Gravity, I still don't get it
Discussion
Frimley111R said:
I've watched a lot of stuff about it but it seems to me that particles of matter are attracted to each other and there's nothing more to it than that and yet scientists seems to say there's no such thing as gravity. If so why are we all attracted to the ground?
Gravity is just another name for the force of attraction that exists between all particles. We tend to use gravity as name for the force of attraction between two bodies when one is a planet or similarly-sized object, but even two tennis balls on a table (for example) will have a minute level of attraction towards each other. You won't see them move though, as other forces (such as friction) are magnitudes more powerful and prevent it moving.This is a good question, really is.
I’ve seen explanations they say what gravity is really doing is bending space time in such a way that objects are directed to each other. The larger the object, the more it bends spacetime.
This makes sense to me bar one thing….
The effect is usually illustrated by an analogy of a bowling ball on a rubber sheet distorting it and causing a smaller ball to roll towards it rather than past it. I totally get the effect of the rubber sheet being analogous to distorted space time, but I then don’t get what force is acting to cause the ball to slide down the sheet. In the analogy, that’s confusingly just gravity (since the demo takes place on earth vs in space), but what’s that gravity supposed to be an analogy of? Would welcome an answer to this!
One thing I do get about gravity is that it is a very weak force. Even a 1g fridge magnet can hold itself off the ground, which means that it has enough magnetic force to beat the gravitational force of the entire planet earth weighing 6,000,000,000,000,000,000,000,000,000 times more. That’s a rather weak force.
I’ve seen explanations they say what gravity is really doing is bending space time in such a way that objects are directed to each other. The larger the object, the more it bends spacetime.
This makes sense to me bar one thing….
The effect is usually illustrated by an analogy of a bowling ball on a rubber sheet distorting it and causing a smaller ball to roll towards it rather than past it. I totally get the effect of the rubber sheet being analogous to distorted space time, but I then don’t get what force is acting to cause the ball to slide down the sheet. In the analogy, that’s confusingly just gravity (since the demo takes place on earth vs in space), but what’s that gravity supposed to be an analogy of? Would welcome an answer to this!
One thing I do get about gravity is that it is a very weak force. Even a 1g fridge magnet can hold itself off the ground, which means that it has enough magnetic force to beat the gravitational force of the entire planet earth weighing 6,000,000,000,000,000,000,000,000,000 times more. That’s a rather weak force.
Any particle of matter exerts an attraction to any other particle with matter.
However, the modern view is not so much that they attract each other but that particles bend and distort space-time in proportion to their mass. Other particles will be affected by the warped space-time in proportion to their distance from each other and their respective masses.
However, the modern view is not so much that they attract each other but that particles bend and distort space-time in proportion to their mass. Other particles will be affected by the warped space-time in proportion to their distance from each other and their respective masses.
boyse7en said:
Gravity is just another name for the force of attraction that exists between all particles. We tend to use gravity as name for the force of attraction between two bodies when one is a planet or similarly-sized object, but even two tennis balls on a table (for example) will have a minute level of attraction towards each other. You won't see them move though, as other forces (such as friction) are magnitudes more powerful and prevent it moving.
Or in Trump's case that attraction is called unwanted sexual abuse. Mars said:
The part I am currently bending my head around is the speed of gravity. Something like, if the sun suddenly winked out of existence, the earth would continue to orbit the sun's previous location for 8 mins (speed of light) before whizzing off tangentially.
What's the explanation for that?Frimley111R said:
Mars said:
The part I am currently bending my head around is the speed of gravity. Something like, if the sun suddenly winked out of existence, the earth would continue to orbit the sun's previous location for 8 mins (speed of light) before whizzing off tangentially.
What's the explanation for that?It's a bit like light in that regard.
Otherwise you would be able to send signals faster than light by moving masses.
See also;
https://en.m.wikipedia.org/wiki/First_observation_...
See also;
https://en.m.wikipedia.org/wiki/First_observation_...
Fusion777 said:
Gravity needs messenger particles, and they can’t travel faster than light (nothing can).
Depends on whether you're talking about general speed of light or C. Cherenkov results from FTL through water, but it's obviously still much slower than C. Standing next to a spent fuel pool with lights off feels properly science fiction
And something something Tachyons... Possibly.
TGCOTF-dewey said:
boyse7en said:
Gravity is just another name for the force of attraction that exists between all particles. We tend to use gravity as name for the force of attraction between two bodies when one is a planet or similarly-sized object, but even two tennis balls on a table (for example) will have a minute level of attraction towards each other. You won't see them move though, as other forces (such as friction) are magnitudes more powerful and prevent it moving.
Or in Trump's case that attraction is called unwanted sexual abuse. As for gravity, it gets me down.
67Dino said:
The effect is usually illustrated by an analogy of a bowling ball on a rubber sheet distorting it and causing a smaller ball to roll towards it rather than past it. I totally get the effect of the rubber sheet being analogous to distorted space time, but I then don’t get what force is acting to cause the ball to slide down the sheet. In the analogy, that’s confusingly just gravity (since the demo takes place on earth vs in space), but what’s that gravity supposed to be an analogy of? Would welcome an answer to this!
I really hope somebody can answer this in simple terms, I read articles and watched numerous videos about it and still can't fully grasp it.I believe it is to do with the missing 'time' aspect of the model.
It's easy to understand that moving particles could have their path of travel through space bent if the underlying geometry of space is altered by gravity. For example if we draw a bunch of lines representing moving particles on a piece of paper and then pinch the paper in the middle (representing a massive object), the lines will bend in towards the pinch.
But why then would two stationary objects attract each other?
My understanding is (but this may be entirely wrong, please correct it somebody!) :
- objects always follow geodesics (shortest path possible)
- even an object which is stationary in space is moving at the speed of light through time.
Therefore since time is also distorted just as space is, the shortest path for that object through time may result in it moving through space.
May be misremembering but Brian Cox showed two objects falling at the same rate in the vacuum demo - and am sure he said that shows the objects are falling at the same rate (in the absence of air friction) down the side of the gravity well / curved spacetime caused by the earths mass. Am sure he also said something about order naturally drifting toward dis-order over time (e.g. buildings decay, people age, etc), increased entropy and all that, and perhaps that objects as they slide into the gravity well are drawn toward slower time, or decreased rate of entropy.
Something like that, or I dreamt it.
Something like that, or I dreamt it.
Frimley111R said:
I've watched a lot of stuff about it but it seems to me that particles of matter are attracted to each other and there's nothing more to it than that
There is more to it than that. There are other forces that attract and repel, at different scales.Broadly, nuclear forces are available in "strong" and "weak" varieties, and then there's magnetism.
Frimley111R said:
and yet scientists seems to say there's no such thing as gravity.
Which scientists? I must have missed this and many other headlines. Gravity exists, has been measured and is reliably present where mass is.Frimley111R said:
If so why are we all attracted to the ground?
Because at our scale the mass of the Earth under us attracts us and we to it via gravitational attraction.Odd thread.
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