Everything you believe about yourself and the universe might be an illusion. You perceive yourself as a real entity existing in a universe that began 14 billion years ago, leading to the formation of galaxies, stars, Earth, and ultimately, you. However, what if you are merely a dream of a dead universe? This seemingly bizarre notion could be an inevitable outcome of our most advanced scientific theories about the cosmos.
The concept of time distinguishes the past from the future. Imagine dropping red ink into a glass of water; the ink disperses throughout the water but never spontaneously reconcentrates into a drop. Time appears to flow in the direction of the ink spreading. However, at a microscopic level, molecules move randomly without a defined direction. The arrow of time is not fundamental but a matter of probability. The likelihood of ink molecules spreading is much higher than them concentrating again, making the reverse process extremely improbable.
The universe, born from the Big Bang, has been expanding and evolving. It is akin to a glass of water with ink, possessing an arrow of time. However, due to dark energy, the universe is expanding at an increasing rate, leading to a future where it becomes a dark, vast expanse dominated by dark energy. In about 100 trillion years, the last star will die, and the universe will become a rapidly expanding space devoid of matter. This expansion creates a “cosmic horizon,” beyond which nothing can reach you, effectively turning the universe into a finite glass surrounded by an impassable boundary.
In this scenario, the universe becomes a closed box filled with particles at an extremely low temperature, undergoing random motions. With infinite time, even the most unlikely events can occur, leading to the possibility of spontaneous fluctuations creating planets, galaxies, or even entire universes.
Given infinite time, random particle fluctuations could generate any conceivable arrangement, much like a monkey randomly typing on a typewriter eventually producing the works of Shakespeare. This raises the possibility that our universe is a “pop-up universe,” a random fluctuation rather than a product of the Big Bang. Such universes might contain bizarre anomalies, like dinosaurs riding snails or stars made of blueberries.
In this context, the probability of smaller fluctuations, such as a human brain, is higher than larger ones like galaxies. This leads to the unsettling question: Are you merely a brain, interpreting sensory signals and creating a perceived reality? Could you be a disembodied brain that emerged by chance in a dead universe, complete with knowledge and memories?
While this idea is intriguing, there are loopholes. Dark energy might behave differently than we expect, or the universe might end in a way that prevents the formation of brains. Moreover, if you were a fluctuating brain, the laws of physics you perceive would be random and unrelated to reality. Thus, even if you believe you are a floating brain, there is no solid reason to trust this belief.
Ultimately, this thought experiment highlights the complexities of our theories about the universe. It serves as a fascinating exercise in physics and philosophy, reminding us of the importance of questioning our understanding of reality. So, rest assured, you are likely not a dream of a dead universe.
At Kurzgesagt, we enjoy exploring topics like Boltzmann brains because we believe that engaging with science and philosophy is crucial for making a positive impact on the world. If you’re looking to make a difference, consider exploring resources like 80,000 Hours, a nonprofit organization offering free career advice to help people find fulfilling careers that contribute positively to global issues. Their comprehensive career guide is available online, providing insights into making a meaningful impact.
Conduct an experiment by dropping different colored inks into separate glasses of water. Observe and record how the ink disperses over time. Discuss with your classmates why the ink spreads and why it doesn’t spontaneously reconcentrate. Relate your observations to the concept of the arrow of time and probability.
Divide into groups and research different theories about the universe’s future, such as the Big Freeze, Big Crunch, and Big Rip. Present your findings to the class and engage in a debate about which theory seems most plausible based on current scientific understanding.
Use a computer program to simulate random typing, akin to monkeys on typewriters. Analyze the output to see how often coherent words or sentences appear. Discuss the implications of this randomness in the context of the universe’s potential to generate random fluctuations, like “pop-up universes.”
Engage in a philosophical discussion about the nature of reality. Consider questions like: How do we define reality? Can we trust our perceptions? What are the implications of being a “brain in a vat”? Reflect on how these ideas challenge our understanding of existence.
Research organizations like 80,000 Hours and explore how science and philosophy can contribute to global issues. Create a presentation on how students can make a positive impact in the world through informed career choices and ethical considerations.
Illusion – A false perception or deceptive appearance that can lead to a misunderstanding of reality. – In physics, the bending of light can create an optical illusion, making a straw appear broken when placed in a glass of water.
Reality – The state of things as they actually exist, rather than as they may appear or might be imagined. – Philosophers often debate the nature of reality, questioning whether what we perceive is truly what exists.
Universe – The totality of known or supposed objects and phenomena throughout space; the cosmos. – The study of the universe involves understanding the vast array of galaxies, stars, and planets that exist beyond our solar system.
Time – A continuous, measurable quantity in which events occur in a sequence from the past through the present to the future. – In physics, time is a fundamental dimension that, along with space, forms the fabric of the universe.
Probability – The measure of the likelihood that an event will occur, often expressed as a number between 0 and 1. – Quantum mechanics relies heavily on probability to predict the behavior of particles at the atomic level.
Expansion – The increase in size, volume, or quantity, often referring to the growth of the universe. – The expansion of the universe is evidenced by the observation that galaxies are moving away from each other.
Energy – The capacity to do work or produce change, existing in various forms such as kinetic, potential, thermal, and more. – In physics, energy conservation is a fundamental principle stating that energy cannot be created or destroyed, only transformed.
Fluctuations – Variations or changes in a quantity or condition, often occurring in an unpredictable manner. – Temperature fluctuations in the early universe played a crucial role in the formation of cosmic structures.
Brain – The organ in humans and other animals that is the center of the nervous system, responsible for thought, perception, and control of bodily functions. – Philosophers often explore the relationship between the brain and consciousness, questioning how physical processes give rise to subjective experiences.
Philosophy – The study of fundamental questions about existence, knowledge, values, reason, and reality. – Philosophy encourages critical thinking and questioning, which can lead to a deeper understanding of the principles underlying physics.
