pz

Another good point.

In the immortal words of John Vanderzyden, "Calculations will not be of much help. Rather, understanding of principles and proper application will."

The irony is palpable, is it not?

lpetrich

One almost expects him to say what Austrian mining engineer and crackpot cosmologist Hanns Hoerbiger once said:

Calculation can only lead you astray.

[ November 09, 2002: Message edited by: lpetrich ]</p>

Happy Wonderer

Give that man a prize! He almost has found his error, although he doesn't realize it yet. (Although I'm a bit concerned by the "typical warm, sunny conditions", do clouds cause low pressure systems?) Simply because a measurement is small in relationship to another doesn't mean it can be "safely ignored" (one of your favorite terms, for some reason.) Oddly enough, <a href="http://express.howstuffworks.com/questions-helium.htm" target="_blank">this website</a> might help...

Now, let's read the quote from the article that you are trying to lambaste:

Is this really "false and grossly misleading"? Three quick questions to consider:

1) What units are referenced here? Is it P or PSI?
2) What does PSI stand for?
3) What is the surface area of the average human body, in square inches?


HW

[ November 09, 2002: Message edited by: Happy Wonderer ]

[ November 09, 2002: Message edited by: Happy Wonderer ]</p>

RufusAtticus

Vander,

My point is that you only calculated the external pressure change due to gravity. You also need to calculte the internal pressure change due to gravity, and compare them to see if the difference is significant. Your argument is that gravity affects the CV system of the fetus. In your post, you calculated the external pressure found that it is not significant, then concluded that it doesn't cancel out internal pressure due to gravity. However, the key calculation missing from your post is how does gravity affect the internal hydrosatic pressure in the fetus. Without that calculation you can't make any conclusions about the effect of gravity.

When you do your calculations, you are getting yourself confused by plugging in numbers before you have finished working out the equations. I suggest you go back do all your calculations and then plug in numbers.

~~RvFvS~~

MrDarwin

Trying to get this discussion nominally back on topic, the issue was whether gravity has a significant influence on the blood circulation of the fetus. After several pages of discussion, John Vanderzyden still has not demonstrated that it does.

Bubba

Mr. Darwin, perhaps rather than trying to convert him intellectually we should opt for a dogma transplant instead.

Bubba <img src="graemlins/banghead.gif" border="0" alt="[Bang Head]" />

Dr Rick

John Vanderzyden has asserted that the fetal circulation cannot be improved upon and so by implication must be intelligently designed. He has argued that improvements would not work by asserting all sorts of unnecessary restrictions and false principles upon the physiology and physics of the fetal circulation.

The objections he has argued and subsequently had shot down include false thoracic cage access issues, unneeded additional heart valves, imagined circulatory pressure changes, useless ligaments, weird assumptions about oxygen requirements, and even aesthetics.

His most recent and so far persistent assertion, that gravity limits or restricts the umbilical vessels to the abdomen, seems to be the dumbest one, however. It's obvious even to the casual observer that the position of a gestating fetus changes continuosly, both has it moves and grows within the womb, and as its mother stands, lies, and carries on activities of daily living.

If gravity had a profound impact on fetal circulation, no fetus could survive the twists and turns it makes within the womb or its mother moving about during the day and lying down to sleep at night.

Perhaps the most ironic thing about this whole issue is that even if gravity did play the important role John imagines that it does, he hasn't made a case for why that would limit the umbilical cord to the abdomen and prohibit an improved thoracic connection.

Rick

[ November 09, 2002: Message edited by: rbochnermd ]</p>

Asha'man

Yet again, Vanderzyden demonstrates that he can read a physics text, but utterly fails to understand what the text is saying.

Buoyancy is completely unaffected by the size of the container. An object that will float in a 100 gallon water tank will not suddenly sink when placed in a 10 gallon water tank.

If an object displaces 5lbs of water, then it will have 5lbs of buoyant lift. Period. The relative size of the container vs the object is completely irrelevant!

As the fetus grows, the effect of buoyancy increases in direct proportion to the displacement of the fetus.


<img src="graemlins/banghead.gif" border="0" alt="[Bang Head]" />

Asha'man

Vanderzyden is also confused by the effect of gravity on pumping a fluid through a closed loop. As long as the fluid does not change density during the cycle, the effect of gravity on such a loop is irrelevant.

Imagine a circular length of tubing, perhaps a meter long. Lay the tubing flat along the ground, so the circle is horizontal. Now fill the tube with water and add a pump to the system to create circulation.

Now, stand the circle up on end, so that the circle is vertical. What is the net effect? Nothing. The gravitational energy required to raise the water up is exactly canceled by the gravitational energy gained by lowering the water on the other half of the cycle.

<img src="graemlins/banghead.gif" border="0" alt="[Bang Head]" />

pz

That's the problem with getting all your science out of a several thousand year old book written by a bunch of goatherders. You miss all those recent developments from the young hotshots, like Archimedes.