Follow Slashdot blog updates by subscribing to our blog RSS feed


Forgot your password?
Compare cell phone plans using Wirefly's innovative plan comparison tool ×
Space Science

Ask The Bad Astronomer 412

Astronomer, author, columnist, and successful populizer of science Phil Plait, perhaps best known as The Bad Astronomer, is a regular sight on Slashdot for his unusual ability to find lucid explanations of esoteric scientific claims and controversies. Phil has graciously agreed to answer Slashdot readers' questions, so ask him below about space, science, debunking conspiracy claims, and anything else that makes sense. Asking more than one question is fine (and encouraged!), but please separate unrelated questions into separate posts, lest your questions be moderated down.
This discussion has been archived. No new comments can be posted.

Ask The Bad Astronomer

Comments Filter:
  • by Anonymous Coward on Monday October 24, 2011 @02:21PM (#37821258)

    Why does matter exist? Why does energy exist?

    Wouldn't it make more sense for the universe to be empty?

  • by earls ( 1367951 ) on Monday October 24, 2011 @02:26PM (#37821316)

    What is the best way to combat pushers of psudeo-science like the Electric Universe?

  • Light pollution (Score:5, Insightful)

    by Frenzied Apathy ( 2473340 ) on Monday October 24, 2011 @02:32PM (#37821388)
    There are a large number of light pollution [] articles to be found on the Sky and Telescope [] website. We amateur astronomers are keenly aware that light pollution isn't just about being able to see more stars from our backyard. Yet, when I mention the subject to friends, family, co-workers, etc, I often get a blank stare. "What's 'light pollution'?" What do you think can/should be done to improve widespread public awareness of light pollution and its effects?
  • Don't Be A dick? (Score:1, Insightful)

    by wbtittle ( 456702 ) on Monday October 24, 2011 @02:32PM (#37821400) Homepage

    How do you make the assessment to jump over threshhold and be dick anyway?

    There are times when it is necessary to ignore the rules.

  • by UberOogie ( 464002 ) on Monday October 24, 2011 @02:36PM (#37821468)
    Given your unique position, I'd like to know your answer to this question:

    What do you think is the currently a bigger threat to legitimate science:
    - The growing wave of anti-intellectualism and anti-science that seemingly rejects science outright on certain issues
    - Or the growing wave of pseudo-science that undercuts science by adopting the trappings of science but none of its procedures?

    Thank you for your time.
  • by vlm ( 69642 ) on Monday October 24, 2011 @02:45PM (#37821604)

    Do you see long term trends in various misconceptions?

    It seems subjectively to me that the "vernal equinox egg" deal was WAY more popular in the 80s. Its a random variable on the timescale of a couple years.

    Other misconceptions, like "the far side of the moon is always dark" or "the moon always rises at sunset and sets at sunrise" has a relatively constant rate of mis-belief over time.

    Another type of misconception is the flash in the pan like the "face on mars" which gets intense media attention for awhile and then fades (permanently?) into obscurity.

    Do you see any general trends in the distribution of the three types of misconceptions over time, like one getting more or less popular or ... maybe due to social media or something?

  • by jd ( 1658 ) <<moc.oohay> <ta> <kapimi>> on Monday October 24, 2011 @03:02PM (#37821880) Homepage Journal

    Dunno about the Bad Astronomer, but *my* conclusion is that everyone would be better served if "ancient alien" and "ghost-hunting" programs were shifted off channels like History and Discovery and onto something dedicated to "off-beat" theories. I disagree with censorship, but I also disagree with mixing educational documentaries and conspiracy theorists on the same channel. You either dilute the value of the educational stuff or you give false credibility to the nutcases.

    This isn't to say that I believe the channels shouldn't air unorthodox views - they should, provided it is good science. Nor am I saying that the channels should show all documentaries that fit the orthodoxy - if it's pseudoscience, it's pseudoscience no matter who it agrees with. In fact, I'd be more worried about bad science that attempts to "prove" something that is true, since that is more likely to pervert the casual viewer's ability to critically reason.

    These "science" channels are a big reason why we're becoming an Idiocracy.

  • by mark-t ( 151149 ) <> on Monday October 24, 2011 @03:04PM (#37821908) Journal
    Initially, a galaxy would be just an enormous cloud of hydrogen, swirling around its gravitational center in essentially random directions. However, owing to the fact that it is not ever perfectly symmetrical, the angular momentum of the matter will not perfectly cancel out and there will always be some net angular momentum in one direction (which itself may have precession). Matter will thus have a tendency to be drawn into a plane perpendicular to the axis of the galaxy's net angular momentum through the pull of gravity... and the more matter that gets pulled into the plane, the faster it pulls other matter into the plane. Within a relatively short time (in cosmological terms), you end up with a distinct accretion disk forming around the gravitational center of the hydrogen cloud. This accretion disk eventually forms individual stars (although it's possible that stars could form outside of the disk, it is unlikely because it would not generally be close enough to enough other matter to get large enough for fusion to begin). Each star, in turn, may develop its own accretion disk that becomes the planets that circle it through the exact same process.
  • by pavon ( 30274 ) on Monday October 24, 2011 @04:15PM (#37823130)

    Whenever I research this, I come back to the "galactic rotation problem" as the most solid evidence.

    That isn't the most solid evidence. It was just the first evidence, and if it was the only evidence then Dark Matter would not be preferred over the idea of a modified gravitational theory. Since then there have been two major additional forms of evidence for dark matter. The first is gravitational lensing.

    According to General Relativity, mass bends bends light that passes by it. We have measured this effect before with objects of known mass, and the predictions of GR are dead on. Astronomers have looked at how strongly light is bent when passing by large galaxies, and used this to compute the mass of the galaxy. The numbers they get are much greater than the mass of the visible material, and more importantly match up very closely with the estimates of dark matter mass obtained by looking at rotational curves.

    The most outstanding evidence of this is from the Bullet Cluster. Here two galaxies had passed through each other, and you can see how the different types of matter were slowed down by different amounts depending on how likely they were to collide. The gas clouds were slowed the most, and the large structures (stars, etc) slowed down less. But if you look at the gravitational lensing, you see that there is a big chunk of non-visible mass that was not slowed down by the collision at all. This is exactly what you would expect to see if the galaxies contained non-baryonic dark matter, and can't be explained by modified gravity at all.

    The second major evidence is the cosmic microwave background radiation. I don't pretend to understand this, and thus won't try to expound, except to note that the ratio of baryonic matter to non-baryonic matter found using the CMBR also agrees with the dark matter estimates found using galaxy rotation curves and gravitational lensing.

    So we have three drastically different ways of indirectly measuring the same thing, and they all come up with the same result. That is pretty strong evidence in my book.

    How long do we have to put up with the notion of "Dark Matter"?

    My guess is quite a long time, because it is almost certainly correct. Hopefully though, we will have direct evidence of dark matter with the next few decades, which should make it less annoying :)

"They that can give up essential liberty to obtain a little temporary saftey deserve neither liberty not saftey." -- Benjamin Franklin, 1759