Wednesday, January 23, 2013

The original diss song?

"My Country, 'Tis of Thee", also known as "America" served as the de facto national anthem of the United States before the adoption of "The Star-Spangled Banner" as the official anthem in 1931. Written in 1831, 48 years after the American War of Independence, the song unquestionably takes some shot at the British. Firstly, the melody is the exact same as that of the national anthem of the United Kingdom, "God Save the Queen". The lyrics have a very post-independence-esque feel to them with reoccurring lines about liberty (My country, 'tis of thee, Sweet land of liberty) and freedom ( "My native country, thee, Land of the noble free"). The most telling swipe at the British is the final line of the song; "Protect us by Thy might, Great God our King" which is in clear contrast to the lyrics of the British anthem "God save our gracious Queen, Long live our noble Queen, God save the Queen". The Americans are clearly stating their sole ruler is God and they have no respect for England's earthly monarch who they are free from. This this the world's first "diss song"? Compare the two anthems below and decide for yourself!

Monday, January 21, 2013

Wednesday, January 16, 2013

Precession of the equinoxes

The precession of the Earth's axis has a number of observable effects. First, the positions of the south and north celestial poles appear to move in circles against the space-fixed backdrop of stars, completing one circuit in 25,772 Julian years (2000 rate). Thus, while today the star Polaris lies approximately at the north celestial pole, this will change over time, and other stars will become the "north star". In approximately 3200 years, the star Gamma Cephei in the Cepheus constellation will succeed Polaris for this position. The south celestial pole currently lacks a bright star to mark its position, but over time precession will also cause bright stars to become south stars. As the celestial poles shift, there is a corresponding gradual shift in the apparent orientation of the whole star field, as viewed from a particular position on Earth.

Secondly, the position of the Earth in its orbit around the Sun at the solstices, equinoxes, or other time defined relative to the seasons, slowly changes. For example, suppose that the Earth's orbital position is marked at the summer solstice, when the Earth's axial tilt is pointing directly towards the Sun. One full orbit later, when the Sun has returned to the same apparent position relative to the background stars, the Earth's axial tilt is not now directly towards the Sun: because of the effects of precession, it is a little way "beyond" this. In other words, the solstice occurred a little earlier in the orbit. Thus, the tropical year, measuring the cycle of seasons (for example, the time from solstice to solstice, or equinox to equinox), is about 20 minutes shorter than the sidereal year, which is measured by the Sun's apparent position relative to the stars. Note that 20 minutes per year is approximately equivalent to one year per 25,772 years, so after one full cycle of 25,772 years the positions of the seasons relative to the orbit are "back where they started". (In actuality, other effects also slowly change the shape and orientation of the Earth's orbit, and these, in combination with precession, create various cycles of differing periods; see also Milankovitch cycles. The magnitude of the Earth's tilt, as opposed to merely its orientation, also changes slowly over time, but this effect is not attributed directly to precession.)

For identical reasons, the apparent position of the Sun relative to the backdrop of the stars at some seasonally fixed time, say the vernal equinox, slowly regresses a full 360° through all twelve traditional constellations of the zodiac, at the rate of about 50.3 seconds of arc per year (approximately 360 degrees divided by 25,772), or 1 degree every 71.6 years. FULL ARTICLE