Effects of a massive object on light and its relation to the 1919 Eclipse

This is exactly what Einstein predicted with General Relativity theory. Later this was proven with better equipment and is now considered one of the confirmations of General Relativity theory.In summary, the 1919 lunar eclipse provided evidence for Einstein's General Relativity theory by showing that light bends when passing near a massive object, as predicted by the theory. This was verified by observing the apparent and actual location of stars during the eclipse, which showed a slight shift due to the bending of light around the Sun. Despite some doubts about the accuracy of the initial measurements, subsequent experiments and advancements in technology have confirmed the validity of General Relativity theory.
  • #1
JM2107
[SOLVED] Effects of a massive object on light and its relation to the 1919 Eclipse

What happens to light as it passes near a massive object and how it this principle or concept connected to the 1919 lunar eclipse where Einstein’s Photoelectric theory was proved (both the apparent and actual location of the stars were revealed around the area of the eclipse?

Thanks for any responses in advance.
 
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  • #2
It was not Photoelectric effect that was (perhaps falsly) verified during the 1919 eclipse put General Relativity. The observations were of the position of a star that was being oculted during the eclipse. GR predicted that the postion of the star would shift as the disk of the sun passed in front of it.

It is not clear in this day and age that the instrumentation and the methods uses were actually up to the task. It may well be that the verifing data was more wishfull thinking then sound numbers. Of course, since that time the measurements have been repeated modern equipment and methods and the theory has been verified many times over.
 
  • #3
Originally posted by JM2107
What happens to light as it passes near a massive object i]

Thanks for any responses in advance.


If a ray of light passes within a distance R from an object with mass M then it is bent by an angle which can be calculuated
using this formula from Einstein's 1916 paper on general relativity:


angle in radians = 4GM/c2R


It was this angle that Eddington's team was trying to check
when they observed the Pleiades during the 1919 eclipse of the sun. They thought they verified that the formula was right---it was headline news "Einstein Proved Correct!" and so on.
 
  • #4
I hope no one is vexed by this side comment and proceeds to declare me out of the mainstream for mentioning it
but I will take that risk.

In natural units (c=G=hbar=1) the sun's mass is 93E36
and a million miles is E44.

the formula for the angle is simply 4M/R radians

But 4M is 37E37

So, if a ray of light passes a million miles from the sun's center,
it is bent by the angle you get by dividing 37E37 by E44.


37E37/E44 = 37E-7 radians-------3.7E-6-----3.7 microradians

It seems to me that natural units, which so many physicists use nowadays in research and theoretical papers, actually help here by making the formula 4M/R so much simpler. It is a mess to do
the formula in metric with numbers like 6.673E-11 for G and so on.

**********

There is a side issue of how did I know the mass of the sun is 93E36.

that is easy to remember if you can remember that the distance to it is 93 million miles.

Because in natural units M=RV2, where R is the radius of a small object's circular orbit and V is the orbit speed. In the case of the Earth (small, in roughly circular orbit) V = E-4 and R=93E44 (93 million miles) so the mass of the sun is quick to compute just by multiplying

M = RV2 = 93E44 x E-8 = 93E36

Again you quite possibly cannot remember the mass of the sun in kilograms and would probably not like to calculate it from what you do know about distance and orbit speed because it would involve messy numbers like 6.673E-11 for G and so on. So natural units are somewhat more practical in this context.
As well as increasingly mainstream (some John Baez discussion on Usenet bears on this)

But if you can remember the mass of the sun in kilograms then of course go ahead and use the metric formula for the angle mentioned earlier

angle = 4GM/c^2R

instead of 4M/R
 
  • #5
Originally posted by JM2107
What happens to light as it passes near a massive object and how it this principle or concept connected to the 1919 lunar eclipse where Einstein’s Photoelectric theory was proved (both the apparent and actual location of the stars were revealed around the area of the eclipse?

Thanks for any responses in advance.

Not Photoelectric theory (for which Einstein got Nobel Prize, by the way), but General Relativity theory.

Basicly what you do is to take picture of starry sky at night and during eclipse and superimpose them. Distance between stars (on a photograph) increases slightly when Sun is among them - this means that starlight sligtly bends around Sun.
 

1. How did the 1919 Eclipse confirm Einstein's theory of general relativity?

The 1919 Eclipse provided a unique opportunity for scientists to observe the bending of starlight by the Sun's massive gravitational pull. According to Einstein's theory of general relativity, massive objects such as the Sun can bend the path of light. The observations made during the 1919 Eclipse matched the predictions of general relativity, providing strong evidence for the theory's validity.

2. What is the significance of the 1919 Eclipse in the history of science?

The 1919 Eclipse is considered a major milestone in the history of science as it provided the first experimental evidence for Einstein's theory of general relativity. The confirmation of this theory revolutionized our understanding of gravity and space-time, and it continues to be a fundamental principle in modern physics.

3. How did the 1919 Eclipse change our understanding of the universe?

The confirmation of general relativity during the 1919 Eclipse fundamentally changed our understanding of the universe. It showed that gravity is not a force between masses, but rather a curvature of space-time caused by massive objects. This led to a new understanding of the universe, including the concept of black holes and the expansion of the universe.

4. What techniques were used to observe the effects of a massive object on light during the 1919 Eclipse?

During the 1919 Eclipse, scientists used the technique of astrometry, which involves measuring the positions of stars in the sky, to observe the bending of starlight by the Sun's gravity. They also used spectroscopy, which involves analyzing the light emitted by stars, to confirm the presence of the predicted gravitational redshift caused by the Sun's massive object.

5. What other astronomical events have been used to study the effects of a massive object on light?

Aside from the 1919 Eclipse, other astronomical events have been used to study the effects of a massive object on light. For example, the gravitational lensing effect, which is the bending of light by massive objects, has been observed during the transit of Mercury and the transit of Venus. These events provide opportunities to further test and refine our understanding of general relativity and the effects of massive objects on light.

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