Aberration of light in classical and relatvistical cases

In summary, the aberration of light refers to the change in frequency or angle of light when observed from a moving frame of reference. It was discovered by Bradley in 1727 and can be explained using the concept of four-vectors in special relativity. The formula for calculating the angle of aberration is tan θ' = (cos θ + v/c)/sin θ, where v is the speed of the observer and c is the speed of light.
  • #1
queenstudy
101
0
i need someone to explain me the aberration of light , i tried to read i from my book its a bit more complicated than i thought i mean when we move the microcope we make a tilt what do you mean by that?
all in all i didnt understand this concept and i need a really clear explanation especially that our professor didnt come in the last week , when we needed him the most before the exams please help and thank you
 
Physics news on Phys.org
  • #2
queenstudy said:
when we move the microcope

What microscope? :confused:

Can you describe the apparatus and observations in more detail? Don't assume everybody has read the same book that you have.
 
  • #3
Hi queenstudy.
I do not know about your book either but I can give you a very basic idea of how I understand aberration of light. Instead of light let’s think of one photon. Basically aberration of light means the change in frequency of light. Let’s say we have a photon with a 0.9 Nano second light speed length when produced at a rest frame. If a photon emitter creates photons in opposite directions (in space at a resting frame) the photons will have the same length. Let’s also say this is in the middle of the visual range. Now we will take that same photon emitter in space to ½ the speed of light. The photon created in the forward direction of travel will have a 0.06 Nano second light speed length. This is because of the forward direction at the beginning of the photon creation and the end of the photon creation the spaceship contracted the rest frame photon by 1/3 of the photon distance. In the back of the emitter the photon is elongated and has a photon length of 1.2 Nano light speed length because the emitter moved away at ½ the speed of light. The back is considered red shifted and the front is considered blue shifted. The shorter the length of the photon the more energy it carries. This may or may not be what happens but it is a way of thinking about the aberration of light.
 
  • #4
sorry for the misunderstanding okay?
the aberration fo light was discovered by bradley in 1727 where he observed that the stars appear to move in circles
he imagined that the observer(who is at the surface of the Earth and telescope as well moving to the right with spped v)
so inorder for the light, coming from the star, to pass down the telescope tube without hitting its sides , we should tilt the telescope by an angle alpha
do you want me to explain more or is it enough? i want to know how did he get alpha?
where tan(Alpha)=v/c where v is the speed of Earth and c is the speed of light(star)
 
  • #5
Qzit said:
Basically aberration of light means the change in frequency of light.
No it doesn't. Aberration of light has to do with the angle that the light makes, not the frequency.
 
  • #6
right so can you help me out please about classical and relativistical aberration?
 
  • #7
queenstudy said:
i want to know how did he get alpha?
where tan(Alpha)=v/c where v is the speed of Earth and c is the speed of light(star)
Start here: Aberration of Starlight
 
  • #9
Doc Al and jtbell, I must dissent.

I've always thought of special relativity as a simple subject, where the answers fell out almost automatically. Until, that is, I came to Physics Forums and read some of the 'explanations' offered! The goal, it seems, is to do it all without using the appropriate mathematics. Special Relativity is about four-vectors. With the use of four-vectors, most SR problems have a similar formulation and a quick solution.

But instead I see rambling multi-page verbal descriptions, with step after step and diagram after diagram. Maybe I have an unusually short attention span, but I tend to pass out halfway through such things. An analogous endeavor would be to attempt to explain the levels of the hydrogen atom without using the Schrodinger equation. And in fact, some people do try to do that! And it all looks like magic. But the most serious drawback is that nothing is learned. If you don't build the foundation of a uniform approach, the next problem will look just as challenging as the last.

Deriving the relativistic aberration is a one-liner. (Well Ok, maybe two.) A light ray is described by a propagation vector k = (kx, ky, kz, kt). Under a Lorentz transformation,

kx' = γ(kx + v/c kt)
ky' = ky
kz' = kz
kt' = γ(kt + v/c kx)

If the ray is propagating at an angle θ with the x-axis, k = (k cos θ, k sin θ, 0, k), and

kx'/ky' = γ(kx + v/c kt)/ky
⇒ cos θ'/sin θ' = γ(cos θ + v/c)/sin θ
 

1. What is aberration of light?

Aberration of light is the phenomenon where the apparent position of a celestial object appears to be shifted due to the motion of the observer. This effect is caused by the finite speed of light and the relative motion between the observer and the object.

2. What is the difference between aberration of light in classical and relativistic cases?

In classical physics, aberration of light is explained by the relative motion between the observer and the source of light. However, in relativistic physics, aberration of light is also affected by the curvature of spacetime caused by massive objects.

3. How does aberration of light affect our observations of celestial objects?

The aberration of light causes celestial objects to appear slightly shifted from their actual position, which can affect the accuracy of our observations and measurements. This effect is especially noticeable for objects that are moving at high speeds relative to the observer.

4. Can aberration of light be used to measure the speed of light?

Yes, aberration of light can be used to measure the speed of light. In fact, it was first discovered and measured by astronomer James Bradley in 1729 while trying to measure the speed of light using the eclipses of Jupiter's moons. He observed a shift in the position of the stars due to aberration, which allowed him to calculate the speed of light.

5. How does the angle of aberration change with the speed of the observer?

The angle of aberration is directly proportional to the speed of the observer. This means that as the speed of the observer increases, the angle of aberration also increases. However, the effect becomes negligible at low speeds and is only significant at speeds close to the speed of light.

Similar threads

  • Special and General Relativity
Replies
4
Views
2K
  • Special and General Relativity
2
Replies
45
Views
3K
Replies
130
Views
7K
  • Special and General Relativity
5
Replies
146
Views
6K
  • Special and General Relativity
2
Replies
64
Views
3K
  • Special and General Relativity
Replies
7
Views
1K
  • Special and General Relativity
Replies
25
Views
784
  • Special and General Relativity
2
Replies
52
Views
3K
  • Special and General Relativity
Replies
16
Views
612
  • Special and General Relativity
Replies
20
Views
746
Back
Top