• Mona Evans

    Precession changes the pole star. Earth's axis has a little wobble in it, so over 26,000 years the axis points to a slightly different area of sky. During that time the north pole star also changes. In 12,000 years it will point towards Vega. Mona Evans, "Ecliptic and Equinoxes" http://www.bellaonline.com/articles/art20530.asp

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Star trails and aurora. Stunning. (Image Credit: Mike Taylor) Mona Evans, "Star-gazing - Seeing in Dim Light" www.bellaonline.c...

Wavelight, still from the video. We can see the star trails in the sky and the wave patterns on the Jurassic sandstone rocks. (Credit: Gavin Heffernan & Harun Mehmedinović) Music: NEBULA by Mark Petiie.

Wavelight. Star trails and wave formations in sandstone make for a remarkable timelapse at the Wave in Arizona. (Credit: Gavin Heffernan and Harun Mehmedinović) Music: "Nebula" by Mark Petrie.

Perseid meteor and ISS, August 13, 2012. (Photo: Martin Popek) The immediately obvious thing is the star trails, but the horizontal line cutting across the trails is the International Space Station going overhead. There is a bright Perseid on the left hand side of the picture. The Perseid meteors are tiny fragments of the debris of comet 109P/Swift-Tuttle. ©Mona Evans, "Meteor Shower - the Perseids" www.bellaonline.c....

Rocket Streak and Star Trails. (Image Credit & Copyright: Mike Killian) 2014-01-23. Star trails are the result of the Earth's rotation. This is also why the Atlas V rocket carrying a NASA satellite follows a path arcing east. Launching east adds rotational velocity to the rocket and reduces the fuel used. The satellite was launched into a geostationary orbit, so its orbital period matches Earth's rotation. It will appear to be motionless.

Star trails above ALMA telescope in Chile. In the southern hemisphere, as Earth turns, stars seem to move in circles around the south celestial pole in the constellation Octans between the Southern Cross & the Magellanic Clouds. ALMA is the most powerful existing telescope for observing the cool Universe — molecular gas & dust, relic radiation of the Big Bang. (ESO/B. Tafreshi (twanight.org)

Star trails and Geminids above Circle of Abstract Rituals. 2013-12-13. (Credit: Jason Hullinger) Sculpture by Jeff Frost.

Star trails, Warrenton, VA, USA. (Credit: John Chumack) Polaris, is the stationary point over a Sequoia tree. This is a 30-minute exposure. Longer exposures give more dramatic effects. more dramatic the effect!”

The axis is tilted 23.5 degrees with respect to the path of Earth's orbit around the Sun (the ecliptic). Mona Evans, "Teaching Why We Have Day & Night", www.bellaonline.c...

The Earth turns. Animation showing how this causes alternating night and day. (Credit: PlanetObserver) Mona Evans, "Teaching Why We Have Night and Day", www.bellaonline.c...

Relative motion on carousel. The riders go up and down while moving clockwise - as viewed from the sidelines. Although this video shows the riders moving up and down, some shots that include the background make it looks as though it's the background moving counterclockwise, not the carousel moving clockwise. Mona Evans, "Teaching Why We Have Night & Day", www.bellaonline.c...

Relative velocity of trains. (Credit: Frank McCulley) Think of being on a train when another train is alongside. You start to move. No! Whoops! It's the othe train that's moving. This video shows relative motion. There are two trains, even though you only see one of them. Which one is moving and which one is stationary? And how does this change during the video? Mona Evans, "Teaching Why We Have Day & Night". www.bellaonline.c...

Precession changes the pole star. Earth's axis has a little wobble in it, so over 26,000 years the axis points to a slightly different area of sky. During that time the north pole star also changes. In 12,000 years it will point towards Vega. Mona Evans, "Ecliptic and Equinoxes" www.bellaonline.c...

Meteor-like star trails at Captain Cook’s Monument, North Yorkshire, England. (Credit: Peter Greig) Peter Greig and David Relph took these 30-second exposures, giving the stars the appearance of a meteor shower.

Star Trails over ruined Viking church in Vallentuna Sweden. [Image Credit & Copyright: P-M Hedén (Clear Skies, TWAN)] Polaris is at the center of the circular trails and you can also see a Geminid meteor cutting across the star trails. ©Mona Evans, “Polaris -10 Fascinating Facts” www.bellaonline.c...

Teimareh Petroglyphs and Star Trails [Image Credit & Copyright: Babak Tafreshi (TWAN)] Polaris is at the center of the trails. ©Mona Evans, “Polaris -10 Fascinating Facts” www.bellaonline.c...

Star trails over Castle Kriebstein in Saxony, Germany. Medieval Kriebstein Castle is situated in Middle Saxony, right at the center of the triangle between the cities of Dresden, Chemnitz and Leipzig, and the first official record for the castle is dated October 4, 1384. Built on a steep rock, its 147 foot tall tower soars over the River Zschopau. Photo by Christoph Schaarschmidt.

Nights in Michigan. (Image credit & copyright: Michael A. Rosinski). This was Highly Commended in the Earth & Sky section of the Astronomy Photographer of the Year 2012. If you point your camera at the sky and leave the shutter open, the stars will form star trails as the Earth turns. If you do it on a summer night in Michigan, you may get yellow flecks crossing them - fireflies. Delightful picture!