| Date | May 2015 | Marks available | 3 | Reference code | 15M.3.SL.TZ1.16 |
| Level | Standard level | Paper | Paper 3 | Time zone | Time zone 1 |
| Command term | Explain | Question number | 16 | Adapted from | N/A |
Question
This question is about the development of the universe.
The graph shows one possible way in which the universe is thought to change with time. This type of universe is known as a fl at universe.
On the graph, draw lines to show the variation with time of the size of the universe for both a closed universe and an open universe. Label your line for the closed universe C and your line for the open universe O.
Explain how the open and closed outcomes for the universe depend on the critical density of matter in the universe.
State one reason why it is difficult to determine the density of the universe.
Markscheme
after present, open universe curve drawn above flat curve and closed universe curve drawn under flat curve; (both needed for mark)
all meet at “present time”;
Ignore curves before present time.
if density less than critical density/too low the universe will expand forever;
if greater than critical density the universe contracts;
after an initial expansion;
If critical density not mentioned award [1 max].
presence of dark matter / WIMPS / MACHOS etc;
