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I always like simplistic but consistent facts to understand something a bit better. Let's neglect cosmological expansion first and rather focus on the immediate vicinity. A rocket A is fired and a rocket B is considered to be a point at rest with respect to A's initial position. The visible spectrum of light is sent form A to B and B can see A's spectrum ...


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There's essentially only one type of redshift - the special-relativistic Doppler shift, properly adapted to the rules of general relativity. In curved space-time, there's no global notion of relative velocities, and we need to parallel transport the emitter's velocity vector to the observer along the light path. In addition to this abstract notion of ...


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Doppler shift occurs only when the sender, the receiver or both are moving relatively to each other. As the black boxes rest at the bottom of the ocean and the search ships move relatively slow, there won't be any significant Doppler shift. However, if the Ocean Shield receives several signals at different locations (the location of the Ocean Shield), the ...


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There are a few other reasons why we think the universe is expanding. Wikipedia lists and explains them far better than I will ever be able to. One thing though, your ruler is not expanding. The intermolecular forces are making sure the distance between molecules stays the same. Empty space is expanding, expanding essentially the distances between weakly ...


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No, EM radiation cannot be completely dissipated. It simply expands to fill the increasing size of the universe, so that each cubic meter contains less of its original free EM energy as the universe grows larger. That reduction is reflected by a decrease both in the frequency of the light within that volume and by an overall dimming of the light. There is ...



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