Red-shift (AQA GCSE Physics): Flashcards
Exam code: 8463
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- FrontGalactic Red-shift
Define the Doppler effect.
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Cards in this collection (24)
Define the Doppler effect.
The Doppler effect is the change in frequency or wavelength due to the relative motion between a source and an observer.
What happens to the wavelength and frequency of waves in front of a moving source?
The wavelength decreases and the frequency increases.
What happens to the wavelength and frequency of waves behind a moving source?
The wavelength increases and the frequency decreases.
Define blueshift.
Blueshift is the decrease in the wavelength of light that occurs when a light source moves towards an observer.
Define red-shift.
Red-shift is the observed increase in the wavelength of light due to the source moving away from the observer.
In the light spectrum from a distant galaxy, the lines are shifted towards the ______ end.
In the light spectrum from a distant galaxy, the lines are shifted towards the red end.
What does the observation of red-shift from distant galaxies provide evidence for?
It supports the Big Bang theory, as it shows that the universe is expanding.
What is the relationship between a galaxy's distance from us and the amount of red-shift observed?
The greater the distance to a galaxy, the greater the red-shift observed, meaning more distant galaxies are moving away faster.
True or False?
A galaxy moving away from an observer will show a decrease in the wavelength of its light spectrum.
False.
A galaxy moving away from an observer shows an increase in wavelength, known as red-shift, not a decrease.
Define the Big Bang theory.
The Big Bang theory states that the universe began from a very small, extremely hot and dense region, which underwent a series of explosions, causing the universe to expand and cool to form the universe we currently observe.
When did the Big Bang occur?
Around 14 billion years ago.
Describe the initial conditions of the universe according to the Big Bang theory.
The universe began from a very small, extremely hot and dense region.
As the universe expanded following the Big Bang, it ______ as it did so.
As the universe expanded following the Big Bang, it cooled as it did so.
What observation about galaxies supports the idea that the universe is expanding?
Galaxies are moving away from each other, and the further away they are, the faster they move.
What evidence from supernovae light spectrums, first observed in 1998, supports the Big Bang theory?
Light from supernovae in other galaxies is red-shifted, showing that distant galaxies are receding (moving further apart) ever faster.
In the explosion analogy for the Big Bang, why do some galaxies end up further from the source than others?
Matter that was travelling at a greater speed moves further from the source of the explosion; matter travelling slower stays closer to the source.
True or False?
If you traced the galaxies' separation back in time, they would become further and further apart.
False.
Traced back in time, the galaxies' separation would become closer and closer together until the entire universe was a single point.
What is the relationship between a galaxy's speed and the distance it has moved since the Big Bang?
The distance a galaxy has moved is proportional to its speed — the fastest-moving galaxies have moved the furthest, and the slowest-moving galaxies have moved the least.
Define dark matter.
Dark matter is unseen matter, inferred from the rotation and motion of galaxies, which suggests there is much more matter in the universe than can be observed directly. Its nature is not currently known.
Define dark energy.
Dark energy is a proposed form of energy suggested to be pushing everything in the universe apart, causing the universe's accelerated expansion.
What evidence suggests the universe is expanding at a faster rate?
Measurements of the expansion of the universe using supernovae suggest the universe is expanding at a faster rate.
Why is dark energy suggested to be counteracting gravity?
If gravity acted alone everywhere in the universe, matter would be expected to move closer together over time. Since the universe is instead expanding, dark energy is suggested as a force counteracting gravity.
If gravity is present everywhere in the Universe, it might be expected that everything will one day become ______ together.
If gravity is present everywhere in the Universe, it might be expected that everything will one day become closer together.
True or False?
The nature of dark matter is well understood by astronomers.
False.
Dark matter's nature is not currently known — its existence is only inferred from the rotation and motion of galaxies.
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