Monday, 1 September 2008

Earth birthday

Another Cosmic Calendar event already!

Only the day after the Solar System begins to form, our own humble planet comes into being.

(Remember, because we are compressing the entire history of the cosmos into one year, each day represents 37.4 million years.*)

I apologize for not having more to say just now - I am still in PhD write-up mode.

References used:
[1] Wikipedia, as usual.
[2] Talk Origins page on dating the age of the Earth

* For those who have followed this series from the beginning, you might remember that I claimed before the each day is 41 million years. I am now calling it 37.4 million. What gives? The earlier figure was based on a 15 billion-year-old universe. I have since learned that the consensus is for a slightly younger universe, at 13.7 billion years. Remember, this is a calendar based on what we know, and so when what we know changes, so does the calendar. If anyone else wants to fact-check my figures and calculations, please let me know.


  1. That picture is not real ! Earth is not visible from space at optical wavelength.

  2. What possible reason could you have for saying something like that? I'm hoping it's some very eccentric joke, rather than a serious claim.

  3. Hi, I am the one who left this comment.
    No it is not a joke!
    If you go to above link, graph there clearly indicates that there is no reflected energy at all within the visible wavelength it means that you can not take any photo!

  4. Okay, I have already spent more time on this than your claim deserves, but I find myself seized by a grim curiosity.

    The page you link to contains what look like lecture notes from a geography class. So the source is probably reliable, but I seriously question your interpretation. There is no graph indicating that there is no visible energy reflected by the Earth. The overall message is that the Earth's surface and atmosphere absorb some of the sun's energy, and reflect the rest. The section on albedo clearly states that various terrestrial features are visible from space.

    So I ask again: what could possibly have persuaded you, in contradiction to all evidence, testimony, reason, and common sense, that the Earth is not visible from space at optical wavelengths?

    This is whole link , I see the graph on the first page,
    x- axis shows the light reflected back from the earth, you can clearly see that visible wavelenght is not reflected back from earth (y axis shows the amplitudes of the reflected light).

  6. You're either kidding (in which case, I fail to see the humour) or you're criminally uninterested in actually thinking about your claims.

    I'm done wasting my time on you.

  7. Ask friend who can interpret graphs for you. You have very ugly language.

  8. I apologize for my ugly language. Perhaps it was unwarranted. Let me explain my position on your claim.

    First, as a scientist, I find the first graph on that page to be poorly-labelled. It seems to indicate the relative distribution of energy across wavelengths of the solar radiation hitting Earth. On reflection, I understand that the markings may seem to indicate that the low-wavelength spike (including visible light) refers only to incoming solar radiation, and the high-wavelength area refers only to outgoing terrestrial radiation.

    This is still ambiguous - I believe the "terrestrial radiation" label refers to radiation that is generated by the Earth (ie, heat from the core), not reflected solar radiation. And, as I said, later portions of the same document seem clearly to claim that visible light does escape into space (for example, the atmospheric transmission graph, which seems to say that almost all visible light gets through).

    My anger and incredulity is because you do not seem to have considered the implications of your claim, and you seem to be ignoring the wealth of evidence that contradicts your claim. Take for example all astronauts who report seeing the earth from space, and all visible-light photos from NASA and other space organizations (such as the one in the original post). Are you claiming that all of these people, who have dedicated their lives to understanding the universe, are either stupid or lying?

    If you can demonstrate that you have thought about the implications of your claim, and that you have some further evidence to support your wild interpretation of a poorly-labelled graph in some geography lecture notes, then I will be happy to carry on this exchange in a respectful manner. If all you have is wild claims, no good evidence, contempt for the work of scientists and engineers, and a complete unwillingness to consider that you might be wrong, then I think my abrupt dismissal was warranted.


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