For the graph shown above, a) what quantity would you label the y-axis with if the distance is between galaxies and the Earth? Explain your answer. Think through what we know is happening, motion-wise, out there in the galaxy. b) Also explain why you think there are dots and a solid line, on the graph.
For the graph shown above, a) what quantity would you label the y-axis with if the distance is between galaxies and the Earth? Explain your answer. Think through what we know is happening, motion-wise, out there in the galaxy. b) Also explain why you think there are dots and a solid line, on the graph.
a)
For the graph shown above, the y- axis would be labelled as velocity, if the x-axis is labelled as distance. This graph is termed as Hubble's diagram and it represents cosmic expansion.
Hubble also measured that majority of galaxies show redshifted spectral lines from the observed values and redshift in spectroscopy means that the object is moving away from the reference position.
Hubble used Cepheid variable stars to measure the distance of galaxy and using shift in spectral lines he measured velocity and concluded that, they are directly corelated.
From this motion, we can conclude that the universe is expanding.
Thus, the y- axis would be labelled as velocity and we can conclude that the universe is expanding.
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