Can anyone explain Gravity to a biologist?

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Gravity has to be the most screwed up force in the universe and the most enigmatic. It pulls on a boulder and a feather to produce the same acceleration. How screwed up is that? It is even more improbable as a moon always showing the same face to the planet it orbits. There is an infinate (or very large finite) number of other states, but moons do and for a relatively understandable reason).

The notion of it is so weird. A large planet sized object without any intermediary particle somehow "knows" I am there and pulls on me at g no matter what my mass is (non relativistic).

Gravity just doesn't make any sense. I remember being outraged at both relativity and that the vacuum of space that transmits electromagnetic radiation even though there was nothing to vibrate. It is a strange counterintuitive universe. I am much better now ;)

Nobody has come up with any theory of gravity that my limited understanding can swallow. Somebody said that gravity is a consequence of mass moving through time. Seems to me that this is as well saying gravity is a result of hedgehogs dancing the rumba.
 
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  • #2
Dale
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Maybe you should bother to learn the theory and its experimental support first. Not fitting nicely into your admittedly ignorant preconceptions is hardly an objection to a scientific theory.
 
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Maybe you should bother to learn the theory and its experimental support first. Not fitting nicely into your admittedly ignorant preconceptions is hardly an objection to a scientific theory.

Blah Blah .... I have enough work to do already. Do you think I am trying to "expose" science as a fraud? Not my intention. I was just curious as I have always been fascinated with gravity but haven't ever been able to come up with anything even remotely compelling even during my intermittant Internet searches on the subject. I was wondering if anyone has yet ..... Isn't that what these forums are for? But perhaps it is indeed impossible to explain without heaps of math. In my field I know personally that I can explain the current state without jargon in a form just about anyone can understand, but others heap on the BS so that nobody can understand it. A mathematician friend of mine is an absolute closed book, mere mortals could never understand what he does.

My ignorant perceptions are obviously ignorant ..... that was the point. I was hoping to have some stimulating enlightenment. Wrong forum I guess .....
 
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  • #4
Pengwuino
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Maybe you should bother to learn the theory and its experimental support first. Not fitting nicely into your admittedly ignorant preconceptions is hardly an objection to a scientific theory.

I think the OP has a very valid point and is simply saying that they don't understand it because of their limited knowledge of the subject.

@OP: Gravity shouldn't make much sense for the very reasons you state. However, it is simply how the world works.

The tidal-locking of the moon actually should make way more sense if you understand how gravity works. The problem is that you have to get away from what comes natural to you. If you apply 10N of force to a 1kg object, you expect a 10m/s^2 acceleration. If you applied the same force to a 100kg object, you'd get a much lower acceleration. So your intuition says that forces work that way. Then you look at gravity, the most common force in our everyday life. If you thought of large masses (planets and moons) in the way your intuition tells you, everything would start to break down. Planets wouldn't orbit correctly if at all, you would get massive problems with something called 'equivalence', etc. So what your intuition tells you must be right is actually wrong because the underlying assumption of how forces work doesn't exactly tell you how gravity works.

Think about it. The Earth must exert a MASSIVE force on the Moon to keep it in orbit. If that same force was exerted on you, you'd be crushed to death in a spectacular manner.

Personally, general relativitys analogy of "spacetime fabric" makes gravity seem the most intuitive to me. The geometry of space changes (e.g. the "fabric") and gravity is just something falling down into that geometry. Then it kinda makes sense everything should fall in the same way. Of course, this is a pretty bad butchering of the actual analogy, and the analogy itself is flawed.... but it helps me understand it a bit better.
 
  • #5
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BREAKING SYMMETRY
-- James Ph. Kotsybar

Our universe has things in it because
chance quantum fluctuations enable.
Nothing is what violates Nature’s laws --
something is apparently more stable.
Super-symmetry was asking for it.
It was just too perfect to be withstood,
and once it took the predictable hit
it lit up the entire neighborhood,
and in that Big Bang, the forces all split.
Gravity, of course, was most serious
and left, having little to do with it,
and, to this day, remains mysterious.
Though we still work to unify them all,
Entropy says it’s too late for that call.
 
  • #6
Dale
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Do you think I am trying to "expose" science as a fraud? Not my intention. I was just curious as I have always been fascinated with gravity but haven't ever been able to come up with anything even remotely compelling even during my intermittant Internet searches on the subject. ... I was hoping to have some stimulating enlightenment.
You'll forgive me if comments like these seem more like an anti-relativity crackpot than an honest student looking to learn:

Gravity just doesn't make any sense. I remember being outraged at both relativity and that the vacuum of space that transmits electromagnetic radiation even though there was nothing to vibrate. It is a strange counterintuitive universe. I am much better now ;)

Nobody has come up with any theory of gravity that my limited understanding can swallow. Somebody said that gravity is a consequence of mass moving through time. Seems to me that this is as well saying gravity is a result of hedgehogs dancing the rumba.

If you want to learn, then ask a question. Don't speak of your outrage and compare current theories to hedgehogs dancing the rumba. I may be hypersensitive due to the large number of crackpots I have dealt with, but you should be aware that your OP sounds cranky rather than inquisitive.
 
  • #7
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I think the OP has a very valid point and is simply saying that they don't understand it because of their limited knowledge of the subject.

@OP: Gravity shouldn't make much sense for the very reasons you state. However, it is simply how the world works.

The tidal-locking of the moon actually should make way more sense if you understand how gravity works. The problem is that you have to get away from what comes natural to you. If you apply 10N of force to a 1kg object, you expect a 10m/s^2 acceleration. If you applied the same force to a 100kg object, you'd get a much lower acceleration. So your intuition says that forces work that way. Then you look at gravity, the most common force in our everyday life. If you thought of large masses (planets and moons) in the way your intuition tells you, everything would start to break down. Planets wouldn't orbit correctly if at all, you would get massive problems with something called 'equivalence', etc. So what your intuition tells you must be right is actually wrong because the underlying assumption of how forces work doesn't exactly tell you how gravity works.

Think about it. The Earth must exert a MASSIVE force on the Moon to keep it in orbit. If that same force was exerted on you, you'd be crushed to death in a spectacular manner.

Personally, general relativitys analogy of "spacetime fabric" makes gravity seem the most intuitive to me. The geometry of space changes (e.g. the "fabric") and gravity is just something falling down into that geometry. Then it kinda makes sense everything should fall in the same way. Of course, this is a pretty bad butchering of the actual analogy, and the analogy itself is flawed.... but it helps me understand it a bit better.


Thanks for the reply. It is so true that intuitive expectations have little to explain about gravity. I have thought about the warping space time analogy, but it seems to me there is no "down" except down in potential energy in the warping of space and the warping is in some manner we are completely ill equiped to even visualize. The best one I have heard is that gravity is the result of mass moving through time, but that doesn't seem to be testable.

My puzzlement has always been how gravity works the way it does, not whether it does or not since that is pretty much a given. Any action a distance is puzzling to me, but with electromagentic and static you can at least manipulate it and thereby get some understanding and comfort.

Electrons do strange things when they move in spiral trajectory ....... has anyone ever tried to make protons move in such a trajectory?
 
  • #8
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This probably won't satisfy you, but everything (at a normal scale) can be explained by:

[tex]g=\frac{GM}{r^2}[/tex]

The mass of the object being accelerated is irrelevant when calculating the acceleration.

You can think of it this way: F=ma. The force of gravity is Fg=GMm/r2. If we were to solve F=ma for the acceleration, we would simply divide both sides by m. Likewise, to calculate the acceleration due to gravity, we would also divide both sides by m. The m's cancel, meaning they do not affect the acceleration.
 
  • #9
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You'll forgive me if comments like these seem more like an anti-relativity crackpot than an honest student looking to learn:



If you want to learn, then ask a question. Don't speak of your outrage and compare current theories to hedgehogs dancing the rumba. I may be hypersensitive due to the large number of crackpots I have dealt with, but you should be aware that your OP sounds cranky rather than inquisitive.

Perhaps the Hedgehog thing was a bit much ;) It is my way of saying that I can't think of any way to test that theory because I can't think of any way to manipulate the relevant variables because they are all inter-related.


Your prodding has forced me to rephase my question:

Can anyone explain how gravity actually acts at a distance as it does without heaps of math and include some real experimental data. Since it seems to me that nobody can manipulate gravity or time in an independant manner, the answer may be no.

If so this doesn't prove or disprove anything, it just means we don't know. Similar to the meaningless stupid analogies about evolution and bumble bees flying that some people make.
 
  • #10
Andy Resnick
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[snip]

Gravity just doesn't make any sense. I remember being outraged at both relativity and that the vacuum of space that transmits electromagnetic radiation even though there was nothing to vibrate. It is a strange counterintuitive universe. I am much better now ;)

Nobody has come up with any theory of gravity that my limited understanding can swallow. Somebody said that gravity is a consequence of mass moving through time. Seems to me that this is as well saying gravity is a result of hedgehogs dancing the rumba.

Blah Blah .... I have enough work to do already.

[snip]

My ignorant perceptions are obviously ignorant ..... that was the point. I was hoping to have some stimulating enlightenment. Wrong forum I guess .....

[snip]
Similar to the meaningless stupid analogies about evolution and bumble bees flying that some people make.

May I make the suggestion that a less confrontational attitude would most likely lead to substantive (or even stimulating) discussions?
 
  • #11
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Can anyone explain how gravity actually acts at a distance as it does without heaps of math

No. That is how physics is written - in the language of math. If you can't read it, you should learn the language.

and include some real experimental data. Since it seems to me that nobody can manipulate gravity or time in an independant manner, the answer may be no.

If you want experiments, merely google "experimental proof of general relativity."
 
  • #12
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This probably won't satisfy you, but everything (at a normal scale) can be explained by:

[tex]g=\frac{GM}{r^2}[/tex]

The mass of the object being accelerated is irrelevant when calculating the acceleration.

You can think of it this way: F=ma. The force of gravity is Fg=GMm/r2. If we were to solve F=ma for the acceleration, we would simply divide both sides by m. Likewise, to calculate the acceleration due to gravity, we would also divide both sides by m. The m's cancel, meaning they do not affect the acceleration.


I vividly remember my high school physics teacher working this one out on the board. An equation is our perception of reality and the above one is exceptionally good but says nothing about how it works.

A very rough analogy from biology would be inheritance of a trait like blue eyes in man. You can study the stats and even closely predict outcomes (more or less) but that tells you litltle about what is actually happening. It wasn't until the importance of DNA was identified that the how questions started getting answered.

I have a feeling gravity is a much much harder nut to crack than DNA
 
  • #13
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May I make the suggestion that a less confrontational attitude would most likely lead to substantive (or even stimulating) discussions?

You have never heard them?

"Sceince must be wrong because it can't understand how Bumble bees fly"

"even if you shake watch parts for a billion years, you will never get a working watch"

I was trying to empathise with person who took exception to my original comment by pointing out comments that have some similarity and saying it wasn't my intention for the comment to be interpreted like that.

Really I was wondering if anyone has found the DNA of gravity or even inklings of the DNA of gravity.
 
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  • #14
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I vividly remember my high school physics teacher working this one out on the board. An equation is our perception of reality and the above one is exceptionally good but says nothing about how it works.

A very rough analogy from biology would be inheritance of a trait like blue eyes in man. You can study the stats and even closely predict outcomes (more or less) but that tells you litltle about what is actually happening. It wasn't until the importance of DNA was identified that the how questions started getting answered.

I have a feeling gravity is a much much harder nut to crack than DNA

I have a video for you to watch:

 
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  • #15
Pengwuino
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Thanks for the reply. It is so true that intuitive expectations have little to explain about gravity. I have thought about the warping space time analogy, but it seems to me there is no "down" except down in potential energy in the warping of space and the warping is in some manner we are completely ill equiped to even visualize. The best one I have heard is that gravity is the result of mass moving through time, but that doesn't seem to be testable.

My puzzlement has always been how gravity works the way it does, not whether it does or not since that is pretty much a given. Any action a distance is puzzling to me, but with electromagentic and static you can at least manipulate it and thereby get some understanding and comfort.

Electrons do strange things when they move in spiral trajectory ....... has anyone ever tried to make protons move in such a trajectory?

Gravity isn't the result of mass moving through time. Or well... in the vaguest sense it is kinda maybe, but not really.

Action at a distance is the concern apparently. Electromagnetism is not an action at a distance, it is actually something mediated by a quantized object: photons. The strong nuclear force, if you've heard of it, is against theorized to be mediated by a quantized object: gluons. To my knowledge we've never observed a free gluon though, but the formalism is widely accepted. Gravity was thought to be something else that you could simply describe using a quantized object: a graviton. However, mathematically trying to have a particle that would do the job of gravity has so many problems that most people have given up on the idea that there is a particle that mediates gravity.

And yes, protons can move in spiral trajectories exactly like protons can but what's the point? What's so strange about it? It's actually extremely easy to do.
 
  • #16
Pengwuino
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I have a video for you to watch:


Be careful. The OP isn't asking "why?". They're asking "how?". We have a fairly good idea how gravity works. "Why" is a completely different story.
 
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  • #17
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Be careful. The OP isn't asking "why?". They're asking "how?". We have a fairly good idea how gravity works. "Why" is a completely different story.

No, but he's asking us to explain gravity in in terms he can understand. That's a hard thing to do, and he should understand that.
 
  • #18
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I have a video for you to watch:


Surely you are joking Mr Feynman ........ I loved that book. He provides a very honest answer that I respect and understand more or less, but he eludes to deeper understandings with regard to even Aunt Edna's fall, much like DNA provides a much much deeper understanding to how we work, but not why alas.
 
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  • #19
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Hi Sirandar. I too share your interest in gravity. I am just a layman in this field but I think I have come to a good understanding of how gravity works. Not "why" of course, no one knows that. You do not need to be good at math to understand it in Newtonian form. The breakthrough came for me when I understood 1) Newton's universal law of gravitation, 2) frame of reference, and 3) the difference between the concepts of "inertial mass", "active gravitational mass", and "passive gravitational mass". (in that order)

This forum seems to work best when you have a specific question. Sometimes things progress from a simple question into an interesting thread.

Welcome to PF.
 
  • #20
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No, but he's asking us to explain gravity in in terms he can understand. That's a hard thing to do, and he should understand that.

I fully understand how difficult it is and I was hoping for an answer not expecting one. For me this is a quick and somewhat lazy way of getting insight into a question I have previously fantacised about addressing, but quickly realized that it about as likely as being a superhero. I can and sometimes do answer questions related to my field but gravity .... that's a whole new type of problem.

In a sense I am not asking why Gravity works because like Mr Feynman says, that is unlikely to yield anything.


So for my 3rd and final iteration i will ask ....... Has there been any deeper understandings in how gravity acts at a distance that at least is partially akin to the limited way how DNA explains how living things work?

PS. I have a second year university physics background so I am not completely ignorant of math and physics, and I have no aspirations of answering this question myself ( well maybe a little ;))
 
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  • #21
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To me the key to understanding how gravity works will involve figuring out how inertia works, because inertia is what distinguishes matter from radiant energy. Gravitation seems to be a function of mass, but not as immediately as inertia is, and inertia seems to be responsible for conflicts between objects in motion that result in force-exertion among them. Presumably this is impossible with EM radiation since it always travels at the same speed within any medium, whereas matter can travel at different speeds in the same medium. This is due to inertia, i.e. the ability to move slower than the speed of light. Could inertia be related to gravitation, for example in the way that cellular DNA is related to characteristics of the organism as a whole?
 
  • #22
Pengwuino
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So for my 3rd and final iteration i will ask ....... Has there been any deeper understandings in how gravity acts at a distance that at least is partially akin to the limited way how DNA explains how living things work?

PS. I have a second year university physics background so I am not completely ignorant of math and physics, and I have no aspirations of answering this question myself ( well maybe a little ;))

General Relativity is our best theory at the moment.
 
  • #23
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To me the key to understanding how gravity works will involve figuring out how inertia works, because inertia is what distinguishes matter from radiant energy. Gravitation seems to be a function of mass, but not as immediately as inertia is, and inertia seems to be responsible for conflicts between objects in motion that result in force-exertion among them. Presumably this is impossible with EM radiation since it always travels at the same speed within any medium, whereas matter can travel at different speeds in the same medium. This is due to inertia, i.e. the ability to move slower than the speed of light. Could inertia be related to gravitation, for example in the way that cellular DNA is related to characteristics of the organism as a whole?


Inertia as the ability to move slower than the speed of light ... I have never looked at it that way before. But it seems to me we could could subsitiute mass for inertia in your statement and the meaning wouldn't change. In relativity is mass and inertia different or are they the same thing? Seems to me mass and inertia are always coupled, but I may be wrong.
 
  • #24
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Sirandar said:
In relativity is mass and inertia different or are they the same thing? Seems to me mass and inertia are always coupled, but I may be wrong.
Inertial mass and gravitational mass are proportionally equivalent. That's the equivalence principle.

edit:
Just wanted to add that there is no known reason why inertial mass and gravitational mass must be equivalent. They just are - according to the most sensitive measurements to date. Just another one of those things that makes gravity so interesting.
 
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  • #25
Andy Resnick
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This probably won't satisfy you, but everything (at a normal scale) can be explained by:

<perfectly good conceptual model for gravity>

An equation is our perception of reality and the above one is exceptionally good but says nothing about how it works.

A very rough analogy from biology would be inheritance of a trait like blue eyes in man. You can study the stats and even closely predict outcomes (more or less) but that tells you litltle about what is actually happening. It wasn't until the importance of DNA was identified that the how questions started getting answered.

Ok, now we are getting somewhere. Yes, theories are a conceptual model, just like the statistical models for inheritance.

Going further with biology, the discovery of the function of DNA in terms of genes "solved" the problem of inheritance.

I'm not an expert, but in many ways, GR 'solved' the problem of gravity. There's a lot of people here who can help you understand GR better. It provides a fairly simple conceptual model that predicts and explains measured data.

Just as 'it wasn't until [Newtonian mechanics was developed] that the how questions started getting answered', when GR was developed, *additional* how questions started getting answered. GR also makes some very simple predictions that are extremely difficult to test (and GR is still being tested).

Back to biology- the discovery of DNA explained a lot, but there is still a lot unknown about genes. It's an incomplete model- so in addition to the genome, we have the proteome, metabolome, fillintheblank-ome, because the more accurately we want to model things like the development of an organism, the more factors we have to take into account. We have a quantitative idea of a gene, but not what each one does (the proteome project). Also, we do not understand related things like upstream regulators for expression, post-translational modification and the spliceosome (one gene != 1 protein), modifier genes, etc.

So to be fair, there's still a lot of research regarding genetics.

Does this help?
 

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