In astronomy, dark matter is a hypothetical form of matter that appears not to interact with light or the electromagnetic field. Dark matter is implied by gravitational effects which cannot be explained by general relativity unless more matter is present than can be seen.
2. INDEX
• Introduction
• Composition of Cosmos
• What we know
• How do we know it exists?
• Various theories
• Classification
• Why are we interested in that?
• Difference between Dark matter and Dark Energy
• Summary
8. WHAT WE KNOW
THERE IS SOMETHING
INTERACTS WITH GRAVITY
THERE IS A LOT OF IT
9. WHAT WE KNOW
• Dark matter is massive and dark.
• It is collision less.(passes through itself and other matter)
• It does not emit or interact with electromagnetic radiation.
• It has not been directly observed, but its existence
is deduced from its gravitational effects .
• Dark matter is not "anti-matter".
13. OBSERVATIONAL EVIDENCE
• Observations of the rotational speed of spiral galaxies.
• The confinement of hot gas in galaxies and clusters of
galaxies.
• The random motion of galaxies in clusters.
• The observed fluctuation in the cosmic microwave
background radiation.
• Observation shows that kinetic energy is large compared to
the corresponding mass. …. MISSING MASS
15. CLASSIFICATION
• Dark matter candidates are usually categorized as:
• Baryonic
• Non-Baryonic :
• Hot Dark Matter (HDM)
• Cold Dark Matter(CDM)
• Other forms of dark matter can be MACHOs, WIMPs, SuperPartner Particles
and Axions.
16. TOP CONDIDATES FOR DARK
MATTER
• MACHOs (Massive Compact Halo
Objects).
• WIMPs(Weakly Interecting Massive
Particles.)
• Axions
• SuperPartner Particles
• Neutrinos
• MOND
18. DARK ENERGY
• As same as the Dark matter, dark energy has been one of the most
mysterious issues its exists in science.
• Dark Energy is the hypothetical form of energy that permeates all of
space and produces a negative pressure, resulting in the repulsive
gravitational force.
• It is responsible for continuous expansion of universe.
• Two possible forms of Dark energy are the cosmological constant and
quintessance, the first static and other dynamic.
19. WHERE IS THE DIFFERENCE
• Dark matter is the form of matter
explaining the gravitational effects while
dark energy is the field that fills all space.
• Dark matter assembles the larger
structures of our universe, dark energy
keeps the universe expanding.
• Dark matter and dark energy are the yin
and yang of the cosmos. Dark matter
produces an attractive force (gravity),
while dark energy produces a repulsive
force (antigravity)
20. WHY ARE WE INTERESTED IN BOTH
• In future it might be possible that we might build such space crafts which
could use the power from Dark matter or Dark energy which will make them
very fuel efficient as well as very fast.
• We can predict the size and shape of the universe.
• Because we don't know what it is.
• People are interested in working on one of today’s boundaries, which, right
now, is dark matter.
• Without Dark matter, we are uniable to explain why galaxies are stable.
21. SUMMARY
• Astrophysical observations tell us that we live in a dark-dominated universe.
• All the points discussed in this presentation are the indirect evidences of the
dark matter. We still don't know what they really are.
• To explain the previous phenomenon ,theories challeging Newtonian
Mechanics and Einstein's theory of relativity have been proposed. But none
of these were successful in explaining all.
• Eg. M O N D (Modified Newtonian Dynamics)
Concept of Dark matter is still a mystery
