Am 21.10.2015 um 05:34 schrieb Stephen:

> I am having difficulty with that. My chosen frame of reference is
> inertial and both the apple and Earth are accelerating. Albeit a very
> small acceleration in the case of the Earth.

Then tell me, how do you know that your frame of reference is inertial?

Also note that you need to choose a frame of reference sufficiently
local to both Earth's surface and the apple, otherwise your frame of
reference will distort over time, which you'd then have to factor back
in to judge changes of distance over time.

Maybe one of the fundamental hurdles you need to take is this: Space
distorts over time, and changes in relative position do not necessarily
require an absolute movement of the objects involved.


>> What you should be able to notice is you being subject to acceleration:
>> If someone locked you in an elevator cabin, you couldn't tell the
>> difference between being "stationary" on Earth's surface, and being
>> subject to an acceleration of 9.81 m/s^2 in deep space.
>>
>> Because there is no difference.
> 
> With a pendulum you could but who am I to teach my grandmother to suck
> eggs when it comes to nitpicking. ;-)

No, as a matter of pure fact you couldn't (the pendulum thing; I don't
know about your grandmother and the eggs). Not unless you know something
that would win you the Nobel prize :)

>>> Since we are talking about speeds of metres per second I assume we can
>>> dismiss any relativistic effects.
>>
>> Strictly speaking we can't, as the whole thing /is/ a relativistic
>> effect.
>>
>>> Can you explain why a force of one Newton acting on a mass of 5.97E+24
>>> Kg can produce an acceleration of 9.81 m/s^2?
>>
>> No, but why should I?
> 
> Because I asked nicely.
> 
>> - Not all of Earth's mass is accelerating at 9.81 m/s^2; the deeper you
>> go, the smaller the acceration, until it drops to zero at Earth's center.
> 
> Great! a mass of round about 100 grammes distorts the Earth's surface.

Well, /any/ mass distorts the Earth's surface...

>> - I have no idea where you got the one Newton from. The actual force
>> pushing Earth's surface outward is about _ten_ Newton _per kg of surface
>> mass_. More precisely it is 9.81 N/kg. Or 9.81 m/s^2.
>>
> Rough and ready:
> http://hypertextbook.com/facts/2004/WaiWingLeung.shtml

Ah, I see - so I understand that you're still obsessed with the apple
having anything to do with the whole smash, when in fact its effects are
(as you correctly note) negligible. It doesn't /cause/ the distortion of
space - that's by far and large Earth's job - its sole purpose is to
help /visualize/ it, by providing an intertial frame of reference.


> Personally I prefer to pick my frames to make sense in the real world.
> If you can't hit it with a hammer or build a bridge out of it. Then it
> is just an interesting thought.

Well, then you're not the target audience of my post, so move along,
there is nothing for you to see here ;)

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