http://news.bbc.co.uk/2/hi/science/nature/6914175.stm
According to research, 99.9% of atom is empty spaced! So how can't we go through objects if all objects are made of atoms?
As you can see that electron in atom is so much smaller than proton but it has very strong negative charge. Electrons are moving around the circumference of nucleus in the speed of light.So when two atoms come into contact, the electrons of each atoms will repel. This is also base on the Pauli Exclusion Principle.
According to a book called
Surface Chemistry of Solid and Liquid Interfaces
By H. Yıldırım Erbil states that: All the different kinds of interactions we have discussed so far have been attractive forces. There must also be some repulsive force, otherwise molecules would collapse. Two types of repulsive force have been considered in the preceeding sections: the Coulomb repulsion between like-charged ions, and the repulsion between atoms and molecules brought too close together which are very short-range. When repulsion occurs between to ions it is generally called Born repulsion. For the second example, the repulsive forces increase very suddenly as two atoms or molecules approach each other very closely, this is due to the repulsion between electron clouds overlapping at very small separations. This repulsion, which increases very steeply with decreasing distance, is due to the Pauli principle, which forbids outer electrons of one molecule from entering occupied orbitals of the other. This repulsion is called hard core or Born repulsion. We will use the name hard core repulsion for the interactions between two uncharged molecules in order to discriminate them from ionic repulsions. These repulsion interactions are quantum mechanical in nature and there is no general expression for their distance dependence, but some empirical potential functions are derived. Ha4rd core repulsions are responsible for the magnitude of the densities of solids and liquids.
