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Surgery Using A Sunlight Scalpel
Makarand writes "Research conducted by Israeli doctors has shown that it is possible to use
concentrated sunlight instead
of lasers to perform surgery, providing a safe and
low cost alternative to laser treatment.
In their experiments sunlight was transported into the operating room
from outside using a system of optical fibers.
The concentrated rays - containing several watts
of energy - were then used in the experimental surgery conducted
on rats." Here is Wired's similar story.
AFAIK, winter = cold season.
Wrong. Winter is defined as (from dictionary.com)
"The usually coldest season of the year, occurring between autumn and spring, extending in the Northern Hemisphere from the winter solstice to the vernal equinox, and popularly considered to be constituted by December, January, and February. "
Generally, its understood that winter (in the northern hemisphere at least) is the time when the earth tilts on its axis and the northern hemisphere is furtherst from the sun.
Cruising the internet on my TI-99/4A @ a whopping 300 baud!
Nope.
r s/980221a.html:
From http://imagine.gsfc.nasa.gov/docs/ask_astro/answe
"
I have heard two conflicting reasons explaining why winter is cooler.
(1) Because of the slight pivot of Earth's on its axis, the sun is farther away during winter because part of the planet is pointing away from the sun, hence, less energy reaches that surface.
(2) The sun is actually CLOSER to the surface during winter but light hits the planet at an obtuse angle which "skims" the surface. Direct rays are not hitting the surface which brings about cooler temperatures.
Which explanation is correct?
The Answer
The second. Winter is colder because the earth's axis is tilted. Winter occurs for the hemisphere which is tilted away from the sun (the northern hemisphere in January, the southern in July). This has two main effects on the winter hemisphere. First, the sun is above the horizon for fewer hours each day, so that hemisphere receives less heat from the sun. Also, sunlight strikes the ground at a shallower angle so that less energy per unit area is intercepted by the winter hemisphere. It is true that the earth is closest to the sun in January. However, the distance from the earth to the sun varies by only about 2% over a year. This causes a change of only 4% in the amount of solar radiation hitting the earth so this effect is not significant compared to the other two.
"
Emphasis mine.
Cruising the internet on my TI-99/4A @ a whopping 300 baud!
How did this make it past the Slashdot editors, especially in the science section of Slashdot? Watts are units of power. Joules are units of energy. The phrase "several watts of energy" does not make any sense.