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Blue whales out-rumble rockets, South Pole more dark than light, Galaxies collide in an expanding space
![[NOAA, NASA] The whale sounds louder](images/2003-03-07-whale-rocket.jpg) Q:
What’s the loudest animal on Earth?
[NOAA, NASA] The whale sounds louder
A: The loudest is the blue whale, which is also the
biggest animal that ever lived. We have measured the foghorn blasts of the blue
whale (and fin whales) at up to 188 decibels—louder than the 180-decibel noise
of a rocket launch.
Only males moan these enormous sounds, apparently searching the seas for a
mate. Other whales can hear the calls up to 1000 miles (1600 km) away. Low
frequency sound travels farther than high frequency and these frequencies are so
low (about 10 to 39 hertz) that humans can barely hear some and cannot hear the
lowest bellows at all.
Further Surfing:
League for the Hard of
Hearing: Noise levels
Guinness world
records: loudest animal
Q:
Last week you said the South Pole doesn’t experience exactly six months of
darkness. Why is that? —Lanney A., Sandia Park, New Mexico
A: The Earth's orbit is not a circle (though nearly) but rather an
ellipse. That orbital non-symmetry causes the illumination non-symmetry. The
orbital speed varies along the orbital path. The path distance between the
Earth's positions for the equinoxes varies also for winter and summer. Both
phenomena contribute to the non-symmetry.
Consider the Southern Hemisphere. During winter there, Earth moves slower and
has farther to go between the equinoxes than during the summer. So, winter is
slightly longer than summer.
"Very small differences but they do make a difference," says Don Neff,
physicist at NOAA’s Climate Monitoring & Diagnostics Laboratory (CMDL), who
spent three years at their South Pole facility.
Further Surfing
WonderQuest: South Pole light
Q: The recent Hubble
photo of the Tadpole Galaxy was explained as two galaxies colliding. Doesn't
this contradict the Big Bang Theory of universe expanding? —Mar
Q: The latest pictures from
the Hubble Telescope are remarkable. But if the universe is expanding, then
everything should be getting farther away from each other. How then, can two
galaxies collide? — John
Q: Constellations remain the same yet scientists
declare that the universe expansion is accelerating...how can this be?
—Margaret F.![A colliding galaxy, dubbed “Tadpole”, located 420 million light-years away. [NASA, H. Ford (JHU), G. Illingworth (USCS/LO), M. Clampin (STScI), G. Hartig (STScI), and the ACS Science Team]](images/tadpole.jpg)
A colliding galaxy, dubbed “Tadpole”, located 420 million
light-years away. [NASA, H. Ford (JHU), G. Illingworth (USCS/LO), M. Clampin (STScI),
G. Hartig (STScI), and the ACS Science Team]
A: Good questions all. The answer is simple. Space— as a whole—is
expanding but nearby objects and space near objects do not expand.
You do not fly apart. The Sun does not move away from Earth. Constellations
and galaxies do not expand.
Gravity and electromagnetic forces hold local objects together.
Consider an extremely local object: your body. Chemical bonds between
molecules hold it together. The bonds are basically due to electromagnetic
forces and those forces are extraordinarily strong: stronger than gravity and
much stronger than the expansion of the Universe for small objects.
Gravity can overcome space expansion for nearby objects, like galaxies. "The
overall expansion is very weak and the attractive force of gravity between two
galaxies (or, indeed, even clusters of galaxies) is much stronger than the
expansion," says Brian Chaboyer, astrophysicist at Dartmouth University.
Gravity prevents expansion of close objects. Expansion wins out over gravity
only on the very largest scales. That’s where expansion takes place—out tens of
billions of light years away, where the glow of distant galaxies is like clotted
dust.
Further Surfing:
Brian
Chaboyer, Dartmouth U: "Dark energy" dominates the Universe
Hubble/NASA: Video of camera move on Tadpole
WonderQuest:
Expanding Universe
(Answered Mar. 7, 2003)
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