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Showing content with the highest reputation on 01/07/21 in all areas

  1. 3 points
    ! Moderator Note I have split the increasingly off-topic discussion into a new thread. I apologize for taking matters into my own hands but there are few mods available and most have taken part in this thread.
  2. 2 points
    Because there is a general principle in nature that says that all systems will always tend towards that state which represents the lowest energy level, and/or the most stable configuration (in technical terms, the “least action”). This is called the principle of least action, and it is a formal mathematical statement that underlies both the macroscopic world (GR) and the microscopic realm (quantum field theory). The principle of extremal ageing is just a special case of this. In the case of test particles under the influence of gravity, the resulting world lines are the simplest possible ones (so it isn’t “elaborate”) - they are geodesics of spacetime, i.e. world lines where proper acceleration vanishes at every point (hence “free fall”), or equivalently the “straightest possible” world lines. Because it is mathematically inconsistent. The object that describes the curvature of spacetime, and hence gravity, the Riemann curvature tensor, can be thought of as “made up of” two parts - its trace-free part, the Weyl curvature tensor (which roughly speaking encodes tidal effects, i.e. distortions in shape of a test volume in free fall); and its trace, the Ricci tensor (which encodes the volume itself). If you have only 3 spatial dimensions, the Weyl tensor identically vanishes (a basic result in differential geometry, which can be straightforwardly proven), so there’s no tidal gravity. In fact, since in vacuum the Ricci tensor vanishes as well due to the Einstein field equations, you would have no gravity at all in the exterior of massive bodies - which is clearly not consistent with what we observe. So the universe cannot have only three spatial dimensions, since this is logically at odds with what we see in the world around us. I can easily formalise this argument mathematically, but I think you understand what I am trying to point out, so there shouldn’t be any need. Nice one 😄
  3. 2 points
    One thing that has become apparent after watching the Capital be over run by insurgents seeking to tear down our government is that across this great land a great many towns and villages are missing their Idiots...
  4. 1 point
    Absolutely, I know a couple of researchers, some really excellent ones that basically were temps until their retirement (or close to). The system is not really good if things like predictive career planning, high income, job security early on, work-life balance are important to you. Eh, I made myself sad now.
  5. 1 point
    swansont said much of what I was going to say, but I think the question was a good one and deserves encouragement so +1. Firstly no nuclear reaction produces or generates electricity. So by themselves nuclear reactors (ie plant and equipment where controlled nuclear reactions take place) need further plant and machinery to generate the electricity. Nuclear reactions generate heat (and fission products of course) - lots of it. So much of it that much is wasted. However this released heat is used to heat coolants by a series of heat exchangers to drive turbines that drive the generators. But the reactor is designed to run 'up slowly'. In theory it may be run down very quickly for emergency purposes by moderators. The issue then becomes how to use the spare heat to meet a sudden increase in demand. One way is to have standby generators that can be brought online very quickly. These would be needed in any case for maintenance purposes. Another way would be to divert more steam to driving turbines, but that would mean they were working at less than full capacity before. Another way would be electricity or heat storage, neither being very practical in marine environments, though a buffer of either could help overcome a short term increase in demand. Electricity storage would be better for this. In any event the whole power plant comprises more than just the nuclear reactor.
  6. 1 point
    As an external observer (I live in Ireland) who isn’t usually interested in politics, I have to say even I am absolutely gobsmacked at what has happened here. A direct attack on the democratic foundations of a once great country, and in my mind it very nearly qualifies as a coup attempt. It’s just scary, and I do not understand how he isn’t being removed immediately. I feel very sorry for the vast majority of decent American people - no single person has ever done as much damage to both the country’s democratic institutions, as well as its international reputation, as Trump has. It will take a generation to recover from this. At least I am relieved to see that the democratic process still seem to function, as the elections results have just been ratified as I am typing this.
  7. 1 point
    Not sure what the videos says, but mutation in the gene for the spike protein are concerning. No conclusive evidence either way, yet.
  8. 1 point
    How, then, does a nuclear powered aircraft carrier go from all stop to full speed ahead in a short period of time?
  9. 1 point
    Sure, he called out the protesters, and threatened prosecution, but he always adds "even though we won the election … by a landslide … and we were robbed". The 'beacon' of Democracy, once a symbol around the world, has been turned into the 'laughing stock', of the world by D Trump, and his useful idiots. Last time we saw shit like this was the 20s, when B Mussolini marched on Rome to take power by fascist intimidation and violence, or the street battles and violence by Hitler's Nazi party, that eventually saw the end of the Weimar Republic, and forced von Hindenburg to appoint him Chancellor. I would be willing to bet, both Mexico, and Canada, will pay for their own border walls now.
  10. 1 point
    I looked for a rats off ship image and came upon this...it's about a year and a half old but might fit better today.
  11. 1 point
    The worst part is that Trump is succesfuly building his equity this very moment of becoming a martyr. Things are not well, when America coughs many others can catch a cold.
  12. 1 point
    It's not elaborate. There are principle like this that are simple ways of summarizing how particles behave under a set of conditions. Light and the principle of least time (Fermat's principle), which is a truth about the path light will take, without discussing the particulars of indices of refraction. Related to the principle of least action for mechanics. Don't anthropomorphize the particles. They hate that.
  13. 1 point
  14. 1 point
    For anyone who's been paying attention, the notion that Trump will voluntarily concede the election (even if he has been legitimately and resoundingly defeated) is undoubtedly not based in reality. Trump is not the type of person to graciously bow out. Trump will use any and all means at his disposal to retain power, and has already laid the groundwork via the bully pulpit to deny the authenticity of the election results: through his constant efforts in the media to undermine the legitimacy of mail in voting, the Republican efforts to limit access to in person voting, and their attempts to get mail in ballots thrown out on fabricated technicalities by the courts. Trump will not go quietly into that good night. If there's anything we should have learned about Trump, what he says, he means. "I think it's a terrible thing when ballots can be collected after an election. I think it's a terrible thing when states are allowed to tabulate ballots for a long period of time after the election is over." - Donald Trump https://www.axios.com/trump-claim-election-victory-ballots-97eb12b9-5e35-402f-9ea3-0ccfb47f613f.html Trump does not want every vote counted. Nothing could be more antithetical to democracy. Trump wants the superficial appearance of a victory and a nullification of the democratic process writ large to continue his exercise in selfish aggrandizement at the expense of the American people. Now, Van Jones has released a remarkable Ted talk that is both terrifying and accurate, describing in detail how Trump could simple refuse to concede (for whatever reason) and the entire democratic process would be wrested from the hands of the people. "For instance, did you know that under our constitution a presidential candidate could actually lose the popular vote, fail to get a majority in the electoral college, refuse to concede, manipulate hidden mechanisms in our government and still get sworn in as the president of the United States of America? That's a true fact. I know it sounds like some crazy "House of Cards" episode, and I wish it was, because then we could just change the channel, but I just described to you a real-world, real-life possibility that could occur this year, the year I'm talking, in 2020, or in some other year, if we don't fix some of these glitches in our system." - Van Jones This will not be business as usual...
  15. 1 point
    ! Moderator Note Dear students, A simple reminder to all: this is the "Homework Help" forum, not the "Homework Answers" forum. We will not do your work for you, only point you in the right direction. Posts that do give the answers may be removed. Best regards, Scienceforums.net Staff p.s. Yes, this is the same text as at the top of the Homework Help forum.
  16. -1 points
    You have zero arguments, pal. You can only threaten, it is the only thing left to you.
  17. -2 points
    I like Feynman because he tries to make nature understandable, but that inevitably leads to errors which books that merely quote equations avoid. If your time was valuable you would not be on here sneering. I only read the thread today since my last post, because I had other things to do with my valuable time. Actually people posting on here should enjoy my book, because just about everything they have said, is said by a character in my book. Interesting that you started as my harshest critic, but are apparently now the only person interested. You posted my blog several days ago, but according to Wordpress I have had only 1 visitor. The point is that special relativity is based on the 3 Lorentz transformations, that is all that is needed for the principle of relativity to hold. You can easily derive the E² equation from the Einstein??? mass dilation formula, but only if you start off by assuming E=MC². However why go out of your way to make things more complicated? The thread is about to be closed, but it is boring anyway because I pretty much know what people are going to say before they say it. But anybody can always contact me via my blog.
  18. -2 points
    Look at this figure from Wikipedia's article "Electric charge": The arrows at the Plus charge point away from it, whereas at the Minus charge toward it. Is this arbitrary, a convention? Can we change the "convention" and adopt this "convention": We can do it neither now nor ever. Do you know why? Because Plus means an effect or force toward outside and Minus means an effect or force toward inside. And exactly the presented figure from Wikipedia you can see when you turn the Wimshurst generator in the dark. Find a Wimshurst generator, see the described phenomenon and then tell me, which side would you call Plus and which Minus? The electricity, where the light flicker is toward outside, is the same as the vitreous electricity, while the electricity, where the light flicker is toward inside, is the same as the resinous electricity. It is very easily provable ( I can explain how, if you are interested). The carbon rod in a carbon-zinc battery has the same polarity as the vitreous electricity, while the zinc jar has the same polarity as the resinous electricity (it is also very easily provable). The electricity flows from the carbon terminal toward zinc terminal through the outer conductive path. That is the truth. I will keep posting the TRUTH and you can do nothing about it. Do you know why? Because the truth is stronger than anything.
  19. -2 points
    This alternative interpretation is evidenced by the same evidence that substantiates Time Dilation in SR.
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