[Lex Computer & Tech Group/LCTG] Meeting Reminder: At Zoom Address 972 6146 0830. Black Holes, Vortex Rings, and More. On Wednesday, April 21, 2021 at 10AM. Lexington Computer and Technology Group Online Meetings via Zoom

Jonathan Goode jonathan.goode at gmail.com
Sun Apr 18 09:12:19 PDT 2021


(NOTE: Initial Reminder.)



*Apr 21, 2021*








*>Black Holes* by Andrea Ghez (2020 Nobel Prize winner in Physics).  link;
50min <https://youtu.be/YcPPGVigvZk> Given at the World Science Festival

*>Vortex Rings Colliding* 3-year effort to video two vortex rings colliding
in super slow motion.  link; 8min <https://youtu.be/EVbdbVhzcM4>

> *Synchronization* link; 20min <https://youtu.be/t-_VPRCtiUg>
> *About the Suez Stuck Ship* link; 8min
<https://www.youtube.com/watch?v=8RxmRw1kCrc>



*SPECIAL NOTE - **Links to many of our previous sessions are available
online at http://lctg.toku.us/ <http://lctg.toku.us/>, thanks to the
diligence of Steve Isenberg. This includes the Mars Landing presentation of
February 24.*



We, the Lexington Computer and Technology Group,  will meet Wednesday at
the usual 10AM Eastern Time, BUT ONLINE, using the Zoom Video Conferencing
Application, facilitated by Steve Isenberg.

There is an instruction page at https://toku.us/zoomish but note that the
URL and phone number shown are examples.



Sometime after 9:45AM on Wednesday, choose one of the following options:

   - If you have the Zoom application installed, start it and join meeting
   with ID 972 6146 0830
   - From your browser, go to: https://zoom.us/j/97261460830
   - From your smartphone, tap this: +16468769923,,97261460830
   - From a “dumb” telephone, call 1 646 876 9923 and enter meeting ID: 972
   6146 0830

Once the connection is established, you may need to locate and use the
on-screen controls that turn on the sound and the video. You should be able
to see and hear others and they should be able to see and hear you, if you
have a camera and microphone (each of which you can unmute selectively).



If this email wasn't addressed to you and you would like to join the group,
or if you have a friend or colleague who might also be interested in
joining, it's easy.  Ask them to go to the group's wiki page at
http://LCTG.toku.us and follow the simple instructions under "Join the
Email List".  By being a member of the group you'll get reminders of
upcoming meetings and infrequent related messages. No advertising.  The
list is tightly managed.

Membership is free and given that all meetings are using Zoom you only need
to be connected to the Internet to join.  It's ok to join from anywhere you
can get a decent Internet connection, even if you're in orbit around Earth
or on another planet or a moon (if you're connecting from somewhere not on
Earth, we'd like to chat).

*Below are our plans for Upcoming Meetings. For more schedule information,
please refer to https://wiki.toku.us/doku.php?id=lctg_speaker_schedule
<https://wiki.toku.us/doku.php?id=lctg_speaker_schedule>  We will continue
to have an online presentation (almost) every Wednesday until it is prudent
for us to resume meeting in person.*

*Apr 28, 2021*










*Composition of Stars* Cacelia Payne-Gaposhkin would have received a Nobel
prize for figuring out what stars are made of, in a fairer world.  link
<https://youtu.be/BiNAAbRqFYQ> (John Rudy) from wikipedia: *a British-born
American astronomer and astrophysicist who proposed in her 1925 doctoral
thesis that stars were composed primarily of hydrogen and helium. Her
groundbreaking conclusion was initially rejected because it contradicted
the scientific wisdom of the time, which held that there were no
significant elemental differences between the Sun and Earth. Independent
observations eventually proved she was correct. (1h4m)*

*May 5, 2021*



















*Space Debris: A Big Problem* (Georg Kirchner)


*When the first satellites were launched some 60 years ago, space was more
or less empty. However, the ever increasing launching activities since that
now have created a rather crowded environment above our heads: More than
30.000 space debris objects – old / defunct satellites, upper stages of
rockets, remaining parts after explosions of collisions etc. – are now
orbiting in different altitudes, tracked by radar, laser and passive
optical telescopes. The possibility of collisions is already rather high:
Collision warning systems create already more than 1000 warnings per day
(!) of close encounters between 2 objects – and sometimes this is TOO close
– and a collision between two space debris objects, at velocities of 27.000
km/h, creates several 1000 new space debris parts… Satellite Laser Ranging
(SLR) has demonstrated during the last years the capability of tracking
such debris objects, helping to determine their accurate orbit, and also
their tumbling motions – important features if you want to catch an old
upper stage, and remove it from space. *Dr. Georg Kirchner is a group
leader at the Space Research Institute, Department of Satellite Geodesy,
Austrian Academy of Sciences in Graz, Austria.
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