The Hertzsprung-Russell diagram, "Wart on the Umpire's Nose"

[gfellow]

I suppose the following belongs in this topic, although I had the good fortune to get it published many moons ago in Science News.
Fortunately, it ought to offend no one, nor upset any pet theories...

The Hertzsprung-Russell diagram is the bulwark of stellar evolution, but consider this little story:

An umpire is standing in a crowded stadium. Upon his nose is an intelligent wart. This wart desires to know the process of evolution of its host, the umpire. To aid itself in this quest, the wart observes the other people in the stadium. Although the wart cannot see, it is able to monitor the heartbeats and blood pressure of the people present. Armed with this information, the wart constructs a graph upon which it now places its data.

The Hertzsprung-Russell Diagram, where luminosity is replaced with blood pressure, and temperature with heartbeat.

The wart now mistakenly believes that by comparing people in this manner it has acquired a system that displays a sequence of evolution from birth to death. The graph displays no such information; it merely describes the momentary state of excitement of the people in the stadium.

Published in Science News,
Vol. 177, May 17th, 1980

[captain swoop]

and?

[gzhpcu]

So basically, we are the warts, the umpire is our sun and the people in the stadium are stars. You saying that the interpretation of the Hertzsprung-Russell diagram in respect to stellar evolution is wrong. What arguments do you have to sustain this argument?

[grant hutchison]

Yes, both diagrams show variables that correlate: blood pressure and pulse (via the sympathetic nervous system); luminosity and temperature (via the physics of star equilibrium). Neither diagram (as it stands) shows an evolutionary sequence from birth to death, though it's possible in both diagrams to drawn in such evolutionary tracks. (Drawing a lifetime track on the BP/pulse diagram isn't particularly informative beyond the childhood years, however.)
I'm not sure why anyone would think this is ATM.

Grant Hutchison

[pzkpfw]

The analogy states that the wart is blind, and can only measure two factors of the things it is studying.

This seems unreasonably restrictive, if it really is trying to argue that the Hertzsprung-Russell diagram or the conclusions drawn from it are wrong.

If we were the wart, we could start by examining further our own host so we could extrapolate to the other beings. For example - does the heartbeat and pressure of our own host change and correlate in the same way?

Further, I'm sure we'd be able to measure more than just two factors. For example - what is the size of the being being measured?

We'd also be studying what pressure and heartbeats actually are and what they tell us about the Universe.

(Having said that, I don't actually know what other factors were used to support the Hertzsprung-Russell diagram... any got a good link? [yes I can google, asking for a recommendation])

[pzkpfw]

Speaking of google: http://goodfelloweb.com/nature/cgbi/umpires_nose.html

In this, the last line from the author is "I urge that the Hertzsprung-Russell diagram be taken with a pinch of caution"... which I guess shows what this thread was started for.

[dgruss23]

I suppose the following belongs in this topic, although I had the good fortune to get it published many moons ago in Science News.
Fortunately, it ought to offend no one, nor upset any pet theories...

The Hertzsprung-Russell diagram is the bulwark of stellar evolution, but consider this little story:

An umpire is standing in a crowded stadium. Upon his nose is an intelligent wart. This wart desires to know the process of evolution of its host, the umpire. To aid itself in this quest, the wart observes the other people in the stadium. Although the wart cannot see, it is able to monitor the heartbeats and blood pressure of the people present. Armed with this information, the wart constructs a graph upon which it now places its data.

The Hertzsprung-Russell Diagram, where luminosity is replaced with blood pressure, and temperature with heartbeat.

The wart now mistakenly believes that by comparing people in this manner it has acquired a system that displays a sequence of evolution from birth to death. The graph displays no such information; it merely describes the momentary state of excitement of the people in the stadium.

Published in Science News,
Vol. 177, May 17th, 1980

First, The Hertzsprung-Russell diagram doesn't look like that. The diagram above lacks the red giants, bright giants, supergiants, white dwarfs - all key components in understanding stellar evolution.

Second, the main sequence (the only portion of the diagram shown on your version) is not an evolutionary sequence. Stars do not evolve from type O to type M.

Third, why would I infer from your version of the diagram that people evolve from high blood pressure to low blood pressure? Scientists look for physical explanations for observed relationships. The graph you've done would be attacked first as a physical problem. The scientist would ask ... Why is blood pressure higher when heart rate is faster? You would only see this as an evolutionary sequence if you had some empirical evidence for systematic age relations along your graph or pre-existing theoretical ideas that hinted that such a relationship might be expected.

Regarding early ideas about stellar evolution, even before the publication of the H-R diagram, some people thought that stars would evolve from a higher temperature condition toward a lower temperature condition. Since it was recognized that the spectral lines produced were related to the stellar temperature, the spectral sequence was initially interpreted as a possible evolutionary sequence.

However, Russell himself pointed out after publishing the H-R diagram that the existence of Red giants required a more complex evolutionary sequence. Russell suggested that stars evolved from the Red Giant stage to B-type as they contracted and heated. Then they began to cool from B-type main sequence through M-type main sequence.

Subsequent discoveries put this idea to rest as well, but it was a good attempt for what was known at the time.

[dgruss23]

BTW, welcome to the BAUT forum!

[grant hutchison]

(Having said that, I don't actually know what other factors were used to support the Hertzsprung-Russell diagram... any got a good link? [yes I can google, asking for a recommendation])

Hertzesprung and Russell merely noted that there were areas of their graph which contained many stars (the main sequence, the giant branch) and areas which contained very few.
To understand why that may be, we need to understand some of the underlying physics of stars, and to understand how stars might evolve from one region of the diagram to another, we need to understand a lot of the underlying physics. So H-R is simply an observation, not a theory of how stars evolve.
Likewise in a chart plotting blood pressure and heart rate for a population of humans. While there is a "main sequence" of people in which heart rate correlates with blood pressure, there are individuals who have extreme hypertension and a slow heart rate (those with high intracranial pressure, for instance). So we need to understand physiology to understand why individuals occupy particular locations on the blood-pressure/heart-rate diagram.

None of this is new, and I'm not sure what lesson of caution we are supposed to learn from the analogy drawn.

Grant Hutchison

[gfellow]

I apologize for making this a general reply to cover all the thoughtful replies - and my! What a lot of sharp minds there are on this forum.
As pzkpfw pointed out, the theme was "A pinch of caution" and upon reflection was perhaps an ill advised omission.

The Aristarchian heliocentric universe was abandoned because the Ptolemaic geocentric system could with some accuracy describe the retrograde motion of planets. A thousand years of misinterpretation and lost opportunity ensued.

As we look out into this amazing universe, where there is so much to observe and so little hard data which is truly interpretable, I believe it is important that as observers we be humble - to continuously reflect and reexamine the very foundations upon which we place our data.
We do this to hold at bay the long, dark night of ignorance.

- I am sorry that I will probably not be able to answer replies to this post in a timely manner. A death in the family is consuming my attentions at the moment - but oh, this forum is a wonderful respite.

[Jerry]

A pinch of caution is warrented. White Dwarf populations seem to fall off the chart anywhere and everywhere.

[R.A.F.]

What a lot of sharp minds there are on this forum.

You "sound" surprised.

A death in the family is consuming my attentions at the moment...

Please accept our condolences...