Download What is the Universe made of?

The
latest
experimental
evidence suggests that the
universe is made up of just 4%
ordinary matter, 23% cold dark
matter and 73% dark energy.
These values were obtained by
fitting data from measurements
of the Cosmic Microwave
Background radiation to models
of our universe.
Dark matter is matter we cannot see
directly when we observe the
Universe. It could be made up of one
of many different things: cold baryonic
matter that cannot be seen by our
telescopes, exotic particles called
WIMPS which react only weakly with
matter, and so are so are difficult to
detect, or super-massive black holes
at the centres of distant galaxies…..
Ordinary Matter is what stars, planets
and
people are made from. All
matter is made up of combinations of
6 quarks, 6 leptons and their
antiparticles. Particles such as the
electron and neutrino are known as
leptons. Particles such as the proton
and neutron are made of three
quarks, and are called baryons.
Scientists often refer to ordinary
matter as baryonic matter.
-
Dark Matter Candidates
+
A Brown Dwarf. A ball
of gas too small to
ignite fusion reactions
and become a star. The
spot at the image
centre is believed to be
a brown dwarf.
The exact amount of dark matter
could determine the ultimate fate of
our Universe - will it collapse or will it
expand forever?
MACHOS
WIMPS
Massive Compact Halo Objects
Weakly Interacting
Massive Particles
White Dwarf stars.
The remains of dead
low mass stars are
circled in this image
made
with
the
Hubble
Space
Telescope.
Neutron
Star.
The remains of
a massive, dead
star. This image
is of the Crab
Pulsar a rapidly
rotating neutron
star.
Massive compact object
Dark Matter Detectors
Dark Energy is still a great mystery
to scientists. One possibility for this
additional energy is “quintessence”,
a fifth fundamental force to go with
gravity, the two nuclear forces and
the electromagnetic force. This fifth
force could be responsible for
accelerating the rate of expansion
of the Universe. Einstein was the
first to introduce such a force when
he added a term called the
cosmological constant, l, to his
theory of general relativity. He later
removed it, calling it his “greatest
mistake”. Recently, it has been reintroduced by scientists trying to
explain their observations of the
Universe.
A Black Hole can be
formed when massive
stars collapse. Supermassive black holes,
millions of times more
massive, are believed
to reside in most
galaxies.
A WIMP is a particle
many
times
more
massive than a proton
that
only
interacts
weakly so is very hard to
detect. They could make
up as much as 99% of
dark matter.
Neutrinos
Neutrinos are like
electrons,
however
they have no charge.
Long believed to be
mass-less,
recent
experiments
have
suggested that they
may in fact have a
tiny mass.
Observer
Background object
When light passes by a massive object its path is bent. If a massive object lies
between us and a distant source, the light rays from the source may be focused
changing the appearance of the source. This effect is known as gravitational
lensing. When the massive object is something quite small, such as a brown
dwarf, the effect is known as gravitational micro-lensing. By observing many
stars over a period of time to see how their appearance changes, scientists
hope to detect the presence of massive objects lying between the Earth and
the stars – objects that could not normally be detected.
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Instruments such as the CDMS
(Cryogenic Dark Matter Search)
are being used to search for
WIMPS. The detectors have to be
carefully shielded from other
sources of radiation, and are often
built at the bottom of deep mines.
Super-Kamiokande
detects radiation from
neutrinos that move
faster than the speed
of light, using an
effect analogous to
the sonic boom from
fast aircraft