Expanding universe

Explain how dark lines (line spectra) in the spectrum of sunlight are produced (2)

Photons of particular frequencies are absorbed (1)

In the sun’s atmosphere (1)

Explain why the position of the line is different in each of the spectra (2)

Light is shifted towards red (1)

As the galaxies are moving away (2)

Evidence of the big bang theory

Redshift of galaxies- indicates the galaxies are moving away from each other.

Olber’s paradox

Cosmic microwave background radiation

A student states that the clocks on board the plane will run slower when the plane is travelling at relativistic speeds. Explain why this is incorrect

from the perspective of the students they are in the same frame of reference as the clock

A student states that the clocks on board the plane will run slower when the plane is travelling at relativistic speeds. Explain why this is correct

from the perspective of the stationary observer there will be time dilation

Einstein based his Special Theory of Relativity on two pieces of knowledge,  which he called ‘postulates’.

One of these is that the laws of physics are the same in all reference frames.

State the other piece of knowledge in which his theory is based. (1)

The speed of light is a constant

Modern cosmology has many observations that remain poorly understood or unexplained.

The outer stars in galaxies are observed to rotate at a different rate to that predicted.

State what is thought to cause this difference (1)

Dark matter

The rate of expansion of the universe is observed to be increasing.

State what is thought to cause this increase (1)

Dark energy

Explain, in terms of wavefronts, why the frequency of the sound detected by the microphone is greater than the frequency of the sound emitted by the buzzer.

The wavefronts are closer together