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Questions to Consider (1)
• Why is it interesting to study the structure of
the whole universe? How would you explain
that interest to someone else?
• Should it be surprising that cosmology, the
study of the very largest things, is intimately
connected to particle physics, the study of the
• Cosmologists believe that most of the universe
is made of substances utterly different than the
atoms and particles with which we are familiar.
How do you feel about that? Again, should we
Questions to Consider astronomer, looking
1. Imagine that you are an ancient (2)
at the night sky without any instruments. How would
you estimate the distance to the planets and stars?
1. Think about how analogies and metaphors are useful
or misleading when it comes to the whole universe.
Can you think of any good analogies?
3. How does the cosmological principle compare to
Copernicus’s original insight that the earth is not at the
center of the solar system? Can you speculate this
Copernican philosophy to other questions?
Space, Time and Gravity (3)
(Absolute space and absolute
(spacetime is the force of gravity)
Questions to Consider (3)
• What does it mean for two distant events, to
happen at the same time? Is this a concept that we
can really afford to do away with?
• Imagine a careful experiment showing that two
objects fell at slightly different rates in a
gravitational field. How would you interpret that
• Einstein was a popular icon, as well as a leading
scientist. Do you think that he deserved his special
status in the popular imagination?
4 - Cosmology in Einstein’s Universe
(E = m c2 )
Dark energy is expanding the Universe
, ) (
(K (p ) H) (
Friedmann (8 pi G / 3) p = H2 + K •
4 – Questions to Consider
• Is there a difference between light being red
shifted by the Doppler effect or by expansion of
space? Can you think of examples to illustrate
whether such a difference really exists?
• Adding up the angles inside a triangle is one way
to measure the curvature of space. Can you think
• How would you test the Friedmann equation
5 - Questions to Consider
• How could we, in principle at least, be sure that
dark matter cannot possibly be ordinary matter that
is simply not visible for some reason.
• It is possible to prove that dark matter exists, at
least beyond any reasonable doubt?
• Can you think of hypothetical examples where we
could detect dark matter or at least infer its
existence without observing it directly? Do you
always need to see something to know that it is
6 – Gravitational Lensing
• Questions to Consider
• Ordinary lenses can be convex or concaved.
What would be the analogous property of
gravitational lenses? What would that imply
about the matter that was creating gravitational
7 – Atoms and Particles
“ NUCLEUNS ”
UP-QUARKS and DOWN-QUARKS