# Einstein's Belief: Everything Moving at Speed of Light?

In summary, Greene is discussing how relativity affects time, and how if we move closer to the speed of light, we experience less time.
In the book "The Elegant Universe" Brian Green says Einstein once said everything in the universe is moving at the speed of light. How can this be? I thought bodies with mass couldn't reach c.

Greene isn't talking about ordinary speed, he's using a sort of idiosyncratic definition of "speed through spacetime" which personally I think is more misleading than helpful--see this thread for more details.

Could you provide a page number?

I assume this is a misunderstanding about Greene's talking about "speed through time". Greene says you can think of everything moving at the speed of light, but things that don't really move at the speed of light are experiencing most of their "motion" through time rather than space. This can be confusing terminology because the idea of "motion" usually means the amount of space covered in a certain amount of time, but Greene is appealing to the fact that time flows in a direction as well.

edit: I've never read anything from Einstein that stated anything close to "everything moves at c", and I would be surprised if someone dug up an example of Einstein using that terminology. If Greene says "Einstein said everything moves at c," he most likely meant Einstein's theories can be interpreted in such a way.

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Several authors have used this metaphore - it gives you a simple derivation of the transforms. But like Ellipse - I cannot find any reference to it in Einstein's original writings

The velocity 4-vector, i.e. the "velocity" in 4D Minkowski space-time has an invariant magnitude $c$ for all objects. The point is however that this 4-vector cannot be interpreted as a normal velocity like velocities in space. The vector is defined as $$\frac{dx_\mu}{d\tau}$$ whereas normal spatial velocities are $$\frac{dx}{dt}$$. ($\tau$ is proper time, defined as $\tau=t/\gamma$).
What Greene does is rewriting the components of this 4-vector from the usual Minkowski form (+---) into Euclidean form (++++) which also changes the spatial velocity components in normal velocity components $$\frac{dx}{dt}$$. You then end up with a temporal velocity component $$c\frac{d\tau}{dt}$$ which is supposed to be the velocity through the time dimension. Greene's approach is common for what is called "Euclidean relativity", a not very well known alternative mathematical framework for the usual Minkowski framework.

Dimensions and geometry

I think I can understand what you are saying. Green was using 3 dimensions to explain a 4 dimensional phenomena.

By "everything is moving at c," a 4D spacetime is referred to rather than a 3D traditional space. Basically, if we are not moving in the first three dimensions relative to an outside observer, then we are moving completely in the 4th dimension. As we move closer to a total of c in the first 3 dimensions, though, less of our "4D-velocity" is directed in the "t" direction and therefore we appear to experience less time to an outside observer.

Basically, this is just a simple way to try to explain the effects of relativity; that is, if we move at a velocity closer to c in space, we move at a slower "velocity" through time.

If my guess is correct, i believe that it was an example about the limit of going to close to the speed of light and its effect on the dilation of time.

With an analogy of a fast moving vehicle trying to calculate its maximum speed by going through a series of test runs.

The first direction taken from point A to B taken to be parrallel to an axis, and the rest of the runs be slightly deviated from the original axis (cause by human error) causing a slight slower time achieved than the rest of the runs.

Eg

y-axis |
|
|
|_______ x-axis

With either of the Axis being Space and Time

With the above analogy being given then more speed less time and less speed more time

I hope i am understandable. Cause i have the above book though. Kinda slow to digest if you are a bit of a beginner(me) and you try to understand everythig in the book =P

## 1. What is Einstein's belief about everything moving at the speed of light?

Einstein's belief is that everything in the universe, including light, moves at the speed of light in a vacuum, which is approximately 299,792,458 meters per second.

## 2. Why did Einstein believe that everything moves at the speed of light?

Einstein's theory of special relativity states that the speed of light is constant and does not depend on the observer's perspective. This means that no matter how fast an observer is moving, they will always measure the speed of light as the same value. Based on this principle, Einstein believed that everything must move at the speed of light.

## 3. Is everything really moving at the speed of light?

While Einstein's theory of special relativity is widely accepted, it is still a theory and not a proven fact. There are some phenomena, such as gravitational waves, that appear to move faster than the speed of light. However, these are still being studied and do not necessarily disprove Einstein's belief.

## 4. How does Einstein's belief impact our understanding of the universe?

Einstein's belief about everything moving at the speed of light has greatly impacted our understanding of the universe. It has led to the development of technologies like GPS, as well as new theories and discoveries in physics. It also challenges our traditional understanding of time and space, and has implications for the study of black holes and the expansion of the universe.

## 5. Can anything truly move at the speed of light?

According to Einstein's theory of special relativity, it is impossible for anything with mass to reach the speed of light. As an object approaches the speed of light, its mass increases infinitely and it would require an infinite amount of energy to accelerate it to that speed. However, particles with no mass, such as photons, can travel at the speed of light.

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