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Author Topic:   Scientific Fact versus Interpretation
crashfrog
Member (Idle past 1467 days)
Posts: 19762
From: Silver Spring, MD
Joined: 03-20-2003


Message 49 of 144 (295682)
03-15-2006 6:31 PM
Reply to: Message 48 by Faith
03-15-2006 6:30 PM


Re: conjecture vs simplified description
My point was AS USUAL very simple AND obvious.
And also, as usual, very wrong.

This message is a reply to:
 Message 48 by Faith, posted 03-15-2006 6:30 PM Faith has not replied

  
crashfrog
Member (Idle past 1467 days)
Posts: 19762
From: Silver Spring, MD
Joined: 03-20-2003


Message 118 of 144 (296608)
03-19-2006 1:48 PM
Reply to: Message 1 by Faith
03-15-2006 9:51 AM


Interpretation as Fact
On the thread about the Grand Canyon there appeared to be enough information for me to try to point out what bugs me the most about how scientists present their views, confusing their facts with their interpretations of the facts.
I'd like to give an example of a legitimate, scientific, legally-accepted example of an interpretation of fact being accepted as a fact itself: DNA "fingerprinting."
Almost everyone has seen a "DNA fingerprint" on TV, like on CSI or Law and Order:
Almost nobody knows what they're actually looking at. I'll try and summarize the process.
1) A sample of DNA, such as that found at a crime scene, is "amplified" by a process called "PCR"; this chemical process uses enzymes and selective "primers" to replicate specific sequences of DNA millions of times. This results in millions of copies of a specific gene which makes it a lot easier to perform tests on it. The DNA is stained with a visible dye (which is often UV-florescent to improve the photographic results.)
2) Enzymes called "restriction enzymes" cut up these copies of DNA by recognizing specific sequences of base pairs (called "restriction sites"). When they see that sequence, they cut the DNA at that position. The DNA in our genes contains long sequences of repeating base pairs accumulated from mutation called "introns." They're irrelevant to the production of proteins but they are inherited by offspring. These nonsense sequences differ in length between individuals, but are almost identical in length between persons who have inherited the same copy of the gene (in other words, are related.)
3) The approximate length of these sequences is determined by a chromatographic process called "gel electrophoresis." DNA molecules have a slight negative electical charge, so when placed in a conductive solution between a positive and negative terminal, they move towards the positive electrode. A gel made out of a sticky sugar called "agarose" is created, basically just like jello. Like a fisher's net, small segments of DNA slip through but longer segments get tangled up. As a result the smaller segments move through the gel quickly, while long segments take longer. This spreads them out from top to bottom in order of length. In the image above, the longer sequences are at the top and the smaller are at the botom. Each band represents a concentration of stained DNA.
4) We photograph (because the DNA and gel are perishable) and interpret the results. When we compare the pictures of two samples, we can determine if they represent the results of this process performed on two copies of the same gene (actually, several genes at once are usually used). If they match up we know one of two things:
A) The samples share the same gene because they're samples from the same person (this would be how we might prosecute a rape from semen left at the scene and a blood sample from a suspect), or
B) The samples share the same gene because they're samples from two people who are related. Basic genetics can tell us, based on how many genes they share, the specific nature of the relation (father and child, brother and sister, maternal or paternal uncle, etc.)
Remember this is all based on the interpretation of the black bands in the photograph above, but that interpretation is accepted fact in every civil and courtroom in the country. Accepting interpretation as fact is not unreasonable, when that interpretation is the only reasonable one from the facts at hand.

This message is a reply to:
 Message 1 by Faith, posted 03-15-2006 9:51 AM Faith has replied

Replies to this message:
 Message 119 by Faith, posted 03-19-2006 4:59 PM crashfrog has replied

  
crashfrog
Member (Idle past 1467 days)
Posts: 19762
From: Silver Spring, MD
Joined: 03-20-2003


Message 123 of 144 (296670)
03-19-2006 9:47 PM
Reply to: Message 119 by Faith
03-19-2006 4:59 PM


Re: Interpretation as Fact
Crash, there are a million ways to TEST those results and that is why they are accepted in courtrooms.
Test how? I mean, these techniques are literally the sole evidence that is putting people in jail. There's no other test possible than the PCR-RFLP process I've described above>
Exactly what results do you think can be tested? If we come upon a rape-murder and the only evidence is semen, and we bag the suspect on his DNA and convict, but he never confesses, exactly what do you think we can test?
In the case of the ToE and OE there is no opportunity to test an interpretation because it's all about one-time events in the distant past.
But that's exactly what's going on here. We're using this one single proceedure to come to an interpretation - that a suspect committed a crime in the past - and there's no other way to test it. We just have our guess about this one-time event, and it's enough to put a man in jail forever or put the needle in his arm.
This message has been edited by crashfrog, 03-19-2006 09:48 PM

This message is a reply to:
 Message 119 by Faith, posted 03-19-2006 4:59 PM Faith has replied

Replies to this message:
 Message 124 by Faith, posted 03-19-2006 10:19 PM crashfrog has replied
 Message 140 by Modulous, posted 03-20-2006 11:11 AM crashfrog has replied

  
crashfrog
Member (Idle past 1467 days)
Posts: 19762
From: Silver Spring, MD
Joined: 03-20-2003


Message 126 of 144 (296676)
03-19-2006 10:28 PM
Reply to: Message 124 by Faith
03-19-2006 10:19 PM


Re: Interpretation as Fact
It HAS BEEN tested millions of times with KNOWN people and situations.
You're taking this on faith, or what? What testing are you referring to? If you put a guy in jail based on DNA evidence, how do you verify that the testing was valid?

This message is a reply to:
 Message 124 by Faith, posted 03-19-2006 10:19 PM Faith has replied

Replies to this message:
 Message 127 by Faith, posted 03-19-2006 10:31 PM crashfrog has replied

  
crashfrog
Member (Idle past 1467 days)
Posts: 19762
From: Silver Spring, MD
Joined: 03-20-2003


Message 128 of 144 (296680)
03-19-2006 10:43 PM
Reply to: Message 127 by Faith
03-19-2006 10:31 PM


Re: Interpretation as Fact
YOu do it on the basis of what you KNOW from millions of OTHER situations where you KNOW the circumstances, the donor of the DNA, etc etc etc.
I still don't understand. Can you be clearer? What do all those "millions" of other situations have to do with this specific situations?

This message is a reply to:
 Message 127 by Faith, posted 03-19-2006 10:31 PM Faith has not replied

  
crashfrog
Member (Idle past 1467 days)
Posts: 19762
From: Silver Spring, MD
Joined: 03-20-2003


Message 142 of 144 (296802)
03-20-2006 1:20 PM
Reply to: Message 140 by Modulous
03-20-2006 11:11 AM


Re: DNA evidence
As the case of the invalid who was arrested for committing a burglary 200kms from his home confirms.
An interesting case, but he was later exonerated on the basis of DNA evidence so I'm not sure what your one example proves. But you're right - it's rare. Usually there's other physical evidence, eyewitnesses, complaining victims, etc. It's far more often the case that convictions are overturned based on nothing but DNA.

This message is a reply to:
 Message 140 by Modulous, posted 03-20-2006 11:11 AM Modulous has not replied

  
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