I understand that in a uniformly expanding universe of the Einstein-de Sitter type, the distances between galaxies is constantly increasing but that the red shift displayed by those galaxies is not due to the Doppler shift - rather it is due to the fact that, during the time it takes for their photons to reach us, the universe has expanded thus stretching the wavelengths of the photons. This suggests that it ought to be possible in principle to measure the expansion of the universe in the laboratory by measuring how the apparent wavelength of a source of monochromatic light varies with its distance from the receiver. Assuming a value of the Hubble constant of H = 2.33 x 10-18 s-1, we should expect a red shift of H/c = 7.77 x 10-28 for every metre of extra separation. Notwithstanding the fact that this shift is so small, it could not possibly be measured, I believe that it must exist. I have, however, heard it categorically stated that while the distances between the galaxies is increasing, the dimensions of the galaxies themselves, and everything in them (including planets and atoms) stays the same. As I see it, this statement is open to three interpretations: It means exactly what it says - and therefore my suggested thought experiment would return a null result because, on a local scale, space is not expanding. It means that, while the universe is expanding on a cosmological scale as evidenced by the galactic red-shift, on a local scale, any measurement that we make eg with a metre ruler, will stay the same because our measuring instruments expand as well. My thought experiment will give a positive result but the measured distance between source and receiver will not change. The statement is not trying to say anything profound at all; it simply means that, while the galaxies are expanding in a cosmological sense, this expansion is completely overwhelmed by the force of gravity which holds them together. Can anyone help me to resolve this issue?