The general theory of relativity leads to the conclusion that the fabric of space time is ever expanding . This has indeed been proved by Hubble when he found out that the galaxies are moving away from each other.In fact all stellar bodies are moving away from each other. My question is this : If space time in itself is expanding, how is it possible that we are able to observe such an expansion since we too are a part of this space time. Let us consider a coordinate sytem in which each axes are rubber rods. Now let there be markings at regular intervals on these rods to help us measure length .Now if this coordinate sytem expands relative to some other coordinate system it would mean that the rubber rods have been stretched. Now if we consider these rubber rods as representing space itself , then any stretching of rubber rods would not be visible if a person were to use these markings on the rods as a measure of length , because though anything in this space would have expanded, the rods too would have been stretched accordingly so something that would have been 2 units of length will still be 2 units of length My concepts of relativity and 4 dimensional space time are extremely poor . This question probably is baseless , but can someone explain what is the problem in the above reasoning.