Dark matter and dark energy make up 95% of the universe. Dark matter is an undetected form of matter that exerts gravitational pull but does not emit or interact with light. Its existence is inferred from its gravitational effects, such as the rotation speeds of galaxies. Dark energy is driving the accelerating expansion of the universe according to Hubble's law, contradicting the expected eventual gravitational collapse. While their effects can be observed, the true nature of dark matter and dark energy remain mysterious, as they have not been directly detected, and may hold potential future applications in spacecraft propulsion if their properties can be better understood.
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Dark matter & dark energy
1. Dark matter & Dark Energys
Submitted By :
D.Surat
M.Sc. Physics
Dayalbagh Educational Institute
2. Mysteries of the cosmos:
Nature and Role of Dark
Matter & Dark Energy
3. What is Dark Matter and Dark Energy ?
In our universe, we are chasing several mysteries
one of them is the 95% of the invisible mass. The
total part of the universe that we can observe only
accounts for 5%, rest 25% is dark matter and 70% is
dark energy.
Dark Matter: An undetected form of mass that
emits no light or no photons, but we know it must
exist because we observe the effects of its gravity.
Dark Energy: An unknown form of energy that is
causing the universe to expand faster over time.
5. What is dark matter ?
Dark Matter is a kind of hidden matter which acts like
a Gravitational pull to our universe.
Dark meaning that it is not in the form of stars or
planets we see. But it is something different from it.
Although Dark Matter is not directly observed yet but
its gravitational pull is experienced such as rotation
of galaxies, gravitational lensing, cosmic microwave
background radiation and so on.
6. Rotation of galaxies
Galaxies are collections of billions of stars. Most of
the light from a galaxy comes from its center. This
indicated that most of the galaxies stars and most of
its mass is concentrated at its center.
If gravity causes galaxies to rotate, as we assume it
does, then outer stars should behave much like the
planets of our solar system. Inner planets rotate
faster and outer planets rotate slower. This is called
Keplerian motion. In galaxies, however, both inner
and outer stars rotate at about the same speed.
7. In order for gravity to cause this type of rotation,
each galaxy must be surrounded by a super-
massive halo of matter. No such halos, however,
can be seen. So we conclude that they are made of
dark matter.
8. What is Dark Energy ?
According to Stephen hawking big bang should be
followed by a big crunch but according to Hubble's
law the more distant are the celestial objects faster
are they moving away from us.
Which is contradiction to Stephen hawking’s
statement. Which brings in an unknown kind of
repulsive force believed to be dark energy.
9. The only thing we
know about it is that it
is a kind of repulsive
force which causes the
expansion of universe.
It might be a
gravitational pull of
some other universe or
something else we
don’t know what it is,
so we believe it to be
dark energy.
10. Why are we interested in both ?
1. 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.
2. Knowing properties of dark matter and dark energy we
may predict actual shape and size of the universe.
11. At the end…
All of these points discussed in this presentation are
the indirect evidences of Dark Matter and Dark
Energy. We still Don't Know what they really are.
They will always remain a mystery to us until we find
the strong foundation for their existence.