Category Archives: Encyclopedia Entry

Encyclopedia Entry #2 – Ball Lightning

Ball lightning is a mysterious phenomenon that occurs during a thunderstorm, and is an electrical discharge that lasts longer than regular lightning.  However, it’s quite rare and very few recorded instances of it are available.  In July 2012, scientists from Northwest Normal University in Lanzhou, China, recorded the spectrum of ball lightning, and published their results in January 2014.

Ball lightning spectrum.  File is public domain, available at Wikipedia.
Ball lightning spectrum. File is public domain, available at Wikipedia.

5 Interesting Facts

1. The ball lightning observed in China was seen from 900 metres away, and 1.64 seconds of video of the lightning was recorded.  The ball lightning traveled horizontally at a speed of 8.6 m/s. Source is here.

2. The spectrum revealed that it contained neutral silicon, calcium, iron, nitrogen, and oxygen.  Regular lightning’s spectrum reveals ionized nitrogen.

3. Ball lightning is mysterious.  Although it has been observed, it’s rarely been observed naturally in a setting where scientists can take readings.  However, there are many hypotheses about the cause of ball lightning.  There is no consensus yet.

4. The characteristics of observed ball lightning is quite varied.  There are different colours, shapes, and sizes.  Many are observed to be rotating, but few are observed to give off heat.  They tend to be attracted to conducting metals.  They often appear at the same time as cloud-to-ground lightning.  They’ve also been known to appear in buildings, aircraft, and pass through walls with no damage. Read all about it here in a New Scientist article.

5. R. C. Jennison of the Electronics Laboratory at the University of Kent observed ball lightning traveling through the aircraft he was in.  During a storm, the aircraft was struck by lightning, and a few seconds later, a 20cm diameter sphere of ball lightning floated down the aircraft and passed within 50cm of him.  Read his account here.

For more information, check the Wikipedia article.

Encyclopedia Entry #1 – Aurora

Welcome to the inaugural Encyclopedia Entry, where I will give you some brief, but interesting facts about various topics.  In this week’s entry, I talk about something that’s been in the news, and should be peaking in a few hours, aurora.

Aurora over Amundsen-Scott South Pole Station
Aurora over Amundsen-Scott South Pole Station

Aurorae are light emissions in the atmosphere caused by oxygen and nitrogen gaining an electron or going from an excited state to ground state.  These atoms are hit by energized particles from the sun that enter the atmosphere and are directed to the polar regions by the Earth’s magnetic field.

5 Interesting Facts

1.  Aurorae come in a variety of colours.  Usually they’re green, but they can also be red or blue.  Green aurorae are caused by oxygen atoms returning to ground state.  Red can also be caused by the same mechanism, but with a different energy level.  Blue is caused by nitrogen atoms regaining an electron after being ionized, while red is caused by nitrogen returning to ground state. For more, see here.

2.  Aurora borealis is visible in the northern hemisphere.  Aurora australis is visible in the southern hemisphere.

3.  Aurorae may cause sounds, but this is rare.  It has been observed by researchers. For more information, check this out.

4.  Aurorae are very strong and bright on Jupiter and Saturn, and have also been observed by telescope on Uranus and Neptune.  Venus and Mars also have aurorae, but are very diffuse due to the lack of a significant magnetic field.  Also, Io, Europa, and Ganymede have been observed to have aurorae. See here.

5. Aurorae are at their most frequent and strongest during the sun’s sunspot peak and the following 3 years.  The last peak was May 2013, so we are currently in an active period.

For more information, check out the Wikipedia article.