Variations in the composition of the planets are largely responsible for the density differences.

行星构成成分的不同是造成密度差异的主要原因。

youdao

This shows the old and new Shanghai density differences.

可见新旧上海人密度差异。

youdao

For example: the density differences and related pressure drop over the liquid layer must be scaled correctly.

比如，水和铝液密度的差异和在不同液位高度时相对压降必须正确地定标。

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OK, all this is a long way short of proof that traffic density alone causes these differences.

BBC: Crashes

There are also huge differences in population density across the country, with the population per square kilometre ranging from nine in Eilean Siar (the Western Isles) and the Highlands to 3, 395 in Glasgow.

BBC: Census shows 'highest' Scottish population ever

But it is possible to detect minute deviations in this signal, and these fluctuations - seen as mottling in the map - are understood to reflect the differences in the density of matter when the light parted company and set out on its journey all those years ago.

BBC: Planck satellite: Maps detail Universe's ancient light