| Topic: |
Science > Physics |
| User: |
"Dr. Jai Maharaj" |
| Date: |
09 Aug 2004 09:49:11 PM |
| Object: |
UNDERSTANDING THE UNIVERSE WITH PROF YASH PAL |
UNDERSTANDING THE UNIVERSE
WITH PROF YASH PAL
The Tribune
Thursday, September 11, 2003
When travelling by plane from Mumbai to Delhi at about 6
p.m. on January 4 this year I observed from my left
window a straight bright line of seven colours running
parallel to us. The plane was at a height of about 11
kilometres. Kindly explain this observation at a time
when it was quite dark outside.
I agree it is one of the joys of flying north south when
the land has lost the sun but the upper atmosphere still
gets some light. Looking towards the horizon late during
a winter evening you see the light that is strongly
scattered during passage through the long path in the air
of our spherical earth. The scattering is wavelength
dependent. The indigo-blue is scattered about 16 times
more than the red. The scattered and refracted light from
the sun that is already below horizon is what comes to
you. The red can travel through the much longer
atmosphere close to the bottom, while the blue is
completely extinguished on that route. As you travel
towards the blue end of the VIBGYOR series of wavelengths
only that light gets through that is coming via paths
where travel through the atmosphere is shorter. For these
also refraction is operative. Thus you end up getting a
ribbon of colours, with red at the bottom and blue at the
top. Remember that in travelling from the sun that is
below horizon light is travelling from denser to the
atmosphere; it bends away from the normal.
The basic phenomenon has the character that is also
exhibited during sunrise and sunset. Everyone sees the
red sunsets. The sky is blue during the day because that
is strongly scattered by the molecules of air. In the
evening the blue is scattered away to make the skies of
others who are further west of us. All this is enhanced
by the conditions under which you made your observation.
Colours up to blue are discernible because it is so dark.
Highly differential molecular scattering and refraction
provided you that treat. The structure of habitat, the
earth, is designed to give us delight. We should never
miss such moments and we should treasure our planet with
all its biological and cultural diversity.
Will oceans ever get extinct due to deposition of decayed
particles on the seabed?
Over long time scales oceans and mountains are
continuously changed and transformed. There was a time, a
few hundred million years ago, when the landmass of India
was in the Southern Hemisphere. There was a big ocean
where most of India is now located. Himalayas did not
exist. This mountain range came into existence when India
collided with the Asian continent. This collision is
still in progress; we are moving North-North-East about 5
cm a year, mostly going under China. (In the last million
years the distance covered would be more than 50
kilometres. The birthplaces of gods and early humans in
our land must have moved through a distance of this order
or more.
Sea fossils are found on top of high mountains, all over
the world, showing that nothing is permanent on long time
scales. The earth is continuously transforming. Large
oceans have mid-ocean ridges where matter comes out from
inside the earth as hot lava, sometimes making islands
that rise tall -- or not so tall -- above the sea
surface. This matter is transported along the ocean
bottom to edges of continents where it is subducted back
into the earth mantle. Such subduction zones lie along
the West Coast of North America and along the eastern
edge of Asia. There is continuous change.
What will happen in millions of years can only be
surmised. Dead matter of living things, does change the
morphology of the oceans. For example many coral islands
and reefs are nothing but accumulations of coral
skeletons growing on hills and mountains whose tops under
the sea come close to the sea surface for sunlight to
penetrate. Coral mountains cannot exist because coral
needs water and sunlight together. Though qualitatively
significant, this phenomenon also rides on the much
larger basic elements of the drama that keeps altering
the surface of the earth.
More at:
http://www.tribuneindia.com
Jai Maharaj
http://www.mantra.com/jai
Om Shanti
.
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| User: "Loopy" |
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| Title: Re: UNDERSTANDING THE UNIVERSE WITH PROF YASH PAL |
09 Aug 2004 10:51:39 PM |
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"> UNDERSTANDING THE UNIVERSE
WITH PROF YASH PAL
OK DO KA
.
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