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---------------------- 2262 - UNIVERSE - how fast is it expanding?
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- In the beginning, all of space rang like a bell. After the big bang all of space rang like a bell. The universe was filled with a plasma energetic soup of particles and radiation. Although that plasma was remarkably smooth, it wasn’t completely smooth. There were slight density and pressure gradients that pushed material around causing this ringing.
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- The ringing happened everywhere, so intensely that we can still sense it 13.8 billion years later. It has been detected directly in the cosmic microwave background, the afterglow left over from the big bang. It has been closely analyzed using the same basic physics used to study the structure of the sun.
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- This primordial reverberation is so well measured and modeled that it has been used to deduce the precise rate at which the universe is expanding. The rate of expansion is known as the Hubble Constant. The Hubble Constant rate of expansion is the cornerstone of our understanding of the size, age and structure of the Universe.
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- The Hubble Constant value derived by extrapolating from these ancient sound waves should match up exactly with the value derived from independent studies of the light from distant stars and galaxies. However, a series of studies show the two approaches yield a vexing disagreement.
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- To figuring out why space is not ringing the way they expected could lead cosmologists to previously unknown physics, potentially revealing a whole new aspect of reality. Dark Matter and Dark Energy are at the center of this unknown physics.
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- Following the big bang, sound waves were produced by the intermingling of light and matter traveled freely through the hot, plasma-filled universe. After some 380,000 years matter cooled enough to form atoms, decoupling from light and dampening the sound waves. Suddenly, the ringing stopped, impressing a final, frozen pattern of sound waves into the escaping light, which we see today in the cosmic microwave background.
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- The light traveling through the expanding universe has been stretched from gamma ray radiation to the broader wavelengths of microwaves. This is the microwave background radiation that we can see today.
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- The sound horizon defines the size of these final waves. You can determine the qualities of a bell from the way it rings. A small glass bell will sound entirely different than a large brass bell. Researchers can infer the precise properties of the universe from its sounds as recorded in this microwave background.
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- That is how they can declare the cosmos consists of 4.8 percent ordinary matter, 26 percent of the unseen stuff known as dark matter and a 69 percent dark energy, an mysterious anti-gravitational force that stretches empty space apart. This force is constantly accelerating the expansion of the Universe. The galaxies are even disappearing beyond the horizon, because their light will never reach us.
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- In 2015 results indicated the universe is expanding at a rate of 67.8 kilometers per second per mega parsec. A “megaparsec” is a unit of distance equal to 3.26 million light-years. Translating to more familiar units this equates to 49,000 miles per hour expansion for every million lightyears of distance.
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- However, we get a different answer when studying the expansion of the universe in a different way. When measuring variable stars or supernova explosions of known distance and then directly measuring how quickly they are moving away from us. This alternative method is called the “distance ladder” method.
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- Instead of 67.8 this new calculation answer is 73. The two numbers agree to within 10%. But, why do they disagree at all? They both claim to be precision measurements? There is nothing obvious that could be causing the 10% difference.
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- Cosmologists on both sides are also looking to outside groups for guidance. A University of California study that looks at how light is bent by distant galaxies gives a Hubble constant of 72.5, close to the distance-ladder result.
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- Another equally convincing study looking at how primordial sound waves affect the distribution of galaxies in the universe gives a constant of 67, not 72.5.
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- Everything we know about the origin of the sound horizon depends on a theoretical model of how the universe behaved during its unseen initial 380,000 years. If the models are wrong and the size of the sound horizon is different than what they predict, that adjustment would change all of the numbers derived from it, including the Hubble constant.
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- A cosmological solution comes with a smaller sound horizon. Shrinking by just 7%, and both studies agree with one another. The problem is determining what could account for such shrinking.
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- The most convincing explanation is that the early universe was expanding slightly faster than expected. If so, it would have cooled more quickly and frozen the sound horizon in place a little sooner. In that case the sound horizon would be smaller than the one theorists have plugged into their current models.
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- Dark Matter is the term for invisible components of the universe that do not interact with radiation in any way. Researchers already invoke dark matter to explain galactic motion and dark energy to account for the universe’s accelerating expansion.
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- The divergent measurements of the Hubble constant may be the first sign of the existence of a third dark component. Something dark that added to the energy of the early universe, hastening its expansion and changing the pitch of its sounds. A related possibility is dark energy has more than one form, or changes over time in complicated ways.
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- This Hubble Constant conflict may be bringing into view an aspect of the universe that had completely eluded detection until now. The visible part of the universe contains many different types of particles and forces. The Dark Matter and Dark Energy components of the universe may be complicated as well?
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- To turn this into a concrete scientific question we need new observations of the early universe. Here are some astronomers re working on: There are the South Pole Telescope in Antarctica and the Atacama Cosmology Telescope in Chile that will further probe the sound horizon. There is also a program designed to map the polarization of the microwave sky with great sensitivity. Studies of gravitational waves will also provide a completely independent way to assess the true Hubble value.
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- There is a lot going on. Stay tuned, more discoveries to follow. Who said explaining the universe was going to be easy. The most amazing part is that we are here to even ask the questions.
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- See also 2253 - Expanding universe, how can it be flat? What is beyond the edge?
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- 2230 - Te story beginning to end. How to get the age of the universe from the rate of expansion.?
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- 2202 - The structure of the universe?
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- 2196 - Discovering the age of he universe?-
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- 2195 - How are Cepheids used in the calculation of the age of the universe?
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- 2194 - How the Universe was born?
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- 2193 - What is the universe expanding in to?
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- 2192 - The universe as we know it?
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- 2177 - The universe by the numbers? Mass, density, diameter?
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- 2167 - Planck satellite measures the cosmic microwave background?
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- 2166 - History of the universe from picoseconds to years, birth to now. 17 pages.
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- 1821 - Describing the universe in math . His review list 15 more reviews available on the Universe.
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- 2086 - Puzzles in astronomy?
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- 2075 - Too weird to ponder?
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- 2066 - Extremes in the universe?
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- 2027 - Lists more reviews about the universe you live in?
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- 1991 - What are the odds you are able to read this?
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- 1665 - How the universe started?
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- 1225 - Is the universe really a computer?
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- 842 - Pressed for time?
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- 342 - The whole shebang.
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- February 8, 2019
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-------------------------- Friday, February 8, 2019 --------------------------
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