How can scientists possibly know ... ?? An open exploration thread

[shernren]

One thing that contributes to creationism is this idea that scientists merely pull facts/ideas out of thin air, and expect people to believe them just because ... well, because it's them saying so! The implication, of course, is that evolution is one of those things pulled out of thin air, and thus any Tom, Dick and Harry is both informed and qualified enough to lambast the scientific validity of that theory.

Of course scientists don't pull ideas out of thin air. However, there is some truth to the idea. Science education certainly sounds very often like things have been pulled out of thin air. Over the course of your science education you were probably taught countless things that were never really justified. "All matter is made of atoms." "The Earth is round." "A mole contains 6 x 10^23 atoms / molecules." "Stars generate power by fusion." The way you're taught them, these facts certainly sound like gospel truth brought down from Mount Scientificus by Saint White Coat.

So this thread is dedicated to the question we should always ask, whether about evolutionary science or not:

How can scientists possibly know this??
​

and this is an open invitation to anyone, whatever your orientation on origins, to throw out those factoids that were drilled into your head in school which you never bothered to question or consider. How can scientists possibly know? Let's see!

 

[Biblewriter]

When I was in high school and in college, one of the best known scientific facts was that the human cell contained 48 chromosomes (24 pairs. My faith in science as a whole was seriously shaken when during my Junior year in the university it was suddenly discovered that the human cell only contained 46 chromosomes (23 pairs).

This was a very simple fact, something anyone with a microscope could count. yet because some authority figure said there were 24 pairs of chromosomes in the human genome, everyone simply counted and recounted until they got 24 pairs, and then said, ah, I finally got it right!

Everyone, that is, until a single japanese student counted and recounted until he was certain that the cell he was observing only had 23 pairs. Itwas immediately announced that it had been discovered that some human cells only contained 23 pairs of chromosomes. This freed everyone to count with an open mind, and within two months it was announced that no human cells contained 24 pairs of chromosomes. They only contained 23 pairs.

So we know that supposed scientific facts are not as reliable as the cult of scientism would have us to believe.

 

[Mallon]

This was a very simple fact, something anyone with a microscope could count. yet because some authority figure said there were 24 pairs of chromosomes in the human genome, everyone simply counted and recounted until they got 24 pairs, and then said, ah, I finally got it right!

That's the great thing about science. You don't have to take the word of authorities on matters that can be tested empirically. It's because of the nature of science that it was revealed that humans have 23 pairs of chromosomes. Not despite it.
Unfortunately, the same empiricism doesn't extend to religious doctrine.

 

[metherion]

If you guys want to list some more things that you'd like known about, I'd be glad to chime in.

Metherion

 

[crawfish]

When I was in high school and in college, one of the best known scientific facts was that the human cell contained 48 chromosomes (24 pairs. My faith in science as a whole was seriously shaken when during my Junior year in the university it was suddenly discovered that the human cell only contained 46 chromosomes (23 pairs).

This was a very simple fact, something anyone with a microscope could count. yet because some authority figure said there were 24 pairs of chromosomes in the human genome, everyone simply counted and recounted until they got 24 pairs, and then said, ah, I finally got it right!

Everyone, that is, until a single japanese student counted and recounted until he was certain that the cell he was observing only had 23 pairs. Itwas immediately announced that it had been discovered that some human cells only contained 23 pairs of chromosomes. This freed everyone to count with an open mind, and within two months it was announced that no human cells contained 24 pairs of chromosomes. They only contained 23 pairs.

So we know that supposed scientific facts are not as reliable as the cult of scientism would have us to believe.

Science is always great about accepting change and admitted they were wrong once it's proven. I only wish it didn't take Christians so long to admit the same thing.

 

[gluadys]

OK, shernren and metherion. Here is something that has always puzzled me. How are scientists able to come up with extremely small measurements like the mass of an electron? What technology enables them to register such a small mass?

 

[metherion]

This takes a little bit to explain.

First, the mass of an electron is directly related to the charge on the thing. Each electron has a charge. Call it -1. It is impossible to have a number of electrons (say, X) and a charge of -X.5, or -X and 1/3.

So, Robert Millikan used a famous oil drop experiment (http://en.wikipedia.org/wiki/Oil-drop_experiment) to determine the charge or a single electron by finding the charge that was multiplied.
An example is if you can get 2 candy bars for 2$, 3 for 3$, 4 for 4$, etc you figure out it 1$ per candy bar. That's the way it works with charge units and electrons.

So anyways. You find the charge per electron. Then, J. J. Thompson used a cathode ray tube with a magnetic field to find the charge to mass ratio of electrons. So now you know the charge per electron, the total mass, and the total charge. The rest is simple algebra.

A similar experiment can be used to find the mass of a proton using hydrogen ions (which are just protons.) Neutrons are harder to measure since they don't have a charge. One method is to find isotopes that differ from another by only 1 neutron (such as Helium-3 or dueterium) and measure them compared to the normal elements (Helium 4 and hydrogen). Then measure the masses of those.


Metherion

 

[shernren]

... or, how come scientists think there are 23 pairs of chromosomes?

It's interesting to see how the story has been considered in popular understanding, compared to what actually happened.

When I was in high school and in college, one of the best known scientific facts was that the human cell contained 48 chromosomes (24 pairs. My faith in science as a whole was seriously shaken when during my Junior year in the university it was suddenly discovered that the human cell only contained 46 chromosomes (23 pairs).

Now I know that you couldn't have been in your junior year in university any time before 1921! It was in that year that Theophilus S. Painter published his paper (available here) detailing the "fact" that humans have 48 chromosomes. However, people had already been counting chromosomes since the 1890s. But of course you should be asking: what, exactly, are chromosomes? They're essentially bundles of genetic material at the highest stage of organization. However, you can't just open up a cell at any time and see chromosomes: they only bunch up in their iconic "X" shapes during mitosis and meiosis, when you can stain them with certain chemicals. (This will be important later.)

Anyways. In the 1890s, the first few counts made were actually lower than they should have been. Much lower: you'd expect 46, but in fact in the five early papers published, all but one counted 24! (The odd one out had 47 in ovaries and 48 in testes; surprisingly close.) So when Painter published his figure of 48 in 1921, again, it's a surprise he even got close. (More on that later.) In fact, part of his original paper reads:

"In my own materials the counts range from 45 to 48 apparent chromosomes, although in the clearest plates so far studied only 46 chromosomes have been found."
​

This was a very simple fact, something anyone with a microscope could count. yet because some authority figure said there were 24 pairs of chromosomes in the human genome, everyone simply counted and recounted until they got 24 pairs, and then said, ah, I finally got it right!

Oh no, it's not a simple fact at all. Above I quoted Painter himself counting anywhere between 45 and 48 chromosomes. Look at one of the diagrams he drew of those chromosomes. Is it any wonder why he couldn't get a fix on it?

It's a wonder he even got anywhere near the correct figure!

What made chromosome counting so difficult? Firstly, it was difficult to find fresh material. Remember that chromosomes only bunch up for counting when a cell is dividing. (How would scientists know? Manipulate cells into different states chemically, e.g. by starving them or feeding them extra nutrients, and then stain them to see what's there and what's not.) It's difficult to get samples of rapidly dividing human cells for study; the main source were reproductive organs (hence the reference to ovaries and testes earlier). Cytologists "literally waited at the foot of the gallows in order to fix the testis of an executed criminal immediately after death before the chromosomes could clump." Also, their method of preparing cells (paraffin sectioning) couldn't separate chromosomes out.

Over the next few decades more techniques appeared for cytologists: hypotonic shock could cause a cell's chromosomes to spread out before slide preparation, and colchicine could arrest cells so that more of them were stuck in the metaphase where chromosomes were bunched up.

Everyone, that is, until a single japanese student counted and recounted until he was certain that the cell he was observing only had 23 pairs. Itwas immediately announced that it had been discovered that some human cells only contained 23 pairs of chromosomes. This freed everyone to count with an open mind, and within two months it was announced that no human cells contained 24 pairs of chromosomes. They only contained 23 pairs.

He wasn't single, and he wasn't Japanese! Though it's no surprise that people might mistake him for one:

Joe Hin Tjio was born of Chinese ancestry in Java in 1919, which would make him 37 when he published the 1956 paper describing the fact that humans have 46 chromosomes. (Hardly a poster boy for "young researcher overturns established dogma" now, is he?) Granted, he was captured by the Japs when they invaded Southeast Asia during WWII.

And it wasn't "counting and recounting" that got him the number 46. In fact, the number had been reported earlier. A fellow student at the instute with Joe recalls being told by the director: "earlier that year [1955] Doctors Eva and Yngve Melander working on normal human fetal cells had problems with their chromosome preparation as they could only find cells with incomplete chromosome plates, the maximum number being 46." Which just goes to show that scientists don't always cover up anomalies! But anyways, it wasn't "counting and recounting" that got him 46. It was:

You don't have to count and recount with an image like that! It's obvious that this new picture is far more reliable than the old one on which the count of 48 chromosomes was based.

So we know that supposed scientific facts are not as reliable as the cult of scientism would have us to believe.

No, we know that old, unreliable "scientific facts" can always be uprooted by new, more reliable scientific facts.

Cool isn't it?

All information obtained from this article: The chromosome number in humans: A brief history (warning, might require subscription)

 

[juvenissun]

So this thread is dedicated to the question we should always ask, whether about evolutionary science or not:

How can scientists possibly know this??
​

and this is an open invitation to anyone, whatever your orientation on origins, to throw out those factoids that were drilled into your head in school which you never bothered to question or consider. How can scientists possibly know? Let's see!

Do you mean if one is or was not a scientist, then the person would not know?

If not, then what is the difference between a scientist and a non-scientist in knowing things? Is what known by non-scientist inferior in quality than those known by scientist?

May be your question should be: How can a non-scientist possibly know?

 

[shernren]

OK, shernren and metherion. Here is something that has always puzzled me. How are scientists able to come up with extremely small measurements like the mass of an electron? What technology enables them to register such a small mass?

This takes a little bit to explain.

First, the mass of an electron is directly related to the charge on the thing. Each electron has a charge. Call it -1. It is impossible to have a number of electrons (say, X) and a charge of -X.5, or -X and 1/3.

So, Robert Millikan used a famous oil drop experiment (http://en.wikipedia.org/wiki/Oil-drop_experiment) to determine the charge or a single electron by finding the charge that was multiplied.
An example is if you can get 2 candy bars for 2$, 3 for 3$, 4 for 4$, etc you figure out it 1$ per candy bar. That's the way it works with charge units and electrons.

So anyways. You find the charge per electron. Then, J. J. Thompson used a cathode ray tube with a magnetic field to find the charge to mass ratio of electrons. So now you know the charge per electron, the total mass, and the total charge. The rest is simple algebra.

A similar experiment can be used to find the mass of a proton using hydrogen ions (which are just protons.) Neutrons are harder to measure since they don't have a charge. One method is to find isotopes that differ from another by only 1 neutron (such as Helium-3 or dueterium) and measure them compared to the normal elements (Helium 4 and hydrogen). Then measure the masses of those.


Metherion

In the first place, how do you know that you can't have a fractional charge? To us today, it's obvious that atoms are made of electrons around a nucleus, and thus it only "makes sense" that atoms can have say 1 electrons'worth or 2 electrons'worth of charge, but not say 1 and a half electrons'worth of charge.

What Milikan did was ionize oil droplets (in modern terms strip electrons away from them), and then measure their charge - which is a story in itself. He found that their values were quantized, and at regular intervals!

Think of it this way: suppose you stood outside a candy store and looked at how much people were being charged (what a pun. heh heh.) for the sweets they bought. You don't get to look inside the shopping bag, though! The first person's bill is $1.80. The next person's bill is $1.20. The next, $2.40. The next, $3.00. After a few hours you find that everybody's bill comes in multiples of $0.60. It's pretty obvious, then, that on that particular day the candy shop only sold things with discrete prices of $0.60 - nothing cost anything else, or else you would've gotten someone with a bill which didn't add up to a multiple of $0.60.

So in the same way, Milikan discovered quantization, and interpreted his results to mean that atoms gain or lose charge in terms of electrons being pasted on or peeled off, and they went on one at a time - you can't get half an electrons'worth of charge.

Now, how to measure the mass of an electron? Well, suppose you have an electric field in space. The amount of force an electron experiences depends on its charge. However, how much acceleration it experiences depends both on the force and on its mass! (All other things being equal, it takes a lot more force to push a truck than it takes to push a small car.) And since acceleration determines velocity, maybe we could measure the velocity of an electron accelerating in a known field, and then find out its charge - basically, find out how fast a given field makes an electron move; the bigger an electron's mass, the more "push" you need to get it to a certain velocity.

In normal life you measure velocity by setting a starting point and an ending point, and then seeing how much time it takes to get between them. However, I think electrons would zip by far too fast for that to work. Enter magnetism! The magnetic force on an electron depends on its charge and its velocity; in particular, if an electron traveling at some speed enters a uniform magnetic field, it ends up turning a corner, and the radius of that bend allows you to calculate its mass and velocity.

And so that's how. =)

 

[metherion]

Do you mean if one is or was not a scientist, then the person would not know?

If not, then what is the difference between a scientist and a non-scientist in knowing things? Is what known by non-scientist inferior in quality than those known by scientist?

May be your question should be: How can a non-scientist possibly know?

I was treating it more as a "how on earth was this figured out in the first place?!" type thread. And, to be fair, many of the basics we take for granted in science, like the mass of an electron, we figure out the first type by scientists. So an alternate but equally valid phrasing of the question would be "how on earth did scientists figure this out for the first time?!"

Metherion

note: I just noticed this. You know the whole "i before e except after c" thing? science has the i before e after a c. Odd.

 

[metherion]

Oh, and shenren, you officially win the "better at phrasing things than me" award. You can stop rubbing it in. .

Metherion

(that was a joke. Don't stop with the posting. It was awesome.)

 

[gluadys]

Thanks, guys.

Metherion: "science" also has two syllables. The i before e thing applies when you have the single sound "ee" or "ei" (as in "eight").

I before e except after c or when sounded like "ei" as in "neighbour" or "weigh".

Of course there are still another dozen or so exceptions like "weird" and "gneiss".

 

[metherion]

Ah, so since the split is sci/ence and not scie/nce, it's all good.

Cool.

And you're welcome!

Metherion

 

[shernren]

Do you mean if one is or was not a scientist, then the person would not know?

If not, then what is the difference between a scientist and a non-scientist in knowing things? Is what known by non-scientist inferior in quality than those known by scientist?

May be your question should be: How can a non-scientist possibly know?

My main point was that a lot of times people as non-scientists know science without reasons. Not because non-scientists are dumber or worse off or anything. It's just that a lot of times, non-scientists tend to take scientists on authority ... and then when other non-scientists say "Hey, why are you taking scientists on authority? You can't possibly trust them on evolution / the age of the earth / XYZ!"

That's the point of this thread I guess. A peek into how the scientific method ends up working in real life. Are there hiccups? Sure. Mistakes and wrong turns and dead ends? Definitely. There is even visible evidence of peer pressure preventing scientists from getting to the right end-point - plenty of cases. (Although peer pressure is not always as important as you may think it is.)

My point is that I don't want people to think that scientists pull things out of thin air. That's the impression people always get from science education in schools. And it's dead wrong. Plenty of single sentences in any 7th grade science textbook have hundreds of years' worth of research behind them.

 

[juvenissun]

My point is that I don't want people to think that scientists pull things out of thin air. That's the impression people always get from science education in schools. And it's dead wrong. Plenty of single sentences in any 7th grade science textbook have hundreds of years' worth of research behind them.

When I teach an introduction level class, I commonly give facts without giving much explanation. However, I also tell them that these facts are results of many many research efforts. I do not sense, so far, that students take these facts as statements pulled from air. And I do not think you should worry about that.

My point is: Non-scientist continuously discovered truth in a non-scientific way: not too logic, not too rigorous, but come up with truth that endures the test of time. How is it possible? To scientist, any such understanding is always treated as an unreliable conclusion or simply as an imagination.

Think about this problem by another fact: Many scientists believe in prophecy (which, indeed, is pulling conclusion directly from air). Why? To me, it says that science is only a trowel in a construction project. It does not see at all how would the project look like at the end.

Sorry if I diverted the attention of your OP.

 

[Biblewriter]

That's the point of this thread I guess. A peek into how the scientific method ends up working in real life. Are there hiccups? Sure. Mistakes and wrong turns and dead ends? Definitely. There is even visible evidence of peer pressure preventing scientists from getting to the right end-point - plenty of cases. (Although peer pressure is not always as important as you may think it is.)

As you mention the scientific method, I will point out that one critical step in the scientific method is to design a test to determine whether or not the hypothesis is correct.

Yet the origin of species is untestable, therefore it is not true science.

 

[metherion]

The origin of species is untestable?

You mean that we can't observe new species arising?

You, sir, are mistaken.

In APA format,
de Wet, J. M. J. 1971. Polyploidy and evolution in plants. Taxon. 20:29-35.

Digby, L. 1912. The cytology of Primula kewensis and of other related Primula hybrids. Ann. Bot. 26:357-388.

Owenby, M. 1950. Natural hybridization and amphiploidy in the genus Tragopogon. Am. J. Bot. 37:487-499.

Karpchenko, G. D. 1927. Polyploid hybrids of Raphanus sativus L. X Brassica oleraceae L. Bull. Appl. Botany. 17:305-408.


Karpchenko, G. D. 1928. Polyploid hybrids of Raphanus sativus L. X Brassica oleraceae L. Z. Indukt. Abstami-a Verenbungsi. 48:1-85.

Rice, W. R. 1985. Disruptive selection on habitat preference and the evolution of reproductive isolation: an exploratory experiment. Evolution. 39:645-646.

Rice, W. R. and E. E. Hostert. 1993. Laboratory experiments on speciation: What have we learned in forty years? Evolution. 47:1637-1653.


Rice, W. R. and G. W. Salt. 1988. Speciation via disruptive selection on habitat preference: experimental evidence. The American Naturalist. 131:911-917.


Rice, W. R. and G. W. Salt. 1990. The evolution of reproductive isolation as a correlated character under sympatric conditions: experimental evidence. Evolution. 44:1140-1152.


are just a few of the scientific papers detailing the observation of new species of several types of plant and fruit fly.



A quick google search will bring up more.



Metherion

 

[holdon]

The origin of species is untestable?

You mean that we can't observe new species arising?

You, sir, are mistaken.

In APA format,
de Wet, J. M. J. 1971. Polyploidy and evolution in plants. Taxon. 20:29-35.

Digby, L. 1912. The cytology of Primula kewensis and of other related Primula hybrids. Ann. Bot. 26:357-388.

Owenby, M. 1950. Natural hybridization and amphiploidy in the genus Tragopogon. Am. J. Bot. 37:487-499.

Karpchenko, G. D. 1927. Polyploid hybrids of Raphanus sativus L. X Brassica oleraceae L. Bull. Appl. Botany. 17:305-408.


Karpchenko, G. D. 1928. Polyploid hybrids of Raphanus sativus L. X Brassica oleraceae L. Z. Indukt. Abstami-a Verenbungsi. 48:1-85.

Rice, W. R. 1985. Disruptive selection on habitat preference and the evolution of reproductive isolation: an exploratory experiment. Evolution. 39:645-646.

Rice, W. R. and E. E. Hostert. 1993. Laboratory experiments on speciation: What have we learned in forty years? Evolution. 47:1637-1653.


Rice, W. R. and G. W. Salt. 1988. Speciation via disruptive selection on habitat preference: experimental evidence. The American Naturalist. 131:911-917.


Rice, W. R. and G. W. Salt. 1990. The evolution of reproductive isolation as a correlated character under sympatric conditions: experimental evidence. Evolution. 44:1140-1152.


are just a few of the scientific papers detailing the observation of new species of several types of plant and fruit fly.



A quick google search will bring up more.



Metherion

I haven't read those articles, but from the titles of it I can gather that this is not about new species. Merely selections, polyploidizations and hybridizations.

To begin to address such an issue, you first have to define what you mean by species. And that's another can of worms...

 

[Mallon]

I haven't read those articles, but from the titles of it I can gather that this is not about new species. Merely selections, polyploidizations and hybridizations.

Selection, polyploidy, and hybridization are mechanisms that bring about speciation. They are not alternatives to speciation.
Maybe you should read the articles?