John the Baptist wasn't the reincarnation of Elijah. The Bible is clear that someone dies only once.

(Hebrews 9:27-28 NIV) Just as man is destined to die once, and after that to face judgment, {28} so Christ was sacrificed once to take away the sins of many people; and he will appear a second time, not to bear sin, but to bring salvation to those who are waiting for him.

Not only that, Elijah didn't die. Elijah was taken alive in heaven. He appeared to Jesus along with Moses:

(Matthew 17:1-6 NIV) After six days Jesus took with him Peter, James and John the brother of James, and led them up a high mountain by themselves. {2} There he was transfigured before them. His face shone like the sun, and his clothes became as white as the light. {3} Just then there appeared before them Moses and Elijah, talking with Jesus. {4} Peter said to Jesus, "Lord, it is good for us to be here. If you wish, I will put up three shelters--one for you, one for Moses and one for Elijah." {5} While he was still speaking, a bright cloud enveloped them, and a voice from the cloud said, "This is my Son, whom I love; with him I am well pleased. Listen to him!" {6} When the disciples heard this, they fell facedown to the ground, terrified.

And here's where Elijah was taken into heaven:

(2 Kings 2:6-12 NIV) Then Elijah said to him, "Stay here; the LORD has sent me to the Jordan." And he replied, "As surely as the LORD lives and as you live, I will not leave you." So the two of them walked on. {7} Fifty men of the company of the prophets went and stood at a distance, facing the place where Elijah and Elisha had stopped at the Jordan. {8} Elijah took his cloak, rolled it up and struck the water with it. The water divided to the right and to the left, and the two of them crossed over on dry ground. {9} When they had crossed, Elijah said to Elisha, "Tell me, what can I do for you before I am taken from you?" "Let me inherit a double portion of your spirit," Elisha replied. {10} "You have asked a difficult thing," Elijah said, "yet if you see me when I am taken from you, it will be yours--otherwise not." {11} As they were walking along and talking together, suddenly a chariot of fire and horses of fire appeared and separated the two of them, and Elijah went up to heaven in a whirlwind. {12} Elisha saw this and cried out, "My father! My father! The chariots and horsemen of Israel!" And Elisha saw him no more. Then he took hold of his own clothes and tore them apart.

The reason you should pray if you're a scientist is that you're a seeker of truth. Spiritual truth as well as scientific truth.