God is busy testifying through the Spirit to the risen Christ:
"It is the Spirit who testifies, because the Spirit is the truth.
...the testimony of God is this, that He has testified concerning His Son.
10 The one who believes in the Son of God has the testimony in himself; the one who does not believe God has made Him a liar, because he has not believed in the testimony that God has given concerning His Son." (1 John 5:6,9-10 NASB)
He is not busy testifying that the earth is round. But he is supplying faith through his word for us to know and believe that what was made was made from nuttin':
"3 By faith we understand that the worlds were prepared by the word of God, so that what is seen was not made out of things which are visible." (Hebrews 11:3 NASB)
I know that Jesus is speaking to the disciples here, but we can see how we also will testify just as the Spirit testifies:
26 "When the Helper comes, whom I will send to you from the Father, that is the Spirit of truth who proceeds from the Father, He will testify about Me, 27 and you will testify also, because you have been with Me from the beginning." (John 15:26-27 NASB)