 tera-electron volts, or TeV). To reach grand unification
energies, particles would need at least a trillion times as much, so physicists
are left to hunt for indirect evidence of such theories.
-
- Besides the issue of energies, the Grand
Unified Theories (GUTs) still have some problems because they predict other
observations that so far haven't panned out. There are several GUTs that say
protons, over immense spans of time (on the order of 10^36 years), should turn
into other particles.
-
- This has never been observed, so either
protons last much longer than anyone thought or they really are stable forever.
Another prediction of some types of GUT is the existence of magnetic monopoles,
isolated "north" and "south" poles of a magnet , and nobody
has seen one of those, either. It's possible we just don't have a powerful
enough particle accelerator. Or, physicists could be wrong about how the universe
works
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- I will continue to work on these
problems. If you have any breakthroughs
please let me know. I have to stop right
now my wife wants me to carry out the garbage.
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-
June 27, 2023 MYSTERIES
IN ASTRONOMY? 2548
4063
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