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> What happens is that Earth, by virtue of having mass, gobbles up space
> inside and around it. Always. Constantly. Whether there are any apples
> out there or not. (So does the apple, but that's negligible compared to
> Earth's dietary budget.) There's no acceleration or even movement
> involved there /per se/ - in the vicinity of matter, distances just
> shrink over time. Fast.
>
> If it was only for this mechanism, earth would shrivel to nothingness in
> a matter of... minutes? hours? Dunno, but certainly in less than a day.
> Space between the elementary particles would just shrink to zero.
>
> Fortunately, electromagnetic force comes to our rescue: The electron
> clouds of any two atoms in the universe repel each other. Partially this
> is compensated by the fact that the electron clouds of any atom in the
> universe also attracts the nucleus of any other atom, but on average the
> net EM force is repelling. And there are a lot of atoms in the Earth. So
> the atoms making up earth constantly accelerate away from each other.
> Earth is exploding.
If gravity (or rather, mass) causes space to contract and get gobbled
up, this must mean then that EM forces (and other equations?) must
somehow be able to measure distances "outside" of this distorted and
gobbled up space? There must be an external "real" space that is somehow
related to the distored spacetime by the distribution of mass around.
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Am 18.10.2015 um 16:29 schrieb Stephen:
>> Also, think of this: If you throw an apple, it moves through space in a
>> /straight/ line - any apparent curvature of its trajectory is due to
>> Earth's surface constantly accelerating upwards. Not towards the apple
>> but away from Earth's center. In a lump of space that's busy shrinking.
>>
>
> If you say so. But consider using another inertial frame of reference.
> One that contains both the Earth and the apple. Which object, the Earth
> or the apple, travels a greater distance in the same time frame?
> I hazard a guess that it will be the apple that has the greater velocity
> and thus acceleration.
Whatever frame of reference you choose - if it is truly inertial, you'll
always find the apple (while airborne) moving at constant velocity (or
remaining at rest, which is a special case thereof), and Earth's surface
accelerating radially from its center at 9.81 m/s^2. (As long as you
ignore aerodynamic drag and remain sufficiently close to Earth's surface
and the apple, that is.)
(Hint: What makes a frame of reference inertial? The fact that it
doesn't accelerate. How can you test it? By releasing some item with an
initial velocity of v=0 relative to the frame of reference, and
verifying that the item remains stationary. If you like, do the
experiment inside an elevator cabin with no windows.)
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Am 19.10.2015 um 09:18 schrieb scott:
> If gravity (or rather, mass) causes space to contract and get gobbled
> up, this must mean then that EM forces (and other equations?) must
> somehow be able to measure distances "outside" of this distorted and
> gobbled up space? There must be an external "real" space that is somehow
> related to the distored spacetime by the distribution of mass around.
No, there's no need for any "meta-space". In the vicinity of any mass,
EM forces still propagate according to Maxwell's wave equations through
whatever space is there at the very moment the wavefront traverses it.
Which is exactly why light appears to "bend" around massive objects.
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>> If gravity (or rather, mass) causes space to contract and get gobbled
>> up, this must mean then that EM forces (and other equations?) must
>> somehow be able to measure distances "outside" of this distorted and
>> gobbled up space? There must be an external "real" space that is somehow
>> related to the distored spacetime by the distribution of mass around.
>
> No, there's no need for any "meta-space". In the vicinity of any mass,
> EM forces still propagate according to Maxwell's wave equations through
> whatever space is there at the very moment the wavefront traverses it.
I suppose that the EM waves travel very much faster than the space is
getting distorted, so in terms of the "reaction time" of atoms being
able to move to keep up it is no problem at all. Until you get to a
black hole :-)
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On 10/19/2015 3:06 PM, clipka wrote:
> and Earth's surface
> accelerating radially from its center at 9.81 m/s^2.
I know it is the psilocybin mushroom season but I thought I was the old
hippy who had taken mind bending substances (in the past, I might add in
case PC Plod is listening).
You have lost it dear friend.
You have lost it.
--
Regards
Stephen
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Am 19.10.2015 um 19:44 schrieb Stephen:
> On 10/19/2015 3:06 PM, clipka wrote:
>> and Earth's surface
>> accelerating radially from its center at 9.81 m/s^2.
>
> I know it is the psilocybin mushroom season but I thought I was the old
> hippy who had taken mind bending substances (in the past, I might add in
> case PC Plod is listening).
> You have lost it dear friend.
> You have lost it.
Just following Einstein's train of thoughts. No shrooms growing there.
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On 10/19/2015 10:06 PM, clipka wrote:
> Am 19.10.2015 um 19:44 schrieb Stephen:
>> On 10/19/2015 3:06 PM, clipka wrote:
>>> and Earth's surface
>>> accelerating radially from its center at 9.81 m/s^2.
>>
>> I know it is the psilocybin mushroom season but I thought I was the old
>> hippy who had taken mind bending substances (in the past, I might add in
>> case PC Plod is listening).
>> You have lost it dear friend.
>> You have lost it.
>
> Just following Einstein's train of thoughts. No shrooms growing there.
>
Pity cause they would go well with the potatoes in my ears. :-)
> Whatever frame of reference you choose - if it is truly inertial, you'll
> always find the apple (while airborne) moving at constant velocity (or
> remaining at rest, which is a special case thereof),
Assuming that you are not trying to wind me up.
What are your reasons for saying that? If your frame of reference was
the apple I would agree with you. But I was talking about a frame of
reference separate from both of the objects.
> and Earth's surface
> accelerating radially from its center at 9.81 m/s^2.
To me that reads that the Earth's surface (and volume) is expanding.
Something I personally haven't noticed.
Since we are talking about speeds of metres per second I assume we can
dismiss any relativistic effects.
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?
I make it 0.000000000000000000000000167504 m/s^2
> (As long as you
> ignore aerodynamic drag and remain sufficiently close to Earth's surface
> and the apple, that is.)
Granted.
--
Regards
Stephen
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Am 20.10.2015 um 17:24 schrieb Stephen:
>> Whatever frame of reference you choose - if it is truly inertial, you'll
>> always find the apple (while airborne) moving at constant velocity (or
>> remaining at rest, which is a special case thereof),
>
> Assuming that you are not trying to wind me up.
> What are your reasons for saying that? If your frame of reference was
> the apple I would agree with you. But I was talking about a frame of
> reference separate from both of the objects.
Okay, so you agree that the dropping apple's frame of reference is an
inertial one.
Then by definition of what constitutes an inertial frame of reference,
all (sufficiently local) frames of reference in which the apple appears
to be moving at constant speed are inertial, while all in which the
apple appears to be accelerating are non-inertial.
Now no matter what frame of reference you choose, you'll find that
Earth's surface and the apple appear to be accelerating towards each
other; thus any frame of reference in which the apple isn't
accelerating, must have Earth's surface accelerating towards it instead.
>> and Earth's surface
>> accelerating radially from its center at 9.81 m/s^2.
>
> To me that reads that the Earth's surface (and volume) is expanding.
> Something I personally haven't noticed.
That's because it is in equilibrium with the collapse of space.
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.
> 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?
- 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.
- 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.
Yup, that's a mind-bogglingly huge total force acting on Earth's mass.
But electromagnetic forces between atoms under pressure /are/
mind-bogglingly huge.
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On 10/20/2015 10:45 PM, clipka wrote:
> Am 20.10.2015 um 17:24 schrieb Stephen:
>
>>> Whatever frame of reference you choose - if it is truly inertial, you'll
>>> always find the apple (while airborne) moving at constant velocity (or
>>> remaining at rest, which is a special case thereof),
>>
>> Assuming that you are not trying to wind me up.
>> What are your reasons for saying that? If your frame of reference was
>> the apple I would agree with you. But I was talking about a frame of
>> reference separate from both of the objects.
>
> Okay, so you agree that the dropping apple's frame of reference is an
> inertial one.
>
No, I don't. I selected an observational frame of reference where I
could observe both objects, a few posts back.
> Then by definition of what constitutes an inertial frame of reference,
> all (sufficiently local) frames of reference in which the apple appears
> to be moving at constant speed are inertial, while all in which the
> apple appears to be accelerating are non-inertial.
>
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.
> Now no matter what frame of reference you choose, you'll find that
> Earth's surface and the apple appear to be accelerating towards each
> other; thus any frame of reference in which the apple isn't
> accelerating, must have Earth's surface accelerating towards it instead.
>
I agree with that.
>>> and Earth's surface
>>> accelerating radially from its center at 9.81 m/s^2.
>>
>> To me that reads that the Earth's surface (and volume) is expanding.
>> Something I personally haven't noticed.
>
No. I read radially as meaning "Radiating from or converging to a common
centre." Not along a radius.
A bit of a slap in the face with a wet fish. *
Misunderstanding understood.
> That's because it is in equilibrium with the collapse of space.
>
> 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. ;-)
>> 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.
> - 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
> Yup, that's a mind-bogglingly huge total force acting on Earth's mass.
> But electromagnetic forces between atoms under pressure /are/
> mind-bogglingly huge.
>
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.
*
I found this Wiki entry
https://en.wikipedia.org/wiki/Wikipedia:Whacking_with_a_wet_trout
--
Regards
Stephen
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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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