(adsbygoogle = window.adsbygoogle || []).push({}); Is it impossible to separate a distance of "1light hour" in space?

i was having a debate with a guy on a site and he argues it is impossible to separate such a distance in space.

Suppose two observers A & B they are relatively at rest, A wish to do an experiment so A & B moves apart by sending laser signals, after a huge amount of time, they slows down their speed to get accurate measuremet, A continuously sends a laser beam to B and B does the same. A notices that a laser beam sent to B took exactly 2 hours to return, which means A is now exactly 1 light hour distant apart. B also does this, so B also concludes that he is exactly 1 light hour away from A. They does this until finally they became relatively at rest to eachother

Or do they disagree?

When A Calculates exact 1 light hour distance, won't that be 1lhr for B??

His arguement was when one of the observers calculate his distance, the other won't get the same measurement because of different frames

Is his argument correct?

Is there really no way to separate a distance in space?

Even i tried saying there is a 1lhr long nebula between these two observers, still he won't agree

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# Is it impossible to separate a distance of 1light hour in space?

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