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Does the mass of the earth change - yes, but not be a great deal. The mass is reduced by the loss of the top of the atmosphere, which escapes into space ( and is blown by the solar wind, I gather ). At the same time, we are bombarded by dust, some of which is captured by the earths gravity, and adds to the mass.
Which means that it does fluctuate, although whether it tends to increase or decrease I don't know. I guess it tends to decrease, meaning that the earth is gradually being eroded into space.
The fly in a jar will increase the weight of the closed jar system, because the flapping of its wings, will provide a pressure on the base of the jar, which will be reflected in extra weight. This downward pressure needs to be equal to the weight of the fly, because that is what keeps it airbourne.
The mass of the jar-fly system would also be unchanged, as mass relates to the amount of matter in the object. The behaviour of the objects is then irrelevant.
That's my take on these at least.
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Quote:
Originally posted here by dstevens1958
Back to the earth mass thingy. This is my view on this subject:
Though I'm sure it does change slightly, I don't think its enough to even measure (even if we took the earth, and dropped it onto a scale on something like the sun that has gravity to make the scale work).
My reasoning:
The Earth, with a few exceptions, is basically to the extent of my still completing Grade 12 knowledge is a closed system. (Though we should all know it isn't because we accept energy input from the sun, thus its open) But aside from that, its basically closed. Things seem to be pretty much at equilibrium right now, (eg. while water is evapourating into the air, water is condensing back into liquid water from the air, etc) and since matter cannot be created nor destroyed, only converted from one form to another, the weight technically shouldn't change. Same goes for energy. Therefore, other than stuff falling into our atmosphere from outside the planet and us sending stuff into orbit, it should stay the same.
Oh well, I'm just a wee little grade 12 student who doesn't know much anyways. ;)
About the fly thingy, I also don't believe it is changing the weight of the jar while its flying. I think its just converting energy. (Using chemical energy stored in its body to flap its little wings creating kinetic energy, and it is also potential because it can fall if its wings fail to create lift, etc.) If anything, I think it would make the jar slightly lighter, as the fly would displace air (unless its a closed system) which would reduce the pressure and therefore reduce the weight of the jar. (Because the air is hitting the sides, and assuming the fly isn't)
I hope I made sense, lol, its late for me. (almost midnight, I can't think now)
Hmmm, maybe I can use this as a science experiment. Oh heck, I will just ask my science teacher if I remember tomorrow! ;)
Peace,
Dave
1. earth is very much not a closed system, we gain mass on earth via metior impacts, space dust ect. we lose mass via satalight launches (unless they come crashing back to earth) and atmosphirac bleed off We also lose a lot of mass into energy that is bleed off (useualy as heat) in fires (natural and things like inernal cumbustion engins) and in nuclear reactions..
. s for the fly the weight in the jar would increase, the mass of the fly would exert an equal amount of presure on the air to kep it aloft, that presure would be exerted as a force on the jar adding to its weight.
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Great discussion. Here are a few factoids from many sources.
The earth’s weight and mass are in constant flux. Particles are coming and going changing mass; and weight is associated with gravitational pull from planets, the moon, the earth and the sun. All of which are constantly changing. Meaning the relation to earth's mass and gravitational alignments in reference to it's location with other solar objects is in constant change.
Earth is hit and absorbs thousands of objects daily. Last estimate on the amount is 40,000 metric tones a year. WOW! That is a lot of weight and there was original concern about earth becoming too heavy and altering its orbit. This would be very bad! It makes sense, because only a small percentage of what hits earth actually leaks into space. But if you do the math and use the average estimate of the earth at 6 sextillion metric tones, that large amount of incoming mass and weight becomes rather trivial at that size of numbers. The actual current number is:
5,972,000,000,000,000,000,000 tons
Now when you look at 40,000 metric tones of incoming mass/weight it doesn't look so bad. Some large ocean going ships are bigger than that when loaded. The amount of incoming mass versus outgoing mass is large but on the planetary scale it’s a very tiny amount.
Here is another interesting fact. Light particles bombard the planet continually, but light is overly accepted as having zero mass as a property. However; when plants convert the energy from light into chemicals, mass increases very slightly but it does change. I wonder how many other influences there are. There are many that haven't been mentioned like the direct effect on CME (since we just had one) on increased space ejection of matter from the upper atmosphere, decaying organic matter, etc.
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decaying organic matter...forgot about that one, it generates a stupidlylarge amount of heat...infact all life uses up a large amount of heat, every time we eat we take some matter and turn it into energy to keep our bodies at body temperature.
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Quote:
Originally posted here by Schrodinger
The fly in a jar will increase the weight of the closed jar system, because the flapping of its wings, will provide a pressure on the base of the jar, which will be reflected in extra weight. This downward pressure needs to be equal to the weight of the fly, because that is what keeps it airbourne.
The mass of the jar-fly system would also be unchanged, as mass relates to the amount of matter in the object. The behaviour of the objects is then irrelevant.
This is how I see it, very good explination.
