Six ways to find another Earth

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11 Responses to “Six ways to find another Earth”

  1. Craig Landrum says:

    The statement:

    “…Earth would dim the Sun’s light by one part in 12,000; that’s less than a current-generation iPad dims when it shorts a single pixel.”

    This seems incorrect to me. The iPad’s screen is 1024 x 768 = 786,432 pixels. If we assume that we start with all pixels lit, turning one off would dim the screen by a factor of 1 part in 786,432. In other words, I can turn one iPad pixel off every second and it would take a bit over 9 days to go completely dark, whereas if I blocked 1 (of 12,000) of the Sun’s “pixels” every second, it would appear to go dark in 3 hours and 30 minutes or so.

    • Lee Billings says:

      Egads, Craig, you’re totally right. This is why I prefer writing over calculating. I take pains to curb my innumeracy but this is a flagrant, embarrassing error. I backtracked and found what I did wrong in my calculations… Several things, actually. Let me see if I can get this post corrected.

    • Lee Billings says:

      Okay, so it looks like the 1/12000th dimming would actually correspond to about 65 pixels droppings out from the iPad display… Right?

  2. Dewi Morgan says:

    65 works for me. And 65 dead pixels would be really EASY to spot for the human eye, so it sounds unimpressive. But hold it far enough that it’s just a point of light, and have it display an all white web page, apart from the word “ipad” in about 12 point text, in a blink tag. I doubt the naked eye could spot the change in brightness with the blinking (and not just because no self-respecting browser respects that tag).

    If you don’t want to be parted from your ipad from such a distance, shine the light from the ipad screen on the wall, and try to tell the difference in illumination – similar concept.

  3. ElighCS says:

    This is an awesome post.

  4. Anonymous says:

    Great article Lee. Love a good hugeness of space analogy. Look out for an interview with Sara Seager of MIT later today @theurbantimes.

  5. retrojoe says:

    “Of the six main methods for detecting exoplanets, only one, direct imaging, hews to the antiquated notion of observing and studying an object by taking its picture.”

    “Antiquated”? Doesn’t NASA spend billions on projects that directly image space? Isn’t this how objects (comets, asteroids, galaxies etc) continue to be found today?

    • boo says:

      I presume that the terms “retro” and “antiquated” were used in their most accurate sense: visual identification is the very oldest form of astronomical observation. I grant that words with less negative connotations might have been used, but I thought it was a brilliant and thoughtful post.

      I am looking forward to the Kepler data release!

    • chenille says:

      A curious thing, though, is that direct imaging doesn’t seem to tell you very much. At least for the first planet found in visible light, Fomalhaut b, most about what we know about it comes from properties of the surrounding disk. Whereas other techniques can at least give you a good idea of the planet’s orbit and mass.

    • Remez says:

      Finding comets, asteroids and galaxies is very different from finding exoplanets. Looking for an exoplanet next to its home star is like looking for a firefly against a klieg light. The star’s light entirely dominates.

      One clever way to work around this is to create an artificial eclipse of the star. Take the light from the star. Feed it through some optics so that the light wave is flipped upside down–what was once a crest is a trough, and vice versa. Now combine the upside-down light wave with the right-side-up wave, and voila, they cancel each other out. All that’s hopefully left is the firefly-level light from any planets. That’s a really simplified version of events, and actually making the thing work is a lot more time and money. Yet not impossible!

      • retrojoe says:

        I didn’t say that they were the same. In fact I never mentioned exoplanets in my post. I merely took exception to describing the technique as “antiquated” when it is incredibly successful in other areas. It’s a minor point and I don’t think the author intended it that way but it implies obsolescence.

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