Sunday, March 27, 2011
Friday, March 18, 2011
Wednesday, March 16, 2011
THE SCIENCE BEHIND A SUNSET
"As a ray of white sunlight travels through the atmosphere to an observer, some of the colors are scattered out of the beam by air molecules and airborne particles, changing the final color of the beam the viewer sees. Because the shorter wavelength components, such as blue and green, scatter more strongly, these colors are preferentially removed from the beam.
At sunrise and sunset when the path through the atmosphere is longer, the blue and green components are removed almost completely leaving the longer wavelength orange and red hues we see at those times. The remaining reddened sunlight can then be scattered by cloud droplets and other relatively large particles to light up the horizon red and orange.
The removal of the shorter wavelengths of light is due to Rayleigh scattering by air molecules and particles much smaller than the wavelength of visible light (less than 50 nm in diameter). The scattering by cloud droplets and other particles with diameters comparable to or larger than the sunlight's wavelengths (> 600 nm) is due to Mie scattering and is not strongly wavelength-dependent. Mie scattering is responsible for the light scattered by clouds, and also for the daytime halo of white light around the sun (forward scattering of white light). Without Mie scattering at sunset and sunrise, the sky along the horizon has only a dull reddish appearance, while the rest of the sky remains mostly blue and sometimes green.
At sunrise and sunset when the path through the atmosphere is longer, the blue and green components are removed almost completely leaving the longer wavelength orange and red hues we see at those times. The remaining reddened sunlight can then be scattered by cloud droplets and other relatively large particles to light up the horizon red and orange.
The removal of the shorter wavelengths of light is due to Rayleigh scattering by air molecules and particles much smaller than the wavelength of visible light (less than 50 nm in diameter). The scattering by cloud droplets and other particles with diameters comparable to or larger than the sunlight's wavelengths (> 600 nm) is due to Mie scattering and is not strongly wavelength-dependent. Mie scattering is responsible for the light scattered by clouds, and also for the daytime halo of white light around the sun (forward scattering of white light). Without Mie scattering at sunset and sunrise, the sky along the horizon has only a dull reddish appearance, while the rest of the sky remains mostly blue and sometimes green.
Sunset colors are typically more brilliant than sunrise colors, because the evening air contains more particles than morning air."
This Thursday the sun will rise and set exactly 12 hours apart.
Thursday, March 3, 2011
SPRING IS IN THE AIR!
I heard a thousand blended notes,
While in a grove I sate reclined,
In that sweet mood when pleasant thoughts
Bring sad thoughts to the mind.
To her fair works did Nature link
The human soul that through me ran;
And much it grieved my heart to think
What man has made of man.
Through primrose tufts, in that green bower,
The periwinkle trailed its wreaths;
And ’tis my faith that every flower
Enjoys the air it breathes.
The birds around me hopped and played,
Their thoughts I cannot measure:--
But the least motion which they made
It seemed a thrill of pleasure.
The budding twigs spread out their fan,
To catch the breezy air;
And I must think, do all I can,
That there was pleasure there.
If this belief from heaven be sent,
If such be Nature’s holy plan,
Have I not reason to lament
What man has made of man?
While in a grove I sate reclined,
In that sweet mood when pleasant thoughts
Bring sad thoughts to the mind.
To her fair works did Nature link
The human soul that through me ran;
And much it grieved my heart to think
What man has made of man.
Through primrose tufts, in that green bower,
The periwinkle trailed its wreaths;
And ’tis my faith that every flower
Enjoys the air it breathes.
The birds around me hopped and played,
Their thoughts I cannot measure:--
But the least motion which they made
It seemed a thrill of pleasure.
The budding twigs spread out their fan,
To catch the breezy air;
And I must think, do all I can,
That there was pleasure there.
If this belief from heaven be sent,
If such be Nature’s holy plan,
Have I not reason to lament
What man has made of man?
William Wordsworth, 1798
Lines Written in Early Spring
Subscribe to:
Posts (Atom)