“You may have heard that "we are made of stardust" (or "star stuff" if you're Sagan), and this is absolutely true if we measure by mass. All the heavier elements in your body—oxygen, carbon, nitrogen, calcium, etc.—were produced later, either in the centers of stars or in stellar explosions. But hydrogen, while the lightest, is also the most abundant element in your body by number. So, yes, you hold within you the dust of ancient generations of stars. But you are also, to a very large fraction, built out of by-products of the actual Big Bang. Carl Sagan's larger statement still stands, and to an even larger degree: "We are a way for the cosmos to know itself.” LifeUniverseStarsSpaceCosmos Book:The End of Everything Source: The End of Everything
“It also means that cosmology doesn’t really have a well-defined concept of “now.” Or rather, the “now” you experience is highly specific to you, to where you are and to what you are doing. What does it mean to say “that supernova is going off now” if we see the light of it now, and we can watch the star explode now, but that light has been traveling for millions of years? The thing we’re watching is essentially fully in the past, but the “now” for that exploded star is unobservable to us, and we won’t receive any knowledge of it for millions of years, which makes it, to us, not “now,” but the future. When we think of the universe as existing in spacetime—a kind of all-encompassing universal grid in which space is three axes and time is a fourth—we can just think of the past and the future as distant points on the same fabric, stretching across the cosmos from its infancy to its end. To someone sitting at a different point on this fabric, an event that is part of the future to us might be the distant past to them. And the light (or any information) from an event that we won’t see for millennia is already streaming across spacetime toward us “now.” Is that event in the future, or the past, or, perhaps, both? It all depends on perspective.” TimeUniverseSpaceCosmos Book:The End of Everything Source: The End of Everything
“In the meantime, we'll continue on, making new pathc through the woods to see what we might find hiding there. Someday, deep in the unknown wilderness of the distant future, the Sun will expand, the Earth will die, and the cosmos itself will come to an end. In the meantime, we have the entire universe to explore, pushing our creativity to its limits to find new ways of knowing our cosmic home. We can learn and create extraordinary things, and we can share them with each other. And as long as we are thinking creatures, we will never stop asking: "What comes next?” LifeUniverseCosmosAstrophysics Book:The End of Everything Source: The End of Everything
“Whether or not we subscribe to any particular religion or philosophy, it would be hard to deny that knowing our cosmic destiny must have some impact on how we think about our existence, or even how we live our lives. If we want to know whether what we do here ultimately matters, the first thing we ask is: how will it come out in the end? If we find the answer to that question, it leads immediately to the next: what does this mean for us now? Do we still have to take the trash out next Tuesday if the universe is going to die someday? I’ve done my own scouring of theological and philosophical texts, and while I learned many fascinating things from my studies, unfortunately the meaning of existence wasn’t one of them. I may just not have been cut out for it. The questions and answers that have always drawn me in most strongly are the ones that can be answered with scientific observation, mathematics, and physical evidence. As appealing as it sometimes seemed to have the whole story and meaning of life written down for me once and for all in a book, I knew I would only ever really be able to accept the kind of truth I could rederive mathematically.” LifePhilosophyUniverseCosmosThe End Of Everything Book:The End of Everything Source: The End of Everything
“Many other physicists get a little blasé about the vastness of the cosmos and forces too powerful to comprehend. You can reduce it all to mathematics, tweak some equations, and get on with your day. But the shock and vertigo of the recognition of the fragility of everything, and my own powerlessness in it, has left its mark on me. There’s something about taking the opportunity to wade into that cosmic perspective that is both terrifying and hopeful, like holding a newborn infant and feeling the delicate balance of the tenuousness of life and the potential for not-yet-imagined greatness. It is said that astronauts returning from space carry with them a changed perspective on the world, the “overview effect,” in which, having seen the Earth from above, they can fully perceive how fragile our little oasis is and how unified we ought to be as a species, as perhaps the only thinking beings in the cosmos.” UniverseSpaceCosmosOverview Effect Book:The End of Everything Source: The End of Everything
“We know it had a beginning. About 13.8 billion years ago, the universe went from a state of unimaginable density, to an all-encompassing cosmic fireball, to a cooling, humming fluid of matter and energy, which laid down the seeds for the stars and galaxies we see around us today. Planets formed, galaxies collided, light filled the cosmos. A rocky planet orbiting an ordinary star near the edge of a spiral galaxy developed life, computers, political science, and spindly bipedal mammals who read physics books for fun. But what’s next? What happens at the end of the story? The death of a planet, or even a star, might in principle be survivable. In billions of years, humanity could still conceivably exist, in some perhaps unrecognizable form, venturing out to distant reaches of space, finding new homes and building new civilizations. The death of the universe, though, is final. What does it mean for us, for everything, if it will all eventually come to an end?” LifeUniverseSpace Book:The End of Everything: Source: The End of Everything:
“Fortunately, if we need weirdness in physics, we can always rely on the quantum realm to serve us up something good.” Science Book:The End of Everything Source: The End of Everything
“The alternative to recollapse is eternal expansion, which, like immortality, only sounds good until you really think about it.” Science Book:The End of Everything Source: The End of Everything