- 2849 - COSMIC INFLATION- explaining the Big Bang? Cosmic inflation is revealing answers has only raised more questions. The puzzles that have arisen this time, however, may truly never be solved. If that information is no longer present in our Universe, it will take a revolution to solve the greatest puzzle of all: “where did all this come from“?
-------------------- 2849 - COSMIC INFLATION- explaining the Big Bang?
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- The 20th century brought us General Relativity, Quantum Physics, and the Big Bang, all accompanied by spectacular observational and experimental successes. But, for the Big Bang, it left some unexplained problems that required us to go farther.
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- We found an uncomfortable conclusion that we are still reckoning with today: any information about the beginning of the Universe is no longer contained within our observable cosmos. Here’s the disconcerting story.
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- In the 1920s our conception of the Universe changed forever as two sets of observations came together in perfect harmony. For the past few years, scientists led by Vesto Slipher had begun to measure spectral lines, emission and absorption features, of a variety of stars and nebulae.
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- Because atoms are the same everywhere in the Universe, the electrons within them make the same transitions, they have the same absorption and emission spectra. But a few of these nebulae, the spirals and ellipticals had extremely large redshifts that corresponded to high recession speeds, faster than anything else in our galaxy.
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- Starting in 1923, Edwin Hubble and Milton Humason began measuring individual stars in these nebulae, determining the distances to them. They were far beyond our own Milky Way, millions of light-years away in most instances.
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- When you combined the distance and redshift measurements together, it all pointed to one inescapable conclusion that was also theoretically supported by Einstein’s General theory of Relativity, the Universe was expanding. The farther away a galaxy is, the faster it appears to recede from us.
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- If the Universe is expanding today, that means that all of the following must be true:
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---------------------- The Universe is getting less dense, as the (fixed amount of) matter in it occupies larger and larger volumes.
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--------------------- The Universe is cooling, as the light within it gets stretched to longer wavelengths.
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--------------------- Galaxies that aren’t gravitationally bound together are getting farther apart over time.
- Those are some remarkable and mind-bending facts, as they enable us to extrapolate what’s going to happen to the Universe as time marches inexorably forwards. But the same laws of physics that tell us what’s going to happen in the future can also tell us what happened in the past, and the Universe itself is no exception.
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- If the Universe is expanding, cooling, and getting less dense today, that means it was smaller, hotter, and denser in the distant past.
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- The big idea of the Big Bang was to extrapolate this back as far as possible, to ever hotter, denser, and more uniform states as we go earlier and earlier. This led to a series of remarkable predictions, including that:
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------------------------- More distant galaxies should be smaller, more numerous, lower in mass, and richer in hot, blue stars than their modern-day counterparts,
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------------------------- There should be fewer and fewer heavy elements as we look backwards in time,
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------------------------ There should come a time when the Universe was too hot to form neutral atoms and a leftover bath of now-cold radiation that exists from that time,
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------------------------- There should even come a time where atomic nuclei were blasted apart by the ultra-energetic radiation leaving a relic mix of hydrogen and helium isotopes.
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- All of these predictions have been observationally confirmed, with that leftover bath of radiation, originally known as the “primeval fireball” and now called the “cosmic microwave background“, discovered in the mid-1960s.
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- We can extrapolate the Big Bang all the way back, arbitrarily far into the past, until all the matter and energy in the Universe is concentrated into a single point.
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- The Universe would reach infinitely high temperatures and densities, creating a physical condition known as a “singularity“, where the laws of physics as we know them give predictions that no longer make sense and cannot be valid anymore.
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- The Universe began with this Big Bang some finite time ago, corresponding to the birth of space and time, and that everything we’ve ever observed has been a product of that aftermath.
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- We had a scientific answer that truly indicated not only that the Universe had a beginning, but when that beginning occurred. In the words of Georges Lemaitre, the first person to put together the physics of the expanding Universe, it was “a day without yesterday.”
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- Only, there were a number of unresolved puzzles that the Big Bang posed, but presented no answers for. Why did regions that were causally disconnected, had no time to exchange information, even at the speed of light, have the same temperatures as one another?
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- Why were the initial expansion rate of the Universe (which works to expand things) and the total amount of energy in the Universe (which gravitates and fights the expansion) perfectly balanced early on to more than 50 decimal places?
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- Why, if we reached these ultra-high temperatures and densities early on, are there no leftover relic remnants from those times in our Universe today?
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- Then, in late 1979, a young theorist named Alan Guth had a spectacular realization that changed history. His new theory was known as “cosmic inflation“, and postulated that perhaps the idea of the Big Bang was only a good extrapolation back to a certain point in time, where it was preceded and set up by this inflationary state.
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- Instead of reaching arbitrary high temperatures, densities, and energies, inflation states that:
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------------------------- The Universe was no longer filled with matter and radiation,
but instead possessed a large amount of energy intrinsic to the fabric of space itself,
which caused the Universe to expand exponentially where the expansion rate doesn’t change over time,
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------------------------- Which drives the Universe to a flat, empty, uniform state,
until inflation ends.
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------------------------- When it ends, the energy that was inherent to space itself, the energy that’s the same everywhere, except for the quantum fluctuations imprinted atop it, gets converted into matter and energy, resulting in a hot Big Bang.
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- This offered a plausible physical explanation for the observed properties the Big Bang alone could not account for. Causally disconnected regions have the same temperature because they all arose from the same inflationary “patch” of space.
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- The expansion rate and the energy density were perfectly balanced because inflation gave that same expansion rate and energy density to the Universe prior to the Big Bang. And there were no left over, high-energy remnants because the Universe only reached a finite temperature after inflation ended.
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- Inflation also made a series of novel predictions that differed from that of the non-inflationary Big Bang, meaning we could go out and test this idea. As of today, in 2020, we’ve collected data that puts four of those predictions to the test:
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------------------------ The Universe should have a maximum, non-infinite upper limit to the temperatures reached during the hot Big Bang.
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------------------------ Inflation should possess quantum fluctuations that become density imperfections in the Universe that are 100% adiabatic with constant entropy.
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------------------------ Some fluctuations should be on super-horizon scales: fluctuations on scales larger than light could have traveled since the hot Big Bang. Those fluctuations should be almost, but not perfectly, scale-invariant, with slightly greater magnitudes on large scales than small ones.
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- The fluctuations from inflation get stretched across the Universe, creating overdensities. With data from satellites like COBE, WMAP, and Planck, tested only inflation yields predictions that are in line with what we’ve observed.
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- But this means that the Big Bang wasn’t the very beginning of everything; it was only the beginning of the Universe as we’re familiar with it.
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- Prior to the hot Big Bang, there was a state known as cosmic inflation, that eventually ended and gave rise to the hot Big Bang, and we can observe the imprints of cosmic inflation on the Universe today.
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- Only for the last tiny, minuscule fraction of a second of inflation. Only, perhaps, for the final 10^-33 seconds of it can we observe the imprints that inflation left on our Universe.
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- It is possible that inflation lasted for only that duration, or for far longer. It’s possible that the inflationary state was eternal, or that it was transient, arising from something else. It’s possible that the Universe did begin with a singularity, or arose as part of a cycle, or has always existed.
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- But, that information doesn’t exist in our Universe. Inflation by its very nature erases whatever existed in the pre-inflationary Universe.
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- The quantum fluctuations that occur during inflation getting stretches across space.
In many ways, inflation is like pressing the cosmic “reset” button. Whatever existed prior to the inflationary state, if anything, gets expanded away so rapidly and thoroughly that all we’re left with is empty, uniform space with the quantum fluctuations that inflation creates superimposed atop it.
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- When inflation ends, only a tiny volume of that space, somewhere between the size of a soccer ball and a city block, will become our observable Universe. Everything else, including any of the information that would enable us to reconstruct what happened earlier in our Universe’s past, now lies forever beyond our reach.
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- It is one of the most remarkable achievements of science that we can go back billions of years in time and understand when and how our Universe, as we know it, came to be this way.
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- Revealing those answers has only raised more questions. The puzzles that have arisen this time, however, may truly never be solved. If that information is no longer present in our Universe, it will take a revolution to solve the greatest puzzle of all: where did all this come from?
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----------------------------------- here are some other reviews;
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- 2236 - COSMIC INFLATION - expanding over 14 billion years. Cosmic Inflation has been expanding the universe for 14 billion years. Science has discovered that the Universe is expanding at an ever increasing acceleration today. If we run time backwards the universe must have started at a point. This point of a compact universe is called a singularity. The whole Universe compacted into a single point of energy.
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- 2164 - The Universe is 13.8 billion years old. We know how fast it has been expanding. We know that the Universe is 31 % matter of which is only 5% is Ordinary Matter. We know that the other 23% matter is invisible Dark Matter that we know is there but we do not understand what it is. The rest is energy of some sort that remains another mystery that is creating and accelerating the expansion, we call it Dark Energy.
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- 1680 - Cosmic Inflation theory assumes that everything started out as quantum fluctuations that got amplified into cosmic inflation. This is evidenced by systematic analysis down to 5-sigma accuracy and using two different modes of detection.
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- 1824 - Today inflation is used to explain why space is flat. Flat meaning the universe has the critical density to just balance gravity pull and Dark Energy push.
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- 1586 - The critical density variations of the cosmic background re 113,000 lightyears across.
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- 1305 - Cosmic harmonics tell us that the Cosmic background radiation started 115,000 years before and ended 487,000 years after the Big Bang.
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- 836 - The Hubble Constant of expansion is 49,000 miles per hour per million lightyears of separation.
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- There are also several reviews about the Cosmic Microwave Background radiation.
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- September 30, 2020 2849
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--------------------- --- Thursday, October 1, 2020 ---------------------------
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