Recent content by paulcretu

Damn! I had a feeling something is not right! Of course, I can't have the same 0.4 kPa throughout the whole tube length because the air would compress due to gravity in the lower part just like in atmosphere. Then I put a lid and access is done by airlocks. Someone above mentioned...

Thank you all for your replies. At 40km altitude, it's almost vacuum. Yes, the air will flow in but the pressure would be 0.4 kPa. I was not sure if the buoyancy would apply though, if the system is open at top. But then if you submerge a tall glass in water with its open end above, the...

But leaving buoyancy aside (I've done some calculations below and the results are not good) and the stability of the tower, would this "vacuum" system work? I mean an open end in space (40 km tall, 0.4 kPa atmospheric pressure), a tightly closed end at ground level, and the pressure is equalized...

Hello everyone, I am thinking of a thought experiment about a so-called "space tower" but don't have enough information to estimate the numbers. I understand the material strength needed for such high structures is huge, because of the weight of the structure. But what if the "tower" would be...

Thank you, DH. I did not read the paper cited by Bandersnatch, but only the equation he suggested as explanation. Now I understand, that according to you the paper argues AGAINST this equation... That leaves us with no explanation for the statement in the OP article ("A less massive moon would...

It has historical roots from the ancient times. The calendar has been reformed several times in order to compensate the moon's period. I've seen a reply here with the history part: http://answers.yahoo.com/question/index?qid=20110130164834AAEsSEb

Okay. Thank you all. So this: D = GM^2 / [(m+M)v^2] ignores masses are not point masses. But I suppose it's valid for non-point masses too (with some corrections maybe)? And this: T[FONT="Comic Sans MS"]z=(3/2)GM12(R5/R6)k2sin2εg takes into account the tidal torque. And as I understand...

Thank you Bandersnatch, and thanks for the reply. The assumption is there, but I also get your point about the drifting: Well this is about geophysics and astronomy but I was more interested in the physical part. Maybe I've posted in the wrong section? I'm no expert either but ... if...

Hi everybody, I've registered to PF because after searching the web and this forum too, I couldn't find a clear answer to my dilemma. I've read this article but something seems wrong: http://www.scientificamerican.com/article.cfm?id=half-mass-moon What if the mass of the Moon would be...