It is impossible to prove the existence of God through scientific measurement. This includes anything which can be seen, heard, felt, tasted or smelled. At best, when endeavoring to convince our fellow man of His existence, we could find out what it would take for him or her to believe. This was the case with 'doubting Thomas':
...Except I shall see in his hands the print of the nails, and put my finger into the print of the nails, and thrust my hand into his side, I will not believe. John 20:25
In this situation, Jesus was able to grant his request. If one claims a miraculous happening is from God, and another sees it for him or herself, this may be enough for the person to believe, but the happening will still not be the kind of proof that can be used in a courtroom.
After Thomas was convinced, Jesus said: "blessed are they that have not seen, and yet have believed." Seeing a miracle is not a necessary prerequisite for a person to believe. If we want to see the people we care about in heaven, the best we can do for them is to make 'proclaiming of the truth' part of everything we do:
Holding forth the word of life; that I may rejoice in the day of Christ, that I have not run in vain, neither laboured in vain. Philippians 2:16
Once adopting this way of life, a believer will find that it is possible to prove God exists, but only to him or herself, and to those willing to believe.
And they went forth, and preached every where, the Lord working with them, and confirming the word with signs following. Amen. Mark 16:20
"To prove the real existence of God (or any other being for that matter), one simply just needs to believe. Believe in your heart.
SmartAZ said: "Stop trying to prove or disprove spiritual things with science." This has NOT happened. No one is trying to prove anything.
Spirits do NOT need to reveal themselves to us in regards to the spirit realm. If we can feel it then it's there.
SmartAZ spouts the word "Christian" and even provides a chapter in Proverbs followed by Romans and Thessalonians. I find it ridiculous for SmartAZ to even mention this since the question clearly states "many religions", not just one. w
Not everyone is Christian. Some are Jewish, Muslim and even Wiccan (like me). Those of different religions believe in different Gods (Muslims believe in Allah, Wiccan's believe in The God (Green Man) and The Goddess (Lady Earth).
How we choose to believe all comes from within. Nothing needs to be seen to prove it."
This was my original comment before I deleted my original account. I stick to my original comment firmly. But I will add on to it.
To believe in the existence of God, one should often pray to God (somehow I doubt SmartAZ even does this). God will come to you to show you God exists.
Furthermore, I should also point out that God is neither male nor female. He is a Spirit.