Astronomy: Classic debates

Being the year of astronomy it would be worthwhile to review some of the great debates of the past: The 1921 debate between Harlow Shapley and Herber Curtis in 1921 and the cosmological debates of the 1930s and 1940s. Of the latter from the Stanford Encyclopedia of Philosophy...

Sometimes, philosophy drives science. Cosmology between 1932-48 provides an excellent example how explicitly philosophical considerations directed the evolution of a modern science during a crucial period of its development. The following article exhibits these philosophical aspects of cosmological thinking in detail, beginning with a brief sketch of the historical development of general relativity cosmology until 1932. Following this, the historical participants in the philosophical debate are introduced, along with the basic ideas of their competing positions. Then the critical stages of the debate -- 1935-37 -- are closely explored by focussing directly upon the arguments of the participating scientists and philosophers. Finally, the concluding stage of the philosophical debate, namely, the emergence of the steady-state theory of the Universe, is presented in the context of its development from Popper's philosophy of science.


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"The Great Debate" [1921]--Shapley & Curtis

The astronomy/cosmology debates of the 1930's & 1940's

An over zealous Sir Arthur Stanley Eddington?

An over zealous Sir Arthur Stanley Eddington?

Sir Arthur Stanley Eddington

The materials:

Philosophiae Naturalis Principia Mathematica [1687]--Newton

Relativity: The Special and General Theory--Einstein

"Report on the relativity theory of gravitation"--Eddington

The event:

1919 solar eclipse

Where:

Two expeditions were organized, one to Sobral in Brazil and the other including Sir Arthur Eddington, to the island of Principe off the west coast of Africa. At Principe there was a thunderstorm in the morning which cleared in time to take photographs, only two of which showed star images. At Sobral the clouds also cleared in time to make observations and 7 usable plates were obtained.

The players:

Albert Einstein

Sir Arthur Stanley Eddington

Result:

Confirmation of Einstein's Theory that predicted light was bent when it passes close to a massive body. MAYBE NOT...for this involved skewed data and perhaps an over zealous Eddington.

"Did Researchers Cook Data from the First Test of General Relativity?

Rumors of data mishandling in an historic eclipse study don't gibe"

by

J. R. Minkel

March 6th, 2008

Scientific American

On May 29, 1919, two British expeditions, positioned on opposite sides of the planet, aimed telescopes at the sun during a total eclipse. Their mission: to test a radical theory of gravity dreamed up by a former patent clerk, who predicted that passing starlight should bend toward the sun. Their results, announced that November, vaulted Albert Einstein into the public consciousness and confirmed one of the most spectacular experimental successes in the history of science.

In recent decades, however, some science historians have argued that astronomer Sir Arthur Eddington, the junior member of the 1919 expedition, believed so strongly in Einstein's theory of general relativity that he discounted data that clashed with it.

In 1919 general relativity was on the cusp of eclipsing Sir Isaac Newton's law of universal gravitation, put forth in 1687. Newton's law cast gravity as a type of bond between objects, all floating within the gridlike arena of space and time. Einstein's insight was that gravity is the grid, which is warped by massive objects such as the sun. As a consequence, light passing the sun should literally fall toward it like a moon rover clipping the edge of a giant crater and falling in.

Eddington, then director of the University of Cambridge Observatory, convinced his senior colleague and England's Astronomer Royal, Sir Frank Dyson, to mount the expedition. The group split into two teams: Dyson's crew from what was then the Royal Observatory in Greenwich headed to the town of Sobral, Brazil, as Eddington and cohorts set up on the western African island of Príncipe. Their task was to independently record the positions of the stars near the moon-blotted sun and compare them with the positions of the same stars at night.

If general relativity was right, the apparent positions of the nearest stars would drift 1.75 arc seconds (a measure of angularity) closer to its rim during the eclipse (a pencil width seen at half a mile). Eddington was hampered by overcast skies on the long-awaited day and photographed only five stars. It was too few for a solid result, but he gave some weight to his final value of 1.61 arc seconds.

Dyson's team had mixed results. One of the group's two telescopes functioned correctly and gave them a value of 1.98 arc seconds. The second instrument yielded a value of 0.93 arc second, which was rather close to the Newtonian prediction of 0.87. The instrument, however, had lost focus during the eclipse, which cast doubt on the accuracy of the photo comparison, so they excluded the measurement from their final result. Based on the remaining evidence, they declared general relativity triumphant.

Over time, experts looked askance at the sweeping conclusion, which both ignored the possibility that some other theory of gravity might have better fit the results and also didn't match general relativity very precisely after known sources of error were taken into account. "No experiment is decisive in the way that Eddington's experiment was presented as being decisive," says Harry Collins, a sociologist of science at Cardiff University in Wales. Indeed, researchers didn't truly nail the light-bending prediction until they used quasar measurements made in the 1960s, says physicist Clifford Will of Washington University in St. Louis, an expert in tests of general relativity.

Science historians John Earman, then at the University of Minnesota, and Clark Glymour of the University of Pittsburgh, revisited the eclipse study in a 1980 paper, concluding that Eddington had erred by suppressing the clashing Sobral result.

But the historical revision never received much scrutiny, physicist–historian Daniel Kennefick of the University of Arkansas Center for Space and Planetary Sciences in Fayetteville argues. "It's actually like you can see two myths layered on top of each other," he says.

To disentangle them, he dug into the historical record. Letters between Eddington and Dyson indicate that the two analyzed their data separately to avoid influencing each other, Kennefick reports in a recent paper. That means Dyson, who was at first ambivalent about Einstein's theory, made the initial judgment to exclude the 0.93–arc second result. Kennefick documents that Eddington acted properly when Dyson, presumably overeager at the potential discovery, put aside his first instinct and proposed averaging the three measurements to get a value that was closer to Einstein's prediction.

Eddington squelched the idea, because it would have meant giving added weight to the suspect measurement from Sobral. Biased or not, Eddington made the right call, says Kennefick, who discovered that Royal Observatory staff in Greenwich had reanalyzed the Sobral data in 1978 using modern computer-based methods. (The Príncipe data hadn't survived.) Their correction put the 0.93–arc second shift at 1.55 arc seconds, plus or minus 0.34—much closer to the 1.75 value. In other words, the researchers were right to suspect that the measurement was flawed.

"If I was in the same position, I would have done the same thing," says Washington University's Will, who adds that he never believed Eddington had cooked the numbers. "It just didn't seem credible to me that someone of his stature would throw out data because it didn't look right."


"Anomalies in the History of Relativity"

Abstract:

In November 1919 it was announced to the world that observations of a solar eclipse that occurred in May 1919 supported 1919 solar eclipse's general theory of relativity. That announcement was one of the most influential events of 20th-century science, since Einstein’s instant rise to enormous fame arose directly from it. In spite of the confidence with which the announcement was made, however, it was later realized that the accuracy of the observations was insufficient to constitute a reliable confirmation of the phenomenon that was predicted. Furthermore, another of the formulas published in the general theory, for the variation in the perihelion of the planet Mercury, had already been derived by another scientist several years earlier using another method. In spite of the fact that the experimental evidence for relativity seems to have been very flimsy in 1919, Einstein's enormous fame has remained intact and his theory has ever since been held to be one of the highest achievements of human thought. The resulting deification of Einstein has had some unfortunate effects: critics of his theory are often dismissed as cranks, and the search for better theories has been inhibited. It is suggested that the announcement of the eclipse observations in 1919 was not a triumph of science as it is often portrayed, but rather an obstacle to objective consideration of alternatives.

"Einstein, Eddington and the 1919 Eclipse"

Abstract:

The modern era of cosmology began with the publication of Einstein’s general theory of relativity in 1915. The first experimental test of this theory was Eddington’s famous expedition to measure the bending of light at a total solar eclipse in 1919. So famous is this experiment, and so dramatic was the impact on Einstein himself, that history tends not torecognize the controversy that surrounded the results at the time. In this paper I discuss the experiment in its historical and sociological context and show that it provides valuable lessons for modern astronomy and cosmology.

"Judging Einstein"

Sir Arthur Stanley Eddington--poetic tribute

Books by Sir Arthur Stanley Eddington:

New Pathways In Science

Philosophy of Physical Science

Relativity Theory of Protons and Electrons

Space, Time and Gravitation : An Outline of the General Relativity Theory

Stellar Movements and the Structure of the Universe

The Nature of the Physical World

The astronomy/cosmology debates of the 1930's & 1940's

Sir Arthur Stanley Eddington--poetic tribute

Sir Arthur Stanley Eddington was a champion of Albert Einstein, went to South America with Einstein to view the 1919 solar eclipse, and introduced the world to Einstein--they were good buddies. Sharing an office with Eddington in the early 1920's at Berkeley, W. H. Williams composed the following poem. It has been intimated that it was based on the nonsense poem "The Walrus and The Carpenter" by Lewis Carroll. See for yourself. [The Lewis Carroll poem is last.]

"The Einstein and the Eddington"

by

Dr. W. H. Williams

The sun was setting on the links,
The moon looked down serene,
The caddies all had gone to bed,
But still there could be seen
Two players lingering by the trap
That guards the thirteenth green.
The Einstein and the Eddington
Were counting up their score;
The Einstein's card showed ninety-eight
And Eddington's was more.
And both lay bunkered in the trap
And both stood there and swore.
I hate to see, the Einstein said;
Such quantities of sand;
Just why they placed a bunker here
I cannot understand.
If one could smooth this landscape out,
I think it would be grand.
If seven maids with seven mops
Would sweep the fairway clean
I'm sure that I could make this hole
In less than seventeen.
I doubt it, said the Eddington,
Your slice is pretty mean.
Then all the little golf balls came
To see what they were at,
And some of them were tall and thin
And some were short and fat,
A few of them were round and smooth,
But most of them were flat.
The time has come, said Eddington,
To talk of many things:
Of cubes and clocks and meter-sticks
And why a pendulum swings.
And how far space is out of plumb,
And whether time has wings.
I learned at school the apple's fall
To gravity was due,
But now you tell me that the cause
Is merely G_mu-nu,
I cannot bring myself to think
That this is really true.
You say that gravitation's force
Is clearly not a pull.
That space is mostly emptiness,
While time is nearly full;
And though I hate to doubt your word,
It sounds like a bit of bull.
And space, it has dimensions four,
Instead of only three.
The square of the hypotenuse
Ain't what it used to be.
It grieves me sore, the things you've done
To plane geometry.
You hold that time is badly warped,
That even light is bent:
I think I get the idea there,
If this is what you meant:
The mail the postman brings today,
Tomorrow will be sent.
If I should go Timbuctoo
With twice the speed of light,
And leave this afternoon at four,
I'd get back home last night.
You've got it now, the Einstein said,
That is precisely right.
But if the planet Mercury
In going round the sun,
Never returns to where it was
Until its course is run,
The things we started out to do
Were better not begun.
And if before the past is through,
The future intervenes;
Then what's the use of anything;
Of cabbages or queens?
Pray tell me what's the bally use
Of Presidents and Deans.
The shortest line, Einstein replied,
Is not the one that's straight;
It curves around upon itself,
Much like a figure eight,
And if you go too rapidly
You will arrive too late.
But Easter day is Christmas time
And far away is near,
And two and two is more than four
And over there is here.
You may be right, said Eddington,
It seems a trifle queer.
But thank you very, very much,
For troubling to explain;
I hope you will forgive my tears,
My head begins to pain;
I feel the symptoms coming on
Of softening of the brain.


"The Walrus and The Carpenter"

by

Lewis Carroll

from

Through the Looking-Glass and What Alice Found There

1872

The sun was shining on the sea,
Shining with all his might:
He did his very best to make
The billows smooth and bright--
And this was odd, because it was
The middle of the night.
The moon was shining sulkily,
Because she thought the sun
Had got no business to be there
After the day was done--
"It's very rude of him," she said,
"To come and spoil the fun!"
The sea was wet as wet could be,
The sands were dry as dry.
You could not see a cloud, because
No cloud was in the sky:
No birds were flying overhead--
There were no birds to fly.
The Walrus and the Carpenter
Were walking close at hand;
They wept like anything to see
Such quantities of sand:
"If this were only cleared away,"
They said, "it would be grand!"
"If seven maids with seven mops
Swept it for half a year.
Do you suppose," the Walrus said,
"That they could get it clear?"
"I doubt it," said the Carpenter,
And shed a bitter tear.
"O Oysters, come and walk with us!"
The Walrus did beseech.
"A pleasant walk, a pleasant talk,
Along the briny beach:
We cannot do with more than four,
To give a hand to each."
The eldest Oyster looked at him,
But never a word he said:
The eldest Oyster winked his eye,
And shook his heavy head--
Meaning to say he did not choose
To leave the oyster-bed.
But four young Oysters hurried up,
All eager for the treat:
Their coats were brushed, their faces washed,
Their shoes were clean and neat--
And this was odd, because, you know,
They hadn't any feet.
Four other Oysters followed them,
And yet another four;
And thick and fast they came at last,
And more, and more, and more--
All hopping through the frothy waves,
And scrambling to the shore.
The Walrus and the Carpenter
Walked on a mile or so,
And then they rested on a rock
Conveniently low:
And all the little Oysters stood
And waited in a row.
"The time has come," the Walrus said,
"To talk of many things:
Of shoes--and ships--and sealing-wax--
Of cabbages--and kings--
And why the sea is boiling hot--
And whether pigs have wings."
"But wait a bit," the Oysters cried,
"Before we have our chat;
For some of us are out of breath,
And all of us are fat!"
"No hurry!" said the Carpenter.
They thanked him much for that.
"A loaf of bread," the Walrus said,
"Is what we chiefly need:
Pepper and vinegar besides
Are very good indeed--
Now if you're ready, Oysters dear,
We can begin to feed."
"But not on us!" the Oysters cried,
Turning a little blue.
"After such kindness, that would be
A dismal thing to do!"
"The night is fine," the Walrus said.
"Do you admire the view?
"It seems a shame," the Walrus said,
"To play them such a trick,
After we've brought them out so far,
And made them trot so quick!"
The Carpenter said nothing but
"The butter's spread too thick!"
"I weep for you," the Walrus said:
"I deeply sympathize."
With sobs and tears he sorted out
Those of the largest size,
Holding his pocket-handkerchief
Before his streaming eyes.
"O Oysters," said the Carpenter,
"You've had a pleasant run!
Shall we be trotting home again?'
But answer came there none--
And this was scarcely odd, because
They'd eaten every one.