Since ancient times, philosophers, prophets, and mystics alike have sought to explain the way the world works, the meaning of life, the origin of the universe, and the nature of life after death. The prophets claim to know from the divine revelations provided to them by a supreme and infallible god. The mystics claim to know through transcendental experience and supernatural visions. The philosophers claim to know through a process of logical deduction and critical reasoning, sometimes mixed with observation and mathematical abstractions. Of these, the philosophers are closest to being scientists, guilty only of speculation without experimental verification. Even so, some ancient philosophers can be described as early scientists or "proto-scientists"--philosophers such as Thales, Pythagoras, Aristotle, Aristarchus, and Hypatia of Alexandria, who took the time to seek rational explanations for phenomenon they observed in nature.
Science is simply a process to investigate natural phenomena in the universe by means of empirical observation, experimentation, formulating theories, and testing outcomes predicted by those theories. The first true scientists, by this definition, emerged between the 11th and 13th centuries CE with men such as Ibn al-Haytham, Abu Rayhan al-Biruni, Shen Kuo, and Roger Bacon. However, the scientific revolution is generally held to have begun with the Renaissance and the pioneering work of Nicolaus Copernicus, Galileo Galilei, Johannes Kepler, Tycho Brahe, Robert Hooke, Christian Huygens, and Giordanio Bruno, many of whom were declared heretics by the Church and suffered dearly as a result. By the end of 17th century, such unjust persecution had largely diminished, Renaissance science reached its epitome with the Principia Mathematica and Opticks of Sir Isaac Newton. The 18th and 19th centuries saw ever greater scientific progress and countless new discoveries, including the taming of electricity, the measurement of the speed of light, the development of the periodic chart of elements, the establishment of the laws of thermodynamics, Dawrin's Origin of Species, and the general acceptance of the truly astronomical scale of the universe. The modern age of science began at the dawn of the 20th century marked by the revolutionary tide propelled by Einstein and carried foreword by nuclear physics, quantum mechanics, and cosmology.
We know what we know because we can observe, measure, hypothesis, test, formulate theories and counter-theories, test those theories, derive conclusions, and find new questions to ask. That is the scientific method, and it has operated flawlessly for thousands of years (even before begin defined as such) providing insights to the natural world and the universe that grows steadily more accurate with every passing generation. As far as we know, there exists no superior source of verifiable information about nature and the universe than what science provides. So-called "revealed knowledge" is at best a leap of insight, or at worse a flight of fancy, and unless it can be verified through scientific inquiry it is ultimately meaningless to our existence, providing nothing to further our biological, intellectual, and technological development. If anything, "revealed knowledge" has a tendency to hold us back, especially when it takes the form of deeply entrenched dogma.
Does this mean we should all abandoned religion and become atheists? Advocates of atheism would certainly argue "yes", but hopefully even they would conceded that the best course of action is simply to accept all that science reveals as factual and true; and as for that which science cannot prove, one may choose to believe as long as it does not contradict the facts of science.
But one may also argue that the facts of science are ever changing. What we knew about science 1000 years ago is virtually obsolete today, replaced by new science which, a 1000 years hence, will likely also be obsolete. Why then should we trust science? In short, science offers us the best possible picture of the true nature of the universe within the limits of our technology at any given moment in history. Just because our knowledge of the universe continues to grow and evolve does not mean we should not trust or accept our present understanding. Science is a process of learning, investigation, and discovery, and it would be a sorry process indeed if it were to simply stop. With each new discovery made with the tools of scientific inquiry, we gain a better understanding of the Cosmos and our place in it.
Science has shown us that we hold a special place in the Cosmos. As the only technological species on our plant, we have a special responsibility to our world, to ourselves, and to all other life forms on on planet. For the first time in 4.5 billion years, we are the first living creatures on Earth possessing the capability of space travel. This not only gives us the ability to avert the kind of disaster that caused the extinction of the dinosaurs, but we also possess the ability to "leave the cradle of Earth", so to speak, and bring life to the stars and planets beyond our home. We only need to embrace that future with fearless determination, and voyage across the heavens as we once voyaged across the seas, exploring, discovering, and revering with awe everything the universe has to offer.