User: Paine Ellsworth/on Cosmology
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Cosmology is the study of the origin, evolution, and eventual fate of the Universe. The scholarly and scientific study of the origin, large-scale structures and dynamics, plus the ultimate fate of the Universe, as well as the scientific laws that govern these realities, is called physical cosmology.
Particle physics (also called "high energy physics") is the branch of science that studies the nature of the particles that constitute matter (particles with mass) and radiation (massless particles). Although the word "particle" can refer to various types of very small objects (e.g. protons, gas particles, or even household dust), "particle physics" usually investigates the irreducibly smallest detectable particles and the irreducibly fundamental force fields necessary to explain them.
This is a, sort of, "un-article", a non-article about a few of my own perceptions on the present state of the science of cosmology (2017) and about the Universe. I am Paine Ellsworth and I approved this message. (I always want to put that in mainspace-article leads, but of course, that's a no-no. :>)
- 1 Expansion of mental matter and energy
- 2 On the Enigmatic Continuum
- 3 What actually can be observed
- 4 Speculations
- 5 Negative time
- 6 Expanding? or stretching
- 7 See also
- 8 Notes
- 9 References
- 10 External links
Expansion of mental matter and energy
Over a period of many years there have been several little bits and pieces of evidence that point to a beginning of the Universe in which we live. Cosmologists and particle physicists have dubbed the originator's "primeval atom" with the more popular name, the Big Bang theory of the beginning of the Universe or the "BB". Alone and by themselves, nearly all of the little bits and pieces of evidence could have one or more plausible explanations apart from the Big Bang; however, there is (and has been for a very long time) one single important piece of evidence that has been by far the most compelling. It has been the most compelling evidence because it was actually predicted years before it was discovered, and the evidence that is so compelling is the cosmic microwave background or the "CMB". That evidence, which itself might also be evidence for one or more other explanations of the state of the Universe, had been predicted twelve years before it was discovered, and it had been predicted specifically as a measurable result of the BB. The CMB, predicted by Gamow and Alpher in their heralded Αβγ paper (1948), was discovered by accident from the work of Penzias and Wilson.
The Big Bang theory of the beginning of the Universe prevails in science mainly because of that one compelling bit of evidence, the CMB, which has been extensively studied, and by the fact that no proposed state of the Universe other than the BB so thoroughly seems to answer many of the questions that have arisen as a result of all the combined evidence over the years; however, that has been extensively argued.
While science embraces the many puzzling consequences of the BB, I continue to think that more evidence is needed and am hoping that the James Webb Space Telescope or "JWST", scheduled to be sent into orbit in October of 2018, will dig deeply enough to answer the questions that cosmologists and I have in regard to several still-standing mysteries of the Big Bang theory. The data that the Webb gathers will either support or possibly refute the BB. We can only wait and see.
On the Enigmatic Continuum
Meanwhile while we wait, perhaps we may collect thoughts about a huge unknown regarding the BB: the Enigmatic Continuum (EC). I know of no other name to call it. The EC is not a frivolous name even though it isn't described by that name by most scientists (it is in fact hardly described at all). I remember reading the published thoughts of one scientist, who is a particle physicist and a trained cosmologist – I think it was Alan Guth. He described the very beginning of the Universe (the very reason the Big Bang sprang into being to expand into our present Universe). He said the uncertainty principle allows for a "disturbance in the continuum" that resulted in the BB. He did not go into detail as to the nature or structure of either the "disturbance" or that "continuum". Since scientists presently accept that both space and time started with the BB, the structure of that Enigmatic Continuum must be interesting indeed.
For clarity, let's look at a long-standing premise, one of the perhaps oversimplified descriptions of the theory. No, I'm not going to talk about raisins in rising, baking muffins, although that decidedly is an interesting, though imprecise, representation. The description that is probably most compelling would be the expanding "balloon" or "bubble" – the bubble of space-time that has been expanding for 13.7 billion years.
This should not be confused with eternal inflation as an extension theory of the BB. However, if we imagine the Universe as having begun with an expansion (not an explosion – there are important differences) of space and time (the BB) and then a continued expansion outward from the center, we are left with a bubble of sorts, the outer film of which contains all the stars and galaxies in the Universe. As this bubble of space-time expands, the space between the galaxies increases; however, due to the limitation of the speed of light or c, these particular distance increases are impossible to observe. More on that in a moment.
So here we are, all the stars, all the galaxies, on the outer film layer of a gigantic bubble-like structure, and that structure continues to expand into an as yet unknown future. According to cosmologists, this expansion is accelerating in the present time. And now let us come back to what I've called the "Enigmatic Continuum". If space-time is only that part of the bubble that is the outer "film", then what precisely is inside this bubble (the area from where space-time has expanded), and what exactly is outside the bubble (that area into which space-time is expanding)? No one knows, and in fact this is one of the greatest mysteries of astronomy and cosmology. It is not "space-time", because space and time sit comfortably on the expanding "film" of the bubble. And if it isn't space-time, then what is it?
- the undefined, unknown and mysterious Enigmatic Continuum (?)
What actually can be observed
To return to the "impossible to observe" phrase used earlier, we are compelled to acknowledge that we are unable to see faraway galaxies in the present moment. Light from all those galaxies and their stars can travel no faster than c, the speed of light in vacuo, so the farther out into the Universe we peer, the longer ago into the past we see.
A galaxy that is, say, 8 megaparsecs (Mpc) away from Earth (that's 8 million parsecs) can also be said to be about 26 million light-years away. Since a light-year is the distance that light travels in the time of one year, then it takes 26 million years for the light from that galaxy to reach Earth. So we look at that galaxy and see how it appeared 26 million years ago. We can't possibly see or know what that galaxy looks like right now nor exactly where it is in the present time. That's the direct result of the lightspeed limitation.
If then, we are to accept the BB theory with all of its implications, we are compelled to see the present Universe as the outer edge of a huge, invisible sphere. When we use our Earth-based telescopes, or the Hubble space telescope (HST), or even the new Webb Space Telescope (JWST), to peer out into the cosmos, we can imagine all of the galaxies we can see as being on smaller concentric spheres inside the sphere of present space-time. Remembering that a light-year is a measure of distance (not a measure of time), a galaxy that is one hundred million light-years away may only be seen from Earth or the space near Earth as it appeared one hundred million years ago (not as it presently appears). So as we see that galaxy from Earth's vicinity, it is on a smaller, invisible, concentric sphere of space-time. It is, however, on a larger sphere of space-time than a galaxy that is, say, five hundred million light-years away from Earth.
To date, the farthest galaxy we can see with the HST is GN-z11. That ever so faraway galaxy is observed as it existed 13.4 billion years ago, just 350 million years or so after the Big Bang. So GN-z11 is on an invisible concentric sphere of space-time that is tiny compared with our present sphere. And it is relatively very close to what might be called the first concentric spheres of space-time, which formed just after the very beginning of the Universe.
If we accept the validity of the BB and the premise that the speed of light in a vacuum (c) cannot be exceeded by matter nor energy, then we must make a distinction between (A), the invisible concentric spheres we observe that take our vision back closer and closer to the central beginning point, and (B), what is actually between us and that central beginning point in the present time. What we actually observe is observable in the described manner solely because we are looking deeper and deeper into the past as we look farther and farther out into space. Were we able to see the area between Earth and the BB's central beginning point in the present time, with no need to allow for the limitation of c, then we might be able to see the EC, because that is what would be expected in that area in the present.
It is also good to remember that the presence of all of space-time on the outer "filmy" edge of a gigantic, bubble-like, invisible sphere is actually based upon the observation that faraway galaxies are moving away from us as they would if the sphere were continuing to expand. This is done by examining the light spectrum of an object and determining how much an element's (usually hydrogen) marker has shifted from its normal position (or what it would be in nearby space) toward the longer wavelengths or the "redder" end of the spectrum. The larger this shift, the farther away the object is and the faster it is moving away from Earth. Again, we must take care to remember that the light from which we resolve the spectrum and "redshift" has taken a long, long time to get from the object to our instruments. If we take that information and allow for the limitation of the speed of light, it may lead us to an entirely different "shape" of the Universe (rather than the expanding-sphere shape). And that may lead to an entirely different cosmology that might not include an initial Big Bang.
For a very long time, now, I've thought that, as Einstein wrote in his preface "note to the fifteenth edition" of his book Relativity:
In this edition I have added, as a fifth appendix, a presentation of my views on the problem of space in general and on the gradual modifications of our ideas on space resulting from the influence of the relativistic view-point. I wished to show that space-time is not necessarily something to which one can ascribe a separate existence, independently of the actual objects of physical reality. Physical objects are not in space, but these objects are spatially extended. In this way the concept "empty space" loses its meaning.
Since Einstein thought that matter's effect was to curve space, which resulted in gravity, that is probably what led him to the conclusion that space isn't "empty" or "nothing". If space were "nothing", then how could it possibly be curved? It is his final sentence above that has been the basis of my thinking on space since I first read it many years ago. It has led me to accept that space-time is not empty at all, not in the sense that when you've gotten your new computer home, opened the box, removed the computer and packing materials and are left with an "empty" box. Even out in the "space" between galaxies or the huge "voids" between galaxy clusters, space is still not empty in that sense. Space is just as "full" out there as it is where the Andromeda Galaxy is seen, seemingly "within" it, but actually a "spatially extended" part of space.
What is space "full" of?
Possibly Probably quantum foam. The effect here in our local world is exceedingly small, but not so small it cannot be measured. I think it's already been discovered and measured; however, the empiricists called it by a different name (and still do). If we consider "physical objects" as Einstein did, we can readily group "known matter" into two general categories: the near or local matter and the faraway matter. The makeup of "space-time", although barely measurable at the local level, becomes highly significant when we view large clumps of objects, such as those in the center of our galaxy. Just as we find that space is invisible in the local area, it is also invisible in faraway areas; however, the effect of the much larger levels of quantum foam in the center of our galaxy would be to appear as high levels of mass that we can only detect by its gravitational effects on visible mass. See dark matter, or as I call it, "spatial matter".
The ideas above seem to naturally lead to this "space that is something (not nothing)" as the actual origin and "cause" of gravity. Due to its small-scale physical properties, space experiences interactions with visible, physical matter and flows toward it. Upon reaching a physical object, the effect we call "gravity" is produced and keeps our feet on the ground.
Astronomers have been studying type Ia supernovas (type one-a) for a long time. At first they'd hoped that by determining the redshifts of those extremely faraway exploding stars they would find how much the Universe's expansion had slowed over time. Instead they found that the Universe's expansion rate may actually be getting faster – accelerating. Their studies show that up until about six billion years ago, the expansion may have actually been slowing down. Then apparently something happened – the expansion appears to have begun to increase, and it's rate of increase has either been steady or accelerating ever since. What happened six billion years back?
If you are familiar with the "quantum foam" model and the links in its Wikipedia article as well, then you have already glimpsed at what happened almost half the life of our Universe ago and at least a billion years before our Solar System first formed. That very same property of space that gives the center of our galaxy an extra boost of gravitational effect from the invisible or "dark" matter of space, gives the large voids between visible, physical objects a very highly excited energy state. The farther away from physical objects the space is, the less like matter and more like energy the space becomes and behaves. See dark energy, or as I call it, "spatial energy". As space expands, the structure of space continues to increase. Six billion years ago the stretched volume of expanded space reached a "critical" level. At that level the immediate effect on the entire Universe was for it to begin to expand faster and faster, and its expansion rate may still be accelerating.
And therein lies a constant, and it is a cosmological one!
You cannot be certain about uncertainty.
It's not the School of Uncertainty that people hate, it's the principle of the thing.
There really is only one thing in this Universe we can be certain about: that the Universe is an extremely violent and uncertain place. Other than that, we all live in a world of uncertainty, and we cope with that uncertain world by harboring illusions that our lives are filled with certainty – certainty about practically everything – certainty that makes us feel safe, secure. We are so deluded by our certainty(ies) that it is actually very difficult, even for trained scientists, to get a firm grasp on the UP (Uncertainty Principle). Most of us just don't want to. Many bad things have been said about Kepler due to his astrology readings for friends and acquaintances in order to make ends meet. But Kepler was a true scientist who, when his and Brahe's calculations showed that planetary orbits around the Sun were indeed not perfect circles as his religion prescribed but instead ellipses, his religious ties and binds caused him to agonize over the results for a long time. In the end, Kepler's scientific training won, and he published his amazing and irreverent findings.
In a similar manner, even trained scientists to this day find the UP to be a formidable challenge, although their training fortunately and finally does usually surpass their illusions of certainty. So why is the UP such a big deal? It's a big deal because it forms the basis of any proper and correct understanding of Nature and the Universe. We at some point absolutely must rise to the realization that we cannot possibly understand our Earth, its peoples and the Universe, nor ourselves, unless we find a way to meet the challenges of uncertainty. It's truly a chaotic enterprise and, as a scientific endeavor, well worth the effort.
For a long time, there has been a lot of speculation about the first few moments of the Big Bang. It seems that what is called "physics", even Einsteinian physics, breaks down in our understanding of those first few moments. A specialty part of physics, particle physics, had to become involved. At first they concentrated just on the BB, and then in 1955, a theoretical physicist by the name of John Wheeler extended quantum mechanics (QM) to all of space, not just to the first moments of the BB. Wheeler devised the QM concept of quantum foam and conceptualized it as the foundation of the fabric of the Universe. The UP was applied to all of space-time to describe the constant construction and annihilation of quarks or quark-like particles with the ensuing energies given off, and with the invisible, mass-like gravitational properties that are sensed near large clumps of faraway matter.
Matter and energy
We are led then to conclude that there is indeed a different kind of matter and energy in the Universe. Since this sheds light on those things, we should no longer refer to them as "dark matter" and "dark energy", so I call them "spatial matter" and "spatial energy" in deference to Einstein's idea that "physical objects are not in space, but these objects are spatially extended".[Einstein's original emphasis]
So there is more to space-time than meets the eye. The properties of space are such that the closer it is to clumps of visible matter, the more like matter it behaves, and the farther away space is from clumps of visible matter, the more like energy it behaves. When visible matter is clumped together, then space adds to the gravitational effects. Out in the voids between clumps of matter, such as galaxies and galaxy clusters, the energy that is space furnishes the power that drives the accelerated expansion of the Universe.
For about the first eight billion years after the BB, the growing spatial energy was weaker than the overall gravitational effect and the Universe's expansion rate became slower and slower. Had gravity slowed and stopped the initial expansion before overall spatial energy had increased to the critical point, then the Universe would have begun to contract and would have returned from whence it came. The expansion did (fortunately for us) reach a certain critical point such that the volume of space – along with the energy of space – became large enough to overcome the overall gravitational effect of both visible and spatial matter, and to this day spatial energy continues to grow and drives the accelerated expansion of the Universe.
To BB or not to BB
(Sorry, couldn't resist.) All Shakespearean stutterings aside, the question remains: Was there really a Big Bang? a beginning of all space? and especially a beginning of all time? It's definitely attractive to think that Lemaître's primal atom was the beginning of all things; however, I am suspicious on several levels. He was a Catholic priest as well an an astrophysicist, so his "primeval atom" or "cosmic egg" was his stab at the Truth that would satisfy both his religious and his scientific leanings.
While Albert Einstein's initial disgust for Lemaître's theory may very well have had something to do with Lemaître's youth, his unproved science "status" and his religious background, I think Einstein probably should have continued to trust his initial instincts. Instead, he later changed his mind and supported the Big Bang theory of the beginning of the Universe. After all, the CMB had been discovered after it had been specifically predicted years before, and that was a colorful feather in the cap of the BB theory. It pointed to just that type of event nearly 14 billion years ago. Study of redshifts also depicts an expanding Universe, either first slowing and then accelerating or expanding at a steady rate. What else could have happened but the very beginning of time and space?
Everything "breathes". By that I mean that all things including inanimate objects contain parts that vibrate. So it would be more precise to say "everything vibrates". Perhaps the Universe, which is full of things that vibrate, perhaps it vibrates too? A look at the image shows that spatial energy, which is the power that drives the expansion of the Universe, has increased to about 2/3 and appears from the evidence to be still on the increase. The only thing that can be envisioned at this point that would slow and reverse that would be increasing mass. Up until six billion years ago, gravity, a product of mass, appears to have been stronger than spatial energy, so the expansion of space was much slower. In the present, this has changed so that spatial energy is the stronger of the two. In the future, if mass and gravity continue to increase, and that increase again surpasses the strength of spatial energy, the Universe will begin to contract. It may then continue to contract until it is once again almost down to the size of a grain of sand, at which point matter will have broken up, gravity will be minimal and spatial energy will take the opportunity to increase again. The Universe begins a new expansion and the cycle repeats itself.
Fortunately(?), the period of the vibration of the Universe must be exceedingly long, on the order of, say, 30–50 billion years. Compared with the breathing rate of living things, or the frequencies of electricity and light, or even the orbital periods of planets around stars, stars around galaxy centers, and galaxies around cluster centers, one cycle per 40 billion years makes the tortoise look like a photon! It would be incredibly great if there were a way for us to measure the mass, and therefore gravity, of the Universe as a function of time. As the evidence looks now, it would be so easy to suggest that the Universe is in inflationary-runaway mode, with spatial energy ever increasing faster and faster and no end in sight. We must find a way to falsify that and show that the Universe, like everything else, vibrates or "breathes".
The situation of the gravity
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Actually, the "situation" is our situation, the one we all have in common. It is the Universe, and unfortunately, none of us including the smartest of us, those trained scientists, none of us understand "the situation of the gravity" (let alone the gravity of the situation). But we have to keep trying. Newton didn't understand it; the best he could do was attribute gravity's cause to God, or so he wrote in a letter to a friend, but of course he never revealed that publicly. Einstein's general theory of relativity (GR or GTR) was all about gravity, and a century of study has yet to reveal all the details of what he meant. It's fair to say that the situation of the gravity was revealed by Einstein, and all we have to do is study his descriptions and equations more deeply to learn more about it.
I'm still at it. For decades scientists have sought to unify GR gravity with quantum gravity, respectively the "large" arena and the "small" arena. But is this necessary? Yes. We look at the large, for example an Elm or Oak tree, and we can understand a lot about it just by viewing things about it on the large scale. However we can't know everything about a tree until we get a microscope out and study its leaves and wood and roots on a small scale. We do this to know all about the tree, and we must do this for gravity, as well, if we want to know all about gravity.
It is important to know why large-scale gravity is so different from quantum gravity and if there is a way we can understand how it is that general relativity's gravity and quantum mechanics' gravity can both be successful descriptions of the same thing. The tree analogy may help, because while we can understand the tree better by studying it on both large and small scales, we know that the cells of a leaf are just part of the tree, a small part. In the same manner, the things we find in a study of quantum gravity (QM) and a study of large-scale gravity (GR) are just parts of the huge "tree" of gravity. Those parts work together to make up the whole that is gravity. And the whole just might be greater than the sum of its parts, a "synergy", very much like a tree is.
This section needs expansion. You can help by adding to it.
If we accept that space itself begins to take on properties of matter when it is near visible matter, and the farther away from visible matter space is, the less it shows properties of matter and the more it may exhibit properties of energy, then one of the first conclusions to be drawn would be that space itself is not static, but instead it is a dynamic medium that might very well be the cause of enigmatic gravity. This readily leads to the question, "How exactly would the medium of space be associated with the property of mass we call 'gravity'?" Have you ever heard of "flowing space"?
Because particle physics, and therefore quantum mechanics (QM), has become crucial to an understanding of cosmology, it is important to speculate about the cloud of incompatibility that physics cannot seem to penetrate. Scientists see Einstein's relativity as incompatible with QM. This was broached earlier in regard to the problem of quantum gravity vs. relativistic gravity, and a comparison with a tree was mentioned. There shouldn't be this incompatibility between two valid and viable working theories, and to my thinking, they are no more incompatible than the microscopic study of a tree is to the large-scale study of that tree. Just as with QM and relativity, the small- and large-scale studies of a tree might seem incompatible simply because they are so different. However, they are still valid and viable studies of the tree. There really is no incompatibility between relativity and QM. They are simply two different ways to study the Universe. They both work, that is, they both yield positive results when tested, and even with all the puzzling properties of QM, you and I would not be able to do what we do on our computers if it were not for the positive results of QM testing.
This section needs expansion. You can help by adding to it.
To illustrate why QM and relativity are considered incompatible, there is one particular experiment that pretty much says it all, the one that results in the double-slit problem. To explain the DSP, we begin with a device that shoots out tennis balls at a wall that has two openings or slits. Beyond that wall is a solid wall where the tennis balls hit and bounce off. The relativistic reality is that if the balls were powdered to leave marks on the second wall where they hit it, then there will be two places on that wall that will show the hits... and only two. Can you picture it? The pitcher device spewing out tennis balls one after another – some of the balls going through the right slit and some through the left – and those balls that get through the slits go on to make two powdery areas on the second wall. So to see if this relativistic (large-scale) idea works on the QM scale, experimenters used electrons in place of tennis balls. They fully expected (as anyone would) that those electrons, which we all thought of only as tiny subatomic particles, would do the same thing the tennis balls did and leave two (and only two) areas on the wall beyond the slits.
The pattern left on the wall by the electrons that went through the two slits looked very different than expected. Instead of just two areas of the wall showing electron "bounces", there was an "interference" pattern on the wall that would be expected from waves, not from particles. As unsettling as this was at first, scientists took this in stride and explained that electrons are indeed particles, but they also demonstrate wave-like properties – they are both particles and waves. So that wasn't much of a problem.
Scientists wanted to view the electrons as they went through the slits, so they set up detectors near the two slits to "watch" the electrons go through. And now we get to the real mystery... the electrons no longer appeared as waves, but had left a particle-like pattern just like the tennis balls. When the detectors were turned off, the electrons acted like waves again. It was as if the very act of observing the electrons was all it took to make them change from waves to particles.
At first glance, the title of this section may appear very speculative; however, it's not as though we are unfamiliar with the term negative time (I was surprised to see that term redlinked, and so I created a redirect). What does "negative time" mean? Does it infer that time may move backwards? Could it be just an imaginative direction on some sort of number line? It is my own contention that the concept of negative time will eventually solve most if not all of the riddles that surround the quantum physics problem of what happened in the very first few moments of the Big Bang.
In mathmatics, real numbers include negative numbers, so –5 is a "real" number. A familiar subject is that of negative temperature where heat can be lost as cold gets colder than zero degrees on the Celsius (°C), Fahrenheit (°F) and even the Kelvin (°K) temperature scales. Negative temperatures are very real to those who have experienced them or worked with them. In Christian terminology there is the concept of Anno Domini, which is medieval Latin for "in the year of the Lord". To Christians, then, all times before the birth of Jesus Christ are expressed as negative time (BC or BCE). The Greek philosopher, Socrates, was for example alive during the years –470 to –399, or about seventy years.
So the concept of "negative time" is not an unfamiliar idea. Indeed it took the imaginative mind of Georges Lemaître to dream up the expansion of space, and then to reverse that expansion and go back in time to a compressed beginning of the Universe – to envision negatively moving time – then to reverse time again and begin the Universe with a "Big Bang" expansion. We need to once again apply the concept of "negative time" to the "beginning of time and space", because the overwhelming enigma of "zero", in this case "zero time" (and "zero space"), gives us seemingly insurmountable challenges. And such challenges become easier when zero is not such a hard and fast "wall" or stopping point. When we finally and earnestly apply the concept of negative time to the Big Bang, many of its puzzles will be solved.
Expanding? or stretching
Maybe the "expansion" of the Universe is a poor description that should be replaced in our minds by more of a "stretching" of the Universe? Yes, I know – the difference between "expanding" and "stretching" might not be readily apparent. So the first question that must be answered is...
What's the diff?
Imagine that you have two identical tape measures. You keep one in your pocket and travel to a galaxy far away. You clip your second tape measure to the center of that faraway galaxy and travel back to the Milky Way. The distance you measure between the galaxies is one billion light-years. You keep an eye on your stretched out tape measure, and you see that even over long periods of time, the distance between the galaxies does not change – it stays the same, right at one billion light years. An "expanding" Universe gives the idea that the distance between the galaxies increases over time, but you have seen that the distance remains the same.
Then you get your other tape measure out of your pocket, and when you compare it to your stretched out tape measure, you take note of a strange thing. The units on the tape measure that you stretched between the galaxies are now twice as long as the units on the other tape measure. So while you have kept an eye on your stretched out tape measure and have not noted any change in distance between the galaxies, the space between the galaxies has stretched to twice as long. That's how the difference between expanding and stretching has been explained to me. I need a pizza.
- Holographic principle
- Inflation theory
- Light cone
- Pale Blue Dot
- Pizza – my favorite place
- by Ellsworth
- Hille (2016)
- Battersby (2006)
- Van Flandern (2002)
- Einstein (1961)
- Augenstein (2016)
- ESA (2013)
- Wolter (c. 1990)
- Augenstein, Seth (21 October 2016). "Universe Expanding at Constant Rate – Not Accelerating, Says Study". www.laboratoryequipment.com. Retrieved 2016-12-27 – so, it is apparent also that after the first extreme inflationary period, the Universe may have expanded at a steady, constant rate, and nothing in particular may have happened 6 billion years ago.
- Battersby, Stephen (4 September 2006). "Introduction: Cosmology – space". New Scientist. Retrieved 2016-10-17.
- Einstein, Albert (1961) . Relativity – the Special and the General Theory. Translated by Lawson, Robert W. (15th ed.). Crown Publishers. p. vi.
- ESA (21 March 2013). "Planck reveals an almost perfect Universe". Planck. Retrieved 2013-03-21.
- Hille, Karl, ed. (13 October 2016). "Hubble Reveals Observable Universe Contains 10 Times More Galaxies Than Previously Thought". NASA. Retrieved 2016-10-17.
- Van Flandern, Tom (2002). "The Top 30 Problems with the Big Bang theory". www.spaceandmotion.com. Retrieved 2016-10-17.
- Wolter, Gordon (c. 1990). "Continuous Big Bang (CBB) Universe". Retrieved 2016-10-17 – One distinct possibility
- The Scale of the Universe
- An ultradeep image that's *full* of galaxies!
- The Smallest Bits of Space
- Secret Worlds: The Universe Within – a.k.a. "Powers of Ten"
- The Hubble Deep Field: The Most Important Image Ever Taken
- An Atlas of the Universe
- "Gravitational spatial flow" – Google search (with quotational marks)