Question: > 
> He is the radiance of the glory of God and the exact imprint of his nature, and he upholds the universe by the word of his power. After making purification for sins, he sat down at the right hand of the Majesty on high (Hebrews 1:3 ESV)
> 
> 
> 

I am interested in the phrase ‘he upholds the universe’
My question is:- How could Christ uphold the universe as a helpless babe and also after he had died before the resurrection.

Answer: 
The simple answer is that He did not uphold the universe as a helpless baby. Hebrews 1:1-3 speaks of His deity/nature BEFORE He was born as a man with a human nature.

In fact, if you read the rest of Hebrews 1 you will discover His own Father acknowledges Jesus as God, vs8. Also at vs10, "And, Thou Lord in the beginning did lay the foundation of the earth and the heavens are the woks of Thy hands.

Moreover Luke 2:11, "for today in the city of David there has been born for you a Savior, WHO IS Christ the Lord." John 17:3,5, "And this is eternal life, that they may know Thee, the only true God, and Jesus Christ WHOM THOU HAS SENT." vs5, "And now, glorify Thou Me together with Thyself, Father, with the glory which I had with Thee BEFORE THE WORLD WAS."

Lastly, Philippians explains at verses 6-8 His pre-existence as God (And so does John 1:1-3) but emptied Himself, taking the form of a bond-servant/man, and being made in the likeness of men, And being found in appearance as a man, He humbled Himself by becoming obedient to the point of death, even death on a cross." And btw, God the Father and God the Holy Spirt did not go anywhere after Jesus died as a man before His resurrection. I think it's important to put things in perspective.
It is impossible to answer this question as we are not told so we cannot know. Indeed, if we knew the answer to this question, we would be God.

Equally mysterious, is the the fact that

* twice in the Gospel of John, we are told the Jesus raised Himself from the dead, John 2:19-21 and 10:17, 18.
* However, we are also told that the Father raised Jesus from the dead as well, Rom 6:4, Gal 1:1, Eph 1:17-20.
* Further, we are also told that the Holy Spirit is the source of life as well, Rom 1:4 & 8:11, 1 Peter 3:18.
* Acts 2:24, 3:15, 4:10, 5:30, 10:40, 13:30, 17:31, Rom 4:24, 1 Cor 15:15, Col 2:20, Heb 13:20, 1 Peter 1:3, 1 Thess 1:10 simply say that “God” raised Jesus without specifying any specific member of the Godhead.

All this simply illustrates the fact that the Godhead acts in complete unison. Just how that occurs we are not told. The same is presumably true of God upholding the universe.