Seminar presentation on Hubble's Law and Expanding Universe

H U B B L E ’ S L A W A N D E X P A N D I N G U N I V E R S E
By
K Gautham Nagi Reddy, B140029EC

U N I V E R S E
All that is present from the tiniest particle
(atom) to huge galaxies is what makes up
the Universe

E D W I N H U B B L E
• Date of Birth : November 20th ,1889.
• Graduated from University of Chicago.
• Lead the research team at Mt. Wilson Observatory.
• Released paper in 1929 on Hubble’s Law.
• Died on September 28th , 1953.

H U B B L E ’ S L A W
 Red Shift of the light coming from distant objects in the Universe is directly proportional to the
distance from Earth
 Was put forward by Hubble in 1929
 Expression
𝑣 = 𝐻0d
Where ,
𝑣 - recession velocity of the celestial body
𝐻0 - Hubble’s Constant
d - Distance between the celestial object and Earth

VELOCITY VS DISTANCE GRAPH
• In the graph show here , the X-axis is the
distance parameter and the Y-axis
indicates the velocity parameter
• From the adjacent from you can notice
that the dots are deviating from the solid
line approximation.
• This graph helps here in the
determination of the Hubble's constant

DATE PUBLISHED HUBBLE CONSTANT OBSERVER WITH METHODOLOGY
16-10-2017 70.0−8.0
+12.0
The LIGO Scientific Collaboration
and the Virgo Collaboration
22-11-2016 71.9−3.0
+2.4 HST with the help of Gravitational
Lensing
13-07-2016 67.6−0.6
+0.7
Baryon Oscillation Spectroscopic
Survey
17-05-2016 73.24±1.74 Hubble Space Telescope using Type
Ia supernova
02-2015 67.74±0.46 Planck mission
01-10-2013 74.4±3.0 Cosmic flows 2 experiment which
used the redshifts and other
methods
2013-03-21 67.80±0.77 Planck Mission
2012-12-20 69.32±0.80 WMAP (9-years)
2010 70.4−1.4
+1.3 WMAP (7-years), combined with
other measurements.
2010 71.0±2.5 WMAP only (7-years).
2009-02 70.1±1.3 WMAP (5-years). combined with
other measurements.
2009-02 71.9−2.7
+2.6
WMAP only (5-years)
2007 70.4−1.6
+1.5 WMAP (3-years)
2006-08 77.6−12.5
+14.9
Chandra X-ray Observatory
2001-05 72±8 Hubble Space Telescope
prior to 1996 50–90 (est.)
early 1970s ~55 (est.) Allan Sandage and Gustav
Tammann
1958 75 (est.) Allan Sandage
1956 180 Humason, Mayall and Sandage, this
was the first good estimate of H0,
but it would be decades before a
consensus was achieved.
1929 500 Edwin Hubble, Hooker telescope
Con stant
mod ification
in th e valu e of
the
Hu b b le’s Con stant

MEASURING 𝐻0 WITH THE HELP OF
GRAVITATIONAL WAVES
 LIGO (Laser Interferometer Gravitational wave Observatory) and Virgo interferometer
 Started in 1997 under the leader ship of Barry Barish an experimental physicist at University of
California and also a Nobel Laureate.
 It is headquartered at both CALTECH and MIT
 The Main aim of both these observatories is to detect the existence of Gravitational waves.
 This mission consists of around 1200 scientists from all over the world and India plays a major in
terms of the number of scientists associated with this mission

G R A V I T A T I O N A L L E N S I N G
When light traveling from a quasar to Earth
passes by a sufficiently massive galaxy, the
galaxy can act as a lens that bends the
quasar light. As a result, Earthbound
astronomers see multiple images of the
quasar as shown in the figure. At times the
brightness of the quasar flickers, and those
fluctuations at the source are observed in
the lensed images too. But since each
image corresponds to a slightly different
path length from quasar to telescope, the
flickers appear at slightly different times for
each image. The H0LiCOW team carefully
measured those time delays, which are
inversely proportional to H0.

TYPE -IA SUPER NOVA
• Type Ia Super nova is a binary system
consisting of two stars revolving
around each other here the
observation was done in terms of
lower order of redshift where z<0.5
• This experiment just increased the
precision of the previous measured
H0 value which was determined using
the redshifts

PLANCK MISSION
• Planck’s mission was a European
led mission to get a clearer image
of the Cosmic Microwave
Background (CMB). This image
gives us the idea of the
temperature variation of the
universe and distribution of heat
after the Big Bang.
• Similar images were taken earlier
by the WMAP and COBE satellites
but were not as sharp as the one
taken by Planck Satellite.
• They had revised many
astronomical constants as well and
recalculated the value of Hubble’s
parameter too.

W M A P
• Wilkinson Microwave
Anisotropy Probe (WMAP), a
U.S. satellite launched in 2001
that mapped irregularities in
the cosmic microwave
background (CMB).It retired
on 2012 .
• It made significant
contributions in the
calculation of the Hubble’s
parameter from 2007 to 2012.

APPLICATION OF THE HUBBLE PARAMETER
 Hubble time (𝒕 𝑯): The Hubble constant (𝐻0) has units of inverse time; the Hubble time (𝑡 𝐻) is
simply defined as the inverse of the Hubble constant.
𝑡 𝐻 =
1
𝐻0
=
1
70(
𝑘𝑚
𝑠
)/𝑀𝑝𝑐
= 14.2 𝑏𝑖𝑙𝑙𝑖𝑜𝑛 𝑦𝑒𝑎𝑟𝑠 ≈ 13.8 𝑏𝑖𝑙𝑙𝑖𝑜𝑛 𝑦𝑒𝑎𝑟𝑠
 The difference is because the Hubble time is the age it would have had if the expansion had been
linear, and it is different from the real age of the universe because the expansion isn't linear.
 The Hubble length or Hubble distance: It is a unit of distance in cosmology, defined as
𝑐
𝐻0
= 𝑐 ∗ 𝑡 𝐻
The speed of light multiplied by the Hubble time. It is equivalent to 4,550 million parsecs or 14.8 billion
light years.
 Hubble volume: It is defined as the volume of the Universe with a comoving size of 𝑐/𝐻0. Some
Cosmologists refer to the size of the observable Universe as the Hubble’s Volume, although it has a
radius which is 3 times larger than this value.

 The term Big bang was first coined by an English Astronomer Sir Fred Hoyle. Much after
Lemaitre noted in 1927 that an expanding Universe could be traced back to in time to an
originating single point called singularity.
 There was constant controversies between the big bang theory and the steady state theory .
After the discovery made by Hubble in 1929 about the expanding Universe.
 In 1964, the cosmic microwave background radiation was discovered, which was crucial
evidence in favour of the Big Bang model.
 More recently, measurements of the redshifts of supernovae indicate that the expansion of
the universe is accelerating, an observation attributed to dark energy's existence.
B I G B A N G T H E O R Y

R E D S H I F T
 It is phenomenon where the light is shifted to the longer wavelengths which indicates that
they travel longer distances than their usual distances, hence we can determine their distance
from Earth.
 Observations of distant galaxies and quasars show that these objects are redshifted—
the light emitted from them has been shifted to longer wavelengths.

C O S M I C M I C R O S C O P I C B A C K G R O U N D
R A D I A T I O N
 Ralph and Alpher and Robert Herman discovered this radiation in 1948 using the Horn
Antenna and estimated the temperature of the universe to be 28K.
 In 1964 , Anno Penzias and Woodrow Wilson of Bell Labs determined the temperature o the
universe to be 4.2K. They had won Nobel prize for this in 1978
 The next big step of the evolution of the CMB radiation image was the NASA COBE mission
and it measured the temperature of the universe to 2.726K in 1992.

GRAVITY AND THE EXPANDING UNIVERSE
 As expansion takes place, the attractive force diminishes (as matter gets distributed as the fabric of
space keeps on expanding) and as there is no effect on the dark energy it keeps on increasing which
ultimately results in the acceleration in the rate of expansion.
 So now lets see what is responsible for this attractive forces:
 Matter: Matter is everything that is around us. It is also called Baryonic matter and it is made up of
electrons and protons. Surprisingly this matter accounts for only 5% of the Universe.
 There are two types of known matter:
 Normal matter
 Anti matter
 Dark matter : This is the type of matter which we have no information about because it does not
interact electromagnetically. There are assumed to be three types of dark matter which are:
 Cold Dark matter
 Warm Dark matter
 Hot dark matter
 Dark matter accounts for 27% of the Universe.

• Dark Energy : Dark Energy makes up almost 68% of the Universe, even though it doesn’t have any attractive
forces related to it, it is responsible for the repulsion effect called anti gravity.
• Gravity : The attractive force through which all the matter attract each other is called gravity. It is responsible for
the formation of matter and without this force, all the matter would have been long ago torn apart. One more
interesting point abut gravity is that it is due to all the dark matter which is present in the Universe is
responsible for the huge amount of attraction between large celestial bodies.

F A T E O F T H E U N I V E R S E
 Density parameter: It is the average matter density of the universe divided by a critical value
of that density.
 Closed Universe: In a closed Universe, gravity usually stops and begins to shirk until all the
matter in the universe collapses to a point.(singularity).
 Open Universe: In an open universe, the Universe keeps on expanding because the dark
energy plays a major role and this expansion rate also keeps on increasing in an accelerated
manner.
 Flat universe: In this kind of expansion takes place but this effect is slowly fading and
eventually becomes zero and the expansion stops because the gravity (pull) and anti
gravity(push) balance each other .

B I G F R E E Z E
 If the expansion of the universe continues at the steady rate as it is doing at
present, then, the Universe will eventually cool as it expands, finally becoming
too cold to sustain life.

L E T ’ S D I S C U S S
 Why is that we at Earth don’t witness the expansion of the Universe?
 Why is that astronomers say that The Andromeda and The Milky Way Galaxies are on
a collision course when we say that the Universe is Expanding at an accelerated
manner?
 * You can also post answers to these questions on Quora too.

Seminar presentation on Hubble's Law and Expanding Universe

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