level question

jakdelad

considering we live on a globe,orb, ball,sphere
how can we define anything as being level?

NoQuarter

Because the Earth is not a perfect sphere. Hills or mountains can be level, or even concave. And of course, anything that is man made could be level in that we could make it with the earths curvature in mind, and alter the shape of the object to counter the earths curve!

jakdelad

NoQuarter wrote: »

Because the Earth is not a perfect sphere. Hills or mountains can be level, or even concave. And of course, anything that is man made could be level in that we could make it with the earths curvature in mind, and alter the shape of the object to counter the earths curve!

hmmmm
but where would we get our levels from
what point do we calibrate from,, what marker

Agonist

Perpendicular to the force of gravity?

jakdelad

Agonist wrote: »

Perpendicular to the force of gravity?

we can get a level from gravity????
please enlighten

AugustusMinimus

jakdelad wrote: »

we can get a level from gravity????
please enlighten

Gravity, quite literally has a centre of gravity.

If you tie a weight to a piece of string and hang it from a ceiling, the string will point directly down towards the earths centre of gravity.

Everything at 90 degrees to this line is level at that precise location on the earth. Walk even a step away and a different measurement would need to be taken to define "level".

jakdelad

AugustusMinimus wrote: »

Gravity, quite literally has a centre of gravity.

If you tie a weight to a piece of string and hang it from a ceiling, the string will point directly down towards the earths centre of gravity.

Everything at 90 degrees to this line is level at that precise location on the earth. Walk even a step away and a different measurement would need to be taken to define "level".

gravity pulls in all directions
your string theory is not precise

AugustusMinimus

jakdelad wrote: »

gravity pulls in all directions
your string theory is not precise

It is always 100% precise in find gravitational "level".

I'm not sure I know what your looking for. There is no such thing as "geographic levelness" (for want of a better term) as the earth is not spherical.

jakdelad

AugustusMinimus wrote: »

It is always 100% precise in find gravitational "level".

I'm not sure I know what your looking for. There is no such thing as "geographic levelness" (for want of a better term) as the earth is not spherical.

gravity bends so in essance you do not get a true level in the sense
you can also say a golf ball is not a true sphere too

AugustusMinimus

jakdelad wrote: »

gravity bends so in essance you do not get a true level in the sense
you can also say a golf ball is not a true sphere too

What do you mean "gravity bends".

Gravity is nothing but an attractive force between matter.

Every single point on earth has a gravition level which is a line which is at 90 degrees to a line pointing at the earths centre of gravity. Simple as that.

Obviously the position of the moon and other planets can slightly alter this but their effect is negligable in the extreme.

jakdelad

AugustusMinimus wrote: »

What do you mean "gravity bends".

Gravity is nothing but an attractive force between matter.

Every single point on earth has a gravition level which is a line which is at 90 degrees to a line pointing at the earths centre of gravity. Simple as that.

Obviously the position of the moon and other planets can slightly alter this but their effect is negligable in the extreme.

couldent have said it better myself

Cú Giobach

AugustusMinimus wrote: »

What do you mean "gravity bends".

Gravity is nothing but an attractive force between matter.

Every single point on earth has a gravition level which is a line which is at 90 degrees to a line pointing at the earths centre of gravity. Simple as that.

Obviously the position of the moon and other planets can slightly alter this but their effect is negligable in the extreme.

Gravity is much more than just "an attractive force between matter", it bends space, the Moon orbits the Earth because it is following the curved space caused by the Earths mass.

Imagine a roulette ball spiralling down a roulette wheel as it slows, because there is nothing to slow down the moon instead of spiralling down it just keeps revolving around the Earth (orbiting).

Mountains and the density of rocks have a measurable gravitational effect, check out this experiment by Nevil Maskelyne.



I've been thinking of the OP a bit today and was playing with the idea that to have something perfectly level you would need a perfect straight line, but because gravity curves space, the gravity of the Earth, Sun, Galaxy and our local Galactic cluster all bending space and even a possible large scale curvature of the universe, would all make a perfectly straight line impossible. You couldn't even use light, because that travels around the curves in space. Hmmmm............
Nice one OP gonna think about that going off to sleep tonight.

rccaulfield

Imperceptible differences in everyday life!

AugustusMinimus

Cú Giobach wrote: »

I've been thinking of the OP a bit today and was playing with the idea that to have something perfectly level you would need a perfect straight line, but because gravity curves space, the gravity of the Earth, Sun, Galaxy and our local Galactic cluster all bending space and even a possible large scale curvature of the universe, would all make a perfectly straight line impossible. You couldn't even use light, because that travels around the curves in space. Hmmmm............
Nice one OP gonna think about that going off to sleep tonight.

In respect to height, lenght and breath, the line would be straight. The line would be bent through the 4th dimension (time) which we simply can't perceive.

I've always been interested in gravity. Trying to reconcile general relativity (mass bending space etc) with Quantum Mechanics (exchange of gravitons creating gravity) is damn tricky. Hell, is just one of them correct or are both of them correct ?

Who knows if the graviton even exists.

Bruthal

Agonist wrote: »

Perpendicular to the force of gravity?

Thats what it is, perpendicular to a line through the earths centre of gravity to the surface at the point of measuring.

Bruthal

Cú Giobach wrote: »

I've been thinking of the OP a bit today and was playing with the idea that to have something perfectly level you would need a perfect straight line

Well in fact, if you had a 1000 mile long rail line for example, it would not in fact be level if it was perfectly straight as in a tangent to the earths curve, but level if it perfectly followed the earths curve. Which would mean it would be of equal distance from the earths centre of gravity along its length.

So any line to be level would in fact be curved in theory.

Cú Giobach

Cú Giobach wrote: »

I've been thinking of the OP a bit today and was playing with the idea that to have something perfectly level you would need a perfect straight line,

Where the **** did I pull that "gem" from??
Yesterday was one of my twice yearly bottle of bushmills malt (Birthday and christmas) Vague memory of posting things but not what I wrote, gonna have to check now if I had any arguments anywhere.

AugustusMinimus wrote: »

In respect to height, lenght and breath, the line would be straight. The line would be bent through the 4th dimension (time) which we simply can't perceive.

There's a photo of light (space) being bent by gravity.

I've always been interested in gravity. Trying to reconcile general relativity (mass bending space etc) with Quantum Mechanics (exchange of gravitons creating gravity) is damn tricky. Hell, is just one of them correct or are both of them correct ?
Who knows if the graviton even exists.

If you get the answer PM me, I promise I won't tell anyone.

My head hurts when I sit down or stand up, Dam you gravity leave me alone for a while...:mad:
.

peterako

Someone mixing G and g up...?

Cú Giobach

The more I think about this the less simple it seems.
The definition of "level" and the difference between "level with" and "level" seem to come into play here.


Imagine the above is a billiard ball sized neutron star.
Which of the lines a,b,and c fit the definition of "level".
Line "c" is not flat, every point is in a different plane, but at only one point on both "a" and "b" could you measure them perpendicular to the force of gravity.
"a" and "b" seem closer to the definition than "c" because every point is at least in the same plane, but are they?

Edit: Though I guess the word "level" is meaningless unless it is "level with" something.

AugustusMinimus

Cú Giobach wrote: »

The more I think about this the less simple it seems.
The definition of "level" and the difference between "level with" and "level" seem to come into play here.


Imagine the above is a billiard ball sized neutron star.
Which of the lines a,b,and c fit the definition of "level".
Line "c" is not flat, every point is in a different plane, but at only one point on both "a" and "b" could you measure them perpendicular to the force of gravity.
"a" and "b" seem closer to the definition than "c" because every point is at least in the same plane, but are they?

Edit: Though I guess the word "level" is meaningless unless it is "level with" something.

Well, a straight line is only ever level at one single point.

If you want to make a perfectly "flat" table top in terms of gravitation it should be slightly curved from the inside outwards.

jakdelad

robbie7730 wrote: »

Well in fact, if you had a 1000 mile long rail line for example, it would not in fact be level if it was perfectly straight as in a tangent to the earths curve, but level if it perfectly followed the earths curve. Which would mean it would be of equal distance from the earths centre of gravity along its length.

So any line to be level would in fact be curved in theory.

any line level would be curved??? interesting hypothesis.

The Hill Billy

There's a difference between a straight line & something being level. To me, an object would be level relative to another at a particular point, whether that be horizontal or vertical. The extension of a real or imaginary line beyond the specific point at which it is level is immaterial.

Maybe the question should be "is there any such thing as a straight line?"

Cú Giobach

AugustusMinimus wrote: »

Well, a straight line is only ever level at one single point.

If you want to make a perfectly "flat" table top in terms of gravitation it should be slightly curved from the inside outwards.

Therein lies the OP's conundrum, to define something as level surely you need 2 points, and something "flat" cannot be "curved".

Bruthal

Cú Giobach wrote: »

Therein lies the OP's conundrum, to define something as level surely you need 2 points, and something "flat" cannot be "curved".

Well putting up a press in the kitchen so its visually level is different from considering a 300 mile long table, which would have to be curved to be level at all points. If it was perfectly straight (a single plane) from end to end, and perfectly level at its centre, a ball put at one end would roll toward the middle. And that end would also not appear level to an observer, or a spirit level.

The above mentioned kitchen press could have a curve matching the earths curve in theory, but would appear perfectly straight to the eye even if it was curved. And would appear level even if perfectly straight because of its miniscule size, even if its 10 foot wide.

jakdelad

Hill Billy wrote: »

There's a difference between a straight line & something being level. To me, an object would be level relative to another at a particular point, whether that be horizontal or vertical. The extension of a real or imaginary line beyond the specific point at which it is level is immaterial.

Maybe the question should be "is there any such thing as a straight line?"

interesting response
how about y = mx + b

im invisible

an extremely EXTREMELY exaggerated depiction of the difference in gravity around the earth

take everything

Cú Giobach wrote: »

I've been thinking of the OP a bit today and was playing with the idea that to have something perfectly level you would need a perfect straight line, but because gravity curves space, the gravity of the Earth, Sun, Galaxy and our local Galactic cluster all bending space and even a possible large scale curvature of the universe, would all make a perfectly straight line impossible. You couldn't even use light, because that travels around the curves in space. Hmmmm............
Nice one OP gonna think about that going off to sleep tonight.

Doesn't gravity bend space-time, not space as such.
So isn't it still possicle to have a perfectly straight line (which albeit will be a curve in space time).

Chuck Stone

A laser beam perhaps?

AugustusMinimus

take everything wrote: »

Doesn't gravity bend space-time, not space as such.
So isn't it still possicle to have a perfectly straight line (which albeit will be a curve in space time).

Gravity doesn't bend space-time. Mass does.


This is the whole crux of the problem though.

General relativity leads us to believe that gravity is caused by matter warping space-time.

On the other hand, the best guesses at how gravity works at a microscopic level (quantum mechanics) is that it is due to various particles exchanging a theorised particle called the Graviton.

How two contrasting theories can be merged into one, I don't know.

AugustusMinimus

Chuck Stone wrote: »

A laser beam perhaps?

Gravity makes light bend.

In reality though, the light is still travelling in a straight line. However, it is space which is bending, not the laser beam.

Chuck Stone

AugustusMinimus wrote: »

Gravity makes light bend.

In reality though, the light is still travelling in a straight line. However, it is space which is bending, not the laser beam.

How about an imaginary line between two atoms?

Any good?

*Bit out of my depth tbh - note all the ???'s*;)

AugustusMinimus

Chuck Stone wrote: »

How about an imaginary line between two atoms?

Any good?

*Bit out of my depth tbh - note all the ???'s*;)

Again it depends.

Is it straight in respect of 3d space or in the case that space is bent, do you want it also to be able to go through 4 dimensions which would mean that the distance may be shorter.

It's like getting a sheet of paper. Drawing two dots on it and drawing a line between the two. However, if the paper is bent, a peice of string linking the two is shorter than the line drawn with the pencil. However, to achieve this, you have to go through the third dimension. With the pencil line, you can stick with your flat world two.

I guess in end, just like velocity, straightness is all relative. Straightness is a balance between the line or curve itself and how it exits in respect to how straight or bent space is.

slade_x

jakdelad wrote: »

hmmmm
but where would we get our levels from
what point do we calibrate from,, what marker

Dont know how i didnt see this thread before

There is no absolute level. we do not define the aspect of the universe as being level, nor any feature or body of it. Level for us can be described in geometry. when making a table or constructing a building the scale of the earth makes it so "level" can be a little bit arbitrary as it can be described as a horizontal plane with a parallel to another, of which length can vary.
We do not build shelves, tables or buildings over hundreds of miles. Our roads in entirety are not level, an entire road spanning miles will vary in degree as the earths surface curves. since a level can be described as without varying in degree with respect to its plane, or alternatively no part of its surface can be higher or lower than another.
However level does not have to be that precise as building foundations or even a table top can vary in degree by even something like a hundredth thousand of a degree. defining it with that level of precision is not practical especially for most construction, so i believe the term level has more significance to subjects as scale construction or carpentry than a means to describe the structures of the universe and its matter. Its important for your home to be level so that the total structure can support the weight of floors or roofing evenly on its constituent parts and foundation. The golden gate bridge is most certaintly not level. if we cant describe nor need to describe a bridge as level whats the point of extending the term for other large scale purposes. To quote Einstein "it's all relative"

Agonist wrote: »

Perpendicular to the force of gravity?

Gravity attracts all matter in all directions. Relative to our planets gravity with respect to objects on it gravity acts perpendicular to horizontal ground (gravity doesnt pull us around the earths circumference). On an incline (hill) a car would roll down a hill (with little friction; handbrake disengaged etc). In both instances level or not the car is under the same affect of gravity. There is no real solid reference to a horizontal plane in that question. the only indicator of a differentiator being the car was pulled down the hill from lack of one. the car had higher potential with which could be pulled down from.

One could say our planet is spherical because the crust was attracted perpendicular to the force of gravity relative to its centre of mass when forming. And as most people will agree the world is not flat but spherical. Even the world isnt level :rolleyes: