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<p class="MsoNormal" style="margin:0in 0in 0.0001pt;font-size:10pt;font-family:"Calibri","sans-serif""><span style="font-size:12pt;font-family:"Times New Roman","serif"">(NOTE: Initial Reminder.)<span></span></span></p>
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<p class="MsoNormal" style="margin:0in 0in 0.0001pt;font-size:10pt;font-family:"Calibri","sans-serif""><b><span style="font-size:14pt;font-family:"Times New Roman","serif"">Apr 21,
2021<span></span></span></b></p>
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<p class="MsoNormal" style="margin:0in 0in 0.0001pt;font-size:10pt;font-family:"Calibri","sans-serif""><b><span style="font-size:14pt;font-family:"Times New Roman","serif"">>Black
Holes</span></b><span style="font-size:14pt;font-family:"Times New Roman","serif""> by Andrea Ghez (2020 Nobel Prize winner in
Physics).
<a href="https://youtu.be/YcPPGVigvZk" class="gmail-urlextern" title="https://youtu.be/YcPPGVigvZk" rel="ugc nofollow">link; 50min</a> Given at the World Science Festival<span></span></span></p>
<p class="MsoNormal" style="margin:0in 0in 0.0001pt;font-size:10pt;font-family:"Calibri","sans-serif""><b><span style="font-size:14pt;font-family:"Times New Roman","serif"">>Vortex
Rings Colliding</span></b><span style="font-size:14pt;font-family:"Times New Roman","serif""> 3-year effort to video two vortex rings
colliding in super slow motion.
<a href="https://youtu.be/EVbdbVhzcM4" class="gmail-urlextern" title="https://youtu.be/EVbdbVhzcM4" rel="ugc nofollow">link; 8min</a><span></span></span></p>
<p class="MsoNormal" style="margin:0in 0in 0.0001pt;font-size:10pt;font-family:"Calibri","sans-serif""><span style="font-size:14pt;font-family:"Times New Roman","serif"">> <b>Synchronization</b> <a href="https://youtu.be/t-_VPRCtiUg" title="https://youtu.be/t-_VPRCtiUg" style="color:blue;text-decoration:underline"><span style="color:windowtext;text-decoration:none">link; 20min</span></a>
<br>
> <b>About the Suez Stuck Ship</b> <a href="https://www.youtube.com/watch?v=8RxmRw1kCrc" title="https://www.youtube.com/watch?v=8RxmRw1kCrc" style="color:blue;text-decoration:underline"><span style="color:windowtext;text-decoration:none">link; 8min</span></a><span></span></span></p>
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<p class="MsoNormal" style="margin:0in 0in 0.0001pt;font-size:10pt;font-family:"Calibri","sans-serif""><span style="font-size:12pt;font-family:"Times New Roman","serif""><span> </span></span></p>
<p class="MsoNormal" style="margin:0in 0in 0.0001pt;font-size:10pt;font-family:"Calibri","sans-serif""><b><i><span style="font-size:12pt;font-family:"Times New Roman","serif";color:black">SPECIAL NOTE - </span></i></b><i><span style="font-size:12pt;font-family:"Times New Roman","serif";color:black">Links to many of our previous sessions are
available online at <a href="http://lctg.toku.us/" target="_blank" style="color:blue;text-decoration:underline"><span style="color:blue">http://lctg.toku.us/</span></a>, thanks to the diligence of
Steve Isenberg. This includes the Mars Landing presentation of February 24.<span></span></span></i></p>
<p class="MsoNormal" style="margin:0in 0in 0.0001pt;font-size:10pt;font-family:"Calibri","sans-serif""><span style="font-size:12pt;font-family:"Times New Roman","serif""><span> </span></span></p>
<p class="MsoNormal" style="margin:0in 0in 0.0001pt;font-size:10pt;font-family:"Calibri","sans-serif""><span style="font-size:13.5pt;font-family:"Times New Roman","serif";color:black">We, the Lexington
Computer and Technology Group,
<span style="font-size:13.5pt;font-family:"Times New Roman","serif";color:black">will meet Wednesday at the
usual 10AM Eastern Time,</span>
BUT
ONLINE, using the Zoom Video Conferencing Application, facilitated by Steve
Isenberg. </span><span style="font-size:12pt;font-family:"Times New Roman","serif""><span></span></span></p>
<p class="MsoNormal" style="margin:0in 0in 0.0001pt;font-size:10pt;font-family:"Calibri","sans-serif""><span style="font-size:13.5pt;font-family:"Times New Roman","serif";color:black">There is an instruction
page at <a href="https://toku.us/zoomish" target="_blank" style="color:blue;text-decoration:underline"><span style="color:blue">https://toku.us/zoomish</span></a> but note that the URL and
phone number shown are examples.</span><span style="font-size:12pt;font-family:"Times New Roman","serif""><span></span></span></p>
<p class="MsoNormal" style="margin:0in 0in 0.0001pt;font-size:10pt;font-family:"Calibri","sans-serif""><span style="font-size:12pt;font-family:"Times New Roman","serif""><span> </span></span></p>
<p class="MsoNormal" style="margin:0in 0in 0.0001pt;font-size:10pt;font-family:"Calibri","sans-serif""><span style="font-size:13.5pt;font-family:"Times New Roman","serif";color:black">Sometime after 9:45AM on
Wednesday, choose one of the following options:</span><span style="font-size:12pt;font-family:"Times New Roman","serif""><span></span></span></p>
<ul style="margin-bottom:0in" type="disc"><li class="MsoNormal" style="margin:0in 0in 0.0001pt;font-size:10pt;font-family:"Calibri","sans-serif""><span style="font-size:13.5pt;font-family:"Times New Roman","serif";color:black">If you have the Zoom application installed, start it and join
meeting with ID 972 6146 0830</span><span style="font-size:12pt;font-family:"Times New Roman","serif""><span></span></span></li><li class="MsoNormal" style="margin:0in 0in 0.0001pt;font-size:10pt;font-family:"Calibri","sans-serif""><span style="font-size:13.5pt;font-family:"Times New Roman","serif";color:black">From your browser, go to: <a href="https://zoom.us/j/97261460830" target="_blank" style="color:blue;text-decoration:underline"><span style="color:blue">https://zoom.us/j/97261460830</span></a></span><span style="font-size:12pt;font-family:"Times New Roman","serif""><span></span></span></li><li class="MsoNormal" style="margin:0in 0in 0.0001pt;font-size:10pt;font-family:"Calibri","sans-serif""><span style="font-size:13.5pt;font-family:"Times New Roman","serif";color:black">From your smartphone, tap this: +16468769923,,97261460830</span><span style="font-size:12pt;font-family:"Times New Roman","serif""><span></span></span></li><li class="MsoNormal" style="margin:0in 0in 0.0001pt;font-size:10pt;font-family:"Calibri","sans-serif""><span style="font-size:13.5pt;font-family:"Times New Roman","serif";color:black">From a “dumb” telephone, call 1 646 876 9923 and enter
meeting ID: 972 6146 0830 </span><span style="font-size:12pt;font-family:"Times New Roman","serif""><span></span></span></li></ul>
<p class="MsoNormal" style="margin:0in 0in 0.0001pt;font-size:10pt;font-family:"Calibri","sans-serif""><span style="font-size:13.5pt;font-family:"Times New Roman","serif";color:black">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).</span><span style="font-size:12pt;font-family:"Times New Roman","serif""><span></span></span></p>
<p class="MsoNormal" style="margin:0in 0in 0.0001pt;font-size:10pt;font-family:"Calibri","sans-serif""><span style="font-size:12pt;font-family:"Times New Roman","serif""><span> </span></span></p>
<p class="MsoNormal" style="margin:0in 0in 0.0001pt;font-size:10pt;font-family:"Calibri","sans-serif""><span style="font-size:12pt;font-family:"Trebuchet MS","sans-serif";color:rgb(11,83,148)">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 </span><span style="font-size:12pt;font-family:"Times New Roman","serif""><a href="http://LCTG.toku.us" target="_blank" style="color:blue;text-decoration:underline"><span style="font-family:"Courier New";color:blue">http://LCTG.toku.us</span></a></span><span style="font-size:12pt;font-family:"Courier New";color:rgb(11,83,148)"> </span><span style="font-size:12pt;font-family:"Trebuchet MS","sans-serif";color:rgb(11,83,148)">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.</span><span style="font-size:12pt;font-family:"Times New Roman","serif""><span></span></span></p>
<p class="MsoNormal" style="margin:0in 0in 0.0001pt;font-size:10pt;font-family:"Calibri","sans-serif""><span style="font-size:12pt;font-family:"Trebuchet MS","sans-serif";color:rgb(11,83,148)">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).</span><span style="font-size:12pt;font-family:"Times New Roman","serif""><span></span></span></p>
<p class="MsoNormal" style="margin:0in 0in 0.0001pt;font-size:10pt;font-family:"Calibri","sans-serif""><b><i><span style="font-size:18pt;font-family:"Times New Roman","serif";color:black">Below are our plans for Upcoming Meetings. For
more schedule information, please refer to <a href="https://wiki.toku.us/doku.php?id=lctg_speaker_schedule" target="_blank" style="color:blue;text-decoration:underline"><span style="color:blue">https://wiki.toku.us/doku.php?id=lctg_speaker_schedule</span></a>
We will continue to have an online presentation (almost) every Wednesday until
it is prudent for us to resume meeting in person.<span></span></span></i></b></p>
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<p class="MsoNormal" style="margin:0in 0in 0.0001pt;font-size:10pt;font-family:"Calibri","sans-serif""><b><span style="font-size:14pt;font-family:"Times New Roman","serif"">Apr 28,
2021<span></span></span></b></p>
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<p class="MsoNormal" style="margin:0in 0in 0.0001pt;font-size:10pt;font-family:"Calibri","sans-serif""><b><span style="font-size:14pt;font-family:"Times New Roman","serif"">Composition
of Stars</span></b><span style="font-size:14pt;font-family:"Times New Roman","serif""> Cacelia Payne-Gaposhkin would have received a
Nobel prize for figuring out what stars are made of, in a fairer world.
<a href="https://youtu.be/BiNAAbRqFYQ" class="gmail-urlextern" title="https://youtu.be/BiNAAbRqFYQ" rel="ugc nofollow">link</a>
(John Rudy) </span><span style="font-size:14pt;font-family:"Times New Roman","serif"">from
wikipedia: <i>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. <span>(1h4m)</span></i><b><span><span></span></span></b></span></p>
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<p class="MsoNormal" style="margin:0in 0in 0.0001pt;font-size:10pt;font-family:"Calibri","sans-serif""><b><span style="font-size:14pt;font-family:"Times New Roman","serif"">May 5,
2021<span></span></span></b></p>
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<p class="MsoNormal" style="margin:0in 0in 0.0001pt;font-size:10pt;font-family:"Calibri","sans-serif""><b><span style="font-size:14pt;font-family:"Times New Roman","serif""><span> </span></span></b></p>
<p class="MsoNormal" style="margin:0in 0in 0.0001pt;font-size:10pt;font-family:"Calibri","sans-serif""><b><span style="font-size:14pt;font-family:"Times New Roman","serif""><span><br></span></span></b></p><p class="MsoNormal" style="margin:0in 0in 0.0001pt;font-size:10pt;font-family:"Calibri","sans-serif""><b><span style="font-size:14pt;font-family:"Times New Roman","serif""><span> <br></span></span></b></p>
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<p class="MsoNormal" style="margin:0in 0in 0.0001pt;font-size:10pt;font-family:"Calibri","sans-serif""><b><span style="font-size:14pt;font-family:"Times New Roman","serif""><span> </span></span></b></p>
<p class="MsoNormal" style="margin:0in 0in 0.0001pt;font-size:10pt;font-family:"Calibri","sans-serif""><b><span style="font-size:14pt;font-family:"Times New Roman","serif""><span> </span></span></b></p>
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<td style="width:80.62%;padding:0.75pt" width="80%">
<p class="MsoNormal" style="margin:0in 0in 0.0001pt;font-size:10pt;font-family:"Calibri","sans-serif""><b><span style="font-size:14pt;font-family:"Times New Roman","serif"">Space
Debris: A Big Problem</span></b><span style="font-size:14pt;font-family:"Times New Roman","serif""> (Georg Kirchner) <br>
<i>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… <br>
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. <br>
</i>Dr. Georg Kirchner is a group leader at the Space Research Institute,
Department of Satellite Geodesy, Austrian Academy of Sciences in Graz,
Austria.<span></span></span></p>
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