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Question about Basics of Gravity


tylers100
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- Question

"Gravity is the weakest of the four fundamental interactions of physics, approximately 1038 times weaker than the strong interaction, 1036 times weaker than the electromagnetic force and 1029 times weaker than the weak interaction. As a consequence, it has no significant influence at the level of subatomic particles.[4] In contrast, it is the dominant interaction at the macroscopic scale, and is the cause of the formation, shape and trajectory (orbit) of astronomical bodies."
link: https://en.wikipedia.org/wiki/Gravity

It seems to me that the gravity or gravitation adds or builds up in interaction from microscopic (e.g. sub-atomic particles) to macroscopic level (stars, planets, etc?) the more it is depended by mass?

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7 hours ago, tylers100 said:

- Question

"Gravity is the weakest of the four fundamental interactions of physics, approximately 1038 times weaker than the strong interaction, 1036 times weaker than the electromagnetic force and 1029 times weaker than the weak interaction. As a consequence, it has no significant influence at the level of subatomic particles.[4] In contrast, it is the dominant interaction at the macroscopic scale, and is the cause of the formation, shape and trajectory (orbit) of astronomical bodies."
link: https://en.wikipedia.org/wiki/Gravity

It seems to me that the gravity or gravitation adds or builds up in interaction from microscopic (e.g. sub-atomic particles) to macroscopic level (stars, planets, etc?) the more it is depended by mass?

Which force predominates depends upon the distance the interaction operates.

That is often stated at bit more vaguely as the scale.

 

When considered as 'forces' the scale or distance order ( not strength order)  is weak < strong < electromagnetic < gravity.

 

So

the weak force predominates at the very shortest scales, smaller than nuclear particles,

The strong force predominates at scales the size of the nucleus

The electromagnetic force predominates at scales the size of a molecule (ie bigger than an atom)

The gravitational force predominatres at the size of galaxies.

This Wiki article has readable presentations of all this and more.

Note the key word is interactions, not forces

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

 

At scales the size of the nucleus and smaller

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9 hours ago, tylers100 said:

It seems to me that the gravity or gravitation adds or builds up in interaction from microscopic (e.g. sub-atomic particles) to macroscopic level (stars, planets, etc?) the more it is depended by mass?

Yes. Each particle in some collection attracts in proportion to its mass, and the total force is the sum of these individual forces. It’s always attractive, so there is no cancellation 

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@studiot and @swansont, thanks for replying.

I understand a bit better about the distance of interactions, but after reading some on fundamental interaction wiki page.. I'm a bit overwhelmed by it at this moment, but one thing caught my attention, this snippet of paragraph on the fundamental interaction wiki page:

"An even bigger challenge is to find a way to quantize the gravitational field, resulting in a theory of quantum gravity (QG) which would unite gravity in a common theoretical framework with the other three forces. Some theories, notably string theory, seek both QG and GUT within one framework, unifying all four fundamental interactions along with mass generation within a theory of everything (ToE)."
link: https://en.wikipedia.org/wiki/Fundamental_interaction

Quantize = Requires an understanding of quantum mechanics in order to quantize gravity (transition from classical to QM) , but I do not fully understand QM (e.g. mathematics).

Still, I feel a drawing or pulling to the gravity topic as part of science subject. I feel like jumping to it.

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53 minutes ago, tylers100 said:

@studiot and @swansont, thanks for replying.

I understand a bit better about the distance of interactions, but after reading some on fundamental interaction wiki page.. I'm a bit overwhelmed by it at this moment, but one thing caught my attention, this snippet of paragraph on the fundamental interaction wiki page:

"An even bigger challenge is to find a way to quantize the gravitational field, resulting in a theory of quantum gravity (QG) which would unite gravity in a common theoretical framework with the other three forces. Some theories, notably string theory, seek both QG and GUT within one framework, unifying all four fundamental interactions along with mass generation within a theory of everything (ToE)."
link: https://en.wikipedia.org/wiki/Fundamental_interaction

Quantize = Requires an understanding of quantum mechanics in order to quantize gravity (transition from classical to QM) , but I do not fully understand QM (e.g. mathematics).

Still, I feel a drawing or pulling to the gravity topic as part of science subject. I feel like jumping to it.

Perhaps I should have noted before that the Wiki article refers to other models/explanations of force -  the article is fairly comprehensive.

That is why I said 'force' and why I referred to 'interactions'.

I suggest you get a good hold on the simple everday idea of force before looking at, for instance, the exchange particle model.

Remember they are all models, none are perfect.

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On 10/17/2021 at 12:33 PM, studiot said:

Perhaps I should have noted before that the Wiki article refers to other models/explanations of force -  the article is fairly comprehensive.

That is why I said 'force' and why I referred to 'interactions'.

I suggest you get a good hold on the simple everday idea of force before looking at, for instance, the exchange particle model.

Remember they are all models, none are perfect.

Yep. Except the fact that this thread is focused specifically on the basics of gravity. You interjected into and jumped to some forces or other interactions, leading me to re-shift my focus to these which is not what I originally intended.

 

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17 minutes ago, tylers100 said:

Yep. Except the fact that this thread is focused specifically on the basics of gravity. You interjected into and jumped to some forces or other interactions, leading me to re-shift my focus to these which is not what I originally intended.

 

This might help

beiser2.thumb.jpg.6408c190491fce995906d5ea0dbd2943.jpgbeiser3.thumb.jpg.2fcfcb5cd9cd094d90e5204d6a2da247.jpg

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On 10/17/2021 at 11:27 AM, tylers100 said:

It seems to me that the gravity or gravitation adds or builds up in interaction from microscopic (e.g. sub-atomic particles) to macroscopic level (stars, planets, etc?) the more it is depended by mass?

Mass is what usually comes to mind first - but it’s important to realise that other forms of energy also have gravitational effects. Examples are pressure, stresses and strains within materials; electromagnetic fields; and even the gravitational field itself acts (at least in some sense) as its own source. Hence, gravity is a lot richer and more complicated than the simplified picture most of us are taught in school.

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1 hour ago, Markus Hanke said:

Mass is what usually comes to mind first - but it’s important to realise that other forms of energy also have gravitational effects. Examples are pressure, stresses and strains within materials; electromagnetic fields; and even the gravitational field itself acts (at least in some sense) as its own source. Hence, gravity is a lot richer and more complicated than the simplified picture most of us are taught in school.

Would you say that this is the reason why gravity is modelled in 2 ways - spacetime warping and/or particle exchange?

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45 minutes ago, Intoscience said:

Would you say that this is the reason why gravity is modelled in 2 ways - spacetime warping and/or particle exchange?

It's three, really - gravitational field, warping, and particle exchange. 

The former two are classical, that latter is quantum, and in that regard this is no different than electromagnetism having classical and quantum models.  

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6 minutes ago, swansont said:

It's three, really - gravitational field, warping, and particle exchange. 

The former two are classical, that latter is quantum, and in that regard this is no different than electromagnetism having classical and quantum models.  

Ok, thanks

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  • 4 weeks later...
On 10/25/2021 at 7:06 AM, Intoscience said:
On 10/25/2021 at 5:38 AM, Markus Hanke said:

Mass is what usually comes to mind first - but it’s important to realise that other forms of energy also have gravitational effects. Examples are pressure, stresses and strains within materials; electromagnetic fields; and even the gravitational field itself acts (at least in some sense) as its own source. Hence, gravity is a lot richer and more complicated than the simplified picture most of us are taught in school.

Would you say that this is the reason why gravity is modelled in 2 ways - spacetime warping and/or particle exchange?

No, but it is the reason gravity is not renormalizable and can't be easily persuaded to play well with Quantum Field theory.

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