Gravity and Levity
gravityandlevity.wordpress.com · Personal blog · on HN since 2009
A physicist writes explanatory posts on physics and everyday phenomena, including mortality rates, charge, magnetic fields and the atmosphere.
What HN saysHN commenters link it for its explanation of the Gompertz mortality curve and the "1% charged" thought experiment about a Coulomb explosion.
42HN people shared it
20linked it in comments
29stories submitted
1.8Kstory points
5 months agolast shared
2009people per year2026
Most-shared posts
- 1Your body wasn’t built to last: a lesson from human mortality rates18 people · 659 points · first shared 2009 · 175 comments on HN
- 2What if I were 1% charged? (2013)6 people · 406 points · first shared 2015 · 136 comments on HN
- 3How strong would a magnetic field have to be to kill you?6 people · 336 points · first shared 2015 · 114 comments on HN
- 4Why can’t I go faster than the speed of light?2 people · 271 points · first shared 2021 · 215 comments on HN
- 5What It Means and Doesn’t Mean to Get a Job in Physics (2019)2 people · 5 points · first shared 2019 · discussion on HN
- 6Braess’s Paradox and “The Ewing Theory”2 people · 3 points · first shared 2009 · discussion on HN
- 7How thick is the atmosphere? A derivation of the Boltzmann distribution1 people · 101 points · first shared 2018 · 20 comments on HN
- 8So is the universe made of tiny springs, or isn’t it?1 people · 3 points · first shared 2010 · 1 comments on HN
- 9How can electrons be “topological”?1 people · 3 points · first shared 2020 · discussion on HN
- 10Is every generation more attractive than the last? – a conjecture (2010)1 people · 2 points · first shared 2021 · discussion on HN
- 11The meaning of Noether’s Theorem (2011)1 people · 2 points · first shared 2015 · discussion on HN
- 12Self-reported happiness measured on a log-scale to relative to income.1 people · 2 points · first shared 2013 · discussion on HN
- 13The fastest possible mile (2009)1 people · 2 points · first shared 2018 · 1 comments on HN
- 14Reasons we don’t understand traffic1 people · 2 points · first shared 2023 · discussion on HN
- 15Pedestrians as interacting particles1 people · 2 points · first shared 2015 · discussion on HN
What HN people wrote when they linked it
didgeoridoo · 2024-07-28
Reminded me of this great post from a while back, “What if I were 1% charged?”[0] looking at the consequences if you were to remove one out of every 100 electrons in your body.
The answer: a Coulomb explosion powerful enough to rip the vacuum and generate antimatter from the void.
[0]: https://gravityandlevity.wordpress.com/2013/05/22/what-if-i-were-1-cha…
rweba · 2018-02-21
Two points:
(1) I haven't seen this article mentioned here:
https://gravityandlevity.wordpress.com/2009/07/08/your-body-wasnt-buil…
I am not sure if the article addressed this model in particular, but I found it compelling.
(2) It occurred to me that most of us don't fear death as much as becoming increasingly useless as we become older due to ill health and physical weakness.
It would be not much fun living to be 200 if the last 120 years were spent in a bed or wheelchair.
So what we want is not to increase the lifespan but to prolong the amount of time we can spend in relatively physically prime condition. I am sure this is not an original thought, but something worth mentioning.
AngryParsley · 2011-07-26
Mortality rates follow a Gompertz curve. This blog post explains it pretty well: http://gravityandlevity.wordpress.com/2009/07/08/your-body-wasnt-built…
There are many suspected specific reasons for why this is (telomeres shortening, mtDNA mutations, protein cross-links, etc), but it boils down to this: accumulating damage accumulates faster as self-repair mechanisms are damaged by accumulating damage.
yellowapple · 2015-01-14
I think the issue is that there are two conflicting populations on Hacker News: hackers/geeks/nerds in the traditional sense (who are here to talk about cool technology and such, and because the place is called "Hacker News") and entrepreneurs (who are here to talk about economics and politics and such, and because the place is run by a company that funds entrepreneurs).
Being part of the first group, it's a bit strange to me to see this sort of article on a site that's called "Hacker News", and I agree with the parent commenter that the article feels out-of-place here. Perhaps if it had some nifty technical details on flash bangs and their effects on humans (more concrete references to PTSD diagnoses, descriptions of temperatures attained by flashbangs and the physical effects of those temperatures on humans, even some possible elaboration on potential blindness caused by flashbangs) - in other words, things that hook into scientific basis (which makes nerds squee) rather than emotion/"ethics" (which doesn't make nerds squee) - would improve this.
On the other hand, I realize that my demographic is not the only one worth considering (regardless of whether I want it to be the only one worth considering). It's disappointing that articles with a dearth of technical description seem to be becoming the norm even here, but at the same time I realize that it's not disappointing to all of HN's users, so the best I can do is move on to a hopefully-better article (or stop using…
gwern · 2011-06-06
> IMHO living for centuries with the body of a 90 year old wouldn't be so bad. (Supposedly there's a point where the body stops getting any more frail.) And as long as you can keep mortality risk to a low enough level for long enough, it's just a matter of time before youthfulness-restoring tech comes along.
I'm sure you've seen http://gravityandlevity.wordpress.com/2009/07/08/your-body-wasnt-built… already, so you know you can't live for centuries with the body of a 90 year old because the decay and mortality is just too bad, fancy exosuits or no.
So this leads to the kind of odd thought experiment which runs more accurately like 'imagine you have the organs and general health of a 12 year old, but are weak and debilitated and functioning at a low level (though not getting any worse); would you still find life worth living today?'
I'd say the answer is yes. Elderly suicide is more frequent than among the middle-aged or younger, so life isn't as good (not a surprising claim), but suicide is still rare, so life is still somewhat good.
Misdicorl · 2023-05-08
They made a coulomb bomb https://gravityandlevity.wordpress.com/2013/05/22/what-if-i-were-1-cha…
> I worked on all sorts of problems that involved the Coulomb interaction, and occasionally my proposed solution would be very wrong. The worst kind of wrong was the one that made my advisor remark “What you just created is a Coulomb bomb,” which meant that I had proposed something that wasn’t neutral on the large scale.
Aeolun · 2021-11-01
I think I read a short blog post about that a while before: https://gravityandlevity.wordpress.com/2015/01/12/how-strong-would-a-m…
At least for how much would be safe.
a1369209993 · 2021-10-01
> If you were standing at arm's length from someone and each of you had one percent more electrons than protons[[0]]
The latent energy of electromagnetic repulsion between the two of you (never mind between the parts of each of your bodies) would be a bit more than ((1%*80kg/2amu*electroncharge)^2 coulombconst / meter), or on the order of a megaton. Not megaton tnt, a megaton of just energy (comparable to a million tons of antimatter).
0: https://gravityandlevity.wordpress.com/2013/05/22/what-if-i-were-1-cha…
random314 · 2021-09-12
I found a much better explanation today on hacker news. Linking it here
https://gravityandlevity.wordpress.com/2009/04/08/why-cant-i-go-faster…
Sniffnoy · 2021-09-09
This links to a comment on the blog post, rather than the blog post itself. The link should be https://gravityandlevity.wordpress.com/2015/01/12/how-strong-would-a-m…
moosekaka · 2018-02-16
Obligatory link to yesterdays topic
https://gravityandlevity.wordpress.com/2009/07/08/your-body-wasnt-buil…
pythonistic · 2017-04-01
A very strong magnetic field has bad health (neurological and intracellular) consequences. I can't find a good citation, but this blog post should help explain the risks.
https://gravityandlevity.wordpress.com/2015/01/12/how-strong-would-a-m…
adonovan · 2016-10-05
Gravity and Levity presented in 2009 a much better intuitive model and mathematical principle that explains this bold pronouncement:
https://gravityandlevity.wordpress.com/2009/07/08/your-body-wasnt-buil…
EGreg · 2016-09-08
Well, read this:
https://gravityandlevity.wordpress.com/2009/07/08/your-body-wasnt-buil…
and then consider that a slight change in one of the exponents could have a significant effect on a person's quality of life.
dexen · 2015-02-13
Tangentially related, a blogpost [1] on statistical approach to baseball teamwork with a dominating player, along with the earlier HN discussion [2].
[1] https://gravityandlevity.wordpress.com/2009/05/28/braesss-paradox-and-…
[2] https://news.ycombinator.com/item?id=771099
jostmey · 2014-03-22
Awhile ago there was a wonderful little post about the probability distributions of human lifespan. The distributions fall off super-exponentially with age. What this means is that chances of someone living past 130 without major medical intervention is astronomically small.
Even with medical intervention, it seems unlikely someone will live much past the 130 year barrier.
Link: http://gravityandlevity.wordpress.com/2009/07/08/your-body-wasnt-built…
rsaarelm · 2013-07-05
We've gotten good interventions for a lot of things that will kill you that aren't old age. But if you've already managed to live to 90, your further life expectancy might not be much better today than it would have been in Ancient Greece. See http://gravityandlevity.wordpress.com/2009/07/08/your-body-wasnt-built… for how bad things get when you age.
Some kind of medical intervention that targeted the actual senescence mechanism instead of just the other problems it causes would be an actual game-changer, and I don't see how we could get living past 100 to be very probable without coming up with one.
jimmytucson · 2012-08-19
Brian Skinner, physicist and basketball analytics extraordinaire, wrote a really nice blog post about this 3.5 years ago [1]. Mining the comments from that post shows it's been banged around numerous times before that [2][3].
[1] https://gravityandlevity.wordpress.com/2009/04/02/parenting-and-the-fe…
[2] http://www.nytimes.com/2009/04/21/science/21qna.html?_r=1
[3] http://web.archive.org/web/20071116094344/http://ourworld.compuserve.c…
panic · 2012-01-09
You can find the original, less ad-encrusted version of this article at http://gravityandlevity.wordpress.com/2009/07/08/your-body-wasnt-built…
pron · 2014-07-19
I don't know anything about global warming research to comment about the conclusion of the text, but I can say something about what is certainly a religious belief infecting those who respect science, and are then led to respect "science": nutrition. The truth is that we know very little about human nutrition, especially in healthy individuals. When John Ioannidis demonstrated that most published medical research is false (wholly or partially), he singled out nutrition and gene-association as two especially problematic fields. Yet, the reason many believe that reading some papers and changing their diets to include more or less protein -- or more or less fiber, or more or less fat -- has an effect on their health is pure religion and magical thinking. This magical thinking stems from a possibly innate (and certainly ingrained) belief that "our body is a temple", or that "we are what we eat", which is a particular manifestation of the more general psychological desire in what Jonathan Haidt calls "purity". This psychological need is combined with the false[1] seemingly-scientific belief that our bodies accumulate damage over time.
The scientific truth is that (other than obviously pathological cases of eating poison, or living on just fries for a year) we simply don't know what food is good for us, and certainly not in what quantity. It's actually worse: we don't even know if diet (again, non pathological) has any effect on health. It is absolutely possible (and even…