Sean M. Carroll
The arrow of time doesn't move forward forever. There's a phase in the history of the universe where you go from low entropy to high entropy. But then, once you reach the locally maximum entropy you can get to, there's no more arrow of time.Collection: History
If time travel were possible, you still wouldn't be able to change the past - it's already happened!Collection: Travel
I don't want to give advice to people about their religious beliefs, but I do think that it's not smart to bet against the power of science to figure out the natural world. It used to be, a thousand years ago, that if you wanted to explain why the moon moved through the sky, you needed to invoke God.Collection: Science
Science isn't just about solving this or that puzzle. It's about understanding how the world works: the whole world from the vastness of the cosmos to the particularity of an individual human life. It's worth thinking about how all the different ways we have to talk about the world manage to fit together.Collection: Science
Even in empty space, time and space still exist.Collection: Space
We ought to teach kids more about the Big Bang and entropy and particles. Every high school graduate should know that everything in the universe is made of a handful of particles. That's not a hard thing to know. But that's not what's emphasized.
The particular aspect of time that I'm interested in is the arrow of time: the fact that the past is different from the future. We remember the past but we don't remember the future. There are irreversible processes. There are things that happen, like you turn an egg into an omelet, but you can't turn an omelet into an egg.
Among advocates for life after death, nobody even tries to sit down and do the hard work of explaining how the basic physics of atoms and electrons would have to be altered in order for this to be true. If we tried, the fundamental absurdity of the task would quickly become evident.
The fact that you can remember yesterday but not tomorrow is because of entropy. The fact that you're always born young and then you grow older, and not the other way around like Benjamin Button - it's all because of entropy. So I think that entropy is underappreciated as something that has a crucial role in how we go through life.
Claims that some form of consciousness persists after our bodies die and decay into their constituent atoms face one huge, insuperable obstacle: the laws of physics underlying everyday life are completely understood, and there's no way within those laws to allow for the information stored in our brains to persist after we die.
Someday, when the ultimate laws of physics are in our grasp, we may discover that the notion of time isn't actually essential. Time might instead emerge to play an important role in the macroscopic world of our experience, even if it is nowhere to be found in the final Theory of Everything.
Naturalism is a counterpart to theism. Theism says there's the physical world and God. Naturalism says there's only the natural world. There are no spirits, no deities, or anything else.
The idea that time is an illusion is an old one, predating any Times Square ball drop or champagne celebrations. It reaches back to the days of Heraclitus and Parmenides, pre-Socratic thinkers who are staples of introductory philosophy courses.
I'm trying to understand how time works. And that's a huge question that has lots of different aspects to it.
I'm trying to understand cosmology, why the Big Bang had the properties it did. And it's interesting to think that connects directly to our kitchens and how we can make eggs, how we can remember one direction of time, why causes precede effects, why we are born young and grow older. It's all because of entropy increasing.
If our local, observable universe is embedded in a larger structure, a multiverse, then there's other places in this larger structure that have denizens in them that call their local environs the universe. And conditions in those other places could be very different. Or they could be pretty similar to what we have here.
A full understanding of what happens in our everyday lives needs to take into account what happened at the Big Bang. And not only is that intrinsically interesting and just kind of cool to think about, but it's also a mystery that is not given much attention by working scientists; it's a little bit underappreciated.
I'm a big believer that science is part of a larger cultural thing. Science is not all by itself.
Something can be real - actually existing, not merely illusory - and yet not be fundamental. Scientists used to think that heat, for example, was a fluidlike substance called 'caloric' that flowed from hot objects to colder ones.
Our conviction that green cheese makes up a negligible fraction of the Moon's interior comes not from direct observation but from the gross incompatibility of that idea with other things we think we know.
There's no reason to be agnostic about ideas that are dramatically incompatible with everything we know about modern science.
Whenever you say you're a physicist, there's a certain fraction of people who immediately go, 'Oh, I hated physics in high school.' That's because of the terrible influence of high school physics. Because of it, most people think physics is all about inclined planes and force-vector diagrams.
One of the tragedies of our educational system is that we've taken this incredibly interesting subject - how the universe works - and made it boring.
Science is a way of getting knowledge. It's a method. It's a method that really relies on making mistakes. We propose ideas, they are usually wrong, and we test them against the data. Scientists do this in a formal way. It's a way that everyone can go through life; that's how we should be teaching science from a very young age.
The fact that the underlying laws of physics are deterministic and impersonal does not mean that at the human level we can't talk about ideas about reasons and goals and purposes and free will.
Naturalism says that we were not put here for any purpose. But that doesn't mean there isn't such thing as purpose. It just means that purpose isn't imposed from outside. We human beings have the creative ability to give our lives purposes and meanings.
The simplest way out of the puzzle of time travel is to say that it can't be done. That's very likely the right answer. However, we don't know for sure.
The weird thing about the arrow of time is that it's not to be found in the underlying laws of physics. It's not there. So it's a feature of the universe we see, but not a feature of the laws of the individual particles. So the arrow of time is built on top of whatever local laws of physics apply.
I've loved physics from a young age, but I've also been interested in all sorts of big questions, from philosophy to evolution and neuroscience. And what those fields have in common is that they all aim to capture certain aspects of the same underlying universe.
I think it's important that science just doesn't stay within narrow boundaries.
People don't realize how many aspects of our lives are touched in one way or another by not just the discoveries, the technological breakthroughs, but the process of science.
We tend to talk about the world in a myriad of ways - a microscopic world of elementary particles, a biological world of organisms and evolution, a social world of morality and meaning. But it's all the same underlying world. That's the underlying theme of 'The Big Picture.'
As we get older, we tend to grow quite fond of the planets of belief we have constructed for ourselves. We build elaborate defense mechanisms to ward off attacks from competing ideas or new data. The system makes us comfortable but resistant to change, no matter how much change might be called for.
The asymmetry of time, the arrow that points from past to future, plays an unmistakable role in our everyday lives: it accounts for why we cannot turn an omelet into an egg, why ice cubes never spontaneously unmelt in a glass of water, and why we remember the past but not the future. And the origin of the asymmetry we experience can be traced all the way back to the orderliness of the universe near the big bang. Every time you break an egg, you are doing observational cosmology.Collection: Time
Scientifically speaking, the existence of God is an untenable hypothesis. It's not well-defined, it's completely unnecessary to fit the data, and it adds unhelpful layers of complexity without any corresponding increase in understanding.Collection: Data
We are looking for a complete, coherent, and simple understanding of reality. Given what we know about the universe, there seems to be no reason to invoke God as part of this description.Collection: Simple
The world is not magic - and that's the most magical thing about it.Collection: Magic
We are not important to the universe. That's the bad news.Collection: Important
Just the idea that we, these little collections of atoms and molecules, are part of the world, but a part that can look at the rest of the world and figure it out in a self-referential way, is kind of breathtaking.Collection: Atheist
There is no such thing as outside the universe, as far as we can tell.Collection: Universe
All the stuff we've ever seen in the laboratory, all the kinds of particles and matter and energy, that only makes up 5 percent of our universe.Collection: Energy
We are not significant on the cosmic scale.Collection: Significant
God is not described in equations.Collection: Equations
We seek an understanding of the laws of nature and of our particular universe in which everything makes sense to us. We do not want to be reduced to accepting the strange features of our universe as brute facts.Collection: Law
Nothing in the fact that there was a first moment in time necessitates that an external something is required to bring the universe about at that moment.Collection: Firsts
The speed of time is 1 hour per hour, no matter what else is going on in the universe.Collection: Matter
There's no verbs before time itself exists, right? There's no popping into existence, there's no fluctuating, there's no quantum mechanical craziness, there is literally nothing.Collection: Verbs