We use radiowave-measuring systems.

A is star. B is antenna. C is moving thing, that 'radiowave'.

A.----------------------B.

A, send C, or make and send C.

A. -------------C-------B. C goes speed D.

B see C. B measure at, C has some D.

How B can calculate, what is it distance to A?

If measured D at point B, is constant speed; then A dont 'make' C, because D is constant. If A make C, then D at point A is 0.

How B can calculate, what is it distance to A. It cannot using only D, speed(km/s). Km/s cannot exist without km, it need km, and we dont know that km.

B cannot know, what is it distance to A. - Only using C:s speed(D).

How B can know, what is it distance to A? 1. C must have with in 'km-measuring equipment'. 2. Need E, and E can measure distance, A to B.

B is located at earth. B can be E, other (B).

B can be Earth, to our equipments. Not anything else. B looks always A and other(B).

But. Because B see A and other(B), like A, we come back start.

B cannot measure distance to A,(or other(B), only by measuring C-speed(D). .

A. Is star, galaxy, sun, etc. B. Is earth or near(radiowave-antenna.) (B).Is star, galaxy, moon, etc. C. Is Radiowave, light, etc. Moving object. D. Is speed at this moving object. E. Is other (B).

How do we can measure planets distances at space?

What is maximum ball-size, what we can measure at our measuring equipments? B is center of that ball.

Mmmmm.?. Wondering?