If a plane flies in a straight line, why does it follow the curvature of the earth and not go out into space?
439775
The plane is actually following the curvature of the earth, which only seems to look straight - exactly the way ships do.\nIF it would follow a geometrical straight line, it would actually increase altitude, leaving the sphere of the atmosphere, and make it look like a perpetuous climb (gain of altitude) to a LOCAL observer ...\nBut the so cold level-flight, is a question of keeping altitude, or keeping touch with a certain air pressure, which means a constant distance to the earths center of gravity, making the path a curve...\nSo, a plane is not flying a straight line - strict geometrically (and GLOBAL) speaking!
9991
To a first-order approximation the Earth is round.  This\nis due to gravity.  Gravity pulls with equal strength in all\ndirections; therefore any variations from a spherical\nshape will lead to gravitational forces that\nbring the shape back into that of a sphere.\n \nThis is without considering the rotation of the earth,\nhowever.  The rotation of the earth adds centrifugal\neffects, which cause the earth to bulge slightly at\nits equator and flatten slightly at its poles.\n(This is like twirling a rock on the end of a string\nand then letting go--the rock flies away from the\ntwirler.)  Because of these centrifugal effects, the\ndistance from the center of the earth to the surface\nof the earth is about 0.33% shorter at the poles\ncompared to the equator.
564572
Because of the curvature of the earth.
340102
I read all the answers and chewed over what ZAHIER had to say...as you know we are unable to leave earth to travel into deep space with out first using our gravity to gain speed and break away from our own gravity pull.... NO we cant at this time travel in a straight line into space, gravity will alter your course creating curves.
506185
Firstly they travel with the speed which is faster than light. Secondly there is always a short-cut available.\n For example: We think that a straight line is the shortest distance between two points which is actually incorrect in reality. If the plane is u-shaped (and not straight) then the shortest diatnce will get reduced.\n Hence they might have also got short-cuts to reach our earth.
1086455
The first effect is centifugal force.  It is caused by the answer of the second question where the ball goes in a straight line.  The ball moving on it's own will continue in a straight line due to inertia unless an outside force acts upon it (the string).  The ball swings at the end of the string because it is trying to go straight, which would carry it away from you, but the string keeps it turning.  The same effect happens to space craft in orbit.   They go in a circle and would go off in a straight line except that gravity holds them.
1036772
depends on your definition of flying, which is commonly known as moving through the air using wings or an engine, but good question though. but IMO flying is controlled falling :), since if you look at the physics of it, you are constantly trying to counter gravity which is towards the center of the earth.
939350
The height of the plane does not affect the acceleration, only the angle.\n\nAcceleration will be constant as long as the force acting on it is constant. The force contributing to acceleration (gravity) is constant.
444020
Good question! I think no because everything moves within the atmosphere. Such as 8 hour long airplanes. If they travel the opposite direction of the earth's rotation, it wouldn't just stay still over the same exact spot over the ocean if it traveled 1000mph. good question, but that's what i predict using prior knowledge. Plus, i think it's gravitational force that makes every object move at the same time along with the earth itself. It may have to do with Earth's magnetic field, i don't know.
964062
Hi. It is bent at any height above zero. Look at the horizon from a spacecraft and you'll see this. The bending gets reduced as you approach zero height, at which point it is a flat circle.
1141344
Because the plane moves along with the earth because of inertia, even after it leaves the ground. If it didn't, then when you jumped straight up, you would land about a hundred meters from where you started.
12149
****Edit based on further details from asker *****\nSailing around the world is sailing within the sperhical confines of our planet.  If there were no athmosphere, or gravity, then we would simply fall off the earth.  However, as gravity is pushing us down, and is affecting the winds, ect within the athmosphere, we are bound to the surface of the water.  \n\nEven though a sphere is included in the define of spheroid, it is a type of spheroid, not the inclusive answer.  The fact that gravity pushes down on us from all around, mainly because the earth is spinning so fast, and other more complicated reasons; the sphereoid holds whatever is on it's surface down to adhere to the confines and shape of such a surface.\n\nEven if the world were flat, or a flattned sphereoid, we woudln't fall off, instead, we'd loop around to the otherside becasue gravity wouldn't allow us to actually 'drop' off the side of the cliff.  The inverse gravity on the other side of the plane would pull us to it's confine, or surface.\n\nSo, there's your answer.  Sorry i didn't get it more clear the first time.\n\nMathamatically you can say that gravity pushes us from all around using a tangent direction.  That means that no matter the point you are on this earth, gravity is pushing down on you within the same confines as any other like region.  As to falling off the earth, if gravity didn't exist, we wouldn't 'fall' exactly; we would more likely be thrown or float off the earth (thrown if the world is spinning).\n\n****End Edit.******\n\nThe world indeed is a sphere, but it is not a perfect sphere, due to the rotation of the earth around it's axis, as well as the rotation of the earth around the sun (central axis), the spinning and speed of the planet make it more of a spehere that jiggles, sometimes squeezed, and sometimes elongated.  But, not by much :) Just a bit :)
520200
assumeing that one leg wasnt longer than the other, and that you couldnt fly and just walk straight out into space, you WOULDNT end up back where you started if walking in a straight line, because the earth isnt perfectly round...  you would have to walk east-west on the equator only
1083768
Good question.  The reason is because gravity isn't actually pulling the light.\n\nGravity is much like a trampoline.  Imagine a bowling ball in the middle.  The ball creates an indention.  If you rolled a marble across the trampoline, and it traveled into that indention, it would curve around not because the bowling ball pulled it, but because it was following the contour of the trampoline.\n\nThis is how mass affects spacetime.  The sun or any mass for that matter creates an indention in spacetime.  The Earth is traveling in the Sun's spacetime indention, so it isn't the Sun pulling the Earth at all.\n\nWhen light enters the indented space, it follows the contour of the curved space, which is why it bends.
1031879
The earth turns from east to west. So when a plane flies from South Africa to Australia (or from any place to the east) the earth turning is against the direction of the plane which makes the distance decrease and so the time. and it is vice versa for the other way, the plane flies from Australia to South Africa, and the earth turns and moves South Africa in the direction of the plane so it becomes nearer and will take less time to reach.
821350
Think of it this way:  Once the plane is off the ground it is part of a mass of air that is likely moving in some direction (think wind).  The airplane moves through this mass of air at a constant velocity depending upon the power setting, load factors, etc.  The speed of the airplane is independent of the speed of the air mass.  The speed of the airplane over the ground consists of its speed in the air plus or minus the speed of the air mass over the ground adjusted for the direction the airplane is moving in relationship to the speed and direction the air mass is moving. \n\nA couple of examples might help.  Suppose that the airplane flies at 200 knots (about 230mph).  It is heading due east.  The airmass is also moving due east at 30 knots.  So, the ground speed of the airplane is 230 knots.  If the airplane were heading northeast then the ground speed would be 200 knots of air speed plus 21 knots (NE component of an air mass moving at 30 knots due east).  If it were heading due west then the ground speed would be 170 knots (200-30).\n\nWhat if it were heading directly to a spot 200 nautical miles to the north?  It would take slightly over an hour to get there.  Why?  Because to get to a spot due north on the ground the airplane would have to head west a bit to keep from going east of the spot it was flying to because the air mass was moving east.  In fact, it would take about 61 minutes and the airplane would have to head about 9 degrees west of north to keep from moving east.  The moving air mass would keep it on the north-south line between the starting point and destination.\n\nGot it?
337086
The planets are actually trying to move in a straight line at a high speed due to the intertia from some force long ago.  When two objects are moving by each other, their gravity interacts and pulls them toward each other, bending the path that would otherwise be a straight line.  If they are too massive and too close, the gravity pulls them so much that they collide.  If things are balanced just right, the path is bent into a complete ellipse.  It's an ellipse instead of a circle because the sun is actually also being pulled a tiny bit toward the earth, as well.\n\nYou could consider gravity to be sort of a "perpendicular inertia", and the planets would revolve around the sun FOREVER if there were no other forces involved.