# This is why I believe that the future already exists Source: https://www.youtube.com/watch?v=um6BmPo5PZc Recap page: https://rapidrecap.app/video/um6BmPo5PZc Generated: 2026-01-11T16:04:46.976+00:00 --- ## Quick Overview The speaker argues that Einstein's theory of relativity, which separates past, present, and future into a fixed block universe where all moments exist simultaneously, is a more accurate description of reality than our intuitive perception of time flowing, a concept further complicated by the non-deterministic nature of quantum mechanics. **Key Points:** - Einstein's theory of relativity implies that past, present, and future all exist simultaneously in a fixed 'block universe'. - Our intuitive perception that the present is special and the future is open is misleading, as relativity suggests all moments are equally real. - The concept of simultaneity is relative; different observers moving at different speeds will disagree on whether two events happened at the same time (e.g., the two flashes example). - The speed of light in a vacuum (c) is constant for all inertial observers, defining the boundaries of the light cone, which separates the past and future. - Quantum mechanics introduces indeterminism, meaning we cannot predict the exact outcome of a measurement, only the probability, which conflicts with the determinism implied by the block universe. - The speaker, Sabine Hossenfelder, supports the block universe view, which she finds more consistent than trying to force quantum mechanics into a concept of changing time. - The speaker encourages viewers to support Planet Wild, which funds environmental missions like ocean plastic cleanup and forest restoration, offering a free month for using the code SABINE41. ![Screenshot at 00:50: The speaker drawing a spacetime diagram illustrating how two events \(flashes\) simultaneous for one observer \(you\) are not simultaneous for a moving observer \(your friend\), demonstrating the relativity of simultaneity.](https://ss.rapidrecap.app/screens/um6BmPo5PZc/00-00-50.jpg) **Context:** The speaker, Sabine Hossenfelder (whose book "Existential Physics" is briefly displayed), explores the philosophical implications of Einstein's Special Relativity concerning the nature of time, contrasting the scientific view of a fixed spacetime continuum with our common human experience of a flowing, open future. She uses a spacetime diagram to illustrate how different observers perceive simultaneity differently, and then brings in quantum mechanics to further complicate the discussion on determinism versus probability. ## Detailed Analysis The speaker explains that science, specifically Einstein's theory of relativity, suggests that our perception of time flowing is misleading because the past, present, and future all exist simultaneously in what is called the 'block universe.' This means that for any event, its past and future are just as real as the present moment. She illustrates this using a spacetime diagram where the horizontal axis represents space and the vertical axis represents time. The speed of light (c) is represented by lines at a 45-degree angle relative to the time axis, forming a 'light cone' that dictates what events can causally influence or be influenced by the present moment. She demonstrates that two events (like two flashes of light) that appear simultaneous to a stationary observer will not appear simultaneous to an observer in relative motion, as their 'now' line (a line perpendicular to their worldline) will intersect the space-time axis at different points. This relativity of simultaneity is a core consequence of relativity. Furthermore, she notes that this deterministic view of the block universe clashes with the probabilistic nature of quantum mechanics, which suggests that the future is not entirely determined by the past. The speaker concludes that the block universe model, despite its counter-intuitive nature (like believing the Earth is flat because we cannot see the curve), is the most consistent framework derived from physics, forcing us to accept that our intuitive notion of a flowing present is flawed. She then pivots to promote the work of Planet Wild, citing their environmental missions as a concrete way people can influence the future, even within this fixed spacetime framework. ### The Nature of Time in Relativity - Science suggests time is not flowing but fixed, existing as a block universe where past, present, and future are equally real - Relativity of Simultaneity: Different observers perceive events occurring at the same time differently based on their relative motion. ### Spacetime Diagrams - Demonstrating causality using light cones (lines at 45 degrees) which separate spacetime into regions of the past, future, and elsewhere (spacelike separation). ### Conflict with Quantum Mechanics - The deterministic nature of the block universe conflicts with the inherent unpredictability (probabilistic outcomes) of quantum mechanics measurements. ### Conclusion on Reality - The speaker concludes that the block universe model is the most consistent physical framework, even if it contradicts our intuition that the future is open to change. ### Sponsor Plug - The speaker promotes Planet Wild, highlighting their work on restoring dead soil and saving the Amazon Rainforest, offering viewers a free first month membership using code SABINE41. ![Screenshot at 00:00: The speaker beginning the discussion in front of a bookshelf.](https://ss.rapidrecap.app/screens/um6BmPo5PZc/00-00-00.jpg) ![Screenshot at 00:36: The speaker drawing the initial spacetime diagram axes labeled 'time' and 'space', with the light cone boundaries drawn in black.](https://ss.rapidrecap.app/screens/um6BmPo5PZc/00-00-36.jpg) ![Screenshot at 01:14: The speaker pointing to the diagram while explaining that the light speed is the fastest signal possible.](https://ss.rapidrecap.app/screens/um6BmPo5PZc/00-01-14.jpg) ![Screenshot at 04:38: The speaker labeling the diagram to show the two flashes occurring at the same time for 'You' \(red line\) but at different times for the moving observer 'Your friend' \(green line\).](https://ss.rapidrecap.app/screens/um6BmPo5PZc/00-04-38.jpg) ![Screenshot at 09:54: The speaker concluding that quantum mechanics introduces indeterminism, contrasting with the deterministic block universe model.](https://ss.rapidrecap.app/screens/um6BmPo5PZc/00-09-54.jpg)