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Accelerating Universe,rate Of Acc Data Needed

  1. May 5, 2008 #1
    I am looking for some data for the deceleration/acceleration of the universe over time/distance. I would love to have matching data with the expected deceleration force due to gravity and any other factors presently known to exist, ideally with margin of error.
    I am ready to compare it with my predicted calculations.......
  2. jcsd
  3. May 6, 2008 #2


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    We don't directly measure acceleration or deceleration but have to infer it based on a model, derived from General Relativity, and observations of objects in the Universe. The most 'direct' method we currently have of tracking the expansion history is by observing the magnitude vs redshift of a particular class of Supernovae. By calculating the what the GR model predicts we would observe, we can compare the predictions with observations and work out the parameters of the model. When we do this the result is that the expansion of the Universe must be accelerating.

    If you have a different model (I think that's what you are saying?) what you need to do is work out what the predictions of the model are for things that we can observe, such as the Supernovae data, and compare it to the observations. You can't however take the acceleration or deceleration implied by fitting the GR model to the observations and test your model against that. Everything always comes back to what we can actually observe.

    If you want to see in more detail how this is done have a look at http://arxiv.org/abs/astro-ph/0510155" [Broken] paper. There are plenty of others out there as well, that is just one example.
    Last edited by a moderator: May 3, 2017
  4. May 6, 2008 #3
    Wallace, thanks for the link. I did know about the supernova redshift measurements, but not to the details given in the paper.
    I am an engineer, not an astrophysist, so I am not familar with all the terminology contained within some of the references I find. In my model the repulsive dark energy force (I dislike this term) is much smaller in a young universe than the attractive gravitational force. With increasing time/distance, the dark repulsive force decreases at a slower rate than the attractive gravitational force. There is a crossing point where the repulsive force is equal to the gravitational attraction after which the accelerating force is greater than the garvitation attraction. Neither force is linear, nor is the resultant net force. As the universe becomes larger the accelerating force will decrease, but never to the point of zero acceleration.

    What I have is correlation between gravitational attraction and this dark energy repulsive force relative to distance. A graph of this would look like two decreasing intersecting curves with force on the y axis and distance on the x axis. The net resultant force would be negative(ie attractive) at time sightly > zero, grow to a posive repulsive force and then decrease to a ever decreasing but always positive repulsive force as the universe becomes bigger.
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