# Inertial Frames

1. Dec 9, 2008

### ritwik06

It is sometimes heard that inertial frame of reference does not actually exists and is only an ideal concept. What do you guys think?

Say, for example, An object is placed far away from all objects that can exert force on it. A reference frame is taken by taking the origin and axes fix in this. Will the frame be necessarily inertial?
I think yes. But I am not very confident.

Is anything in the universe absolutely non accelerated???

2. Dec 9, 2008

### Staff: Mentor

I would say that it depends on what it would mean for a reference frame (ineritial or not) to "actually exist". A reference frame is nothing more or less than a coordinate system, and as such I don't really know how the term "actually exists" would apply.

I would take a practical stance that (insofar as any reference frame can be said to "actually exist") a reference frame is actually inertial if no deviations from the standard form of the laws can be detected in the given experiment. If an effect is smaller than what is experimentally observable then it is fine to ignore.

3. Dec 9, 2008

### ritwik06

"actually exist" meant in practical world.
Is anything at absolute rest or moving with uniform velocity???
And I am not talking to ignore those effects, however small they may be.
Is there any such inertial frame of reference?

4. Dec 9, 2008

### Georgepowell

I would say no, just because the range of a bodies gravitational pull is infinite. so where ever this thing that is at rest is, it will accelerate slightly due to the acceleration of gravity.

5. Dec 9, 2008

### D H

Staff Emeritus
That's a bit of a contradiction. The practical world worries about what is practical. Newtonian mechanics does not "actually exist" and yet many scientists and engineers use Newtonian mechanics (a) because its "practical", (b) it is sufficiently accurate for the problem at hand, and (c) using a more accurate model is not warranted. For that matter, general relativity and quantum electrodynamics probably don't "actually" exist, either; we just don't know what's wrong with them yet.

The rest of your post veers far from this concept of the practical. You are talking about whether inertial frames exist theoretically given perfect measurements. Of course not. Then again, neither does Newtonian mechanics "actually exist".