Scale factor Definition and 62 Threads

A scale factor is usually a decimal which scales, or multiplies, some quantity. In the equation y = Cx, C is the scale factor for x. C is also the coefficient of x, and may be called the constant of proportionality of y to x. For example, doubling distances corresponds to a scale factor of two for distance, while cutting a cake in half results in pieces with a scale factor for volume of one half. The basic equation for it is image over preimage.
In the field of measurements, the scale factor of an instrument is sometimes referred to as sensitivity. The ratio of any two corresponding lengths in two similar geometric figures is also called a scale.

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  1. M

    Normalization, reweighting, and the scale factor:

    Hi all, I am about to begin my studies as an experimentalist and I keep hearing about these terms when someone represents his data as histograms. Can some one here, please, give me a clear explanation about their meanings. My background is theory and you can use as much mathematics as you...
  2. F

    What is meant by scale factor for gyroscopes.

    hello.i'm looking at data for gyroscopes, because i need to find one that's very accurate to within a degree. there are two items that might describe it the way i see it: bias or scale factor... I'm not sure which one would tell me what I need to know. I've tried to Google for definitions, but...
  3. I

    What is the current value of the scale factor?

    Do cosmologists know what is the current value of the scale factor? I know we have a current value for the Hubble constant H, and I know H=a'/a. But what about the value of a? Thanks!
  4. R

    Does the Planck length grow with the scale factor?

    What happens to the Planck length due to the expansion? Does it grow with the scale factor?
  5. W

    Determining Hubble Constant and Scale Factor of Universe

    Hi, I am in my second astronomy course and just received a twenty question take home final exam, and I am having trouble with two of the questions. In 2004 astronomers reported finding evidence that certain white dwarfs are 12.1 +- 0.9 billion years old. Assuming an inflationary model in...
  6. K

    Meaning of setting the scale factor equal to 1 at present epoch

    EDIT: I corrected a typo below: I had forgotten to put my entire expression for a(t) to the power 1/3. It's corrected now This may sound like a silly question but it's bugging me quite a bit. Consider a cosmological model, let's say the simple case of no pressure, no cosmological...
  7. K

    How many parameters are needed to fix the scale factor?

    Never mind! I realized the answer to my question. Consider solving Einstein's equations in a FLRW universe and assume that there is no other force acting on matter/energy beside gravity. Let's say I want to find the full time evolution of the scale factor a(t) (and knowing...
  8. K

    How Does Scale Factor Affect Objects in Expanding Universe?

    I will be writing my final exam tomorrow evening, and I am currently terribly stuck on the following practice problems. I have posted my thoughts below each problem. They look tricky to me. It would be very nice if someone could help me out and I will remain eternally grateful for your help...
  9. D

    General Relativity, form of scale factor

    We are given a form of Einstein's field equations: 3R'' = -pR R''R + 2((R')^2) = p(R^2) where p is a constant and R' = dR/dt Assuimg that R and R' are both positive, we are asked to show that the general solution is R(t) = A*[(t-ti)^(2/3)] I'm very confused about this. If we...
  10. George Jones

    Scale Factor Ratio: Z Value at End of Inflationary Era

    What is the ratio of the scale factor now to the scale factor at the end of the inflationary era? Edit: In other words, what is the z value of the end of the inflationary era?
  11. K

    Age of Universe, Redshift & Scale Factor

    Homework Statement Assume that the current age of the universe is 13.4 billion years old, and that we live in a matter-dominated, omega_m = 1, critical universe, what is the age of the universe at redshift 0.6? HINT: use the current age of the universe to pin down the proportionality...
  12. M

    Scale factor in Robertson-Walker metric

    The scale factor in the R-W metric is there to account for the expansion of the universe. My question is whether this scale factor is put in by hand just to account for observations? Or can it be derived from more basic assumptions? Thanks.
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