Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

The fastest pulsar spins at 716Hz; its equator spins at 24% the speed of light

en.wikipedia.org

Post reply on HN
Print view View original

71–80 of 83 posts

Re: The fastest pulsar spins at 716Hz; its equator spins at 24% the speed of light

#71

Post by lifeisstillgood »

lifeisstillgood wrote: post #41
einrealist wrote: post #20

Earlier quoted context omitted.

It makes me sad because most of the births are in underdeveloped countries, where people have no access to clean water and healthy food. And as more people of countries like China enter middle class, the resources we depend on, will diminish faster and faster.

Please watch anything by Hans Rosling for an entertaining and educational counter-balance to your fears, ; while having some validity, over population is it one of humanities most pressing problems.

typo: over population is not one of humanities most pressing problems

Re: The fastest pulsar spins at 716Hz; its equator spins at 24% the speed of light

#72

Post by Kell »

dfc wrote: post #52

Linking to wikipedia pages with titles like this = Today I Learned on HN Yet another reason I like the "don't change the title; the title is not for editorializing" policy on HN.

So what are you proposing in this case, that the original poster had kept the Wikipedia title? Or that the linked Wikipedia article shouldn't have been posted at all ?

Because hn's anti editorialization policy is useless in both cases. For, in the first case, without editorialization, the title is completely useless except for experts on the subject. And for the second case, it has nothing to do with title editorialization, but with content.

Re: The fastest pulsar spins at 716Hz; its equator spins at 24% the speed of light

#73

Post by throwaway_yy2Di »

saalweachter wrote: post #51
Crito wrote: post #18

Earlier quoted context omitted.

Wolfram Alpha has 10^46 J as 100x the energy given off by a supernova. I don't know if that means your numbers are off, or if this star is just mind-bendingly insane.

You can pack a lot of energy into a rotating system. You have similar problems with ring worlds or terraforming Venus (which barely rotates at all). Transporting in the extra hydrogen and all the rest is trivial compared to spinning it up to a decent period.

I wonder if it's practical to store energy in rotating asteroids? For the terrestrial power grid. No friction, no (mechanical) safety hazards, just an expensive transmission problem.

edit: Back-of-the-envelope says it's a very bad idea, which is just barely plausible if your asteroid is extremely large, and has an extremely high tensile strength (maybe iron-nickel?). Oh well.

edit2: Also apparently there's a failure mode where if you do overestimate the strength of the asteroid's interior, it tears apart and (from e.g geosynchronous orbit) has a >5% chance of destroying most of the planet. D: Yeah, where I said "no mechanical safety hazards", I retract that.

Re: The fastest pulsar spins at 716Hz; its equator spins at 24% the speed of light

#74

Post by lifeisstillgood »

dredmorbius wrote: post #66
lifeisstillgood wrote: post #12

Earlier quoted context omitted.

I could not take my eyes off "One Birth" / "One Death" Fascinating - and I think humanity is "winning"

If you keep winning like that for too long you lose.

what's the timescale here ? Still on the same planet? Yeah maybe, but there is a lot of land here anyway.

Re: The fastest pulsar spins at 716Hz; its equator spins at 24% the speed of light

#75

Post by dredmorbius »

lifeisstillgood wrote: post #74
dredmorbius wrote: post #66

Earlier quoted context omitted.

If you keep winning like that for too long you lose.

what's the timescale here ? Still on the same planet? Yeah maybe, but there is a lot of land here anyway.

It's not land that's the problem, strictly speaking. Look up Leibig's Law of the Minimum.

The historical preindustrial peak human population was around 500-800 million. Maybe we'd be lucky and be able to sustain somewhat more than that, say 2 billion. I have a hard time seeing much more given energy and resource limitations.

Prediction's hard, especially about the future, but I suspect we're looking at a crisis well within 100 years. Possibly a few decades out, if that.

Look up Limits to Growth.

Re: The fastest pulsar spins at 716Hz; its equator spins at 24% the speed of light

#76

Post by deletes »

PeterisP wrote: post #58
deletes wrote: post #37

Earlier quoted context omitted.

Spacetime in the center of a perfect spherical object is the same as a point in empty space, you can't tell them apart. Of course that only counts for the exact point in the center. So the time will not tick slower there as to someone far from any objects.

Being unable to tell is not an argument for time not ticking slower; the whole point of time ticking slower is that everything is consistent for your point of reference and you can't tell, but your point of reference has different time than other points. Just as if you were inertially moving at 0.9c relative to me, the time frame would be different despite both me and you being 'the same as a point in empty space'.

My two comments above are wrong. Very counterintuitive. How can you have a difference with two points stationary relative to each other.

Re: The fastest pulsar spins at 716Hz; its equator spins at 24% the speed of light

#77

Post by einrealist »

lifeisstillgood wrote: post #41
einrealist wrote: post #20

Earlier quoted context omitted.

It makes me sad because most of the births are in underdeveloped countries, where people have no access to clean water and healthy food. And as more people of countries like China enter middle class, the resources we depend on, will diminish faster and faster.

Please watch anything by Hans Rosling for an entertaining and educational counter-balance to your fears, ; while having some validity, over population is it one of humanities most pressing problems.

Thanks, I will.

Re: The fastest pulsar spins at 716Hz; its equator spins at 24% the speed of light

#78

Post by stcredzero »

ars wrote: post #62
stcredzero wrote: post #49

Earlier quoted context omitted.

generator using the rotational energy...would need to have a reference in the main star Nope. You could launch generator pods in a hyperbolic trajectory that would start out escaping the neutron star, but generate electricity from the rotating magnetic field in such a way that it's captured in orbit and comes back to its launch point.

No you can't. Conservation of angular momentum doesn't allow that.

Yes you can. You just end up changing the angular momentum of two bodies, not just one. When you launch the pod, you slow down the body you launched from. The system as a whole conserves momentum and energy, but the amount of electricity you have increases.

Re: The fastest pulsar spins at 716Hz; its equator spins at 24% the speed of light

#79

Post by dfc »

Kell wrote: post #72
dfc wrote: post #52

Linking to wikipedia pages with titles like this = Today I Learned on HN Yet another reason I like the "don't change the title; the title is not for editorializing" policy on HN.

So what are you proposing in this case, that the original poster had kept the Wikipedia title? Or that the linked Wikipedia article shouldn't have been posted at all ? Because hn's anti editorialization policy is useless in both cases. For, in the first case, without editorialization, the title is completely useless except for experts on the subject. And for the second case, it has nothing to do with title editoriali…

The policy is: "Do not change the title." What is it that you are having trouble understanding?
Post reply on HN