Apr 28, 2026 03:26 PM
SABINE HOSSENFELDER
https://youtu.be/um6BmPo5PZc
VIDEO EXCERPTS: If science has taught us one thing, it's that our perception of reality can be extremely misleading. The earth isn't flat. Solids don't fill space and no one looks like they do on Instagram. That the future somehow different from the past is another such quirk of human perception that doesn't correspond to reality. At least that's what I think. And today I want to explain why.
In a nutshell, the reason is that Einstein's theory of general relativity tells us that the future, present, and past are really all the same thing. They belong together to one common entity, spacetime, which just is. It doesn't come into being. It's there, has always been there, and will always been there in its entirety. In Einstein's theory, you can't separate the past from the present and the future. It's not logically possible. And this theory is experimentally very well confirmed.
This is why I think we can't just discard this consequence. It's like insisting that the earth is flat because we can't see the curve, instead of denying it because it doesn't agree with our personal experience.
We should be trying to understand what it means. This is an argument in three steps.
The first step is the question of what we mean when we say that something exists...
[...] The second step is then to factor in Einstein's relativity.,,,
[...] now let's look at step three...
[...] But there could be an observer at any distance from you. Each of whom has their own now. None of those nows is any better than any other. So this means every moment your past, present or future is now for someone somewhere. If you take these three steps together, then you arrive at the following conclusion.
Once you identify that what exists with a present moment, then Einstein's theory forces you to accept that all moments exist in the same way. This perplexing consequence of Einstein's relativity has been dubbed the block universe by physicists. In this block universe, the past still exists and the future already exists.
[...] In case you think this sounds pretty crazy, it's actually a standard argument that physics professors throw at undergrad students and then just let the students cope with the consequences because how do we make sense of this? What does it mean that the past, present, and future all exist the same way? Yes, I've spent three decades trying to wrap my head around this.
I think that for one thing it means that our past selves still exist the same way as this present self. It's just that our past selves are all disconnected from each other. They can't communicate. And our future selves also already exist. But doesn't this also mean that we can't change anything about the future? Depends on what you mean by change.
The future will be whatever is the consequence of today. But these consequences depend on what you and the matter around you do. This means that the future does depend on what you will do. It depends on what information you take away from this video and how this affects your thoughts and your actions.
The opposite is also the case by the way. The present depends on the future in the same way that the future depends on the present. It's just that we don't think about it this way. Einstein's theories really are strange, and I don't think we've yet entirely appreciated how strange they are.
[...] You see, so far what I told you was all Einsteinian physics, which doesn't know anything about quantum physics. If you take into account quantum physics, the argument becomes more complicated...
[...] Once you've measured the particle, you can't say exactly what the wave function was. You can only say it was more likely to have been this instead of that. And this sort of indeterminism is entirely compatible with the block universe. It's not deterministic, okay? But it still doesn't tell you which moment is now. To put this differently, there's no such thing as a now in the mathematics of quantum physics. Not unless you actually change something about the maths.
This is why I think the block universe is how nature really works and that our perception of the present moment being somehow special is just false. Like the idea that the earth is flat...
This is why I believe the future already exists ... https://youtu.be/um6BmPo5PZc
https://www.youtube-nocookie.com/embed/um6BmPo5PZc
https://youtu.be/um6BmPo5PZc
VIDEO EXCERPTS: If science has taught us one thing, it's that our perception of reality can be extremely misleading. The earth isn't flat. Solids don't fill space and no one looks like they do on Instagram. That the future somehow different from the past is another such quirk of human perception that doesn't correspond to reality. At least that's what I think. And today I want to explain why.
In a nutshell, the reason is that Einstein's theory of general relativity tells us that the future, present, and past are really all the same thing. They belong together to one common entity, spacetime, which just is. It doesn't come into being. It's there, has always been there, and will always been there in its entirety. In Einstein's theory, you can't separate the past from the present and the future. It's not logically possible. And this theory is experimentally very well confirmed.
This is why I think we can't just discard this consequence. It's like insisting that the earth is flat because we can't see the curve, instead of denying it because it doesn't agree with our personal experience.
We should be trying to understand what it means. This is an argument in three steps.
The first step is the question of what we mean when we say that something exists...
[...] The second step is then to factor in Einstein's relativity.,,,
[...] now let's look at step three...
[...] But there could be an observer at any distance from you. Each of whom has their own now. None of those nows is any better than any other. So this means every moment your past, present or future is now for someone somewhere. If you take these three steps together, then you arrive at the following conclusion.
Once you identify that what exists with a present moment, then Einstein's theory forces you to accept that all moments exist in the same way. This perplexing consequence of Einstein's relativity has been dubbed the block universe by physicists. In this block universe, the past still exists and the future already exists.
[...] In case you think this sounds pretty crazy, it's actually a standard argument that physics professors throw at undergrad students and then just let the students cope with the consequences because how do we make sense of this? What does it mean that the past, present, and future all exist the same way? Yes, I've spent three decades trying to wrap my head around this.
I think that for one thing it means that our past selves still exist the same way as this present self. It's just that our past selves are all disconnected from each other. They can't communicate. And our future selves also already exist. But doesn't this also mean that we can't change anything about the future? Depends on what you mean by change.
The future will be whatever is the consequence of today. But these consequences depend on what you and the matter around you do. This means that the future does depend on what you will do. It depends on what information you take away from this video and how this affects your thoughts and your actions.
The opposite is also the case by the way. The present depends on the future in the same way that the future depends on the present. It's just that we don't think about it this way. Einstein's theories really are strange, and I don't think we've yet entirely appreciated how strange they are.
[...] You see, so far what I told you was all Einsteinian physics, which doesn't know anything about quantum physics. If you take into account quantum physics, the argument becomes more complicated...
[...] Once you've measured the particle, you can't say exactly what the wave function was. You can only say it was more likely to have been this instead of that. And this sort of indeterminism is entirely compatible with the block universe. It's not deterministic, okay? But it still doesn't tell you which moment is now. To put this differently, there's no such thing as a now in the mathematics of quantum physics. Not unless you actually change something about the maths.
This is why I think the block universe is how nature really works and that our perception of the present moment being somehow special is just false. Like the idea that the earth is flat...
This is why I believe the future already exists ... https://youtu.be/um6BmPo5PZc
