Total Posts:9|Showing Posts:1-9
Jump to topic:

Do centres if gravity 'exist';

kp98
Posts: 729
Add as Friend
Challenge to a Debate
Send a Message
7/19/2015 6:21:10 AM
Posted: 1 year ago
Well, do they? If so, what are they made of? If not, why do we speak of them?
I say they don't exist - at least not for 'all values of 'exist".'
RuvDraba
Posts: 6,033
Add as Friend
Challenge to a Debate
Send a Message
7/19/2015 9:25:04 AM
Posted: 1 year ago
At 7/19/2015 6:21:10 AM, kp98 wrote:
Well, do they? If so, what are they made of? If not, why do we speak of them?

A centre of mass has an objective definition -- meaning, it's a definition which if applied consistently, produces identical results.

That definition has a constructive, objective use, meaning, if we share the definition, we can all expect to gain the same nontrivial benefit thereby.

So as an idea, centre of mass:
* is more precisely and objectively defined than a social idea like 'personhood' say;
* has canonical constructive uses, as 'personhood' need not.

So if we felt 'centre of mass' was too abstract a concept to be useful, we'd also have cause to challenge the word 'person' on even stronger grounds.
Mhykiel
Posts: 5,987
Add as Friend
Challenge to a Debate
Send a Message
7/19/2015 9:37:55 AM
Posted: 1 year ago
At 7/19/2015 6:21:10 AM, kp98 wrote:
Well, do they? If so, what are they made of? If not, why do we speak of them?
I say they don't exist - at least not for 'all values of 'exist".'

They don't exist per se.

It is a word describing the result of a measurement and calculation.

take the word "Cosine" do cosigns exist? The calculated value exists but the cosign itself is nothing material, it is identifying that which is described as the side divided by the hypotenuse.

Technically the calculated value doesn't exist either. It is a ratio. Another value that is descriptive of something.

So the center of gravity is the center found by measuring the whole and dividing by 2. ((the equation is not really X/2 but you get the point)).
RuvDraba
Posts: 6,033
Add as Friend
Challenge to a Debate
Send a Message
7/19/2015 11:06:58 AM
Posted: 1 year ago
At 7/19/2015 9:35:46 AM, kp98 wrote:
You managed to avoid saying yes or no....

Yes, that was deliberate, KP. I think it's like the philosophical question that mathematicians sometimes ask: 'Do numbers exist'?

You can argue it more than one way, and people do. It matters a fair bit, since if numbers exist then maths is a science; if they don't, then it might be more of a philosophy, and this distinction might affect the weight we give its results.

I have a friend who's a senior researcher in linguistics, and he thinks of certain ideas as linguistic constructs: meaning, they're abstractions that help us order and make sense of our world. We don't adopt them because they exist objectively, but because we're more functional with them than without.

I think he'd view an idea like 'centre of gravity' as a linguistic construct. Another linguistic construct is the biological taxonomy -- ideas like clade, genus, species. Or the Dewey Decimal system used by many libraries to order books. Or (say) the Metric or Imperial systems of measurements -- while they're definable objectively and physically, they are themselves abstractions.

It has been argued by sociologists that nationhood too is a linguistic construct -- and I suggested above that personhood may be too.

There are an awful lot of these, and the reason I posted as I did was to invite you to consider just how full our language and thought are with such ideas, and to think through what weight we need to give them.

I don't think it's fair to call all of them subjective or arbitrary, but are abstractions of objective concepts real? And what if they're not?
Skepsikyma
Posts: 8,280
Add as Friend
Challenge to a Debate
Send a Message
7/19/2015 11:15:59 AM
Posted: 1 year ago
At 7/19/2015 6:21:10 AM, kp98 wrote:
Well, do they? If so, what are they made of? If not, why do we speak of them?
I say they don't exist - at least not for 'all values of 'exist".'

I think Feynman tackles this sort of idea pretty well.
"The Collectivist experiment is thoroughly suited (in appearance at least) to the Capitalist society which it proposes to replace. It works with the existing machinery of Capitalism, talks and thinks in the existing terms of Capitalism, appeals to just those appetites which Capitalism has aroused, and ridicules as fantastic and unheard-of just those things in society the memory of which Capitalism has killed among men wherever the blight of it has spread."
- Hilaire Belloc -
JMcKinley
Posts: 314
Add as Friend
Challenge to a Debate
Send a Message
7/20/2015 7:01:58 AM
Posted: 1 year ago
I can tell you from an engineering standpoint they certainly exist, and have very real applications. If you have a mass, then there is by definition a center of mass. Its a physical point in space relative to the mass.

Comparatively, if you have a finite line, no matter how long, it has a midpoint. This midpoint exists. It is a physical point in space.

The only time these things get fuzzy is if we approach infinity. An infinite line can not be said to have a midpoint. An infinite mass can not be said to have a center of mass.
Floid
Posts: 751
Add as Friend
Challenge to a Debate
Send a Message
7/20/2015 7:50:49 AM
Posted: 1 year ago
At 7/19/2015 6:21:10 AM, kp98 wrote:
Well, do they? If so, what are they made of? If not, why do we speak of them?
I say they don't exist - at least not for 'all values of 'exist".'

Yes, centers of gravity exist. They are not made of anything as the term refers to a specific location.

If you say centers of gravity don't exist, then I would suggest no flying in an airplane, because if didn't exist that airplane would be aerodynamically unstable and crash.
kp98
Posts: 729
Add as Friend
Challenge to a Debate
Send a Message
7/20/2015 7:54:32 AM
Posted: 1 year ago
In the science forum CoGs exist no problem, but if this was the philosophy thread things would be bit more complicated!

Does an object have a centre of gravity, or does it (under appropriate conditions) behave as if it has a centre of gravity? If it has a CoG of gravity, will you kindly remove it from the object and hand it to me? If not, what's stopping you?

One interpretation of why you can't extract the CoG from an object and hand it someone is that CoGs don't actually exist - a CoG is a mathematical trick for calculation purposes. They don't actually exist - it's just useful to pretend they do.

Nonsense to an engineer, but engineers make very bad philosophers - but not as bad as the engineers philosophers would be!