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Description
Mind Map by Connor O'Hare, updated more than 1 year ago
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Created by Connor O'Hare
over 6 years ago
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Chapter 20- Cosmology
- Measurements
- Astronomical unit (AU)
- "The average distance from the Earth
to the Sun"
- 1.5*10^11m
- "The average distance from the Earth
to the Sun"
- The light-year (ly)
- "The light- year is the distance
travelled by light in a vacuum in a
time of one year
- 9.46*10^15m
- Speed of light * Seconds in a year
- Speed of light * Seconds in a year
- "The light- year is the distance
travelled by light in a vacuum in a
time of one year
- The parsec (pc)
- "The parsec is defined as the distance at
which a radius of 1 AU subtends an angle
of 1 arcsecond"
- 1 arcsecond=(1/3600)°
- 1 arcsecond=(1/3600)°
- 3.1*10^16m
- "The parsec is defined as the distance at
which a radius of 1 AU subtends an angle
of 1 arcsecond"
- Astronomical unit (AU)
- Stellar parallax
- This is the apparent shift of position of any nearby
star against the background of distant objects
- Distance to star=1/parallax angle
- Distance is in parsecs
- Angle in archseconds
- Distance is in parsecs
- This is the apparent shift of position of any nearby
star against the background of distant objects
- The Dopler shift
- Whenever a wave source
moves relative to an observer,
the frequency & wavelength of
the waves recieved by the
observer change
- Waves in front of source are compressed
- Waves behind source are stretched
- Waves in front of source are compressed
- If galaxy is moving towards
Earth=Absoprtion lines will be
blue-shifted because wavelengths
appear shorter
- If galaxy is moving away
from Earth=Absorption
lines will be red-shifted
because wavelengths
appear stretched
- Whenever a wave source
moves relative to an observer,
the frequency & wavelength of
the waves recieved by the
observer change
- Hubble's law
- 1) Light from the vast majority of galaxies was red-shifted (They had a relative
velocity away from the Earth)
- 2) In general the further away the galaxy was the greater the
observed red-shift and so the faster the galaxy was moving
- This shows that recessional speed
is proportional to the distance
from us
- Hubble's law is key evidence for the
Big Bang theory
- Since light from nearly all the
galaxies is red-shifted it states
the fabric of space is
expanding in all directions
- Since light from nearly all the
galaxies is red-shifted it states
the fabric of space is
expanding in all directions
- 1) Light from the vast majority of galaxies was red-shifted (They had a relative
velocity away from the Earth)
- The cosmological principle assumes that- "When viewed on a large enough scale, the
Universe is homogeneous and isotropic, and the laws of physics are universal
- The Big Bang theory
- There are 2 main pieces of
evidence for the Big Bang
theory
- 1) Hubble's law
- Shows the Universe is expanding in all dimensions- hence the expansion could be
traced back to a single, denser and hotter point
- Shows the Universe is expanding in all dimensions- hence the expansion could be
traced back to a single, denser and hotter point
- 2) Microwave background radiation
- The Big Bang model predicts that
loads of gamma radiation was
produced in the hot early universe
and should still be observed today
- Due to the Universe expanding, the wavelengths of the
Cosmic radiation are now in the microwave region
- Due to the Universe expanding, the wavelengths of the
Cosmic radiation are now in the microwave region
- The Big Bang model predicts that
loads of gamma radiation was
produced in the hot early universe
and should still be observed today
- 1) Hubble's law
- Age of the Universe ≈ 1/Hubble's constant
- The Universe is roughly 14 billion years old
- The Universe is roughly 14 billion years old
- There are 2 main pieces of
evidence for the Big Bang
theory
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