Adriano said..
Ignoring the patronising tone from Carantoc and moving on, I'm not disputing the Einstein Equivalence Principal, that is not in debate - it's fundamental. We're talking about "how it feels" in a real experiment.

The principal deals with the effect on all "bodies". We have a brain and can feel the forces as well as measure the resultant vectors. The assumption by Ian is that inertia and gravity feel exactly the same to a human. I'd like to see his experiment on that.


"The Einstein equivalence principle has been criticised as imprecise, because there is no universally accepted way to distinguish gravitational from non-gravitational experiments (see for instance Hadley[35] and Durand[36])."

So to prove what you're saying is correct, you first need to do a verifiable universally accepted experiment and so far - that's not possible.

(" Completely fundamentally wrong. Gravity works on every atom/subatomic particle with mass of your body. An externally applied force such as a rocket engine firing reacts with one surface of your body. Totally different sensation.")

Also Carantoc, don't forget Ian thinks steel skyscrapers are built with cold formed light steel. We all make fundamental mistakes but ever hold hope that minds can remain open.

Ah, but you've googled on to the outer limits of relativistic physics, to something still being theorised that may or may not be exactly the case in the darkest, most distant, most warped corner of space time. And if there does turn out to be an exception to the principal we'll need something as sensitive as LIGO to detect it.

Curantoc was just trying to help out with the more earthly elevator, gravitron, chop hopping sort of issues.

evlPanda said..

It feels exactly the same because it is exactly the same.

When you accelerate in gravitational field - there are all around you those discovered gravitational waves, space is bend and curved around you, time affected.When you accelerate by your own mean- say rocket engine or centrifuge/carousel that are none of those mentioned above.So it may feel that same, but may not be the same.

evlPanda said..

Adriano said..
Ignoring the patronising tone from Carantoc and moving on, I'm not disputing the Einstein Equivalence Principal, that is not in debate - it's fundamental. We're talking about "how it feels" in a real experiment.

It feels exactly the same because it is exactly the same. Acceleration doesn't act "on one side of your body" because your entire body is accelerating.

Using the 'box' analogy again let's exaggerate to see the effect more clearly. The box is now accelerating at 10g (acceleration is measured in gravity because they're the same) straight up and not only is the force acting on the bottom of the box, and the bottom of your feet, it is also acting on the blood in your brain which is now being pushed to your feet (inertia) making you pass out.

1g of acceleration is, literally, in every way possible, time dilation and all (c is constant), exactly the same as 1g caused by mass.

You're arguing that 1g <> 1g.

Anyway, it trips me out and I find it very interesting.

The pull of a gravitational field is relative to distance from the center of mass. So if you fell sideways into a black hole, the atoms on one side of your body would be ripped from the other due to the differential rate of acceleration. Spaghettification...

Kamikuza said..


The pull of a gravitational field is relative to distance from the center of mass. So if you fell sideways into a black hole, the atoms on one side of your body would be ripped from the other due to the differential rate of acceleration. Spaghettification...

But it would still be the same sensation.

You imply it yourself when you interchange the words acceleration and gravity.



If you stood next to a blackhole and didn't fall into it but experienced its gravity, the gravitational forces would be greater than the strength of your muscles and your head would be pulled to the floor and you would be a horrible sticky mess of bits on the floor.

If you stood in a rocket, in deep space weightless with no gravity, and the rocket accelerated at 30 million g say (I don't know what the average gravitational forces are in blackholes so I'll pick 30 million g), so you accelerated at 300 million metres per second, thus taking you from standing to the speed of light in one second then again your body could not sustain the acceleration and your head would be on the floor and you would be a horrible sticky mess of bits on the floor of the rocket.

Stood still and confined with 30 million g pulling you down, or free to move and accelerating at 30 million g - same sensation.





Perhaps at the sub-sub-sub-atomic level for the milli-milli-sconds that parts of atoms can exist in colliders and perhaps in the bottom of blackholes and perhaps for dark matter (which interacts with gravity but no other force or energy within the universe) and so perhaps at the bottom of a dark matter blackhole ?, then perhaps it might be theoretically different. Hence Adraino can find some quote on the internet that theorises that perhaps, maybe it isn't always and maybe Einstein is not true for all cases (much we now find some of Newton's laws may not be true for all cases at the very very small or very very large scales).

But we don't exist at the sub-sub-atomic level, or at the bottom (if there is one) of a blackhole or as dark matter. In this universe, where we exist, where the energy and matter we interact with exists then it is the same sensation.


And surely we can prove it for us here in this humanly universe. Doesn't Ian K's video of zero G prove it ?

Become weightless in the plane then get somebody to push your feet, accelerating at exactly 9.81m/s/s. You are now experiencing acceleration at 1g but with zero gravity. Do your feet muscles move but your arm bones get ripped off? no, the sensation of being pushed at 1g is the same sensation as standing on the floor of the plane with gravity at 1g. If there is no atmosphere to move through so you have no feeling of wind on your skin and you shut your eyes you wouldn't be able to tell the difference (except you'd bang your head on the end of the plane pretty quick if you were moving).


Same same.

The only thing I would disagree with Ian K and evlpanda is that I do not find it quite interesting. I find it rather geeky and quite boring.

Science for science's sake is for the academics and bohemians. Science for purpose is for the engineers.

Engineers get paid more than scientists. I find that the interesting point.

Kamikuza said..
Same same, yes. But if you accelerated rapidly, the forces aren't applied instantly across your whole body at the same time. There will be measureable time where your feet are experiencing 3 Million G but your head is still at 0 G. If the converse was true, then you'd be breaking the universe: you'd have sent information faster than the speed of light

Only in the case of a change in the rate of acceleration.


If you are accelerating at a fixed rate then your head is accelerating at the same rate as your feet, there is no difference.

And a change in the rate of acceleration would be the same sensation as a change in the rate of gravity

If you were at rest and then commenced accelerating and the rate rapidly changed (so if you go from rest to 2m/s/s to 5m/s/s to 15m/s/s to 100m/s/s in a short period of time) then yes what you say is true. But if you are weightless and then suddenly re-apply gravity going 0g to 2g to 5g to 15g to 100g then same same sensation occurs.

When the people in that plane have gravity re-applied and their arses start "pushing" against the floor then the re-active forces in their bodies must act to equalise the loads imposed by gravity to stop them becoming squished up blobs and that isn't instantaneous either.

Still same same sensation I think.

Don't confuse a change in the rate of acceleration with constant rate of acceleration vs constant rate of gravity



But I still reckon their is an answer to evlpanda's conundrum somewhere. Got to think outside the box (the accelerating / gravity box you are in - so to speak)

Probably something to do with moving through space. If you accelerate you by definition have motion, in gravity you don't necessarily (although you could be in constant motion orbiting an object remaining at equal distance to its mass). If you move through space then hitting cosmic rays and things would knock electrons off your metal box, so it would become more negatively charged. Gravity however it would remain the same.


Perhaps you have to run your hair on your woolly jumper and if the rate that your hair lifts up due to the static charge changes then your are accelerating, but if the rate it lifts up is the same then you are in gravity ??? Or is the argument that any matter outside capable of knocking electrons off as you fly through space is not allowed because you have to be gravity free and so free of all matter outside the box ? Could I say electro-magnetic radiation does not have mass but would still cause a change to the charge of the box if you travelled through it and is present in space regardless of the presence of gravity ?

But what if the box is made of timber though ?

Box is good example.
If we put something in that box and accelerate or apply gravity force
a)only all elements that have mass - may undergo gravity forces
b) everything in this box mass less or not will undergo this acceleration
So being in this closed wooden box you could easy tell if that is acceleration or gravitational force, that cause this Geeees.

Fair enough but it wasn't really my point.

I was only saying 'from standing to speed of light in one second' to highlight the quantum of the forces - in so much as that gravitational loads from blackholes large enough to pull one side of your body from the other would presumably be equivalent to massive, massive accelerations. I don't think I can envisage either even when I try to imagine going around the earth 7 times in one second, which is what my example was seeking to envisage.

But - my point was that the theory is to compare a constant rate of gravitational load to a constant rate of acceleration. You can't say rapid changes in the rate of acceleration give you whiplash but a constant gravitational force doesn't, thus disproving Einstein.

So yes, if you vary the rate of acceleration, like say going up and down and round and round on a roller coaster, this would provide a different sensation to constant gravity.

But, if you could invent a fairground ride that simply applies gravity in different directions and at different rates then you'd have the same sensation as a moving roller coaster, but so much safer as the rider simply stands in one place and if it all goes wrong and everything suddenly fails you don't fly off and plummet to earth. You could even stand inside a box. and hey, guess what - you wouldn't be able to tell the difference. It would be the same sensation.

Kamikuza said..
Same same, yes. But if you accelerated rapidly, the forces aren't applied instantly across your whole body at the same time. There will be measureable time where your feet are experiencing 3 Million G but your head is still at 0 G. If the converse was true, then you'd be breaking the universe: you'd have sent information faster than the speed of light

If you fall into a black hole you aren't accelerating.

edit: I'm wrong here because black holes are infinitely small; there are massive tidal effects. Example holds for less extreme, less infinitely unknowable objects.

Same as right now, we're falling into a mass called Earth. Drop me from a plane and I'll feel zero g because I'm not accelerating through space-time. I'm only accelerating relative to the things that aren't accelerating, such as the air and the ground coming up to meet me.

Right now we're on the ground and we are feeling inertia, which is the same as acceleration, because the ground is pushing us against the shape of space-time which is distorted locally by mass/the Earth.

We call it 'feeling gravity' but it's really acceleration/inertia. It's no different to accelerating in a drag car, time distortion and all (< the trippy bit)

I'll add that that's probably where the confusion above has started; gravity is different to acceleration but the effect, what we call and experience gravity as, is the same. i.e. acceleration isn't a force.

What I really like about this is it doesn't require any equipment, nor any abstract thought; it's not a thought experiment; it's happening to all of us right now.

Macro said...
When you accelerate in gravitational field - there are all around you those discovered gravitational waves, space is bend and curved around you, time affected.When you accelerate by your own mean- say rocket engine or centrifuge/carousel that are none of those mentioned above.So it may feel that same, but may not be the same.

When you accelerate by your own means all of those things happen; space and time bend, relative to the observer (not sure about gravity waves).

Why?
It is all because c, the speed of light, is constant in every direction. Say you're in a rocket traveling at half light speed. If you shine a light from the front of the ship toward the back of the ship the light will not get there in half the time. < read that last sentence again. It can't because the speed of light is constant.

And because speed = distance/time then distance or time has to change, because the speed of light isn't going to change.

On your rocket everything seems normal, however. And it is.

evlPanda said..

Macro said...
When you accelerate in gravitational field - there are all around you those discovered gravitational waves, space is bend and curved around you, time affected.When you accelerate by your own mean- say rocket engine or centrifuge/carousel that are none of those mentioned above.So it may feel that same, but may not be the same.

When you accelerate by your own means all of those things happen; space and time bend, relative to the observer (not sure about gravity waves).

Why?It is all because c, the speed of light, is constant in every direction

Lets consider following thought experiment.

In our wooden box kept on accelerating space ship we have laser beam of lights traveling indefinitely between two mirrors.Now we could have this beam across - perpendicular to our acceleration or along.

We could now apply acceleration varies from zero to billions of trillions Geeees

Question is : Can we observe something at all happening with our beam bouncing of that mirrors ?

Question 2 : If effect of gigaliions G acceleration will be exactly the same as standing in vicinity of black hole that pull you at same G rate ?

evlPanda said..
^

Question 1:
Speed of light is finite so your laser will zig-zag and eventually bounce off the bottom of the mirrors, but only while accelerating.

Now imagine following scenario.

We have the same space ship with wooden box inside and laser beaming from one side to another.

Suppose that our light beam travel across our wooden box at speed 300,000 km/s.

What is the path of our beam of light in those 3 examples :
a) space ship is stationery
b) space ship is not accelerating but already travelling at speed 300,000 km/s
c)space ship is accelerating and enormous rate billions of geeees

If that laser beam will be always able to reach another side of our wooden box ?

evlPanda said..

Kamikuza said..
Same same, yes. But if you accelerated rapidly, the forces aren't applied instantly across your whole body at the same time. There will be measureable time where your feet are experiencing 3 Million G but your head is still at 0 G. If the converse was true, then you'd be breaking the universe: you'd have sent information faster than the speed of light

If you fall into a black hole you aren't accelerating.

edit: I'm wrong here because black holes are infinitely small; there are massive tidal effects. Example holds for less extreme, less infinitely unknowable objects.

Same as right now, we're falling into a mass called Earth. Drop me from a plane and I'll feel zero g because I'm not accelerating through space-time. I'm only accelerating relative to the things that aren't accelerating, such as the air and the ground coming up to meet me.

Right now we're on the ground and we are feeling inertia, which is the same as acceleration, because the ground is pushing us against the shape of space-time which is distorted locally by mass/the Earth.

We call it 'feeling gravity' but it's really acceleration/inertia. It's no different to accelerating in a drag car, time distortion and all (< the trippy bit)

I'll add that that's probably where the confusion above has started; gravity is different to acceleration but the effect, what we call and experience gravity as, is the same. i.e. acceleration isn't a force.

What I really like about this is it doesn't require any equipment, nor any abstract thought; it's not a thought experiment; it's happening to all of us right now.

Macro said...
When you accelerate in gravitational field - there are all around you those discovered gravitational waves, space is bend and curved around you, time affected.When you accelerate by your own mean- say rocket engine or centrifuge/carousel that are none of those mentioned above.So it may feel that same, but may not be the same.

When you accelerate by your own means all of those things happen; space and time bend, relative to the observer (not sure about gravity waves).

Why?
It is all because c, the speed of light, is constant in every direction. Say you're in a rocket traveling at half light speed. If you shine a light from the front of the ship toward the back of the ship the light will not get there in half the time. < read that last sentence again. It can't because the speed of light is constant.

And because speed = distance/time then distance or time has to change, because the speed of light isn't going to change.

On your rocket everything seems normal, however. And it is.

If I drop you from a plane, you'll accelerate at 9.8m/s2 until terminal velocity but you'll feel weightless. If we took away wind resistance, by putting you in the Vomit Comet, you couldn't tell you were moving at all...

Our senses haven't enough fidelity to tell the difference, that's all.

The singularity is very small, the event horizon is not.

evlPanda said..

Remember space-time is bent by the Earth; it's not flat. Satellites travel in a straight line.

Again, it's trippy ****.

Light travel in straight line too, In such case laser beam should follow satellites and do few rounds around our planet...

Kamikuza said..

You're "weightless" when you're in orbit because you are, actually, in free-fall--you're accelerating towards the earth at ~9.8m/s2

It will be quite interesting if one day somebody could build ( spin out faster existing) big wheel, as that one in London or Brisbane.
But instead of slow motion they will rotate fast to provide you acceleration to neglect our gravitational force , and even exceed by same amount.
So for a while we could be completely weight less, then " gravity" return and now we could walk on the ceiling of our cabin, then we becomes very, very heavy on the floor again.