From what I gather from A Brief History of Time, doesn’t Heisenberg’s Uncertainity Principle only applies to sub-atomic particules?
Since we’re being pedantic, “affecting” (as I’ve used the word) is not the same as “changing” as you seem to be implying. If the state of the brick includes it’s current energy state, position, composition, etc., then measuring it does in fact “change” it. If you just mean gross physical properties (such as the height in millimetres), then no, measuring a brick does not necessarily change it.
For the record, yes you are correct about Heisenberg’s Uncertainity Principle, which states that knowledge of the values of certain pairs of properties (such as position and momentum) are mutually exclusive for any given particle.
Well, if Blake “might be dense”, I’m dense times 10 at least. I’m not getting any of this. I’ve struggled in the past to understand this idea in terms of quantum mechanics and I’ve been able to slightly wrap a small portion of my brain around some of it some of the time.
But how the heck does holding a ruler up to a brick to measure its length change the brick in any way that it would not have been changed absent the ruler?
Estes (forgive me for not going to their site and looking, it’s incompatible with my browser) used to sell a device which, when you pointed it at a rocket in flight, would tell you how high the rocket went. This device effectively enabled you to measure the height of the rocket’s trajectory without coming into contact with the rocket, or emitting anything which could strike the rocket, so if you can demonstrate how this changes the rocket, I think I can safely say, you’ll get a Nobel Prize.
It’s easy to measure a brick without changing it. If the brick is inside a building, the brick is smaller than the building. Brick measured. Didn’t even have to see the brick. My measurement has a big margin of error, but you didn’t ask for accuracy. I can also tell you that anything on Earth (or everything on Earth including Earth) is between 0 and .009 suns in size, which is a decent degree of solar accuracy… thousandths of a sun! Measure twice cut once!
Alternately I could say that the definition of a hazelbrick is any brick that is exactly 6"x3"x3" and weighs one pound. So if it’s a hazelbrick, I don’t need to measure it. I might never know if any hazelbricks actually exist, but their measurements can be known without changing them. That’s a bit silly though.
Then would you care to explain how it changes it. In what way is a brick changed if I divert some of the light reflected from it through a clinometer lense? What mechanism is there that allows feedback from light already reflected back to the source of the reflection? I am fairly certain I can measure the position of brick using a clinometer and/or rangefinder without ever needing to interfere with the brick.
Agreed. These types of ‘debates’ are fun (and common here) but applying sub-atomic particle measurement/quantum mechanics to a macro environment displays an ostentatious concern formal rules of the high order.
Pedantic, indeed. Sill fun though.
The point is actually that you need that light to measure it. I.e. something has to interfere with the brick for it to be possible for you to measure it. That you didn’t initiate that interference, or that it would have happened anyway, is irrelevant.
Of course, to make that truly self-evident, the wording of the statement has to be changed, but it is what it’s meant to say.
Well, no, it’s highly relevant. The question was whether you could measure something without changing it. That is very different from your point, which is that you can’t measure something that doesn’t change.
The OP specifically wants to know if it is posible to measure something without the act of mesuring having an effect on the object. By using light we can measure somehting without the act of measuring having any effect.
What you are talking about is a change that would have occured whether the act of measurement occured or not. It is quite clearly doesn’t irrlevant to the original question. Of course you can’t measure somehting that doesn’t change, that’s because objects that don’t change can’t exist in this universe. All objects change and when they do change they can be measured using the energy such changes produces. The act of measurement doesn’t change the brick (which is what the OP wanted to know), the brick changing all by itself is what permits the sct of measurement. If you didn’t take the measurement the change would still have occurred.
It applies to everything; it’s just that for macroscopic objects it’s small enough to ignore.
I don’t remember the details, but I’ll throw this out anyway. Some years ago in Scientific American, I read an article about a process that could measure quantum states without interacting with the target, or emitting any light ( or anything else ). The mere possibility of interacting registered on the instrument, allowing the state to be determined without change or interaction.
I can’t see how measuring the tempature of a star or the Sun (or planet) from earth or orbit will change it. Also the lightwave signature of either.