4 ms·

Not a physicist, but how do you get something to bend without a force exerted upon it?

by cronix 3y ago

habibur 3y ago
They attribute it to the fact that space around the object is bent. Which is causing the other object to drop, accelerate or bent. Check General Relativity's explanation of Gravity. That might not answer all of your or my question. But maybe we didn't give enough time to ponder on that line.
scotty79 3y ago
The cool thing about gravity is that it doesn't bend anything it just alters space so that straight things are bent.
- _8j50 3y ago
  So without it planets are like cubes? Can't even imagine how deformed people would be
a_wild_dandan 3y ago
It's just unfortunate nomenclature. Space(time) is a set of dimensions. It's not a substance, like a ruler, anymore than temperature is a substance in a thermometer. The word "bend" misleads us by equivocating "bending" a ruler (forcefully rearranging its atoms into a new shape) with "bending" spacetime (e.g. changing how fast someone's clock ticks).
LegitShady 3y ago
the simplest way to describe it is that an object in freefall moves in geodesic in spacetime, which is a is not straight line in 3dimensional classical physics but produces gravitational motion. https://en.wikipedia.org/wiki/Geodesics_in_general_relativity https://en.wikipedia.org/wiki/Geodesics_in_general_relativit... The basic idea is that depending on your frame of reference, you might experience what is called a fictitious or psuedo force that disappears in a more simple frame of reference. Examples of these include centrifugal force, the Coriolis effect. https://en.wikipedia.org/wiki/Fictitious_force https://en.wikipedia.org/wiki/Fictitious_force Einstein's great revelation in the theory of general relativity was that there was no difference between gravity and free fall - which is called the equivalence principle. https://en.wikipedia.org/wiki/Equivalence_principle https://en.wikipedia.org/wiki/Equivalence_principle In special relativity, einstein's theory had a preference for inertial frame observers where the observer essentially became the origin of coordinate system to map space by, but in general relativity einstein does away with inertial frames as privileged, and an observer is literally decided by what light it can see, and their coordinate system cannot be universal because of curved space. https://en.wikipedia.org/wiki/Inertial_frame_of_reference#Special_relativity https://en.wikipedia.org/wiki/Inertial_frame_of_reference#Sp... https://en.wikipedia.org/wiki/Observer_%28special_relativity%29 https://en.wikipedia.org/wiki/Observer_%28special_relativity...
antonvs 3y ago
General relativity doesn't really say forces don't exist, it just says that they're a secondary, and relative, effect caused by a more fundamental phenomenon, i.e. the curvature of spacetime due to the presence of mass/energy. Just as centrifugal force is a relative effect that you only observe in a rotating (i.e. accelerated) reference frame, the force of gravity is also a relative effect that you only observe in an accelerated reference frame. Standing on Earth, we're accelerating towards the center at 9.8 m/s^2, and we feel that as weight due to a force of gravity that we experience in our reference frame. If you jump out of a plane, though, you feel weightless (especially if you can arrange to do so in a vacuum), because you're in "free fall" - you're following the curvature of spacetime. In your reference frame, you're not experiencing the force of gravity. This demonstrates that gravity, like centrifugal force, is a "fictitious" force - which doesn't really mean that it's not real, but rather that it's a secondary effect that depends on your reference frame.

Not a physicist, but how do you get something to bend without a force exerted upon it?

by cronix 3y ago

Not a physicist, but how do you get something to bend without a force exerted upon it?

They attribute it to the fact that space around the object is bent. Which is causing the other object to drop, accelerate or bent. Check General Relativity's explanation of Gravity. That might not answer all of your or my question. But maybe we didn't give enough time to ponder on that line.

scotty79 3y ago

The cool thing about gravity is that it doesn't bend anything it just alters space so that straight things are bent.

_8j50 3y ago
So without it planets are like cubes? Can't even imagine how deformed people would be

a_wild_dandan 3y ago

It's just unfortunate nomenclature. Space(time) is a set of dimensions. It's not a substance, like a ruler, anymore than temperature is a substance in a thermometer. The word "bend" misleads us by equivocating "bending" a ruler (forcefully rearranging its atoms into a new shape) with "bending" spacetime (e.g. changing how fast someone's clock ticks).

LegitShady 3y ago

the simplest way to describe it is that an object in freefall moves in geodesic in spacetime, which is a is not straight line in 3dimensional classical physics but produces gravitational motion. https://en.wikipedia.org/wiki/Geodesics_in_general_relativity https://en.wikipedia.org/wiki/Geodesics_in_general_relativit... The basic idea is that depending on your frame of reference, you might experience what is called a fictitious or psuedo force that disappears in a more simple frame of reference. Examples of these include centrifugal force, the Coriolis effect. https://en.wikipedia.org/wiki/Fictitious_force https://en.wikipedia.org/wiki/Fictitious_force Einstein's great revelation in the theory of general relativity was that there was no difference between gravity and free fall - which is called the equivalence principle. https://en.wikipedia.org/wiki/Equivalence_principle https://en.wikipedia.org/wiki/Equivalence_principle In special relativity, einstein's theory had a preference for inertial frame observers where the observer essentially became the origin of coordinate system to map space by, but in general relativity einstein does away with inertial frames as privileged, and an observer is literally decided by what light it can see, and their coordinate system cannot be universal because of curved space. https://en.wikipedia.org/wiki/Inertial_frame_of_reference#Special_relativity https://en.wikipedia.org/wiki/Inertial_frame_of_reference#Sp... https://en.wikipedia.org/wiki/Observer_%28special_relativity%29 https://en.wikipedia.org/wiki/Observer_%28special_relativity...

antonvs 3y ago

General relativity doesn't really say forces don't exist, it just says that they're a secondary, and relative, effect caused by a more fundamental phenomenon, i.e. the curvature of spacetime due to the presence of mass/energy. Just as centrifugal force is a relative effect that you only observe in a rotating (i.e. accelerated) reference frame, the force of gravity is also a relative effect that you only observe in an accelerated reference frame. Standing on Earth, we're accelerating towards the center at 9.8 m/s^2, and we feel that as weight due to a force of gravity that we experience in our reference frame. If you jump out of a plane, though, you feel weightless (especially if you can arrange to do so in a vacuum), because you're in "free fall" - you're following the curvature of spacetime. In your reference frame, you're not experiencing the force of gravity. This demonstrates that gravity, like centrifugal force, is a "fictitious" force - which doesn't really mean that it's not real, but rather that it's a secondary effect that depends on your reference frame.