Yesterday afternoon, I attended a Tweetup at NASA Headquarters in Washington, DC. It was a short event: about an hour for the official program, with brief chances to mingle at the beginning and end, but well worth the trip for me. The main program featured a short presentation from Shuttle Commander Chris Ferguson (Twitter handle: @astro_ferg) and Mission Specialist Sandy Magnus (Twitter handle: @astro_sandy), a video about the last Atlantis launch STS-135 (which Ferguson and Magnus flew on), and a question-and-answer session with the astronauts.
It was very interesting and exciting to be in that crowd. I’m a space fan (obviously), but I’m not as intensely involved as many of the Tweetup crew, some of whom traveled a long distance just for this event — 25 states along with (at least) Canada and Germany were represented, so my measly drive from Richmond seems pretty small by comparison. Many of the participants knew each other from previous Tweetups, or were able to compare notes about other Tweetups they had attended. (By the way, I’m also wait-listed for the Tweetup for the launch of Mars Curiosity, which I really really want to go to, if I can possibly afford it! I wrote a little about Curiosity here.)
A few items from the event:
- Chris Ferguson noted that he used Twitter as a diary during the mission, since there was so little time to think and record real thoughts. Going back over his stream, he was able to recall a lot of what happened, when things were jumbled during the rush and stress of getting things done.
- This mission, the last shuttle flight, was only crewed by 4 people, due to its original intent of being a relief mission for the Space Station. Obviously the shuttle can be operated by a crew that small, but it meant everyone was even busier than usual.
- They did (barely) have time to shoot a stunt video, with the astronauts from the shuttle and Space Station “flying” past each other in the microgravity conditions. Evidently outtake footage exists, which is hilarious. NASA, why do you suppress vital evidence the public needs to see?
On a more serious note, Sandy Magnus spoke eloquently about seeing Earth from space for the first time. Her initial reaction was to say “The atmosphere is so thin!”. It’s really true, if you think about it: we live in the troposphere, the lowest layer of the atmosphere, which is the only one thick enough for us to breathe. The troposphere is only about 17 kilometers high (just shy of 11 miles), compared to the 6400-kilometer radius of Earth: it’s just a little haze surrounding the ball of our world. As Magnus talked about our fragile ecosystems, I thought again of Alice Bell’s Lorax post from yesterday calling for science communicators to speak on behalf of voiceless nature. Magnus holds a Ph.D. in materials science (a discipline on the intersection of physics, chemistry, and engineering), so she has two different platforms from which to speak.
Overall, I loved seeing the community built around spaceflight. Cultures in the internet era are often far-flung: people group together based on common interests rather than accidents of geography. My own community of scientists and science writers exists primarily online, since we live in so many different cities across the world; I regularly communicate with people in New York, British Columbia, London, Edinburgh, and so forth, and haven’t met all of them in “real life” yet. The NASA Tweetup community is another such community, which I appreciate joining now as a newly-minted alum.
Speaking of community, I wrote a three-part series of guest posts for Sheril Kirschenbaum’s Culture of Science Blog. As of this writing, Part I is available; I’ll update to link to Parts II and III when they go live. My topic is scientific isolation — the feeling of being disconnected and sometimes confused by science — and how virtual communities provided by citizen science projects may help alleviate some of that isolation. Please go, read, and comment!
Update: the complete series of guest posts for “Culture of Science” is now up!
6 responses to “From Way Up Here, the Earth is Very Small”
Steve Carlip finally gave me a workable answer to the ring singularity diameter question.
See sci.physics.research (thread on Ring Sing.)
Using Kerr-Schild metric
Circumference of ring sing = (2)/(pi)(angular velocity param.)
I think the ang. vel. param. = (specific ang. momentum)/(inner event horizon^2 + spec. ang. momen.^2). Or: a.v.p. = a/(r+)^2 + a^2
To a first approx., Radius of ring sing. = 1/(pi)^2 (ang. veloc. param.)
For a typical Kerr black hole, R(ring)/R(bh) ~ 0.43, with dependence on “spin”.
1. This result is wrong: the size of the singularity depends on mass as well as spin parameter. The result you state is only for M = 0.
2. This is rather off-topic for the blog post.
“M = 0 case”! I think you are mistaken.
The mass of the black hole is included in the values for the inner event horizon and the specific angular momentum (a = J/M, if you will remember your GR 101).
The angular velocity parameter determines the size of the ring for a given mass. If the spin is zero, you get a point singularity.
I agree M = 0 is a mathematical abstraction, that is used to elucidate the coordinate system in Kerr geometry. (See Wald’s or especially Carroll’s books on the subject.) You can keep a finite and still let M = 0 if J -> infinity at the same time; it’s not physically meaningful, but at least it helps you see how the Kerr geometry works.
Now I may be wrong in my assessment that the suggested solution is true only when M = 0. I haven’t done the whole calculation, since it’s not high on my priority list. The ring singularity isn’t exactly measurable by observers far from the black hole, so I’m really not concerned about its radius. My intuition is that mass does matter in the calculation, because the ring is a real curvature singularity when mass is not zero, but it’s a coordinate singularity when M = 0. Again, I may be wrong about this, so I was a bit hasty to say “wrong wrong wrong”.
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[…] I mentioned before, I spent yesterday at NASA’s Langley Research Facility as part of the NASA Tweetup program. The official version of the event is here, and here’s one of several Flickr pages from the […]