Kurzgesagt – In a Nutshell
Sources – Jiggle of Existence
We thank the following experts for their help with this script:
Dr. Matthew Caplan
Illinois State University
Dr. Alexander Ji
Department of Astronomy and Astrophysics, University of Chicago
Dr. Denis Erkal
Astrophysics Research Group, University of Surrey
Jiggle of Existence – Sources
– Somewhere in a room, maybe in a city on a continent on a planet orbiting a star in a galaxy among billions.
Current estimates suggest that there are as many as two trillion galaxies in the Universe.
#Hubble Reveals Observable Universe Contains 10 Times More Galaxies Than Previously Thought, NASA, 2016
Quote: “One of the most fundamental questions in astronomy is that of just how many galaxies the universe contains. The landmark Hubble Deep Field, taken in the mid-1990s, gave the first real insight into the universe's galaxy population. Subsequent sensitive observations such as Hubble's Ultra Deep Field revealed a myriad of faint galaxies. This led to an estimate that the observable universe contained about 200 billion galaxies. The new research shows that this estimate is at least 10 times too low.”
– Let us start this video at a familiar place and then get increasingly weird. From your perspective the world is seemingly flat and you can move in 3 dimensions. It's what physicists call a `frame of reference`– the perspective you have of the universe and how you see things moving around you. Where your up and down is. Your frame of reference is correct. For you – but not for the rest of the universe.
We are using the term “frame of reference” in the physical sense here rather than the mathematical definition; but have taken the liberty to move pretty freely betwee coordinate systems and reference frames throughout the video for the sake of simplification.
#Space and Time: Inertial Frames, 2020
https://plato.stanford.edu/entries/spacetime-iframes/
Quote: “A “frame of reference” is a standard relative to which motion and rest may be measured; any set of points or objects that are at rest relative to one another enables us, in principle, to describe the relative motions of bodies. A frame of reference is therefore a purely kinematical device, for the geometrical description of motion without regard to the masses or forces involved.”
– Around 5 kilometers from you, where the horizon begins, the ground noticeably curves away from you.
5 km refers to the average distance to the horizon. It is the furthest one can see before the curvature of the Earth impacts the view. All possible confounders excluded, it can be calculated through the Pythagorean Theorem in the most simple way. As illustrated in the image below, the distance depends on one’s height or elevation. If we take an average human height of 160cm (H in the formula) and plug this in together with the average radius of the Earth, 6371 km (R in the formula), into the formula below, we end up with D = 4515 m which we rounded up to 5 km. In comparison, if one was to stand at the top of Mount Everest, which is approx. 8.5 km tall, the distance to the horizon would be about 330 km instead.
#Q&A: Distance to the Horizon, 2017
https://sky-lights.org/2017/07/24/qa-distance-to-the-horizon/
This simple calculation neglects the effect of the atmospheric refraction which bends the light and curves the light path downwards which would make us see further away. The following image illustrates this effect by comparing the conditions with and without refraction.
#RASC Calgary Centre, The Horizon, 2014
– But for humans there is an up and down because within our frame of reference that just makes sense. Which is also why we think that the planet itself has an up and down, north and south. And we made our maps accordingly. But an observer looking at the solar system might disagree. Our maps make sense to us because we are used to them, not because they are correct.
In astronomy, this axial tilt is also known as obliquity, i.e. it is the angle between the Earth’s – or any object's so to say– rotational (i.e. its own movement) and orbital (i.e. its movement around another object) axes.
#The Sun and Stars in the Celestial Sphere
https://w.astro.berkeley.edu/~basri/astro10-03/lectures/CelestialSphere.htm
Even though it starts messing around with our perspective, we have seasons thanks to obliquity: As the Earth revolves around the sun, the hemisphere that’s tilted towards the sun receives more sunlight, causing it to be summer season in that hemisphere.
Also, this angle is not fixed at 23.5 degrees; it goes through between 22.1 and 24.5 degrees on a cycle of around 40,000 years. So, about 10,700 years ago, it was at its maximum tilt, 24.5 degrees, and about 9,800 years from now it will reach its minimum tilt, 22.1 degrees. A smaller angle causes milder seasons, cooler summers and warmer winters, since the distance between the earth and the sun gets a little longer.
#The Earth Observatory, Orbital Variations, 2000
https://earthobservatory.nasa.gov/features/Milankovitch/milankovitch_2.php
Quote: “As the axial tilt increases, the seasonal contrast increases so that winters are colder and summers are warmer in both hemispheres. Today, the Earth's axis is tilted 23.5 degrees from the plane of its orbit around the sun. But this tilt changes. During a cycle that averages about 40,000 years, the tilt of the axis varies between 22.1 and 24.5 degrees. Because this tilt changes, the seasons as we know them can become exaggerated. More tilt means more severe seasons—warmer summers and colder winters; less tilt means less severe seasons—cooler summers and milder winters. It's the cool summers that are thought to allow snow and ice to last from year-to-year in high latitudes, eventually building up into massive ice sheets. There are positive feedbacks in the climate system as well, because an Earth covered with more snow reflects more of the sun's energy into space, causing additional cooling.”
– First of all, our orbit really is an ellipse, so we spend half the year sinking a little bit closer to the sun speeding up, and half the year rising up a bit and slowing down. And the ellipsis itself changes its shape every 100,000 years too.
Earth goes about an elliptical trajectory during its yearly travel around the Sun. The closest point is called perihelion and the furthest is called aphelion. Sometime around January 3 every year, we pass through Perihelion, and around July 4 through Aphelion. The difference between the two distances is currently about 5.1 million kilometers. Apart from making our frame of reference more confusing, this shape also causes the seasons to differ in length slightly: Summers are around 5 days longer than the winters in the Northern Hemisphere due to this departure of the orbit from the perfect circularity.
#Przystupa, Krzysztof, Selected aspects of electricity generation in a private photovoltaic installation. 2019
#Steve C. Rockport, Planetarium, retrieved 18.01.2022
Quote: “We should begin by explaining that Earth's orbit is not perfectly circular. If it were, Earth's distance from the Sun would never change. However, it is a slightly elongated ellipse, so its distance varies continuously throughout the year. Its distance veers from its minimum distance (perihelion), which it reaches in early January, to aphelion, which it reaches in early July. It is logical to assume that Earth would necessarily be hotter at perihelion than aphelion. However, the difference in the amount of the Sun's energy we receive (called the solar constant) doesn't vary considerably between perihelion and aphelion. After all, the distance difference between perihelion and aphelion is only about three million miles,* a small fraction of Earth's average 93 million mile heliocentric distance.”
The deviation from the perfect circularity is measured by eccentricity. For an elliptical orbit like in the following figure, the semimajor axis (the length a) is the longest radius of the ellipse. Perihelion is the closest point of a celestial body’s orbit, in this case Earth’s, around the Sun. Eccentricity (e) is the ratio of the difference between the semimajor axis (a) and perihelion distance (dp) to the semimajor axis itself: e = (a -dp)/a. For a perfect circle, e would be 0; whereas for an ellipse 0<e<1. Earth’s orbit has an eccentricity of 0.0167, almost a circle.
# J. Giesen, Eccentricity of the orbit of the Earth from 1,000,000 BC to 1,000,000 AD, 2019.
NASA provides these numbers:
#Earth Fact Sheet, NASA, 2021
https://nssdc.gsfc.nasa.gov/planetary/factsheet/earthfact.html
And since the speed of the Earth increases with the decreasing distance to the Sun, at the Perihelion, we are at our fastest. When we plug the numbers in the following formula, we can calculate the speed. The universal gravitational constant, G = 6.673x10^(-11) N∙m2/kg2, mass of Earth ~ 5.98 x 10^24 kg.
#Orbital Velocity Formula
https://www.softschools.com/formulas/physics/orbital_velocity_formula/76/
Therefore, we are now moving about 30.3 km/sec at the Perihelion, 1 km/sec faster than when Earth is farthest from the sun in early July at the Aphelion.
What’s more, this value is also not set in stone. As the Earth moves about the solar neighborhood, its orbit gets stretched over time by the gravitational effects of the other hefty residents of the solar system like Saturn and Jupiter. Orbital shape goes between an almost circular to slightly elliptical over a 100,000 year period, as illustrated in the graph below:
# J. Giesen, Eccentricity of the orbit of the Earth from 1,000,000 BC to 1,000,000 AD, 2019.
– And in another cycle of 112,000 years, the ellipse itself is drifting – which at least creates a beautiful shape. In the end, we get an orbital path that looks like a wobbly circle with wavy edges.
Until now we mentioned two of the three dominant periodic motions of the orbital features: Eccentricity and Obliquity. Third movement is the Precession. There are two types of precession: Apsidal Precession, that refers to the movement of the apsides of the Earth’s orbit around the Sun and, Axial precession, that refers to the wobbling of Earth upon its own axis. Apsidal Precession refers to a motion similar to the following pattern:
#Planet's perihelion precession
All planets in the Solar system exhibit Apsidal Precession. Smaller gravitational forces of the planets on each other cause the major axes of the planets to slowly rotate about the Sun, shifting the line from the Sun to the perihelion to a certain angle (depicted with greek letter phi in the following image) each orbit. The cycle of apsidal precession of Earth is around 112,000 years.
#Perihelion of Mercury’s Orbit, Paul A. Tipler; Gene Mosca, Physics for Scientists and Engineers, Sixth Edition, 2020.
The following animation, on the other hand, shows the Axial Precession – precession of Earth's axis over its cycle of 26,000 years:
#Basics of Space Flight, NASA Science/Solar System Exploration, retrieved 19 Jan 2022
All these orbital movements are collectively known as Milankovitch Cycles:
#Alan Buis, Milankovitch (Orbital) Cycles and Their Role in Earth's Climate, NASA's Jet Propulsion Laboratory, 2020
https://climate.nasa.gov/news/2948/milankovitch-orbital-cycles-and-their-role-in-earths-climate/
Quote: “Specifically, he examined how variations in three types of Earth orbital movements affect how much solar radiation (known as insolation) reaches the top of Earth’s atmosphere as well as where the insolation reaches. These cyclical orbital movements, which became known as the Milankovitch cycles, cause variations of up to 25 percent in the amount of incoming insolation at Earth’s mid-latitudes (the areas of our planet located between about 30 and 60 degrees north and south of the equator). The Milankovitch cycles include:
1.The shape of Earth’s orbit, known as eccentricity;
2.The angle Earth’s axis is tilted with respect to Earth’s orbital plane, known as obliquity; and
3.The direction Earth’s axis of rotation is pointed, known as precession.”
As a recap, all three cycles are separately looking like in the following gif:
#Caroline Catherman, Medill Reports, 2020
https://news.medill.northwestern.edu/chicago/milankovitch-theory-flaw-climate-change-new-study/
– And it gets worse, as the moon now starts to screw things up too. As the moon is a pretty massive thing, it pulls on earth. Both objects orbit their common center of gravity, that lies around 4700 km off to the side of Earth’s core. In practice this means that as the moon orbits earth, it is jerking earth around a bit, enough to make it jiggle.
Yes, the common misconception is that the Moon orbits around the exact center of mass of the Earth. In reality, however, there is little more to what it seems like. In space, two bodies (or more in case of systems) actually orbit each other around their common center of mass. This point is called the Barycenter.
#ESA, Barycentric balls Figure A1, 2015
https://www.esa.int/ESA_Multimedia/Images/2015/05/P07_Barycentric_balls_Figure_A1
Barycenter can be computed by multiplying the distance between the objects by their mass ratio. In the case of the Moon-Earth duo, their distance (which is 384,400 km) multiplied by their mass ratio (which is around 0.0123) gives 4728 km, so around 4700 km. And yes, this is smaller than the Earth’s radius! Since the Earth is massive in comparison to the Moon, the barycenter of the two is inside the Earth – about 1600 km below your feet.
One can read the Earth/Moon mass ratio and the distance (semi-major axis) from NASA’s Factsheets:
#Moon Fact Sheet, NASA
https://nssdc.gsfc.nasa.gov/planetary/factsheet/moonfact.html
This is the point not only the Moon revolves around, but the Earth does so as well – in a way smaller orbit of course, a wobble in comparison to Moon’s movement. The timescale for one wobble is the same as the orbital period of the Moon, 27 days and its relative velocity is 0.01 km/s, which is 3000 times smaller than the orbital velocity of the Earth around the Sun.
Following image shows this wobbling highly exaggerated:
#Laetitia Rodet, How much does the Earth "wobble" in its orbit due to the Moon's gravity?, 2021
– But who's to say the earth is right? From the perspective of the sun the plane of the solar system is arbitrary, it's defined as the plane the earth orbits in because that is convenient for us. In reality the other planets are just a little bit inclined with respect to our plane. From their point of view, we're the ones with a slightly bent orbit.
Planets are moving around the Sun more or less on the same plane – the ecliptic plane. Each planet deviates a few degrees from it which is quantified with the Orbital Inclination in the following table. The ecliptic plane is defined as the plane containing the Earth's orbit, so the Earth's inclination is 0.
#Planetary Fact Sheet - Metric, retrieved 19 Jan 2022
So they would look like as in the following diagram (blue lines projects to the closeup version of the inner planets):
#Ecliptic, Retrieved 19 Jan 2022
– But this is not it – far from it! The solar system as a whole is orbiting the center of the milky way galaxy. If we look at the milky way, we can clearly make out a galactic plane in which the solar system orbits the center every 230 million years. But of course it is not that simple. First of all, the plane of the solar system is not aligned with the plane of the galaxy. Nothing really is – just like the planets in the solar system orbit the sun on their own planes, so do all the stars orbiting the galactic center. The solar system as a whole is tilted about 60 degrees towards the galactic plane, speeding through space at almost a million kilometers per hour.
The Sun is currently about 27,000 light years away from the center of the galaxy – on one of its minor spiral arms Orion. And the ecliptic plane makes a 60 degree angle with the galactic plane. So we can imagine it as in the following images:
#Alison Klesman, (Senior Associate Editor, Astronomy magazine) In which direction does the Sun move through the Milky Way?, 2020.
#Motion of Sun, Earth and Moon around the Milky Way, Wikimedia Commons, 2017
https://commons.wikimedia.org/wiki/File:Motion_of_Sun,_Earth_and_Moon_around_the_Milky_Way.jpg
It takes around 230 million years for the Sun to complete a trip around our galaxy – a galactic year so to say. So we are in the 20th galactic year currently. And the sun’s average speed during this trip is about 828,000 km/hr.
#Beyond Our Solar System, NASA Science/Solar System Exploration, 2019
https://solarsystem.nasa.gov/solar-system/beyond/in-depth/
Quote: “All of the stars in the Milky Way orbit a supermassive black hole at the galaxy's center, which is estimated to be some four million times as massive as our Sun. Fortunately, it is a safe distance of around 28,000 light years away from Earth. The Milky Way zips along a galactic orbit at an average speed of about 514,000 mph (828,000 km/hr). It takes about 230 million years for our solar system to make one revolution around the galactic center.”
Our Sun is far from being the only celestial object moving about the Milky Way. There are billions of stars in the galaxy each moving about their own orbital planes and have no problems with not being aligned to each other. The group of S-stars, for instance, which are moving nearby the black hole in the center of our galaxy Sagittarius A*, have orbital periods ranging from a few years to a few thousand years. S0-2, whose orbit is depicted with the yellow circle in the following animation, has been observed throughout its full orbit, around 15 years. It is 17 light hours away when it is closest to the black hole.
#Stellar Orbits in the Central Parsec, UCLA Galactic Center Group
Following animation shows the orbits in 3D:
# 3D Movie of Stellar Orbits in the Central Parsec, UCLA Galactic Center Group
#ESA, GAIA'S stellar motion for the next 1.6 million years, 2020
https://sci.esa.int/web/gaia/-/gaia-s-stellar-motion-for-the-next-1.6-million-years
Quote: “The stars are in constant motion. To the human eye this movement, known as proper motion, is imperceptible but Gaia is measuring it with more and more precision. The trails on this image show how 40 000 stars, all located within 100 parsecs (326 light years) of the Solar System, will move across the sky in the next 400 thousand years. These proper motions are released as part of the Gaia Early Data Release 3 (Gaia EDR3). They are twice as precise as the proper motions released in the previous Gaia DR2. The increase in precision is because Gaia has now measured the stars more times and over a longer interval of time. This represents a major improvement in Gaia EDR3 with respect to Gaia DR2.”
– Someone in the center of the galaxy would see the orbits of the planets moving through space in a helix shape, which you can imagine as a corkscrew motion, on the tilted plane of the solar system, relative to the plane of the galaxy. This orientation in space means that sometimes the planets are sort of in front of the sun as it orbits around the galactic core.
#Ethan Siegel, Earth Is Drifting Away From The Sun, And So Are All The Planets, 2019
# The Solar System Is Not A Vortex, But It Might As Well Be, retrieved 19 Jan 2022
– This is still not the whole story because the mass of the galactic disk is constantly pulling on the solar system too. Like a drunk dolphin, we're diving down and shooting up hundreds of lightyears through the galactic plane, ten times every orbit, along arcs thousands of light years long. We haven’t mapped this motion out completely, as it takes the solar system tens of millions of years to go up and back once; and, well, humanity is not that old.
As it goes around the galactic core, the Sun does not stay on the same plane. Due to the gravitational effects of surrounding stars, gas and dust, it oscillates vertically with a period of around 60 million years. We are currently above the galactic plane, at around 70 million light years, though there are varying estimates
And we don't even know for how long more our Sun will follow this path. Other parts of the galaxy, like spiral arms and the galactic bar may push the Sun's orbit around and cause the orbital distances to change.
Murchikova, E.M. et al. A cool accretion disk around the Galactic Centre black hole, 2019.
–The Milky way is part of a galaxy group that appears to be part of greater structures like the Laniakea Supercluster, which itself is part of the gigantic Pisces–Cetus Supercluster Complex and finally a galactic filament that spans hundreds of millions of lightyears in all directions and orientations.
The Milky Way and Andromeda are the two large galaxies in our Local Group. The third biggest one is the Triangulum Galaxy (aka Messier 33) which is suspected to be a gravitationally bound companion to the Andromeda Galaxy. Accompanying these, there are almost 100 dwarf galaxies residing in the Local Group. Each pulling and pushing each other around, affecting each other's movement that causes a seemingly chaotic stellar dance. The Milky Way and Andromeda, for instance, are drawn to each other because of the gravitational forces. So the Milky Way is moving towards Andromeda at 400,000 km per hour. Given that they are 2.5 million lightyears apart, they still have some 4 billion years or so until they collide with each other head to head and become one.
#Messier 33 (The Triangulum Galaxy), NASA Hubble’s Messier Catalog, 2019
https://www.nasa.gov/feature/goddard/2019/messier-33-the-triangulum-galaxy
Quote: “Spiral galaxy M33 is located in the triangle-shaped constellation Triangulum, earning it the nickname the Triangulum galaxy. About half the size of our Milky Way galaxy, M33 is the third-largest member of our Local Group of galaxies following the Andromeda galaxy (M31) and the Milky Way. Comprised of 54 separate Hubble fields of view, this image is the largest high-resolution mosaic of M33 assembled to date by any observatory. It resolves 25 million individual stars in a 14,000-light-year-wide region spanning the center of the galaxy.”
#Hubble Shows Us the Future, NASA Solar System and Beyond, 2021
https://www.nasa.gov/image-feature/hubble-shows-us-the-future
Quote: “Hubble went on to discover the expanding universe where galaxies are rushing away from us, but it has long been known that M31 is moving toward the Milky Way at about 250,000 miles per hour. That is fast enough to travel from here to the moon in one hour. ”
Moreover, scientists have recently discovered that the whole Milky Way galaxy is moving even ignoring nearby galaxies like Andromeda. Our galactic neighbor, the Large Magellanic Cloud (LMC), is pulling the Milky Way out of its place. It is one of a few dozen satellite galaxies of the Milky Way. The force of the dark matter halo of the Large Magellanic Cloud is pulling the Milky Way’s galactic disc at 32 km per second.
#Michael S. Petersen and Jorge Peñarrubia. Detection of the Milky Way reflex motion due to the Large Magellanic Cloud infall. 2021
https://www.nature.com/articles/s41550-020-01254-3
Quote: “The Large Magellanic Cloud is the most massive satellite galaxy of the Milky Way, with an estimated mass exceeding a tenth of the mass of the Milky Way1–5. Just past its closest approach of about 50 kpc, and flying past the Milky Way at an astonishing speed of 327 km s−1 (ref. 6), the Large Magellanic Cloud can affect our Galaxy in a number of ways, including dislodging the Milky Way disk from the Galactic centre of mass7– 9 . Here, we report evidence that the Milky Way disk is moving with respect to stellar tracers in the outer halo in a direction that points at an earlier location on the Large Magellanic Cloud trajectory.”
The following two papers identified the motion of LMC and Milky Way:
#Erkal D. et al., The total mass of the Large Magellanic Cloud from its perturbation on the Orphan stream, 2019.
https://arxiv.org/pdf/1812.08192.pdf
#Eugene Vasiliev, Vasily Belokurov, Denis Erkal. Tango for three: Sagittarius, LMC, and the Milky Way, 2020
Here is the video showing the motion of the Sun, Milky Way and Large Magellanic Cloud based on the data published with the above paper:
https://www.youtube.com/watch?v=WW-ps2zg89s
The Sun is shown as the yellow star in the video and the Milky Way as the red cross. It is difficult to do so but try to ignore at first the surge of pink color brushing around the scene – it represents the stars in Sagittarius and the surrounding dark matter, and the dotted blue line tracks the past orbit of the Sagittarius dwarf. So the Sun is orbiting around the Milky Way's center. The red line tracks the position of the Milky Way over time. The big green dot entering the scene around 14 seconds in is the Large Magellanic Cloud. So as LMC comes in, one can see that the Milky Way is pulled in by a huge amount!
But all these galaxies are not randomly scattered across the universe; rather they are found in groups, like our own Local Group with its dozens of galaxies and also in bigger clusters with hundreds– all interconnected in a web of filaments dotted by galaxies. At the intersections of these filaments, we find huge structures, called “superclusters.” The Milky Way is located on the outskirts of one such supercluster: Laniakea Supercluster. It is 500 million light-years in diameter and contains the mass of a hundred quadrillion suns in 100,000 galaxies.
#Tully et al, The Laniakea supercluster of galaxies, 2014
https://arxiv.org/pdf/1409.0880.pdf
Quote: “The particular interest with the present discussion is with the largest structure that can be circumscribed with the presently available distance and peculiar velocity data. This is the structure schematically illustrated in Figures 1 and 2. The region includes 13 Abell clusters (with the Virgo Cluster). Local flows within the region converge toward the Norma and Centaurus clusters in good approximation to the location of what has been called the ‘Great Attractor’17. This volume includes the historical Local and Southern superclusters18, the important Pavo-Indus filament, an extension to the Ophiuchus Cluster, the Local Void, and the Sculptor and other bounding voids. This region of inflow toward a local basin of attraction can be reasonably called a supercluster. The region, if approximated as round, has a diameter 12,000 km s−1 or 160 Mpc and encompasses ~1×1017M⊙. The region deserves a name. In the Hawaiian language “lani” means “heaven” and “akea” means “spacious, immeasurable”. We propose that we live in the Laniakea Supercluster of galaxies.”
Laniakea is part of a yet bigger structure: Pisces-Cetus Supercluster Complex.
Following image shows the two major supercluster complexes in the south galactic hemisphere Pisces-Cetus and Aquarius with their substructures. Within the region marked as Virgo-Hydra-Centaurus Supercluster, Centaurus is located at the center of the Laniakea basin of attraction whereas Virgo and Local Group are at its periphery.
#R. Brent Tully, More about clustering on a scale of 0.1 c, 1987.
https://articles.adsabs.harvard.edu/pdf/1987ApJ...323....1T
Quote: “The Pisces-Cetus Supercluster Complex is separated into five parts: (i) the Pisces- Cetus Supercluster, (ii) the Perseus-Pegasus chain, (iii) the Pegasus-Pisces chain, (iv) the Sculptor region, and (v) the Virgo-Hydra-Centaurus Supercluster.”
The largest of these filaments known to us is the Hercules–Corona Borealis Great Wall – an astonishing 10 billion light years long and contains several billion galaxies. It is the largest
#Horvath et al, The largest structure of the Universe, defined by Gamma-Ray Bursts, 2013
https://arxiv.org/pdf/1311.1104.pdf
Quote: “Research over the past three decades has revolutionized the field of cosmology while supporting the standard cosmological model. However, the cosmological principle of Universal homogeneity and isotropy has always been in question, since structures as large as the survey size have always been found as the survey size has increased. Until now, the largest known structure in our Universe is the Sloan Great Wall (SGW), which is more than 400 Mpc long and located approximately one billion light-years away. Here we report the discovery of a structure at least six times larger than the Sloan Great Wall that is suggested by the distribution of gamma-ray bursts (GRBs). Gamma-ray bursts are the most energetic explosions in the Universe.”
#Wang et al, Possible observational evidence for cosmic filament spin, 2021
https://www.nature.com/articles/s41550-021-01380-6.pdf
Quote: “Although structures in the Universe form on a wide variety of scales, from small dwarf galaxies to large super clusters, the generation of angular momentum across these scales is poorly understood. Here we investigate the possibility that filaments of galaxies—cylindrical tendrils of matter hundreds of millions of light years across—are themselves spinning. By stacking thousands of filaments together and examining the velocity of galaxies perpendicular to the filament’s axis (via their redshift and blueshift), we find that these objects too display vortical motion consistent with rotation, making them the largest objects known to have angular momentum. The strength of the rotation signal is directly dependent on the viewing angle and the dynamical state of the filament. Filament rotation is more clearly detected when viewed edge-on. In addition, the more massive the haloes that sit at either end of the filaments, the more rotation is detected. These results signify that angular momentum can be generated on unexpectedly large scales.”
– Someone looking right at us from that far away will only see the End of Greatness. All stuff appears homogeneous, the same everywhere. Just like with empty space, when everything looks the same, who's to say anyone's view is better than anyone else's?
All the objects we have mentioned so far are not randomly junked in space. There is somehow a certain structure to the distribution of matter. The paragraph in the following quote summarizes this galactic hierarchy:
#De Marzo et al, Zipf’s law for cosmic structures: how large are the greatest structures in the universe?, 2021
https://arxiv.org/pdf/2105.06110.pdf
Quote: “The fractal behavior of visible matter in the universe corresponds to the fact that galaxies are distributed in a hierarchical manner: they form small groups, that, in turn, aggregate into clusters of galaxies and then, going on, clusters are grouped into larger structures, i.e., superclusters and filaments (De Vaucouleurs 1953; Abell et al. 1989), which are the largest known structures in the universe. Superclusters are linked by these filaments of galaxies and clusters forming the so called cosmic web (Bond et al. 1996) or superclusters-void network (Einasto et al. 1980), corresponding to a complex distribution of matter characterized by large voids and connected over-densities (Tully et al. 2014; Pomarede et al. 2017; Pomar`ede et al. 2020; Colin et al. 2019).”
All this blur makes up the cosmic web. However, beyond some 300 million light years things start to look differently – they start to even out. It doesn't matter where you look or where you are. On the largest scales, the universe has the same physical properties throughout, it is homogeneous. This is also called the Cosmological Principle and it is one of the main assumptions we have about the universe. Harvard astronomer Robert Kirshner was the first to use “End of Greatness” to refer to the sudden appearance of cosmic homogeneity and uniformity as one observes at greater and greater cosmological distances.
#Slime Mold Simulations Used to Map Dark Matter Holding Universe Together, 2020
Quote: “The cosmic web is the large-scale backbone of the cosmos, consisting primarily of the mysterious substance known as dark matter and laced with gas, upon which galaxies are built. Dark matter cannot be seen, but it makes up the bulk of the universe's material. The existence of a web-like structure to the universe was first hinted at in the 1985 Redshift Survey conducted at the Harvard-Smithsonian Center for Astrophysics. Since those studies, the grand scale of this filamentary structure has grown in subsequent sky surveys. The filaments form the boundaries between large voids in the universe.”