What is gravity? What is the effect of a solar eclipse?

i could have sworn that half of what F_alk said came directly from Stephen Hawkings’s “A Brief History of Time”

@Imperious:

Does any increase in barometric pressure have any effect on gravity? treat your answer as if we are dealing in a sealed room with all other things being equal.

The reason why i asked this was during my research i found estimates that the barometric pressure about 200-400 million years ago was about 3 times what it is today, while oxygen levels were at 35% (currently 21%). Of course there were major changes to oxygen levels during the 5 episodes of an asteroid hitting the earth and killing countless species.

I honestly do not believe that barometric pressure has an effect on gravity per se.  Regardless of the barometric pressure of the Earth, moon, Saturn, Sun, etc. they will interact with each other based on their masses. 
Now the relative effects on objects by an increased barometric pressure might have the effect of an increase in gravity as even air has mass, and an increase in barometric pressure would cause an increase in the mass of all air surrounding us - as the vast majority is above, it would have a crushing effect.  Consider diving underwater.  You have increased your surrounding “barometric pressure”.  The reason your ears hurt is because this pressures your tympanic membranes inwards and the pain from the stretch receptors can only be mitigated by rising nearer the surface, or by equalizing the pressure by forcing air through your eustacian tubes by blowing against pursed lips and sealed nares. 
Does this make any sense?  F_alk?

Considering the atmosphere effectively ends about 100 miles above the earth (which is about 7,000) miles in diameter, and considering most gases condense to hundreths of their previous volume when frozen/solidified; even an atmosphere 10X denser than todays should produce an insiginificant change in gravity.  Also, this thicker atmosphere (if it actually existed) is probably still locked inside the earth in some form or other.

As far as physiological changes, I would suspect you should see more streamlining (as in marine animals) since a denser atmosphere would make movement more difficult due to air resistance and make the effects of wind storms more severe.  Smaller lungs might be a possibility due to an easier transfer of oxygen/CO2 due to the higher pressure.  The effects on the tympanic membranes should be insignificant IMO because once you are stabilized at the higher/lower altitude or pressure all is well.  The problems here are only with rapidly changing pressures.

Smaller lungs might be a possibility due to an easier transfer of oxygen/CO2 due to the higher pressure.

Ok so oxygen transfer of a higher pressured world in LARGE animals is easier, while they have less ability to get air in a lower pressure?

Ok so oxygen transfer of a higher pressured world in LARGE animals is easier, while they have less ability to get air in a lower pressure?

Well, a higher pressure (all else being equal) means there are more oxygen molecules in a given surface area.  Therefore, for a given animal size, the lungs could potentially be smaller proportionally.  It would not necessarily make life for large animals more possible because this might not be the limiting factor with regards to animal size.

The September 95 issue of Discover magazine has an article on the fluctuations in the oxygen levels during the Carboniferous (p. 32).  I don’t recall any literature being cited, but the 35% number was used as a reason for the huge insects of that period.  The theory goes that as the concentration of oxygen increases so does the size of the animal that can be supported by diffusional oxygen transfer (also known as the squared/cubed law). This may help explain why they got so huge. So the question is rather why did they get large and secondly after the Asteroid hits every 150 million years, why dint they simply come back? IT the answer has to explain both land and sea animals, because after all the heat wave from a 100 megaton event would bake the Earth except for things burrowed in the ground or in the deep sea. (e.g. giant crabs and squids)

I am not trying to hyjack this thread, but i dont see a “good” answer for the demise of Dinasours only explained by Asteroids, because this event has occured at least 4 other times in earths history, based on geological  records.

I am not debating the reason why the O2 level changed. I am trying to state the reason why the Dinasours died in both land and sea other than saying “a big rock” hit the earth so 100% were killed by that alone… or are their other factors?

1. O2 levels didnt compensate for the ability of larger animals to breath
2. Barometric Pressure and its effects of lungs for large animals.

@F_alk:

i could have sworn that half of what F_alk said came directly from Stephen Hawkings’s “A Brief History of Time”

I don’t hope so. If so, then it didn’t happen on purpose (and i have to change my view on the book, as i didn’t like it that much).

i read the book again last night, well skimmed it is a better term (dont really feel like reading it again, i think we both kind of agree on its quality) while skimming through it i found similarites, but nothing to get my imaginary underwear in a bunch.

i will say i like the topic ,i have always liked gravity, here on earth it is basically the only constant.