| Date | May 2016 | Marks available | 2 | Reference code | 16M.3.HL.TZ0.21 |
| Level | Higher level | Paper | Paper 3 | Time zone | Time zone 0 |
| Command term | Explain | Question number | 21 | Adapted from | N/A |
Question
The Hot Big Bang model suggests several outcomes for the universe. There is now evidence that dark energy and dark matter exist.
On the axes, sketch a graph of the variation of cosmic scale factor with time for
(i) a closed universe without dark energy. Label this curve C.
(ii) an accelerating universe with dark energy. Label this curve A.
Explain one experimental observation that supports the presence of dark matter.
Markscheme
(i) curve beginning on R=0 before present time and ending after present time on R=0
(ii) curve starting earlier than C with general shape shown above
coincides with curve C at present time
Judge by eye.
rotation speeds of galaxies is greater at the edges than expected
so the density at the edges must be greater than that supplied by luminous matter alone
Accept any other valid piece of evidence, eg gravitational lensing, which provides a good measure of galactic cluster masses.
