With a CS degree, some planning and luck, you have a good shot at saving FU money while you're still relatively young (let's say before 40). After that, you can

With a CS degree, some planning and luck, you have a good shot at saving FU money while you're still relatively young (let's say before 40). After that, you can take a few years to study physics and see if it is really how you imagined it would be. If it is, great, if it's not - you still have the FU money and can look for fulfillment in other places (incl. going back to your CS career, at which point you should be excellent at, which gives plenty of satisfaction to many people in itself).