Big Bang spørgsmål

Fora ASTRO-FORUM GENEREL ASTRONOMI Big Bang spørgsmål

  • This topic has 149 svar, 19 stemmer, and was last updated 11 years, 8 months siden by hjertensfryd. This post has been viewed 4272 times
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  • #2388

    mhansen
    Deltager
    • Nova

    Så vidt jeg har kunne forstå af Universe (Freedman, 2008), så skulle universet ikke have hverken have egenskaberne af en hyperbol eller en sfære. Faktisk så skulle universet være et flat accelererende univers.

    Man skal huske på at det univers som vi kender har en optisk grænse. Det er den afstand hvormed lyset fra fjerne objekter ikke har nået os endnu.

    Men det er alligevel en underlig tanke for vores hjerner at forestille os, at man ved at rejse i en bestemt retning i universet, skulle havne det samme sted som man startede. Og jeg vil da også mene at tankegangen bag det flade univers, siger lidt det modsatte. Men så velbevandret er jeg dog ikke i kosmologi.
    #2389

    jesper
    Deltager
    • Neutron star

    Som jeg har forstået det er det flade univers en naturlig følge af inflationen, hvadenten universet i virkeligheden er lukket eller åbent. Hele universet er simpelthen så stort at geometrien er flad i den lille del af universet der er det observerbare univers. Man kan jo heller ikke ret nemt måle jordens krumning på en kvadratcentimeteri sin have.

    Jeg vil dog ikke lægge hovedet på blokken for om det er den korrekte måde at forstå det.

    Jesper
    #2390

    rigo
    Deltager
    • Super Nova

    mener ikke man kan sige at noget kan være så langt væk, at “lyset” ikke er nået til os endnu. Også fordi, hvis Big bang er sket et sted, så har den fjerneste galakse også kunne nå at “lyse” hen til hvor vi er…

    The current observable universe is about 156 billion light years wide which means that if we start our journey from one corner of the universe at the speed of light, which is 299,000 Km/s or 186,000 miles/s, then it will take about 156 billion years to reach the other corner of the universe. That is just the observable universe. No body knows the actual size

    how%20big%20is%20the%20universe

    No one knows if the universe is infinitely large, or even if ours is the only universe there is.

    Although our view of the universe is limited, our imaginations are not. Astronomers have indirect evidence that the universe of galaxies extends far beyond the region we can see. But no one knows if the whole universe is infinitely large – large beyond limit.

    According to the leading theories, other parts of the universe may look very different from our own – and may even have different laws of nature. We may never be able to find out for sure. But it is possible that clues to the answer lie in plain view, just waiting to be discovered!

    The Future. NASA’s LISA mission will look for ripples in the fabric of space, predicted by Albert Einstein. Such clues may help refine theories about what the rest of the universe is like.

    http://www.rigorigo.dk2008-10-17 18:32:47

    #2391

    jesper
    Deltager
    • Neutron star

    Selvfølgelig kan man da det Rigo. Lysets hastighed er jo ikke uendelig høj. Den er “kun” på 300.000 kilometer i sekundet. Sammenhold det med at universet heller ikke er uendelig gammelt, så er det logisk at der er en grænse for hvor langt vi kan se. Det er det man kalder det observerbare univers. Næste år er Det observerbare univers lidt større, og næste år igen lidt større.

    Den udgave af big bang teorien som indeholder inflatorisk udvidelse i det første korte øjeblik er efterhånden vældig godt underbygget af observationer. Den fortæller os at hele universet er meget, meget større end det lille område som er det observerbare univers.

    Størrelsen af det observerbare univers er da forkert angivet i dit citat??

    Jesper

    Jesper2008-10-17 18:36:01

    #2392

    rigo
    Deltager
    • Super Nova

    Det er nu kun et par mdr. siden hvor Nasa, fandt (tog foto) “starten eller slutning” af the big bang begyndelse, altså kikkede på noget som muligevis er fra “kanten” som man udtrykker det, altså ca15 milliarder lysår tilbage i tiden.

    Jeg syndes meget af det man snakke om, modsiger sige selv (lidt træls man ikke kan finde den udsendelse som var ret god og op todate)

    http://www.rigorigo.dk2008-10-17 18:39:29

    #2393

    rigo
    Deltager
    • Super Nova
    #2394

    rigo
    Deltager
    • Super Nova

    Der er nu mange sider der skriver dette: About a 78 billion light-years radius (156 light-years in diameter) and still expanding.

    http://www.rigorigo.dk2008-10-17 18:47:00

    #2395

    jesper
    Deltager
    • Neutron star

    Fra kanten er bare et lidt smart udtryk. Jeg tror forvirringen skyldes at du skal huske på noget som også blev nævnt længere oppe i tråden: Når man kigger på noget der er langt væk, kigger man samtidig tilbage i tiden. Hvis universet er 15 milliarder år gammelt og vi ser på noget der er 12 milliarder lysår borte, så er lyset fra det vi ser på udsendt da universet var 3 milliarder år gammelt.

    Som illustrationen viser er det længste/ældste vi har set mikrobølge bagrindsstrålingen 300.000 år efter big bang.

    Jesper

    #2397

    mhansen
    Deltager
    • Nova

    Jeg håber da ikke seriøst at de mener at universet kun skulle have en diameter på 156 lysår. Mon ikke de mener en diameter på 156 mia. lysår.

    Det er svært at spekulere på hvor stort universet er. Man kan regne sig frem til, hvor gammelt universet er, ud fra dets udvidelse. Men jeg har ikke kunne finde noget i min litteratur hvor der står noget om universets størrelse. Men jeg kigger lige nærmere.
    #2398

    jesper
    Deltager
    • Neutron star

    156 milliarder lysår for det observerbare univers er jo også forkert. Hvis vi vedtager at universet er 15 milliarder år gammelt, så er 15 milliarder lysår radius af det observerbare univers. Altså en diameter på 30 milliarder lysår. Hele universets størrelse er der ingen der kender (eller kun en, hvis man er troende).

    Jesper
    #2400

    rigo
    Deltager
    • Super Nova

    Men i kan godt se at man siger det er uendelige!, og så på den anden hånd siger det er så og så gammel og så bred = noget modsigende noget.

    Det samme er at de så viser en total timelap fra big bang til enden på det hele, hvor det hele går i et sort hul. = ingen modsigende, da man siger det hele flytter fra sige hinanden
    #2401

    rigo
    Deltager
    • Super Nova

    Jesper wrote: 156 milliarder lysår for det observerbare univers er jo også forkert. Hvis vi vedtager at universet er 15 milliarder år gammelt, så er 15 milliarder lysår radius af det observerbare univers. Altså en diameter på 30 milliarder lysår. Hele universets størrelse er der ingen der kender (eller kun en, hvis man er troende).

    Jesper

    Der mange steder på net hvor de nævner 156 milliarder
    #2402

    rigo
    Deltager
    • Super Nova

    http://www.space.com/scienceastronomy/mystery_monday_040524.html

    Universe Measured: We’re 156 Billion Light-years Wide!

    http://www.rigorigo.dk2008-10-17 19:21:58

    #2403

    rigo
    Deltager
    • Super Nova

    Billion = milliarder ??? vel nej http://www.rigorigo.dk2008-10-17 19:22:33

    #2404

    rigo
    Deltager
    • Super Nova

    If you’ve ever wondered how big the universe is, you’re not alone. Astronomers have long pondered this, too, and they’ve had a hard time figuring it out. Now an estimate has been made, and its a whopper.

    The universe is at least 156 billion light-years wide.

    In the new study, researchers examined primordial radiation imprinted on the cosmos. Among their conclusions is that it is less likely that there is some crazy cosmic “hall of mirrors” that would cause one object to be visible in two locations. And they’ve ruled out the idea that we could peer deep into space and time and see our own planet in its youth.

    First, let’s see why the size is a number you’ve never heard of before.

    Stretching reality

    The universe is about 13.7 billion years old. Light reaching us from the earliest known galaxies has been travelling, therefore, for more than 13 billion years. So one might assume that the radius of the universe is 13.7 billion light-years and that the whole shebang is double that, or 27.4 billion light-years wide.

    But the universe has been expanding ever since the beginning of time, when theorists believe it all sprang forth from an infinitely dense point in a Big Bang.

    “All the distance covered by the light in the early universe gets increased by the expansion of the universe,” explains Neil Cornish, an astrophysicist at Montana State University. “Think of it like compound interest.”

    Need a visual? Imagine the universe just a million years after it was born, Cornish suggests. A batch of light travels for a year, covering one light-year. “At that time, the universe was about 1,000 times smaller than it is today,” he said. “Thus, that one light-year has now stretched to become 1,000 light-years.”

    All the pieces add up to 78 billion-light-years. The light has not traveled that far, but “the starting point of a photon reaching us today after travelling for 13.7 billion years is now 78 billion light-years away,” Cornish said. That would be the radius of the universe, and twice that — 156 billion light-years — is the diameter. That’s based on a view going 90 percent of the way back in time, so it might be slightly larger.

    “It can be thought of as a spherical diameter is the usual sense,” Cornish added comfortingly.

    (You might have heard the universe is almost surely flat, not spherical. The flatness refers to its geometry being “normal,” like what is taught in school; two parallel lines can never cross.)

    Hall of mirrors

    The scientists studied the cosmic microwave background (CMB), radiation unleashed about 380,000 years after the Big Bang, when the universe had first expanded enough to cool and allow atoms to form. Temperature differences in the CMB left an imprint on the sky that was used last year to reveal the age of the universe and confirm other important cosmological measurements.

    The CMB is like a baby picture of the cosmos, before any stars were born.

    The focus of the new work, which was published last week in the journal Physical Review Letters, was a search of CMB data for paired circles that would have indicated the universe is like a hall of mirrors, in which multiple images of the same object could show up in different locations in space-time. A hall of mirrors could mean the universe is finite but tricks us into thinking it is infinite.

    Think of it as a video game in which an object disappearing on the right side of the screen reappears on the left.

    “Several years ago we showed that any finite universe in which light had time to ‘wrap around’ since the Big Bang would have the same pattern of cosmic microwave background temperature fluctuations around pairs of circles,” Cornish explained. They looked for the most likely patterns that would be evident in a CMB map generated by NASA’s Wilkinson Microwave Anisotropy Probe (WMAP).

    They didn’t find those patterns.

    Don’t look back

    “Our results don’t rule out a hall-of-mirrors effect, but they make the possibility far less likely,” Cornish told SPACE.com, adding that the findings have shown “no sign that the universe is finite, but that doesn’t prove that it is infinite.”

    The results do render impossible a “soccer ball” shape for the universe, proposed late last year by another team. “However, if they were to ‘pump up’ their soccer ball to make it larger, they could evade our bounds” and still be in the realm of possibility, Cornish said. Other complex shapes haven’t been ruled out.

    The findings eliminate any chance of seeing our ancient selves, however, unless we can master time travel.

    “If the universe was finite, and had a size of about 4 billion to 5 billion light-years, then light would be able to wrap around the universe, and with a big enough telescope we could view the Earth just after it solidified and when the first life formed,” Cornish said. “Unfortunately, our results rule out this tantalizing possibility.”

    http://www.rigorigo.dk2008-10-17 19:28:19

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