An overview of the Chandra mission and goals, Chandra's namesake, top 10 facts.
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Overview of X-ray Astronomy and X-ray sources: black holes to galaxy clusters.
All Chandra images released to the public listed by date & by category
Current Chandra press releases, status reports, interviews & biographies.
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A collection of illustrations, animations and video.
Chandra discoveries in an audio/video format.
Contrary To Belief
June 2, 2008 ::
"Put it before them briefly so they will read it, clearly so they will appreciate it, picturesquely so they will remember it and, above all, accurately so they will be guided by its light." Joseph Pulitizer.
One of the primary goals of communicating science to the public is to capture the excitement of scientific discoveries while trying to follow the advice of Joseph Pulitizer. Writers and speakers often fall short of this goal and say too much, use too much jargon, or use picturesque language carelessly, as in saying that a neutron star is "incredibly dense," when in fact the data have shown that the density is credible.
More problematic is the use of the word "believe," as in "Astronomers believe that most galaxies harbor massive black holes at their centers," or "Scientists believe that elements such as oxygen, silicon and sulfur are dispersed into the galaxy primarily by the explosion of massive stars."
In most cases, what is meant by these statements is something like "Based on the evidence at hand, this is what most scientists think is going on, and there is no good evidence to indicate otherwise." It is much briefer to say "scientists believe," but not nearly as accurate.
For many readers, the word "believe" could indicate a statement of faith, as in "He believes in God." Or, it could be a statement that involves an educated guess, as in "I believe the Red Sox will win the World Series again this year."
The latter is closer to what is meant, but does not reflect the state of scientific knowledge, which is well beyond an educated guess. In fact, the evidence is strong that supernovas play a critical role in the dispersal of heavy elements, and that supermassive black holes exist in the centers of most galaxies. It is healthy to maintain a little skepticism, but not to the point of inaccurately describing the state of understanding.
To say that "The evidence indicates that most galaxies harbor massive black holes... " would seem to be a good compromise that satisfies both the brevity and accuracy criteria.
The search for knowledge using the scientific method proceeds in a random walk, with steps that can be forward, backward, or sideways. It moves along a broad path from having an idea to thinking something might be true, to being so sure as to say that we know it is true. For example, we know that gravity acts throughout the universe, and that we can use our knowledge of the law of gravity to launch satellites and send them to planets in the outer reaches of the solar system.
Progress along the path from ideas to knowledge is driven by applying the steps of the scientific method - observation, hypothesis, and testing with more observations or experiments. Several hypotheses are almost always proposed to explain initial observations, and further observations are undertaken to distinguish between hypotheses.
For scientists who formulate hypotheses, the sobering fact is that most of their hypotheses will turn out to be wrong. But that’s not necessarily a bad thing. As Nobel laureate Frank Wilczek said, "If you don't make mistakes, you are not working on hard enough problems."
The process of developing an idea into a working hypothesis and building models to test the hypothesis can take years or even decades, before it finally becomes a theory.
More on theories next time. In the meantime, the evidence indicates that we should be more careful and use "The evidence indicates..." or words to that effect, instead of "Scientists believe..." when describing the state of scientific understanding.
Part II: It Is Not Just a Theory... It Is a Theory!