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This link is earlier in this thread. Unruh came up with an interesting solution. Just thought I would post here for you Joigus. https://arxiv.org/pdf/1703.00543.pdf

For your specific mass extinction event you should read Micheal Benton's (professor of geology Bristol University) book https://www.amazon.co.uk/When-Life-Nearly-Died-Extinction/dp/0500291934 This details all 5 of the great mass extinctions of the past. But for the OP subject this is the book you want https://www.google.co.uk/search?ei=a5reXsPpE8qJ1fAP1MSXuAM&q=clive+oppenheimer+eruptions+that+shook+the+world&oq=oppenheimer+eruptions&gs_lcp=CgZwc3ktYWIQARgAMgYIABAWEB46BAgAEEc6BQgAEJECOgUIABCDAToFCAAQsQM6AggAOgQIABBDOgcIABCxAxBDOg0IABCxAxCRAhBGEPkBOgcIABCDARBDOgQIABAKOgQIABANOgYIABANEB5QzgxYwD9gxFBoAHABeAGAAeAEiAGKG5IBCzguNy40LjEuMC4xmAEAoAEBqgEHZ3dzLXdpeg&sclient=psy-ab Oppenheimer is reader in vulcanology University of Cambridge. He tabulates all the largest known eruptive events.

Nope the cosmological constant has no gravitational force or Coulomb force term. A force is a vector it has a magnitude and direction. The cosmological constant is a scalar quantity. It's value only has a magnitude. This is one critical detail you have to learn to seperate. The two types of fields will have different dynamics.

It is not simply a matter of "finding stuff that agrees"; it is a very succinct and reasoned summary of the flaws in the "erasing history" argument. Those accused of "erasing history" are the ones who want the history exposed and discussed. Those making the accusations wish they would just keep quiet about it; "Why can't they just remember the nice things that Mr Hitler did." So it is easy to be dismissive of a cliche that has no basis in reality (if one wants to be objective). And I don't think there is any reason to be dispassionate about this. Quite the reverse. You might be surprised.

Just saw this, as an excellent response the idiotic "erasing history" trope: https://twitter.com/malorynye/status/1269659045096501248

You seem to have a very specific approach to a very general issue. You want reminders, and it's "short-sighted and naive" to remove the statue of this one particular guy. And you don't want to add other statues. Why? What's so great about this particular statue? Is it more important to be reminded of this scofflaw over all others who do not have a statue? Shouldn't children be prompted to ask about other bad actors? The history we want to remember is the man and his acts, not the manufacture and erection of a statue. I understand a general desire to ensure we don't forget, but statues and monuments are usually reserved for those we wish to emulate. Not those we deem unworthy citizens.

https://www.google.com/search?q=confederate+monuments+site:scienceforums.net When these statues honor men who killed your grandfather or raped your grandmother, or who sent soldiers into battle to die so that people who look like you could continue being owned as property and without human rights or dignity... when those statues were put up as a direct response to increasing calls for equal and civil rights... a time when those calls for equality were met with dogs and hoses and state sanctioned viciousness in response... when the statues were used to remind you of your diminished place in society... to remind you that you’re “less than” those in power and lack any power or autonomy of your own... when you must relive that trauma every. single. day walking past those statues on your way to and from work, or to bring your child to school, to the grocery store... then the statues should be removed for the harm they cause. People can study history in books and these statues can and should be put into a museum. But... Putting up monuments to these symbols of oppression does little more than reinforce how the state agrees with those values we claim to have discarded... it implicitly sanctions the ideas that some of us are inferior or subhuman or less than due merely to the melanin content in our skin. Monuments are physical manifestations of what we value as a society and a culture. That’s why not. ✌️ Note: I’ve requested this conversation be split into its own thread.

Why not leave the statues in place and give them a new or additional plaque that reflects the present view of the person being commemorated? (eg "Notorious and wealthy Slave owner of the 18th century") I remember as a teenager being accommodated by a French family who took me to see the Arc de Triomphe in Paris where are listed all of Napolean's military victories in battle. Totally naively I looked for Waterloo and it was not there. I asked my hosts "Where is Waterloo?" with a very frosty response. I was later informed of my faux pas in as gentle a way as possible.

If I might 'steer' the OP in a slightly different direction... During the last great extinction, 65 Million years ago, the theory is that, there was much increased volcanic activity already poisoning the environment, and the meteor that hit Chicxulub, in the Yucatan peninsula, only hastened the ongoing extinction of dominant Dinosaurs. Could it have happened the other way around ? The meteor hits the Yucatan, and causes not only the devastation of tsunamis, fires, windstorms and global winters for years to come, but also increased volcanic activity for thousands of years to come. And that was the 'nail in the coffin' for Dinosaurs. IOW, do we have geological evidence of the volcanic activity/meteor timeline ?

I posted the 'play' because I don't know if you are asking because you know what entropy is and want to teach it or because you are studying it yourself? So the 'play' was a bit of a middle way. I guess from what you are saying that you are teaching it. Then the main point from the play was that you don't tell them everything at once. Just some basic but important part and let them get used to it before telling them more. In particular I don't know the level of maths available. It is easy to show that entropy is a state variable if they can do cyclic integrals. Otherwise you can just say "This is a state variable and we will come to how and why later" or you could discuss it in the context of the difference between reversible and irreversible changes. You could also note there are many more derived quantities such as Free energy, Chemical Potential and so on depending upon which subject you are teaching it in. You do not need the Second Law - although that came first for historical reasons. If you come to the second law before meeting entropy then the law can be nothing more than a definition for you. Not a Law at all. Here is an Engineering introduction along these lines.

OK so studying Thermodynamics is like watching a good play, film or reading a good book. The actors are introduced and a lttle bit of information is given about them. Enough to know who they are some of their relationship to the other actors and why the audience should be interested in them. As the play unfolds more information is revealed. In the same way, in Thermodynamics we first learn about the main quantities, their relationship to the other main quantities and why we might be interested in them. Now sonmeone who is just starting Thermodynamics is at the beginning of the play. He has learned about Boyle's Law P1V1 = P2 V2 (1662) Charles Law V1T2 =V2T1 (1780) Avogadros Gas Law PV = nRT (1812) Something about energy (Young 1802) Something about 'work' as the force times distance Something about 'heat' being mass times specific heat So he is in the same position of scientists in the first half of the 19th century that is 50 years before the first version of the First Law of Thermodynamics. So to get to the First Law some study needs to be carried out filling in the gaps and strengthening the definitions of these variables. Additionally he will need to learn some of the structure of Thermodynamics. In particular what is a system and what is a process and what is a state and a state variable. Once these ideas have been absorbed (they are all important) additional details can be studied and understood. Such the meaning of isolated, open, closed and flow systems. The difference between reversible and irreversible processes The difference between intensive and extensive variables and so on. So our student learns about different types of energy, including something called internal energy (symbol here U) and arrives at the First Law This connects the State Variable: Internal Energy to two variables heat and work. These are not system properties but variables that connect the system to its surroundings. U2 - U1 = q + w But he notices that whilst q and w can easily be measured or directly calculated from measurable variables , U cannot be directly measured. Furthermore the other state variables already mentioned P, V and T can also be easily measured and the equations stated allow calculation of w. So Internal Energy is the first quantity he has come across that he cannot directly measure. However he realises that it is a very important quantity since it is like a bank balance which = money in - money out. This was so important to early engineers in the development of steam engines that they invented a special diagram called an indicator diagram to show the work part - w. This work is the area under a P - V graph or plot And they even invented a mechanism to fix to steam engines called an 'indicator', which is where the name came from. Now you will have noticed by now that there are three measurable connected variables, P, V and T and that we have only used one of them. So guess what? Someone said, "Wouldn't it be nice if we had another variable we could plot against temperature (the unused variable) to calculate q in the same way ?" Bingo there you have it Entropy as Clausius named it. I have drawn the indicator diagram for Temperature v Entropy side by side with the one for Pressure v Volume so you it can be seen that they have the same format. Entropy is not some mystical property. It is simply the thing we need to multiply temperature by to get a particular energy in this case the heat exchanged across the system boundary. Again we cannot directly measure entropy, but simple equations exist to calculate it from easily measurable ones. Now that we are not frightened of it we can study more details and proceed to the next level of the development of Thermodynamics. Also if there are any details in the foregoing that are unclear please ask.

And, even simpler, in the case of the Apollo missions, there is a point where the gravitational force of the Moon exceeds that of the Earth and the craft starts falling towards the Moon (and similarly for the return journey, falling back to Earth).

erased : I haven't enought think

Universal time frames have cyclical effect Light like all electromagnetic waves can be defined mathematically as sine, cosine on a graph. These trigonometric functions serve as circular functions in relation to the degrees of angles. The wave of a sine function for instance may move forward in one direction on a graph but actually it is the definition of motion in a circle where points return to the point of origin. This is a holographic universe that involves holographic light projected through time frames of events. Since light waves have a cyclical effect so will the effects of the universal holographic time frames. The universal time frames will reverse order back to the point of origin as an opposite and equal reaction enforced by a scientifically proven God. This circular effect is evident in the perceived yin yang circle concept where there is a conversion of opposite qualities as a reverse order.