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Full phase Earth from the lunar surface?



 
 
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  #1  
Old May 19th 14, 11:28 AM posted to sci.space.policy,sci.astro,sci.physics,rec.arts.sf.science
Robert Clark[_4_]
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Posts: 85
Default Full phase Earth from the lunar surface?

The full Moon sometimes looks huge when it's low on the horizon. I was
wondering if the same effect would occur on the Moon if we saw a full phase
Earth from the lunar surface.
There haven't been many pictures taken from the surface of the Moon that
show the Earth. Here's one:

http://moonpans.com/prints/CernanEarth.jpg

The Earth can look pretty large low on the horizon from lunar orbit even
when not at full phase as shown by this Apollo 11 image taken from orbit:

http://www.astronautix.com/graphics/0/10075247.jpg

Are there images taken from the lunar surface either by robots or manned
missions that show the Earth rise at or close to full phase?

Nice article by Dr. Pauls Spudis:

Earth Rising.
Earth as seen from the Moon is always in the same place – true or false? It
depends.
By Paul D. Spudis
May 15, 2014
Quote:
Thus, there are places on the Moon from which we can stand and
contemplate the sheer beauty and magnificence of a slowly rising Earth.
Given the sea change in global perspective provided by the famous Earthrise
picture taken by the Apollo 8 crew almost fifty years ago, what societal
impacts will occur when a human being stands on the lunar surface and
watches the Earth slowly rise above the horizon? I suspect that a similar
shift in planetary perspective will occur. If history is any guide, such a
shift will have profound psychological and political implications – both
positive and negative – in our reach for the stars.
http://www.airspacemag.com/daily-pla...#ixzz321FRfV82

I wonder if a Google Lunar X-Prize entrant could land at one of the
locations where Earthrise would be visible.


Bob Clark

  #2  
Old May 19th 14, 11:38 AM posted to sci.space.policy,sci.astro,sci.physics,rec.arts.sf.science
R Kym Horsell[_2_]
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Posts: 111
Default Full phase Earth from the lunar surface?

In sci.physics Robert Clark wrote:
The full Moon sometimes looks huge when it's low on the horizon. I was
wondering if the same effect would occur on the Moon if we saw a full phase
Earth from the lunar surface.


The effect might even be larger. Sitting out in the middle of the sky objects
generally have no references we can judge their size by. Closer to
the horizon they seem larger because we then have landmarks and even
the curvature of the horizon to compare their angular size with.

On the Moon, while there may be landmarks, they may be unfamiliar enough
our visual wiring won't react normally to. But they may still cue off
the curvature of the horizon.

Might be a cute set of experiments to try with bits of colored card
and some willing volunteers. Could be a jr science prize winner if
you have kids allergic to volcanic dust.

There haven't been many pictures taken from the surface of the Moon that
show the Earth. Here's one:
http://moonpans.com/prints/CernanEarth.jpg
The Earth can look pretty large low on the horizon from lunar orbit even
when not at full phase as shown by this Apollo 11 image taken from orbit:
http://www.astronautix.com/graphics/0/10075247.jpg
Are there images taken from the lunar surface either by robots or manned
missions that show the Earth rise at or close to full phase?
Nice article by Dr. Pauls Spudis:
Earth Rising.
Earth as seen from the Moon is always in the same place ? true or false? It
depends.
By Paul D. Spudis
May 15, 2014
Quote:
Thus, there are places on the Moon from which we can stand and
contemplate the sheer beauty and magnificence of a slowly rising Earth.
Given the sea change in global perspective provided by the famous Earthrise
picture taken by the Apollo 8 crew almost fifty years ago, what societal
impacts will occur when a human being stands on the lunar surface and
watches the Earth slowly rise above the horizon? I suspect that a similar
shift in planetary perspective will occur. If history is any guide, such a
shift will have profound psychological and political implications ? both
positive and negative ? in our reach for the stars.
http://www.airspacemag.com/daily-pla...#ixzz321FRfV82
I wonder if a Google Lunar X-Prize entrant could land at one of the
locations where Earthrise would be visible.
Bob Clark


--
[Paul's week-long multi-thread "need for atmosphere to be a black body":]

The subject is "Why do they so much need the atmosphere to be a black body"
-- Paul Aubrin, 16 May 2014

But Paul, black body radiation IS thermal radiation. Try to stay on topic.
-- Tom P, 17 May 2014

Microwave sounding doesn't require the atmosphere to be a black body.
-- PA, 16 May 2014

Well in that case, what are you arguing about? You really are a complete
time-waster.
-- Tom, 17 May 2014
  #3  
Old May 19th 14, 04:14 PM posted to sci.space.policy,sci.astro,sci.physics,rec.arts.sf.science
Sam Wormley[_2_]
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Posts: 3,966
Default Full phase Earth from the lunar surface?

On 5/19/14, 5:28 AM, Robert Clark wrote:
The full Moon sometimes looks huge when it's low on the horizon. I was
wondering if the same effect would occur on the Moon if we saw a full
phase Earth from the lunar surface.
There haven't been many pictures taken from the surface of the Moon that
show the Earth. Here's one:

http://moonpans.com/prints/CernanEarth.jpg

The Earth can look pretty large low on the horizon from lunar orbit even
when not at full phase as shown by this Apollo 11 image taken from orbit:

http://www.astronautix.com/graphics/0/10075247.jpg

Are there images taken from the lunar surface either by robots or manned
missions that show the Earth rise at or close to full phase?

Nice article by Dr. Pauls Spudis:

Earth Rising.
Earth as seen from the Moon is always in the same place – true or false?
It depends.
By Paul D. Spudis
May 15, 2014
Quote:
Thus, there are places on the Moon from which we can stand and
contemplate the sheer beauty and magnificence of a slowly rising Earth.
Given the sea change in global perspective provided by the famous
Earthrise picture taken by the Apollo 8 crew almost fifty years ago,
what societal impacts will occur when a human being stands on the lunar
surface and watches the Earth slowly rise above the horizon? I suspect
that a similar shift in planetary perspective will occur. If history is
any guide, such a shift will have profound psychological and political
implications – both positive and negative – in our reach for the stars.
http://www.airspacemag.com/daily-pla...#ixzz321FRfV82


I wonder if a Google Lunar X-Prize entrant could land at one of the
locations where Earthrise would be visible.


Bob Clark


  #4  
Old May 19th 14, 04:23 PM posted to sci.physics,sci.astro
Sam Wormley[_2_]
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Posts: 3,966
Default Full phase Earth from the lunar surface?

On 5/19/14, 5:28 AM, Robert Clark wrote:
The full Moon sometimes looks huge when it's low on the horizon. I was
wondering if the same effect would occur on the Moon if we saw a full
phase Earth from the lunar surface.



Homework problem I give my freshman astronomy students: What is the
angular diameter of the Earth (in either degrees or arc minutes) as
seen from the Moon?



  #5  
Old May 19th 14, 10:32 PM posted to sci.space.policy,sci.astro,sci.physics,rec.arts.sf.science
Michael Moroney
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Posts: 124
Default Full phase Earth from the lunar surface?

"Robert Clark" writes:

[quote]Thus, there are places on the Moon from which we can stand and
contemplate the sheer beauty and magnificence of a slowly rising Earth.


The Earth, as seen from the moon will appear fixed in the sky as the moon
is tidally locked with the earth. The earth will move wrt the background
stars, will have phases, but other than "wobble" from a noncircular orbit,
remains fixed in the sky and cannot rise.

I suppose at the "edge" of the moon (as seen from Earth, longitudes +/-90
degrees) you may see the earth on the horizon repeatedly rise and set due
to this wobble, but that's it. The Apollo "earthrise" was due to the
motion of the spacecraft.

  #6  
Old May 19th 14, 11:19 PM posted to sci.astro
dlzc
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Posts: 1,426
Default Full phase Earth from the lunar surface?

Dear Robert Clark:

On Monday, May 19, 2014 3:28:58 AM UTC-7, Robert Clark wrote:

The full Moon sometimes looks huge when it's
low on the horizon. I was wondering if the
same effect would occur on the Moon if we saw
a full phase Earth from the lunar surface.


Well no, since the Moon is tidally locked to the Earth. The Earth always looks the same size, whereever you are. Now from orbit around the Moon, sure.

David A. Smith
  #7  
Old May 19th 14, 11:21 PM posted to sci.space.policy,sci.astro,sci.physics,rec.arts.sf.science
R Kym Horsell[_2_]
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Posts: 111
Default Full phase Earth from the lunar surface?

In sci.physics Michael Moroney wrote:
"Robert Clark" writes:
[quote]Thus, there are places on the Moon from which we can stand and
contemplate the sheer beauty and magnificence of a slowly rising Earth.

The Earth, as seen from the moon will appear fixed in the sky as the moon
is tidally locked with the earth. The earth will move wrt the background
stars, will have phases, but other than "wobble" from a noncircular orbit,
remains fixed in the sky and cannot rise.
I suppose at the "edge" of the moon (as seen from Earth, longitudes +/-90
degrees) you may see the earth on the horizon repeatedly rise and set due
to this wobble, but that's it. The Apollo "earthrise" was due to the
motion of the spacecraft.



The moon libates which causes the earth to move in
Lissajous figures in a region 15x13 deg -- i.e.
20 or 30 times the apparent size of the moon as
seen from earth and about 5 or 6 times the apparent
size of the earth as seen from the moon.


But, yes, walking around the edge of the moon would be
a faster way to see an earthrise on the surface.

--
The most likely culprit [for the dieback of Azorella on Macquarie
Island] would seem is climate change. Having evolved in an environment
with a remarkably consistent climate -- albeit consistently cold and
wet -- on a tiny speck of land within the latitudes of the furious
fifties, Azorella looks to be well suited for constant drizzle and
howling westerly winds. This climate has become less consistent over
the last 30 to 40 years, heavy rain is more common; periods of several
days with no drizzle at all are more common; wind may be getting
stronger; and sunny days possibly more common. Maybe a threshold has
been crossed and Azorella is no longer superbly adapted to its
environment because the environment in which it has evolved over
thousands of years has changed.
-- ABC, "Walking the climate tightrope on Macquarie Island", 19 May 2014
  #8  
Old May 19th 14, 11:51 PM posted to sci.space.policy,sci.astro,sci.physics,rec.arts.sf.science
R Kym Horsell[_2_]
external usenet poster
 
Posts: 111
Default Full phase Earth from the lunar surface?

In sci.physics R Kym Horsell wrote:
....

I found
http://upload.wikimedia.org/wikipedi...ns/thumb/b/ba/
Lunar_libration_with_phase_Oct_2007_450px.gif/220px-
Lunar_libration_with_phase_Oct_2007_450px.gif

which shows the various components of the EM system working together.

I had made a movie of the reverse view, but can't locate it at present.

In the 90s I fell in with a bunch of Berkeley math dropouts that had
graduated in things like topology or group theory yet didn't want to make
planet busting weapons. So they'd "retired"
to a farm in the Valley where they lived off
the proceeds of agricultural products, hand-made
icecream, and posters.

That's where I came in. We made a calendar of the earth as seen
from the moon over the period of a year, so I had to do the calcs
as best I could at the time.

From memory the apparent motion of the earth is around 2.5 mins/hour
so it's a pretty slow earthrise even from the 20% of the moon from which it's
visible. It takes 2 or 3 days just to fully cross the horizon line.

--
http://arstechnica.com/science/2014/...ing-after-the-
dinosaur-killing-asteroid-impact/
As best we can make out, a 10 kilometer wide asteroid struck the
Earth along the coast of the Yucat?n Peninsula [about 65 mn y ago] and
produced a shockwave and fireball of unfathomable scale. As tsunamis
swept across the Gulf of Mexico and wildfires raged, huge amounts of
sulfur (from rock vaporized by the impact) and soot were lifted into
the air, blocking sunlight from reaching the surface. With the fires
followed by cold and greatly diminished photosynthesis (sunlight
might have dropped by 80%), ecosystems collapsed.
The analysis indicated local sea surface temperatures of 30-31C
[atm CO2 about 1000 ppmv; deep ocean temp ~ 8C]
prior to the impact. The data from the post-tsunami layers are a
little variable (possibly due to the stirring up of the sediment by
storms), but it records temperatures fully 2-7C cooler than that.
After that, temperatures rose to 1-2C higher than they had been
before the impact.
[deep ocean temps maxed at ~ 12C about 50 Mya]
[Also see
Andrew Glikson, "Copenhagen: a warning from the history of Earth", 7 Dec 2009.
http://www.onlineopinion.com.au/view...e=9793&page=0].
  #9  
Old May 20th 14, 12:11 AM posted to sci.space.policy,sci.astro,sci.physics,rec.arts.sf.science
Lord Androcles[_3_]
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Posts: 575
Default Full phase Earth from the lunar surface?



"Robert Clark" wrote in message ...

The full Moon sometimes looks huge when it's low on the horizon. I was
wondering if the same effect would occur on the Moon if we saw a full phase
Earth from the lunar surface.
There haven't been many pictures taken from the surface of the Moon that
show the Earth. Here's one:

http://moonpans.com/prints/CernanEarth.jpg

The Earth can look pretty large low on the horizon from lunar orbit even
when not at full phase as shown by this Apollo 11 image taken from orbit:

http://www.astronautix.com/graphics/0/10075247.jpg

Are there images taken from the lunar surface either by robots or manned
missions that show the Earth rise at or close to full phase?

Nice article by Dr. Pauls Spudis:

Earth Rising.
Earth as seen from the Moon is always in the same place – true or false? It
depends.
By Paul D. Spudis
May 15, 2014
Quote:
Thus, there are places on the Moon from which we can stand and
contemplate the sheer beauty and magnificence of a slowly rising Earth.
Given the sea change in global perspective provided by the famous Earthrise
picture taken by the Apollo 8 crew almost fifty years ago, what societal
impacts will occur when a human being stands on the lunar surface and
watches the Earth slowly rise above the horizon? I suspect that a similar
shift in planetary perspective will occur. If history is any guide, such a
shift will have profound psychological and political implications – both
positive and negative – in our reach for the stars.
http://www.airspacemag.com/daily-pla...#ixzz321FRfV82

I wonder if a Google Lunar X-Prize entrant could land at one of the
locations where Earthrise would be visible.


Bob Clark
================================================== =========
http://www.universetoday.com/20489/m...ared-to-earth/

-- Lord Androcles, Zeroth Earl of Medway

  #10  
Old May 20th 14, 01:51 AM posted to sci.astro
Barry Schwarz[_2_]
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Posts: 52
Default Full phase Earth from the lunar surface?

On Mon, 19 May 2014 15:19:58 -0700 (PDT), dlzc wrote:

Dear Robert Clark:

On Monday, May 19, 2014 3:28:58 AM UTC-7, Robert Clark wrote:

The full Moon sometimes looks huge when it's
low on the horizon. I was wondering if the
same effect would occur on the Moon if we saw
a full phase Earth from the lunar surface.


Well no, since the Moon is tidally locked to the Earth. The Earth always looks the same size, whereever you are. Now from orbit around the Moon, sure.


Some have posited that the apparent increase in size when the moon is
near the horizon is due to atmospheric refraction. Others have posted
that this is not the case. I have no idea which is correct but -

If the observation is due to atmospheric refraction, it would not
occur on the moon do to the absence of an atmosphere.

If it is not due to refraction, then during a new moon, someone
standing on the moon anywhere along the terminator would see the Earth
just above the horizon. (Regardless of the phase, if he doesn't move
the Earth will always be just above the horizon.) Unless there is
something else unique about looking at the moon, the lunar observer
looking at Earth should experience the same type of enlargement. Of
course, he would have to drive for quite a while to a position where
the Earth was well off the horizon to notice the difference.

--
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