[ARCHIVED THREAD] - Gravity... How does it work? (Page 1 of 2)
Posted: 12/13/2010 8:53:29 AM EDT
| Hypothetically, lets say we were able to bore a hole through the center of the earth and out the other side.. Lets say we were able to make a vertical tunnel that could withstand the heat, and shield you from the molten rock.... What would happen if you were to jump in??? (assuming you didnt hit the sides) |
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It utilizes the same theory as a thermos bottle. If it's hot it keeps it hot. If it's cold it keeps it cold.
Gravity...if it's light it keeps it light. If it's heavy it keeps it heavy. The real question is, "How do it know"? It might be better if we ran a long tread mill through the center of the earth and put some bathroom scales on it with a know weight on it. Camera equipment could record the reading as it traveled from Detroit to China. |
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You would oscillate falling from one side of the tunnel to the other until air resistance slowed you down, leaving you stuck at the center of the earth. ETA: Actually, you'd hit the sides, but you specified that can't happen in your question. I had a girl friend one time that was so big that I could only hit the sides. |
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You would oscillate falling from one side of the tunnel to the other until air resistance slowed you down, leaving you stuck at the center of the earth. The rotation and orbit of the earth might keep you perpetually oscillating.  Yea, you'd hit the sides of the tunnel. But the OP specified that we ignore that. |
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fall, reach terminal velocity, go through center, slow down, go backwards, reach terminal velocity, go through center, etc till you settled in the middle? This is what I thought at first.. But think about it, what would keep you in the center? The earths mass as a whole creates gravity. Its not like the center of the earth is a giant magnet or has more gravity and gets stronger as your reach it.. Perhaps its to early to be drinking and pondering such complex things... |
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fall, reach terminal velocity, go through center, slow down, go backwards, reach terminal velocity, go through center, etc till you settled in the middle? This, only I think that terminal velocity would be slower the closer you get to the center. I'm no physicist, but I think that the closer to the center you are, the less gravity there will be on the side you are moving to, thus slower speeds. |
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Quoted: Hypothetically, lets say we were able to bore a hole through the center of the earth and out the other side.. Lets say we were able to make a vertical tunnel that could withstand the heat, and shield you from the molten rock.... What would happen if you were to jump in??? (assuming you didnt hit the sides) |
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fall, reach terminal velocity, go through center, slow down, go backwards, reach terminal velocity, go through center, etc till you settled in the middle? This is what I thought at first.. But think about it, what would keep you in the center? The earths mass as a whole creates gravity. Its not like the center of the earth is a giant magnet or has more gravity and gets stronger as your reach it.. Perhaps its to early to be drinking and pondering such complex things... The force of gravity is neutral at the center. The left half is pulling as much as the right half, so you don't move. In that case, you'd actually "fall" towards the moon, perhaps a few miles, until Earth's gravity counteracted it. |
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Quoted: Quoted: fall, reach terminal velocity, go through center, slow down, go backwards, reach terminal velocity, go through center, etc till you settled in the middle? This is what I thought at first.. But think about it, what would keep you in the center? The earths mass as a whole creates gravity. Its not like the center of the earth is a giant magnet or has more gravity and gets stronger as your reach it.. Perhaps its to early to be drinking and pondering such complex things... You're right that at the center of the Earth you would feel a net sum gravity of 0, but once you move from the center out towards either end of the hole, you'll feel increasing gravity towards the center of the earth. |
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What if you lined the tunnel with steel and wore a magnetic suit, while holding a pelican and making a call on your cell phone...during a rainbow?? 
I'd say feed the pelican first. You might be gone awhile. Holy Shit! 
I love this place!  Best place on the Webz for a laugh.
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Quoted: Quoted: You would discover a lost tribe of women with large breasts, flat heads, and beer. You would never return. I've heard tales about this tribe. They are known as the "Wanaknobajobba tribe". It is said that they laugh on their knees. I've heard that their best and brightest have pistol grip ears. |
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fall, reach terminal velocity, go through center, slow down, go backwards, reach terminal velocity, go through center, etc till you settled in the middle? This is what I thought at first.. But think about it, what would keep you in the center? The earths mass as a whole creates gravity. Its not like the center of the earth is a giant magnet or has more gravity and gets stronger as your reach it.. Perhaps its to early to be drinking and pondering such complex things... The force of gravity is neutral at the center. The left half is pulling as much as the right half, so you don't move. In that case, you'd actually "fall" towards the moon, perhaps a few miles, until Earth's gravity counteracted it. If there is less gravity in the center, wouldn't you "fall up" just as far..... So if you were to jump say off a 10 foot latter, shouldn't you pop out the other side? |
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The actual “how” part is unknown. Suffice it to say that one of the properties of matter is that it is weakly attracted to all other matter in the universe through the force of gravity. There is no known way to block off this force or shield against it.
Mass is what generates gravity. A metric ton of lead and a metric ton of feathers all generate exactly the same gravity. The closer you are to the object the stronger the attraction is. Gravity follows the “inverse square law.” If you double your distance from the object the force drops to one forth what it was. If you half your distance then the force you feel increases by four times. This force is generated on an atom by atom basis. Fortunately, if you have a sphere of uniform density (or of layers of uniform density) you can assume that gravity acts from a point in the center of the object. This works until you start to dig beneath the surface of the object. When you do dig beneath the surface of the object, you start leaving mass above you. In a body of uniform density this would mean gravity would steadily decrease as you dug deeper. Once you reached the center you would be weightless, gravity would be zero. Earth is not of uniform density however. The iron core is about 8 times as dense as water while the mantle rocks are probably more like 3-4 times as dense as water. This means that, on Earth, gravity actually increases as you dig deeper until you get about 1,000 miles down. Then it starts decreasing again. (That figure was from memory, don’t quote me on it exactly.) At the center, of course, you have zero gravity. And, if Earth were a giant shell that was empty in the middle then everything in the hollow space would be weightless too. We are about 4,000 miles from the center of the earth and we feel 1G of gravity. If we were 4,000 miles above the earth’s surface then the force of gravity would be 0.25G. The reason astronauts a mere 200 miles up are weightless is that they are in orbit. Gravity is constantly pulling them down. They are falling, but their forward momentum is so great that they keep missing the earth due to the fact that earth is round. If there was a 200 mile high tower on Earth then you could stand on the top and would feel most of Earth’s gravitational force. Weightless astronauts in the shuttle would pass by at some 18,000 miles an hour. That’s the big problem with getting into orbit. The 200-300 mile trip is no big deal. Getting to orbital speed is the challenge. Now for black holes… If you dig beneath the surface of earth gravity decreases. But what happens if you compress the earth? Imagine if you compressed the earth to half it’s current diameter. Now we would be 2,000 miles above the center and we would feel 4g of gravity. Compress it in half again and we are 1,000 miles from the center feeling 16g. At 500 miles we would experience 64G and at 250 we would feel 256G…. Compress earth enough and gravity would get so strong at the surface that even light couldn’t escape. Earth would be a black hole. You might have to compress the entire earth down to the size of a marble for this to happen though. But earth’s mass wouldn’t have increased at all. So the total gravity wouldn’t have gone up one bit either. Only the surface gravity would have increased. A satellite in orbit around the earth would stay in its orbit as if nothing had happened. |
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fall, reach terminal velocity, go through center, slow down, go backwards, reach terminal velocity, go through center, etc till you settled in the middle? This. This, also it doesn't matter from what two points on the planet to dig to, the time it takes for gravity to get you from one end to the other is the same. |
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You would discover a lost tribe of women with large breasts, flat heads, and beer. You would never return. I've heard tales about this tribe. They are known as the "Wanaknobajobba tribe". It is said that they laugh on their knees. I've heard that their best and brightest have pistol grip ears.
They were also cross breed with dolphins and snakes, their teeth fold back and they can breath through their ears. At the center of the earth your beer will never go flat. |
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You would oscillate falling from one side of the tunnel to the other until air resistance slowed you down, leaving you stuck at the center of the earth. ETA: Actually, you'd hit the sides, but you specified that can't happen in your question. Not if you bored the hole from the north pole to the south pole! |
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fall, reach terminal velocity, go through center, slow down, go backwards, reach terminal velocity, go through center, etc till you settled in the middle? This is what I thought at first.. But think about it, what would keep you in the center? The earths mass as a whole creates gravity. Its not like the center of the earth is a giant magnet or has more gravity and gets stronger as your reach it.. Perhaps its to early to be drinking and pondering such complex things... A good way to understand how gravity works is to take a plastic sheet and suspend it evenly and flat. take something with a heavy weight and set it in the middle. The dimple that is produced by its mass in the plastic is basically what gravity is. If you were to set a bb on the plastic, it would roll down towards the center of the mass. Now just picture this in all dimensions and you have gravity. |
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I'd sell it as the world's biggest bungee jump. With the added bonus of not needing a bungee to do it. Of course there would be a tramway cable in there to pull you back out after you settled in the middle. With a JATO rocket ignited most of the way through, it could also be the fastest way to the other side of the earth. |
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Quoted: Quoted: What if you lined the tunnel with steel and wore a magnetic suit, while holding a pelican and making a call on your cell phone...during a rainbow?? I wanna take a penguin, pelicans scare me Hmmm. I wonder what type of bird a certain moderator here would take? Hmmm.
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The actual “how” part is unknown. Suffice it to say that one of the properties of matter is that it is weakly attracted to all other matter in the universe through the force of gravity. There is no known way to block off this force or shield against it. Mass is what generates gravity. A metric ton of lead and a metric ton of feathers all generate exactly the same gravity. The closer you are to the object the stronger the attraction is. Gravity follows the “inverse square law.” If you double your distance from the object the force drops to one forth what it was. If you half your distance then the force you feel increases by four times. This force is generated on an atom by atom basis. Fortunately, if you have a sphere of uniform density (or of layers of uniform density) you can assume that gravity acts from a point in the center of the object. This works until you start to dig beneath the surface of the object. When you do dig beneath the surface of the object, you start leaving mass above you. In a body of uniform density this would mean gravity would steadily decrease as you dug deeper. Once you reached the center you would be weightless, gravity would be zero. Earth is not of uniform density however. The iron core is about 8 times as dense as water while the mantle rocks are probably more like 3-4 times as dense as water. This means that, on Earth, gravity actually increases as you dig deeper until you get about 1,000 miles down. Then it starts decreasing again. (That figure was from memory, don’t quote me on it exactly.) At the center, of course, you have zero gravity. And, if Earth were a giant shell that was empty in the middle then everything in the hollow space would be weightless too. We are about 4,000 miles from the center of the earth and we feel 1G of gravity. If we were 4,000 miles above the earth’s surface then the force of gravity would be 0.25G. The reason astronauts a mere 200 miles up are weightless is that they are in orbit. Gravity is constantly pulling them down. They are falling, but their forward momentum is so great that they keep missing the earth due to the fact that earth is round. If there was a 200 mile high tower on Earth then you could stand on the top and would feel most of Earth’s gravitational force. Weightless astronauts in the shuttle would pass by at some 18,000 miles an hour. That’s the big problem with getting into orbit. The 200-300 mile trip is no big deal. Getting to orbital speed is the challenge. Now for black holes… If you dig beneath the surface of earth gravity decreases. But what happens if you compress the earth? Imagine if you compressed the earth to half it’s current diameter. Now we would be 2,000 miles above the center and we would feel 4g of gravity. Compress it in half again and we are 1,000 miles from the center feeling 16g. At 500 miles we would experience 64G and at 250 we would feel 256G…. Compress earth enough and gravity would get so strong at the surface that even light couldn’t escape. Earth would be a black hole. You might have to compress the entire earth down to the size of a marble for this to happen though. But earth’s mass wouldn’t have increased at all. So the total gravity wouldn’t have gone up one bit either. Only the surface gravity would have increased. A satellite in orbit around the earth would stay in its orbit as if nothing had happened. I should have paid attention in high school and gone to college... Things like this I find really intresting. Math and science were my best subjects, however once i discoverd bewbies and booze that all went to hell... 
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fall, reach terminal velocity, go through center, slow down, go backwards, reach terminal velocity, go through center, etc till you settled in the middle? This is what I thought at first.. But think about it, what would keep you in the center? The earths mass as a whole creates gravity. Its not like the center of the earth is a giant magnet or has more gravity and gets stronger as your reach it.. Perhaps its to early to be drinking and pondering such complex things... Gravity calculations based on center of mass. You're at the earths surface, so you have potential energy relative to the earth's center. You jump in and fall accelerating as you go. As you fall, your potential energy becomes kinetic energy. With air, you'd reach some kind of terminal velocity that will cause energy to bleed off faster, in a vacuum, you'd just keep accelerating until you reached the center. Either way, you'd be at maximum velocity as you passed through the center. As you approach the opposite side, you are decelerating at the same rate you accelerated, but you lost some amount of energy, so you will come up just short of the opposite crust. You are back to all potential energy again. Basically, you're a pendulum and the exact same behavior applies. What this means is each trip back and forth will take the same amount of time, even as the distance traveled becomes less. A pendulum will always complete a swing in the same amount of time for a specific beam length. |
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The earths mass as a whole creates gravity. Its not like the center of the earth is a giant magnet or has more gravity and gets stronger as your reach it.. . Bingo!!!!! The "down" of gravity is not towards the center of the earth as we think it is but towards the earth as a mass. At the center of the earh you will still have the gravity attraction to the mass. |
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You would oscillate falling from one side of the tunnel to the other until air resistance slowed you down, leaving you stuck at the center of the earth. ETA: Actually, you'd hit the sides, but you specified that can't happen in your question. Not if you bored the hole from the north pole to the south pole! But I don't like the cold. |
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You would discover a lost tribe of women with large breasts, flat heads, and beer. You would never return. I've heard tales about this tribe. They are known as the "Wanaknobajobba tribe". It is said that they laugh on their knees. I've heard that their best and brightest have pistol grip ears.
They were also cross breed with dolphins and snakes, their teeth fold back and they can breath through their ears. At the center of the earth your beer will never go flat. What self respecting Morlock would allow their beer to go flat? |
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The earths mass as a whole creates gravity. Its not like the center of the earth is a giant magnet or has more gravity and gets stronger as your reach it.. . Bingo!!!!! The "down" of gravity is not towards the center of the earth as we think it is but towards the earth as a mass. At the center of the earh you will still have the gravity attraction to the mass. But you will have equal amounts of mass in all directions, hence the net gravitational force is zero. |
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fall, reach terminal velocity, go through center, slow down, go backwards, reach terminal velocity, go through center, etc till you settled in the middle? This is what I thought at first.. But think about it, what would keep you in the center? The earths mass as a whole creates gravity. Its not like the center of the earth is a giant magnet or has more gravity and gets stronger as your reach it.. Perhaps its to early to be drinking and pondering such complex things... Gravity calculations based on center of mass. You're at the earths surface, so you have potential energy relative to the earth's center. You jump in and fall accelerating as you go. As you fall, your potential energy becomes kinetic energy. With air, you'd reach some kind of terminal velocity that will cause energy to bleed off faster, in a vacuum, you'd just keep accelerating until you reached the center. Either way, you'd be at maximum velocity as you passed through the center. As you approach the opposite side, you are decelerating at the same rate you accelerated, but you lost some amount of energy, so you will come up just short of the opposite crust. You are back to all potential energy again. Basically, you're a pendulum and the exact same behavior applies. What this means is each trip back and forth will take the same amount of time, even as the distance traveled becomes less. A pendulum will always complete a swing in the same amount of time for a specific beam length. So in theroy, with the correct height, prior to jumping in the hole, you could fall through the earth and pop out the other side... |