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  1. E

    Proton / neutron freeze out

    I thought the neutron's decay time is more like 15 minutes. http://en.wikipedia.org/wiki/Neutron#Stability_and_beta_decay Maybe your hinting that the decay time is slower at such high temps as there was during BBN...? At the end of BBN, without neutron decay, I think it is calculated...
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    CMB a picture of the past

    Ok, so it is actually a picture of the past with the only difference being the wavelength. Great, now I know... Thanks for the help!!
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    CMB a picture of the past

    Thanks for your reply Jorrie! Can anyone confirm this? I thought that the universe was smoother in the past, wouldn't these changes in the density affect the way the CMB looks? Thanks again!!
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    CMB a picture of the past

    Hi, Am I right when I say that the cosmic microwave background is a picture of the radiation left from recombination but that the picture (from COBE or WMAP) that we see today is not exactly the same as it was then due to the redshifting of the radiation particles. The flucuations that we see...
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    Big bang predictions

    Ok, I didn't know about the seperate Friedmann acceleration equation. Thanks for the help!
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    Big bang predictions

    Hi, I am trying to understand how it is possible to make predictions about the energy density of early universe using the freidman equation if the expansion rate of the universe has not been constant throughout history. As I understand it there are three main variables in the freidman...
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    Proton / neutron freeze out

    As I understand it, it can be calculated that 1 minute after the big bang, when protons and neutrons freeze out and are no longer being created, that for every neutron that exists there are 7 protons. Does anyone know what equation is used to calculate this and if it is not a equation that is...
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    Expanding Universe

    Ok, that makes sense. Good analogy by the way, makes it much eaiser to picture the expansion in my mind. Thanks a lot!!
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    Expanding Universe

    Hello, I am trying to understand that in order for the universe to be expanding that galaxies at further distances must be moving away from us at faster speeds than galaxies closer to us. It seems enough that all galaxies are moving away from us (or each other if observed from another galaxy)...
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    More Density = More Gravity?

    Perfect!! That helped a lot!! Thanks!!
  11. E

    More Density = More Gravity?

    Ok great, that clears things up then. One more thing, is there a equation that describes the relationship between an objects "surface gravity" and it's mass? Thanks again for the help!!
  12. E

    More Density = More Gravity?

    Hi, I am a bit confused with how a neutron star or black hole has such a high force of gravity. As I understand the process of star death of a massive star (I'll use a neutron star for example), 1) the star fuses heavier and heavier elements 2) the core begins to contract 3) this...
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    Particle confusion

    Thanks for the help, after your comments and some quality time on Wikipedia I think I got everything worked out now.... I think that it made it difficult for me that, when I first heard about fermions and bosons they were presented as 'matter particles' and 'force particles' and I was...
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    Particle confusion

    And one more thing... If this is the 'standard definition'... Does this mean that not all fermions are 'matter particles' and not all bosons are 'force particles' and that bosons can make up matter and fermions can make up forces...?
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    Particle confusion

    The first part of the explanation was spot on, thanks but... Can you explain what you mean by this... Which classification are you refering to? And fundamental and composite, haven't heard of those.... are they diffrent types of bosons?
  16. E

    Particle confusion

    So I have just started learning a bit about particle physics and I am confused about some small details... As I understood it fermions and bosons are two different types of particles that have different behaviours. They are not related other than the fact that they are both particles. But...
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    Nm into Joules

    You are right Doc Al I wasn't asking about conservative force but I believe the answer to the question posed by ZapperZ is 0 Joules since the distance between the starting point and the ending point is 0, then 0 * 100Nm = 0 Joules, or...?
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    Nm into Joules

    So, am I right in saying that if I have 100N in 1 meter and I turn my meter long handle 0.2rad that I do 100N * 0.2rad = 20Joules of work?
  19. E

    Nm into Joules

    Got it. Thanks
  20. E

    Nm into Joules

    Maybe this is a stupid question but... If I have a torque value of, let's say, 100 Nm, am I right in saying that it takes 100 Joules of energy to generate that torque since 1 Nm = 1 Joule.
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    Force of Falling Bodies

    Sorry... maybe I shouldn't post sub-topics on other peoples topics. I know Newton is easier in this case, I am just trying to see if I understand Einstein well enough to answer the question in another way and to get an answer about part of the theory I don't understand.
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    Deadhang Equation

    Yes, I understand that torque is force x distance and that the answer comes in the form of Nm and if I were going to use the torque equation in my situation then I also must be able to take the answer from the equation (X Nm) and put it into another equation that considers the area and time...
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    Force of Falling Bodies

    I am going to try and answer this question a la Einstein to see if I have understood the theory correctly and pose another related question. As the object falls it enters slower time 'zones' as the force of gravity increases closer to the earths surface and as the time slows the object sheds...
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    Deadhang Equation

    You are right about the friction part... We use powdered chalk to improve the 'grip' that we get when climbing or in this instance dead hanging but temperature does still play a role but it is a factor that is too complex for me to calculate accurately but I’d be more than welcome to hear...
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    Deadhang Equation

    Hi, I am working on a small project and am hoping to get some outside insight from anyone who has the time or intrest... One of my hobbies is rock climbing and because I am quite fanatic about it I train for it quite regularly. One of the methods commonly used for training is called 'dead...
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    Torque force homework help

    Yes! That worked. Thanks
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    Torque force homework help

    Yeah, your probably right about the translation... the problem is translated from swedish and my physics termonology in english isn't so accurate. Yes, the chain is divided in two as you said and yes, you solve the problem dividing the total force by 2. F * L = 4910N * (L/2) * sin(30) I...
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    Torque force homework help

    Homework Statement A drawbridge to the castle is slowly lifted. Its weight is 500kg. There are is one chain drawn over a pulley that pulls up the drawbridge (see pic). The angle is 30 degrees at the rotation point (see pic). http://pici.se/200459/ link to pic if it dosen't come up...
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