Does the Past Still Exist?

This paragraph introduces the enigmatic nature of time, both from a personal experience and a physical perspective. It highlights the difference between our everyday perception of time as linear and the revolutionary understanding provided by Albert Einstein, who suggested a more interconnected view of past, present, and future. The paragraph also mentions the upcoming book 'existential physics' for further reading on the topic and emphasizes the shift from viewing time as a universal parameter to considering it a dimension, as proposed by Hermann Minkowski, which redefined the understanding of space-time.

This paragraph delves into the concept of 'now' and how it is not universally agreed upon. It uses the example of viewing a screen to illustrate that the light emitted has not yet reached the viewer, questioning the immediate existence of objects. The discussion moves to the thought experiment by Einstein, which aims to define 'now' operationally. However, with the introduction of a moving observer (Alice), it becomes clear that 'now' is relative and depends on the observer's motion, leading to the concept of the relativity of simultaneity. This challenges the notion of a shared 'now' and introduces the idea that all moments in time may exist equally, a concept known as the block universe.

This paragraph further explores the implications of the relativity of simultaneity, emphasizing that any two non-causally connected events can be made to occur simultaneously for some observer. It introduces the idea of the block universe, where all events throughout time exist simultaneously, and this model remains unchanged by quantum mechanics. The paragraph also discusses alternative views on existence and the slicing of space-time, but these are found to be incompatible with Special Relativity or without observable consequences. The conclusion is that, according to our current understanding, the past exists in the same way as the present.

The final paragraph shifts focus from the theoretical discussion of time to practical learning resources. It promotes a new course on quantum mechanics offered on Brilliant, which covers fundamental concepts like superpositions, entanglement, and the uncertainty principle. The speaker shares their positive experience working with Brilliant's team and encourages viewers to sign up using a provided link for a discount on the annual premium subscription. The paragraph concludes with a thank you note and a promise to see the audience in the next video.