The Earth Moves: The Ten Principles of Science

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The Earth Moves The Ten Principles of Science

• SNC2D

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The Ten Principles of ScienceDaily Learning Goal

• The student will be able to identify and explain
  the principles that underlie the development of
  science and apply them to examples from the
  history of science.

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Taylor

• In 1908, an amateur American geologist named
  Frank Bursley Taylor was struck by the similarity
  in shape between the facing coastlines of Africa
  and South America, and from this observation he
  developed the idea that the continents had once
  slid around.

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Taylor

• He even suggested that the crunching together of
  continents could have thrust up the world's
  mountain chains. He failed, however, to produce
  much in the way of evidence, and the theory was
  considered too crackpot to merit serious
  attention.

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Wegener

• In Germany, however, the idea was appropriated by
  Alfred Wegener, a meteorologist, who investigated
  the many plant and fossil anomalies that did not
  fit comfortably into the standard model of Earth
  history and realized that very little of it made
  sense if conventionally interpreted.

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Wegener

• Animal fossils repeatedly turned up on opposite
  sides of oceans that were clearly too wide to
  swim. How, he wondered, did marsupials travel
  from South America to Australia? How did
  identical snails turn up in Scandinavia and New
  England?

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Wegener

• And how did one account for coal seams and other
  semi-tropical remnants in frigid spots like
  Spitsbergen in Svalbard, four hundred miles north
  of Norway, if the spots had not somehow migrated
  there from warmer climes?

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Wegener

• Wegener hypothesized that the world's continents
  had formed a single landmass he called Pangaea,
  where flora and fauna had been able to mingle,
  before the continents had split apart and floated
  off to their present positions. All this he put
  together in a book called The Origin of
  Continents and Oceans, which was published in
  German in 1912.

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Land Bridges

• Geologists, to get around the problems of fossil
  distributions, responded to this by positing
  ancient land bridges wherever they were needed.
  When an ancient horse named Hipparion was found
  to have lived in France and Florida at the same
  time, a land bridge was drawn across the
  Atlantic.

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Land Bridges

• When it was realized that ancient tapirs had
  existed simultaneously in South America and
  Southeast Asia a land bridge was drawn there,
  too. Soon maps of prehistoric seas were almost
  solid with hypothesized land bridges that had
  somehow vanished without leaving a trace of their
  former existence.

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Trilobites

• But even land bridges couldn't explain some
  things. One species of trilobite that was well
  known in Europe was also found to have lived on
  Newfoundland but only on one side. No one could
  persuasively explain how it had managed to cross
  two thousand miles of hostile ocean but then
  failed to find its way around the corner of a
  200-mile-wide island.

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Trilobites

• Even more awkwardly anomalous was another species
  of trilobite found in Europe and the Pacific
  Northwest but nowhere in between, which would
  have required not so much a land bridge as a
  flyover.

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Holmes

• Yet it was Wegener's theory that was held to be
  full of numerous grave theoretical
  difficulties. Most significantly, he could offer
  no convincing explanation for how the landmasses
  moved about.

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Holmes

• It was the English geologist Arthur Holmes, who
  first suggested a mechanism radioactive warming
  could produce convection currents within the
  Earth that could be powerful enough to slide
  continents around on the surface.

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Holmes

• In his influential textbook Principles of
  Physical Geology, published in 1944, Holmes laid
  out a continental drift theory that was in its
  fundamentals the theory that prevails today.

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Holmes

• At the time, it was widely criticized,
  particularly in the United States, where
  resistance to the theory lasted longer than
  elsewhere. One reviewer there fretted, without
  any evident sense of irony, that Holmes presented
  his arguments so clearly and compellingly that
  students might actually come to believe them.

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Meanwhile. . . .

• Interestingly, oil company geologists had known
  for years that if you wanted to find oil you had
  to allow for precisely the sort of surface
  movement that were implied the theory. But oil
  geologists didn't write academic papers they
  just found oil.

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Sediments

• There was one other major problem with Earth
  theories that no one had resolved where all the
  sediments went. Every year Earth's rivers carried
  massive volumes of eroded material 500 million
  tons of calcium, for instance to the seas.

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Sediments

• If you multiplied this rate by the number of
  years it had been going on, it followed that the
  ocean bottoms should be now be well above the
  ocean tops. Scientists dealt with this problem by
  ignoring it.

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The Ocean Floor

• In the Second World War, a mineralogist named
  Harry Hess was put in charge a ship equipped with
  a fancy new depth sounder called a fathometer,
  which was designed to facilitate beach landings,
  but Hess realized that it could equally well be
  used for scientific purposes and never switched
  it off, even when far out at sea.

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The Ocean Floor

• What he found was entirely unexpected. If the
  ocean floors were ancient, as everyone assumed,
  they should be thickly blanketed with sediments,
  like the mud on the bottom of a river or lake.
  But Hess's readings showed that the ocean floor
  was scored everywhere with canyons, trenches, and
  crevasses and dotted with volcanic seamounts.

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The Ocean Floor

• Throughout the 1950s oceanographers undertook
  more and more sophisticated surveys of the ocean
  floors and discovered that the mightiest and most
  extensive mountain range on Earth was mostly
  underwater.

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The Ocean Floor

• People laying ocean-floor cables in the
  nineteenth century had realized that there was
  something in the mid-Atlantic, but the continuous
  nature and overall scale of the chain was a
  stunning surprise.

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The Ocean Floor

• Moreover, it contained physical anomalies that
  couldn't be explained. Down the middle of the
  mid-Atlantic ridge was a canyon a rift up to
  a dozen miles wide for its entire 12,000-mile
  length. In 1960 core samples showed that the
  ocean floor was quite young at the mid-Atlantic
  ridge but grew progressively older as you moved
  away from it to the east or west.

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Seafloor spreading

• Hess considered the matter and realized that this
  could mean only one thing new ocean crust was
  being formed on either side of the central rift,
  then being pushed away from it as new crust came
  along behind.

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Seafloor spreading

• The Atlantic floor was effectively two large
  conveyor belts, one carrying crust toward North
  America, the other carrying crust toward Europe.
  The process became known as seafloor spreading.

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Subduction

• When the crust reached the end of its journey at
  the boundary with continents, it plunged back
  into the Earth in a process known as subduction,
  which explained where all the sediment went. Hess
  elaborated his ideas in an important paper, which
  was almost universally ignored.

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Matthews and Vine

• However, in 1963, a geophysicist from Cambridge
  University named Drummond Matthews and a graduate
  student of his named Fred Vine, used magnetic
  studies of the Atlantic Ocean floor to
  demonstrate conclusively that the seafloors were
  spreading in precisely the manner Hess had
  suggested and that the continents were in motion
  too.

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Morley

• An unlucky Canadian geologist named Lawrence
  Morley came up with the same conclusion at the
  same time, but couldn't find anyone to publish
  his paper. In what has become a famous snub, the
  editor of the Journal of Geophysical Research
  told him Such speculations make interesting
  talk at cocktail parties, but it is not the sort
  of thing that ought to be published under serious
  scientific aegis. One geologist later described
  it as probably the most significant paper in the
  earth sciences ever to be denied publication.

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Plate tectonics

• At all events, crust in motion was an idea whose
  time had finally come. Today we know that Earth's
  surface is made up of eight to twelve big
  plates and twenty or so smaller ones, and they
  all move in different directions and at different
  speeds.

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Plate tectonics

• They bear only an incidental relationship to the
  landmasses that sit upon them. The North American
  plate, for instance, roughly traces the outline
  of the continent's western coast (which is why
  that area is so seismically active, because of
  the bump and crush of the plate boundary), but
  then extends halfway across the Atlantic to the
  mid-ocean ridge.

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The future?

• Assuming things continue much as at present, the
  Atlantic Ocean will expand until eventually it is
  much bigger than the Pacific. Much of California
  will float off and become a kind of Madagascar of
  the Pacific.

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The future?

• Africa will push northward into Europe, squeezing
  the Mediterranean out of existence and thrusting
  up a chain of mountains of running from Paris to
  Calcutta. Australia will colonize the islands to
  its north.

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The future?

• These are future outcomes, but the events are
  happening now. As we sit here, continents are
  adrift, like leaves on a pond. Thanks to Global
  Positioning Systems we can see that Europe and
  North America are parting at about the speed a
  fingernail grows roughly two metres in a human
  lifetime.

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The Ten Principles

• The cycle of proof describes the process of
  science. The Ten Principles of science describe
  the thinking behind the development of this
  process.

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Objectivity

• Scientists cultivate the ability to gather and
  examine facts. They base their conclusions only
  on these facts.
• Scientific conclusions are based on all the facts
  that have been discovered and only on the facts.
  Scientists spend a large portion of their
  research time familiarizing themselves with the
  current data base they read newly published
  papers and confer with their colleagues, and
  scientists are rigorously critical of both their
  own and of their colleagues' work to ensure that
  all the facts entering the data base are correct
  and not the results of flawed research.

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Objectivity

• 20Th-century geologists had to be familiar with
  the work of other geologists, even (often
  especially) the work of geologists with whom they
  disagreed since if someone presented evidence
  that apparently contradicted their theory, they
  had to modify their theory to accommodate the
  evidence. When Wegener demonstrated that fossil
  evidence was consistent with continental drift,
  the geologic orthodoxy of the day invented
  prehistoric land bridges to attempt to explain
  the evidence.

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Tentativeness

• Scientists do not regard their conclusions as
  final but are willing to modify them if they are
  contradicted by new evidence.
• This principle is perhaps best applied to science
  as a whole rather than to individual scientists,
  who can understandably resist new ideas after
  they have staked their career on the old ones
  but this conservatism is not necessarily a bad
  thing it is important that any new idea prove
  itself before gaining general acceptance.

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Tentativeness

• Einstein's Theory of General Relativity
  overturned the Newtonian understanding of gravity
  but even though his theory explained things the
  Newtonian understanding could not, such as the
  precession of Mercury's orbit, it needed to make
  testable predictions and those testable
  predictions needed to be verified before it was
  generally accepted.

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Tentativeness

• No one other than Wegener paid much attention to
  Taylor's continental drift idea because Taylor
  didn't have much evidence to support it. Even
  after Wegener presented supporting evidence, much
  of it from the fossil record, it was still the
  continental drift theory that was considered to
  have numerous grave theoretical difficulties.
  Only after Holmes proposed a mechanism for the
  drift and Hess described the phenomenon of
  seafloor spreading and Matthews and Vine put all
  the evidence, including magnetic evidence,
  together did the theory gain acceptance. But it
  did finally gain acceptance. Science is
  eventually self-correcting.

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Consistency

• Scientists assume that the behaviour of the world
  is describable in terms of laws which have always
  operated in the same way and that the world which
  we now see is the result of the continuous
  operation of these laws.
• Values like the density of mercury may be
  determined by some scientists and published in
  texts and on websites, and other scientists may
  then use these values in their own work without
  having to verify the density of mercury
  themselves because although these values may
  later be determined to greater accuracy and
  precision by better experimental techniques, the
  values are not going to change randomly because
  the physical laws that govern the universe do not
  change randomly. They are the same as they have
  always been. This is why we assume that the
  results of any scientific experiment should be
  reproducible.

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Consistency

• The processes that shaped the world in the past
  are the same processes that are active now and
  (we assume) will continue to be active in the
  future. This is why the missing sediments in the
  ocean presented a problem to geologists if
  eroded material is being deposited in the oceans
  now, one can assume it was also being deposited
  in the past, and therefore what happened to all
  of it?
• Assuming that the processes will remain the same
  is also why we can speculate with some confidence
  about what the surface of the Earth will look
  like even 50 million years in the future, after
  the Mediterranean Sea has become the
  Mediterranean Mountain Range.

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Causality

• Scientists believe that every phenomenon results
  from discoverable causes.
• At one time many people, particularly in North
  America, suffered from a disease known as
  pellagra. Victims suffered from skin rashes,
  diarrhea, and nausea. In extreme cases, they
  became psychotic and even died. The disease was
  unknown to medicine before the discovery of
  America, but in 1915, over 10 000 people died of
  it. Why did people get pellagra? For a long time,
  medical researchers didn't know, but they always
  assumed that something caused it that it didn't
  just happen. It turned out to be the result of
  a dietary deficiency corn lacks niacin, a B
  vitamin, and people who lived in corn-growing
  districts for whom corn was a major staple of
  their diet would have niacin deficiencies.

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Causality

• The discovery of the mid-Atlantic ridge, which
  was only part of an enormous undersea mountain
  range, was a surprising one. The further
  discovery that at the centre of the ridge was a
  canyon up to twelve miles wide was perplexing.
  But scientists believed that there were
  discoverable explanations for both.

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Parsimony

• Scientists attempt to reduce their view of the
  world to the simplest possible terms. They prefer
  explanations, theories, and hypotheses that
  account for as many phenomena as possible.
• Parsimony is an unwillingness to spend two
  dollars where one would do. The Principle of
  Parsimony was first put forward by the English
  monk William of Occam (1300 1349) and is often
  known to this day as Occam's Razor, the razor
  being an instrument to shave thing down as
  closely as possible. Occam phrased it this way
  Entities must not needlessly be multiplied.

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Parsimony

• If you came down to breakfast in the morning and
  discovered a broken window, a missing television,
  and footprints in the garden outside the window,
  you would probably not assume that a stone
  dropped from an airplane and broke the window, a
  monkey came in through the broken window and took
  the television, and the footprints were caused by
  a neighbour looking in to see what was going on.
  All this is possible it fits well with the
  Principle of Causality but it wouldn't strike
  you as the most likely explanation since it
  assumes four entities the airplane, stone,
  monkey and neighbour. The most likely explanation
  has only one entity a burglar.

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Parsimony

• The ancient land bridges that the geologic
  orthodoxy of the day hypothesized to explain
  fossil distributions were an example of needless
  multiplication. Not only did the explanation
  multiply the number of land bridges needed but
  also the number of geologic mechanisms required
  for their formation and for their disappearance.
  Wegener's explanation of continental drift
  required only one mechanism, though what was
  responsible for the drift was as yet unknown.

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Materiality

• Scientists prefer material and mechanical
  explanations of phenomena, rather than those
  which depend on non-material or supernatural
  factors.
• The Norsemen had a god of thunder, Thor, and
  might explain the event of someone being struck
  and killed by lightning as a blow struck by an
  angry god. Even today, some people might say that
  the man was killed as a judgment sent by God
  because of some sin he had committed. A
  scientist, seeing the same thing, would explain
  it by looking at the physical laws that describe
  the behaviour of atmospheric electricity. The
  Principle of Materiality does not prevent the
  scientist from believing in God or even Thor. The
  scientist does not claim that miracles can never
  occur that would be contrary to the Principle
  of Tentativeness. But all other possibilities
  must be eliminated first.

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Materiality

• Before geology became a science at all, features
  of the landscape were understood as the work of
  God and God alone. Some people, even today, still
  insist that the Grand Canyon was produced by the
  Biblical Flood and not by the erosion of
  millennia. The problem with such supernatural
  explanations is that they have no predictive
  power because God is said to work in mysterious
  ways, people cannot guess what is going to happen
  next and can only pray. Scientists who believe in
  material explanations such as erosion can make
  plans to prevent the erosion of riverbanks and
  shorelines.

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Relativeness

• Scientists think of the world and the phenomena
  in it as consisting of sets of relationships
  rather than of absolutes.
• Meteorologists scientists who study climate and
  weather systems have to consider many factors
  from the movement of the Earth around the Sun and
  the Earth's rotation on its axis to the
  convection effects of rising warm air or of ocean
  currents. All of these factors interact to
  determine whether or not it will be cloudy or
  sunny, rainy or snowy, so it is important to
  understand not only these factors individually
  but to understand the relationships between them.
  The Earth itself is a similarly complex system,
  even if rocks move more slowly. It even convects.

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Dynamism

• Scientists expect nature to be dynamic rather
  than static and to show variation and change.
• The Principle of Dynamism is consistent with the
  Principle of Consistency. The Principle of
  Consistency concerns the laws and processes of
  the universe, which remain constant the
  Principle of Dynamism concerns the universe
  itself, which because of those laws and processes
  is continuously changing.

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Dynamism

• These changes may happen on very short timescales
  almost instantly in the case of explosions or
  hourly or daily in the case of the weather or
  they may happen on very long timescales North
  America and Europe are moving apart from each
  other at about the same rate that your
  fingernails grow. Baja California will eventually
  separate from North America, but not in the space
  of a human lifetime.

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Continuous Discovery

• Scientists hope that it will be possible to go on
  learning about the material world, and the
  material universe of which it is part, until
  eventually all may be understood.
• Often there are questions in science that have to
  wait until the right knowledge in some other
  field comes along or the right experimental
  techniques are discovered.

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Continuous Discovery

• Astronomers were limited in what they could find
  out about the universe until the telescope was
  invented medical researchers couldn't find out
  much about the causes of cancer until the
  biochemistry of animal cells was understood in
  some detail. But every scientist hopes that right
  knowledge and techniques will be developed and
  that his or her work is contributing to the
  scientific data base and to future discoveries.

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Continuous Discovery

• Those scientists who collected data on the
  distribution of fossils in South America and
  Africa did not know at the time that their data
  would be used to support the theory of
  continental drift. Wegener pursued the theory of
  continental drift even though he did not know of
  a mechanism that could move the continents. It
  was the apparently unrelated discovery of
  radioactivity and of radioactive heating that
  eventually provided the theory with its
  mechanism.

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Social Limitation

• The social framework within which scientists
  operate may determine and limit the kinds of
  problems with which they work and may also
  influence their conclusions.
• Some subjects of scientific research are of
  obvious practical value. Medical research,
  studies of the climate and of weather events,
  improving the safety and efficiency of nuclear
  power generation all these are examples of
  applied research. Applied research, because it is
  likely to benefit society as a whole and/or
  enrich those who conduct the research, is the
  type likely to be encouraged by governments and
  private industry and therefore the type likely
  to be funded. But pure or curiosity-based
  research, in which the objective is simply to
  find out more about the workings of the universe,
  is necessary too.

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Social Limitation

• Although there may be no obvious and immediate
  practical use for the discoveries of pure or
  curiosity-based research, it is these discoveries
  that will form the basis for future applied
  research. Prime numbers were once just a
  mathematical curiosity today they form the basis
  for modern encryption systems, including internet
  security.

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Social Limitation

• There is an apocryphal story that the British
  Prime Minister of the day, William Gladstone,
  once asked the physicist Michael Faraday the
  value of electricity Faraday is said to have
  replied, I do not know. You may as well ask, 'Of
  what use is a newborn baby?'

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Social Limitation

• The historical unwillingness of governments and
  industry to fund pure or curiosity-based research
  is one reason why a lot of important fundamental
  work has been done by scientists who were at the
  time employed to work on something else. Albert
  Einstein developed his theory of special
  relativity while employed as a patent clerk.
  Turner, who first proposed the idea of
  continental drift, was a wealthy and thus
  self-funded amateur Wegener was a meterologist.

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Social Limitation

• Sometimes science is impeded not by financial but
  by ethical or philosophical considerations, many
  of them valid. For years medical science was not
  permitted to perform dissections of human
  cadavers and had to employ grave robbers to
  supply physicians in training and medical
  researchers with corpses. Today many people,
  including many scientists, oppose stem-cell
  research on human embryos.