Resurrection of Jesus

Was Peter telling a crowd of disciples about the resurrection of Jesus?
No, it was a crowd that had gathered after hearing a strange sound and then people speaking in languages that they (the speakers) had never learned (see Acts 2:7-8).

Were they hearing pleasant things from Peter?
He was accusing them of murdering - "you have taken by lawless hands, have crucified, and put to death" (Acts 2:23) - God.

So why did they keep quiet instead of objecting to what Peter was saying about Jesus' resurrection?
They couldn't deny the truth of what he was saying. Jesus' body had disappeared from a guarded tomb (photos) and over five hundred people were running around the region testifying that they had seen the resurrected Jesus: "After that He was seen by over five hundred brethren at once, of whom the greater part remain to the present, but some have fallen asleep" (1 Corinthians 15:6). Think about this for a second. Had there been any doubt about Jesus' resurrection, Peter would have been challenged, if not shouted down, by this crowd, who would have dispersed, dismissing Jesus as just a rabbi who had done and said some amazing things but eventually talked too much and gotten himself killed. But if Jesus is someone who is more powerful than death and not only rose from the dead but actually had prophesied that in advance (see Destroy this Temple, Bronze Snake, A little while), then everything else He had said - including His declaration of being God who came to die to save us from our sins and hell - had to be taken seriously. If Jesus hadn't proven His deity by His resurrection, Christianity would never have made it past this crowd. See Before Abraham was, I AM and John 18.

Would Jesus' disciples have re-assembled without His resurrection?
Consider things also from the perspective of Jesus' disciples. They had followed Jesus around for three years and seen amazing miracles (see Miracles of Jesus). Yet when Jesus was crucified, all but one of them ran off and hid "for fear of the Jews" (John 20:19, see Peace be with you) coming for them as well. But here they were just six weeks later, confidently declaring Jesus' resurrection to a massive crowd of Jews who had called for Jesus to be crucified and who could now arrest and have them crucified as well. Something happened during those six weeks - something so dramatic in fact, that it confirmed their faith in Jesus' deity and words more than all of His miracles that they had witnessed during the previous three years combined.

What could be more convincing than seeing Jesus make the blind see, heal the sick, feed thousands, calm storms, walk on water, etc.?
This time, it wasn't what Jesus did, but what He couldn't do: He couldn't quietly stay dead. During those six weeks, they had seen and talked with the physically resurrected Jesus, who even ate in front of them (see Peace be with you) to prove that they weren't seeing a ghost.

How did His disciples spend the rest of their of their lives?
Not seeking money or comfort, but getting beaten up, chased out, even martyred for telling people to repent from their sins and believe that Jesus rose from the dead to prove that He is God who had died to pay the death penalty due for their sins.

Why would the disciples do that if it weren't true?
Most people don't choose a life of suffering for any cause. A rare few choose a life of suffering for a cause that they believe to be true. Nobody chooses a life of suffering, even unto martyrdom, for a cause that they know to be a lie.

What do the remainders of the disciples' lives indicate about the resurrection of Jesus?
 

What does the resurrection of Jesus mean for the rest of your life?