The "Hubble speed" of Imagine whereever Imagine goes, a crowd of people always collects, trying to explain the world----Imagine exerts a kind of magnetism or enchantment----and being no exception I also feel compelled to explain the world to Imagine. Most recently Imagine has written: ------------------------ What is our actual Hubble "speed" ? ... What is our own recession speed? Zero ? Since temperature seems to decrease with time, is it, or could it be, related to CMB? ----------------------- A THOUGHT EXPERIMENT for Imagine The CMB temperature has been measured in each direction of the sky very carefully and although the basic temp is 2.7 kelvin it is just slightly warmer in the direction of Leo (that very nice spring constellation). It is between 3 and 4 MILLIkelvins warmer in the Leo direction and the same amount colder in the away-from-Leo direction. So the uniformity of the temperature around us is not perfect. But suppose we had a rocket ship with enough room and supplies for several friends and able to achieve a speed AWAY from Leo just fast enough so that the sky is now the same temperature in all directions. Then we in the ship would be AT REST vis a vis the CMB. Our solar system and our galaxy are both almost at rest relative to the CMB already, but by means of this rocket ship we can arrange to be perfectly at rest in respect to CMB. Now suppose that 100 million light years away from us there are also some nice people who wish, like us, to be at rest with respect to the CMB and they too have a rocket ship. They measure the temperature carefully and find the hot spot and then they speed away from the hotspot at just the right speed so that it seems cooler to them and the whole sky is also for them the same temperature. They are in some other galaxy because 100 million light years is an intergalactic distance. So those people are also now at rest relative to the CMB, like we are. Suppose that we unroll a long tape measure, marked in centimeters, between them and us. We take care not to let the tape measure touch any stars, which might burn it and spoil the thought experiment. Does the distance measured by the tape measure, between these two points (both at rest) change with time? And if so, by how many centimeters per second is it changing?