PUT YOUR HAND ON THE BIBLE?
Why do Presidents always put one hand on the Bible when they're sworn in? The Bible is basically a book divided into two distinct versions of God and his relationship to man. In the first part of the Bible, God is always destroying everything. In the second part, The New Testament, God sends his son down to make sure we're on the right path. Jesus doesn't destroy things like his father did. He brings a message of peace and harmony which is a lot better than being turned into a pile of sand.
The reason the President puts his hand on a Bible is because George Washington did it. No one knows why he did it, he just did. John Quincy Adams didn't put his hand on the Bible. Instead he put his hand on a copy of laws of the United States making it clear he was endorsing the separation of church and state. No one knows why Teddy Roosevelt didn't do it.
There is no law that says the President has to put his hand on a Bible. He could put it on a stack of Marvel comics or the New York City Telephone Directory. A President doesn't have to put his hand on anything if he doesn't want to.
The gesture is obviously symbolic and recognizes that yes; a majority of Americans identify themselves as Christians so it's safe to say few people are going to object to the President putting his hand on a Bible. Putting his hand on a Bible also implies that the President is vowing to do as he's sworn to do. It's a promise he says he'll keep or face the wrath of not only the voters but the wrath of God as well.
Just remember that if you're ever elected President, you can put your hand on anything you want to or you can let your arm just hang at your side. Personally I don't think a President should put his hand on any religious document or symbol. The Constitution is clear; the government is prohibited from establishing a state religion.
There's also a National Prayer ceremony which means representatives of all faiths gather together to pray with the President. That's also an inauguration tradition started by George Washington. I'd be interested to know what they're praying for and if any of it comes true.
We're supposed to keep religion separate from the government. The reason is the Founding Fathers wanted to ensure that all religions could be practiced, not just those endorsed by the government.
Not everyone believes in God or the Bible, or any sort of organized religion. Those people are also part of our society and their concerns need to be addressed as well. They're not asking we end the tradition. They just want to make us aware of why we do it.