6 ms·

Is Gravity Real? A Scientist Takes On Newton

59 points by donohoe 16y ago

workingsmart 16y ago
I would like to respectfully say that this article is only superficially appealing and therefore not proper for HN. This is just a hypothesis without mathematical basis. All you really need to read is the last few paragraphs to see that there isn't any mathematical rigor to it. This is a whole article about speculation about gravity, and it wastes a lot of time trying to hype up a physicist that won't flush out his math.
- vecter 16y ago
  I haven't had a chance to go through the paper yet (http://arxiv.org/abs/1001.0785 http://arxiv.org/abs/1001.0785), but it seems that he does make some derivations and proof sketches. Can someone verify this?
  - rubidium 16y ago
    I got through page 11 before loosing the plot, and it seems to be a very light mathematical treatment of the subject. More of a "what if we thought about it this way?" then a "here's the proof" type paper.
    - Qz 16y ago
      Relativity started with "what if we thought about it this way?". Just saying.
      - robryan 16y ago
        Yeah part of the process, because of this new paper someone might get an idea they wouldn't have had to expand upon it. You see articles stating that something broke the laws of physics when really it just didn't fit our current model of understanding.
        pyre 16y ago
        > You see articles stating that something broke the > laws of physics when really it just didn't fit our > current model of understanding. It 'broke the law' in so much as it proved that the law was a 'broken' law (aka incomplete). It wasn't an action that violated a law, but a law that was rendered 'broken' by an action.
      - rubidium 16y ago
        Yes, exactly. That's why it's worth talking about in the first place. I wasn't downplaying the paper, just observing what I could about the current strength of its claims. It's more of a Gedankenexperiment with some guiding equations, which it seems the author stated as his intent in the nytimes article.
  - varjag 16y ago
    I'm not a physics major, but it appears superficial, non conclusive and light on math. At this point it's not a theory, but an (interesting as it may be) speculation.
    - bertm 16y ago
      This paper built upon work that Stephen Hawking did. "The hypothesis of gravity being an entropic force has a history that goes back to research on black hole thermodynamics by Bekenstein and Hawking in the mid-1970s. These studies suggest a deep connection between gravity and thermodynamics." http://en.wikipedia.org/wiki/Gravity_as_an_entropic_force http://en.wikipedia.org/wiki/Gravity_as_an_entropic_force someone might be able to find a better source.
- rjprins 16y ago
  Since when does HN need mathematical rigor for hypotheses? I have never seen this standard applied to blog posts about how to be a leader, pitching your ideas, how to program, etc. All of which usually don't come with the statistical proof with which they should come if they want to make a scientific claim... It's all just insights and thoughts.
- dasil003 16y ago
  In order for anyone to take your opinion about what is proper for HN seriously you need to post it from an account that actually has an investment in HN.
michael_nielsen 16y ago
I haven't read the Verlinde paper, but wanted to mention one of the papers it apparently builds on. That's Ted Jacobson's remarkable paper showing that gravity is a consequence of (1) thermodynamics and (2) the black hole entropy law. The paper is http://arxiv.org/abs/gr-qc/9504004 http://arxiv.org/abs/gr-qc/9504004 Sabine Hossenfelder has some useful comments on Verlinde's work here: http://backreaction.blogspot.com/2010/03/gravity-is-entropy-is-gravity-is.html http://backreaction.blogspot.com/2010/03/gravity-is-entropy-...
- yannis 16y ago
  You can also get more links from Verlinde himself http://twitter.com/erikverlinde http://twitter.com/erikverlinde but as he twitts Tomorrow I have to teach. Third year students. They also want to hear about emergent gravity. It is going to be tough to explain it to them...
- DaniFong 16y ago
  Thanks for the link, Michael. I wonder how far the link goes the other way? One of these days, I want to try to sort out the major results and foundations in the major topics of physics in a big map, showing what has been shown to follow from what. Like the complexity zoology inclusion diagrams (http://www.math.ucdavis.edu/~greg/zoology/diagram.xml http://www.math.ucdavis.edu/~greg/zoology/diagram.xml), only more general. I have the suspicion that a lot of the proofs of physics are in fact in some important way circular, but based on my first attempts I think I need to a computer to help me track all the logical dependencies.
robryan 16y ago
We are at a point where belief in a god is probably at an all time low due to our greater understanding of science without the basics being to complex. Gravity is currently a simple enough concept that most people can understand it in a local context. It will be interesting to see if in the future it is found that the laws of nature are much more complex than most of us can comprehend do more people again proclaim a god as the answer. Of course it could go the other way and we find nice formulas to better describe the universe.
- AndrewDucker 16y ago
  The problem with that is that we'd ne using the word "God" to mean "I don't know". Which doesn't tell us anything about God, what God wants, etc. This is generally known as the http://en.wikipedia.org/wiki/God_of_the_gaps http://en.wikipedia.org/wiki/God_of_the_gaps
nphase 16y ago
Nope. Not real; I'm currently floating. Silly bogus comment aside: I hate paywalls.
- donohoe 16y ago
  "I hate paywalls" If you mean the NYT paywall? There is none. Yet. Being asked to log-in to a site to view content (still for free) is annoying but it is not a paywall.
  - nphase 16y ago
    I see NYT log in screen, I immediately close the window. It's a hard habit to fix.
Confusion 16y ago
On the one hand, gravity hasn't been 'real' since Einstein: it's a secondary effect due to the curvature of space. On the other hand, gravity has been real since long before Newton: we experience it rather directly. The editorialized title gives the impression that there are entirely new insights concerning the 'reality' of gravity and that is certainly not the case.
- wlievens 16y ago
  "Scientist has hypothesized that gravity's origin may be somewhat different from previously considered, with no effect whatsoever on the real world" doesn't make for a very sensatinal headline.
  - Confusion 16y ago
    The original headline 'A Scientist Takes On Gravity' is good enough for the NYT and therefore good enough for HN.
    - lurkinggrue 16y ago
      He took on gravity... but did gravity win?
      - alisey 16y ago
        Gravity always wins.
- gwern 16y ago
  > "...but I have not been able to discover the cause of those properties of gravity from phænomena, and I frame no hypotheses; for whatever is not deduced from the phænomena is to have no place in experimental philosophy. To us it is enough that gravity does really exist, and acts according to the laws which we have explained." --Sir Isaac Newton's _Mathematical Principles of Natural Philosophy_
sliverstorm 16y ago
Does anyone else find it ironic that the way we usually visualize the cause of gravity (wells or dents or pockets formed in the fabric of spacetime) depends on gravity to cause things to fall into the wells? In the absence of gravity, it makes no sense to expect things to fall into the well.
- danparsonson 16y ago
  It sounds like you might be taking the 'bumpy surface' space-time metaphor too literally - I think it's only meant as an easy way to visualise the idea of curvature in more than three dimensions using our three-dimensional brains, rather than suggesting that there is actually a force acting perpendicular to the 'surface' the pulls objects into gravity wells. Were that not the case, then, as you say, the external force required to make gravity work would be gravity itself, which is a bit like the homunculus theory of consciousness (http://en.wikipedia.org/wiki/Homunculus http://en.wikipedia.org/wiki/Homunculus).
sajid 16y ago
This is a ridiculous paper, it would have been dismissed as the work of a crackpot if the author wasn't a respected string theorist.
Maro 16y ago
Original paper (degree in Physics needed): http://arxiv.org/abs/1001.0785 http://arxiv.org/abs/1001.0785 Discusion of the paper: http://badphysics.wordpress.com/2010/01/11/%E2%80%9Con-the-origin-of-gravity-and-the-laws-of-newton%E2%80%9D-by-erik-verlinde/ http://badphysics.wordpress.com/2010/01/11/%E2%80%9Con-the-o... Reply(s) by the author, Verlinde: http://staff.science.uva.nl/~erikv/page20/page18/page18.html http://staff.science.uva.nl/~erikv/page20/page18/page18.html

59 points by donohoe 16y ago

I would like to respectfully say that this article is only superficially appealing and therefore not proper for HN. This is just a hypothesis without mathematical basis. All you really need to read is the last few paragraphs to see that there isn't any mathematical rigor to it. This is a whole article about speculation about gravity, and it wastes a lot of time trying to hype up a physicist that won't flush out his math.

vecter 16y ago
I haven't had a chance to go through the paper yet (http://arxiv.org/abs/1001.0785 http://arxiv.org/abs/1001.0785), but it seems that he does make some derivations and proof sketches. Can someone verify this?
- rubidium 16y ago
  I got through page 11 before loosing the plot, and it seems to be a very light mathematical treatment of the subject. More of a "what if we thought about it this way?" then a "here's the proof" type paper.
  - Qz 16y ago
    Relativity started with "what if we thought about it this way?". Just saying.
    - robryan 16y ago
      Yeah part of the process, because of this new paper someone might get an idea they wouldn't have had to expand upon it. You see articles stating that something broke the laws of physics when really it just didn't fit our current model of understanding.
      - pyre 16y ago
        > You see articles stating that something broke the > laws of physics when really it just didn't fit our > current model of understanding. It 'broke the law' in so much as it proved that the law was a 'broken' law (aka incomplete). It wasn't an action that violated a law, but a law that was rendered 'broken' by an action.
    - rubidium 16y ago
      Yes, exactly. That's why it's worth talking about in the first place. I wasn't downplaying the paper, just observing what I could about the current strength of its claims. It's more of a Gedankenexperiment with some guiding equations, which it seems the author stated as his intent in the nytimes article.
- varjag 16y ago
  I'm not a physics major, but it appears superficial, non conclusive and light on math. At this point it's not a theory, but an (interesting as it may be) speculation.
  - bertm 16y ago
    This paper built upon work that Stephen Hawking did. "The hypothesis of gravity being an entropic force has a history that goes back to research on black hole thermodynamics by Bekenstein and Hawking in the mid-1970s. These studies suggest a deep connection between gravity and thermodynamics." http://en.wikipedia.org/wiki/Gravity_as_an_entropic_force http://en.wikipedia.org/wiki/Gravity_as_an_entropic_force someone might be able to find a better source.
rjprins 16y ago
Since when does HN need mathematical rigor for hypotheses? I have never seen this standard applied to blog posts about how to be a leader, pitching your ideas, how to program, etc. All of which usually don't come with the statistical proof with which they should come if they want to make a scientific claim... It's all just insights and thoughts.
dasil003 16y ago
In order for anyone to take your opinion about what is proper for HN seriously you need to post it from an account that actually has an investment in HN.

michael_nielsen 16y ago

I haven't read the Verlinde paper, but wanted to mention one of the papers it apparently builds on. That's Ted Jacobson's remarkable paper showing that gravity is a consequence of (1) thermodynamics and (2) the black hole entropy law. The paper is http://arxiv.org/abs/gr-qc/9504004 http://arxiv.org/abs/gr-qc/9504004 Sabine Hossenfelder has some useful comments on Verlinde's work here: http://backreaction.blogspot.com/2010/03/gravity-is-entropy-is-gravity-is.html http://backreaction.blogspot.com/2010/03/gravity-is-entropy-...

yannis 16y ago
You can also get more links from Verlinde himself http://twitter.com/erikverlinde http://twitter.com/erikverlinde but as he twitts Tomorrow I have to teach. Third year students. They also want to hear about emergent gravity. It is going to be tough to explain it to them...
DaniFong 16y ago
Thanks for the link, Michael. I wonder how far the link goes the other way? One of these days, I want to try to sort out the major results and foundations in the major topics of physics in a big map, showing what has been shown to follow from what. Like the complexity zoology inclusion diagrams (http://www.math.ucdavis.edu/~greg/zoology/diagram.xml http://www.math.ucdavis.edu/~greg/zoology/diagram.xml), only more general. I have the suspicion that a lot of the proofs of physics are in fact in some important way circular, but based on my first attempts I think I need to a computer to help me track all the logical dependencies.

robryan 16y ago

We are at a point where belief in a god is probably at an all time low due to our greater understanding of science without the basics being to complex. Gravity is currently a simple enough concept that most people can understand it in a local context. It will be interesting to see if in the future it is found that the laws of nature are much more complex than most of us can comprehend do more people again proclaim a god as the answer. Of course it could go the other way and we find nice formulas to better describe the universe.

AndrewDucker 16y ago
The problem with that is that we'd ne using the word "God" to mean "I don't know". Which doesn't tell us anything about God, what God wants, etc. This is generally known as the http://en.wikipedia.org/wiki/God_of_the_gaps http://en.wikipedia.org/wiki/God_of_the_gaps

nphase 16y ago

Nope. Not real; I'm currently floating. Silly bogus comment aside: I hate paywalls.

donohoe 16y ago
"I hate paywalls" If you mean the NYT paywall? There is none. Yet. Being asked to log-in to a site to view content (still for free) is annoying but it is not a paywall.
- nphase 16y ago
  I see NYT log in screen, I immediately close the window. It's a hard habit to fix.

Confusion 16y ago

On the one hand, gravity hasn't been 'real' since Einstein: it's a secondary effect due to the curvature of space. On the other hand, gravity has been real since long before Newton: we experience it rather directly. The editorialized title gives the impression that there are entirely new insights concerning the 'reality' of gravity and that is certainly not the case.

wlievens 16y ago
"Scientist has hypothesized that gravity's origin may be somewhat different from previously considered, with no effect whatsoever on the real world" doesn't make for a very sensatinal headline.
- Confusion 16y ago
  The original headline 'A Scientist Takes On Gravity' is good enough for the NYT and therefore good enough for HN.
  - lurkinggrue 16y ago
    He took on gravity... but did gravity win?
    - alisey 16y ago
      Gravity always wins.
gwern 16y ago
> "...but I have not been able to discover the cause of those properties of gravity from phænomena, and I frame no hypotheses; for whatever is not deduced from the phænomena is to have no place in experimental philosophy. To us it is enough that gravity does really exist, and acts according to the laws which we have explained." --Sir Isaac Newton's _Mathematical Principles of Natural Philosophy_

sliverstorm 16y ago

Does anyone else find it ironic that the way we usually visualize the cause of gravity (wells or dents or pockets formed in the fabric of spacetime) depends on gravity to cause things to fall into the wells? In the absence of gravity, it makes no sense to expect things to fall into the well.

danparsonson 16y ago
It sounds like you might be taking the 'bumpy surface' space-time metaphor too literally - I think it's only meant as an easy way to visualise the idea of curvature in more than three dimensions using our three-dimensional brains, rather than suggesting that there is actually a force acting perpendicular to the 'surface' the pulls objects into gravity wells. Were that not the case, then, as you say, the external force required to make gravity work would be gravity itself, which is a bit like the homunculus theory of consciousness (http://en.wikipedia.org/wiki/Homunculus http://en.wikipedia.org/wiki/Homunculus).

sajid 16y ago

This is a ridiculous paper, it would have been dismissed as the work of a crackpot if the author wasn't a respected string theorist.

Maro 16y ago

Original paper (degree in Physics needed): http://arxiv.org/abs/1001.0785 http://arxiv.org/abs/1001.0785 Discusion of the paper: http://badphysics.wordpress.com/2010/01/11/%E2%80%9Con-the-origin-of-gravity-and-the-laws-of-newton%E2%80%9D-by-erik-verlinde/ http://badphysics.wordpress.com/2010/01/11/%E2%80%9Con-the-o... Reply(s) by the author, Verlinde: http://staff.science.uva.nl/~erikv/page20/page18/page18.html http://staff.science.uva.nl/~erikv/page20/page18/page18.html