From a thought experiment point of view (because I believe the universe is at least as old as cosmologists say), I would feel as if I’d taken the blue pill and entered the Matrix. (One of our TV stations had a Matrix marathon yesterday, so I guess that’s what made me think of the blue pill/red pill conundrum.)
A 10,000 year old universe, if proved by science, would force me to set aside all the wonderful things I learned about chemistry in my younger days, and all the fascinating things about the science of dating objects that I learned when I studied art conservation. How could I rely on any of the physics and chemistry of half-lives, for instance, if the science that was presumed to underlie such principles as radioactive decay was just a pile of hooey? How could I rely on what I learned about rates of chemical processes? Would I have to throw differential calculus out the window because our understanding of rates had been so fundamentally flawed? Could I rely anymore at all on what my senses were telling me? On what my scientific instruments were telling me? On what the history of our planet and our universe were telling me about who God is and what matters most in life?
I would have to give up all the bits and pieces of the science and math that have helped me slowly build a positive, reassuring, trusting relationship with God. I would have to give up the idea (so central to my life) of a Mother Father God who models patience, endurance, acceptance, creativity, conscientiousness, openness to change, healing, forgiveness, and love, and in its place I’d have to accept a God who is impatient, fickle, resistant to change, and willing to create a Matrix-like illusory world that no one could really depend on but everyone would be forced to accept.
So I’d be forced into a small theological corner with the Gnostics and their evil demiurge, and for the rest of my life I would feel discouraged, betrayed, fearful, hopeless, unable to trust God’s love, and unable to trust myself.
That’s how my life would change.