Empathy List Archives

BT

Bent T

Mon, Nov 1, 2004 4:01 PM

Quote
Question (from "New Scientist")
In the novel Moby Dick, the wooden whaling ship meets a typhoon south-east
of Japan and is subjected to thunder, lightning and displays of St Elmo's
fire. Subsequently, the magnetism of the ship's compass needle is discovered
to be reversed. The author, Herman Melville, maintains that such compass
reversals "have in more than one case occurred to ships in violent storms",
and sometimes when the rigging has been struck by lightning the magnetism in
a compass needle may be totally lost. Is this fact or fiction, and if it is
true how does it occur?

Alan Sloan, Buxton, Derbyshire, UK

Answers
Herman Melville's assertion is entirely plausible. Lightning involves very
high currents with high associated magnetic fields. They remagnetise exposed
outcrops of high-coercivity (high resistance to the effect of an applied
magnetic field) rocks with ease. Currents exceeding 10,000 amperes have been
deduced from rock magnetisations. The associated magnetic fields could
easily demagnetise or reversely magnetise a compass needle.

Alan Reid, Leeds, UK
Unquote

Redundancy is always a good thing...

Cheers
Bent Tolstrup

Quote Question (from "New Scientist") In the novel Moby Dick, the wooden whaling ship meets a typhoon south-east of Japan and is subjected to thunder, lightning and displays of St Elmo's fire. Subsequently, the magnetism of the ship's compass needle is discovered to be reversed. The author, Herman Melville, maintains that such compass reversals "have in more than one case occurred to ships in violent storms", and sometimes when the rigging has been struck by lightning the magnetism in a compass needle may be totally lost. Is this fact or fiction, and if it is true how does it occur? Alan Sloan, Buxton, Derbyshire, UK Answers Herman Melville's assertion is entirely plausible. Lightning involves very high currents with high associated magnetic fields. They remagnetise exposed outcrops of high-coercivity (high resistance to the effect of an applied magnetic field) rocks with ease. Currents exceeding 10,000 amperes have been deduced from rock magnetisations. The associated magnetic fields could easily demagnetise or reversely magnetise a compass needle. Alan Reid, Leeds, UK Unquote Redundancy is always a good thing... Cheers Bent Tolstrup

JA

Jim Ague

Mon, Nov 1, 2004 4:23 PM

Assuming spherical earth, we all know that 1 minute of latitude is equal to
1 nautical mile.

At what latitude is 1 minute of LONGITUDE:

(easy one) equal to 1 nautical mile
(hard one) equal to 1 STATUTE mile

-- Jim

Jim & Rita Ague
M/V Derreen, Monk 36
at Waterside, Norfolk, VA

Assuming spherical earth, we all know that 1 minute of latitude is equal to 1 nautical mile. At what latitude is 1 minute of LONGITUDE: (easy one) equal to 1 nautical mile (hard one) equal to 1 STATUTE mile -- Jim ~~~~~~~~~~~~~~~~~~~~~~~~ Jim & Rita Ague M/V Derreen, Monk 36 at Waterside, Norfolk, VA ~~~~~~~~~~~~~~~~~~~~~~~~

MM

Mike Maurice

Mon, Nov 1, 2004 5:07 PM

ague@usa.net
At 11:23 AM 11/1/04 -0500, you wrote:

Assuming spherical earth, we all know that 1 minute of latitude is equal to
1 nautical mile.

At what latitude is 1 minute of LONGITUDE:

(easy one) equal to 1 nautical mile
(hard one) equal to 1 STATUTE mile

I don't have Bowditch in front of me.
At an absolute level of precision you can't assume a spherical earth. After
all it ain't so.

One minute of latitude equals one nautical mile. But the tricky part is how
many feet is that. It so happens that as the precision of our measurements
has improved the actual number has changed by a few feet, in some cases by
a few inches. As I recall the number of feet is calculated by the size of
the earth using the latitude and is directly related to the measurement as
it exists and is not necessarily static.
Whereas the statue mile is static.

Fortunately, the level of precision involved is not necessary for ordinary
mariners, or we would be in bi_G trouble.

The details for all this used to be, but may not be in the present version
of Bowditch.

Mike

Capt. Mike Maurice
Tualatin(Portland), Oregon

ague@usa.net At 11:23 AM 11/1/04 -0500, you wrote: >Assuming spherical earth, we all know that 1 minute of latitude is equal to >1 nautical mile. > >At what latitude is 1 minute of LONGITUDE: > > (easy one) equal to 1 nautical mile > (hard one) equal to 1 STATUTE mile I don't have Bowditch in front of me. At an absolute level of precision you can't assume a spherical earth. After all it ain't so. One minute of latitude equals one nautical mile. But the tricky part is how many feet is that. It so happens that as the precision of our measurements has improved the actual number has changed by a few feet, in some cases by a few inches. As I recall the number of feet is calculated by the size of the earth using the latitude and is directly related to the measurement as it exists and is not necessarily static. Whereas the statue mile is static. Fortunately, the level of precision involved is not necessary for ordinary mariners, or we would be in bi_G trouble. The details for all this used to be, but may not be in the present version of Bowditch. Mike Capt. Mike Maurice Tualatin(Portland), Oregon

JG

John Gaquin

Mon, Nov 1, 2004 5:15 PM

----- Original Message -----
From: "Jim Ague" jim.ague@att.net

Assuming spherical earth, we all know that 1 minute of latitude is equal

to

1 nautical mile.

At what latitude is 1 minute of LONGITUDE:

(easy one) equal to 1 nautical mile
(hard one) equal to 1 STATUTE mile

A -- Lat 0
B -- approx Lat 12

----- Original Message ----- From: "Jim Ague" <jim.ague@att.net> > Assuming spherical earth, we all know that 1 minute of latitude is equal to > 1 nautical mile. > > At what latitude is 1 minute of LONGITUDE: > > (easy one) equal to 1 nautical mile > (hard one) equal to 1 STATUTE mile A -- Lat 0 B -- approx Lat 12

PB

Peter Bennett

Tue, Nov 2, 2004 2:00 AM

Monday, November 1, 2004, 8:23:42 AM, Jim wrote:

JA> Assuming spherical earth, we all know that 1 minute of latitude is equal to
JA> 1 nautical mile.

JA> At what latitude is 1 minute of LONGITUDE:

JA> (easy one) equal to 1 nautical mile

at the equator

JA> (hard one) equal to 1 STATUTE mile

The length of a minute of longitude at any latitude is equal to the cosine of the latitude.

5280/6076 = 0.87 The angle whose cosine is 0.87 is 29.6.

--
Peter Bennett, VE7CEI Vancouver, B.C., Canada
Lien Hwa 28 (AKA Polaris 30) "Sea Spray"
GPS and NMEA info: http://vancouver-webpages.com/peter
Vancouver Power Squadron: http://vancouver.powersquadron.ca

Monday, November 1, 2004, 8:23:42 AM, Jim wrote: JA> Assuming spherical earth, we all know that 1 minute of latitude is equal to JA> 1 nautical mile. JA> At what latitude is 1 minute of LONGITUDE: JA> (easy one) equal to 1 nautical mile at the equator JA> (hard one) equal to 1 STATUTE mile The length of a minute of longitude at any latitude is equal to the cosine of the latitude. 5280/6076 = 0.87 The angle whose cosine is 0.87 is 29.6. -- Peter Bennett, VE7CEI Vancouver, B.C., Canada Lien Hwa 28 (AKA Polaris 30) "Sea Spray" GPS and NMEA info: http://vancouver-webpages.com/peter Vancouver Power Squadron: http://vancouver.powersquadron.ca

TM

Todd Mains

Tue, Nov 2, 2004 2:14 AM

I came up with the equator and approximately 30 degrees north and south
latitude.

Capatin Todd Mains
Portland, OR

-----Original Message-----
On Behalf Of Jim Ague
Sent: Monday, November 01, 2004 8:24 AM
To: Vianaut@tdc-broadband.dk; Trawler World List
Subject: T&T: RE: Which Way, Captain?

Assuming spherical earth, we all know that 1 minute of latitude is equal to
1 nautical mile.

At what latitude is 1 minute of LONGITUDE:

(easy one) equal to 1 nautical mile
(hard one) equal to 1 STATUTE mile

-- Jim

I came up with the equator and approximately 30 degrees north and south latitude. Capatin Todd Mains Portland, OR -----Original Message----- On Behalf Of Jim Ague Sent: Monday, November 01, 2004 8:24 AM To: Vianaut@tdc-broadband.dk; Trawler World List Subject: T&T: RE: Which Way, Captain? Assuming spherical earth, we all know that 1 minute of latitude is equal to 1 nautical mile. At what latitude is 1 minute of LONGITUDE: (easy one) equal to 1 nautical mile (hard one) equal to 1 STATUTE mile -- Jim

AW

Alan Wagner

Tue, Nov 2, 2004 4:06 AM

Is there a way to calculate how many BTUs of air conditioning you need for a
boat in Florida. I would suspect there is a web site calculator somewhere,
but I'll be darned if I can find it.

Alan
Tampa

Is there a way to calculate how many BTUs of air conditioning you need for a boat in Florida. I would suspect there is a web site calculator somewhere, but I'll be darned if I can find it. Alan Tampa

KT

Ken Tischler

Tue, Nov 2, 2004 4:12 AM

Flagship Marine has some good formulas here
http://flagshipmarine.com/sizeboat.html

Ken Tischler
Microship
Defever 49 PH

-----Original Message-----
From: trawlers-and-trawlering-bounces@lists.samurai.com
[mailto:trawlers-and-trawlering-bounces@lists.samurai.com] On Behalf Of Alan
Wagner
Sent: Monday, November 01, 2004 10:06 PM
To: trawlers-and-trawlering@lists.samurai.com
Subject: T&T: Air Conditioning

Is there a way to calculate how many BTUs of air conditioning you need for a
boat in Florida. I would suspect there is a web site calculator somewhere,
but I'll be darned if I can find it.

Alan
Tampa

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Flagship Marine has some good formulas here http://flagshipmarine.com/sizeboat.html Ken Tischler Microship Defever 49 PH -----Original Message----- From: trawlers-and-trawlering-bounces@lists.samurai.com [mailto:trawlers-and-trawlering-bounces@lists.samurai.com] On Behalf Of Alan Wagner Sent: Monday, November 01, 2004 10:06 PM To: trawlers-and-trawlering@lists.samurai.com Subject: T&T: Air Conditioning Is there a way to calculate how many BTUs of air conditioning you need for a boat in Florida. I would suspect there is a web site calculator somewhere, but I'll be darned if I can find it. Alan Tampa _______________________________________________ http://lists.samurai.com/mailman/listinfo/trawlers-and-trawlering To Unsubscribe send email to trawlers-and-trawlering-request@lists.samurai.com Include the word Unsubscribe (and nothing else) in the subject or body of the message.

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Which Way, Captain?