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Seminar Agenda
 Visualizing a Black Hole
 Very Small and Far Away: Measuring and
Observing Extremes
 Questions & Answers
Visualizing a Black Hole
Before this unit, what was your
exposure to the concept of a
black hole?
Visualizing a Black Hole
Visualizing a Black Hole
Visualizing a Black Hole
What is a black hole?
Visualizing a Black Hole
Less Technical Answer:
A black hole is a region of space that has
so much mass concentrated in it that
there is no way for a nearby object to
escape its gravitational pull.
Visualizing a Black Hole
Technical Answer:
A black hole is formed when a star of sufficient
mass undergoes gravitational collapse, with most
or all of its mass compressed into a sufficiently
small area of space, causing infinite spacetime
curvature at that point (a "singularity").
Such a massive spacetime curvature allows
nothing, not even light, to escape from the "event
horizon," or border.
Visualizing a Black Hole
…but more importantly, a black hole is a
THEORY !
Visualizing a Black Hole
The difference between a hypothesis and a theory….
 A hypothesis attempts to answer questions by
proposing an explanation that has yet to be
rigorously tested.
 A theory has already undergone extensive testing by
various scientists and is generally accepted as
being an accurate explanation of an
observation.
 This doesn’t mean the theory is correct; only that
current testing has not yet been able to disprove
it, and the evidence appears to support it.
Visualizing a Black Hole
The difference between a hypothesis and a theory….
 A theory will often start out as a hypothesis.
 If it survives testing, it begins to take on the
significance of a theory.
 The next step is to present the findings to the
scientific community for further, independent
testing.
The more a hypothesis is tested and
holds up, the better accepted it
becomes as a theory.
Visualizing a Black Hole
Can we observe a
black hole?
Visualizing a Black Hole
If we can’t observe a black
hole, why are we all buying
into this theory?
What is the biggest obstacle to
proving that black holes really
do exist?
What kinds of evidence are
there that they do exist?
Because of the way gravity bends light around a black hole (rays’
paths shown), the silhouette will appear larger than it really is. The
spinning black hole will look lopsided, with rays on the side
approaching Earth (lighter paths) appearing brightest.
Very Small and Far Away
How is the search for black
holes similar to the quest to
view microscopic objects?
Very Small and Far Away
Everything starts out as a theory….
Cells were just a theory until the invention of
the microscope.
Inventions and technology help up
“push the envelope” and observe
the unobservable!
Ant holding a computer chip
Eye lash hairs growing out of skin