(Happy Birthday to astronomer Vera Rubin, born on this day in 1928!)
The periodic table of the chemical elements as we know it that
dates back to the 19th century. So at the end of the 19th century, the
understood theory of what the universe is made from is, there are more than a
hundred different chemical elements. John Dalton, through his work on stoichiometry,
concluded that each element of nature was composed of a single, unique type of
particle. And thanks to this Dalton's atomic theory, what he said was that for
every element like hydrogen, and helium, lithium and so on, there was an atom,
which was thought to be something fundamental, indivisible, indestructible
little thing and you had different atoms, one for every element. Then at the
turn of the 20th century when the electron was discovered, that revised
everything. During the same period, Einstein first suggested that the universe
is dominated by gravity and there could be a “cosmological constant,” a kind of
anti-gravity that pushes back to keep the universe static and prevent it from
collapsing inward and then other people said that universe is expanding. In
1924, Edwin Hubble announced that we are not alone that the Milky Way is just
one of many galaxies in the universe. Hubble measured the distances to galaxies
and provided evidence for the expansion of universe. In the early 1930s, it was
discovered that the nucleus itself is made of even smaller things called
protons and neutrons. Inside the atomic nucleus, in the middle there are big
heavy particles protons and neutrons stuck together by the nuclear force and there
are electrons orbiting on the outside attracted to the nucleus by the
electromagnetic force. So until the early part of the 20th century, it went
with notion that the matter we see and most of the matter there in the universe
would be protons and neutrons with accelerating electrons creating the light,
but that came into question in the early 1930s; when Fritz Zwicky a Swiss
astrophysicist at Caltech studied the Coma Cluster of galaxies located over 300 million light years away with an immense and home to thousands
of individual galaxies spanning 25 million
light-years in diameter. This was barely a decade after the realization that the Milky
Way was not alone in the universe and numerous other galaxies exists as scattered
throughout the cosmos. Zwicky looked at it in a
number of ways, first he used galaxies motion to calculate mass and then he
also used galaxies luminosity to calculate mass, his processes were not precise
but they do provide approximate figures for the mass of the cluster. He noticed
something funny about the way they moved that the galaxies in the coma cluster were moving
far too fast, with only the gravitational effect of the galaxies in play each
galaxy in coma should have been travelling sedately in its orbit. Zwicky reasoned that the individual galaxies in coma were held in
their orbits by the gravitational pull of all the other galaxies around it. He
realized that by measuring the galactic speeds he could determine just how much
mass was in the coma cluster providing a new way of weighing the galaxies, but
instead what Zwicky found was a big problem. And with immense
speeds of almost a thousand kilometers per second, coma should have been
tearing itself apart because all the stars in
all those galaxies had far too little gravity to hold the cluster together, it was clear
significantly more gravity was needed to hold coma together. Zwicky thought that something else must be biding them to each
other. That mysterious missing component would have to weigh something like 50
times as much as the stars themselves. What was the source of this extra gravity with
nothing obvious Zwicky concluded that there
must be ‘duncal materi’ (meaning dark matter) that gravitationally binding the coma
cluster and there had to be a lot more dark matter than the stars we can see.
Over the course of the 20th century, it became clear that there
is much more to the universe than meets the eye. In 1933 Fritz Zwicky at Caltech,
by studying the dynamics of clusters of galaxies, concluded that there is not
enough visible matter in the galaxies to hold the clusters together
gravitationally. He also pointed out that the measured quantity of luminous
matter was far below the value that would be necessary for critical density—i.e.,
to produce a universe with an expansion that would gradually slow to a halt at
infinity—but he speculated that the dark matter could conceivably be enough to make
up the difference. Astronomers were faced with a stark question, is there an entire
shadow universe of dark matter out there? What is it made from? And how can we
measure it? Zwicky's discovery should have set the astronomy world on fire but
because of his brusque style, no one paid much
attention to this wild notion by considering it as just one of Zwicky’s crazy
ideas and so instead
there was silence. This was a shocking
surprise and a lot of people didn’t believe it, because it is quite unnatural
according to what their understanding about physics. This notion of dark
matter lay buried in the pages of scientific journals and for the next few
decades astronomers had a new focus measuring the expansion speed of the universe.
By the 1970s there were new technological advances large telescopes and
sensitive instruments for observing the heavens and with these a new generation
of astronomers was asking new questions about the universe. The evidence for
dark matter was growing and it was now they turned to Einstein's seemingly
inconsequential theoretical prediction made more than half a century before; they
turned to gravitational lensing. Rubin
results were confirmed over subsequent decades by radio astronomers, the
discovery of the cosmic microwave background, and images of gravitational
lensing. And
so Zwicky's dark matter was back in the spotlight, it was becoming clear that
what we could see with our telescopes the myriads of stars and clouds of gas were
nothing but minor cosmic players. Today
many physicists continue to study the dark matter, using data from various
telescopes and also Geneva where the Large Hadron Collider lurks underground,
improving our understanding of particle physics. The cosmic pie depicts that
ordinary baryonic matter, including everything made of atoms from the periodic
table of which made all the galaxies, and stars, and planets in the universe;
everything that Standard Model describes is just 5% of the total content of the
universe. And more than five times of the known universe that we are made of; is
the invisible dark matter stuff which is 27% of that cosmic pie, the matter
that interacts with gravity but not light.
There are a number of
different ways of working out how much dark matter is out there in the
universe. So there is the gravitational lensing method which can be used across
the whole sky and map the distribution of dark matter by how light is being
bent through space and comparing it with the bending expected from the visible
matter. In 2018 an enormous blue supergiant star nicknamed Icarus became
the farthest individual star ever seen spotted by Hubble, formed nine billion
years ago which existed four billion years after Earendel. The Hubble Space
Telescope, 32 years after its launch, broke the all-time record for discovering most distant star substantially further away than Icarus. Just before its 32nd
birthday Hubble spotted farthest star humanity ever seen “Earendel” setting its
new record discovering fetching this star light from within the 1st billion
years after the Big Bang appearing to us as it did when the universe was only 7
percent of its current age (at redshift 6.2). That
is a dot of light that shone 12.9 billion years ago, or just 900 million years
after the Big Bang. Earendel is only visible because of an intervening galaxy
cluster WHL0137-08 creating the cosmic distorted lens in the space which
magnifies the light, seen as the red arc named as 'Sunrise Arc' which
represents the entire galaxy that Earendel is a part of. This find is a huge leap looking further back in cosmic time as
the previous single-star record holder detected by Hubble in 2018 was an
enormous blue star nicknamed “Icarus", existed when the universe was about
4 billion years old, or 30 percent of its current age. Until now, Icarus was
the most distant single star on record, at a time that astronomers refer to as
“redshift 1.5” and now we have Earendel at "redshift 6.2". Scientists
use the word “redshift” because as the universe expands, light from distant
objects is stretched or “shifted” to longer, redder wavelengths as it travels
toward us. Hubble's
observations of gravitational lensing effects have also given us a glimpse of
the cosmos that will be unveiled by the James Webb Space Telescope. JWST may uncover objects from even earlier times in the
universe’s history than what Hubble can see because this new infrared telescope
will be sensitive to light from more distant objects. Upcoming wide-area
surveys from the Vera Rubin Observatory and Euclid combined with detailed
follow-up from James Webb Space Telescope will provide a revolution in the
understanding of early universe. One of the scientific goals of the Vera Rubin
Observatory is to study the dark energy and dark matter by measuring weak
gravitational lensing, baryon acoustic oscillations and photometry of type Ia
supernovae, all as a function of redshift. Similarly, the objective of the
Euclid, visible to near-infrared space telescope is to better understand dark
energy and dark matter by accurately measuring the acceleration of the
universe.
Earendel is positioned along a ripple in space-time, massive
galaxy cluster which bend and focus the light from more distant background
objects and so Earendel gets extreme magnification, allowing it to emerge into
view from its host galaxy, which appears as a red smear/arc across the sky. The
Hubble Frontier Fields observing campaign drew upon the power of massive
clusters of galaxies to unleash the full potential of the Hubble Space
Telescope. Hubble's sensitivity and high resolution allow it to see faint and
distant gravitational lenses that are harder to detect with ground-based
telescopes. Gravitational lensing is a phenomenon created by extremely
concentrated masses like the galaxy clusters. Their strong gravity warps the
surrounding space, and light from distant objects travelling through that
warped space is curved away from its straight-line path, as if passing through
a lens. Hubble can resolve details within the multiple banana-shaped arcs that
are one of the main results of gravitational lensing as the images of
background sources are distorted. An important consequence of lensing
distortion is magnification, allowing us to observe objects that would otherwise
be too far away and too faint to be seen. Hubble makes use of this
magnification effect to study beyond the sensitivity of its 2.4 meter diameter
primary mirror by showing us the most distant galaxies/stars humanity has ever
encountered. Einstein's notebooks indicate that he had realized that if an
observer was located at the correct distance, the deflected light rays from
around the celestial object would converge to make a magnified image. This
phenomenon is known as gravitational lensing, and the amount of bending is one
of the predictions of Albert Einstein's general theory of relativity that light
should be bent by gravity.
This is the First Deep Field image from NASA’s James Webb Space
Telescope. It is the deepest and sharpest infrared image of the distant
universe to date, looking far back in time when the Universe was less than a
billion years old. This Webb’s First Deep Field image is covering a patch of
sky approximately the size of a grain of sand held at arm’s length by someone
on the ground and yet overflowing with detail as it reveals thousands of
galaxies – including the faintest objects ever observed in the infrared – have
appeared in Webb’s view for the first time in this tiny sliver of vast
Universe. It shows galaxy cluster SMACS 0723 as it appeared 4.6 billion years
ago, with many more galaxies in front of and behind the cluster. There are
stars, the things with the kind of cross twinkie patterns. But everything else,
pretty much, is a galaxy. These are extremely distant galaxies, sort of almost
out to the edge of as far as we can see with telescopes. So, for example, in
the center of the image, you can see there's a kind of cluster of galaxies, kind
of blobs. Now, hopefully you should be able to also see that on this image,
there is this smearing pattern. So there's kind of circular structures arranged
around this central cluster of galaxies. Multi-wavelength studies have led to
the discovery of numerous new objects in space & have allowed us to
"see" the Universe as never before. With advances in technology &
the ability to place telescopes into space, we can now see the Universe in all
of its light! All the wavelengths of the electromagnetic spectrum have
something important to say. We can learn from each wavelength, by observing the
Universe in a various wavelengths of light to understand the complete picture.
Multi-wavelength astronomy fetch us complete picture of the universe as
observing it in different wavelengths from radio, microwave, infrared, optical,
ultraviolet, x-ray to gamma rays. Since the Webb's successful launch last year,
now we have multi-wavelength composite images from Webb and NASA’s great
observatories at various wavelengths. Chandra
is an incredible piece of equipment and it is part of a suite of other
observatories so called NASA's great observatories which includes Hubble,
Spitzer and the Compton gamma-ray observatory. Webb Deep Field shows how galaxy
cluster SMACS J0723, located ~4.2 billion light-years away, contains hundreds
of galaxies. Galaxy clusters are filled with vast reservoirs of superheated gas
seen only in X-ray light. In the same image later Chandra data (blue in color)
revealed gas with temperatures of tens of millions of degrees, possessing a
total mass about 100 trillion times that of the Sun. Invisible dark matter
forms an even larger fraction of the cluster’s total mass compared to the measured
quantity of luminous matter.
Gravitational lensing basically acts like a lens and we end up
getting this kind of smeared multiple image of the same galaxy across the whole
sky, which you can see in the JWST’s first image so called Webb Deep Field. Why
do some of these galaxies in this image appear bent? This smearing is something
called gravitational lensing. The combined mass of this galaxy cluster acts as
a gravitational lens magnifying more distant galaxies, including some seen when
the Universe was less than a billion years old. So this is essentially where
light from a distant galaxy travels towards the earth. Now thanks to Einstein,
we know that gravity doesn't just make matter move in orbits or curves. It also
curves space time, and it will cause light to travel in curved paths. As the
light leaves the galaxy and travels past this heavy object (galaxy cluster
between JWST and the distant galaxy), it get bent by cluster gravity and pulled
back towards the JWST again. So we have evidence of dark matter from lensing
and also by looking at the rotations of stars around galaxies, we can calculate
to a fairly high degree of confidence how much dark matter is out there, even though
we can't see it which Vera Rubin famously studied in 1970s. Vera Rubin was an
American astronomer who pioneered work on galaxy rotation rates. She targeted the large
spiral galaxies similar to our own milky way, working with her collaborator
Kent Ford she wanted to understand how these galaxies spin. Vera Rubin in the 1970s was looking at Andromeda and the other
neighboring galaxies; she measured the rotation speeds of the stars in those
galaxies. The
expectation was that these galaxies were like the solar system with most of the
mass concentrated towards the center. So closer to the center of the galaxy you have
lots of gravity and the stars should be orbiting very quickly in order to not
fall into the center and just like the planets the speeds of stars in the spiral
disk were expected to fall as gravity gets weaker towards the edge of the galaxy, but this was not
what Rubin found. The rotation speed of stars did not diminish but remained
roughly the same all the way to the edge of the galaxies. She uncovered the discrepancy between the predicted and observed
angular motion of galaxies by studying galactic rotation curves. Identifying
the galaxy rotation problem, her work provided the first evidence for the existence
of dark matter.
Vera Rubin did some pretty
incredible things as helping to prove the existence of dark matter. She
uncovered the discrepancy between the predicted and observed angular motion of galaxies
by studying galactic rotation curves. She used calculations to show that
galaxies contain at least five to ten times more dark matter than ordinary
matter which is really considered as one of the biggest and most important
discoveries in astronomy, an early indication that spiral galaxies were surrounded by dark
matter haloes. Rubin's results were confirmed over
subsequent decades, and became the first persuasive results supporting the
theory of dark matter, initially proposed by astronomer Fritz
Zwicky in the 1930s. Vera Rubin was the first woman in 1965 to use the
telescope at the Palomar Observatory which was the biggest telescope in the
world at the time and this was a major step because before that women weren't
allowed to do that. It was incredible that she finally had that dare, her want
to use the biggest telescope in contemporary period and we are overcompensating
for something with this giant telescope as she really had to work hard to get
to that point. She was born in 1928 when a scientific field certainly dominated
by men. Her career before even getting to that position was quite an
inspirational journey, at first she wanted to do her degree in astronomy and
for her Bachelor of Science degree most schools wouldn't accept her but finally
she got into an all-girls school and graduated. She was the only one from her
class who graduated with a degree in astronomy. And then she went to Cornell, again
most other universities wouldn't accept her into their program because she was
a woman. So for her to get to where she was required some kind of tenacity, at
age 23 she started pursuing her PhD and she even had her first child while
pursuing her PhD. She had entered astronomy when it was essentially a male-only
activity and encountered resistance throughout her career including a lack of
female bathrooms in the telescopes facility she used, but this didn't stop her
as she undertook meticulous observations of the rotation speeds of spiral
galaxies. This terrific and well-deserved gutsy woman
will be the first woman to have an observatory named after her. On December 20, 2019,
the Large Synoptic Survey Telescope (LSST) was renamed the National Science Foundation
Vera C. Rubin Observatory in recognition of Rubin's contributions to the study
of dark matter and her outspoken advocacy for the equal treatment and representation
of women in science. It has the current most
powerful telescope in the world with the largest (human sized) digital
camera ever built, designed to take continuous 24-hour increment snapshots of
the sky which then can be stitched together to make a movie of the night sky. Hence previously
referred as the ‘Large Synoptic Survey Telescope’ (LSST) which itself evolved from
the earlier concept of the ‘Dark Matter Telescope’. The name honors Rubin and
her colleagues' legacy to probe the nature of dark matter by mapping and cataloging
billions of galaxies through space and time. The observatory will be located on
a mountain in Cerro Pachon, Chile and focus on the study of dark matter and dark
energy. It will also contribute to the study of the structure of the universe
by observing thousands of supernovae, both nearby and at large redshift, and by
measuring the distribution of dark matter through gravitational lensing.
Vera Rubin in the 1970s was looking at Andromeda and the other neighboring
galaxies; she measured the rotation speeds of the stars in those galaxies. When we map the velocity of the planets orbiting the Sun because
the Sun has 99% of all the matter in the system, the mass within any orbit will
be relatively fixed at the sun's mass. Therefore the further away from the
central mass we get the weaker the gravitational pull and the slower the
orbital velocity this model is called Keplerian model because it follows
Kepler's laws for orbital motion. Vera Rubin published a paper in 1978 studying
the rotational velocities of stars in galaxies as a function of their distances
from the galactic center. The expectation was that these galaxies were like the solar
system with most of the mass concentrated towards the center. So closer to the
center of the galaxy you have lots of gravity and the stars should be orbiting
very quickly in order to not fall into the center and just like the planets the speeds of stars
in the spiral disk were expected to fall as gravity gets weaker towards the
edge of the galaxies, but this was not what
Rubin found. Rotational velocities were found to be
nearly constant over a fairly large radial distance, though predictions based
on the distribution of visible matter implied that they would decrease with
distance. The
rotation speed of stars did not diminish but remained roughly the same all the
way to the edge of the galaxies. Just like Zwicky, she was left with a gravitational
puzzle that what was the source of gravity needed to keep the stars moving at
their unexpected speeds. So again to explain that motion you need to invoke some
invisible material that adds an extra gravitational attraction to hold the
stars in the galaxy. Rubin’s discoveries were
interpreted as evidence for the presence of substantial amounts of dark matter
in the haloes around galaxies. And we can use that again to measure how much dark matter there
is in the galaxies as her data was confirmed by radio astronomers, the
discovery of the cosmic microwave background (CMB), and images of gravitational
lensing. About the same time, radio
astronomers, using a spectral line of hydrogen at 21-cm wavelength, obtained a
similar result in the outer parts of galaxies where there is little starlight. Using
accurate and high-resolution emission lines from neutral hydrogen astronomers
modeled the mass distribution of galaxies. They use the mass-to-light ratio in
the visible disc; a galaxy's core radius and the circular velocity of the halo.
The study found the contribution to the rotation curve of three types of matter
gas, luminous matter and dark matter. This new understanding about the
possibility and impact of dark matter, astronomers turn their attention back to
galaxy clusters like the one studied by the Zwicky in 1936. Dark Matter makes
up most of the mass of galaxies when they've looked at the speed and rotation
of galaxies where there should be less Mass on the outside and they should be
slowing down in fact the galaxies were spinning really fast too fast so either
we have missed some fundamental calculations in the universe or there's just
mass invisible to the telescope.
The solar system is located within the Milky Way Galaxy, close
to its equatorial plane and about 8 kiloparsecs from the galactic center. The
galactic diameter is about 30 kiloparsecs, as indicated by luminous matter.
There is evidence, however, for nonluminous matter so called dark matter extending
out nearly twice this distance. The entire system is rotating such that, at the
position of the Sun, the orbital speed is about 220 km per second (almost
500,000 miles per hour). But even at this speed, it takes about roughly 240
million years for the Sun to make one complete trip around the Milky Way. Application
of Kepler’s third law leads to an estimate for the galactic mass of about 100
billion solar masses. The rotational velocity can be measured from the Doppler
shifts observed in the 21-cm emission line of neutral hydrogen and the lines of
millimeter wavelengths from various molecules, especially carbon monoxide. At
great distances from the galactic center, the rotational velocity does not drop
off as expected but rather increases slightly. This behavior appears to require
a much larger galactic mass than can be accounted for by the known (luminous)
matter. Additional evidence for the presence of dark matter comes from a variety
of other observations. The nature and extent of the dark matter (or missing mass)
constitutes one of today’s major astronomical puzzles. We also have evidence of
dark matter from simulations which show how the universe formed in the early
stages. And essentially what scientists find that if we want to show how structure
in the universe formed, we need dark matter. If we don't put dark matter into
your simulations, then we don't get the universe that looks like the one we
live in. So for the simulation that can show the sort of galaxies bursting to
life and new stars turning on, we need the dark matter to make this work, and
to agree with what universe we observe out there in the sky.
One more way of measuring
the dark matter is by looking at something called the Cosmic Microwave Background
(CMB) which is a very faint microwave radiation left over from the big bang, essentially
the point about 380,000 years after the big bang. The universe before that
point was massive super-heated opaque plasma. At 380,000 years it expanded and
cooled down enough, so that plasma condensed into a gas and light, for the
first time could travel freely and that light has been basically travelling through
space ever since which we now detect as CMB radiation. The Cosmic Microwave
Background (CMB) is microwave radiation that fills the all space in the observable
universe and can be detected in every direction. With a standard optical
telescope, the background space between stars and galaxies is almost completely
dark. However, a sufficiently sensitive radio telescope detects a faint
background glow that is almost uniform and is not associated with any star,
galaxy, or other object. This glow is strongest in the microwave region of the
radio spectrum. As microwaves are invisible to the naked eye, we can’t see it
but it is everywhere in the universe and cannot seen without instruments as a
static signal on the screen. Because this pattern is everywhere we look, the
source of this background (CMB) is bath of photons coming uniformly from every
direction in the sky. And by looking at patterns in this radiation across the
whole sky, we can calculate again how much dark matter there is in the universe.
It is a remnant that provides an important source of data on the primordial
universe. Dr. John C. Mather is a senior Astrophysicist in the observational
cosmology laboratory at NASA’s Goddard Space Flight Center. He is also the
Senior Project Scientist on the James Webb Space Telescope. He has received
many awards including the Nobel Prize in Physics, 2006, for his precise
measurements of the cosmic microwave background radiation using the COBE
satellite. In 1978, Nobel Prize for Physics was awarded to American radio
astronomers Arno Penzias and Robert Wilson for detecting the CMB back in 1965.
The accidental discovery of the CMB in 1965 by Penzias and Wilson was the
culmination of work initiated in the 1940s. After couple of decades, John
Mather and George Smoot shared the 2006 Nobel Prize in Physics, the pair were
honored for their “discovery of the blackbody form and anisotropy of the cosmic
microwave background radiation” measured by COBE. Further evidence for dark matter comes from measurements on
cosmological scales of anisotropies in the cosmic microwave background. The distribution of
the anisotropy across the sky has frequency components that can be represented
by a power spectrum displaying a sequence of peaks and valleys. The peak values
of this spectrum hold important information about the physical properties of
the early universe: the first peak determines the overall curvature of the
universe, while the second and third peak detail the density of normal matter
and so-called dark matter, respectively. The
height of the second peak implies that 5% of the total is ordinary atoms, while
matching all the peaks implies that 26% of the total is dark matter. Indeed the
CMB by itself provides irrefutable evidence for dark matter. So all of these three
methods gives us answers about the existence of ‘dark matter’ in the universe.
Euclid space telescope was successfully launched on 1st July
2023, beginning its mission to study dark energy and dark matter in the universe.
It is a fully European mission, built and operated by ESA, with contributions
from NASA. Euclid is designed to explore the evolution of the dark Universe; it
will take images in optical and near-infrared light. The telescope will create
the largest-ever 3D-map of the Universe (with time as the third dimension) by
observing billions of galaxies out to a distance of 10 billion light-years away,
across more than a third of the extragalactic sky outside the Milky Way. Mapping
the extragalactic sky over six years will provide unprecedented data to give
new insight on the nature of dark energy and dark matter, helping scientists
unravel the mysteries of the 'Dark Universe.' Euclid’s image quality will be at
least four times sharper than that achieved by ground-based sky surveys. Textbooks
and popular accounts universally claim that Einstein was the first to equate the geometry of a flexible
spacetime (placed on the left side of his field equations) with the matter
affecting that geometry (placed on the right), demonstrating the revolutionary
idea that mass and geometry are intimately connected. Euclid is named after the Greek mathematician Euclid of Alexandria,
who lived around 300 BC and founded the subject of geometry. As the density of
matter and energy is linked to the geometry of the universe, the mission was
named in his honor. A whole host of experiments are underway with many more planned
for the immense telescopes that are currently making their way from drawing
board to reality. In Chile, the 8.4 meter telescope at the Vera Rubin observatory
will turn its eye to the sky in 2024. So if we
get more and more galaxies then we get a more and more accurate map of where
that dark matter is and what it looks like. One of the scientific goal of the
upcoming Vera Rubin Observatory is to study the dark energy and dark matter by
measuring weak gravitational lensing, baryon acoustic oscillations, and
photometry of type Ia supernovae, all as a function of redshift. Similarly, the
objective of the Euclid, visible to near-infrared space telescope is to better
understand dark energy and dark matter by accurately measuring the acceleration
of the universe. Euclid is a cosmology survey mission, optimized to determine
the properties of dark energy and dark matter on universal scales. When we see
today the structure of the universe as we know it, that has all sorts of galaxies
populating this cosmic web of structure and this diffuse light that's out there
today came from all sorts of interactions happened during the early history of
the evolution of galaxies. While dark energy accelerates the expansion of the
Universe and dark matter governs the growth of cosmic structures, scientists
remain unsure about what dark energy and dark matter actually are. By observing
the Universe evolving over the past 10 billion years, Euclid will reveal how it
has expanded and how structure has formed over cosmic history – and from this,
astronomers can infer the properties of dark energy, dark matter and gravity,
to reveal more about their precise nature. The key goals of these and other telescopes is
to uncover the mysteries of dark matter and dark energy which includes
searching for the signs that dark energy might not be exactly Einstein's
cosmological constant perhaps dark energy has evolved and changed over the
billions of years of the universe maybe it has decayed into matter and radiation.
These would provide new clues to the true nature of dark energy and open new
avenues of research to unravel its physics. However as of today all
observations suggest that dark energy appears to be precisely Einstein's
cosmological constant unchanging over the life of the universe, but this sends
a shiver down the spine of cosmologists as it might mean that the cosmological
constant is uncrackable. The nature of dark matter and dark energy represents a
failure of the fundamental laws of physics. European
space agency has launched its Euclid telescope on a mission to produce an
enormous 3D map of the cosmos designed specifically to give us important new
insights into the "dark side" of the universe -- namely dark matter
and dark energy.
The dark sector could potentially host its own physics as rich
as those in the atomic world, but with the limited observational evidence we
are again stuck in the world of theory and clearly more observations and measurements
are required. Whilst astronomers were gazing skyward, particle physicists were
hunting for dark matter in the world of the subatomic realm. Through the course
of the 20th century, they had unraveled the fundamental nature of matter
finding the particles from which mass and forces are constructed, comprised of
quarks and leptons, photons and gluons as well as the more esoteric w and z
bosons. This zoo of particles was rounded off in 2012 with the discovery of the
Higgs boson. This standard model of particle physics has proved to be a great
success, it accurately accounts for the tumult of particles pouring out of the
immense collisions at the large hadron collider and other particle physics
experiments. Scientist believes that Standard Model
is definitely on to something as you don't get this kind of result by accident.
Despite this we know it
must be incomplete as it can account for the strong and weak nuclear forces and
electromagnetism but gravity is still resisting from being added to the quantum
world. So it’s a really stunningly successful theory, but it is not
without some problems. And these problems are actually what motivated, in part,
the building of the Large Hadron Collider in the first place. There are at least
two key components of our cosmos that are missing from the standard model of
particle physics. Scientists aim to find
out more about two of the universe's greatest mysteries: dark energy and dark
matter, researchers know virtually nothing about these phenomena which appear
to make up the vast majority of the universe. The
discovery of the Higgs which is really kind of closing the chapter of 20th
century physics and the beginning of the next era in fundamental physics paving
the way to new physics. What everyone now actually is after the answers to some
big, unsolved questions that the Standard Model cannot address. The cosmic pie
depicts that ordinary matter of which made all the galaxies, and stars, and
planets in the universe; everything that Standard Model describes is just 5% of
the total content of the universe. And more than five times of the known
universe that we are made of; is the invisible dark matter stuff which is 27%
of that cosmic pie. There is something even more mysterious called dark energy
that’s makes up around 68% of cosmic pie, repulsive force that appears to be
accelerating the expansion of the universe. That's pretty big of what's out
there, so that is definitely a bit of an omission in the Standard Model. The large
hadron collider at CERN had remained shut for three years as scientists worked
on upgrading the facility for higher proton collisions than in 2012 when the
God Particle was discovered, the detectors, electronics, and computing have all
gone through substantial upgrades. Scientists are not done, Large Hadron
Collider was not built to just find the Higgs boson; it was built to find new
particles. LHC was shut down for maintenance purpose just before the start of
Run 3, they tightened the screws once again as they are going to lift it up to
a much higher energy. The changes will allow them to collect significantly
larger data samples, of higher quality than previous runs. The restart
marked the beginning of preparations for the third run of the LHC, called Run
3, which planed four years of physics-data taking at world-record collision
energy of 13.6 trillion electronvolts (13.6 TeV). LHC Run 3 was started on 5
July, the day after the 10th anniversary of the discovery of the Higgs boson. There
are also theoretical hints that the new physics should be found at accessible
energy scales. Much of the efforts to find this new physics are focused on new
collider experiments. LHC Run 3 with the increased data samples and higher
collision energy expanded further the already very diverse LHC physics
programme and now scientists at the LHC experiments will be searching for
candidates for dark matter and for other new physics phenomena, either through
direct searches or – indirectly – through precise measurements of properties of
known particles and these more powerful collisions will allow us to explore
further the particle world, and we will certainly learn much more.
The discovery of the Higgs was such a big deal and now that we
have found it, we can move beyond everyday physics, there are dark matter, dark
energy and black holes out there in the universe. Particle Physicists are hopeful
that the Higgs boson will not simply be the end of one story, but the beginning
of the next era in fundamental physics. So the next question: Is there any boson for
gravity? And basically if there is no boson for gravity, how could we explain
it? It is hypothesized that gravitational interactions are mediated
by an as yet undiscovered elementary particle, dubbed the graviton. In theories of quantum gravity, the graviton is the hypothetical
quantum of gravity, an elementary particle that mediates the force of
gravitational interaction. There is no complete quantum field theory of
gravitons due to an outstanding mathematical problem with renormalization in general
relativity.
If it exists, the graviton is expected to be massless because
the gravitational force has a very long range, and appears to propagate at the
speed of light. General relativity did give scientists a nice starting point. According
to general relativity's explanation of the distribution of the mass and energy
in the universe, if there is a graviton it's a massless particle with the spin
of two; scientists from Fermilab and CERN are looking for this particle with
eager eyes. Assuming
that they do exist, it would be a bit unlike the other particles. The problem
with gravitons is that gravity is so weak; while
gravitons offer a nice explanation of
gravity, we are yet to discover their existence. So what exactly is it about graviton
that makes it so hard to discover? You see gravity contrary to what many people
believe is one of the weakest forces to exist. If we go down to particle level, we have got
these incredibly strong forces of nature that are
mediated by elementary particles like the electromagnetic force by the photon, the strong nuclear force by gluons, the weak force by the W and Z bosons and they totally overwhelm gravity; in fact the bonds holding together a hydrogen atom are stronger. To prove this just think how easily we can pick up an apple
despite the entire earth exerting a gravitational pull on it. From a quantum
mechanical view the reason for gravity's lack of strength is due to the fact
that gravitons interact very weakly, so as a result detecting a graviton would
be very difficult. It’s quite difficult to actually measure their effect, so if you
are trying to do some experiment to measure gravitational attraction between
two particles then that attraction is so tiny that it's basically impossible to
measure in an experiment at the moment. The
cosmic pie depicts that ordinary baryonic matter, including everything made of
atoms from the periodic table of which made all the galaxies, and stars, and
planets in the universe; everything that Standard Model describes is just 5% of
the total content of the universe. And more than five times of the known
universe that we are made of; is the invisible dark matter stuff which is 27%
of that cosmic pie, the matter that interacts with gravity but not light. And if you really want
to find the evidence of gravitons then you have to build a gigantic particle
accelerator that the size of the Milky Way galaxy. So scientists don’t have any
firm evidence for their existence, but still they think that gravitons are out
there.
People: What is dark matter?
Scientists: ¯\_(ツ)_/¯
It’s not the thing that bothers what came first; chicken or eggs?
But the biggest curiosity quest is dark matter with the boson
Higgs.
It’s kind of assumed that at the moment, they are impossible to
detect directly but some of these extra dimensional theories contain massive
gravitons in them. And those are things that could be observe in a collider, so
if some of these extra dimensions of space ideas are right then there could be
gravitons that can be detectable by the LHC. So
far we know that 95% of the universe is dark it doesn't shine. We have
constructed what seems to be this stunningly successful theory over a century
with all these clever experiments backing it up. But then we realize that what
we've been describing is actually only a tiny fraction of the total content of
the universe. And as having a theory that works really well in the very narrow
domain in which we've applied it, but tells us basically nothing about major content
of the universe. In the physics community, until we find and confirm the existence
of gravitons they just remain theory explanation of our universe. So the lesson
from this is essentially that the word “dark” in physics means we don't know
what we're talking about and that scientists themselves get very suspicious
because it as we cannot see it with our telescopes. Although dark matter does
not interact with light, it interacts with gravity. So we observe it through its
influence on other things using methodology called weak gravitational lensing
where the shapes of distant galaxies gets distorted as the light from them
comes to us by passing through the Dark Matter in between. Today many physicists
continue to study the dark matter, using data from various telescopes and also
Geneva where the Large Hadron Collider lurks underground, improving our
understanding of particle physics.
↓↓↓↓Poetic Piece↓↓↓↓
http://sukalyogesh.blogspot.com/2023/06/cern-concern.html
