Download Big Bang and Steady State Theories

Big Bang and Steady State Theories - Past exam questions (6 mark)
(1) * Scientists believe that the Universe is expanding.
Describe how careful observation of electromagnetic radiation from distant galaxies as well as
from the whole of space gave evidence supporting the Big Bang Theory.
(6)
(2) *b While the origin of stars is well understood, there is still much debate about the origin of
the Universe.
Two major theories about the origin of the Universe are the Big Bang and the Steady State
theories.
Some evidence supports both theories. Other evidence supports only one theory.
By considering the evidence, discuss why one of these theories is preferred by most scientists.
(6)
Examiner comments
(1)
Full marks could be obtained by a clear description of the observation of red-shift of light from
galaxies together with either an appreciation of its significance in terms of an expanding universe
or some detail about the process. This should lead to a brief description about how this
supported the Big Bang theory. This should then be coupled with an understanding of the
significance of another observation; cosmic microwave background radiation.
Candidates were not asked to describe the Big Bang or Steady State theories in detail and many
candidates devoted a large part of their answer in doing so. Some candidates used much of the
available response area by effectively writing out the question again.
Some common inaccuracies were to write about planets expanding or moving away and galaxies
being “red-shifted” (rather than the light from those galaxies). Nevertheless, candidates have
clearly found this topic interesting and many displayed a very detailed understanding.
Results Plus: Examiner Comments
This is a level two answer. There are some correct details about red-shift and CMBR;
even though the candidate has described red-shift as a theory rather than an
observation.
In order to be in level three the candidate would have needed to explain that the
red-shift is caused by the galaxies moving away from us and have written more detail
about CMBR (for example that it is observed in all directions).
Examiner Comments
(2)
To gain full marks here, candidates would have to state what both pieces of evidence were and
give an explanation of each of them, link this evidence to the appropriate theories and explain
which theory was most likely on the basis of the evidence.
This was answered confidently by many candidates and there were some excellent examples of
candidates gaining full marks for well-presented discussions. It was encouraging to see that the
topic is well understood.
Marks were lost by some candidates because they described the two theories themselves rather
than describe the evidence and its relevance.
Results Plus: Examiner Comments
There was good discussion of evidence but not linked to the theories. This acheived
level 2, QWC appropriate, four marks.
Results Plus: Examiner Comments
No marks were awarded here. Theories discussed but no evidence considered.
Mark scheme
Question
Number
(1)
QWC
*
Indicative Content
A description to
include some of
the following facts:
• observation of
visible light led to
discovery of
red-shift.
• galaxies are
moving away from
each other
• CMBR detected
in radio telescopes
• space
telescopes (such
as COBE) gave
more detail of
CMBR • Big Bang
and Steady State
theories were
proposed
• distances to
galaxies could be
determined • Big
Bang could explain
red-shift • Steady
State could explain
red-shift The
description gives
some of the
following details:
• red-shift means
lower frequency /
longer wavelength
• red-shift was
greatest for the
most distant
galaxies
• red-shift means
universe is
expanding • Big
Bang / Steady
State can explain
an expanding
universe • only
Big Bang could
explain CMBR
• CMBR is
residual radiation
Mark
(6)
Level
1
0
1-2
2
3-4
3
5 -6
from the Big Bang
The description
gives some of the
following reasons
for scientists
beliefs
• observation of
increasing red-shift
with distance is a
reason to believe
in expanding
universe
No rewardable material
• a limited description of either red-shift
or CMBR, e.g. light from galaxies was
red-shifted OR Red-shift is evidence for
Big bang. • the answer communicates
ideas using simple language and uses
limited scientific terminology • spelling,
punctuation and grammar are used with
limited accuracy
• a description giving full detail of either
red-shift or CMBR OR some detail of
both red-shift and CMBR, e.g. light was
seen to be shifted towards a longer
wavelength. This means that the
galaxies are moving away from each
other. • the answer communicates
ideas showing some evidence of clarity
and organisation and uses scientific
terminology appropriately • spelling,
punctuation and grammar are used with
some accuracy
• a detailed description of how both
red-shift and CMBR give supporting
evidence for the Big Bang theory, e.g.
light was seen to be shifted towards a
longer wavelength. This means that the
galaxies are moving away from each
other so the Universe must be
expanding. This is evidence for the Big
Bang theory. Cosmic Background
Radiation coming from all directions
provides further evidence for the Big
Bang. • the answer communicates
ideas clearly and coherently uses a
range of scientific terminology accurately
• spelling, punctuation and grammar
are used with few errors
Mark scheme
Question
Number
(2)
QWC
Indicative Content
*
Level
1
0
1-2
2
3-4
3
5-6
Mark
A discussion
linking some of the
following points red
shift • • linked to
movement • both
theories have
expanding
Universe
• redshift support
both CMB • linked
to ageing Universe
• Big Bang ageing
, SS not • CMB
supports Big Bang
only • because
only Big Bang has
single origin
(6)
No rewardable material
• a limited discussion stating both
pieces of evidence or limited detail about
either red shift or CMB e.g. change in
wavelength /red shift shows galaxies /
stars moving away • the answer
communicates ideas using simple
language and uses limited scientific
terminology • spelling, punctuation and
grammar are used with limited accuracy
• a simple discussion including both
pieces of evidence and simple detail
about either red shift or CMB e.g. a
change in wavelength shows galaxies /
stars moving away • the answer
communicates ideas showing some
evidence of clarity and organisation and
uses scientific terminology appropriately
• spelling, punctuation and grammar
are used with some accuracy
• a detailed discussion describing
both pieces of evidence and drawing a
conclusion e.g. a change in wavelength
shows galaxies / stars moving away and
CMB shows Universe has been
changing with time and redshift supports
both theories, CMB supports only Big
Bang because Steady State has
constant Universe • the answer
communicates ideas clearly and
coherently uses a range of scientific
terminology accurately • spelling,
punctuation and grammar are used with
few errors