WebProNews

Tag: equinox

  • Time-Lapse Video Captures Northern Lights

    Time-Lapse Video Captures Northern Lights

    Canadian photographer Richard Gottardo recently spent 7 hours in Southern Alberta, capturing the remarkable color changes displayed by the northern lights, or the aurora borealis, which were seen over the Rocky Mountains.

    The aurorae, from the Latin word for “sunrise,” and also the name of the Roman goddess of dawn, is a natural light display in the sky that can be viewed particularly in the high-latitude Arctic and Antarctic regions. The aurora borealis, or aurora australis, as it is known in the southern hemisphere, is caused by the collision of charged particles with atoms in the high altitude atmosphere, also called the thermosphere.

    Below is Gottardo’s clip:

    The colliding particles, which originate in the magnetosphere, are directed by the Earth’s magnetic field into the atmosphere. Most aurorae occur in a small band known as the auroral zone, which is typically 3° to 6° in latitudinal extent, and at all local times or longitudes. The auroral zone is typically 10° to 20° from the magnetic pole, which is defined by the axis of the Earth’s magnetic dipole. Although, during a geomagnetic storm, the auroral zone expands to lower latitudes.

    Below is a clip of the aurora australis, captured by the crew of Expedition 29, on board the International Space Station. The shots were taken on September 17, 2011, during an ascending pass from south of Madagascar to just north of Australia, over the Indian Ocean:

    The aurora borealis most often occurs near the equinoxes. The northern lights have had a number of names throughout history. The Cree Native American tribe of Canada call this phenomenon the “Dance of the Spirits,” an in Medieval Europe, the aurorae were commonly seen to be a sign from God.

    Human persistence of vision allows the playback of roughly 24 pictures per second, in succession, to resemble what can be perceived as being normal motion. The more images inserted into a one second timeline, also called overcranking, the “slower” the scene will appear upon playback. Time-lapse photography, on the other hand, is an extreme form of undercranking, to where a very small amount of frames are run together, producing an illusion of fast motion upon normal playback.

    Image via YouTube.

  • The Equinox and Why Fall Starts Sunday

    The Equinox and Why Fall Starts Sunday

    On Sunday, September 22, the earth’s Northern Hemisphere will move into fall and the Southern Hemisphere will move into spring. The celestial shift that prompts this transition is called an equinox, which happens biannually, around March 21 and September 21.

    While rotating on its polar axis every 24 hours, the earth sees night and day – as well as the annual cycle of seasons caused by its 365.25 orbit around the sun. The equinox (latin for equal night) occurs when the earth’s rotation intersects with its orbit. Because Earth is so huge, its mass creates an extremely powerful gyroscopic effect, causing the poles to mostly point in the same direction (though major earthquakes can cause tiny axis wobbling). The direction the north and south poles are pointing has very important consequences for the change of seasons.

    The poles are tilted 23.4 degrees relative to the earth’s plane of orbit. This tilt always points toward the celestial pole in the sky, making it appear that the sun is moving across the sky at an angle to the celestial equator, from the vantage of Earthlings. Twice a year, the sun crosses the celestial equator, changing the direction the rays of the sun fall on Earth.

    On Sunday, the sun will move from the Northern Hemisphere to the Southern Hemisphere, passing along the earth’s equator, rising exactly in the east and setting exactly in the west. Day and night will be of roughly equal length, hence the equinox name. On Monday, the sun will begin shining more on the southern half of Earth, and less in the north, where autumn will begin. For the next 3 months, the sun will continue to “move” southward, marking the solstice on December 21. The days in the north will gradually become shorter and colder. Though, after the solstice, more sunshine will begin coming northward again.

    In related news, one can still see the tail end of the Harvest Moon (or Full Corn Moon, as Algonquian tribes called it) in the night’s sky. Up until the solstice in December, one also has a chance to check out a “Hunter’s Moon”, a “Blood Moon”, a “Sanguine Moon”, a “Beaver Moon”, a “Frosty Moon”, an “Oak Moon”, a “Cold Moon” and a “Long Nights Moon”, depending on which lunar nomenclature one prefers.

    Image courtesy of Wikimedia Commons.