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tovisonnenberg
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How does the expansion of space cause light to lose energy?
That is not correct. In an expanding universe light emitted from a cosmologically remote point DOES lose energy as it travels and is red-shifted more and more, and loses energy more and more, as the point of reception is farther and farther away. There is no conservation of energy on cosmological scales.stefan r said:The light has not really changed energy.
Just to be clear, this refers specifically to the energy relative to comoving observers, an assumption that is not always stated explicitly. Energy is not an inherent property of a light signal by itself (the stress-energy tensor is). In that sense, the light has not changed energy, because energy is not a property inherently associated to it.phinds said:That is not correct. In an expanding universe light emitted from a cosmologically remote point DOES lose energy as it travels and is red-shifted more and more, and loses energy more and more, as the point of reception is farther and farther away. There is no conservation of energy on cosmological scales.
This is missing a qualifying statement. The baseball does not have an inherent energy and momentum either - it only has a particular energy and momentum given some fixed frame. As we all know, energy and momentum are not Galilei invariant. They will take different values in different inertial frames and no frame can be said to be preferred over another.stefan r said:If someone throws a baseball from the back of moving pickup truck it will not be going very fast when you catch it. It would hit your glove hard if they threw it forwards and you caught it. The pitcher throws the ball with the same energy/momentum each time. It is only the measurement from your perspective that changes with each pitch.
Good point. Thank you for that clarification.Orodruin said:Just to be clear, this refers specifically to the energy relative to comoving observers, an assumption that is not always stated explicitly. Energy is not an inherent property of a light signal by itself (the stress-energy tensor is). In that sense, the light has not changed energy, because energy is not a property inherently associated to it.
Inflation has no effect on CMB wavelength because it happened before the CMB was released. Do not confuse inflation with expansion. Expansion is the scale of the universe increasing with time, inflation is a hypothetical period of rapid expansion in the very beginning of the universe, before CMB, before nucleosynthesis, intended to explain (among other things) why the universe is so homogeneous.Ilythiiri said:So, inflation itself has zero effect on (for example) CMB wavelength
In the context of the expanding universe, redshift refers to the phenomenon where light from distant galaxies appears to have longer wavelengths, shifting towards the red end of the visible light spectrum. This is due to the stretching of space caused by the expansion of the universe, causing the light to appear to have longer wavelengths.
The expanding universe causes redshift because as space expands, it stretches the wavelengths of light that travel through it. This stretching of wavelengths is known as cosmological redshift. The farther a galaxy is from us, the more space has expanded and the more redshifted its light will appear.
Redshift is used to measure the expansion of the universe by observing the redshift of light from distant galaxies and using that information to calculate the distance of those galaxies. By measuring the redshift and distance of many galaxies, scientists can plot a graph of the relationship between redshift and distance, known as the Hubble diagram, which can be used to determine the rate of expansion of the universe.
Yes, redshift can also be caused by other factors such as the relative motion of the light source and the observer. This is known as Doppler redshift and is caused by the motion of an object towards or away from us. However, for objects at very large distances, cosmological redshift is the dominant factor.
Redshift has significant implications for the fate of the universe. The observation of redshift in the light from distant galaxies led to the discovery of the expanding universe, which in turn led to the theory of the Big Bang. Redshift also provides evidence for the accelerating expansion of the universe, which suggests that the universe will continue to expand indefinitely and may result in a "Big Freeze" or "Heat Death" scenario.