What is gravity?

[Bubbles]

I saw this.

On incorrect scientific ideas.

DAVID DEUTSCH
Quantum Physicist, Oxford; Author, The Fabric of Reality
Surely the most extreme example is the existence of a force of gravity.
It's hard to say when this belief began but it surely predates Newton. It must have existed from the time when concepts such as force were first formulated until the general theory of relativity superseded it in 1915.
Why did scientists hold that belief for so long? Because it was a very good explanation and there was no rival theory to explain observations such as heavy objects exerting forces on whatever they were resting on. Since 1915 we have known the true explanation, namely that when you hold your arm out horizontally, and think you are feeling it being pulled downwards by a force of gravity, the only force you are actually feeling is the upward force exerted by your own muscles in order to keep your arm accelerating continuously away from a straight path in spacetime. Even today, it is hard to discipline our intuition to conceive of what is happening in that way, but it really is.

https://www.quora.com/What-are-some-examples-of-wrong-scientific-beliefs-that-were-held-for-long-periods

Ok, I grew up with the idea that Gravity was a force and that was what I was taught.

Would anyone care to explain what the Quantum Physicist is on about? Because he has lost me......... ( my arm accelerating continuously away in space time??)


Eh?

What is gravity then? Imagination?

[Sriram]

Rose,

There is no 'one true' explanation of reality. Refer to Niels Bohr quotes in the general section.

We only have models formulated using our logic in an effort to explain our experiences. No one knows what gravity is. The General Theory of Relativity is only another effort to explain it....which is in fact at odds with QM.

Like seeing shadows on the walls of the cave (refer Plato). 

Cheers.

Sriram

   

[Bubbles]

 

https://en.m.wikipedia.org/wiki/Blind_men_and_an_elephant

A story from your part of the world I believe 

🌹

[Bubbles]

From the Wiki link

An elephant joke inverts the story in the following way:

Six blind elephants were discussing what men were like. After arguing they decided to find one and determine what it was like by direct experience. The first blind elephant felt the man and declared, 'Men are flat.' After the other blind elephants felt the man, they agreed.

Moral:

"We have to remember that what we observe is not nature in itself, but nature exposed to our method of questioning." - Werner Heisenberg

 

[Bubbles]

I'm intrigued by what answers might be given to the OP 🌹

🌹😜

[trippymonkey]

Are you saying there's a hell of a lot more to EVERYTHING than what our somewhat limited senses can perceive ?
It MUST be true as most things have stayed the 'same' but our 'knowledge' has changed !!!

Cat & pigeons springs to mind.

Nick

[Sriram]

https://en.m.wikipedia.org/wiki/Blind_men_and_an_elephant

A story from your part of the world I believe 

🌹

Yes....the blind men and the elephant is a very valid analogy.  Just as they end up with the picture of a rock, a tree and a snake....we also end up with our own variations and interpretations of reality.   Our ideas may work and could never the less be wrong.

People like Heisenberg and Bohr were such genuine thinkers. True scientists & philosophers! 

[torridon]

I saw this.

On incorrect scientific ideas.

DAVID DEUTSCH
Quantum Physicist, Oxford; Author, The Fabric of Reality
Surely the most extreme example is the existence of a force of gravity.
It's hard to say when this belief began but it surely predates Newton. It must have existed from the time when concepts such as force were first formulated until the general theory of relativity superseded it in 1915.
Why did scientists hold that belief for so long? Because it was a very good explanation and there was no rival theory to explain observations such as heavy objects exerting forces on whatever they were resting on. Since 1915 we have known the true explanation, namely that when you hold your arm out horizontally, and think you are feeling it being pulled downwards by a force of gravity, the only force you are actually feeling is the upward force exerted by your own muscles in order to keep your arm accelerating continuously away from a straight path in spacetime. Even today, it is hard to discipline our intuition to conceive of what is happening in that way, but it really is.

https://www.quora.com/What-are-some-examples-of-wrong-scientific-beliefs-that-were-held-for-long-periods

Ok, I grew up with the idea that Gravity was a force and that was what I was taught.

Would anyone care to explain what the Quantum Physicist is on about? Because he has lost me......... ( my arm accelerating continuously away in space time??)


Eh?

What is gravity then? Imagination?

Pre-Einstein physics regarded gravity as one of the fundamental forces, albeit, an unaccountably weak one. In general relativity however, gravity is merely a consequence of the curvature of spacetime, and not a 'force' at all.

[Sriram]

Rose,

There is no 'one true' explanation of reality. Refer to Niels Bohr quotes in the general section.

We only have models formulated using our logic in an effort to explain our experiences. No one knows what gravity is. The Special Theory of Relativity is only another effort to explain it....which is in fact at odds with QM.

Like seeing shadows on the walls of the cave (refer Plato). 

Cheers.

Sriram

   

Yes...I meant  the General Theory....not the Special Theory. Sorry...corrected.

[Sriram]

Pre-Einstein physics regarded gravity as one of the fundamental forces, albeit, an unaccountably weak one. In general relativity however, gravity is merely a consequence of the curvature of spacetime, and not a 'force' at all.

\




And then we have the Graviton!

https://en.wikipedia.org/wiki/Graviton

[torridon]

Pre-Einstein physics regarded gravity as one of the fundamental forces, albeit, an unaccountably weak one. In general relativity however, gravity is merely a consequence of the curvature of spacetime, and not a 'force' at all.

And then we have the Graviton!

https://en.wikipedia.org/wiki/Graviton

which is conjectural only; gravitons have never been observed or detected.

[Outrider]

I saw this.

On incorrect scientific ideas.

DAVID DEUTSCH
Quantum Physicist, Oxford; Author, The Fabric of Reality
Surely the most extreme example is the existence of a force of gravity.
It's hard to say when this belief began but it surely predates Newton. It must have existed from the time when concepts such as force were first formulated until the general theory of relativity superseded it in 1915.
Why did scientists hold that belief for so long? Because it was a very good explanation and there was no rival theory to explain observations such as heavy objects exerting forces on whatever they were resting on. Since 1915 we have known the true explanation, namely that when you hold your arm out horizontally, and think you are feeling it being pulled downwards by a force of gravity, the only force you are actually feeling is the upward force exerted by your own muscles in order to keep your arm accelerating continuously away from a straight path in spacetime. Even today, it is hard to discipline our intuition to conceive of what is happening in that way, but it really is.

https://www.quora.com/What-are-some-examples-of-wrong-scientific-beliefs-that-were-held-for-long-periods

Ok, I grew up with the idea that Gravity was a force and that was what I was taught.

Would anyone care to explain what the Quantum Physicist is on about? Because he has lost me......... ( my arm accelerating continuously away in space time??)


Eh?

What is gravity then? Imagination?

OK - there are some approximations and poetic license here, it's the general concept I'm trying to convey.

Mass distorts space/time - if you think of  a stretched-out sheet, and then put a weight in the middle, the ball distorts the line of the sheet. (Ironically, due to gravitational effects...)

If you roll a ball-bearing across the sheet, as it approaches the weight it changes path as the distortion of the sheet affects it. That's effectively what happens with mass and gravity, what we think of as a straight line (say, from looking straight down at the sheet from above) is actually bent because of the mass.

When something falls towards a gravitational source it's actually travelling in a straight line through space-time.

O.

[Udayana]

hmmm.. yes, and what is mass? Why does it bend space-time, and what the heck is space-time anyway?

Never mind... I've decided not to let it drag me down...

[Jack Knave]

From the Wiki link

An elephant joke inverts the story in the following way:

Six blind elephants were discussing what men were like. After arguing they decided to find one and determine what it was like by direct experience. The first blind elephant felt the man and declared, 'Men are flat.' After the other blind elephants felt the man, they agreed.

Moral:

"We have to remember that what we observe is not nature in itself, but nature exposed to our method of questioning." - Werner Heisenberg

 

Moral : Avoid elephants!!!

[Jack Knave]

I saw this.

On incorrect scientific ideas.

DAVID DEUTSCH
Quantum Physicist, Oxford; Author, The Fabric of Reality
Surely the most extreme example is the existence of a force of gravity.
It's hard to say when this belief began but it surely predates Newton. It must have existed from the time when concepts such as force were first formulated until the general theory of relativity superseded it in 1915.
Why did scientists hold that belief for so long? Because it was a very good explanation and there was no rival theory to explain observations such as heavy objects exerting forces on whatever they were resting on. Since 1915 we have known the true explanation, namely that when you hold your arm out horizontally, and think you are feeling it being pulled downwards by a force of gravity, the only force you are actually feeling is the upward force exerted by your own muscles in order to keep your arm accelerating continuously away from a straight path in spacetime. Even today, it is hard to discipline our intuition to conceive of what is happening in that way, but it really is.

https://www.quora.com/What-are-some-examples-of-wrong-scientific-beliefs-that-were-held-for-long-periods

Ok, I grew up with the idea that Gravity was a force and that was what I was taught.

Would anyone care to explain what the Quantum Physicist is on about? Because he has lost me......... ( my arm accelerating continuously away in space time??)


Eh?

What is gravity then? Imagination?

Pre-Einstein physics regarded gravity as one of the fundamental forces, albeit, an unaccountably weak one. In general relativity however, gravity is merely a consequence of the curvature of spacetime, and not a 'force' at all.

So we have gravity which we don't really know what it is curving something else which we don't know what it is - space being dimensions i.e. nothing and time (in my view) not existing at all. Well that's clear enough!!!

[jeremyp]

Would anyone care to explain what the Quantum Physicist is on about? Because he has lost me......... ( my arm accelerating continuously away in space time??)

Eh?

What is gravity then? Imagination?

According to Albert Einstein, gravity does not exist as such but is actually curvature in space time. IF you have two marbles in your hand and you let go of one of them, it starts moving.  It is actually moving in a straight line but because we don't perceive the curvature of space-time, we see it as accelerating towards the centre of the Earth.

An analogy may help here: if you look at an online map of the North Atlantic that shows aeroplane flights, you'll notice that flights between London and New York generally take a curved route going way North of what looks like a straight line. That seems crazy until you remember that they are actually flying across the surface of a sphere and taking the "great circle route". In surface-of-a-sphere geometry, the great circles are the straight lines.

Going back to the marbles, if you could perceive the curvature of space-time, it would be obvious that the marble you drop is the one travelling in a straight line. The marble you keep hold of is not travelling in a straight line and by Newton's first law, it must be experiencing a force in order to make it travel in a not straight line. The force is provided by your arm.

[Jack Knave]

Would anyone care to explain what the Quantum Physicist is on about? Because he has lost me......... ( my arm accelerating continuously away in space time??)

Eh?

What is gravity then? Imagination?

According to Albert Einstein, gravity does not exist as such but is actually curvature in space time. IF you have two marbles in your hand and you let go of one of them, it starts moving.  It is actually moving in a straight line but because we don't perceive the curvature of space-time, we see it as accelerating towards the centre of the Earth.

An analogy may help here: if you look at an online map of the North Atlantic that shows aeroplane flights, you'll notice that flights between London and New York generally take a curved route going way North of what looks like a straight line. That seems crazy until you remember that they are actually flying across the surface of a sphere and taking the "great circle route". In surface-of-a-sphere geometry, the great circles are the straight lines.

Going back to the marbles, if you could perceive the curvature of space-time, it would be obvious that the marble you drop is the one travelling in a straight line. The marble you keep hold of is not travelling in a straight line and by Newton's first law, it must be experiencing a force in order to make it travel in a not straight line. The force is provided by your arm.

Yep, that's marbles alright!!!

[Sriram]

Short video on Einsteins space-time curvature.

http://www.sciencedaily.com/videos/91df1b5e1d3f2341d93bbe323aefb76f.htm

Nothing we didn't know from college days ...but still difficult to imagine in 3 D+time.

 

[Bubbles]

Thanks everyone 

[Jack Knave]

I heard recently that gravity is the only force we know that attracts. All the others repel.