Kingdom of God
for a Kingdom to exists it must have a King, with Him his subjects, the people under the domain of his rule. The size of the Kingdom is determined by the authority, he power of the King exercised upon his Kingdom citizens.
God's Dominion in the spirit world:
Spirit realm governs the created realm in existence. It reigns, affects and penetrates to change and govern over the created order. God is Spirit Being, Supreme, The Only Sovereign; for as King (God) of Creation He must have no equal - No other thrones, no other kings, no other titles, powers, rule, dominion and influences can be equal to His. Since He is God immutable unchangeable, for ever the same in substance and power, his sphere is the eternal domain. He reigns from everlasting to everlasting, which Kingdom can not be destroyed. Therefore, His Kingdom is above all kingdoms and spirits in the spirit realm.
God's Dominion in the earth world:
(a) Genesis 1: 1, 'In the beginning God created the heavens and the earth (Genesis 1: 1).
(b) John 1: 1-3, 'In the beginning was the Word (Christ Jesus the Son of God), and the Word was with God, and the Word was God. He was with God in the beginning. Through Him all things were made; without Him nothing was made that has been made. In Him was life, and that life was the light of all mankind.
The sphere of influence God has is: (a) Over all things created, including the earth and galaxies. Everything was created through His spoken Word (namely, Christ Jesus - God's Word incarnated, meaning spirit takes on a body, the physical form and manifested into this creation realm of existence). Nothing that God created was not through Him (God's Word). (b) Every creating thing has a spiritual ear to hear the Creator's voice by creation.
God's Agent: His Church
God's Kingdom is advancing forcefully since the day Jesus Christ died and rose from the dead, ascended into heaven; and promised He shall come back again to gather us to be with Him. Jesus delegated His authority to rule in heaven & on earth to His believers - The Church, to preach His good news of redemption of all creations, to usher in the day of His second coming.
(a) He has delegated His authority to His Church, that whatever we bind on earth, it is bound in heaven. Whatever we loose on earth, it is loosed in heaven. (b) Everything on earth can be changed to pattern after God's model in heaven through His Church exercising authority in Jesus' Name. (c) This change is done through faith - anchored in the promises of God, spoken through faith.