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Gravitational Pull continued
 t’s
the fact of putting together indirect clues," she said. "How
do we know black holes exist? They don’t even let off light."
Since
black holes are not directly observable, astronomers had to trace
the outburst of energy generated in the black holes to the density
of the holes and only then infer that such an entity existed – a
controversial notion when first introduced. Greene wrote her thesis
on stellar mass black holes.
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Jenny
Greene points to the moons of Jupiter on a photograph taken
from the Hubble telescope. PHOTO: Vikram Sura
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Although she enjoys the intricacies involved in pursuing astronomy,
Greene also seems to like thinking that far-away galaxies are ultimately
accessible. An atheist raised in a family of atheists, Greene shows
little curiosity about the unknowable.
Regarding
the existence of a master designer of the universe, she asked, "Something
I’m not really going to find out about?" Shrugging, she answered
her own question. "It doesn’t interest me."
But
Greene, who became curious about astronomy after a class she took
in 12th grade, is drawn to the skies by more than a purely
intellectual quest. "I like to look at the stars," she
said. "It’s fun to feel really, really small."
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A
space vehicle speeds at seven miles
per second to escape Earth's gravitational pull. The
speed is the same as going from New
York to Philadelphia in 20 seconds.
A
cosmic year is the amount of
time it takes the sun to revolve around the center of the
Milky Way - about 225 million
years.
Astronaut
Neil Armstrong first stepped on the moon with his left
foot.
Why
is the sky blue? Contrary to
popular belief, the phenomenon is not due to a reflection
of light from the oceans. The sky is blue because it scatters
the sun's blue light.
The
term "comet wine" is often used
for wines made in the year of an important comet passing.
For example, Portuguese wine bottled in 1811 is so dubbed
because it is believed to have been influenced by the Great
Comet of that year.
source:
www.space.com
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