R.E. Slater - The Laniakea Supercluster: Our Home in the Heavenly Skies

Scientists have created the first map of a colossal supercluster of galaxies known as Laniakea, the home of Earth's Milky Way galaxy and many other. This computer simulation, a still from a Nature journal video, depicts the giant supercluster, with the Milky Way's location shown as a red dot.| Credit: Nature Video

New Galactic Supercluster Map

Shows Milky Way's 'Heavenly' Home

http://www.space.com/27016-galaxy-supercluster-laniakea-milky-way-home.html#undefined.gbpl

by Charles Q. Choi, Space.com Contributor

September 3, 2014

A new cosmic map is giving scientists an unprecedented look at the boundaries for the giant supercluster that is home to Earth's own Milky Way galaxy and many others. Scientists even have a name for the colossal galactic group: Laniakea, Hawaiian for "immeasurable heaven."

The scientists responsible for the new 3D map suggest that the newfound Laniakea supercluster of galaxies may even be part of a still-larger structure they have not fully defined yet.

"We live in something called 'the cosmic web,' where galaxies are connected in tendrils separated by giant voids," said lead study author Brent Tully, an astronomer at the University of Hawaii at Honolulu.

This computer-generated depiction of the Laniakea Supercluster of galaxies, which includes the Milky Way galaxy containing Earth's solar system, shows a view of the supercluster as seen from the supergalactic equatorial plane. | Credit: SDvision interactive visualization software by DP at CEA/Saclay, France Galactic structures in space

Galaxies are not spread randomly throughout the universe. Instead, they clump in groups, such as the one Earth is in, the Local Group, which contains dozens of galaxies. In turn, these groups are part of massive clusters made up of hundreds of galaxies, all interconnected in a web of filaments in which galaxies are strung like pearls. The colossal structures known as superclusters form at the intersections of filaments.

The giant structures making up the universe often have unclear boundaries. To better define these structures, astronomers examined Cosmicflows-2, the largest-ever catalog of the motions of galaxies, reasoning that each galaxy belongs to the structure whose gravity is making it flow toward.

"We have a new way of defining large-scale structures from the velocities of galaxies rather than just looking at their distribution in the sky," Tully said.

Two views of the Laniakea Supercluster, a massive collection of galaxies that contains Earth's Milky Way galaxy and many others, are shown in these computer-generated images. | Credit: SDvision interactive visualization software by DP at CEA/Saclay, France

Laniakea: Our Supercluster Home

The new 3D map developed by Tully and colleagues shows that the Milky Way galaxy resides in the outskirts of the Laniakea Supercluster, which is about 520 million light-years wide. The supercluster is made up of about 100,000 galaxies with a total mass about 100 million billion times that of the sun. [How Computers Simulate the Universe (Infographic)]

The name Laniakea was suggested by Nawa'a Napoleon, who teaches Hawaiian language at Kapiolani Community College in Hawaii. The name is meant to honor Polynesian navigators who used their knowledge of the heavens to make long voyages across the immensity of the Pacific Ocean.

"We live in the Local Group, which is part of the Local Sheet next to the Local Void — we wanted to come up with something a little more exciting than 'Local,'" Tully told Space.com.

This supercluster also includes the Virgo cluster and Norma-Hydra-Centaurus, otherwise known as  the Great Attractor. These new findings help clear up the role of the Great Attractor, which is a problem that has kept astronomers busy for 30 years. Within the Laniakea Supercluster, the motions of galaxies are directed inward, as water flows in descending paths down a valley, and the Great Attractor acts like a large flat-bottomed gravitational valley with a sphere of attraction that extends across the Laniakea Supercluster.

Tully noted Laniakea could be part of an even larger structure:

"We probably need to measure to another factor of three in distance to explain our local motion," Tully said. "We might find that we have to come up with another name for something larger than we're a part of — we're entertaining that as a real possibility."

Laniakea: Our home supercluster

The Laniakea Supercluster of Galaxies

Schematic Visualization

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Laniakea Supercluster

Additional References

Wikipedia - https://en.wikipedia.org/wiki/Laniakea_Supercluster

Images - click here

Google Search - click here

Laniakea Supercluster diagram

Laniakea Supercluster diagram

Laniakea Supercluster diagram with distances

Our Milky Way Galaxy

The Milky Way seen from the Rocky Mountains, USA

Where Earth is in the Milky Way

The Milky Way on a Summer's Eve

Pete Enns - Why "Original Author" [Theory] is Overrated

The Bible: Why "Original Author" [Theory] is Overrated
http://www.peteenns.com/the-bible-its-sort-of-like-a-viral-internet-joke-or-why-original-author-is-overrated/

by PeteEnns
[*any edits or emendations mine - r.e. slater]
March 6, 2017
Topical Section: Nature of the Bible32

If you know how Wikipedia works, you have a good idea of how the authorship of biblical books went down: an anonymous text is added to over time, but none of the additions are screaming for individual recognition.

Benjamin Sommer explains the phenomenon this way:

"As Walter Jackson Bate and Harold Bloom have shown, poets since the romantic era [sic] have attempted to cover up the extent to which they are indebted to their predecessors. Ancient and medieval authors, however, saw their writings as valuable only if they contributed to a mighty stream that predated and transcended them. Where a modern author (to borrow language from T. S. Eliot) emphasizes individual talent, the ancients found meaning in tradition. They believed in all sincerity that anything of merit in their writing was the product of insight they culled from earlier authorities and of skills they learned from their masters. (Revelation and Authority, p. 139, my emphasis; see also here and here and here)."

Modern notions of “authorship” value individual talent and creativity. In antiquity, “authors” were valued by being seen as part of a greater whole, as standing in a tradition.

The modern obsession with individual authorship of biblical texts is the very thing that the Old Testament “authors” seem determined to obscure.

Consider the book of Psalms. Over time, David came to be associated with the book as a whole, which included “authoring” psalms that stem from a much later time. Why? Because these later authors and compilers saw themselves not as individual authors, but as purveyors of a tradition.

Likewise, the book of Proverbs is associated with Solomon, but the book as a whole is a compilation of proverbial sayings that span a great length of time.

This same notion can be applied to Isaiah. All but a very few scholars agree that the book of Isaiah, though rooted in the 8th c. BCE, is added to until the postexilic period (late 6th and into the 5th centuries BCE) where it reached the form as we know it. These later authors, however, continued to attribute the book as a whole [to] the 8th century prophet Isaiah—not in an attempt to fool anyone, but because their notion of “[traditional] authorship” demanded it.

And of course, we have the Pentateuch—that diverse collection of laws and narratives that did not reach it’s final form until well after the return from Babylonian exile (539 BCE), though all of it claims to be rooted in the time of Moses.

The “late” authorship of biblical books—which is so central to modern biblical scholarship and yet so problematic, even heretical, to others—makes perfect sense if we adopt ancient notions of “authorship” rather than modern ones.

Adding one’s voice to an ancient tradition without acknowledging it isn’t “lying” or “showing disrespect for God’s word.” It is how ancient authorship works—it is how the truth is told and how one shows respect for the tradition.

Modern assumptions of how authorship “should” work need to be set aside if we want to “take seriously” the biblical text.

Sommer uses a well-known internet joke to explain further how ancient authorship works: “Why God Could Not Get Tenure at a University.” The [email comments he found read like this]:

• He only has one publication;
• it has no footnotes;
• it is in Hebrew;
• when one experiment went amiss, He tried to cover it up by drowning all the subjects;
• some doubt He even wrote it Himself.
• [a fuller Internet list can be found below - res]

A real knee-slapper, of course, but Sommer noticed that none of the forwarded emails contained precisely the same list. Some of the reasons remained constant, but the exact wording was tweaked and the number of reasons given varied. (I might also add that the joke exists with at least one alternate name, “Why God Couldn’t Get a PhD,” or some other variation).

Sommer explains:

"Because anyone who forwards an email can alter the text, various people (whether my friends, or the people who sent them, or some unknown person in the chain before that) had introduced small modifications, additions, and subtractions. Some people must have said to themselves, “It would be even funnier if I rephrase this one a little,” “Here’s a good one I thought of myself,” “I can take a joke as well as the next guy, but this one’s just sacrilegious.” Even though it was clear that people who passed the lists on often intervened in the text, I never saw anyone’s name attached to a list as author, even as partial author. It would have been ridiculous for someone who made a minor alteration to claim that status."

The situation of biblical scribes, mutatis mutandis, was similar. A scribe who added a line, even rephrased a sentence, or combined two texts did not regard himself as the author, and no one person is the “real” author. As a desire to attribute texts to particular authors became more common over time in ancient Israel, scribes connected texts with specicific figure, but putting their own name on texts they were transmitting would have been grossly inappropriate. In such a situation, attribution to a respected symbolic figure from the past was culturally sensible. (p. 141, reformatted, emphasis added)

Wikipedia, emails, and the Internet as a whole are helpful analogies for understanding what the Bible is—a living, moving, dynamic, tradition.

The “word of God written,” as some describe the Bible, is itself complex and dynamic, a back-and-forth between respect for tradition and the need to continue transforming it. That much seems crystal clear to me.

The question we need to be asking, however, is as it has always been for Christians:

• does reading the Bible faithfully mean continuing that “transformative” trajectory, or shutting it down?

• Does the biblical “canon” function as a closed book of rules or as a [more open] model for a necessarily continuing theological process?

I think these are viable questions raised by paying attention to the Bible itself—both within the Old Testament and in how the New Testament authors appropriate it.

- PE

* * * * * * * * * * *

Why God Didn't Get Tenure

(revised and expanded report)

Dear Mr. Dean,

At your request, the Tenure Evaluation Committee has once more re-evaluated Mr. God's application. [But] we regret to inform you that after careful analysis the Committee unanimously resolved to uphold the original recommendation. We repeat below the reasons that led us to this decision --- including several points which, in a misguided attempt to preserve academic decorum and the Candidate's reputation, we had chosen to omit from the original report.

1. He had only one major publication.
2. It wasn't written in English.
3. It wasn't published in a referred journal,
4. ... it has no references,
5. ... it lacks a review of previous work,
6. ... and does not even mention alternative approaches to the problem.
7. Its many sweeping claims were not backed by formal proofs.
8. There is evidence that some parts of the text were plagiarized.
9. Some even doubt that He wrote it Himself.
10. He performed His chief experiment only once, with no control experiments.
11. It is still not clear whether His experiment succeeded at all.
12. Some of His acts caused extensive environmental damage and major property loss.
13. He neglected to keep a lab notebook.
14. He did not provide any error analysis or confidence intervals.
15. He did not use standard metric units.
16. His description of the experiment omitted essential details.
17. He cheated by deleting any subjects whose behavior did not fit His model.
18. The scientific community had a hard time replicating His results.
19. He encouraged, and apparently enjoyed, the pointless cruel sacrifice of animals.
20. He experimented with human subjects without Ethics Board's approval.
21. He was idle for many years, and only started working one week before the deadline.
22. He did not get any government or industrial support for His project.
23. In fact, he has never written a single grant proposal.
24. He never served on any committees, and never attended a faculty meeting.
25. He was never awarded a doctoral degree, not even an honorary one.
26. He would not tolerate criticism or discordant opinions.
27. His difficult personality has prevented effective collaboration with His peers.
28. He had His first two grad students expelled, for sheer professional jealously.
29. Since that incident, He couldn't or wouldn't recruit any new grad students.
30. His research lab has been deserted and inactive for ages.
31. Throughout His entire career, He taught only one course...
32. ... whose syllabus can be reduced to ten trivial rules-of-thumb.
33. In fact, after the first lecture He hardly showed up in class.
34. There are reports that He once sent His Son to teach the class.
35. His lectures were lots of high-sounding talk with little technical substance.
36. His practical demos were often too dangerous to students.
37. Students were forced to use His own textbook, which is quite old and lacks exercises.
38. Most students felt that His grading was too harsh and unfair.
39. He was a slow grader and often wouldn't give students any feedback until it was too late.
40. He insisted on using only pass/fail grades instead of the standard A-F system.
41. He would not grade on a curve, and once He flunked all of His students but one ...
42. ... to whom He had previously revealed the exam's content.
43. He didn't keep a homepage and didn't read His email.
44. His office hours were infrequent and were often held in inconvenient locations.
45. He violated the honor system by being omnipresent even during examinations.
46. He made some rude and demeaning remarks about students who failed His tests.
47. He used obsolete teaching methods, such as peer pressure and guilt manipulation.
48. He even resorted to physical punishment.
49. His controversial views on race and sex could have harmed the university's image.
50. He showed some creativity once, it's true; but what has He done since then?

Respectfully yours,

(original signed by TEC Chairman)

Last edited on 2004-01-06 16:29:04 by stolfi

R.E. Slater - The Quantum Universe We Live In

"Whole regions of space will never be observable from Earth for that reason. Mack noted that assuming inflation happened, the universe is actually 10 to the 23 times bigger than the 46 billion light-years humans can see. So if there is an edge to the universe, it's so far away Earthlings can't see it, and never will." - Dr. Katie Mack

"By definition, the universe contains everything, so there is no "outside." Physicist Stephen Hawking has often said that the whole question makes no sense, because if the universe came from nothing and brought everything into existence, then asking what lies beyond the universe is like asking what is north of the North Pole." - Dr. Stephen Hawking

While away last month visiting Mexico's beautiful Gulf coasts (our first time) to rest and heal up from the past 14 months of horrible health, infectious diseases, and complex surgery gone wrong, I decided to catch up on quantum scientific breakthroughs in cosmological studies of the universe. I chose Paul Halpern's Edge of the Universe book (2012) as my guide and was not disappointed.

When not talking to Serbian, Argentinian and Sri Lanka friends we readily made, or when not having great conversations with any number of non-American guests and workers, I had hoped to have selected a simple study guide offering edge-of-the-seat, can't-wait-what's-next, discussion of "the universe we think we know" and "the quantum one we're now discovering."  And so, with every turn of an orbital research satellite zooming around the earth or, star-filled observatory log documenting that evening's findings, the search for the quantum structures of the universe continue apace with the technology we have on hand.

The other reason I thought to undertake this task was to put into historical perspective all those Stephen Hawking's physics and philosophical readings I did so many years ago. Here too I discovered a few more new developments in quantum astrophysics that were yet in their infancy or non-existent a decade or two ago. So this too was an expectation met.

And so, for those readers who are interested in the cosmos in which we live - and are trying to understand - here's some mind-blowing statements I've come across to get you started . Enjoy!

R. E. Slater

March 15, 2017

Mind-blowing statements:

Where is the center of the universe? EVERYWHERE! Any point in the universe is factually the center of the universe.

What is the hiss found in the static background of the universe? It is the left over remnants, or relic-radiation, of the Big Bang 13.75 billion years ago.

When we look back in time how is this done? It is done every time "old" light (photonic radiation) is captured by our eye or camera lens. The further the light the further its travel to us and older its "reveal."

How far back can we see? At present half our universe in any one direction (45.6 to 46.5 billion light years away) which makes the universe approximately 93b LYs across. But no more than 62b LYs (or 124b Lys across) in any one direction as our space in the universe is expanding as quickly as all other spaces. And too quickly for the speed of photoaic radiation (light) to surpass/overcome these expanding distances.

Was the universe always infinite if it began as a singularity? Yes. It is both inherently and theoretical infinite in all directions at once even as it expanded from its singularity point.

How is this possible? Because time is measured by speed and distance (photon emittal between massless, primordial-Higgs forces) so that as the universe "brewed" so did matter which was held time captive. In effect there was no time. It's was part of a liquefied hyperspace consisting of 0, 1, or 2 dimensions (not the 3D, matter, or 4D, Space-Time, we are familiar with today). Thus, primordial time was as "infinite in its eternity" as matter was "infinite in its spatial dimensions." This was the substance of the singularity of the Big Bang before the Higgs boson fixed its rotation and gave all particles their mass.

What happened when the Big Bang tripped over its threshold of expansion? In less than a flash of a second (faster than ultra short gamma ray bursts), 10 to the -32 second to be exact, the BB expanded instantly across a non-existent void to a distance of 10 to the 78th factor, in a violent explosion. If you had been looking at the Big Bang and blinked your eyes you would have found yourself standing in the middle of our present-day universe (minus it's supercooling phase where homogeneous matter-blobs clumped together to form the stars, nebulae and galaxies to come. This took the remaining 13.75 billion years to create.

What shape is the universe? Is it spherical, oval, elongated, thin, or web-like in its mega-cluster lattices (essentially it looks more like a sea sponge's structure than a spider web)? Yes, it is all this but scientifically it is considered flat as it is propelled infinitely outwards into a void that isn't there by creating its own space.

When will this expansion stop? During its first six billion years dark matter's gravitational force was holding the universe back in order for it to form. If dark matter had continued as a force the universe would eventually reverse course and become crunched up back into a singularity again ("singularity" means something that is unique).

What stopped dark matter's effect? At around 8 billion years ago dark energy overcame dark matter and for the past eight billion years has been propelling the universe at exceedingly faster and faster rates. If this dynamic force holds then the universe will be ripped apart into nothingness - even down to its subatomic structures. Effectively all will cease to exist because all has been separated from itself (reminds me of spiritual death as an annihilating force ripping body-soul-spirit and all creational connections apart).

What does this mean? That we live in a connected universe. Without connectivity we have no presence. If we collect all the matter in the universe it would consist of 4-5% of everything in it. The stuff we don't know and cannot measure or see is dark. We named this dark matter (23%) + dark energy (72%) = 95% of the remaining universe. Effectively, even the stuff that we don't understand or can't feel or see impacts us with a massively unseen force. Thus, we live in a connected cosmos - not only with matter and forces but with each other (also composed of matter and forces). Everything effects the movement, rotation, and direction of the other back to ourselves and back again to others, creation, and even God our Creator.

R.E. Slater

March 15, 2017

Additional References

• http://www.iflscience.com/space/the-edge-of-the-universe-is-closer-than-scientists-previously-thought/

• http://www.livescience.com/33646-universe-edge.html

• https://www.google.com.mx/amp/amp.space.com/33005-where-is-the-universes-edge-op-ed.html?client=ms-android-verizon

• Harvard.edu - https://www.cfa.harvard.edu/~ejchaisson/cosmic_evolution/docs/fr_1/fr_1_site_summary.html

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Physical cosmology

From Wikipedia, the free encyclopedia

  (Redirected from Cosmic evolution)

This article is about the branch of physics and astronomy. For other uses, see Cosmology.

"Cosmic Evolution" redirects here. For the book by Eric Chaisson, see Cosmic Evolution (book).

Part of a series on
Physical cosmology
Big Bang · Universe Age of the universe Chronology of the universe
Early universe[show]
Expansion · Future[show]
Components · Structure[show]
Experiments[show]
Scientists[show]
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Category  Cosmology portal  Astronomy portal
v t e

Physical cosmology is the study of the largest-scale structures and dynamics of the Universe and is concerned with fundamental questions about its origin, structure, evolution, and ultimate fate.^[1] Cosmology as a science originated with the Copernican principle, which implies that celestial bodies obey identical physical laws to those on Earth, and Newtonian mechanics, which first allowed us to understand those physical laws. Physical cosmology, as it is now understood, began with the development in 1915 of Albert Einstein's general theory of relativity, followed by major observational discoveries in the 1920s: first, Edwin Hubble discovered that the universe contains a huge number of external galaxies beyond our own Milky Way; then, work by Vesto Slipher and others showed that the universe is expanding. These advances made it possible to speculate about the origin of the universe, and allowed the establishment of the Big Bang Theory, by Georges Lemaitre, as the leading cosmological model. A few researchers still advocate a handful of alternative cosmologies;^[2]however, most cosmologists agree that the Big Bang theory explains the observations better.

Dramatic advances in observational cosmology since the 1990s, including the cosmic microwave background, distant supernovae and galaxy redshift surveys, have led to the development of a standard model of cosmology. This model requires the universe to contain large amounts of dark matter and dark energy whose nature is currently not well understood, but the model gives detailed predictions that are in excellent agreement with many diverse observations.^[3]

Cosmology draws heavily on the work of many disparate areas of research in theoretical and applied physics. Areas relevant to cosmology include particle physics experiments and theory, theoretical and observational astrophysics, general relativity, quantum mechanics, and plasma physics.

Subject history[edit]

Nature timeline

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Earliest light

cosmic speed-up

Solar System

water

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photosynthesis

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life

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Dark energy

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Omega Centauri forms

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Andromeda Galaxy forms

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Axis scale: billions of years.
Also see: Human timeline and Life timeline

See also: Timeline of cosmology and List of cosmologists

Modern cosmology developed along tandem tracks of theory and observation. In 1916, Albert Einstein published his theory of general relativity, which provided a unified description of gravity as a geometric property of space and time.^[4] At the time, Einstein believed in a static universe, but found that his original formulation of the theory did not permit it.^[5] This is because masses distributed throughout the universe gravitationally attract, and move toward each other over time.^[6] However, he realized that his equations permitted the introduction of a constant term which could counteract the attractive force of gravity on the cosmic scale. Einstein published his first paper on relativistic cosmology in 1917, in which he added this cosmological constant to his field equations in order to force them to model a static universe.^[7] However, this so-called Einstein model is unstable to small perturbations—it will eventually start to expand or contract.^[5] The Einstein model describes a static universe; space is finite and unbounded (analogous to the surface of a sphere, which has a finite area but no edges). It was later realized that Einstein's model was just one of a larger set of possibilities, all of which were consistent with general relativity and the cosmological principle. The cosmological solutions of general relativity were found by Alexander Friedmann in the early 1920s.^[8] His equations describe the Friedmann–Lemaître–Robertson–Walker universe, which may expand or contract, and whose geometry may be open, flat, or closed.

History of the Universe – gravitational waves are hypothesized to arise from cosmic inflation, a faster-than-light expansion just after the Big Bang^[9][10][11]

In the 1910s, Vesto Slipher (and later Carl Wilhelm Wirtz) interpreted the red shift of spiral nebulae as a Doppler shift that indicated they were receding from Earth.^[12][13] However, it is difficult to determine the distance to astronomical objects. One way is to compare the physical size of an object to its angular size, but a physical size must be assumed to do this. Another method is to measure the brightness of an object and assume an intrinsic luminosity, from which the distance may be determined using the inverse square law. Due to the difficulty of using these methods, they did not realize that the nebulae were actually galaxies outside our own Milky Way, nor did they speculate about the cosmological implications. In 1927, the Belgian Roman Catholic priest Georges Lemaître independently derived the Friedmann–Lemaître–Robertson–Walker equations and proposed, on the basis of the recession of spiral nebulae, that the universe began with the "explosion" of a "primeval atom"^[14]—which was later called the Big Bang. In 1929, Edwin Hubble provided an observational basis for Lemaître's theory. Hubble showed that the spiral nebulae were galaxies by determining their distances using measurements of the brightness of Cepheid variable stars. He discovered a relationship between the redshift of a galaxy and its distance. He interpreted this as evidence that the galaxies are receding from Earth in every direction at speeds proportional to their distance.^[15] This fact is now known as Hubble's law, though the numerical factor Hubble found relating recessional velocity and distance was off by a factor of ten, due to not knowing about the types of Cepheid variables.

Given the cosmological principle, Hubble's law suggested that the universe was expanding. Two primary explanations were proposed for the expansion. One was Lemaître's Big Bang theory, advocated and developed by George Gamow. The other explanation was Fred Hoyle's steady state model in which new matter is created as the galaxies move away from each other. In this model, the universe is roughly the same at any point in time.^[16][17]

For a number of years, support for these theories was evenly divided. However, the observational evidence began to support the idea that the universe evolved from a hot dense state. The discovery of the cosmic microwave background in 1965 lent strong support to the Big Bang model,^[17] and since the precise measurements of the cosmic microwave background by the Cosmic Background Explorer in the early 1990s, few cosmologists have seriously proposed other theories of the origin and evolution of the cosmos. One consequence of this is that in standard general relativity, the universe began with a singularity, as demonstrated by Roger Penrose and Stephen Hawking in the 1960s.

An alternative view to extend the Big Bang model, suggesting the universe had no beginning or singularity and the age of the universe is infinite, has been presented.^[18][19][20]

Energy of the cosmos[edit]

Light chemical elements, primarily hydrogen and helium, were created in the Big Bang process (see Nucleosynthesis). The small atomic nuclei combined into larger atomic nuclei to form heavier elements such as iron and nickel, which are more stable (see Nuclear fusion). This caused a later energy release. Such reactions of nuclear particles inside stars continue to contribute to sudden energy releases, such as in nova stars. Gravitational collapse of matter into black holes is also thought to power the most energetic processes, generally seen at the centers of galaxies (see Quasar and Active galaxy).

Cosmologists cannot explain all cosmic phenomena exactly, such as those related to the accelerating expansion of the universe, using conventional forms of energy. Instead, cosmologists propose a new form of energy called dark energy that permeates all space.^[21] One hypothesis is that dark energy is the energy of virtual particles, which are believed to exist in a vacuum due to the uncertainty principle.

There is no clear way to define the total energy in the universe using the most widely accepted theory of gravity, general relativity. Therefore, it remains controversial whether the total energy is conserved in an expanding universe. For instance, each photon that travels through intergalactic space loses energy due to the redshift effect. This energy is not obviously transferred to any other system, so seems to be permanently lost. On the other hand, some cosmologists insist that energy is conserved in some sense; this follows the law of conservation of energy.^[22]

Thermodynamics of the universe is a field of study that explores which form of energy dominates the cosmos – relativistic particles which are referred to as radiation, or non-relativistic particles referred to as matter. Relativistic particles are particles whose rest mass is zero or negligible compared to their kinetic energy, and so move at the speed of light or very close to it; non-relativistic particles have much higher rest mass than their energy and so move much slower than the speed of light.

As the universe expands, both matter and radiation in it become diluted. However, the energy densities of radiation and matter dilute at different rates. As a particular volume expands, mass energy density is changed only by the increase in volume, but the energy density of radiation is changed both by the increase in volume and by the increase in the wavelength of the photons that make it up. Thus the energy of radiation becomes a smaller part of the universe's total energy than that of matter as it expands. The very early universe is said to have been 'radiation dominated' and radiation controlled the deceleration of expansion. Later, as the average energy per photon becomes roughly 10 eV and lower, matter dictates the rate of deceleration and the universe is said to be 'matter dominated'. The intermediate case is not treated well analytically. As the expansion of the universe continues, matter dilutes even further and the cosmological constant becomes dominant, leading to an acceleration in the universe's expansion.

History of the universe[edit]

See also: Timeline of the Big Bang

The history of the universe is a central issue in cosmology. The history of the universe is divided into different periods called epochs, according to the dominant forces and processes in each period. The standard cosmological model is known as the Lambda-CDM model.

Equations of motion[edit]

Main article: Friedmann–Lemaître–Robertson–Walker metric

The equations of motion governing the universe as a whole are derived from general relativity with a small, positive cosmological constant.^[23] The solution is an expanding universe; due to this expansion, the radiation and matter in the universe cool down and become diluted. At first, the expansion is slowed down by gravitation attracting the radiation and matter in the universe. However, as these become diluted, the cosmological constant becomes more dominant and the expansion of the universe starts to accelerate rather than decelerate. In our universe this happened billions of years ago.

Particle physics in cosmology[edit]

Main article: Particle physics in cosmology

Particle physics is important to the behavior of the early universe, because the early universe was so hot that the average energy density was very high. Because of this, scattering processes and decay of unstable particles are important in cosmology.

As a rule of thumb, a scattering or a decay process is cosmologically important in a certain cosmological epoch if the time scale describing that process is smaller than, or comparable to, the time scale of the expansion of the universe. The time scale that describes the expansion of the universe is ${\displaystyle 1/H}$ with ${\displaystyle H}$ being the Hubble constant, which itself actually varies with time. The expansion timescale ${\displaystyle 1/H}$ is roughly equal to the age of the universe at that time.

Timeline of the Big Bang[edit]

Main article: Timeline of the Big Bang

Observations suggest that the universe began around 13.8 billion years ago.^[24] Since then, the evolution of the universe has passed through three phases. The very early universe, which is still poorly understood, was the split second in which the universe was so hot that particles had energies higher than those currently accessible in particle accelerators on Earth. Therefore, while the basic features of this epoch have been worked out in the Big Bang theory, the details are largely based on educated guesses. Following this, in the early universe, the evolution of the universe proceeded according to known high energy physics. This is when the first protons, electrons and neutrons formed, then nuclei and finally atoms. With the formation of neutral hydrogen, the cosmic microwave background was emitted. Finally, the epoch of structure formation began, when matter started to aggregate into the first stars and quasars, and ultimately galaxies, clusters of galaxies and superclusters formed. The future of the universe is not yet firmly known, but according to the ΛCDM model it will continue expanding forever.

Areas of study[edit]

Below, some of the most active areas of inquiry in cosmology are described, in roughly chronological order. This does not include all of the Big Bang cosmology, which is presented in Timeline of the Big Bang.

Very early universe[edit]

The early, hot universe appears to be well explained by the Big Bang from roughly 10⁻³³ seconds onwards, but there are several problems. One is that there is no compelling reason, using current particle physics, for the universe to be flat, homogeneous, and isotropic (see the cosmological principle). Moreover, grand unified theories of particle physics suggest that there should be magnetic monopoles in the universe, which have not been found. These problems are resolved by a brief period of cosmic inflation, which drives the universe to flatness, smooths out anisotropies and inhomogeneities to the observed level, and exponentially dilutes the monopoles. The physical model behind cosmic inflation is extremely simple, but it has not yet been confirmed by particle physics, and there are difficult problems reconciling inflation and quantum field theory. Some cosmologists think that string theory and brane cosmology will provide an alternative to inflation.

Another major problem in cosmology is what caused the universe to contain far more matter than antimatter. Cosmologists can observationally deduce that the universe is not split into regions of matter and antimatter. If it were, there would be X-rays and gamma rays produced as a result of annihilation, but this is not observed. Therefore, some process in the early universe must have created a small excess of matter over antimatter, and this (currently not understood) process is called baryogenesis. Three required conditions for baryogenesis were derived by Andrei Sakharov in 1967, and requires a violation of the particle physics symmetry, called CP-symmetry, between matter and antimatter. However, particle accelerators measure too small a violation of CP-symmetry to account for the baryon asymmetry. Cosmologists and particle physicists look for additional violations of the CP-symmetry in the early universe that might account for the baryon asymmetry.

Both the problems of baryogenesis and cosmic inflation are very closely related to particle physics, and their resolution might come from high energy theory and experiment, rather than through observations of the universe.

Big Bang Theory[edit]

Main article: Big bang nucleosynthesis

Big Bang nucleosynthesis is the theory of the formation of the elements in the early universe. It finished when the universe was about three minutes old and its temperature dropped below that at which nuclear fusion could occur. Big Bang nucleosynthesis had a brief period during which it could operate, so only the very lightest elements were produced. Starting from hydrogen ions (protons), it principally produced deuterium, helium-4, and lithium. Other elements were produced in only trace abundances. The basic theory of nucleosynthesis was developed in 1948 by George Gamow, Ralph Asher Alpher, and Robert Herman. It was used for many years as a probe of physics at the time of the Big Bang, as the theory of Big Bang nucleosynthesis connects the abundances of primordial light elements with the features of the early universe. Specifically, it can be used to test the equivalence principle, to probe dark matter, and test neutrino physics. Some cosmologists have proposed that Big Bang nucleosynthesis suggests there is a fourth "sterile" species of neutrino.

Standard model of Big Bang cosmology[edit]

The ΛCDM (Lambda cold dark matter) or Lambda-CDM model is a parametrization of the Big Bang cosmological model in which the universe contains a cosmological constant, denoted by Lambda (Greek Λ), associated with dark energy, and cold dark matter (abbreviated CDM). It is frequently referred to as the standard model of Big Bang cosmology.

Cosmic microwave background[edit]

Main article: Cosmic microwave background

Evidence of gravitational waves in the infant universe may have been uncovered by the microscopic examination of the focal plane of the BICEP2 radio telescope.^{[9][10][11][25]}

The cosmic microwave background is radiation left over from decoupling after the epoch of recombination when neutral atoms first formed. At this point, radiation produced in the Big Bang stopped Thomson scattering from charged ions. The radiation, first observed in 1965 by Arno Penzias and Robert Woodrow Wilson, has a perfect thermal black-body spectrum. It has a temperature of 2.7 kelvins today and is isotropic to one part in 10⁵. Cosmological perturbation theory, which describes the evolution of slight inhomogeneities in the early universe, has allowed cosmologists to precisely calculate the angular power spectrum of the radiation, and it has been measured by the recent satellite experiments (COBE and WMAP) and many ground and balloon-based experiments (such as Degree Angular Scale Interferometer, Cosmic Background Imager, and Boomerang). One of the goals of these efforts is to measure the basic parameters of the Lambda-CDM model with increasing accuracy, as well as to test the predictions of the Big Bang model and look for new physics. The recent measurements made by WMAP, for example, have placed limits on the neutrino masses.

Newer experiments, such as QUIET and the Atacama Cosmology Telescope, are trying to measure the polarization of the cosmic microwave background. These measurements are expected to provide further confirmation of the theory as well as information about cosmic inflation, and the so-called secondary anisotropies, such as the Sunyaev-Zel'dovich effect and Sachs-Wolfe effect, which are caused by interaction between galaxies and clusters with the cosmic microwave background.

On 17 March 2014, astronomers at the Harvard–Smithsonian Center for Astrophysics announced the apparent detection of gravitational waves, which, if confirmed, may provide strong evidence for inflation and the Big Bang.^{[9][10][11][25]} However, on 19 June 2014, lowered confidence in confirming the cosmic inflation findings was reported.^[26][27][28]

Formation and evolution of large-scale structure[edit]

Main articles: Large-scale structure of the cosmos, Structure formation, and Galaxy formation and evolution

Understanding the formation and evolution of the largest and earliest structures (i.e., quasars, galaxies, clusters and superclusters) is one of the largest efforts in cosmology. Cosmologists study a model of hierarchical structure formation in which structures form from the bottom up, with smaller objects forming first, while the largest objects, such as superclusters, are still assembling. One way to study structure in the universe is to survey the visible galaxies, in order to construct a three-dimensional picture of the galaxies in the universe and measure the matter power spectrum. This is the approach of the Sloan Digital Sky Survey and the 2dF Galaxy Redshift Survey.

Another tool for understanding structure formation is simulations, which cosmologists use to study the gravitational aggregation of matter in the universe, as it clusters into filaments, superclusters and voids. Most simulations contain only non-baryonic cold dark matter, which should suffice to understand the universe on the largest scales, as there is much more dark matter in the universe than visible, baryonic matter. More advanced simulations are starting to include baryons and study the formation of individual galaxies. Cosmologists study these simulations to see if they agree with the galaxy surveys, and to understand any discrepancy.

Other, complementary observations to measure the distribution of matter in the distant universe and to probe reionization include:

• The Lyman-alpha forest, which allows cosmologists to measure the distribution of neutral atomic hydrogen gas in the early universe, by measuring the absorption of light from distant quasars by the gas.
• The 21 centimeter absorption line of neutral atomic hydrogen also provides a sensitive test of cosmology
• Weak lensing, the distortion of a distant image by gravitational lensing due to dark matter.

These will help cosmologists settle the question of when and how structure formed in the universe.

Dark matter[edit]

Main article: Dark matter

Evidence from Big Bang nucleosynthesis, the cosmic microwave background and structure formation suggests that about 23% of the mass of the universe consists of non-baryonic dark matter, whereas only 4% consists of visible, baryonic matter. The gravitational effects of dark matter are well understood, as it behaves like a cold, non-radiative fluid that forms haloes around galaxies. Dark matter has never been detected in the laboratory, and the particle physics nature of dark matter remains completely unknown. Without observational constraints, there are a number of candidates, such as a stable supersymmetric particle, a weakly interacting massive particle, an axion, and a massive compact halo object. Alternatives to the dark matter hypothesis include a modification of gravity at small accelerations (MOND) or an effect from brane cosmology.

Dark energy[edit]

Main article: Dark energy

If the universe is flat, there must be an additional component making up 73% (in addition to the 23% dark matter and 4% baryons) of the energy density of the universe. This is called dark energy. In order not to interfere with Big Bang nucleosynthesis and the cosmic microwave background, it must not cluster in haloes like baryons and dark matter. There is strong observational evidence for dark energy, as the total energy density of the universe is known through constraints on the flatness of the universe, but the amount of clustering matter is tightly measured, and is much less than this. The case for dark energy was strengthened in 1999, when measurements demonstrated that the expansion of the universe has begun to gradually accelerate.

Apart from its density and its clustering properties, nothing is known about dark energy. Quantum field theory predicts a cosmological constant (CC) much like dark energy, but 120 orders of magnitude larger than that observed. Steven Weinberg and a number of string theorists (see string landscape) have invoked the 'weak anthropic principle': i.e. the reason that physicists observe a universe with such a small cosmological constant is that no physicists (or any life) could exist in a universe with a larger cosmological constant. Many cosmologists find this an unsatisfying explanation: perhaps because while the weak anthropic principle is self-evident (given that living observers exist, there must be at least one universe with a cosmological constant which allows for life to exist) it does not attempt to explain the context of that universe. For example, the weak anthropic principle alone does not distinguish between:

• Only one universe will ever exist and there is some underlying principle that constrains the CC to the value we observe.
• Only one universe will ever exist and although there is no underlying principle fixing the CC, we got lucky.
• Lots of universes exist (simultaneously or serially) with a range of CC values, and of course ours is one of the life-supporting ones.

Other possible explanations for dark energy include quintessence or a modification of gravity on the largest scales. The effect on cosmology of the dark energy that these models describe is given by the dark energy's equation of state, which varies depending upon the theory. The nature of dark energy is one of the most challenging problems in cosmology.

A better understanding of dark energy is likely to solve the problem of the ultimate fate of the universe. In the current cosmological epoch, the accelerated expansion due to dark energy is preventing structures larger than superclusters from forming. It is not known whether the acceleration will continue indefinitely, perhaps even increasing until a big rip, or whether it will eventually reverse.

Other areas of inquiry[edit]

Cosmologists also study:

• Whether primordial black holes were formed in our universe, and what happened to them.
• The GZK cutoff for high-energy cosmic rays, and whether it signals a failure of special relativity at high energies
• The equivalence principle, whether or not Einstein's general theory of relativity is the correct theory of gravitation, and if the fundamental laws of physics are the same everywhere in the universe.
• The increasing complexity of universal structures, an example being the progressively greater energy rate density.^[29]

See also[edit]

• Hubble's law
• Illustris project
• List of cosmologists
• Photon
• Physical ontology
• String cosmology
• Universal Rotation Curve