Observational evidence for the existence of Dark Matter is limited to its gravitational effects. The extensive program for dedicated searches has yielded null results so far, challenging the most popular models. Here we propose that this is the case because the very existence of cold Dark Matter is a manifestation of gravity itself. The consistent bimetric theory of gravity, the only known ghost-free extension of General Relativity involving a massless and a massive spin-2 field, automatically contains a perfect Dark Matter candidate. We demonstrate that the massive spin-2 particle can be heavy, stable on cosmological scales, and that it interacts with matter only through a gravitational type of coupling. Remarkably, these features persist in the same region of parameter space where bimetric theory satisfies the current gravity tests. We show that the observed Dark Matter abundance can be generated via freeze-in and suggest possible particle physics and gravitational signatures of our bimetric Dark Matter model.You heard it here first. Probably.
Tuesday, May 03, 2016
A new dark matter solution?
Speculative theories of gravity are a dime a dozen on arXiv, and I don't usually pay that much attention to them (well, they are hard to understand); but I am interested to see that there are two recent papers up, one by a handful of European physicists, and another by a couple of Japanese ones, talking about a bimetric theory of gravity that incorporates something that makes sense as a dark matter particle. Here's the European abstract:
How ignorant can you get?
Very, very ignorant, if you just live in the Right wing climate change denial-o-sphere, as does Steve Kates. (Climate change denial goes hand in hand with believing Obama has crushed and killed freedom, the American economy, and all Western values, by the way. That's Kates' other favourite line at Catallaxy.)
Anyway, my evidence for his extreme, gob smacking ignorance, is this from his recent short post:
Not that Kates would have known of the Bickmore post. It's outside his denial-o-sphere.
I see that only a few comments have been made at the Catallaxy post. Is it possible that even they can see when Kates is exaggerating to a ridiculous extent?
Anyway, my evidence for his extreme, gob smacking ignorance, is this from his recent short post:
Global warming is almost totally out of the news since the evidence that is happening has all but disappeared.This is by way of introduction to a video by retired climate scientist Lindzen, which had already been thoroughly debunked (at length) by Barry Bickmore.
Not that Kates would have known of the Bickmore post. It's outside his denial-o-sphere.
I see that only a few comments have been made at the Catallaxy post. Is it possible that even they can see when Kates is exaggerating to a ridiculous extent?
Skepticism on company tax cuts
From Crikey. (Bernard Keane is a real mix of policy beliefs, no? Often, when it comes to "nanny state" issues like licensing hours, he sounds like a libertarian. But he hates them on guns, and hardly follows their small government economics to the letter.)
Monday, May 02, 2016
About those submarines...
It's been a little while since the Turnbull government announced it was going to go with a fleet of French designed, Australian built, submarines. Twelve of them, in fact, but (as I understand it) to be built at a somewhat glacial pace.
A few observations, if I may:
a. of course this will be criticised. Surely the public has noticed that all major Defence acquisition programs look, at one stage or another, to have been a wrong decision: at least in terms of cost, and often in technical ways too. So it doesn't matter which of the contenders had been chosen - any would have been criticised and would go wrong in one way or another.
b. Apparently, Defence came out strongly in favour of the French bid. Given that Abbott had told the Japanese, apparently on a handshake (and probably one of his stupid winks) that they had the deal in the bag, this gives someone like me who disliked PM Abbott decidedly mixed feelings. On the one hand, it's deprived us of the criticism of the Japanese subs which would have been inevitable (see above), and hence the blaming of Abbott when the Defence preference was made known; on the other hand, I have a sneaking suspicion that Abbott might have been right - the Japanese submarine probably would have been ultimately fine; cheaper too. The Japanese remain good at hi tec stuff at a reasonable price. The French do well in aerospace, but not sure about cost. Is it silly of me to think I can judge a nation's likely submarine building capacity from their car making ability? Because I would prefer a Japanese luxury car to a French one. Not that I know anything really about luxury cars, either.
c. The criticism of the contract is already starting, and, amusingly, it's the "delcons" who don't like Turnbull, such as Andrew Bolt, leading the charge. All further evidence of the internal crisis in the Coalition. Does Bolt really think he is doing the Coalition a favour by criticising them for making a decision that Defence wanted? Or that he is helping Australia's diplomatic standing by dredging up what France did 50 years ago? Once again, I sense a Turnbull "with friends like Bolt, who needs enemies" response coming.
d. Twelve submarines? Really? As I have mentioned before, without a willingness to have Filipino seaman run them under contract, I thought we couldn't even manage [insert gender neutral word for "manning"] the 2 or 3 Collins class that are available at any one time. And that's despite throwing money at sailors to try to convince them to become submariners. Seriously, how does the government intend dealing with that problem? And is there room for Labor to make political headway by announcing that if it wins the next election, it'll only be going to contract for 9 or 10 submarines, saving a substantial amount of money in the process? I reckon there could be.
e. Building them here was an inevitable result of politics trumping dry economics, but I have no big problem with that. There does seem to be speculation, though, that what the Liberals are doing in concentrating spending in Adelaide and WA is going to be at the expense of votes in Queensland - especially with them not being able to at least throw Queensland the bone of some patrol boat builds.
A somewhat more serious take on the economics of supporting industry (esp defence industry) can be found here at the Lowy Institute.
A few observations, if I may:
a. of course this will be criticised. Surely the public has noticed that all major Defence acquisition programs look, at one stage or another, to have been a wrong decision: at least in terms of cost, and often in technical ways too. So it doesn't matter which of the contenders had been chosen - any would have been criticised and would go wrong in one way or another.
b. Apparently, Defence came out strongly in favour of the French bid. Given that Abbott had told the Japanese, apparently on a handshake (and probably one of his stupid winks) that they had the deal in the bag, this gives someone like me who disliked PM Abbott decidedly mixed feelings. On the one hand, it's deprived us of the criticism of the Japanese subs which would have been inevitable (see above), and hence the blaming of Abbott when the Defence preference was made known; on the other hand, I have a sneaking suspicion that Abbott might have been right - the Japanese submarine probably would have been ultimately fine; cheaper too. The Japanese remain good at hi tec stuff at a reasonable price. The French do well in aerospace, but not sure about cost. Is it silly of me to think I can judge a nation's likely submarine building capacity from their car making ability? Because I would prefer a Japanese luxury car to a French one. Not that I know anything really about luxury cars, either.
c. The criticism of the contract is already starting, and, amusingly, it's the "delcons" who don't like Turnbull, such as Andrew Bolt, leading the charge. All further evidence of the internal crisis in the Coalition. Does Bolt really think he is doing the Coalition a favour by criticising them for making a decision that Defence wanted? Or that he is helping Australia's diplomatic standing by dredging up what France did 50 years ago? Once again, I sense a Turnbull "with friends like Bolt, who needs enemies" response coming.
d. Twelve submarines? Really? As I have mentioned before, without a willingness to have Filipino seaman run them under contract, I thought we couldn't even manage [insert gender neutral word for "manning"] the 2 or 3 Collins class that are available at any one time. And that's despite throwing money at sailors to try to convince them to become submariners. Seriously, how does the government intend dealing with that problem? And is there room for Labor to make political headway by announcing that if it wins the next election, it'll only be going to contract for 9 or 10 submarines, saving a substantial amount of money in the process? I reckon there could be.
e. Building them here was an inevitable result of politics trumping dry economics, but I have no big problem with that. There does seem to be speculation, though, that what the Liberals are doing in concentrating spending in Adelaide and WA is going to be at the expense of votes in Queensland - especially with them not being able to at least throw Queensland the bone of some patrol boat builds.
A somewhat more serious take on the economics of supporting industry (esp defence industry) can be found here at the Lowy Institute.
Following the Republicans
It's kind of fascinating, if not edifying, to watch the Coalition in Australia follow the path of the Republicans.
I don't know how long the Liberals have sent people over to America to study Republican electoral tactics, and I suppose that you can't blame them for thinking they might learn something useful.
Instead, it has just encouraged a contagion of the American Republican problem to Australian right wing politics - what with the climate change denial, economic rabid anti-Keynesians and Laffer-ites continually decrying economic pragmatists in Treasury (and confused Coalition Treasurers trying to walk a path between the two), and the revival of culture wars amongst the conservatives with more than a dash of misogyny thrown in.
On the last point, it's hard to read the return of Chris Kenny to his own vomit of the Abbott/News Ltd attack of Gillian Triggs in any other way. It's just the nuttiest and most strangely obsessive personal attack on a statutory appointment I can ever recall coming from the Right of Australian politics.
I expect it must also dismay Malcolm Turnbull, too. But one of the mysteries for which we have to wait (perhaps) another few years, until he publishes his account of his time in office, is how he must really feel about having to dance with and corral the conservative ideologues in his party. Surely he is doing his part, with hypocritical walking back from former views on everything from climate change policy to negative gearing, but is he really happy doing it?
The split within the Right in Australia at the moment is such an obvious (but smaller scale) version of the split within the Right in America. Sure, we don't have a populist like Trump shaking up the corridors of Right wing power; but we did have the pretty close analogue of blowhard Clive Palmer. Perhaps in that respect we are slightly ahead of the Americans, in that Palmer has (politically) blown apart already, but we are waiting another 6 months or so before we see it happen to Trump. Who can doubt that, if we had some similar electoral system to the Americans, that Palmer would have run for President in the same self funded manner?
It could be right, what the dimwitted Abbott diehards are muttering to themselves - that the best thing that can happen to the Coalition is a surprise fail at the next election. [It's hilarious reading Catallaxy at the moment, where the pro Abbott supporters congregate and threaten a Labor vote, while openly dissing Sinclair Davidson for his support of the Turnbull overthrow. It seems that SD can't ban anymore commenters who are rude to his face (up to and including one who now openly calls him an "idiot") because of the large number he would have to cull.] The only thing is, the "delcons" (delusional conservatives) think that it will vindicate them - so their imperviousness to evidence will remain a problem, unless they are the ones to then leave the fold and establish a breakaway conservative party. Yes, let that happen, and let the moderates of the Right tell their Party they have to decide whether to stand with the evidence free, ideologically driven side of the Right, or go with the centrist and and pragmatic Right. It may be the only way to resolve the current problems.
I don't know how long the Liberals have sent people over to America to study Republican electoral tactics, and I suppose that you can't blame them for thinking they might learn something useful.
Instead, it has just encouraged a contagion of the American Republican problem to Australian right wing politics - what with the climate change denial, economic rabid anti-Keynesians and Laffer-ites continually decrying economic pragmatists in Treasury (and confused Coalition Treasurers trying to walk a path between the two), and the revival of culture wars amongst the conservatives with more than a dash of misogyny thrown in.
On the last point, it's hard to read the return of Chris Kenny to his own vomit of the Abbott/News Ltd attack of Gillian Triggs in any other way. It's just the nuttiest and most strangely obsessive personal attack on a statutory appointment I can ever recall coming from the Right of Australian politics.
I expect it must also dismay Malcolm Turnbull, too. But one of the mysteries for which we have to wait (perhaps) another few years, until he publishes his account of his time in office, is how he must really feel about having to dance with and corral the conservative ideologues in his party. Surely he is doing his part, with hypocritical walking back from former views on everything from climate change policy to negative gearing, but is he really happy doing it?
The split within the Right in Australia at the moment is such an obvious (but smaller scale) version of the split within the Right in America. Sure, we don't have a populist like Trump shaking up the corridors of Right wing power; but we did have the pretty close analogue of blowhard Clive Palmer. Perhaps in that respect we are slightly ahead of the Americans, in that Palmer has (politically) blown apart already, but we are waiting another 6 months or so before we see it happen to Trump. Who can doubt that, if we had some similar electoral system to the Americans, that Palmer would have run for President in the same self funded manner?
It could be right, what the dimwitted Abbott diehards are muttering to themselves - that the best thing that can happen to the Coalition is a surprise fail at the next election. [It's hilarious reading Catallaxy at the moment, where the pro Abbott supporters congregate and threaten a Labor vote, while openly dissing Sinclair Davidson for his support of the Turnbull overthrow. It seems that SD can't ban anymore commenters who are rude to his face (up to and including one who now openly calls him an "idiot") because of the large number he would have to cull.] The only thing is, the "delcons" (delusional conservatives) think that it will vindicate them - so their imperviousness to evidence will remain a problem, unless they are the ones to then leave the fold and establish a breakaway conservative party. Yes, let that happen, and let the moderates of the Right tell their Party they have to decide whether to stand with the evidence free, ideologically driven side of the Right, or go with the centrist and and pragmatic Right. It may be the only way to resolve the current problems.
Sunday, May 01, 2016
MIT needs a new writer
The Curious Link Between the Fly-By Anomaly and the “Impossible” EmDrive Thruster
What's this? MIT Technology Review appears to have a writer who is completely on board with the EmDrive being a real, new physics thing.
I remain deeply skeptical. And someone in comments claims (not sure if it is right, though), that the EmDrive, if true and configured right, could generate its own power and zip around forever. So you could build your own UFOs powered by perpetual motion, I guess. Would be rather cool, but come on, how likely is that?
What's this? MIT Technology Review appears to have a writer who is completely on board with the EmDrive being a real, new physics thing.
I remain deeply skeptical. And someone in comments claims (not sure if it is right, though), that the EmDrive, if true and configured right, could generate its own power and zip around forever. So you could build your own UFOs powered by perpetual motion, I guess. Would be rather cool, but come on, how likely is that?
Friday, April 29, 2016
I'll take it up when they can get it down to 45 seconds
The Case for the 1-Minute Workout Is Getting Stronger | TIME: In the latest study, published in PLOS One, exercise scientists led by Martin Gibala, chair of kinesiology at McMaster University, who has spent the last several years documenting the health benefits of interval training, found that as little as one minute of intensive exercise could have the same health benefits for the heart, respiratory fitness and muscles as 45 minutes of more typical continuous exercise over three months.
Granted, those 60 seconds have to be at a sprint-like pace, as if you’re being chased down by a tiger and fueled by adrenaline. But it’s just 60 seconds. “I think there is good evidence that shows you can see comparable benefits despite the fact that intervals require less total exercise and reduced time commitment,” says Gibala.
Stiglitz on economists
Joseph Stiglitz Talks About Inequality and the Economy - The Atlantic:
Stiglitz: The prevalent ideology—when I say prevalent it’s not all economists— held that markets were basically efficient, that they were stable. You had people like Greenspan and Bernanke saying things like “markets don't generate bubbles.” They had precise models that were precisely wrong and gave them confidence in theories that led to the policies that were responsible for the crisis, and responsible for the growth in inequality. Alternative theories would have led to very different policies. For instance, the tax cut in 2001 and 2003 under President Bush. Economists that are very widely respected were cutting taxes at the top, increasing inequality in our society when what we needed was just the opposite. Most of the models used by economists ignored inequality. They pretended that macroeconomy was unaffected by inequality. I think that was totally wrong. The strange thing about the economics profession over the last 35 year is that there has been two strands: One very strongly focusing on the limitations of the market, and then another saying how wonderful markets were. Unfortunately too much attention was being paid to that second strand.
What can we do about it? We've had this very strong strand that is focused on the limitations and market imperfections. A very large fraction of the younger people, this is what they want to work on. It's very hard to persuade a young person who has seen the Great Recession, who has seen all the problems with inequality, to tell them inequality is not important and that markets are always efficient. They'd think you're crazy.
Gut microbiome research, continued
Lifestyle has a strong impact on intestinal bacteria
This study of some healthy Dutch people still concludes that having a higher diversity bunch of bugs in your gut is healthier. Not exactly an intuitive result, compared to what people probably would have thought until recently:
This study of some healthy Dutch people still concludes that having a higher diversity bunch of bugs in your gut is healthier. Not exactly an intuitive result, compared to what people probably would have thought until recently:
This DNA analysis made it possible to examine which factors impact the diversity of the microbiome (the intestinal bacterial community unique to each of us). And that appears to be many. Wijmenga says, "You see, for example, the effect of diet in the gut." People who regularly
consume yogurt or buttermilk have a greater diversity of gut bacteria. Coffee and wine can increase the diversity as well, while whole milk or a high-calorie diet can decrease it.
"In total we found 60 dietary factors that influence the diversity. What these mean exactly is still hard to say," explains UMCG researcher Alexandra Zhernakova, the first author of the Science article. "But there is a good correlation between diversity and health: greater diversity is better."
Clear writing on negative gearing
How negative gearing replaced the great Australian dream and distorted the economy | Greg Jericho | Business | The Guardian
An excellent, clear bit of explanation from Greg Jericho on the investment distorting effect of our current negative gearing/CGT system in Australia.
It's pretty appalling, really, that once again, political games prevents politicians (I'm looking at you, Malcolm Turnbull) speaking honestly about an economic issue. (It's going to do the same to him on climate change policy, too.) This is why people become cynical about politics.
An excellent, clear bit of explanation from Greg Jericho on the investment distorting effect of our current negative gearing/CGT system in Australia.
It's pretty appalling, really, that once again, political games prevents politicians (I'm looking at you, Malcolm Turnbull) speaking honestly about an economic issue. (It's going to do the same to him on climate change policy, too.) This is why people become cynical about politics.
Disturbing food
The BBC has an article up about food photographers, and it includes this example:
I'm pretty sure that I wouldn't be the only person who would be feel a tad queasy if served that dish in a restaurant. Oh, sure, everyone with a phone would probably want to photograph it (although I personally have never done that in public), but that's not the point.
I'm pretty sure that I wouldn't be the only person who would be feel a tad queasy if served that dish in a restaurant. Oh, sure, everyone with a phone would probably want to photograph it (although I personally have never done that in public), but that's not the point.
A pretty convincing analysis
The truth about gun ownership after Port Arthur - The Drum (Australian Broadcasting Corporation)
One thing that interested me in this is the explanation that the increase in gun numbers in Australia in the last decade or so has not been into more households - proportionally, about the same number of households have guns. As the author notes, this is a similar phenomena as has occurred in America.
In America, I take it as pretty convincing evidence of the paranoid streak that runs in its right wing politics (especially in the last decade or two), and reading the gun nutters who comment at Catallaxy, I find it hard to deny there is a similar strain in Australia.
Those in Australia who buy one (or want to buy one) for self protection ignore the risk to themselves and their family that having a gun in the household creates. (Nor the fact that there's a good chance the crim's gun they are worried about had a good chance of having originally come from a legal owner.) But then again, scratch a gun obsessed nut, and you'll have a much better than even chance of finding a climate change denier, too. They just aren't good at understanding the big picture.
One thing that interested me in this is the explanation that the increase in gun numbers in Australia in the last decade or so has not been into more households - proportionally, about the same number of households have guns. As the author notes, this is a similar phenomena as has occurred in America.
In America, I take it as pretty convincing evidence of the paranoid streak that runs in its right wing politics (especially in the last decade or two), and reading the gun nutters who comment at Catallaxy, I find it hard to deny there is a similar strain in Australia.
Those in Australia who buy one (or want to buy one) for self protection ignore the risk to themselves and their family that having a gun in the household creates. (Nor the fact that there's a good chance the crim's gun they are worried about had a good chance of having originally come from a legal owner.) But then again, scratch a gun obsessed nut, and you'll have a much better than even chance of finding a climate change denier, too. They just aren't good at understanding the big picture.
Thursday, April 28, 2016
The seriously immature Senator
Wicked Campers critics 'authoritarians disguised as hippies or feminists': Senator
Yes, it's Leyonhjelm, who says of the seriously sexist and routinely offensive Wicked Campers slogans:
Yes, it's Leyonhjelm, who says of the seriously sexist and routinely offensive Wicked Campers slogans:
"You need to be a particularly wowserish type of person to not find them funny."Actually, Senator, you need to have a sense of humour of the kind found in immature 14 year boys, as you do, to find any of them funny.
Hot in Asia
Punishing Heat Wave Sets Records Across Asia
You really have to feel sorry for the poor people in these regions who do not have airconditioning. This really sounds like heat that will kill:
You really have to feel sorry for the poor people in these regions who do not have airconditioning. This really sounds like heat that will kill:
And just how hot is it?
Titlagarh in the Indian state of Odisha sizzled at 48.5°C on April 24
— the highest reliably measured temperature for the country in any
April. Schools in Odisha were unexpectedly let out for the summer on
Tuesday. Classes will remain suspended until, at least, the third week
of July.
Cambodia saw a national all-time record high of 42.6°C set in Preah
Vihea province on April 15. That was two days after its neighbor to the
north, Laos, set its own national all-time high temperature of 42.3°C at
Seno.
Dozens of Thai weather stations have broken or tied their all-time record maximum temperatures this month.
The thermometer has been reaching 46.0°C in several towns in Myanmar,
still shy of the national record high of 47.2°C at Myinmu observed on
May 14, 2010.
A greener Earth with local droughts
Global Droughts: A Bad Year – Significant Figures by Peter Gleick
Peter Gleick lists the areas which have recently (over the past couple of years) had drought problems.
This seems to me a good thing to keep in mind when reading about the Earth becoming greener. Not much benefit to be had if its greener (and slightly wetter) where no one's living.
Peter Gleick lists the areas which have recently (over the past couple of years) had drought problems.
This seems to me a good thing to keep in mind when reading about the Earth becoming greener. Not much benefit to be had if its greener (and slightly wetter) where no one's living.
Rudd chat
I haven't seen all that many episodes of The Weekly this year (I'm a bit embarrassed to admit that I have MKR to blame), but I watched it last night, and was annoyed with the clearly increased amount of swearing on it.
Look, honestly, the writing is (generally) smart, it's only on at 8.30 pm (not like 11pm or later with the routinely sweary equivalent shows - such as John Oliver's - in the US), and the use of 4 or 5 "f...s" in a half hour really doesn't make it any funnier. Get your act together, ABC, and resist the intrusion of language we don't really want to normalise amongst your teen viewers. (As I tell my kids, swearing is partly wrong because it's boring when people develop it as a routine tic. And so many people do.)
Anyhow, I post here mainly to note the "Hard Chat" interview with Kevin Rudd, which was pretty funny. But I thought Rudd looked puffy faced, tired and not very well. I really do suspect his health may not be up to any high powered job, and why on Earth do people like him keep trying to get into positions of power when they can easily retire early and develop other interests and hobbies. (Or do charitable works, or whatever.)
Look, honestly, the writing is (generally) smart, it's only on at 8.30 pm (not like 11pm or later with the routinely sweary equivalent shows - such as John Oliver's - in the US), and the use of 4 or 5 "f...s" in a half hour really doesn't make it any funnier. Get your act together, ABC, and resist the intrusion of language we don't really want to normalise amongst your teen viewers. (As I tell my kids, swearing is partly wrong because it's boring when people develop it as a routine tic. And so many people do.)
Anyhow, I post here mainly to note the "Hard Chat" interview with Kevin Rudd, which was pretty funny. But I thought Rudd looked puffy faced, tired and not very well. I really do suspect his health may not be up to any high powered job, and why on Earth do people like him keep trying to get into positions of power when they can easily retire early and develop other interests and hobbies. (Or do charitable works, or whatever.)
Eating in the news
It's seems it's either too much or too little:
* The BBC reports about some amazing changes in obesity rates in China:
* In other eating disorder news, I was surprised to read about the search for the genetic role in anorexia nervosa. (I just hadn't really thought of genes playing much of a role in it.)
Given that the disease (often/always?) involves people developing a persistent ill founded reaction to their own body image (merely imagining that they are overweight), and transexualism can involve a not dissimilar distress at the look of their body, I wonder if anyone has looked for a genetic component to that?
* The BBC reports about some amazing changes in obesity rates in China:
Researchers found 17% of boys and 9% of girls under the age of 19 were obese in 2014, up from 1% for each in 1985.* In Japan, in the meantime, they apparently don't so well at dealing with anorexia and eating disorders. Culturally, I'm not sure they generally handle mental health issues all that well, but I think they are improving. Slowly.
The 29-year study, published in the European Journal of Preventive Cardiology, involved nearly 28,000 students in Shandong province.
The study used a stricter cut-off of the Body Mass Index (BMI) than the World Health Organization standard.
"It is the worst explosion of childhood and adolescent obesity that I have ever seen," Joep Perk from the European Society of Cardiology told AFP news agency.
The study said China's rapid socioeconomic and nutritional transition had led to an increase in energy intake and a decrease in physical activity.
* In other eating disorder news, I was surprised to read about the search for the genetic role in anorexia nervosa. (I just hadn't really thought of genes playing much of a role in it.)
Given that the disease (often/always?) involves people developing a persistent ill founded reaction to their own body image (merely imagining that they are overweight), and transexualism can involve a not dissimilar distress at the look of their body, I wonder if anyone has looked for a genetic component to that?
Wednesday, April 27, 2016
In praise of an add-on
I use Firefox as my preferred Windows browser. (It's not bad in Android too, but just a little bit slower than Chrome.)
But I just have an odd urge to praise its add-on Lightshot, a screenshot addition that I use frequently in blogging, but also quite often at work. It is just one of the handiest things to have at hand, and I really appreciate its simplicity, reliability and utility. Thank you, its creators.
And now back to your regular programming...
But I just have an odd urge to praise its add-on Lightshot, a screenshot addition that I use frequently in blogging, but also quite often at work. It is just one of the handiest things to have at hand, and I really appreciate its simplicity, reliability and utility. Thank you, its creators.
And now back to your regular programming...
Much, much bigger on the inside
It's hard not to think of the Tardis when reading a paper like this one: On the volume inside old black holes. It talks about the mind boggling concept of the insides of evaporating black holes being much larger than the exterior surface indicates. The abstract reads:
Black holes that have nearly evaporated are often thought of as small objects, due to their tiny exterior area. However, the horizon bounds large spacelike hypersurfaces. A compelling geometric perspective on the evolution of the interior geometry was recently shown to be provided by a generally covariant definition of the volume inside a black hole using maximal surfaces. In this article, we expand on previous results and show that finding the maximal surfaces in an arbitrary spherically symmetric spacetime is equivalent to a 1+1 geodesic problem. We then study the effect of Hawking radiation on the volume by computing the volume of maximal surfaces inside the apparent horizon of an evaporating black hole as a function of time at infinity: while the area is shrinking, the volume of these surfaces grows monotonically with advanced time, up to when the horizon has reached Planckian dimensions. The physical relevance of these results for the information paradox and the remnant scenarios are discussed.And then, from within the paper itself:
A few numbersImpressive, to put it mildly.
Before closing this section, let us put the above in perspective: when a solar mass (1030 kg) black hole becomes Planckian (it needs 1055 times the actual age of the universe), it will contain volumes equivalent to 105 times our observable universe, hidden behind a Planckian area (10−70 m2).
Perhaps more pertinent is to consider small primordial black holes with mass less than 1012 kg. Their initial horizon radius and volume are of the order of the proton charge radius (10−15m) and volume (10−45m3) respectively. They would be in the final stages of evaporation now, hiding volumes of about one litre (10−9m3).
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