Twinkle Twinkle Little Star: BGP's Astronomy Thread

Page 40 of I'm sure there are several astronomy enthusiasts here, besides TB&G and myself. I can't get enough of astronomy and I never get tired of learning n... 589 comments | 14184 Views | Go to page 1 →

  1. #586
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    Found in the Constellation Monoceros, this is the star, V838Mon, along with the dust and gas that surrounds it. It's about 20,000LY from us and about 13.7LY across. Up until early on in this century, it seemed like just another ordinary star. But 15 years ago this month, the star flashed and became 4,000 times brighter. In fact, it was the brightest star in our Milky Way galaxy for several weeks after the flash. Then just as suddenly, it faded. A stellar flash like this had never been seen before. While the V838Mon flash appears to expel material into space, what appears here is an outwardly moving light echo of bright flash. The star continues to be the subject of intensive study.

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    In with a Bang, out with a ...

    About 13.8 billion years ago, our entire visible universe was contained in an unimaginably hot, dense point about a billionth the size of a nuclear particle. Since then, it has expanded... A LOT !!!

    In this post, I want to talk just briefly about different periods in the life of the universe, but mostly I want to speculate , not so much about what happened at the beginning, but how it's all gonna end.

    First, let me take you back(WAYYY back) to the infant universe.

    Inflation:

    In FAR less than a nanosecond(a billionth of a sec.), a repulsive energy field inflated space to a visible size and filled it with a soup of subatomic particles called quarks. A quark is a type of elementary particle and a fundamental constituent of matter. Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nuclei.

    Age of Universe at this time: 10^ -32 milliseconds
    Size of the universe: Infinitesimal to about the size of a golf ball

    Those Quarky Quarks:

    The baby universe expanded, cooled. Quarks clumped into protons and neutrons, the building blocks of atomic nuclei.

    Age of universe at this time= 1/100 of a millisecond( or 1/100,000 of a second)
    Size = About a trillionth its present size

    H and He Come on the Scene:

    As the universe continued to cool, the lightest nuclei, that of hydrogen and helium, are born. A thick fog of particles blocked out all light.

    Age of the universe = 1/100 of a second to 3+ minutes
    Size = About 1-billionth its present size

    "Let there be light":

    Electrons began orbiting nuclei, thus creating atoms. The glow from our infant universe was unveiled. We had light!!! This early light is as far back as our modern instrumentation can see.

    Age of the universe = about 380,000 yrs.
    Size = 9/10,000 of its present size

    "The Dark Ages" :

    For some 300 million yrs the cosmic background radiation was the only light. Clumps of matter that would eventually become galaxies glowed brightest.

    Age of universe= 300 million yrs.
    Size = About 1/10 its present size

    Gravity wins and the stars turn on :



    Dense clouds of dust and gas collapsed under their own gravity, as well as that of dark matter , and eventually formed the stars and galaxies. Nuclear fusion lit the stars!!!

    Age of universe: 300 million yrs.
    Size: About 1/10 its present size.

    Anti-Gravity Finally Wins the Tug-of-War:

    After being slowed for billions of years by gravity, the expansion of the universe once again accelerated. The big, powerful culprit--- Dark Energy!!! To this day, we still are not clear as to its nature, but we know that dark energy , along with dark matter make up more than 95% of the universe. That's right, the vast majority of the universe cannot even been seen!!!

    Age of the universe at this time= 10 billion yrs.
    Size= About 77/100 its present size.

    Fast Forward to... the Present !:

    Today, the universe continues to expand, becoming less and less dense. As a result, fewer new stars and galaxies are forming.

    Age of universe= 13.8 billion yrs.
    Size= Present

    While we have learned much in recent decades about the early universe, still many questions remain. As you can see, the lifetime of the universe has featured a no holds barred battle royal between gravity and anti-gravity. Which force will win out in the end?

    There are three possible scenarios for what is likely the eventual fate of the universe. The theory you subscribe to probably depends upon which you think is the stronger force- gravity or anti-gravity.

    1) Is the density of matter enough for gravity to halt or even reverse the present cosmic expansion, leading to a "Big Crunch." In other words, will gravity eventually cause the universe to collapse back onto itself? That will be one heck of a crunch! I wouldn't want to be around for that. I personally don't think this scenario is likely, given the immense power of dark energy, a kind of anti-gravity, that makes up almost 70% of the universe(dark matter makes up most of the remainder).

    2) If you are in the dark energy/anti-gravity camp, you likely think that the acceleration in the universe's expansion caused by dark energy will trigger a "Big Rip" that will shred everything from galaxies to atoms. In this scenario, the expansion will accelerate to the point that everything in the universe will be ripped to shreds.

    3) Those like myself who don't believe we will be crunched or ripped believe that the universe is likely to continue to expand for hundreds of billions of years, long after ALL the stars have shut down and gone "night night." Yes, I think the universe is likely to outlive even the last flicker of starlight. The universe, in my opinion is destined to work a perpetual and infinite graveyard shift among a cold, dark, void of nothingness. I say, in with a bang.... out with a whimper !!!

    I would be interested to hear what you think. Do you think the end is most likely gonna be a Big Crunch , a Big Rip, or Infinite expansion? I actually sit and ponder things like this a lot. The end of times is somehow even more fascinating to me, at times, than the beginning.
    I wish I knew our ultimate fate... or do I???

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    SF, I’ve always had a problem wrapping my brain around the theory that the universe was originally the size of a golf ball. Could you explain that more in layman’s terms for me.

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    Quote Originally Posted by The Professor View Post
    SF, I’ve always had a problem wrapping my brain around the theory that the universe was originally the size of a golf ball. Could you explain that more in layman’s terms for me.
    That's a good question and a very hard one to answer. I'm still thinking about it. I asked a physicist and he seemed at a loss to add much. I've sent out a message to astrophysicist, Michio Kaku, but I'm not very hopeful of getting a response anytime soon.

    Most astrophysicists accept that the universe was born as an incredibly hot, dense point in space. Unlike what the name might suggest, there was probably no explosion in space but just the appearance of space everywhere in the baby universe. When the universe was VERY young- something like a hundredth of a billionth of a trillionth of a trillionth of a second- it underwent an incredible spurt of growth, doubling in size something like 90 times or more. During this expansion, it was cooling and getting less dense(though it was still unimaginably dense at this point). Note, at this time there was still no matter. It had yet to form. After this period of inflation , our universe continued to grow, but at a slower rate. As space continued to expand, the universe cooled and matter formed. The rest, as we say, is history.

    What started as a single infinitesimally small point could fit in the palm of your hand just a hundredth of a billionth of a trillionth of a trillionth of a second later. Much less than a second later, it's the size of the Earth. That's quite the growth spurt. It's hard to fathom, I know. It's one of those things that hard for the human mind to comprehend.
    Space appeared from a hot, dense point , expanded incredibly fast, expansion continued but at a "slower" rate, continued expansion, universe cools, matter forms... and so on...

    Wish I had a better answer. We'll have to wait on Michio .

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    It's hard to fathom how dense the baby universe was. Consider, for a minute, how dense neutron stars are. One sugar cubed size of neutron star material would weigh more than all humanity--- and there are a lot of fat humans!!!

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