Question

big bang theory has led to two testable ideas: 1. in the first few seconds after the big bang, a small amount of protons and neutrons fused to produce helium and a trace amount of lithium. heavy elements were not formed because the conditions for the formation of heavier elements require a much greater time (tens of thousands of years) than the big bang lasted for. therefore, when we measure the elements in distant young galaxies we should expect to see large amounts of hydrogen (about 75% of all elements), smaller amount of helium (about 25%), and trace amounts of lithium and other elements. 2. measurements of these elements in young galaxies and stars match these predictions precisely.

1. explain what is meant by red - shifted.
2. study the spectral diagrams below. compare them to the unshifted spectral diagram opposite. what can you say about galaxy a and galaxy b?
3. explain how the red - shifting of galaxies provided evidence for the big bang.
4. (a) what is the cosmic microwave background? (b) explain how the discovery of the cmb provided evidence for the big bang.
5. why could heavy elements not form during the big bang?

Explanation:

1. Red - shift refers to the displacement of spectral lines towards the red - end of the spectrum. It occurs when a source of light (like a galaxy) is moving away from the observer. The Doppler effect for light causes this shift. As the source moves away, the wavelength of the light is stretched, resulting in a shift towards longer wavelengths (red end).
2. Comparing the spectral diagrams of galaxy A and B to the unshifted one: If the spectral lines in galaxy A and B are shifted towards the red - end compared to the unshifted spectrum, it indicates that they are moving away from us. The degree of shift can give an indication of their recession velocities.
3. Red - shifting of galaxies provided evidence for the Big Bang because it shows that galaxies are moving away from each other. This is consistent with the idea that the universe is expanding, which is a key prediction of the Big Bang theory. As the universe expands from a single, dense point (the Big Bang), galaxies move apart, causing the observed red - shifts.
4. (a) The cosmic microwave background (CMB) is a faint glow of microwave radiation that fills the universe. It is the afterglow of the Big Bang, remaining radiation from a very early and hot stage of the universe.

(b) The discovery of the CMB provided evidence for the Big Bang as it is consistent with the prediction that the early universe was hot and dense. As the universe expanded and cooled, the radiation from that early stage was stretched to microwave wavelengths. The nearly uniform distribution of the CMB across the sky also supports the idea of a homogeneous early universe, as predicted by the Big Bang theory.

1. Heavy elements could not form during the Big Bang because the conditions during the Big Bang did not last long enough. The formation of heavy elements requires processes like nuclear fusion in stars over long periods (tens of thousands of years). The Big Bang was a short - lived event, and there was not sufficient time for the complex nuclear reactions needed to build heavy elements from hydrogen and helium.

Answer:

1. Red - shift is the displacement of spectral lines towards the red end due to the source moving away, stretching the light's wavelength.
2. If spectral lines in A and B are red - shifted compared to the unshifted spectrum, they are moving away; degree of shift indicates recession velocity.
3. Red - shifting shows galaxies are moving apart, consistent with the universe expanding as predicted by the Big Bang.
4. (a) The CMB is a faint microwave radiation filling the universe, the afterglow of the Big Bang.

(b) It is consistent with a hot, dense early universe that expanded and cooled, and its nearly uniform distribution supports the Big Bang's prediction of a homogeneous early universe.

1. Heavy elements require long - term nuclear fusion processes in stars, and the Big Bang was too short - lived for such reactions to occur.