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How I understand #generalrelativity THREAD
A good gif to visualize the difference between #Newton and #Einstein. Although it's not possible to imagine/draw Einstein's system because it's in 4D and our brain works in 3D.
So, we can see an apple (green/red ball) being held...
A good gif to visualize the difference between #Newton and #Einstein. Although it's not possible to imagine/draw Einstein's system because it's in 4D and our brain works in 3D.
So, we can see an apple (green/red ball) being held...
So, we can see an apple (green/red ball) being held by a branch (the green arrow), but suddenly the branch breaks, so there is no more green arrow and the apple falls.
Here's the difference, according to Newton there is a force, gravity, the red arrow, that pulls the apple down
Here's the difference, according to Newton there is a force, gravity, the red arrow, that pulls the apple down
According to Einstein, when the branch breaks, the apple doesn't move, there is no force pulling it "down", there is no red arrow, the apple is following a straight line in a curved spacetime.
And it isn't following a straight line because it's falling straight but because
And it isn't following a straight line because it's falling straight but because
there is no force applying to it, so a free-throw in basketball is also following a straight line since the moment the ball leaves the hands.
The thing is a straight line behaves differently in a curved surface so two parallel lines cross in a curved surface. A geodesic.
The thing is a straight line behaves differently in a curved surface so two parallel lines cross in a curved surface. A geodesic.
Why Newton saw a force? Because he was looking at it like the Earth was still, but obviously it isn't. So when you describe something from a moving place, you need to introduce forces to explain the movement.
This is call a fictitious force, gravity is a fictitious force
This is call a fictitious force, gravity is a fictitious force
The best way to understand a fictitious force is this image. We have 2 frames of reference: the 1 and the 2 (in red).
The frame of reference 1 (FR1) is on the ground of the elevator.
The frame of reference 2 (FR2) is on the ground of the building.
The frame of reference 1 (FR1) is on the ground of the elevator.
The frame of reference 2 (FR2) is on the ground of the building.
According to FR1, to explain how much time the ball takes to touch the ground of the elevator you need to introduce a fictitious force (Ff).
According to FR2, you can explain the time it takes without any fictitious force.
This is what happened to Newton.
According to FR2, you can explain the time it takes without any fictitious force.
This is what happened to Newton.
This is why Einstein is a genius, because he was able to visualize, at least conceptually, a superior dimension, he was able to see the universe as 4D. He saw time mathematically.
The straight line the objects follow in spacetime is time. Time is change and change is a distance.
The straight line the objects follow in spacetime is time. Time is change and change is a distance.
This is something I drew to understand 4D and time.
If you are not moving on any space coordinate, you are only moving on the time coordinate, so in the image you just moved the length of that red arrow.
But that length it's measured with 4D rules, not 3D rules.
If you are not moving on any space coordinate, you are only moving on the time coordinate, so in the image you just moved the length of that red arrow.
But that length it's measured with 4D rules, not 3D rules.
That's why time and space can be measured differently, because it depends from where and when you are measuring it.
Like, it's harder to take a picture moving than still, the same for measuring.
Like, it's harder to take a picture moving than still, the same for measuring.
This is how I imagine the universe after studying Einstein.
Space exists everywhere the same way that time exists all the time.
The past isn't "destroyed" nor the future is being "created"
So I imagine the universe "paused", this means there is no time, only space.
Space exists everywhere the same way that time exists all the time.
The past isn't "destroyed" nor the future is being "created"
So I imagine the universe "paused", this means there is no time, only space.
Every paused universe is an instant.
Each instant evolves to the next one.
Each instants is connected by time, so each instant is separated by X time.
So every instant (paused universe) exists, and time is all the instants connected. Time is to change by not changing.
Each instant evolves to the next one.
Each instants is connected by time, so each instant is separated by X time.
So every instant (paused universe) exists, and time is all the instants connected. Time is to change by not changing.
Time could be seen like the state of lowest energy possible. Like if you do nothing, times happens. And it happens in accordance to universal laws. That's why we can trace back the past or the future, because we follow the energy connecting each instant
The way I picture it is when the apple is falling, the apple isn't moving on space, but it's moving on time, so what we see is the universe moving while the apple is also moving itself in a straight line in time only.
