how realistic is unity3D's physics supposed to be ?

So i've been trying to get into unity3D, to see if it's any good.

i'm trying to make a pinball machine just to test things out and see how everything works.

But i fairly quickly came to the point where i discovered that if i make a little ball with realLife size/scale (0.03) it just sinks into the underlying object..

why?

Now i read in some other q&a that is has something to do with the physics engine using float math. but shouldn't things be normal if i also rescale the cube on which the little ball is landing to the same small scale?

Am i not supposed to use real life scale ?

is unity3D just not made to use some marble sized balls ?

I seriously wanna make games with marbles.. should i just give up on unity3D or am i doing things wrong ?

You may want to tweak the settings in the Physics Manager:

http://unity3d.com/support/documentation/Components/class-PhysicsManager.html

Specifically, I suspect you need to lower the `Min Penetration for Penalty` setting.

Physics are fine really , i myself havent encountered your problem so can you upload a screenshot or the scene? Maybe you could switch the collision detection to continuous dynamic?

I've had problems in the past with a small ball not colliding with certain objects correctly. You may want to increase the FixedTimeStep value in your projects physics properties.