Transcript Dark Matter and Dark Energy

Dark Matter and Dark Energy
Most of the universe is dark matter
and dark energy.
• Most of the mass-energy, about 95%, in the
universe is ‘dark’. By dark we mean that it
does not emit any form of electromagnetic
radiation.
• Dark energy and dark matter have not been
directly observed but they have been inferred
from observations of a wide variety of
phenomena. There existence is vital to the Big
Bang Theory.
Total Mass/Density of the Universe
Dark Energy makes up
72% of the total massenergy density of the
universe. The other
dominant contributor is
Dark Matter, and a
small amount is due
to atoms or baryonic
matter.
Dark Matter
• The existence of dark matter is inferred indirectly
by its gravitational effect.
• Inference from observations of
– the motions of stars and gas in galaxies, cluster
galaxy radial velocities, hot gas properties of clusters,
and gravitational lensing of distant, background
galaxies by foreground galaxy clusters all suggest large
amounts of Dark Matter exist.
– Radial velocity is the velocity of a star or other body
along the line of sight of an observer.
Dark Matter
– Gravitational lensing - A gravitational lens refers to
a distribution of matter between a distant source
and an observer; which is capable of bending the
light from the source, as it travels towards the
observer.
Dark Energy
• Dark Energy is a hypothetical form of energy
that exerts a negative, repulsive pressure,
behaving like the opposite of gravity.
– Without dark energy, astronomers would not be
able to explain why the galaxy is still increasing in
size, in fact its expansion is accelerating, when
gravity should make it contract.
Dark Energy
• Like Dark Matter, Dark Energy is not directly
observed, but rather inferred from
observations of gravitational interactions
between astronomical objects.
Big Bang Nucleosynthesis
• Big Bang Nucleosynthesis (abbreviated BBN) refers to the production of nuclei other than
those of the lightest isotope of hydrogen
during the early phases of the universe.
• http://astro.berkeley.edu/~mwhite/darkmatte
r/bbn.html
Big Bang Nucleosynthesis
• The Universe's light-element abundance is another
important criterion by which the Big Bang hypothesis is
verified.
• It is now known that the elements observed in the
Universe were created in either one of two ways.
– Light elements (namely deuterium, helium, and lithium)
were produced in the first few minutes of the Big Bang.
– Elements heavier than helium are thought to have their
origins in the interiors of stars which formed much later in
the history of the Universe.
– Both theory and observation lead astronomers to believe
this to be the case.