# Is Lightspeed Determining the Vertical Speed of Light Accurately?

• Tage
In summary, the conversation discussed the speed of light and its relation to its wavelength. It was clarified that light always travels at the speed of light, regardless of its wavelength. The analogy of a ball flying at a constant speed was used to explain this concept. It was also mentioned that light travels in a straight line, not in waves as some may think.
Tage
Is lightspeed defining the speed of light in which it travels a vertical length?
Can lightspeed be used to accurately decide how long it will take for light to travel 5 meters straight vertically?

Considering that light has wave length that 'should' not be the case.
Does this mean that different types of light travels faster than others in a straight direction?

Hopefull for answers, tell me if I need to clarify what I mean better.

/Tage

I also want to know if light or anything for that matter has wave lenghts in vacuum.

Tage said:
Hopefull for answers, tell me if I need to clarify what I mean better.

/Tage

Yes padawan. To clarify better we want you.

TI.

Well, your second post... yes. Light travels in a vacuum and can be described as a wave with a wavelength. I dodn't understand your first post, sorry. The direction the light travels in is irrelevant, in fact arbitrary. Yes, you can tell how long it will take for light to travel 5 m.

Since light has a wave length it doesn't travel in a straight line.
Hence I was wondering wether lightspeed is the definition of the time it takes for light to travel a vertical length or if the wave lengths are accounted for aswell.
I'll try to make a picture..:)

<--------->5m
^ ^
/ \_/ \

Is lightspeed the speed at which the particle is moving? In that case wave length would speed down the vertical speed.
If not, then lightspeed < the speed at which the particle is moving.

Hope that helped.

EDIT: (The picture changes appearence after I hit the 'post' button, another mystery of the universe)

It helped in making the confusion even larger.The light in vacuo,treated as a classical wave,has the nice property of non dispersion,which translates into phase velocity is equal to group velocity and equal to "c".If u know the definitions for the two kinds of velocity,then u can simply get the exact meaning of "c".

HINT:since v_{g}=c,it won't be so obvious.I suggest you pick the mathematical form of harmonical scalar em wave traveling in vacuum:

$$\psi (\vec{r},t)=\psi_{0}e^{i\left(\vec{k}\cdot\vec{r}-\omega t\right)}$$

Daniel.

I'll give this one last shot before I give up.
I'm sorry but I didn't understand half of what you just said Dextercioby, thanks for trying though.

Say that you are driving from New York to Los angeles´, it's 500miles bird route but since you have to follow the road it's 750 miles (I'm just making these numbers up).
This can be compared to light following it's road (going in waves).
5meters 'bird route' might be 7meters considering that it follows a road (not going in a straight line but in waves).

With that in mind, is lightspeed the speed at which light covers the bird route?
Since different lights has different wave lenghts the speed at which they cover the bird route would be different.

Hope this didn't leave you even more confused.

Nope,a pointlike light source produces a perfect spherical wave whose surface of constant phase propagates at "c" in vacuum.It's the simplest explanation of light propagation one could give and very useful for special relativity.

Daniel.

Tage said:
I'll give this one last shot before I give up.
I'm sorry but I didn't understand half of what you just said Dextercioby, thanks for trying though.

Say that you are driving from New York to Los angeles´, it's 500miles bird route but since you have to follow the road it's 750 miles (I'm just making these numbers up).
This can be compared to light following it's road (going in waves).
5meters 'bird route' might be 7meters considering that it follows a road (not going in a straight line but in waves).

With that in mind, is lightspeed the speed at which light covers the bird route?
Since different lights has different wave lenghts the speed at which they cover the bird route would be different.

Hope this didn't leave you even more confused.

Er, young padawan, you are saying strange things. Beware, you are closer to the dark side of the force.

I will give you an analogy. Take 2 balls flying at the same speed in a bird route. Now say that the ball is a light of a given wavelenght (the size of the ball). Why do you want to get a different speed for a different size (a different wavelenght? (they are both equal in this example).

TI.

Daniel, to what side of the force do you belong?

Last edited:
Tage, I believe I understood the source of your worry. The light itself does not move up to its crest and down to its trough as it propogates. These amplitudes relate to the waves energy density. It is not the path the light actually travels by.

Tage said:
Since light has a wave length it doesn't travel in a straight line.
You got a completely wrong idea! Light "waves" are changes in the electro-magnetic field not in space- light does, indeed, travel in a straight line.

Thanks everybody for clarifying, I finally got it :)

Tage said:
Thanks everybody for clarifying, I finally got it :)

## 1. How fast is the speed of light?

The speed of light in a vacuum is approximately 299,792,458 meters per second, or about 670,616,629 miles per hour.

## 2. Can anything travel faster than the speed of light?

According to Einstein's theory of relativity, nothing can travel faster than the speed of light. The speed of light is considered the ultimate speed limit of the universe.

## 3. Why is the speed of light important in physics?

The speed of light is important in physics because it is a fundamental constant that plays a crucial role in many theories and equations, such as Einstein's famous equation E=mc^2. It also determines the maximum speed at which information and energy can travel, which has implications in many areas of science.

## 4. How do we measure the speed of light?

The speed of light can be measured using various methods, such as using mirrors and a rotating wheel to measure the time it takes for light to travel a certain distance. The most accurate measurement was achieved using a technique called the "vacuum cavity resonator" method, which measured the speed of light to be 299,792,458 meters per second.

## 5. Has the speed of light always been constant?

According to our current understanding of physics, the speed of light has always been constant. However, some theories suggest that in the early stages of the universe, the speed of light may have been different due to the conditions of the universe at that time. This is still a topic of ongoing research and debate among scientists.

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