Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Indulge a poet a few questions about Big Bang?

  1. Mar 16, 2014 #1
    I am not a scientist by training. I have a graduate degree in ancient languages. Is this the right place to ask some basic questions about the Big Bang?
     
  2. jcsd
  3. Mar 16, 2014 #2

    micromass

    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor
    2016 Award

    Sure, this is the right place to ask questions. We would appreciate it however if you did some research on your own before asking questions. For example, try to read http://en.wikipedia.org/wiki/Big_Bang and the FAQ's at https://www.physicsforums.com/forumdisplay.php?f=206 [Broken]

    If you still have questions after that reading, then you are more than welcome to ask here!
     
    Last edited by a moderator: May 6, 2017
  4. Mar 16, 2014 #3
    Thanks. I am interested specifically in how "cooling" (I guess that would be energy density decreasing) results in the formation of multiple elements.

    Is it correct to assume that "singularity" means "undifferentiated matter|substance"?

    If energy density is defined as "energy stored in a given system or region of space per unit volume or mass" then for energy density to decrease, either mass would have to increase or space would have to increase. Is that right?

    Is it correct to assume that the mass of the Universe is constant? So that it is space that is increasing?

    Did space increase uniformly? Homogeneous energy density? No clumping of mass? Or if energy density did not remain homogeneous, what accounts for the heterogeneity?
     
  5. Mar 16, 2014 #4

    Drakkith

    User Avatar

    Staff: Mentor

    Per wiki: http://en.wikipedia.org/wiki/Big_Bang_nucleosynthesis#Sequence

    As the universe expands, it cools. Free neutrons and protons are less stable than helium nuclei, and the protons and neutrons have a strong tendency to form helium-4. However, forming helium-4 requires the intermediate step of forming deuterium. Before nucleosynthesis began, the temperature was high enough for many photons to have energy greater than the binding energy of deuterium; therefore any deuterium that is formed was immediately destroyed (a situation known as the deuterium bottleneck). Hence, the formation of helium-4 is delayed until the universe became cool enough for deuterium to survive (at about T = 0.1 MeV); after which there was a sudden burst of element formation. However, very shortly thereafter, at twenty minutes after the Big Bang, the universe became too cool for any further nuclear fusion and nucleosynthesis to occur. At this point, the elemental abundances were nearly fixed, and only change was the result of the radioactive decay of some products of BBN (such as tritium).

    Note that helium-4 wasn't the only element that was created by this fusion process. A small amount of Lithium and trace amounts of heavier elements were created as well.

    Also, the expansion acts on both particles and radiation to reduce their energy. Two particles approaching each other would be very slightly slowed by expansion before they hit. If the expansion process continues for a long enough period of time and over a great number of collisions, then what started as extremely high energy particles smashing into each and annihilating or creating other particles eventually becomes low speed particles colliding and forming nuclear or chemical bonds.

    No, a singularity is the point where calculations in our mathematical models start giving us infinities as answers. At this point, the model can no longer predict anything. The infinite density of the center of a black hole is the classic example. We don't actually know if a "real" singularity exists or if it is our math breaking down, however I've been told that most scientists working in cosmology and astrophysics favor the latter.

    The mass of objects inhabiting a volume of space adds to the energy density. To decrease energy density you can remove some of these objects, decrease the kinetic energy or temperature, or increase the volume of space they objects occupy (which is what expansion does).

    I'm not 100% sure, but I don't think the mass of the universe is constant. Consider the CMB. Over time the expansion of the universe redshifts the CMB photons and reduces their energy. This energy is simply gone, along with the mass the energy would have added to the universe.

    The early universe was never perfectly homogenous. Quantum fluctuations and the inherent random movement of particles and EM radiation caused some areas of the universe to be more or less dense than the average. Denser areas tended to be where galaxies formed, while less dense areas tended to be where intergalactic voids formed.
     
  6. Mar 16, 2014 #5

    marcus

    User Avatar
    Science Advisor
    Gold Member
    Dearly Missed

    If you google "smoot TED" you should get a 15-20 minute video by Nobel laureate George Smoot speaking to a club of intelligent people in (Tech, Entertainment, Design) industries somewhere in the LA area. He talks about structure formation (cooling and clumping) in the early universe.

    Don't worry about "singularity", it's a place where a math function fails to be defined, blows up etc, and the word is carried over to physical theories---a place where the theory breaks down, cannot be made to apply, stops giving meaningful numbers. Old Victorian word "singular" meaning ODD. "A very singular chap" meaning odd peculiar irregular. Singularity is something that happens in manmade theories not in nature.

    1915 Gen. Rel. breaks down right at the start of expansion. Suffers a singularity. there are people working on improved theory which will reproduce the good stuff of GR but will not break down at the start of expansion but will extend on back in time. We just have to be patient and the "singularity" in cosmology will go away, as the math model improves.

    George Smoot has some computer animations of clumping in the early universe at first making a kind of cobwebby mess. And then higher density regions attracting more, and forming clusters of galaxies etc etc

    According to current thinking because of quantum fluctuations you wouldn't expect PERFECTLY uniform even distribution. there would be some slight OVERdensity patches and some slight UNDERdensity regions. and stuff would start to gather, to "fall" towards the over density. they simulate that kind of process numerically in the computer and produce movies of it.

    Interestingly, the models of this structure formation process work better if there is some amount of a kind of extra matter called "dark matter" that sort of helps the ordinary matter with its gravity. the dark matter begins to fall together and its gravity assists the ordinary to coagulate. But because of a special feature of DM it can itself not achieve the final stage of condensation and form stars. It is unable to radiate! So it can't bump and get hot and radiate off the excess energy. It always has this energy of motion that it can't get rid of by shining off some heat glow. So it is unable to ultimately SETTLE DOWN. So it HELPS but only ordinary matter gets to form stars and planets. Very interesting. There are suggestions that folks have begun to observe evidence of a kind of neutrino that has the right properties to be the dark matter particle.

    Anyway you are a poet so you have imagination and maybe can use this, but I run on and say more than thou askest.
     
    Last edited: Mar 16, 2014
  7. Mar 17, 2014 #6
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Indulge a poet a few questions about Big Bang?
Loading...