- #1
Jeff Root
- 76
- 6
If I want to measure my height, I need to find not only
the location of the top of my head, but also the location
of the bottom of my feet. The difference is my height.
I make those measurements by placing the end of a tape
measure against the floor, and then find where the top of
my head is against the tape. If I leave out the first
step, the second step is useless.
Does that first step constitute a measurement?
If not, what is it?
Whatever it is, are all measurements like that? Every
measurement consists of (at least) those same two steps?
If I want to measure some property of a photon-- say the
simplest property that has a quantitative value, not just
existence versus nonexistence-- are there (at least) two
steps, like two measurements?
When I measure my height, the two steps necessarily take
place in different locations. Do they also necessarily
take place at different times, in my reference frame?
(You can assume that my head and my feet are not moving
relative to each other.)
How about when measuring a photon?
-- Jeff, in Minneapolis
the location of the top of my head, but also the location
of the bottom of my feet. The difference is my height.
I make those measurements by placing the end of a tape
measure against the floor, and then find where the top of
my head is against the tape. If I leave out the first
step, the second step is useless.
Does that first step constitute a measurement?
If not, what is it?
Whatever it is, are all measurements like that? Every
measurement consists of (at least) those same two steps?
If I want to measure some property of a photon-- say the
simplest property that has a quantitative value, not just
existence versus nonexistence-- are there (at least) two
steps, like two measurements?
When I measure my height, the two steps necessarily take
place in different locations. Do they also necessarily
take place at different times, in my reference frame?
(You can assume that my head and my feet are not moving
relative to each other.)
How about when measuring a photon?
-- Jeff, in Minneapolis