Dark matter is an invisible form of matter inferred from its gravitational effects on visible matter, comprising approximately 26.8% of the universe's total mass. Historical theories have speculated on its composition, with evidence suggesting that most dark matter is nonbaryonic, with candidates like axions and supersymmetric particles. Current understanding indicates that baryonic matter constitutes only about 4-5% of the universe, while detailed analyses show that a significant portion of dark matter does not interact with ordinary matter or photons.

1. DARK MATTER
BY : Zoe Schiaffino and Silvia Candeira

2. DARK MATTER (IMAGES)

3. INTRODUCTION
• . It is a kind of matter in astronomy and cosmology to
account for gravitational effects that appear to be the
result of invisible mass.
mass
• Dark matter cannot be seen directly with telescopes;
evidently it neither emits nor absorbs light or other
electromagnetic radiación at any significant level.
• The existence and properties of dark matter are
inferred from its gravitational effects on visible matter
radiation, and the large-scale structure of the universe

4. • TODAY
• Atoms 4.9%
• Dark matter 26.8%
• Dark energy 68.3%
• 13.7 BILLION YEARS AGO
• Neutrinos 10%
• Photons 15%
• Atoms 12%
• Dark matter 63%

5. HISTORY SEARCH OF ITS COMPONENTS
• Although dark matter had historically been inferred by many
astronomical observations, its composition long remained speculative.
• Early theories of dark matter concentrated on hidden heavy normal
objectsas the possible candidates for dark matter, collectively known
as massive compact..
• Cold dark matter – objects with a free-streaming length much smaller
than a protogalaxy.
• Warm dark matter – particles with a free-streaming length similar to a
protogalaxy.
• Hot dark matter – particles with a free-streaming length much larger
than a protogalaxy.

6. BARYONIC DARK MATTER
There are three separate lines of evidence that the majority of dark matter is not
made of baryons:
-The theory of Big Bang nucleosynthesis, which very accurately predicts the
observed abundance of the chemical elements predicts that baryonic matter
accounts for around 4–5 percent of the critical density of the Universe.
- Large astronomical searches for gravitational microslensing, including the
MACHO, EROS and OGLE projects, have shown that only a small fraction of the
dark matter in the Milky Way can be hiding in dark compact objects
- Detailed analysis of the small irregularities (anisotropies) in the cosmic microwave
background observed by WMAP and Planck shows that around five-sixths of the
total matter is in a form which does not interact significantly with ordinary matter or
photons.

7. NONBARYONIC DARK MATTER
• Candidates for nonbaryonic dark matter are
hypothetical particles such as axions,
or supersymmetric particles; neutrinos can only form a
small fraction of the dark matter, due to limits
from large-scale structure and high-redshift galaxies.
Unlike baryonic dark matter, nonbaryonic dark matter
does not contribute to the formation of the elements in
the early universe and so its presence is revealed only
via its gravitational attraction