Oh my! Things don't look good in SE Asia.

  • Thread starter Thread starter keith
  • Start date Start date
keith said:
I find this sort of reporting amazing (not really, considering the hoopla
over "global warming"). Was there a significant change in the COG? Was
there matter ejected from the Earth that would change the net energy of
the (rest of the) Earth? What net energy was imparted to the orbit that
caused the change? Where did said energy come from?

I've heard that the day's lenghth changed by perhaps three microseconds
(which has nothing to do with the orbit). Even that's not a huge
deal wstatthey're adding leap seconds every few years.
Click to expand...

Well, I guess they meant changed the Earth's rotation rather than its orbit.

Yousuf Khan
 
keith said:
I find this sort of reporting amazing (not really, considering the hoopla
over "global warming"). Was there a significant change in the COG? Was
there matter ejected from the Earth that would change the net energy of
the (rest of the) Earth? What net energy was imparted to the orbit that
caused the change? Where did said energy come from?
Click to expand...

Keith, consider an ice skater. When entering a spin, the arms are
outstretched and the spin is slow. When the arms are pulled in, the
spin rate increases dramatically. This is due to conservation of
angular momentum.

Rock is a lot heavier than water. If you cut off Mt. Everest at the
base and drop it into the Mindinao Trench, the spin rate of the earth
will increase significantly because more of the mass of the Earth
moves toward its center. This, in effect, is what happened a couple
of days ago: one tectonic plate dove under another, causing the whole
tectonic plate near the junction to drop (thus causing the tidal
wave). So the earth's spin rate increases.

The orbital effect was much smaller, but yes, the COG did change
[evidently significantly enough to measure]. As you indicate, the
earth-system's [including the mass of the moon] COG follows a highly
stable elliptical orbit around the sun. Cut off Everest and drop it
in the Trench and the COG does change - and that (slightly) changes
the orbit.

Keith, next time send me my Xmas gift a few days earlier? ;-)

Felger Carbon
who remembers when there weren't any tectonic plates
 
The little lost angel said:
I don't think any one of us want to see a 10. This 9 has killed people
as far away as India and Somalia. A 10 would have total disregard for
distance I think. :(
Click to expand...

IIRC, a 10 has ten times the energy of a 9. If the energy dissipates
equally in all directions through rock (half of a ball; no energy
dissipation into the air) then the effect a 9 has at 100 miles would
be felt for a 10 at about 350 miles. Sorry, you're wrong.

On the other hand, you're entitled to be shook up a little bit. ;-)
 
Felger Carbon said:
Rock is a lot heavier than water. If you cut off Mt. Everest at the
base and drop it into the Mindinao Trench, the spin rate of the earth
will increase significantly because more of the mass of the Earth
moves toward its center. This, in effect, is what happened a couple
of days ago: one tectonic plate dove under another, causing the whole
tectonic plate near the junction to drop (thus causing the tidal
wave). So the earth's spin rate increases.
Click to expand...

But doesn't the rock "sliding under" push the rock above it up some,
resulting in a net change of zero (at least potentially)?

As for Mt. Everest, yes, it's "large", but my understanding is that
the Earth is in fact smoother than a billiards ball.
 
chrisv said:
But doesn't the rock "sliding under" push the rock above it up some,
resulting in a net change of zero (at least potentially)?
Click to expand...

The operative word is "some", Chris. ;-)
As for Mt. Everest, yes, it's "large", but my understanding is that
the Earth is in fact smoother than a billiards ball.
Click to expand...

Never measured the smoothness of a billiard ball, so I can't comment
on that. Sigh. There goes my rep for omiscience! ;-) ;-)

Hey, the speedup in the Earth's 24-hr rotational rate was a very few
microseconds.
 
IIRC, a 10 has ten times the energy of a 9. If the energy dissipates
equally in all directions through rock (half of a ball; no energy
dissipation into the air) then the effect a 9 has at 100 miles would
be felt for a 10 at about 350 miles. Sorry, you're wrong.
Click to expand...

Except AIUI, the earthquake shock wave travels through the surface
(crust), so dissipates as the inverse square so a 9 at 100 miles would
be close to a 10 at 1000Mi. so...
On the other hand, you're entitled to be shook up a little bit. ;-)
Click to expand...

As long as it's shaken and not stirred.
 
Keith, consider an ice skater. When entering a spin, the arms are
outstretched and the spin is slow. When the arms are pulled in, the
spin rate increases dramatically. This is due to conservation of
angular momentum.
Click to expand...

Ok, but the ice skater is still orbiting around the sun at the same
rate. ...and rotating around the earth at the same rate.
Rock is a lot heavier than water. If you cut off Mt. Everest at the
base and drop it into the Mindinao Trench, the spin rate of the earth
will increase significantly because more of the mass of the Earth
moves toward its center. This, in effect, is what happened a couple
of days ago: one tectonic plate dove under another, causing the whole
tectonic plate near the junction to drop (thus causing the tidal
wave). So the earth's spin rate increases.
Click to expand...

....but not it's orbit. As I said, I'm told that the day changed by
three microseconds, but the year?
The orbital effect was much smaller, but yes, the COG did change
[evidently significantly enough to measure]. As you indicate, the
earth-system's [including the mass of the moon] COG follows a highly
stable elliptical orbit around the sun. Cut off Everest and drop it
in the Trench and the COG does change - and that (slightly) changes
the orbit.
Click to expand...

The COG of the E-M system is still in the same orbit around the sun,
even if the COG shifted relative to the earth's center, so no, I don't
buy what you're selling. ;-)
Keith, next time send me my Xmas gift a few days earlier? ;-)
Click to expand...

You mean it hasn't gotten there yet? How about last years? ;-)
Felger Carbon
who remembers when there weren't any tectonic plates
Click to expand...

You *are* old. ;-) We learned about them in first grade along with the
strange "coincidence" that the Africa coastline looks strangely like it
would fit into S. America.
 
Keith R. Williams said:
The orbital effect was much smaller, but yes, the COG did change
[evidently significantly enough to measure]. As you indicate, the
earth-system's [including the mass of the moon] COG follows a highly
stable elliptical orbit around the sun. Cut off Everest and drop it
in the Trench and the COG does change - and that (slightly) changes
the orbit.
Click to expand...

The COG of the E-M system is still in the same orbit around the sun,
even if the COG shifted relative to the earth's center, so no, I don't
buy what you're selling. ;-)
Click to expand...

Keith, the COG wuz following (by definition) a certain orbit. If the
COG suddenly changes (even by a tenth of an inch), the orbit has
suddenly changed.
 
Keith R. Williams said:
The orbital effect was much smaller, but yes, the COG did change
[evidently significantly enough to measure]. As you indicate, the
earth-system's [including the mass of the moon] COG follows a highly
stable elliptical orbit around the sun. Cut off Everest and drop it
in the Trench and the COG does change - and that (slightly) changes
the orbit.
Click to expand...

The COG of the E-M system is still in the same orbit around the sun,
even if the COG shifted relative to the earth's center, so no, I don't
buy what you're selling. ;-)
Click to expand...

Keith, the COG wuz following (by definition) a certain orbit. If the
COG suddenly changes (even by a tenth of an inch), the orbit has
suddenly changed.
Click to expand...

Nope. The COG is still in the same orbit. The COG may have shifted
location, but it is still in the *same* orbit since no energy has been
added/subtracted from the system. The year is still the same length as
long as the COG doesn't change (and that won't change without energy
being added/subtracted from the system).
 
chrisv said:
But doesn't the rock "sliding under" push the rock above it up some,
resulting in a net change of zero (at least potentially)?
Click to expand...

It's actually this rock that's pushed up that's causing the change in
momentum. The rock that's pushed up is a massive amount of rock (like
the island of Sumatra) and it adds some additional momentum from being
pushed out that slight bit. Even if it's only been thrown out by a
couple of metres it's still farther enough out that it slowed the
Earth's spin rate by a few microseconds.

Yousuf Khan
 
Yousuf Khan said:
It's actually this rock that's pushed up that's causing the change in
momentum. The rock that's pushed up is a massive amount of rock (like
the island of Sumatra) and it adds some additional momentum from being
pushed out that slight bit. Even if it's only been thrown out by a
couple of metres it's still farther enough out that it slowed the
Earth's spin rate by a few microseconds.
Click to expand...

The claim being objected to wasn't that it changed the spin (which is
quite reasonable), but that it changed the orbit.
 
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