the speed of light is 186000 mps or some such compared to what? :)
Rephrase please. I'm not sure what you are asking.
The speed of light is approximately 186,000 miles per secpnmd or exactly 299 792 458 metres per second. I don't know what you mean by 'compared to 'what', the speed of light is the same in all inertial frames.
Oops, sorry, didn't see your post there jcsd.
So whatever inertial frame one is measuring by, light travels at c as if the inertial frame was still?
Yes. And that is the 2nd postulate of Special Relativity.
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