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We say space-time is not rigid.

But if, e.g. space expands then even the 'meter' stick we use to measure distance expands - (I guess distance is nothing but number of times a meter stick is repeated to reach from pt A to pt B which then won't change) - then how will we ever know that space (i.e. distance between A and B) has 'expanded'

What is it that I'm missing in this - Why am I wrong?

Dale
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aman_cc
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1 Answers1

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But if, for e.g. space expands then even the 'meter' stick we use to measure distance expands - (I guess distance is nothing but number of times a meter stick is repeated to reach from pt A to pt B which then won't change)

This is not correct. The number of meter sticks from A to B does increase. If A and B are each stationary with respect to the cosmic microwave background and are exchanging light signals they will each find that the other’s signals are redshifted and progressively delayed. Since the meter is based on the speed of light, this indicates an increasing number of meters between them

Dale
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