The Big Bang Model - Chapter 12
- Created by: CatherineMcGurk
- Created on: 11-08-15 22:18
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- The Big Bang Model of the Universe
- Hubble's Ideas
- Recessional Velocity is Proportional to Distance
- The spectra from galaxies all show redshift.
- The amount of redshift gives the recessional velocity.
- HUBBLES LAW: v=H0d where v = recessional velocity, H0 = Hubble's Constant, d = distance
- UNITS: v = km/s d = Mpc H0 = (km/s) / (Mpc)
- Mpc is a megaparsec. 1Mpc = 3.09E+22m
- SI Unit for H0 is 1/s therefore... v = m/s d=m
- UNITS: v = km/s d = Mpc H0 = (km/s) / (Mpc)
- When Hubble plotted the recessional velocity of galaxies against their distance from Earth (Cepheid Variables) he found that they were proportional.
- The spectra from galaxies all show redshift.
- The Universe is Expanding
- By showing that objects in the Universe are moving away from each other, Hubble's work is strong evidence that the Universe is expanding.
- The rate of expansion depends on the value of H0.
- The way cosmologists tend to look at this, the galaxies aren't actually moving through space away from us.
- Instead, space itself is expanding and light waves are being stretched along with it.
- This is called cosmological redshift to distinguish it from redshift produced by sources that are moving through space.
- Instead, space itself is expanding and light waves are being stretched along with it.
- The Universe is expanding uniformly away from us, creating the illusion that we are at the centre of the universe.
- By showing that objects in the Universe are moving away from each other, Hubble's work is strong evidence that the Universe is expanding.
- The Age and Observable Size of the Universe depend on H0.
- If the Universe has been expanding at the same rate for its whole life, the age of the Universe is t = 1/H0
- This is only an estimate as it is unlikely that the universe has been expanding at the same rate.
- Since no on know the exact value of H0, we can only guess the universe's age.
- Approx. 14 billion years old.
- The absolute size of the Universe is unknown. There is a limit on the observable size of the Universe.
- This is a sphere, where radius = maximum distance that light can travel during its age (radius approx. 14 billion light years).
- If the Universe has been expanding at the same rate for its whole life, the age of the Universe is t = 1/H0
- Evidence: The Red Shift of Galaxies
- If you assume that the Universe has always been expanding, if you trace back far enough it can be implied that the universe must once have been contained in a single point.
- Recessional Velocity is Proportional to Distance
- Evidence: Cosmic Microwave Background Radiation
- Properties of the Cosmic Microwave Background Radiation
- Cosmic Background Explorer set up to look at spectrum.
- Continuous spectrum corresponding to a temperature of 2.73k
- Radiation is ISOTROPIC AND HOMOGENOUS - same intensity whichever direction you look at it
- Very tiny fluctuations in temperature, at the limit of COBE detection.
- Due to tiny energy density variations in the early universe and are needed for the initial seeding of galaxy formation.
- Also shows a Doppler Shift
- Milky Way is rushing towards an unknown mass (GREAT ATTRACTOR) at over a million miles per hour.
- Cosmic Background Explorer set up to look at spectrum.
- Penzias and Wilson, 1960's
- HBBM predicts that EM radiation was produced in the very early Universe. This radiation should still be observed today.
- Because the Universe has expanded,, the wavelengths have been stretched and are in the microwave region.
- Properties of the Cosmic Microwave Background Radiation
- The HBB (HOT BIG BANG MODEL)
- The Universe started off very hot and very dense (perhaps as an infinitely hot, infinitely dense singularity)and has been expanded.
- Widely accepted
- Since Hubble's findings were published,the redshifts of other objects have been measured and fit with his predictions.
- Evidence: the amount of Helium in the Universe
- The HBB Model also explains the large amount of helium in the Universe.
- The early Universe had to have been very hot and at some point it must have been hot enough for hydrogen fusion to occur.
- This means that, together with the theory of the synthesis of heavier elements in stars, the relative abundances of all of the elements can be accounted for.
- Hubble's Ideas
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