Without a reference frame, what experiment can you perform that would tell you that you're accelerating?
Well, to be really pedant, if you were spinning around yourself, you'd feel an acceleration.
Wouldn't there be a force in the direction you are accelerating in?
Anyway, when you accelerate a car, you are not feeling acceleration, you are feeling the force of the car on you. Imagine being inside of a box that is in free fall. What experiment could you run to determine if you were accelerating?
Well, yes, that would be the standard way to look at it. Sorry for being confusing.
>Anyway, when you accelerate a car, you are not feeling acceleration, you are feeling the force of the car on you.
According to [Force = Mass * Acceleration] you can take them as equal (apart from the constant factor of your mass). In the freefalling box that is accelerating (and thus no longer in free fall) you'd also feel a force. No need for experiments if you have your normal senses. You'll be pressed against one side of the box. (And if the acceleration is 9.81 m/s^2 you couldn't distinguish it from a box on earth.)
That is actually the basic premise of general relativity - the equality of 'inertial mass' that resists against acceleration and 'gravitational mass' that happens because of, well, gravity. It's like the idea of constant speed of light for special relativity.
edit: Unless you're talking about gravity, which accelerates all parts of the setup equally, thus no force results.. but that would need something else in the experiment, either a great amount of matter or energy. But then you'd have a reference frame right there. (Mathematically. As for an experiment.. hm. Check for perturbances from space-time distortions that result from rotating gravity sources, maybe.. most gravity sources in this universe are rotating. There's an experiment done that checked that for Earth.[1])
And as shardling said, a reference frame isn't a physical thing that is created and destroyed - it's simply the zero point for your system of measurement - but the measurement would work just fine if you started with any number, zero is just convenient.
I may have missed the point of dropping an object, though. I thought the idea was to create a physical point we could anchor the coordinate system to, and in that way be able to measure acceleration.
You can't. There is absolutely no test that can tell you this.
You can't "drop" anything - whatever force is accelerating you also accelerates the object, so letting go of it tells you nothing.
If the force is external and doesn't apply pressure then you have to drop an object.
If the force affects the entire universe the same way then that's aether and can't be measured / doesn't exist. But that was not the kind of force I was using to disprove "you can't move".
What kind of force is external and doesn't apply pressure, and also doesn't affect the dropped object? There is no such force, and therefor no such test.
If you dropped something it would simply stay right next to you, even if you were accelerating - both of you are accelerating at exactly the same rate.
If you want a useful thought experiment about physics then you need to give reasonable physics tools. Otherwise you get something like "Pretend you are an inanimate green blob. You can't climb a hill, can you? Therefore climbing a hill is an illusion."
The only type of acceleration that is undetectable is gravity - and gravity will effect the dropped object exactly as much as you.
Dropping something was only one idea, but feeling pressure is much simpler.