Can prayers go backward or foreward in time? That is, if I pray for Columbus to find America before his voyage in 1492, will my prayers be effective?
There are some principles to keep in mind:
No sincere prayer for something that is objectively good will ever be wasted. If it is meritorious, it will be used even if it is not used for the specific good you have in mind. For example, if you pray for the repose of the soul of someone who is in heaven or hell then that person either does not need or cannot benefit from that prayer but God can use it for another needy soul in purgatory. So even if God doesn’t use your prayer for Columbus’s journey for that specific good, he can use it for a good to which he wills to apply it. Accepting this is trust in God’s will and we should always pray with this principle in mind.
God is outside of time. Eternity doesn’t have a “beginning” or an “end,” only an ever-present Now.
God is omniscient. He knows what you will pray for throughout your life and may choose to grant grace in anticipation of your prayers that will, in time, take place centuries “later.” This is not an unknown phenomenon. Mary received the grace of the Immaculate Conception in anticipation of Christ’s sacrifice on the cross. In like manner, when our prayers are joined to his sacrifice, our prayers are fruitful by the power of the cross. God may, therefore, by the sacrifice of Christ, anticipate the grace merited by Christians centuries later.
Conclusion: So, yes, it may well be that a prayer you pray tonight for Columbus’s discovery of the Americas might be used by God to assist those long-ago seamen in their journey. We can’t know for sure in this life, but it is a lovely idea to think about.