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Thread: Astronomy

  1. #376
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    This from EarthSky:
    Many universes? Until recent decades, most astronomers would have told you that, by definition, the word universe means all there is. That word was used to describe all space, time, matter, physical laws and constants. But now a new word – multiverse – has entered the language of scientists.

    Not all scientists agree, but some – including Stephen Hawking, for example, and Alan Guth of MIT – believe there’s scientific justification for a multiverse, many universes springing into being, possibly existing simultaneously, each possibly with its own physics. If true, then our universe of stars and galaxies is just a small part of this vast assemblage of many universes.


    There is a growing interest in parallel universes, rather than just one universe, and not just one big bang, but several. This is discussed in http://earthsky.org/space/bumping-up...llel-universe?

  2. #377
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    In Charles Lawrence's talk on the Planck mission results he claimed there wasn't any evidence in the data for multiverses. He also didn't even know what to measure in the data that would show a multiverse. See the part toward the end about 1:30 and following for this discussion: https://www.youtube.com/watch?v=ZCZdrfDHwgU

    That makes me think there isn't any "scientific justification" for a multiverse. However, if one needs certain metaphysical assumptions about the universe to be true then there might be philosophical justifications that could save those assumptions by invoking a random multiverse. All we would have to go on are whether the justifications are rational or not. There is no data, hence no scientific justification.

    The main problem is that the cosmic microwave background is evidence that our universe had a beginning. It is not eternal. Did something conscious start the universe? If so, then one has theism. So the basic metaphysical assumption underlying these multiverse theories is the need to avoid theism. This is done by assuming there must be a random multiverse. This would restore the eternal and unconscious nature of the universe. However, it does not help explain the existence of our own consciousness.

    My personal view is that there is a non-random, intentional multiverse. If the big bang happened once, it happened many times. There is a consciousness that started all of these universes and they are all able to support life.
    Last edited by YesNo; 12-01-2015 at 12:23 PM.

  3. #378
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    Another question that arose is where in the universe did the big bang take place and so provide the centre of the universe out of which it expanded? Presumably the heart of the universe can be identified, by measuring the distance from this "centre". Where, for example is our own galaxy the Milky Way in this pattern of explosion?

  4. #379
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    I am thinking there should be a center as well, but I understand that space and time started with the big bang. If that is the case, the big bang happened everywhere in our space and time. However, it is hard for me to think of space and time having a beginning.

    One thing Lawrence mentioned in his talk was that someone looking at the cosmic microwave background from a different part of the universe would see something different.

    I was thinking about the multiverse a bit more. It seems that life requires that the universe be finite based on Olber's paradox: https://en.wikipedia.org/wiki/Olbers%27_paradox If there were infinitely many stars, the night sky would be black and too hot for life to survive. So each universe is finite and this allows us to exist.

  5. #380
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    "Scientists capture a black hole swallowing a star for the first time ever" - http://releases.jhu.edu/2015/11/26/s...speed-flare-2/

    Ta ! (short for tarradiddle),
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  6. #381
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    I searched for ASASSN-14li which I assume is the name associated with this along with "tidal disruption event". I wonder what Mersini-Houghton thinks of that event.

  7. #382
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    The multiverse theory: https://en.wikipedia.org/wiki/Laura_Mersini-Houghton. Sorry, not checked my mail for some days...

  8. #383
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    She may be wrong about the cosmic microwave background showing evidence for a multiverse. I understand the Planck data does not show enough variability that something besides randomness cannot account for it. Also I don't understand why another universe would have a gravitational effect on our universe. They are in separate spaces. They shouldn't touch.

    It seems she is also interested in many worlds. This is different from a multiverse. Each universe would have multiple versions of itself to account for quantum indeterminacy. I don't think that's a coherent interpretation of quantum physics.

    So maybe she is wrong about the black holes as well. According to the link, "She claimed that Hawking radiation causes the star to shed mass at a rate such that it no longer has the density sufficient to create a black hole." In her favor there isn't much evidence to go on. The ASASSN-14li might be explainable in other ways than a black hole consuming a star. It is after all in another galaxy and the predicted collision in our galaxy's center did not happen.

  9. #384
    Orwellian The Atheist's Avatar
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    An astronomy thread?

    Why didn't someone tell me?

    Serious amateur astronomer for about 40 years. I'll be checking back to see what's been going on.
    Go to work, get married, have some kids, pay your taxes, pay your bills, watch your tv, follow fashion, act normal, obey the law and repeat after me: "I am free."

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  10. #385
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    Welcome to the astronomy thread!

  11. #386
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    Yes, welcome back. There's also a cosmology thread you might be interested in.

    I was hoping to see the moon and Venus this morning, but the sky was overcast.

  12. #387
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    The Atheist - you are probably far ahead of us - or at least of me. I was inspired to start this thread because of the recent discoveries in our own solar system, New Horizons, the explorations of Mars (which shows just how unnecessary it will be to send astronauts to Mars). And this is just the beginning. The future is clearly with unmanned exploration, I think.

    It would be interested to learn more about what kind of amateur astronomy you have been involved in. I have no equipment to speak of, only a 7x50 binoculars - asaklitt, decent quality but better for birdwatching than stargazing...There is not even a local astro club near me...So I follow space.com and EarthSky.org on a regular basis, and am a member of the British popular astronomy society. Read the Swedish equivelent, too, at local libraries - populär astronomi.

  13. #388
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    SPA: Electronic News Bulletin No. 411 2015 December 6

    A team of astronomers using the Very Large Telescope (VLT) has captured detailed images of the hypergiant star VY Canis Majoris. The observations show how the unexpectedly large size of the particles of dust surrounding the star enable it to lose an enormous amount of mass as it begins to die. That process, understood now for the first time, is necessary to prepare such gigantic stars to meet their explosive demise as supernovae. VY CMa is a stellar goliath, a red hypergiant, one of the largest stars known in the Milky Way. It is 30 or 40 times the mass of the Sun and 300,000 times (nearly 14 magnitudes) more luminous. In its current state, the star would encompass the orbit of Jupiter, having expanded tremendously as it entered the final stages of its existence. The new observations of the star were made with the SPHERE instrument on the VLT. The adaptive-optics system of that instrument corrects images to a higher degree than earlier systems. It allows features very close to bright sources of light to be seen in great detail. SPHERE clearly revealed how the brilliant light of VY CMa was lighting up clouds of material surrounding it. The team could not only see into the heart of the cloud of gas and dust around the star, but could also see how the starlight was scattered and polarised by the surrounding material. Those measurements were key to discovering the properties of the dust, and revealed the grains of dust to be comparatively large particles, half a micron across, which may seem small, but it is about 50 times larger than the dust normally found in interstellar space.

  14. #389
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    Cheers!

    A couple of bits that may already be under discussion:

    The Japan probe to Venus is finally in orbit - 5 years late.

    and the LISA Pathfinder, about to prove gravitational theories.

    My telescope is one of these.

    Fully motorised, with many thousands of pre-programmed positions that work off a GPS. It means you don't have to waste too much time looking for what you want to see. Excellent for planets & nebulae.

    The astronomy comes in handy at times, like when we saw a bolide a few months ago. In 40 years of watching the sky I've never seen anything remotely as impressive as that. The thing that struck me - and probably as a result of being in a very quiet place - was the sound! It was an amazing hissing that made us look at the sky, only to see it bursting through the atmosphere. No question it was an outer solar system rock; it was much, much faster than any meteor I've seen.

    Out of this world, you might say!
    Go to work, get married, have some kids, pay your taxes, pay your bills, watch your tv, follow fashion, act normal, obey the law and repeat after me: "I am free."

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  15. #390
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    A fellow-Londoner, and with a decent telescope! The link to The Guardian article was interesting. And the Japanese Venus probe. It seems that different countries are specialising in different planets to investigate further, like NASA on Mars. Good to specialise, especially when each planet poses its own problems. There is an article on this in Scace.com today: http://www.space.com/31300-japan-aka...orbit-try.html

    Venus has been very prominent in the skies in recent months, bright and clear. Feel free to publish any pictures on this website.
    Last edited by Dreamwoven; 12-08-2015 at 02:43 AM.

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