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News Item - Earth losing its magnetism

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  • Todd S. Greene
    [posted by Todd Greene] from: http://news.bbc.co.uk/1/hi/sci/tech/3359555.stm [go to link for full article] ... Earth loses its magnetism by Molly Bentley (BBC
    Message 1 of 4 , Jan 1, 2004
      [posted by Todd Greene]

      from: http://news.bbc.co.uk/1/hi/sci/tech/3359555.stm
      [go to link for full article]

      ----------------------------------------------------------------

      Earth loses its magnetism
      by Molly Bentley (BBC News, 12/31/03)

      Scientists have known for some time that the Earth's magnetic field
      is fading.

      Like a Kryptonite-challenged Superman, its strength has steadily and
      mysteriously waned, leaving parts of the planet vulnerable to
      increased radiation from space.

      Some satellites already feel the effects.

      What is uncertain is whether the weakened field is on the way to a
      complete collapse and a reversal that would flip the North and South
      Poles.

      Compasses pointing North would then point South.

      It is not a matter of whether it will happen, but when, said
      scientists who presented the latest research on the subject at a
      recent meeting of the American Geophysical Union in San Francisco.

      But when is hard to pinpoint. The dipole reversal pattern is erratic.

      "We can have periods without reversals for many millions of years,
      and we can have four or five reversals within one million years,"
      said Yves Gallet, from Institut de Physique du Globe de Paris,
      France, who studies the palaeomagnetic record and estimates that the
      current decay started 2,000 years ago.
    • lipscombgene
      ... Gene: My concern is this type of news will only embolden the YEC to continue repeating their argument about the age of the earth from the decay of the
      Message 2 of 4 , Jan 1, 2004
        --- In creationism@yahoogroups.com, "Todd S. Greene" <greeneto@y...> wrote:
        > [posted by Todd Greene]
        >
        > from: http://news.bbc.co.uk/1/hi/sci/tech/3359555.stm
        > [go to link for full article]
        >
        > ----------------------------------------------------------------
        >
        > Earth loses its magnetism
        > by Molly Bentley (BBC News, 12/31/03)
        >
        > Scientists have known for some time that the Earth's magnetic field
        > is fading.

        Gene: My concern is this type of news will only embolden the YEC to continue
        repeating their argument about the age of the earth from the decay of the magnetic
        field.
      • Todd S. Greene
        ... Hi, Gene. Long time no hear from! How are you? Anyway, I have the same expectation of YECs as you do. Which goes to show how they will continue to ignore
        Message 3 of 4 , Jan 1, 2004
          --- In creationism, Gene Wright wrote (post #16276):
          > --- In creationism, Todd Greene wrote:
          >>
          >> from: http://news.bbc.co.uk/1/hi/sci/tech/3359555.stm
          >> [go to link for full article]
          >>
          >> ----------------------------------------------------------------
          >>
          >> Earth loses its magnetism
          >> by Molly Bentley (BBC News, 12/31/03)
          >>
          >> Scientists have known for some time that the Earth's magnetic
          >> field is fading.
          >
          > Gene: My concern is this type of news will only embolden the YEC
          > to continue repeating their argument about the age of the earth
          > from the decay of the magnetic field.

          Hi, Gene.

          Long time no hear from! How are you?

          Anyway, I have the same expectation of YECs as you do. Which goes to
          show how they will continue to ignore the relevant geology and
          physics on the subject, some of which is discussed in the online
          article I quoted this from. Indeed, I think that when they use their
          YEC argument about the earth's magnetic field decay it gives us a
          great example of how young earth creationists take things out of
          context and only give us half the story (or less) and thus
          misrepresent and mischaracterize matters by omission and distortion
          based on this omission.

          Regards,
          Todd Greene
          http://www.creationism.cc/
        • lipscombgene
          Faintest Spectra Ever Raise Glaring Question: Why do Galaxies in the Young Universe Appear so Mature? Until now, astronomers have been nearly blind when
          Message 4 of 4 , Jan 6, 2004
            Faintest Spectra Ever Raise Glaring Question: Why do Galaxies
            in the Young
            Universe Appear so Mature?

            Until now, astronomers have been nearly blind when looking
            back in time to
            survey an era when most stars in the Universe were expected to
            have formed. This
            critical cosmological blind-spot has been removed by a team
            using the Frederick
            C. Gillett Gemini North Telescope, showing that many galaxies
            in the young
            Universe are not behaving as expected some 8-11 billion years
            ago.

            The surprise: these galaxies appear to be more fully formed and
            mature than
            expected at this early stage in the evolution of the Universe. This
            finding is
            similar to a teacher walking into a classroom expecting to greet
            a room full of
            unruly teenagers and finding well-groomed young adults.

            "Theory tells us that this epoch should be dominated by little
            galaxies crashing
            together," said Dr. Roberto Abraham (University of Toronto) who
            is a
            Co-Principal Investigator of the team conducting the
            observations at Gemini. "We
            are seeing that a large fraction of the stars in the Universe are
            already in
            place when the Universe was quite young, which should not be
            the case. This
            glimpse back in time shows pretty clearly that we need to re-
            think what happened
            during this early epoch in galactic evolution. The theoreticians
            will definitely
            have something to gnaw on!"

            The results were announced today at the 203rd meeting of the
            American
            Astronomical Society in Atlanta, Georgia. The data will soon be
            released to the
            entire astronomical community for further analysis, and three
            papers have been
            submitted for publication in Nature, The Astrophysical Journal,
            and The
            Astronomical Journal.

            These observations are from a multinational investigation,
            called the Gemini
            Deep Deep Survey (GDDS), which used a special technique to
            capture the faintest
            galactic light ever dissected into the rainbow of colors called a
            spectrum. In
            all, spectra from over 300 galaxies were collected, most of which
            are within
            what is called the "Redshift Desert," a relatively unexplored
            period of the
            Universe seen by telescopes looking back to an era when the
            universe was only
            3-6 billion years old. These spectra represent the most
            complete sample ever
            obtained of galaxies in the Redshift Desert. By obtaining large
            amounts of data
            from four widely separated fields, this survey provides the
            statistical basis
            for drawing conclusions that have been suspected by past
            observations done by
            the Hubble Space Telescope, Keck Observatory, Subaru
            Telescope and the Very
            Large Telescope over the past decade.

            Studying the faint galaxies at this epoch when the Universe was
            only 20-40% of
            its current age presents a daunting challenge to astronomers,
            even when using
            the light-gathering capacity of a very large telescope like Gemini
            North with
            its 8-meter mirror. All previous galaxy surveys in this realm have
            focused on
            galaxies where intense star formation is occurring, which makes
            it easier to
            obtain spectra but produces a biased sample. The GDDS was
            able to select a more
            representative sample including those galaxies which hold the
            most stars --
            normal, dimmer, and more massive galaxies -- hat demand
            special techniques to
            coax a spectrum from their dim light.

            "The Gemini data is the most comprehensive survey ever done
            covering the bulk of
            the galaxies that represent conditions in the early Universe.
            These are the
            massive galaxies that are actually more difficult to study
            because of their lack
            of energetic light from star formation. These highly developed
            galaxies, whose
            star-forming youth is in fact long gone, just shouldn't be there,
            but are," said
            Co-Principal Investigator Dr. Karl Glazebrook (Johns Hopkins
            University).

            Astronomers trying to understand this issue might have to put
            everything on the
            table. "It is unclear if we need to tweak the existing models or
            develop a new
            one in order to understand this finding," said the survey's third
            Co-Principal
            Investigator, Dr. Patrick McCarthy (Observatories of the Carnegie
            Institution).
            "It is quite obvious from the Gemini spectra that these are
            indeed very mature
            galaxies, and we are not seeing the effects of obscuring dust.
            Obviously there
            are some major aspects about the early lives of galaxies that we
            just don't
            understand. It is even possible that black holes might have been
            much more
            ubiquitous than we thought in the early Universe and played a
            larger role in
            seeding early galaxy formation."

            What is arguably the dominant galactic evolution theory
            postulates that the
            population of galaxies at this early stage should have been
            dominated by
            evolutionary building blocks. Aptly called the Hierarchical Model,
            it predicts
            that normal to large galaxies, like those studied in this work,
            would not yet
            exist and would instead be forming from local beehives of activity
            where big
            galaxies grew. The GDDS reveals that this might not be the
            case.

            The spectra from this survey were also used to determine the
            pollution of the
            interstellar gas by heavy elements (called "metals") produced by
            stars. This is
            a key indicator of the history of stellar evolution in galaxies.
            Sandra Savaglio
            (Johns Hopkins University), who studied this aspect of the
            research said, "Our
            interpretation of the Universe is strongly affected by the way we
            observe it.
            Because the GDDS observed very faint galaxies, we could detect
            the interstellar
            gas even if partly obscured by the presence of dust. Studying the
            chemical
            composition of the interstellar gas, we discovered that the
            galaxies in our
            survey are more metal-rich than expected."

            Caltech astronomer, Dr. Richard Ellis commented, "The Gemini
            Deep Deep Survey
            represents a very significant achievement, both technically and
            scientifically.
            The survey has provided a new and valuable census of galaxies
            during a key
            period in cosmic history, one that has been difficult to study until
            now,
            particularly for the quiescent component of the galaxy
            population."

            Making observations in the Redshift Desert has frustrated
            modern astronomers for
            the last decade. While astronomers have known that plenty of
            galaxies must exist
            in the Redshift Desert, it is only a "desert" because we couldn't
            get good
            spectra from many of them. The problem lies in the fact that key
            spectroscopic
            features used to study these galaxies have been redshifted --
            due to the
            expansion of the Universe -- into a part of the optical spectrum
            that
            corresponds to a faint, natural, obscuring glow in the Earth's
            nighttime atmosphere.

            To overcome this problem, a sophisticated technique called
            "Nod and Shuffle" was
            used on the Gemini telescope. "The Nod and Shuffle technique
            enables us to skim
            off the faint natural glow of the night sky to reveal the tenuous
            spectra of
            galaxies beneath it. These galaxies are over 300 times fainter
            than this sky
            glow," explains Dr. Kathy Roth, an astronomer at Gemini who
            was also part of the
            team and obtained much of the data. "It has proven to be an
            extremely effective
            way to radically reduce the "noise" or contamination levels that
            are found in
            the signal from an electronic light detector."

            Each observation lasted the equivalent of about 30 hours and
            produced nearly 100
            spectra simultaneously. The entire project required over 120
            total hours of
            telescope time. "This is a lot of valuable time on the sky, but
            when you
            consider that it has allowed us to help fill in a crucial 20% gap in
            our
            understanding of the Universe, it was time well spent," adds Dr.
            Glazebrook who
            developed the use of Nod and Shuffle with Joss Hawthorn for
            faint galaxy
            observations while at the Anglo-Australian Observatory a few
            years ago. A more
            complete history and explanation of the technique, including its
            original
            development in the mid 90's can be found on the Nod and
            Shuffle background page,
            <http://www.gemini.edu/project/announcements/press/2004-1-
            nod.html>

            Previous studies in the Redshift Desert have concentrated on
            galaxies that were
            not necessarily representative of mainstream systems. For this
            study, galaxies
            were carefully selected based upon data from the Las
            Campanas Infrared Survey in
            order to assure that strong ultraviolet emitting starburst galaxies
            were not
            oversampled. "This study is unique in that we were able to study
            the red end of
            the spectrum, and this tells us about the ages of old stars," says
            Dr. Abraham.
            "We undertook incredibly long observations with Gemini -- about
            ten times as
            long as typical exposures. This let us look at much fainter
            galaxies than is
            usually the case, and let us focus on the bulk of the stars,
            instead of just the
            flashy young ones. This makes it a lot easier for us to work out
            how the
            galaxies are evolving. We are no longer guessing at it by
            studying young objects
            and assuming the old objects were not contributing much to the
            story of galaxy
            evolution. It turns out that there are lots of old galaxies out there,
            but
            they're really hard to find."
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