DP Physics Questionbank

Description

Nature of science:

Cognitive bias: According to everybody’s expectations the rate of expansion of the universe should be slowing down because of gravity. The detailed results from the 1998 (and subsequent) observations on distant supernovae showed that the opposite was in fact true. The accelerated expansion of the universe, whereas experimentally verified, is still an unexplained phenomenon. (3.5)

Understandings:

• The cosmological principle
• Rotation curves and the mass of galaxies
• Dark matter
• Fluctuations in the CMB
• The cosmological origin of redshift
• Critical density
• Dark energy

Applications and skills:

• Describing the cosmological principle and its role in models of the universe
• Describing rotation curves as evidence for dark matter
• Deriving rotational velocity from Newtonian gravitation
• Describing and interpreting the observed anisotropies in the CMB
• Deriving critical density from Newtonian gravitation
• Sketching and interpreting graphs showing the variation of the cosmic scale factor with time
• Describing qualitatively the cosmic scale factor in models with and without dark energy

Guidance:

• Students are expected to be able to refer to rotation curves as evidence for dark matter and must be aware of types of candidates for dark matter
• Students must be familiar with the main results of COBE, WMAP and the Planck space observatory
• Students are expected to demonstrate that the temperature of the universe varies with the cosmic scale factor as 

Data booklet reference:

International-mindedness:

• This is a highly collaborative field of research involving scientists from all over the world

Theory of knowledge:

• Experimental facts show that the expansion of the universe is accelerating yet no one understands why. Is this an example of something that we will never know?

Aims:

• Aim 2: unlike how it was just a few decades ago, the field of cosmology has now developed so much that cosmology has become a very exact science on the same level as the rest of physics
• Aim 10: it is quite extraordinary that to settle the issue of the fate of the universe, cosmology, the physics of the very large, required the help of particle physics, the physics of the very small

Directly related questions

• 18M.3.HL.TZ2.19b: Outline why a hypothesis of dark energy has been developed.
• 18M.3.HL.TZ2.19a: Explain the evidence that indicates the location of dark matter in galaxies.
• 18M.3.HL.TZ1.19c: Explain, using the equation in (a) and the graphs, why the presence of visible matter alone...
• 18M.3.HL.TZ1.19b: Draw on the axes the observed variation with r of the orbital speed v of stars in a galaxy.
• 18M.3.HL.TZ1.19a: The mass of visible matter in the galaxy is M. Show that for stars where r > R0 the velocity...
• 17N.3.HL.TZ0.20c: Show that the critical density of the universe is \[\frac{{3{H^2}}}{{8\pi G}}\] where H is the...
• 17N.3.HL.TZ0.20b: Suggest how fluctuations in the cosmic microwave background (CMB) radiation are linked to the...
• 17M.3.HL.TZ2.20c: Curve A shows the actual rotation curve of a nearby galaxy. Curve B shows the predicted rotation...
• 17M.3.HL.TZ2.20b: The distribution of mass in a spherical system is such that the density ρ varies with distance...
• 17M.3.HL.TZ2.20a: Describe what is meant by dark matter.
• 17M.3.HL.TZ2.19b: State how the anisotropies in the CMB distribution are interpreted.
• 17M.3.HL.TZ2.19a.ii: The present temperature of the CMB is 2.8 K. This radiation was emitted when the universe was...
• 17M.3.HL.TZ2.19a.i: Derive, using the concept of the cosmological origin of redshift, the relation T...
• 17M.3.HL.TZ1.17b.ii: The density of dark energy is ρΛc2 where ρΛ = ρc – ρm. Calculate the amount of dark energy in 1...
• 17M.3.HL.TZ1.17b.i: The density of the observable matter in the universe is only 0.05 ρc. Suggest how the remaining...
• 17M.3.HL.TZ1.17a: The graph shows the variation with time t of the cosmic scale factor R in the flat model of the...
• 16N.3.HL.TZ0.25b: Explain why the rotation curves are evidence for the existence of dark matter.
• 16N.3.HL.TZ0.25a: Calculate the rotation velocity of stars 4.0 kpc from the centre of the galaxy. The average...
• 16M.3.HL.TZ0.21b: Explain one experimental observation that supports the presence of dark matter.
• 16M.3.HL.TZ0.21a: On the axes, sketch a graph of the variation of cosmic scale factor with time for (i) a closed...
• 15M.3.SL.TZ1.16c: State one reason why it is difficult to determine the density of the universe.
• 15M.3.SL.TZ1.16b: Explain how the open and closed outcomes for the universe depend on the critical density of...
• 11M.3.SL.TZ2.15b: Suggest one reason why it is difficult to estimate the density of matter in the universe.
• 11M.3.SL.TZ2.15a: Explain, with reference to the possible fate of the universe, the significance of the critical...
• 11N.3.SL.TZ0.12b: The future development of the universe is determined by the relationship between the apparent...
• 12M.3.SL.TZ2.14b: The diagram represents how the universe might develop if its density were greater than the...
• 12N.3.SL.TZ0.16a: Theoretical studies indicate that the universe may be open, closed or flat. (i) State, by...
• 12M.3.SL.TZ2.14a: Define, with reference to the flat model of the universe, critical density.