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-------------------- 2569 - UNIVERSE - what is the fate of the universe?
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- I know the Universe’s fate is a long time from now. But, wouldn’t you like to know what is ultimately going to happen to this Universe we are living in. Of course, an even deeper question is how did we get here in the first place. Although the answer to these ancient questions is still unknown, there are strong observational hints toward a clear future for this Universe.
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- That concept, in and of itself, would have surprised most astronomers who thought about the subject during the past 100 years.
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- For most of recorded history, the answer was simple: The universe has always existed and always will. Few people challenged the dogma or even suspected it might not be true.
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- That challenge started to change in the 1910s with the publication of Albert Einstein’s general theory of relativity. The first models developed from Einstein’s equations showed that the universe does not have to be static and unchanging, but it can evolve over time.
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- In the 1920s, Belgian priest and astronomer Georges Lemaître developed the concept of the Big Bang. Coupled with Edwin Hubble’s observations of an expanding universe, astronomers were coming around to the idea that the universe had a beginning , and, could have an end as well.
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- It was not until the 1960s that strong observational evidence supported the Big Bang. The two breakthroughs were the discovery of the cosmic microwave background radiation by radio astronomers Arno Penzias and Robert Wilson, and the realization that active galaxies existed preferentially in the distant universe. This also meant they existed when the cosmos was much younger than it is today, and so the universe has been evolving.
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- By the 1980s, most astronomers were convinced that the universe began with a bang, but they had little clue how it would end. There were basically three scenarios, all based on how much matter the universe contained.
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- If the cosmos had less than a certain “critical density“, the universe was “open” and would expand forever; if the density were above the critical value, the universe was “closed” and the expansion ultimately would stop and then reverse, leading to a “Big Crunch”; if the universe were at the critical density, it was “flat” and expansion would continue forever, but the rate would eventually slow to zero.
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- Observations seemed to favor an open universe, with astronomers finding only about 1 percent of the matter needed to halt expansion. But scientists knew that a lot of dark matter must exist. This was non-luminous material that nevertheless has gravitational pull similar to normal matter.. Would it be enough to stop the expansion? No one knew.
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- Matters grew more interesting in the 1980s when Alan Guth proposed his inflation hypothesis. This theory says a brief period of hyper-expansion in the universe’s first second made the universe “flat“. Astronomers eagerly accepted inflation because it solved some of the problems with the Big Bang model.
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- But the most remarkable development came in the late 1990s. Astronomers using the Hubble Space Telescope and several large ground-based instruments were examining dozens of distant type Ia supernovae. This variety of exploding star arises when a white dwarf in a binary system pulls enough matter from its companion star to push it above 1.4 solar masses. At that stage, the white dwarf can no longer support itself, which triggers a runaway nuclear chain reaction that causes the star to explode with a calculated amount of energy.
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- Because all these exploding “white dwarfs” have the same mass, they all have the same approximate peak luminosity. Simply measure how bright the type Ia supernova appears, and you can calculate its distance. Brightness decreases as the square of the distance traveled.
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- To their surprise astronomers found the most distant supernovae were fainter than their distances would imply. The only way this makes sense is if the expansion of the universe is speeding up. Gravity works to slow down the expansion, and did so successfully for billions of years. But it now appears we have entered an era where gravity is no match for the mysterious force causing the expansion to accelerate.
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- The force may take the form of “dark energy“, quintessence, the cosmological constant, or some other strange name with a different effect. But the results of this energy that makes up 68 percent of the mass-energy content of the cosmos will lead to unending expansion. If it keeps operating as it has, a “Big Rip” may be in our future. If not, a “Big Crunch” could still be ahead.
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-- Searching for knowledge is like picking up little pebbles on the beach with the whole ocean of the unknown out in front of us. If you want to search more here are some other Reviews about the universe:
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- 2449 - Strange universe is expanding forever.
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- 2459 - Measuring the universe.
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- 2476 - Determining the age of the universe?
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- 2478 - What is the shape of he universe?
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- 2504 - Measuring the universe from the biggest to the smallest.
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- 2524 - What is the structure of the universe?
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- 2536 - Explaining the universe is explaining the impossible.
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- 2551 - Exploring the age and size of the universe?
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- 2552 - Studying the birth of the universe.
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- 2553 - Is the Universe homogeneous?
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- 2447 - UNIVERSE - how did it all happen? 13.8 billion years ago the universe started as the Big Bang when space itself rapidly began expanding. At the time the observable universe, which included enough materials to build at least 2 trillion galaxies, fit into a space less than a centimeter across. Today the observable universe is 93 billion light-years across and still expanding.
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- 2439 - UNIVERSE - discovering the expansion? One of the biggest scientific surprises in astronomy was the recent discovery that space itself is expanding. And, expanding the Universe at an ever increase rate. Distant galaxies recede from us and from one another more quickly than the nearby ones, as though the fabric of space itself is being stretched by some dark form of energy.
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- 2432 - UNIVERSE - expanding space. If you were born when the Universe was ten times its current age, our local group of galaxies would merge into one and would be the only galaxy you could see in the Universe for trillions of light years.
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- 2419 - and - 2393 - Age of the Universe
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- 2412 - Comprehending the expanding Universe.
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- 2394 - Wrap your mind around the Universe.
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- 2348 - The Universe from start to finish. 13 pages.
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- 2347 - The Island Universe
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- 2335 - The Universe almost did not happen.
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- 2334 - How is it expanding?
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- 2262 - How fast is it expanding? Also list more reviews about the Universe. It is a big topic. In fact it is the biggest.
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- December 26, 2019 2569
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--- to: ------ jamesdetrick@comcast.net ------ “Jim Detrick” -----------
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--------------------- Saturday, December 28, 2019 --------------------
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