So then the Lord Jesus, after he spoke to them, was taken up into heaven and took his seat at the right hand of God. Mark 16:19
What the apostles have witnessed in Jesus taken up to heaven, how they must have been in awe. And to think they also did not have the technology we have today, to try and explain away what went on. They wrote it down for future generations. Not only that but the Church found it's roots in Jesus, where he told his chosen disciples to go out into the world and preach the gospel. Look where the Church is now, from it's meager beginnings, how it has grown.
How the apostles must have felt that day, to see with their eyes Jesus going up in the clouds to heaven. What a glorious day that was for them. And a sad one too, for the time Jesus was with them on earth came to an end. Which marked also a beginning, when they would be filled with the Holy Spirit in a short time to come.
Do any of us ever wonder how we would react were we to witness what the apostles did. To see for ourselves the truth of the Divine, yet blessed are those who believe without seeing.