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Thread: Astronomy

  1. #1486
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    https://www.space.com/38976-jupiter-...tectonics.html

    "The case for plate tectonics on Jupiter's ocean-harboring moon Europa keeps getting stronger.

    Scientists had already spotted geological signs that plates within the moon's ice shell may be diving beneath one another toward the moon's buried ocean. Now, a new study suggests that such "subduction" is indeed possible on Europa and shows how the phenomenon might be happening.

    The new results should intrigue astrobiologists and anyone else who hopes that Earth isn't the only inhabited world in the solar system. [Photos: Europa, Mysterious Icy Moon of Jupiter]

    "If, indeed, there's life in that ocean, subduction offers a way to supply the nutrients it would need," study lead author Brandon Johnson, an assistant professor in the Department of Earth, Environmental and Planetary Sciences at Brown University in Rhode Island, said in a statement.

    Such nutrients include oxidants, electron-stripping substances that are common on Europa's surface and that could help provide an energy source for life, the researchers said. "

  2. #1487
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    https://www.space.com/38982-no-big-b...gy-theory.html

    Exploration of the Big Bang theory. I've always thought this was too simple:

    "Was the universe created with a Big Bang 13.7 billion years ago, or has it been expanding and contracting for eternity? A new paper, inspired by alternative explanations of the physics of black holes, explores the latter possibility, and rejects a core tenant of the Big Bang hypothesis."

  3. #1488
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    This link provides some more details on Neves Bouncing Theory

    "Brazilian physicist Juliano Cesar Silva Neves part of a group of researchers who dare to imagine a different origin. In a study recently published in the journal General Relativity and Gravitation, Neves suggests the elimination of a key aspect of the standard cosmological model: the need for a spacetime singularity known as the Big Bang.

    In raising this possibility, Neves challenges the idea that time had a beginning and reintroduces the possibility that the current expansion was preceded by contraction. "I believe the Big Bang never happened," the physician said, who Works as a researcher at the University of Campinas's Mathematics, Statistics & Scientific Computation Institute (IMECC-UNICAMP) in Sao Paulo State, Brazil.

    For Neves, the fast spacetime expansion stage does not exclude the possibility of a prior contraction phase. Moreover, the switch from contraction to expansion may not have destroyed all traces of the preceding phase.

    The article, which reflects the work developed under the Thematic Project "Physics and geometry of spacetime," considers the solutions to the general relativity equations that describe the geometry of the cosmos and then proposes the introduction of a "scale factor" that makes the rate at which the Universe is expanding depend not only on time but also on cosmological scale.

    "In order to measure the rate at which the Universe is expanding with the standard cosmology, the model in which there's a Big Bang, a mathematical function is used that depends only on cosmological time," said Neves, who elaborated the idea with Alberto Vazques Saa, a Full Professor at IMECC-UNICAMP and also the supervisor for Neves' postdoctoral project, funded by the Sao Paulo Research Foundation -- FAPESP.

    With the scale factor, Big Bang itself, or cosmologic singularity, ceases to be a necessary condition for the cosmos to begin universal expansion. A concept from mathematics that expresses indefiniteness, singularity was used by cosmologists to characterize the "primordial cosmologic singularity" that happened 13.8 billion years ago, when all the matter and energy from the Universe were compressed into an initial state of infinite density and temperature, where the traditional laws of physics no longer apply.

    The Big Bang Theory has its origins in the late 1920s when US astronomer Edwin Hubble discovered that almost all galaxies are moving away from each other at ever-faster velocities.

    From the 1940s onward, scientists guided by Einstein's theory of general relativity constructed a detailed model of the evolution of the Universe since the Big Bang. Such model could lead to three possible outcomes: the infinite expansion of the Universe at ever-higher velocities; the stagnation of the Universe expansion in a permanent basis; or an inverted process of retraction caused by the gravitational attraction exerted by the mass of the Universe, what is known as Big Crunch.

    "Eliminating the singularity or Big Bang brings back the bouncing Universe on to the theoretical stage of cosmology. The absence of a singularity at the start of spacetime opens up the possibility that vestiges of a previous contraction phase may have withstood the phase change and may still be with us in the ongoing expansion of the Universe," Neves said.

    Neves conceptualizes that "bouncing cosmology" is rooted in the hypothesis that Big Crunch would give way to an eternal succession of universes, creating extreme conditions of density and temperature in order to instigate a new inversion in the process, giving way to expansion in another bounce.

    Vestiges of contraction

    Black holes are the starting point of Neves' investigations about "Bouncing Universe." "Who knows, there may be remains of black holes in the ongoing expansion that date from the prior contraction phase and passed intact through the bottleneck of the bounce," he said.

    Consisted of the imploded core remaining after a giant star explodes, black holes are a kind of cosmic object whose core contracted to form a singularity, a point with infinite density and the strongest gravitational attraction known to exist. Nothing escapes from it, not even light.

    According to Neves, a black hole is not defined by singularity, but rather by an event horizon, a membrane that indicates the point of no return from which nothing escapes the inexorable destiny of being swallowed up and destroyed by the singularity.

    "Outside the event horizon of a regular black hole, there are no major changes, but inside it, the changes are deep-seated. There's a different spacetime that avoids the formation of a singularity."

    The scale factor formulated by Neves and Saa was inspired by US physicist James Bardeen. In 1968, Berdeen used a mathematical trick to modify the solution to the general relativity equations that describe black holes.

    The trick consisted of thinking of the mass of a black hole not as a constant, as had previously been the case, but as a function that depends on the distance to the center of the black hole. With this change, a different black hole, termed a regular black hole, emerged from the solution to the equations. "Regular black holes are permitted, since they don't violate general relativity. The concept isn't new and has frequently been revisited in recent decades," said Neves.

    Since the insertion of a mathematical trick into the general relativity equations could prevent the formation of singularities in regular black holes, Neves considered creating a similar artifice to eliminate the singularity in a regular bounce.

    In modern science, a theory is worthless if cannot be verified, however beautiful and inspiring it may be. How do you test the hypothesis of a Big Bang that did not start with a singularity?

    "By looking for traces of the events in a contraction phase that may have remained in the ongoing expansion phase. What traces? The candidates include remnants of black holes from a previous phase of universal contraction that may have survived the bounce," Neves said.

    Story Source:

    Materials provided by Fundação de Amparo à Pesquisa do Estado de São Paulo. Original written by Peter Moon. Note: Content may be edited for style and length.

    Journal Reference:

    J. C. S. Neves. Bouncing cosmology inspired by regular black holes. General Relativity and Gravitation, 2017; 49 (9) DOI: 10.1007/s10714-017-2288-6

    Fundação de Amparo à Pesquisa do Estado de São Paulo. "Possible vestiges of a universe previous to the Big Bang." ScienceDaily. ScienceDaily, 27 November 2017. <www.sciencedaily.com/releases/2017/11/171127105935.htm>.
    https://www.sciencedaily.com/release...1127105935.htm
    Exeptionally I copied the whole article. The article itself is not available.
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  4. #1489
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    I've never really considered the Big Bang Theory, it seems so abstract, a bit like the religious debates over how many angels can fit onto a pin-head!

    I'm more comfortable with the theory of multiple big bangs, because it remains abstract and so doesn't need to be proved or disproved.

  5. #1490
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    https://www.space.com/39008-bizarre-...atter-sea.html

    "Two enormous galaxies seen merging in the distant universe have astronomers rethinking the leading theory of how galaxies form.

    When the universe was in its infancy, the very first galaxies were tiny "dwarf galaxies" that clumped together to form the larger galaxies seen today. Known as hierarchical formation, this theory suggests that galaxies form in a step-by-step process as smaller galaxies are pulled together by their mutual gravitational attraction.

    But now, the recent discovery of two distant galaxies that are abnormally huge has led astronomers to rethink that theory because it suggests that those dwarf galaxies assembled into large galaxies a lot faster than previously thought."

  6. #1491
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    http://earthsky.org/space/star-seaso...nce-brightness

    "Consider the sky at the opposite time of year. In June, July and August, the evening sky seen from the entire Earth is facing toward the center of the Milky Way galaxy. The galaxy is about 100,000 light-years across, and its center is some 25,000 to 28,000 light-years away. We don’t see into the exact center of the Milky Way, because it’s obscured by galactic dust. But during those Northern Hemisphere summer months (Southern Hemisphere winter months), as we peer edgewise into the galaxy’s disk, we’re gazing across some 75,000 light-years of star-packed space (the distance between us and the center, plus the distance beyond the center to the other side of the galaxy)."

    There is more but if interested visit the link above!

  7. #1492
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    EarthSky is one of my all-time favourite websites to visit. This is about the oldest citizen project: http://earthsky.org/earth/audubons-c...-december-14th

    Audubon Society’s Christmas Bird Count is one of the longest-running citizen science projects in existence. Here’s how to participate (go to website above)

  8. #1493
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    Interesting links, DW, specially the last one that comments on the brightness of the stars:

    "As seen during Northern Hemisphere winter (or Southern Hemisphere summer), the stars seem brighter. Why? It’s partly because – on December, January and February evenings – the part of Earth you’re standing on is facing into the spiral arm of the galaxy to which our sun belongs."

    http://earthsky.org/space/star-seaso...nce-brightness
    "You can always find something better than death."
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  9. #1494
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    About Big Bang. Until a short time ago I didn´t know what it was about. But I am also inclined to think that the origin of the universe was different. Big Bang somehow doesn´t fit whit what one knows about celestial bodies up to now.
    "You can always find something better than death."
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    Personally, I do not believe the big brains are real close yet. One reason for this is that we have not been at it with advanced technology for long enough. Our sample space is too small, to put it in statistical terms. During most of human existence, there might be a strong chance that a shift from contraction to expansion would not even have been noted by big brains, who were busy rubbing sticks together. I take it that now we would note such an occurrence. I am not smart enough to note subtle changes, but there are those about who are. Our sample space is too narrow, though. We have not been at it long enough. Imagine what we might see and figure out after a million years of steady scientific observation, when our sample space was not so small anymore nor statistically so likely to be devoid of big events.

    One keeps hearing that the Webb telescope will transform astronomy again, as the Hubble did in its working life. I hope this is true and that I am still on top of the ground to receive the news.

  11. #1496
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    The International Space Station can be read about here, and there is much information on it: I didn't know i was so big!

    http://www.astronomytoday.com/exploration/iss.html

    On November 2, 2010, the ISS marked its 10th anniversary of continuous human occupation. The ISS team includes the United States, Canada, Japan, Russia, Brazil, and the 11 ESA nations, and the space station has been visited by 202 individuals. Four times bigger than Mir, the ISS is about the size of a football field. The ISS weighs 390,908 kg, or 861,8704 pounds and is larger than a five-bedroom house. Construction on the ISS was essentially completed in 2011. The ISS orbits at 402 kilometers above sea level with a 51.6� inclination, allowing easy crew and supply accessibility and coverage of 85% of Earth. People on Earth can see the ISS pass overhead as a bright point of light, looking similar to an airplane.

  12. #1497
    On the road, but not! Danik 2016's Avatar
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    Quote Originally Posted by desiresjab View Post
    Personally, I do not believe the big brains are real close yet. One reason for this is that we have not been at it with advanced technology for long enough. Our sample space is too small, to put it in statistical terms. During most of human existence, there might be a strong chance that a shift from contraction to expansion would not even have been noted by big brains, who were busy rubbing sticks together. I take it that now we would note such an occurrence. I am not smart enough to note subtle changes, but there are those about who are. Our sample space is too narrow, though. We have not been at it long enough. Imagine what we might see and figure out after a million years of steady scientific observation, when our sample space was not so small anymore nor statistically so likely to be devoid of big events.

    One keeps hearing that the Webb telescope will transform astronomy again, as the Hubble did in its working life. I hope this is true and that I am still on top of the ground to receive the news.
    The new instruments are already transforming astronomy. The sample space, as you call it, is still limited but broadening fastly IMO.
    "You can always find something better than death."
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  13. #1498
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    Quote Originally Posted by Dreamwoven View Post
    The International Space Station can be read about here, and there is much information on it: I didn't know i was so big!

    http://www.astronomytoday.com/exploration/iss.html

    On November 2, 2010, the ISS marked its 10th anniversary of continuous human occupation. The ISS team includes the United States, Canada, Japan, Russia, Brazil, and the 11 ESA nations, and the space station has been visited by 202 individuals. Four times bigger than Mir, the ISS is about the size of a football field. The ISS weighs 390,908 kg, or 861,8704 pounds and is larger than a five-bedroom house. Construction on the ISS was essentially completed in 2011. The ISS orbits at 402 kilometers above sea level with a 51.6� inclination, allowing easy crew and supply accessibility and coverage of 85% of Earth. People on Earth can see the ISS pass overhead as a bright point of light, looking similar to an airplane.
    Just google the Brazilian part in the program:

    "Brazil joined the ISS as a partner of the United States and this included a contract with NASA to supply hardware to the Space Station.[6] In return, NASA would provide Brazil with access to NASA ISS facilities on-orbit, as well as a flight opportunity for one Brazilian astronaut during the course of the ISS programme. However, due to cost issues, the subcontractor Embraer was unable to provide the promised ExPrESS pallet, and Brazil left the programme in 2007.[7] Regardless, the first Brazilian astronaut, Marcos Pontes, was sent to ISS in April 2006 for Expedition 13.[34] This was Brazil's first space traveler and he returned to Earth safely.[34] Marcos trained on the Space Shuttle and Soyuz, but ended up going up with the Russians, although he did work at the U.S. Johnson Space Center after returning to Earth."
    https://en.wikipedia.org/wiki/Politi..._Space_Station

    Marcos Pontes gave several interviews at the time as Brazil´s only space traveler.
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    https://astronomynow.com/2016/07/20/...teroid-impact/

    Around 3.8 billion years ago, an asteroid more than 150 miles across, roughly equal to the length of New Jersey, slammed into the Moon and created the Imbrium Basin — the right eye of the fabled Man in the Moon. This new size estimate, published in the journal Nature, suggests an Imbrium impactor that was two times larger in diameter and 10 times more massive than previous estimates.

    “We show that Imbrium was likely formed by an absolutely enormous object, large enough to be classified as a protoplanet,” said Pete Schultz, professor of Earth, environmental and planetary sciences at Brown University. “This is the first estimate for the Imbrium impactor’s size that is based largely on the geological features we see on the Moon.”

  15. #1500
    On the road, but not! Danik 2016's Avatar
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    Interesting post. Now we are adding lost giants to dwarf planets.
    "“The Moon still holds clues that can affect our interpretation of the entire solar system,” he said. “Its scarred face can tell us quite a lot about what was happening in our neighbourhood 3.8 billion years ago.”
    "You can always find something better than death."
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