Do experimental measurements give the true value of a physical quantity?

Question

explain.

~I say no it doesn't. But why that is is up to debate on my part. I think that it doesn't give the true value because there is always a source of error and also varying factors such as temperature fluctuations, differences in measuring device calibration, and individual errors that can vary results.

Is this thinking alright?

Answer 1

My answer is a little different than yours but mostly for the same reasons you cite. Experimental measurements MAY give the true value but we have no way of knowing what the true value is; therefore, we don't know if the measurment is 100% accurate or not. And of the 50 measurments we make, for example, which of the 50 is the correct value. Perhaps none of them. Perhaps some of them. There may be those who will argue that experimental measurements give the true value +/- the VERY small standard deviation listed; however, those can be quoted at the 95% confidence interval, or the 99% or the 99.9% or 99.99% but none will give the confidence limit of 100%. My corollary to that is that some of the measurements are so precise (then we assume so accurate) that we essentially know the true value for all practical purposes.

Answer 2

So is there a correct answer to this?
It was a question in my ASA for my lab for physics.

I'm sort of confused by what you say. You say that it may give the true value but we don't know essentially the true value itself. However you also mention that the values can be so precise that we "know the true value".

If I think about this correctly then there is no way to tell if what you measure is the true value and thus you may or may not get the true value at all?

So my answer was incorrect to a certain degree?

Answer 3

No. I think your answer is correct. And I think the correct answer is that we don't know the true value. Having said all of that, I think we may be able to measure the true value with such a high degree of precision that we essentially know the answer. It just isn't exact, or at least we don't know that it is. Remember the Heisenberg Uncertainty Principle.

Answer 4

Heisenberg Uncertainty Principle?
I've never heard of it at all.

Answer 5

I'm sure you know about energy levels for electrons in atoms. If you confine a particle in a box then, just like in case of electrons in atoms, there will be energy levels that that particle can occupy. The smaller the box is, the higher the lowest possible energy level will be. So, the more precise you locate the particle at some position the more uncertain its momentum will become (energy equals magnitude of momentum squared divided by twice the mass).

It turns out that this is a general principle.

Answer 6

If the physical quantity you want to measure is discrete (i.e. an integer multiple of some number, then you can measure it exactly. An example is electric charge. The electric charge is always a multiple of the elementary charge (minus the charge of the electron).

So, if you measure a charge accurate enough so that the error in the measurement becomes much less than one elementary charge, you just divide it by the elementary charge and round it off to the nearest integer. The charge expressed in units of the elementary charge will then be exact.

Answer 7

Thanks Count Iblis =)

Answer 8

Isn't "alright" supposed to be two words, as in "all right"?