Quote:
Originally posted by Pragmatist:
"why you can't observe light speed as half c
if you travel at half c?"

To put it as simply as possible:
Because the length of your 'measuring stick` is changed.
Relative to which reference frame? You only observe a change in length when the measuring stick travels with a speed v relative to you. When you travel with the measuring stick it is not shorter at all; because it is then at rest relative to you.

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