All science is based on observations whose veracity can’t be completely proven. You may be a brain in a vat and all your life experiences are illusions. All you can do is make sense of the world with respect to your observations and have faith that it is an accurate representation of reality.
Science is still better than religion or plain guessing because in science you are looking for logical consistency. Even if your worldview is false, at least it will be in accordance with itself.