How are light-years measured?

[Jacob]

I think your question boils down to: How is the speed of light determined?

There are some old-fashioned methods that could work quite well to look at how fast light travels, but all of them have been set aside in favor of the assumption that lightspeed is a constant (called "c").

This led to the calculation of a light year, which is a useful tool for working within the field of astronomy under the assumption of c.

But how does a person know how long it has been since the light was emitted? A year ago?

Is the speed of light a constant for all wavelengths in the spectrum?

 

[Stripe]

But how does a person know how long it has been since the light was emitted?

Did you read the experimental setup in my previous post?

Is the speed of light a constant for all wavelengths in the spectrum?

No. Light varies in speed dependent on a number of things, its wavelength being one. The medium it is traveling through and the gravitational environment are two others.

 

[Jacob]

Did you read the experimental setup in my previous post?

I did (afterward), but reading it again helps I think.

No. Light varies in speed dependent on a number of things, its wavelength being one. The medium it is traveling through and the gravitational environment are two others.

What if only the wavelength changes and the speed does not? I have heard that taught.

Would you say the same speed if the same medium? The color is interesting if we define light to be independent of color, all colors, or made up of any particular color but black or darkness.

 

[Stripe]

What if only the wavelength changes and the speed does not?

i don't know.

Would you say the same speed if the same medium?

No. Every inch that light travels, its speed is always affected, because the gravity environment is always changing.

 

[Jacob]

i don't know.

Are you saying that different wavelengths imply different speeds? We obviously think of light in terms of direction and wavelength.

No. Every inch that light travels, its speed is always affected, because the gravity environment is always changing.

I don't know about the gravity environment.

We are talking about distance.

Is it gravity or is it something else that would make light bend around a sphere, if it does?

 

[Stripe]

Are you saying that different wavelengths imply different speeds?

Uh .. yes.

We are talking about distance.

Yes, but I opened with the observation that your question boils down to what the speed of light is.

Is it gravity or is it something else that would make light bend around a sphere, if it does?

Light doesn't "bend around a sphere." Its velocity is affected by gravity.

 

[Jacob]

Uh .. yes.

Do you have a picture in your mind of the distance (length) light travels as opposed to its wavelength (width)?

Yes, but I opened with the observation that your question boils down to what the speed of light is.

Yes, but the unit (measured?) is a light-year which is assumed to be a measure of distance whether it is or not.

Light doesn't "bend around a sphere." Its velocity is affected by gravity.

So somewhere the question then has to do with whether or not this pertains to the earth's gravity if the earth is the sphere being considered.

 

[Stripe]

Do you have a picture in your mind of the distance (length) light travels as opposed to its wavelength (width)?

Of course.

Yes, but the unit (measured?) is a light-year which is assumed to be a measure of distance whether it is or not.

Uh -- of course a light year is a measurement of length. That is not an assumption.

So somewhere the question then has to do with whether or not this pertains to the earth's gravity if the earth is the sphere being considered.

Uh. :idunno:

 

[Jacob]

Of course.

Do you recognize width (wavelength) and distance the light has traveled, to be different? For a wavelength called light we have then the passage of time. But we don't know if light is to be measured in wavelengths. How bright a thing is is different than what color or kind of light it is.

Uh -- of course a light year is a measurement of length. That is not an assumption.

It is if a light year is not a standard unit of measure. How do you know the light comes from an object that was a light year away a year ago?

Uh. :idunno:

 

[Stripe]

Do you recognize width (wavelength) and distance the light has traveled, to be different? For a wavelength called light we have then the passage of time. But we don't know if light is to be measured in wavelengths. How bright a thing is is different than what color or kind of light it is.

I think you are asking questions based on a serious misunderstanding of something, but I can't figure out what it is you do not understand.

It is if a light year is not a standard unit of measure. How do you know the light comes from an object that was a light year away a year ago?

Did you read the post where the experimental setup was described?

Light does not have to travel for a year for an experiment to be possible that shows how fast it will travel. Once it is known how fast it travels, a simple calculation can show how far it will travel in a year.

 

[Jacob]

I think you are asking questions based on a serious misunderstanding of something, but I can't figure out what it is you do not understand.

Do you believe that light is white or that light can be seen as a spectrum of colors?

Did you read the post where the experimental setup was described?

I believe I did, yes. Do you mean this?

I did (afterward), but reading it again helps I think.

Light does not have to travel for a year for an experiment to be possible that shows how fast it will travel. Once it is known how fast it travels, a simple calculation can show how far it will travel in a year.

If you see some light or light is received, we have no idea how far it has traveled.

 

[JosephR]

the speed of light is what I think is the speed of reality...FPS if you will..

Its how far light travels in a year, as previously posted.

So if we send out radio waves from the earth to space, a hundred years ago, then it is a 100 light years away...

The Einstein thought experiment was about what it would be like to travel at the speed of light, kinda like the match lit on the train thought experiment.I imagine as the light moves the physical universe seems to stand still, its all perspective really, and as we are told by Einstein, reality is nothing but a mere illusion,albeit a persistent one.

 

[CabinetMaker]

Light doesn't "bend around a sphere." Its velocity is affected by gravity.

This statement is wrong. The speed of light is not affected by gravity. Large gravitational body act a gravity lens and will change the direction of the light. The speed of light does change based on the medium through which the light travels. The speed of the different wavelengths of light are equally changed.

So how does a prism work? The triangular shape is the key. Ax the light strikes the prism refract the different wavelengths at a different angle.

Please don't pay attention to Stripes notions regarding the speed of light. He casually disregards hundreds of years of research and testing and glibly replaces it with a self serving definition that completely fails to explain what is actually observed about the properties of light.

 

[CabinetMaker]

You are talking about a velocity vector. Is this how you determine the difference between a velocity and a speed?

An orbit (I have heard there is an escape velocity but can't remember how it works) may have a direction or velocity, but in what sense is it a vector? Is it only a vector perpendicular relative to the distance from the earth assuming this remains the same? Or would we say the vector is constantly changing, perhaps in an ideal situation at an even rate relative to some point. I think of the object's orbit path.

By definition, a velocity is a magnitude (speed) and a direction. An escape velocity is the speed and direction that must be achieved to overcome the gravitational pull of a gravitational field.

An orbital path is described by the velocity on the planet (speed and direction) as well as the gravitation of the star attempting to pull the planet in. The velocity of the star sets up a force, centripetal force, that opposes the the stars gravitational force resulting in the orbit of the planet. This is grossly over simplified as orbital mechanics is quite complex, but it is functionally what is going on.

 

[CabinetMaker]

What is light and does some light travel faster than other light? What about colors?

Light is hard to explain. It exhibits the properties of both a particle and a wave yet is not quite either one at the same time. We describe it using photons.

 

[Stripe]

If you see some light or light is received, we have no idea how far it has traveled.

The experimental setup Resurrected posted all those years ago shows your thinking to be wrong.

 

[CabinetMaker]

Uh -- of course a light year is a measurement of length. That is not an assumption.

Strip, do you understand that based on your assumptions regarding the speed of light, a light year is actually a variable in your system?

 

[Stripe]

This statement is wrong.

Evidence. You don't have it. All you have is the assertion of your theory's popularity over mine.

The speed of light is not affected by gravity.

That is a testable claim. Run the experiment Resurrected described in two different gravity environments and see what we get. :thumb:

 

[CabinetMaker]

Evidence. You don't have it. All you have is the assertion of your theory's popularity over mine.

We actually have experimental evidence dating back to 1675. Have you ever actually read and of the history of the measurements of the speed of light?

That is a testable claim. Run the experiment Resurrected described in two different gravity environments and see what we get. :thumb:

Get to it! Publish a paper in a peer reviewed journal with your results and lets see what you got.

The answer to this is, again, non-trivial:

Here.

And here.

 

[Stripe]

We actually have experimental evidence dating back to 1675.

Then you should present that instead of spouting nonsense. :thumb:

Have you ever actually read and of the history of the measurements of the speed of light?

Yes. Have you?

Get to it! Publish a paper in a peer reviewed journal with your results and lets see what you got.

:yawn: The evolutionists' cry of defeat.

The answer to this is, again, non-trivial:

Your "answer" requires that we first assume the truth of what you are trying to prove.