Original source :http://2spare.com
Posted : March 2006
Author : the admin
1. Water IS blue, not
just because of the sky
Many believe that lakes and oceans are blue "only"
because they reflect the blue sky. Actually water looks blue because water is
blue; the water molecules do absorb some light, and they absorb red frequencies
more than blue. The effect is small, so the blue color only becomes obvious
when observing layers of water many meters (or more) thick. (This effect is
noticeable to a lesser amount in white-painted swimming pools.) In salt water
or mineral-laden fresh water, the color of dissolved minerals can also be seen.
Sky-reflection does play a role, but only when the water surface is very calm,
and only when the water is observed at a glancing angle less than approximately
ten degrees.
2. Electricity does
NOT travel at the speed of light
Many textbooks claim that Electricity (electrons) within
wires flows at nearly (or even exactly at) the speed of light. In fact it's the
electrical energy which flows rapidly ("rapidly" is still slower than
the speed of light). Electrons, which have mass, can never travel at the speed
of light due to the theory of relativity. The drift velocity of the charges in
an electric current is extremely slow, on the order of centimetres per hour.
Where the electric current is visible, as in electrophoresis, the slow movement
of charge carriers can be seen directly.
As a very rough analogy, imagine a line of people at an amusement park. When
the people at the front board the ride, a space opens up, and rapidly spreads
to the back of the line. However, the average velocity of any one person is far
slower than the speed at which the space moves.
3. Seasons are NOT
the same length
Due to the earth moving fastest in its orbit when closest to
the Sun, the southern summer / northern winter is the shortest season, with
northern summer / southern winter being the longest. However, the difference on
earth is only a matter of a few days, while on Mars with its more eccentric
orbit the difference is more distinct.
4. You WON'T get a cold
just from low temperature
It is a very widespread misconception that the common cold
can be caused by (or the chance of getting infected by it is increased by)
exposure to cold weather. In reality, the common cold is caused by viruses and
has nothing to do with low temperatures.
5. Saturn is NOT the
only planet with rings
Jupiter, Uranus, and Neptune also have rings, though those
of Saturn are the most visually striking (and the only ones easily seen).
6. Meteors are NOT
hot when they land on Earth
When a meteor lands on Earth, it usually is not hot. It's
usually warm. A meteor's great speed is enough to melt its outside layer, but
any molten material will be quickly blown off (ablated), and the interior of
the meteor doesn't have time to heat up because rocks are poor conductors of
heat. Also, atmospheric drag can slow small meteors to terminal velocity by the
time they hit the ground, giving them some time to cool down.
7. Clouds do NOT form
because of the air's temperature
It is incorrectly believed that clouds form because cold air
"holds" less water vapor than warm air. Air has no capacity to hold
water vapor. It is the temperature of the water itself (and its surroundings)
that causes humidity, condensation and clouds to form.
8. People DID know earth
was not flat before Columbus
Some believe that Christopher Columbus had a hard time
receiving support because Europeans believed in a flat Earth. In fact, sailors
and navigators of the time knew that the Earth was spherical, but (correctly)
disagreed with Columbus's estimates of the
distance to the Indies. If the Americas did not exist, and Columbus
had continued to the Indies (even putting
aside the threat of mutiny he was under) he would not have survived long enough
to reach them.
9. The Great Wall of China is NOT particularly visible from
space
While at a low orbit, the Great Wall of
China can certainly be seen from space but it is not unique in
that regard. From a low orbit of the earth, many artificial objects are visible
on the earth, not just the Great Wall of China.
Highways, ships in the sea, dams, railroads, cities, fields of crops, and even
some individual buildings.
As to the claim that it's the only man-made object visible from the moon,
Apollo astronauts have reported that they could not see any man-made object
from the moon, not even the Great Wall.
10. There is NO "dark
side" of the Moon
The Moon is in synchronous orbit - this means, it takes exactly
the same time to rotate once around its axis than it does to make one orbit
around the Earth - so it has a far side, because it always keeps the same
hemisphere pointed towards Earth. When the Moon is roughly between the Sun and
Earth, it is daytime for the "far side" and night time for the
"near side". When the Moon gets "behind" the Earth, it is
night time for the "far side" and daytime for the "near
side".
~Blog Admin~
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