What constitutes an observer?

[magus niche]

Is it true that Einstein believed that for reality to exist, an observer must be present?

If so, what is the current theory on the existence of an observer, early on in the development of space-time?

[zefram_c]

I have not heard of this Einstein quote before. In special relativity, an "observer" is simply something that can establish an inertial frame of reference. Any and all objects that have mass satisfy this requirement; there is no need for the observer to have intelligence or actively perform measurements.

[Cosmo16]

Magus- This seems to me to be a question of quantom mechanics which states that no object has any measurable quanity untill it is being measured.

Also, the quote you are referring to seems to be one that he made (At least partially sarcasticly) to refute quantom mechanics.. he considered Quantom mechanics to be bunk.

[pmb_phy]

Is it true that Einstein believed that for reality to exist, an observer must be present?
I never saw Einstein say that. But I doubt he did. I recall him saying something like "Is there moon there when nobody is looking?" though.

If so, what is the current theory on the existence of an observer, early on in the development of space-time?In special relatvity the term "observer" is taken to mean a system of clocks and rods, i.e. a frame of reference.

Pete