Physic question: Does size of matter matter?

[Kasper Hviid]

I am a bit impressed by how large the objects can be, and how small:

• The smallest object I can create in Algodoo is ½ square-millimeter. (that's 0.005 square-meters)
• The largest object is I can create is something like 2 square-kilometers. (that's 2000 square-meters)

But I wonder how size affects the physics. I mean, if we recreated the entire universe, but with everything just 1000 times larger, would its physics behave the same?

For example, I can make a rubber ball with a radius of 100 meters jumps about just like the normal sized one if we set Gravity Strength: 2000 m/s2 (thus recreating how a small rubber ball is attracted by a much larger object, the earth)

So, is there any rules where the proportions of everything changes the physics behavior? And if so, why?

- Kasper

[tatt61880]

Sorry, I don't understand what you want to know but next information may interest you.

App.scalePowHingeImpulseBreakLimit = 3, default = 3. When scaling x times, this attribute will be scaled by x^this
App.scalePowControllerAcc = 1, default = 1. When scaling x times, this attribute will be scaled by x^this
App.scalePowSpringDamping = 0, default = 0. When scaling x times, this attribute will be scaled by x^this
App.scalePowMotorTorque = 4, default = 4. When scaling x times, this attribute will be scaled by x^this
App.scalePowThrusterForce = 3, default = 3. When scaling x times, this attribute will be scaled by x^this
App.scalePowSpringStrength = 2, default = 2. When scaling x times, this attribute will be scaled by x^this
App.scalePowMotorSpeed = 0, default = 0. When scaling x times, this attribute will be scaled by x^this
App.scalePowAttraction = 1, default = 1. When scaling x times, this attribute will be scaled by x^this

This means that when you scaled object by scale tool, the object's property will be changed automatically.
The automatic change is for not to change behavior of your machine by size effect.
NOTE: gravity won't be changed automatically in current Algodoo.

Edit: I've tried smallest object.
Scene.addBox{size := [1, 1]*0.00000000030642238}
returns a box.
Scene.addBox{size := [1, 1]*0.00000000030642237}
returns WARNING.
(0.306)^2 square-nano-meters.

[Kasper Hviid]

Wow, that's a very small box!

Thanks for the code, I had a feeling that something happened to the data when stuff was being resized, but I didn't knew for sure!

I think my question was mostly about how the physics worked in the real world, which of course also applies to Algodoo. An ant can easily survive falling from 10 times its own length, while a similar drop would damage me. So I got the feeling that the proportions make some sort of basic difference.

But it looks like a Algodoo model behaves the same when I resizes them to be twenty times larger. It seems that I just have to multiply the gravity by twenty, too.

[Ivanlul]

Size does make a difference. I remember watching a lecture by Richard Feynman,however I don't remember which one. He explained that changing the scale of objects would definitely make a difference. Physically, it would make a difference because we can't change the size of atoms, for example. Our world has certain physical constants and if everything was scaled differently it would not behave the same because those constants would not change.