Why does the moon always have a dark side?

Discussion in 'Digital Photography' started by Richard Henry, Apr 7, 2004.

  1. <> wrote in message news:40735763.7140.A8CBF0@localhost...
    > title says it all


    Because there is only one sun?

    Actually the "dark" side can be lit up quite a bit from reflected Earthshine
    when the angles are right.
     
    Richard Henry, Apr 7, 2004
    #1
    1. Advertising

  2. wrote:
    >
    > title says it all


    The Moon is lit by the Sun. The Sun is off to one side of the Moon.
    One side lit, one side dark. You would need two suns to light both
    sides at the same time.

    --
    John Popelish
     
    John Popelish, Apr 7, 2004
    #2
    1. Advertising

  3. Richard Henry

    vhl Guest

    wrote:
    > title says it all


    Its because by some fluky chance, the moon rotates at the
    same rate as the earth does so the near side is always
    facing the earth, so even when its in shadow, its still
    the same side. We can see more than half the sphere as
    we can see it from different parts of the earth.

    --
    Vin
    Melbourne, Australia
    Remove no and spam from both sides of the @ sign email address to reply
     
    vhl, Apr 7, 2004
    #3
  4. Richard Henry

    Squishua Guest

    On Wed, 07 Apr 2004 01:20:35 -0400, wrote:

    >title says it all


    Over the course of a lunar day (29.5 earth days) all sides of the moon
    receive sunlight. If you are operating under the assumption that one
    particular side of the moon *never* recieves light, you are mistaken.

    The "dark side" of the moon refers to the "forbidden" side that is
    never viewed directly from earth (or at least has not been viewed
    directly for eons) because the same side of the moon always faces us.

    Regards,

    Squishua


    (remove the capital letters from my e-mail address to contact me)
     
    Squishua, Apr 7, 2004
    #4
  5. Richard Henry

    Ida Noe Guest

    Ahh..so what kind of light fill ratio should one use to bring out the
    shadows nicely?

    How much depth of field would you need to get the whole moon in focus?

    Would you tell the moon to say "cheese"?



    On 7-Apr-2004, John Popelish <> wrote:

    > wrote:
    > >
    > > title says it all

    >
    > The Moon is lit by the Sun. The Sun is off to one side of the Moon.
    > One side lit, one side dark. You would need two suns to light both
    > sides at the same time.
    >
    > --
    > John Popelish
     
    Ida Noe, Apr 7, 2004
    #5
  6. <> wrote in message news:40735763.7140.A8CBF0@localhost...
    > title says it all
    >


    No such thing as the dark side of the moon. Matter of fact, its all dark.

    (Blatantly stolen from Floyd)
     
    Jason Pawloski, Apr 7, 2004
    #6
  7. Richard Henry

    Obake Guest

    In article <40735763.7140.A8CBF0@localhost>, wrote:
    >title says it all
    >


    one side of the moon is heavier then the other. the heavy side was/is
    attracted by earth's gravity and over the many many years has stabilized so
    only one 'side' of the moon faces the earth.
     
    Obake, Apr 7, 2004
    #7
  8. Richard Henry

    Nacho Guest


    > one side of the moon is heavier then the other. the heavy side was/is
    > attracted by earth's gravity and over the many many years has stabilized so
    > only one 'side' of the moon faces the earth.


    This is completely off-topic, but it is not true. The point is tidal
    forces. Tidal forces creates intense deformations in the moon when it
    rotated, time ago. This deformations uses energy, obtained from its
    rotation. So it slowly stopped. It could have been stopped in any other
    position.

    Best regards.
     
    Nacho, Apr 7, 2004
    #8
  9. wrote:

    > title says it all


    Any light seen from the Moon is relected light. Since the only
    significan t source of the light is from the Sun and there is only one
    Sun, then only one side of the Moon is lit up by the Sun.

    Bob Kolker

    >
     
    Robert J. Kolker, Apr 7, 2004
    #9
  10. Richard Henry

    Sam Wormley Guest

    "Robert J. Kolker" wrote:
    >
    > wrote:
    >
    > > title says it all

    >
    > Any light seen from the Moon is relected light. Since the only
    > significan t source of the light is from the Sun and there is only one
    > Sun, then only one side of the Moon is lit up by the Sun.
    >
    > Bob Kolker
    >


    We (posters) should add that only half of the spheroid is illuminated,
    a opposed to more than half, because the illumination source is far
    enough away to approximate a point source.
     
    Sam Wormley, Apr 7, 2004
    #10
  11. Richard Henry

    Mike Guest

    wrote in message news:<40735763.7140.A8CBF0@localhost>...
    > title says it all


    Good question and I see you did not get a straight answer from the
    physics "gurus" hanging out in this NG.

    What is called a "dark side" of the moon is actually the "far side"
    which is never seen by an observer on earth. But the moon gets sun
    shine on all of its sides as it turns. The reason there is a "far
    side" is that over the millions of years the moon goes around the
    earth, the gravitational pull of the earth has slowed moon's rotation
    about its axis down so it matches the period of its revolution around
    the earth. One can easily see that when this is true there is always a
    "far side" not seen by the earth and called the "dark side" but it
    actually gets sun shine all over the place.

    Mike
     
    Mike, Apr 7, 2004
    #11
  12. "Mike" <> wrote in message
    news:...
    > wrote in message

    news:<40735763.7140.A8CBF0@localhost>...
    > > title says it all

    >
    > Good question and I see you did not get a straight answer from the
    > physics "gurus" hanging out in this NG.


    It looks to me that all but 2 of the responses were "straight".
     
    Richard Henry, Apr 7, 2004
    #12
  13. Richard Henry

    Uncle Al Guest

    wrote:
    >
    > title says it all


    Why does the Earth always have a dark side?

    --
    Uncle Al
    http://www.mazepath.com/uncleal/
    (Toxic URL! Unsafe for children and most mammals)
    "Quis custodiet ipsos custodes?" The Net!
     
    Uncle Al, Apr 7, 2004
    #13
  14. Richard Henry

    Chris Brown Guest

    In article <c50tbq$>, Nacho <> wrote:
    >
    >> one side of the moon is heavier then the other. the heavy side was/is
    >> attracted by earth's gravity and over the many many years has stabilized so
    >> only one 'side' of the moon faces the earth.

    >
    >This is completely off-topic, but it is not true.


    Actually, he's quite right - although tidal forces are involved, your
    explanation is trivially wrong:

    >The point is tidal
    >forces. Tidal forces creates intense deformations in the moon when it
    >rotated, time ago. This deformations uses energy, obtained from its
    >rotation. So it slowly stopped.


    The problem with this is that the Moon hasn't actually stopped rotating at
    all. It rotates on its axis once every 28 days. This is the same as its
    orbital period, so that we always see the same side. If it had stopped, we'd
    see opposite sides at 14 day intervals.

    The reason the same side faces us is because the orbital and rotational
    periods coincide. The reason they coincide is indeed because tidal forces
    slow the rotation down, but, and this is the important bit, the Moon's
    centre of mass is offset from its centre of rotation, like a bicycle wheel
    that has a weight on one side. Over the N billion years that the Moon has
    been orbiting the Earth, tidal forces have slowed the rotation until it
    reached the optimal rotational speed, which is the speed where the Moon's
    centre of gravity is always as close as possible to the centre of the Earth,
    i.e. always facing down.
     
    Chris Brown, Apr 7, 2004
    #14
  15. Richard Henry

    Guest

    In article <4073da81$0$25661$>, (Obake) writes:
    > In article <40735763.7140.A8CBF0@localhost>, wrote:
    >>title says it all
    >>

    >
    > one side of the moon is heavier then the other. the heavy side was/is
    > attracted by earth's gravity and over the many many years has stabilized so
    > only one 'side' of the moon faces the earth.


    Under the tidal forces associated with the Earth's gravity, the
    moon naturally assumes a slightly elongated shape -- something
    like an egg. Those same tidal forces naturally pull the long axis
    into alignment with the earth.

    When the moon was rotating at a different speed than it revolved around
    the Earth, it was something like a gushy soft-boiled egg -- always a
    little elongated, but with various pieces of the lunar crust continuously
    rotating into and out of the bulges. Since the moon is (or was) neither
    completely rigid nor completely fluid, the viscosity would cause the
    bulges to lag a little. And this would, in turn, cause a tidal torque,
    eventually bringing the moon's rotation rate into lockstep with its
    orbital period about the earth.

    A moon that was merely heavy on one side would continue to spin
    out of synch forever (*), much like an unbalanced frictionless
    bicycle wheel. It takes a gushy satellite to efficiently lock up with
    its partner.

    I've never learned this out of a textbook in so many words, but it
    seems pretty obvious.

    John Briggs

    (*) the rotation of an unbalanced satellite can eventually damp due to
    other effects, but the time frames are much longer than the induced
    tidal drag scenario described above.
     
    , Apr 7, 2004
    #15
  16. Richard Henry

    Jay Windley Guest

    "Mike" <> wrote in message
    news:...
    |
    | Good question and I see you did not get a straight answer
    | from the physics "gurus" hanging out in this NG.

    Well, be fair. It wasn't clear whether itnwas a phase angle question or a
    tidal locking question. Contrary to the original poster's statement, the
    title did not say it all. I think both interpretations of the question were
    answered courteously.

    --
    |
    The universe is not required to conform | Jay Windley
    to the expectations of the ignorant. | webmaster @ clavius.org
     
    Jay Windley, Apr 7, 2004
    #16
  17. Richard Henry

    Ian Stirling Guest

    In sci.physics Sam Wormley <> wrote:
    > "Robert J. Kolker" wrote:
    >>
    >> wrote:
    >>
    >> > title says it all

    >>
    >> Any light seen from the Moon is relected light. Since the only
    >> significan t source of the light is from the Sun and there is only one
    >> Sun, then only one side of the Moon is lit up by the Sun.


    > We (posters) should add that only half of the spheroid is illuminated,
    > a opposed to more than half, because the illumination source is far
    > enough away to approximate a point source.


    No, it's not.
    Somewhere around an extra half a degree, or some extra 10Km of illumingation
    round the edge of the illuminated area.

    Anyway, the correct answer is that there has been a dark side of the
    moon since 1973, as that's when the album was released.
     
    Ian Stirling, Apr 7, 2004
    #17
  18. Richard Henry

    ZZBunker Guest

    wrote in message news:<40735763.7140.A8CBF0@localhost>...
    > title says it all


    Because the moon does not orbit the Earth,
    it is locked in Earth orbit.

    And also because the dark side of the moon
    is do much dark as it is colder than
    Mars.
     
    ZZBunker, Apr 7, 2004
    #18
  19. Richard Henry

    Jim Hutton Guest

    But it does NOT have a dark side.
    How anthropocentric!
    J

    "ZZBunker" <> wrote in message
    news:...
    > wrote in message

    news:<40735763.7140.A8CBF0@localhost>...
    > > title says it all

    >
    > Because the moon does not orbit the Earth,
    > it is locked in Earth orbit.
    >
    > And also because the dark side of the moon
    > is do much dark as it is colder than
    > Mars.
     
    Jim Hutton, Apr 7, 2004
    #19
  20. Richard Henry

    Jeff Guest

    Squishua wrote:
    > On Wed, 07 Apr 2004 01:20:35 -0400, wrote:


    > The "dark side" of the moon refers to the "forbidden" side that is
    > never viewed directly from earth (or at least has not been viewed
    > directly for eons) because the same side of the moon always faces us.


    Damn gravity. ;)
     
    Jeff, Apr 7, 2004
    #20
    1. Advertising

Want to reply to this thread or ask your own question?

It takes just 2 minutes to sign up (and it's free!). Just click the sign up button to choose a username and then you can ask your own questions on the forum.
Similar Threads
  1. Bratboy

    An AC3 file of Dark side of the moon?

    Bratboy, Oct 29, 2005, in forum: DVD Video
    Replies:
    6
    Views:
    569
    Tarkus
    Nov 2, 2005
  2. tednat

    DARK SIDE OF THE MOON

    tednat, Dec 18, 2004, in forum: Digital Photography
    Replies:
    7
    Views:
    285
    Bob Harrington
    Dec 20, 2004
  3. Replies:
    3
    Views:
    591
    Michael Gray
    Sep 15, 2005
  4. Replies:
    11
    Views:
    840
    Denis Loubet
    Jan 12, 2006
  5. Shane

    I have joined the dark side :)

    Shane, Nov 30, 2005, in forum: NZ Computing
    Replies:
    17
    Views:
    547
    Robert Cooze
    Dec 1, 2005
Loading...

Share This Page