Comments policy and other housekeeping issues

I have chosen as my comment policy that the first comment by someone has to be approved by me but once approved that person will be able to post comments freely.

I will try to check frequently and apologize in advance if work and other pressures result in delays and your first comment not appearing as soon as you might like.

The blogging software here is different from what I am used to so there may be some rough patches early on until I get the feel of things. If readers notice anything that can be improved upon, I would be grateful for their suggestions.


  1. Pierce R. Butler says

    … I would be grateful for their suggestions.

    Doin’ fine so far.

    How ’bout a lay-comprehensible explanation of how the dark matter/energy hypotheses affect the Big Bang model (Genesis references optional)?

  2. Tim says

    Congratulations on your new site, Mano! I’m glad that your writings are getting a broader platform.

  3. felicis says

    Personally, I have wondered how the Hubble red shift correlates with distance and why the assumption is that the universe has finite age rather than hyperbolic geometry.

    I blame poor communication -- the explanation (that I recall from PBS in the 70’s) is that the universe is ‘expanding as a balloon’ and the red shift has to do with velocity. But -- wouldn’t either (or both) changing curvature or a hyperbolic geometry lead to a red shift as well?

    Presumably the numbers don’t work out correctly -- but how could I check myself if (in principle) I wanted to?

  4. Mano Singham says

    It is not clear to me why hyperbolic geometry of space-time would lead to a red shift at all. Could you give more details?

  5. Pinky says

    Mano Singham -- thank you for the tough, honorable work you do as a science educator.

    Science education is where enlightenment starts!

  6. Eric says

    Well -- I am not entirely sure if the ‘gravitational red shift’ occurs because of the curvature of space-time or because of the change in the curvature of space-time, so I was thinking that (if the former) an infinite hyperbolic space could see the same kind of red-shift effect, *and* would be an answer to Olber’s Paradox (the background radiation being the result of the asymptotic red-shift of an infinite amount of radiation).

    Of course -- just after this question, I saw your next post and went and looked at the 16-parts you had, and the Big Bang FAQ, and my ‘theory’ cannot in any way explain the relative abundances of light elements (at least I don’t see any obvious way to reconcile it…)

    I have a strong mathematics background, and this idea kind of popped up when I was thinking one day about Olber’s paradox and the comment of a geometry teacher popped up, “a hyperbolic space is very cold -- the heat from a fire drops exponentially”… So, I wondered if a balance between the density of stars over all space and that exponential decrease could explain both Olber and the background radiation. Then I thought about the red shift and was wondering if that could also be explained with geometry…

    I guess what I *really* would like to know is how the gravitational red shift works mathematically (i.e. given a curvature tensor, how do we get a red-shift out of it? If that’s the right way to ask the question…)


  7. 'Tis Himself, OM. says

    Welcome to FtB.

    I’m FtB’s token economist. That means I can answer any economics question you have, as long as you’ll accept “I don’t know” as an answer.

  8. Mano Singham says

    There is a simpler way of looking at this. The red shift of light comes from two sources. One is the loss in energy of the photon as it climbs out of the gravitational field into space on its way to us. This is what we refer to as the gravitational red shift.

    The other is the stretching of the wavelength during the photon’s journey to us through empty space, due to the expansion of space.

    The gravitational field, in addition to red shifting the light, also curves space. So there is a relationship between the red shift and the curvature but I suspect it is not a simple one. I for one do not know it but a mathematical cosmologist may be able to say what it is.

  9. Dorset Troll says

    A sensible comments policy for a happier blog (I’m not really a troll, but I have lived in Dorset).

  10. Ex-Android says

    I’m glad to see you may have a larger audience. I spent 25 years reading trash written by fools, liars and those of little education. I’ve been free now for 20 years. My freedom came about as a result of giving attention to helpful educators as yourself. Thank you.

  11. Snap says

    Whereas I can answer “I don’t know” on a much wider range of topics than simply economics. I am, therefore, clearly a token expert of a much higher caliber ;^)

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