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Chat Area => General Discussion Area => Topic started by: Field Marshal Dr. Opti on 21 December 2012, 13:05:02

Title: Shortest day?
Post by: Field Marshal Dr. Opti on 21 December 2012, 13:05:02
Is it the shortest day today?

Title: Re: Shortest day?
Post by: Taxi_Driver on 21 December 2012, 13:08:20
Yes....it would have been even shorter if the world had exploded  ::) ::) ;D
Title: Re: Shortest day?
Post by: Lizzie_Zoom on 21 December 2012, 13:25:29
Yes....it would have been even shorter if the world had exploded  ::) ::) ;D

Which of course it has not! ;D ;D ;D ;D ;D ;D  Surprise, surprise!! :P :P
Title: Re: Shortest day?
Post by: Entwood on 21 December 2012, 13:29:12
Days now getting longer ...

Quote
the exact time of the solstice this year - when the Earth's axial tilt is farthest away from the sun - is at 11:11 GMT

:)
Title: Re: Shortest day?
Post by: Field Marshal Dr. Opti on 21 December 2012, 13:38:24
Days now getting longer ...

Quote
the exact time of the solstice this year - when the Earth's axial tilt is farthest away from the sun - is at 11:11 GMT

:)


The Earth moves pretty quickly for an elderly dowager. I'd have to look it up, but I believe the old girl spins at about 1,000 MPH. ;D
Title: Re: Shortest day?
Post by: Entwood on 21 December 2012, 13:50:24
Days now getting longer ...

Quote
the exact time of the solstice this year - when the Earth's axial tilt is farthest away from the sun - is at 11:11 GMT

:)

The Earth moves pretty quickly for an elderly dowager. I'd have to look it up, but I believe the old girl spins at about 1,000 MPH. ;D

correctomundo  :) (except you don't "spin" in mph .. but in revolutions per time :)  )

mean diameter of earth = 12756.2 km = 7926.34 miles

mean circumference of earth at equator = 3.14159 x 7926.34 = 24901.31 miles

earth completes one revolution in 24 hours, so any point on the earths surface is moving at approximately 1037.5545 mph
Title: Re: Shortest day?
Post by: Auto Addict on 21 December 2012, 14:02:53
Days now getting longer ...

Quote
the exact time of the solstice this year - when the Earth's axial tilt is farthest away from the sun - is at 11:11 GMT

:)

The Earth moves pretty quickly for an elderly dowager. I'd have to look it up, but I believe the old girl spins at about 1,000 MPH. ;D

correctomundo  :) (except you don't "spin" in mph .. but in revolutions per time :)  )

mean diameter of earth = 12756.2 km = 7926.34 miles

mean circumference of earth at equator = 3.14159 x 7926.34 = 24901.31 miles

earth completes one revolution in 24 hours, so any point on the earths surface is moving at approximately 1037.5545 mph

Is that why I keep falling over :o
Title: Re: Shortest day?
Post by: Kevin Wood on 21 December 2012, 14:26:58
Is that why I keep falling over :o

www.acmezimmerframes.co.uk   :y

 ;)

Title: Re: Shortest day?
Post by: Abiton on 21 December 2012, 14:40:31
Shouldn't that be "any point on the earth's surface on the equator is moving at 1037.5545mph"?
Title: Re: Shortest day?
Post by: cem_devecioglu on 21 December 2012, 14:54:46
ok.. question is why airplanes dont stay in same point and travel free to another distance ;D
 
or wait until earth turns enough and land in there ;D :P
 
Title: Re: Shortest day?
Post by: Entwood on 21 December 2012, 15:50:53
ok.. question is why airplanes dont stay in same point and travel free to another distance ;D
 
or wait until earth turns enough and land in there ;D :P

Simple .. the air is also moving at over 1000 mph .... relative to a stationary spot in space .. but relative to the surface to the earth it is not ....  one could argue that a "spot" on the earth is actually moving at a far greater speed .. relative to the sun, as the earths orbit around the sun needs to be included ... but then again .. relative to another planetary system the movement of the Sun needs to be considered .. and then again .... relative to another galaxy the movement of the "milky way"  and then again ....... etc etc etc ....

Everything discussed under the term "motion" is always "relative" to the position of the point of measure .. :)
Title: Re: Shortest day?
Post by: Entwood on 21 December 2012, 15:51:13
Shouldn't that be "any point on the earth's surface on the equator is moving at 1037.5545mph"?

correctomundo :) a point at the planetary pole is rotating without any relative movement .. it could be considered stationary ..... but it is moving ....  depending on your point of view ..  ;D ;D ;D ;D
Title: Re: Shortest day?
Post by: Kevin Wood on 21 December 2012, 15:58:39
Shouldn't that be "any point on the earth's surface on the equator is moving at 1037.5545mph"?

correctomundo :) a point at the planetary pole is rotating without any relative movement .. it could be considered stationary ..... but it is moving ....  depending on your point of view ..  ;D ;D ;D ;D

It's still rotating around the sun at quite a few leptons, though. .. and is the solar system still, or blatting through the universe? My head hurts.
Title: Re: Shortest day?
Post by: Entwood on 21 December 2012, 15:59:56
Shouldn't that be "any point on the earth's surface on the equator is moving at 1037.5545mph"?

correctomundo :) a point at the planetary pole is rotating without any relative movement .. it could be considered stationary ..... but it is moving ....  depending on your point of view ..  ;D ;D ;D ;D

It's still rotating around the sun at quite a few leptons, though. .. and is the solar system still, or blatting through the universe? My head hurts.

Agreed   see post #10   :)
Title: Re: Shortest day?
Post by: Lizzie_Zoom on 21 December 2012, 16:33:13
Shouldn't that be "any point on the earth's surface on the equator is moving at 1037.5545mph"?

correctomundo :) a point at the planetary pole is rotating without any relative movement .. it could be considered stationary ..... but it is moving ....  depending on your point of view ..  ;D ;D ;D ;D

It's still rotating around the sun at quite a few leptons, though. .. and is the solar system still, or blatting through the universe? My head hurts.

Agreed   see post #10   :)

Now all this has got me thinking (all too much really! :o :o ;D), but how do satellites keep stationery above a point on the Earth's surface and keep propelled to the speed of the Earth.  For once I cannot get my head around that thought to come up with an answer!  Anyone?? ??? ??? ???
Title: Re: Shortest day?
Post by: Entwood on 21 December 2012, 16:41:46
Lizzie  ... they are NOT stationary ...  they are geo-stationary ... stationary RELATIVE to the earths surface ... actually moving at quite a high speed given their height above the surface. There is virtually no "drag" so once accelerated to speed they hold that speed for a very long time ... and it needs to be high to overcome gravity which is trying to pull each satellite back down .... so....

centrifugal force (the force created by the movement of the satellite "trying" to go in a straight line - Newtons laws of motion)) is [hopefully] equal to the centripetal force generated by gravity trying to pull it down ...... so it stays up and in one place ... a very difficult balancing act ... it is easier to keep the satellite moving in an orbit which is why navigation satellites, for example, move all the time.

Geo-stationary satellites usually have a small amount of fuel in reserve to keep repositioning themselves ... when they run out of fuel and slow down too much they are doomed to eventualy reenter and burn up...... just takes a long while to happen .. :)

HTH
Title: Re: Shortest day?
Post by: Lizzie_Zoom on 21 December 2012, 16:45:01
Lizzie  ... they are NOT stationary ...  they are geo-stationary ... stationary RELATIVE to the earths surface ... actually moving at quite a high speed given their height above the surface. There is virtually no "drag" so once accelerated to speed they hold that speed for a very long time ... and it needs to be high to overcome gravity which is trying to pull each satellite back down .... so....

centrifugal force (the force created by the movement of the satellite "trying" to go in a straight line - Newtons laws of motion)) is [hopefully] equal to the centripetal force generated by gravity trying to pull it down ...... so it stays up and in one place ... a very difficult balancing act ... it is easier to keep the satellite moving in an orbit which is why navigation satellites, for example, move all the time.

Geo-stationary satellites usually have a small amount of fuel in reserve to keep repositioning themselves ... when they run out of fuel and slow down to much they are doomed to eventualy reenter and burn up...... just takes along while to happen .. :)

HTH

Thanks for that Entwood! 8) 8)  I now understand :y :y
Title: Re: Shortest day?
Post by: Field Marshal Dr. Opti on 21 December 2012, 17:22:21
Shouldn't that be "any point on the earth's surface on the equator is moving at 1037.5545mph"?

correctomundo :) a point at the planetary pole is rotating without any relative movement .. it could be considered stationary ..... but it is moving ....  depending on your point of view ..  ;D ;D ;D ;D

It's still rotating around the sun at quite a few leptons, though. .. and is the solar system still, or blatting through the universe? My head hurts.



Best figure I can come up with is about 68,000 MPH. The Earth clearly has a formidable "power to weight" ratio.  ;)
Title: Re: Shortest day?
Post by: Nick W on 21 December 2012, 19:03:48
Going back to the original post, although it might be the shortest day a combination of dopey customers, idiot controllers and crap jobs is making it feel like the longest!