Aces High Bulletin Board
General Forums => The O' Club => Topic started by: rogwar on December 06, 2007, 05:34:08 PM
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Was down around 7,200 feet below the surface of the earth for about an hour today. Seven minute ride both ways. Ride seemed a bit fast as well, like the fastest elevator I'd ever been on.
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The moon is over 250,000 miles away, and we've sent people there! The center of the earth, on the other hand, is less than 4,000 miles away, and not a single visitor yet.
tsk tsk
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Oh, it's not that there's no visitors, it's just that it's a permanent move and you wouldn't like the neighbors.
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What do you think would happen if you got to the center of the earth. I mean would you float because of all the gravity pushing from all sides.
I know there is Hot Lava down there, but what if there wasnt?
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Gravity would be pulling from all directions, not pushing down from all directions.
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Thank you. I forgot to proof read:(
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Originally posted by rogwar
Was down around 7,200 feet below the surface of the earth for about an hour today. Seven minute ride both ways. Ride seemed a bit fast as well, like the fastest elevator I'd ever been on.
So what were you doing down there? Mining of some type?
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Originally posted by Jebus
What do you think would happen if you got to the center of the earth. I mean would you float because of all the gravity pushing from all sides.
I know there is Hot Lava down there, but what if there wasnt?
Actually, it's theorized that the Earth's core is composed of molten Nickel-Iron.
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Originally posted by Chairboy
Gravity would be pulling from all directions, not pushing down from all directions.
not true. gravity sure would be pulling everthing down to the center, but an object in the very center would feel the effect of everything around pushing down on it.
so infact jebus was right and superbrainchairperfectcitizen boy was wrong ;)
i think...
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That would FREAK me out being so far down. Honestly. The thought of all that rock and dirt above me...nope. Not into it.
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Batfink, ask yourself what causes gravity.
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the mass of an object, and all objects produce a field of gravity. that is besides the point.
what jebus was pondering was what would happen to a person at the very center of the earths gravity and there was a hollow airspace at the center to make this possible.
now all the earth's gravity is 'pulling' towards the center as you correctly state. this is what anyone can learn from a science book. now try and take a step off some author's shoulders and think for yourself with a little imagination for a change.
'Pulling' denotes that you have seperation between yourself and an object. if you have a ball on a string 10ft away you can pull it right on to you. when the ball gets to your fingers you cannot 'pull' the ball any further unless you move your hand seperately from the ball, or the other way around....or both at the same time. i dont think the earth will be planning any vastly new orbits for the remainder of the suns life.
so when you are 'pulled' to the very center of gravity and gravity is acting all around you from every direction it simply cannot be 'pulling' you any further without moving the whole earth or you seperately.
so we can only assume that gravity when completely surrounding you from all directions to remain static could be considered the only possible 360 degree 'push' gravity can produce. just call it negtive scale zero gravity and i think that yes you would just float there, like jebus first said. in space you float because surrounding gravity fields are so weak, inside the center of a huge gravity field you float from 100% concentration of the gravity's source.
but hey, i have only given the topic a half hour of thought. i could always be wrong although hell, it looks good from where i wrote it. :cool:
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Here's the problem, the center of the planet is not where everything is being pulled. He's float in the center, but not because he was being pushed 'down' equally in all directions, it'd be because he's being pulled by all the mass around him. If you cut the planet in half while you were in that same spot, the side of the planet that's still there would be 'down' to you. You're being pulled by the mass, and the person in the center is being pulled in all directions by the mass around them.
So put the snarky comments aside and smack yerself on the forehead because I'm not there to enjoy the privilege.
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VALE Inco
Creighton Nickel Mine
Sudbury, Ontario
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Not to try to 1-up you, but the most beautiful place I've ever been is 95 feet beneath the surface of the Caribbean Sea scuba diving in the national marine park off the coast of Cozumel.
But I guess a deep scary mine could be pretty too.
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(quote) Oh, it's not that there's no visitors, it's just that it's a permanent move and you wouldn't like the neighbors. (unquote)
Excellent perspective, Saxman! :rofl
(Incidentally, do you play alto, tenor, or bari?)
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i think youre totaly wrong chairboy. your original tartly correction of jebus's fun hypothesis got under my skin. you want to crush his and maybe even my fun because you think you truly know what happens at the center of gravity just like any scientist can have a clue for sure....yeah.
my version makes perfect sense, and you still seem to think that if an object is at the center of the earths gravitational field without the physical matter of the earth to get in the way that you could describe gravity as 'pulling' you anywhere.
my comments were not intentionaly snarky i was just light spirited same as jebus when he suggested something that we can never proove for real anyhow. i just saw you as jumping in to crush the idea before we had any fun with it. geuss the fact that you have said some pretty funny things in anger directed at some people im friends with here maybe puts me in a hostile mood with you so i appologise for that.
but youre still wrong and whoever backs you up is wrong for your original wording correction, i stand by:
if no there is no seperation between the very center source of a force and an object then 'pulling' is not a word that can be applied unless one or both forces or objects are in another plane of motion independant from each other.
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Originally posted by Curval
That would FREAK me out being so far down. Honestly. The thought of all that rock and dirt above me...nope. Not into it.
Holy CRAP Rogwar!
I'm on the verge of a panic attack just thinking about being that deep!:eek: I hope you are paid very, very well for your services.
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Originally posted by rpm
Holy CRAP Rogwar!
I'm on the verge of a panic attack just thinking about being that deep!:eek: I hope you are paid very, very well for your services.
Serious question - has anyone ever sent anything down there ?
I mean, how can we really know for sure what's down there until we actually send something down there....
Assuming we sent down a highly resilient web cam at the end of a proverbial very long stick... would we be greeted with zero gravity, or the maniacal smiling face of the dark lord himself ?
Shamroc
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Ok, maybe a little multimedia presentation will sort this out.
Force due to gravity is an inversely affected by the square of the distance between the center of mass.
(http://www.glenbrook.k12.il.us/gbssci/phys/Class/circles/u6l3c3.gif)
Now you could view the earth as a number of really really small but equal masses; think really really small pieces of rock and each is a separate object that just happens to be placed really really close to other really really small rocks.
(http://i193.photobucket.com/albums/z39/clerick44/fig1.jpg)
But, if you assume the Earth is a sphere of constant mass (which it isn't), you can combine all those smaller masses into one big mass and the math will work out the same. Plug in some simple values and you will see that this is true.
(http://i193.photobucket.com/albums/z39/clerick44/fig1a.jpg)
However, things get a bit tricky once you place one object within the other, because now you have to start looking at it as a bunch of smaller masses again. This is because the entire mass of the one object is no longer "pulling: the second object in the same direction. Simply illustrated, it would be like placing one object equidistant from two identical masses.
(http://i193.photobucket.com/albums/z39/clerick44/fig2.jpg)
Now, if we extrapolate this to the idea of an object at the center of he Earth, and treat the Earth no as one large mass, but as an infinite number of smaller, but equal, masses you could visualize it like this. (not to scale)
(http://i193.photobucket.com/albums/z39/clerick44/fig3.jpg)
Each one of those masses wants to pull the poor balloon towards it, but since they are all theoretically the same mass, and the balloon is hypothetically in the exact center of the smaller masses, the balloon will stay where it is.
I have oversimplified things and ignored a number of other factors...
The Earth is not a true sphere
The Earth's density and mass fluctuate from point to point.
The extreme heat and pressure at he center of the Earth would render this moot.
The object placed at the center of the Earth would also have to be a perfect sphere for this to work.
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(http://www.tfw2005.com/boards/images/smilies/this_thread_is_useless_without_pics.gif)
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Originally posted by shamroc
Serious question - has anyone ever sent anything down there ?
I mean, how can we really know for sure what's down there until we actually send something down there....
Assuming we sent down a highly resilient web cam at the end of a proverbial very long stick... would we be greeted with zero gravity, or the maniacal smiling face of the dark lord himself ?
Shamroc
Nothing has ever come close to the center of the earth and i doubt we ever will. The tremendous heat and pressure would destroy anything barring some ultra-futuristic device.
To help illustrate:
A skydiver falling at terminal velocity would take approximately 32 hours to fall to the center of the earth (ignoring the change in gravity he would experience on the way down).
The deepest hole drilled (as far as i could Google) was about 15 kilometers, that means we have only penetrated .002% of the Earth's crust.
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Originally posted by rogwar
VALE Inco
Creighton Nickel Mine
Sudbury, Ontario
Interesting! So was it warm down there? How's the air pressure? Do you have to contend with air composition issues, like.. too much oxygen ( as opposed to the 'thin air' at Mile-high?)
Never done any research on deep air depths ( probably know more about deep sea stuff ).
And the real important question.. what would the equivalent be to the mile-high club?
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Batfink, with respect, you're mistaken, and your "anyone who disagrees with me is wrong because they're disagreeing with me" stance is kinda weak.
Clerick's post is spot on (and of course he's right about the uneven distribution of mass) and his diagrams should help you understand what's happening.
There's nothing magical about the center of the mass that makes it the place exerting the pull. It's the mass itself that exerts the pull, not the very center. So if you were at the center of an undifferentiated mass, you'd be pulled in all directions by the mass around you.
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hmmm chairboy and clerick both wrong here im afraid. if you are at the centre of our (hollow) earth you are not being pulled/pushed outwards towards the mass around you, you are being pulled/pushed towards the centre of mass of the entire object.
easy proof - move 1 foot from the CoM and you will return to it. If you were being pulled by the mass around you, you would keep on going out until you hit the "roof" of the inner chamber.
the pull/push thing is just linguistics, as bat alluded to.
and back OT rogwar thats a great trip :aok - how did it feel? noticeably warmer down there? get bends on the way back up?
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Maybe it's semantics at this point, RTHolmes, because if you're at the center of mass and then you move to one side, there's more mass pulling at you on one side so you float back to the center. But when you're at the center, you're being pulled equally in all directions.
Compare this with Batfink's assertion that some force is "pushing down on you".
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Originally posted by RTHolmes
easy proof - move 1 foot from the CoM and you will return to it. If you were being pulled by the mass around you, you would keep on going out until you hit the "roof" of the inner chamber.
I'd like to see an empirical test that proves your first point. According to my thinking, and i am still mulling this one over, i would have to believe that your second assertion is correct and you would indeed wind up on the "roof." Since the gravity increases/decreases with distance, moving closer to one part of the "chamber" would increase the force pulling you to that side of the chamber and decrease the force exerted by the opposite side. Now, this is assuming that there is no actual mass at he CoM but a hollow chamber, if it were a solid object then i do believe that you would return to the CoM.
the pull/push thing is just linguistics, as bat alluded to.
Gravity is an attractive force, NOT a repelling force. It is not like electrical charges or magnetism, it will NOT push! Its important to keep the terms correct for clarity.
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I sketched this up quickly, pardon the crudeness:
(http://hallert.net/images/gravity-sucks.png)
In figure A, the object is at the exact center of mass. The arrows indicate that the force being exerted on it is towards mass. Every atom in the universe attracts every other atom, it's just big lumps of it that make a noticeable force.
When the spherical object is in the center like in figure A, it would essentially be 'weightless' because it's being pulled equally in all directions.
If you move it to one side, like in figure b, then there's less mass on the left side exerting force and more mass on the right side, which would tend to pull it back towards the center, at which point it would appear weightless again. It's not, actually, it is experiencing something like G/pi^3 (my math might be wrong, no coffee yet), but it's from all directions, so in practice, it appears weightless.
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Originally posted by Chairboy
Batfink, ask yourself what causes gravity.
If you can come up with the answer to this you will become famous. A real answer that is, not that it is an intrinsic quality of mass. Or, something equally undefinitive like it's the bending of space by mass. You will need to answer why and how mass bends space.
In one of my less lucid moments I imagined that space is full of holes with the pressure of time forcing mass through them creating the illusion of gravity. I know, I should switch from scotch to beer.
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Originally posted by Jebus
I know there is Hot Lava down there, but what if there wasnt?
Yes you would float, but just in a sea of molten nickel!:aok
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The pressure would likely supersede any gravitational effects. That and of course the heat. But I would think the closer you got to an objects center the less gravity it would have. But then again...I dont know, you'll have to ask Mr. Whoopee that one Chumly :)
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Originally posted by Chairboy
Batfink, with respect, you're mistaken, and your "anyone who disagrees with me is wrong because they're disagreeing with me" stance is kinda weak.
Clerick's post is spot on (and of course he's right about the uneven distribution of mass) and his diagrams should help you understand what's happening.
There's nothing magical about the center of the mass that makes it the place exerting the pull. It's the mass itself that exerts the pull, not the very center. So if you were at the center of an undifferentiated mass, you'd be pulled in all directions by the mass around you.
ok i think i understnad now! :D
well it was fun while it lasted.
i dont really have a clue
hehe
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Ok, after a rigorous morning spent doing calculus, i have to admit that i was wrong on one point, the object would tend to return to center, but only by the smallest margin. And i am trying to set up the problem in a number of other ways to see if i was right about me being wrong about me being right.... wait... aww screw it.
I know i have a copy of Mathematica around here somewhere....
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you make me head hurt. i would ponder that the orginal poster is a miner of some sort. you never answered that question
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Originally posted by kilz
you make me head hurt. i would ponder that the orginal poster is a miner of some sort. you never answered that question
None of us will probably go anywhere as cool as where the OP did, so we compensate with diagrams and arguments! :D
In case it got missed in the kerfuffle, that's awesome rogwar. Any pictures?
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mmmm... fun topic! :)
I think...
The person is also a mass thus they have their own self-generated non-uniform gravity field.
If there were a hollow little sphere at the center of the earth and a person was put into that little hollow sphere, they would slowly gravitate to the surface of the sphere but it would feel almost like zero gravity.
Nothing is perfect, thus even the slightest pico-unit of mass unbalance would eventually cause the person to drift to the surface.
This would also be the case if two planets of equal mass were held 10 feet apart and a person was placed exactly between them. The person's own gravity field would affect the outcome as to which surface they would eventually gravitate.
Even if a perfectly uniform solid sphere were placed inside that empty sphere at the earth’s center and the mass of the earth was perfectly uniform it would still gravitate to one side; that side being in the direction of the Sun and its gravitation field.
I think the "effect" of a hollow sphere at the center of the earth would be the closest thing to no effective earth gravity at all... if mass of the surrounding earth were perfectly uniform, it zeros itself out from all angles.
Fun thing to ponder! :)
TIGERESS
Edit: FYI, I didn't read any of the posts past the initial few when I wrote this... that would have made it not as much fun.
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Geez, y'all are talking about this without being forced? Tips a hat.
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You will need to answer why and how mass bends space.
Gravity as a geometry of space-time still makes more layman sense than any hypothetical alternative. Definitely better than gravity rays or some such..
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Where do we apply the tachyon pulse?
We can have the array ready in an hour.
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lol this innocent post really opened a can of worms :D
oookay...
Originally posted by Chairboy
Compare this with Batfink's assertion that some force is "pushing down on you".
Originally posted by clerick
Gravity is an attractive force, NOT a repelling force.
my point was that Bat was talking about the effects of a force on a body, and as Newton worked out a while ago every force has an equal and opp reaction, so push/pull are both right. non-physicists generally only see one side of the reaction, so our language reflects this.
Got to admit that although I was right about the gravitational force acting from the CoM, I forgot another thing Newton worked out - inside a hollow sphere there is no net gravitational force. so displace a foot from the CoM and you will stay there :cool: smart guy that Newton :aok
I still want to know if its hot down there :D
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You just won't be satisfied poking and prodding into the center of the Earth until you let all the air out, will you.
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The only reason why i ask is when I was in high school. My high school science teacher asked,"what if a stainless steal tube was cut right threw the center of earth. And you jump in the tube, what would happen if you hit the center?" That one question set up for a years worth of discussion and debate. That is the only reason why I brought it up.
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Assuming that the tube is a vacuum, you'd blast through the center about 20 minutes after you jumped. You'd be moving at a good clip, too, about 17,700 mph.
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Originally posted by Chairboy
Assuming that the tube is a vacuum, you'd blast through the center about 20 minutes after you jumped. You'd be moving at a good clip, too, about 17,700 mph.
Did you adjust for diminishing gravitational force once he leaves the surface?
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Yep.
(http://hyperphysics.phy-astr.gsu.edu/hbase/mechanics/imgmech/eh2.gif)
The gravity at any radius r less than Rearth will be linearly proportional to the distance from the center.
(per http://hyperphysics.phy-astr.gsu.edu/hbase/mechanics/earthole.html)
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Ok, how about for rotational inertia of a spinning earth? Did we assume no friction in this tube?
That was a little vague, I'll clarify. Because on the surface of the earth you are moving faster than a point say halfway to middle of the earth you will exert force on the side of the tube as you fall. If we create a maglev tube perhaps this force becomes negligible.
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What the hell did you two just say?:confused:
English Boy
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Originally posted by Jebus
What the hell did you two just say?:confused:
English Boy
The ride to the middle of the earth will be like a water slide, only scarier. :D
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The temp was around 75 to 80 degrees. Zero at the top. They pump huge amounts of air down into the mine.
It will eventually bottom out around 10K feet underground.
The wild thing is there are like miles of tunnels at the 7,000 foot range.
Had to go down there to recommend some equipment. I work with the mining and cement industries in the area of instrumentation and process control.
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Originally posted by Chairboy
Yep.
(http://hyperphysics.phy-astr.gsu.edu/hbase/mechanics/imgmech/eh2.gif)
The gravity at any radius r less than Rearth will be linearly proportional to the distance from the center.
(per http://hyperphysics.phy-astr.gsu.edu/hbase/mechanics/earthole.html)
ok ok uncle! uncle! you win
:D
Originally posted by Chairboy
(http://hallert.net/images/gravity-sucks.png)
although....
this diagram shows the center object being pushed equaly in all directions.
your arrows should be reversed? or is the 'pull' of gravity expected to be coming fom the surface of the earth and not the center?
confusing eh?
think of an object in orbit, the arrows would need to be pointing inward toward the CoG to make sense. the object in orbit is being pulled by gravity the same as us falling out of a tree.
but not by the earth's surface, the earths surface acts as a barrier to stop us being pulled to the center, hence we can walk on it.
so really are your arrows not showing a push from the center in all directions, and not a pull from the surface of the sphere?