Another contrary view is that lengthening telomeres will not only fail to reduce the increase in cancers with age, but could accelerate it. Cell genomes accumulate mutations over time (and cell divisions). Longer telomeres let the cells hang around longer, but don't prevent or repair the mutations. Sometimes, anti-fortuitously, these mutations lead to a cell becoming cancerous. Killing off cells which have accumulated too much damage or divided too many times is one of the body's defenses against cancer, and longer telomeres can delay or defeat this defense.
(I'm not advocating either viewpoint - I know enough to be aware that the arguments exist, not enough to judge their correctness.)
I like this idea, but there is something of a slippery slope:
* Send us arbitrary design files and we'll make it for you (for profit) Legal, I think.
* Send us design files to make, and by the way this website is a good source of designs. Legal, I think
* Send us design files to make, and here on our website is a handy search tool for the designs on that other website Probably legal
* Send us design files to make, and here on our website is a handy search tool for that other website which displays their pages in a frame while in our frame we give the price and a one-click 'download the files and upload them to us and add the price to your shopping cart' button Legality unknown.
Note I am not a lawyer, and all the above is assuming designs with a non-commercial license. (If it is a commercial with attribution license, it would all be legal.)
Neutron irradiation can transform stable nuclei into radioactive ones. Some of those nuclei are pretty benign, others nasty. Pure water doesn't produce any nasties (just isotopes with a few minutes half-life, as I recall). However if you have impurities in the water, those might produce something nasty when bombarded with neutrons. I expect this is why they filter the water so carefully.
Parts of this story were puzzling to me, so off to Wikipedia...
https://en.wikipedia.org/wiki/... "Tritium is also produced in heavy water-moderated reactors whenever a deuterium nucleus captures a neutron." https://en.wikipedia.org/wiki/... Indian Point is a Pressurized Water Reactor. https://en.wikipedia.org/wiki/... PWRs are light water reactors, not heavy water --- so I'm still puzzled about the origin of the tritium. Is there enough deuterium in ordinary (light) water to produce it? At any rate, it sounds like their primary coolant loop is leaking, which has to be a worry.
From TFA: "John J. Kelly, former director of licensing for Indian Point and a certified healthy physicist, said that tritium is a radioactive form of hydrogen that is found naturally."
https://en.wikipedia.org/wiki/... "Tritium occurs naturally due to cosmic rays interacting with atmospheric gases.... Worldwide, the production of tritium from natural sources is 148,000 terabecquerels per year." However I'm thinking that the natural concentration of tritium is going to be many orders of magnitude lower than what they're finding near the plant. If so, this statement is wildly misleading - while technically true, it has no bearing on how hazardous this leak is. That arsenic is present in trace quantities in ground water doesn't make it safe in large doses.
As explained in your linked article, the latest version of Falcon 9 uses super-cold liquid oxygen, as it is denser. This means that they need to pump it in just before launch, so it doesn't have time to warm up. Previously the LO2 would have been loaded a few hours before launch, and there would have been plenty of time to deal with any loading issues, so this bit of cleverness has cost them a scrubbed launch. Hopefully it is just teething troubles and they'll be able to make the LO2 loading process reliable soon.
Here's my (very abbreviated) plan to overhall the US presidential election system. * The primaries become an official part of the constitutional system. Anybody who wants to be on the presidential ballot needs to get some threshold number/proportion of votes in the primaries. The threshold is set such that there will be about 3 to 6 candidates. * The presidential vote is done by preferential voting with a Condorcet voting system.
The big benefits: The Condorcet voting will tend to elect compromise candidates, whereas the current primary system means you don't get to be a candidate unless you're extremist (at least for one of the main parties in the current climate.) Because of preferential voting, each side of politics can put up more than one candidate without fear of losing by 'splitting the vote'. More choice, without bloating the ballot unmanageably. All candidates on the ballot have legitimacy through the primary system, so (hopefully) presidential candidate debates won't ignore the 'minor' candidates. It allows for candidates to differ on more axes than just left vs right. No more electoral college. Everyone's vote counts the same, whatever state they are in.
It takes billions (not millions) of years for hydrogen atoms to fuse in the sun - that is precisely why the sun has a billions-of-years lifetime. So in building a fusion reactor, we need many orders of magnitude higher reaction rates, and to achieve them at many orders of magnitude lower densities. One way of doing this is to have much higher temperatures. The solar core temperature is about 15 million degrees and TFA has 50 million degrees for this new result, and 80 million degrees for half a second at a European reactor. This sounds unimpressive, but the reaction rates are very sensitive to temperature - proportional to about T^8 as I recall, but I didn't quickly find an online reference for this. 75 million degrees would therefore give a boost of about 5^8 which is about 400,000.
In the sun, the first reaction in the chain (proton+proton->deuterium) is the rate limiting step. In a reactor, we can provide deuterium enriched fuel and bypass this step. I don't know what the reaction rates are, but I suspect that this will be a greater benefit that the higher temperatures. You can do even better with tritium in the fuel, but your reactor becomes an intense neutron source, leading to induced radioactivity in nearby materials. Some proposed designs use these neutrons to breed more tritium from a lithium blanket around the reactor. (Once I get beyond the proton-proton chain reaction, I'm just relying on pop-science knowledge, so corrections from the more knowledgeable are welcome.)
Stars a bit more massive than the sun burn hydrogen via the CNO cycle, which has even higher temperature dependence (from memory, about T^17). I've never heard of anyone suggesting using the CNO cycle in a fusion reactor - presumably there are good reasons, but I don't know what they are. One problem is you need to wait for radioactive decays, but these have half-lives on the order of 1 to 2 minutes, and a commercial reactor would be running for much longer than that.
Poll 1: Which nation/organization do you think will be next to land people on the moon? * China (CNSA) * USA (NASA) * Japan (JAXA) * Europe (ESA) * India (ISRO) * Russia (RFSA) * North Korea (KCST) * Privately funded (e.g. SpaceX, Blue Origin or Cowboy Neal without direct state support) (ETLA)
Poll 2: Which nation/organization do you want be next to land people on the moon? (same options)
NASA discovers little green men on the moon. NASA makes a 2 page press release. Bob writes a blog post where he condenses the NASA press release to 1 page, mostly by deleting every second paragraph. (Alternatively it could be a Javascript and advertising heavy commercial news site.) Slashdot posts an article linking to Bob's blog, rather than linking directly to NASA as they should. One of the first comments provides the direct link (with title something like "This is the link you should be using") and instantaneously gets modded to +5, in reward for having done what the Slashdot editor should have done.
I'm not saying never use secondary sources - sometimes Bob has summarized 50 pages to 1 page (and done a good job of it), or added some insightful commentary. Just don't use secondary sources unless they add significant value, and always include a link to the primary source in the summary.
It sounds like this system relies critically on the coefficient of friction between the slider grommets and the risers. Too high, and the slider never (or incompletely) slides and the chute does not fully inflate. Too low, and it inflates too fast and soon, bruising or breaking the parachutist or, worse, ripping the chute.
From the abruptness of the transition between slightly inflated and fully inflated in the space capsule chutes, and the prolonged delay before this occurs, I suspect the friction method you describe is not used. However a slider with some other release mechanism seems likely.
I think he has a plan for this, where he gets several years of free accommodation in a guarded and fortified building all at state expense. I think they call it a "safe house" or a "big house" or something like that.
There is a thing that these chutes do, where on initial deployment the open aperture of the chute is quite small, and the chute looks rather like a sausage. Then later on, the chute abruptly opens fully, and looks like a hemisphere. (The transition wasn't shown in the video in TFA, but I've seen it elsewhere and it is also simulated in Kerbal Space Program.)
How is this achieved? Is it some clever aerodynamics where the chute has two stable configurations and a 'catastrophic' transition? Is there some rope which constrains the aperture early on and then is somehow severed to allow fully deployment?
(I understand why - the first configuration slows the payload sufficiently so that the chute is not torn apart when it fully deploys. "How" is what I don't know.)
SpaceX love fourfold symmetry: octagonal layout of stage 1 rockets (plus one central, for 9 total). Four landing legs. Four steering fins at the top of stage I. Four pairs of "super Draco" landing/abort rockets on the Dragon. And now, four chutes.
However, statistical evidence is just an aggregation of anecdotal evidence.
No, sorry, completely wrong.
Statistical data comes from a well defined sample which is designed to be representative of an entire population. Anecdotes have no well defined selection criteria (my grandmother smoked until she was 100, and because I don't want to believe smoking is harmful, I remember and put great importance on this, and forget all the other people I have a connection to who were damaged by smoking) or (often where the selection criterion is 'stuff that happened to me') too little data to draw a conclusion (I've never crashed while driving drunk, so it must be safe.)
"I remember really hot days 10 years ago, hotter than now" holds very little weight. It is your experience (perhaps for every person like you there are 100 with the opposite experience), it is subject to biases of memory, and you've chosen the example retroactively to support a given position. The statistical data is thousands of thermometers measuring temperatures every hour over decades.
You can't sail a drilling platform up to a wharf to unload the rocket, like you can a barge (so your idea would require an extra transfer at sea from platform to barge), nor is it so easy to move around the landing spot to match mission requirements. Having said all that, if barge landings turn out to be sufficiently haphazard, your idea may be economical.
People could animate Hamlet with a certain mouse as the protagonist (so long as it looks like 1930s Willy not 21st century Mickey.) They could distribute the Steam Boat Willy cartoon modified so that the mouse protagonist is naked and has oversized genitalia - just so long as they never call the mouse protagonist "Mickey". I think these are the sorts of possibilities that give Disney executives sleepless nights.
Historians write a (very dubious) history book. Novelist writes a novel in which this dubious history is true. Historians sue. Historians lose. http://news.bbc.co.uk/2/hi/ent...
My analysis: You can't copyright facts. If you present something as a fact (such as in a history book), you lose any copyright over that "fact" (but not over your presentation of it.) Otherwise if you wrote a SF story involving Hawking radiation then Hawking could sue you.
This raises an interesting issue: If I edit Anne Frank's diary, I have copyright on the edited version. If I carefully set things up and take a high quality photo of the Mona Lisa, I have copyright over that photo. If a monkey takes a selfie with my camera and then I do a bunch of post-processing to "improve" it and publish the improved picture, I have copyright due to the improvements.
In each case, somebody else could read the diaries and publish their own edition, take their own photo of the Mona Lisa, or freely distribute the original unimproved monkey selfie - but only if they have access to the diaries (or facsimile), to the Mona Lisa without plate glass in the way, or the unimproved selfie. When access to the original is restricted, reproductions can effectively exert copyright over the original when the original is out of copyright. (The monkey selfie camera owner missed this trick.)
I've thought for some time that we should have video games for this. Make a game in which the speed of light is (e.g.) 30m/s and make it relativistically correct. (I've seen a simple version: run around a village collecting tokens, the more you collect the slower the speed of light.) Make a game in which quantum effects happen on a macroscopic scale. (I'm not sure how this one would work.) If you can figure out how to make 4D space into a game, I'll be impressed.
In any case, the hope is that with many childhood hours of playing such games, relativistic and quantum effects will become intuitive, and therefore as easy to learn as Newtonian mechanics.
Here is a stunning example of how bad the USA news cycle can be.
This story would be the night 19 August, 1991. I was a graduate student living not too far from New York. The previous day, I'd heard ominous indications of a coup in Russia, probably trying to return to Soviet style government. Having been out of touch with news media for about 24 hours ("graduate student", remember?) I felt the need for an update, so I tuned my radio to a New York city "24 hour news" radio station.
After a full 30 minutes, they hadn't even mentioned it once. Then the announcer said "And now back to tonight's top story..." "Finally!" I thought. "... basements flooded in Long Island" ARGH! I gave up. The world's second largest nuclear arsenal was potentially falling into the hands of hostile extremists, the Cold War could be restarting, and it didn't rate a mention compared to flooded basements.
Slashdot Mirror
Here is an argument that he got killed by a bad user interface.
Thanks for all that. I was unaware that mtDNA had any role in cancer.
Another contrary view is that lengthening telomeres will not only fail to reduce the increase in cancers with age, but could accelerate it. Cell genomes accumulate mutations over time (and cell divisions). Longer telomeres let the cells hang around longer, but don't prevent or repair the mutations. Sometimes, anti-fortuitously, these mutations lead to a cell becoming cancerous. Killing off cells which have accumulated too much damage or divided too many times is one of the body's defenses against cancer, and longer telomeres can delay or defeat this defense.
(I'm not advocating either viewpoint - I know enough to be aware that the arguments exist, not enough to judge their correctness.)
I like this idea, but there is something of a slippery slope:
* Send us arbitrary design files and we'll make it for you (for profit)
Legal, I think.
* Send us design files to make, and by the way this website is a good source of designs.
Legal, I think
* Send us design files to make, and here on our website is a handy search tool for the designs on that other website
Probably legal
* Send us design files to make, and here on our website is a handy search tool for that other website which displays their pages in a frame while in our frame we give the price and a one-click 'download the files and upload them to us and add the price to your shopping cart' button
Legality unknown.
Note I am not a lawyer, and all the above is assuming designs with a non-commercial license. (If it is a commercial with attribution license, it would all be legal.)
Thanks.
Neutron irradiation can transform stable nuclei into radioactive ones. Some of those nuclei are pretty benign, others nasty. Pure water doesn't produce any nasties (just isotopes with a few minutes half-life, as I recall). However if you have impurities in the water, those might produce something nasty when bombarded with neutrons. I expect this is why they filter the water so carefully.
Parts of this story were puzzling to me, so off to Wikipedia...
https://en.wikipedia.org/wiki/...
"Tritium is also produced in heavy water-moderated reactors whenever a deuterium nucleus captures a neutron."
https://en.wikipedia.org/wiki/...
Indian Point is a Pressurized Water Reactor.
https://en.wikipedia.org/wiki/...
PWRs are light water reactors, not heavy water --- so I'm still puzzled about the origin of the tritium. Is there enough deuterium in ordinary (light) water to produce it? At any rate, it sounds like their primary coolant loop is leaking, which has to be a worry.
From TFA: "John J. Kelly, former director of licensing for Indian Point and a certified healthy physicist, said that tritium is a radioactive form of hydrogen that is found naturally."
https://en.wikipedia.org/wiki/... ... Worldwide, the production of tritium from natural sources is 148,000 terabecquerels per year."
"Tritium occurs naturally due to cosmic rays interacting with atmospheric gases.
However I'm thinking that the natural concentration of tritium is going to be many orders of magnitude lower than what they're finding near the plant. If so, this statement is wildly misleading - while technically true, it has no bearing on how hazardous this leak is. That arsenic is present in trace quantities in ground water doesn't make it safe in large doses.
As explained in your linked article, the latest version of Falcon 9 uses super-cold liquid oxygen, as it is denser. This means that they need to pump it in just before launch, so it doesn't have time to warm up. Previously the LO2 would have been loaded a few hours before launch, and there would have been plenty of time to deal with any loading issues, so this bit of cleverness has cost them a scrubbed launch. Hopefully it is just teething troubles and they'll be able to make the LO2 loading process reliable soon.
I've proposed the following on /. before.
Here's my (very abbreviated) plan to overhall the US presidential election system.
* The primaries become an official part of the constitutional system. Anybody who wants to be on the presidential ballot needs to get some threshold number/proportion of votes in the primaries. The threshold is set such that there will be about 3 to 6 candidates.
* The presidential vote is done by preferential voting with a Condorcet voting system.
The big benefits:
The Condorcet voting will tend to elect compromise candidates, whereas the current primary system means you don't get to be a candidate unless you're extremist (at least for one of the main parties in the current climate.)
Because of preferential voting, each side of politics can put up more than one candidate without fear of losing by 'splitting the vote'.
More choice, without bloating the ballot unmanageably.
All candidates on the ballot have legitimacy through the primary system, so (hopefully) presidential candidate debates won't ignore the 'minor' candidates.
It allows for candidates to differ on more axes than just left vs right.
No more electoral college. Everyone's vote counts the same, whatever state they are in.
However, I am not a US citizen or resident.
It takes billions (not millions) of years for hydrogen atoms to fuse in the sun - that is precisely why the sun has a billions-of-years lifetime. So in building a fusion reactor, we need many orders of magnitude higher reaction rates, and to achieve them at many orders of magnitude lower densities. One way of doing this is to have much higher temperatures. The solar core temperature is about 15 million degrees and TFA has 50 million degrees for this new result, and 80 million degrees for half a second at a European reactor. This sounds unimpressive, but the reaction rates are very sensitive to temperature - proportional to about T^8 as I recall, but I didn't quickly find an online reference for this. 75 million degrees would therefore give a boost of about 5^8 which is about 400,000.
In the sun, the first reaction in the chain (proton+proton->deuterium) is the rate limiting step. In a reactor, we can provide deuterium enriched fuel and bypass this step. I don't know what the reaction rates are, but I suspect that this will be a greater benefit that the higher temperatures. You can do even better with tritium in the fuel, but your reactor becomes an intense neutron source, leading to induced radioactivity in nearby materials. Some proposed designs use these neutrons to breed more tritium from a lithium blanket around the reactor. (Once I get beyond the proton-proton chain reaction, I'm just relying on pop-science knowledge, so corrections from the more knowledgeable are welcome.)
Stars a bit more massive than the sun burn hydrogen via the CNO cycle, which has even higher temperature dependence (from memory, about T^17). I've never heard of anyone suggesting using the CNO cycle in a fusion reactor - presumably there are good reasons, but I don't know what they are. One problem is you need to wait for radioactive decays, but these have half-lives on the order of 1 to 2 minutes, and a commercial reactor would be running for much longer than that.
Poll 1: Which nation/organization do you think will be next to land people on the moon?
* China (CNSA)
* USA (NASA)
* Japan (JAXA)
* Europe (ESA)
* India (ISRO)
* Russia (RFSA)
* North Korea (KCST)
* Privately funded (e.g. SpaceX, Blue Origin or Cowboy Neal without direct state support) (ETLA)
Poll 2: Which nation/organization do you want be next to land people on the moon?
(same options)
NASA discovers little green men on the moon. NASA makes a 2 page press release. Bob writes a blog post where he condenses the NASA press release to 1 page, mostly by deleting every second paragraph. (Alternatively it could be a Javascript and advertising heavy commercial news site.) Slashdot posts an article linking to Bob's blog, rather than linking directly to NASA as they should. One of the first comments provides the direct link (with title something like "This is the link you should be using") and instantaneously gets modded to +5, in reward for having done what the Slashdot editor should have done.
I'm not saying never use secondary sources - sometimes Bob has summarized 50 pages to 1 page (and done a good job of it), or added some insightful commentary. Just don't use secondary sources unless they add significant value, and always include a link to the primary source in the summary.
Thanks.
It sounds like this system relies critically on the coefficient of friction between the slider grommets and the risers. Too high, and the slider never (or incompletely) slides and the chute does not fully inflate. Too low, and it inflates too fast and soon, bruising or breaking the parachutist or, worse, ripping the chute.
From the abruptness of the transition between slightly inflated and fully inflated in the space capsule chutes, and the prolonged delay before this occurs, I suspect the friction method you describe is not used. However a slider with some other release mechanism seems likely.
I think he has a plan for this, where he gets several years of free accommodation in a guarded and fortified building all at state expense. I think they call it a "safe house" or a "big house" or something like that.
There is a thing that these chutes do, where on initial deployment the open aperture of the chute is quite small, and the chute looks rather like a sausage. Then later on, the chute abruptly opens fully, and looks like a hemisphere. (The transition wasn't shown in the video in TFA, but I've seen it elsewhere and it is also simulated in Kerbal Space Program.)
How is this achieved? Is it some clever aerodynamics where the chute has two stable configurations and a 'catastrophic' transition? Is there some rope which constrains the aperture early on and then is somehow severed to allow fully deployment?
(I understand why - the first configuration slows the payload sufficiently so that the chute is not torn apart when it fully deploys. "How" is what I don't know.)
SpaceX love fourfold symmetry: octagonal layout of stage 1 rockets (plus one central, for 9 total). Four landing legs. Four steering fins at the top of stage I. Four pairs of "super Draco" landing/abort rockets on the Dragon. And now, four chutes.
However, statistical evidence is just an aggregation of anecdotal evidence.
No, sorry, completely wrong.
Statistical data comes from a well defined sample which is designed to be representative of an entire population. Anecdotes have no well defined selection criteria (my grandmother smoked until she was 100, and because I don't want to believe smoking is harmful, I remember and put great importance on this, and forget all the other people I have a connection to who were damaged by smoking) or (often where the selection criterion is 'stuff that happened to me') too little data to draw a conclusion (I've never crashed while driving drunk, so it must be safe.)
"I remember really hot days 10 years ago, hotter than now" holds very little weight. It is your experience (perhaps for every person like you there are 100 with the opposite experience), it is subject to biases of memory, and you've chosen the example retroactively to support a given position. The statistical data is thousands of thermometers measuring temperatures every hour over decades.
The average global temperature hasn't risen since 2015!
I just wanted to be the first person to make that argument. When this argument becomes popular in 2025, remember you saw it here first.
Thanks, that's great.
I wonder why SpaceX didn't start with this design?
You can't sail a drilling platform up to a wharf to unload the rocket, like you can a barge (so your idea would require an extra transfer at sea from platform to barge), nor is it so easy to move around the landing spot to match mission requirements. Having said all that, if barge landings turn out to be sufficiently haphazard, your idea may be economical.
People could animate Hamlet with a certain mouse as the protagonist (so long as it looks like 1930s Willy not 21st century Mickey.) They could distribute the Steam Boat Willy cartoon modified so that the mouse protagonist is naked and has oversized genitalia - just so long as they never call the mouse protagonist "Mickey". I think these are the sorts of possibilities that give Disney executives sleepless nights.
Historians write a (very dubious) history book. Novelist writes a novel in which this dubious history is true. Historians sue. Historians lose.
http://news.bbc.co.uk/2/hi/ent...
My analysis: You can't copyright facts. If you present something as a fact (such as in a history book), you lose any copyright over that "fact" (but not over your presentation of it.) Otherwise if you wrote a SF story involving Hawking radiation then Hawking could sue you.
This raises an interesting issue:
If I edit Anne Frank's diary, I have copyright on the edited version. If I carefully set things up and take a high quality photo of the Mona Lisa, I have copyright over that photo. If a monkey takes a selfie with my camera and then I do a bunch of post-processing to "improve" it and publish the improved picture, I have copyright due to the improvements.
In each case, somebody else could read the diaries and publish their own edition, take their own photo of the Mona Lisa, or freely distribute the original unimproved monkey selfie - but only if they have access to the diaries (or facsimile), to the Mona Lisa without plate glass in the way, or the unimproved selfie. When access to the original is restricted, reproductions can effectively exert copyright over the original when the original is out of copyright. (The monkey selfie camera owner missed this trick.)
I've thought for some time that we should have video games for this. Make a game in which the speed of light is (e.g.) 30m/s and make it relativistically correct. (I've seen a simple version: run around a village collecting tokens, the more you collect the slower the speed of light.) Make a game in which quantum effects happen on a macroscopic scale. (I'm not sure how this one would work.) If you can figure out how to make 4D space into a game, I'll be impressed.
In any case, the hope is that with many childhood hours of playing such games, relativistic and quantum effects will become intuitive, and therefore as easy to learn as Newtonian mechanics.
Here is a stunning example of how bad the USA news cycle can be.
This story would be the night 19 August, 1991. I was a graduate student living not too far from New York. The previous day, I'd heard ominous indications of a coup in Russia, probably trying to return to Soviet style government. Having been out of touch with news media for about 24 hours ("graduate student", remember?) I felt the need for an update, so I tuned my radio to a New York city "24 hour news" radio station.
After a full 30 minutes, they hadn't even mentioned it once. Then the announcer said "And now back to tonight's top story..."
"Finally!" I thought.
"... basements flooded in Long Island"
ARGH! I gave up. The world's second largest nuclear arsenal was potentially falling into the hands of hostile extremists, the Cold War could be restarting, and it didn't rate a mention compared to flooded basements.
Novel Distances for Dollo Data