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Putting the expansion of the universe into contextIt is important always to remember that it is the space itself that is expanding and not things that are moving quickly. On our scale this expansion is incredibly tiny.Let me do some simple calculations The Hubble constant or expansion coefficient of our universe is about 70km/sec per megaparsec in astronomers units.Let us now put it into more familiar units and relate it to distances in our solar system. A parsec is about 3.26 light years or 206,265 times the distace of the earth from the sun.So over a distance of 206,265,000,000 the distace of the earth from the sun the expansion velocity is 70,000,000 millimeters per second (remember there are a million millimetres in a kilometer)So the expansion of space between the earth and the sun is 70,000,000/206,265,000,000 millimetres per second.This is about .00034 millimetres per second in about 150 million Km let us give this velocity a bit longer to show itself, say one yearthere are 365x24x60x60 = 31,536,000 seconds in a yearso in a year the space equal to the distace from the earth to the sun the space expands by 31,536,000x 0.00034 millimetres 10,722 mm or about 10 metres.But surely I hear you say if the earth got ten metres further away from the sun every year over many millions of years this would have a significant effect? the answer is no! because the expansion of space does not significantly push the earth away from the sun because the energy of the attraction of gravity between the earth and the sun is so much greater that it completely overwhelms this effect and no change takes place.It is only on the vast scales of distances between clusters of remote galaxies that the effect of the expansion of space can be measured. To measure it in the laboratory would be totally impossible.
The exact value of the Hubble Constant is still not accurately known, but is generally believed to be between 50-100 km/sec/Mpc.
The error margin in calculating the distance of a galaxy 10 million light years away will be greater than the increase due to expansion which has occurred during that period.Expansion will have increased the distance to a galaxy 10 million light years by less than one percent in that period.