Do you wish there's a god?

[Belacqua]

At work.


Uhm... but, at their base, aren't even 'Measurable observations' actually subjective?

An inch length is, effectivly, just some mutually agreed upon 'Thing'.

Meters are the same.

Astronomical units are... simply our agreed upon 'Earth  orbital radius from parent star.' ?

Every one uses the agreed upon 'Standard'. But, at a base level, said standard us still arbitrary and kind of subjective.

Hope I'm making sense.

Often people use the word "objective" to mean "eternal and universal." But that gets us into trouble.

You're right that meters and astronomical units are not eternal and universal. The cloud beings who live in a distant galaxy have never heard of them and couldn't understand them. Nor would ancient peoples who used cubits instead. But a thing need not be universally intelligible to be objective among people. 

Once people have agreed on what a meter is, we can all talk objectively about the same thing.