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You misunderstood. You are thinking about dust-in-dirt passing physics. That is NOT the entire process. That's the very end of the process. Maybe you are not

You misunderstood. You are thinking about dust-in-dirt passing physics. That is NOT the entire process. That's the very end of the process. Maybe you are not familiar with this use of the phrase? Elon Musk uses the “it must pass physics” phrase to basically mean that the ENTIRE THING has to obey the laws of nature, not just the last step. Perhaps this example can clarify the concept: Using electrolysis to extract hydrogen from water is, to use your phrase "a known quantity and doesn't need to be repeated for every new study in the field". In other words, that process is real and "passes physics". If, on the other hand, we propose to use electrolysis to generate liquid hydrogen to use as fuel, the ENTIRE PROCESS has to pass physics. It does not. Why? Well, it takes approximately 55 kWh of electrical energy to extract 1 kg of gaseous hydrogen from water. Great. However, 1 kg of gaseous hydrogen contains 40 kWh of energy. In other words, you have to use MORE energy to extract the hydrogen than the energy it contains. This idea, at the most basic level, does not pass the physics test. It's a fantasy. Once we add such things as the inefficiencies of generating the energy, energy transportation losses (wires, connections, transformers, etc.), the energy required to bring the water to the electrolysis plant and run it at scale, the energy required to liquify hydrogen (12 kWh per kilogram), the energy required to transport and manage liquid hydrogen, etc. Well. The entire story quickly becomes a ridiculous fantasy. You are going to expend more than 100 to 200 kWh per kg of gas to deliver 40 kWh of stored energy in liquid form. That's what "does not pass physics" means. The entire process cannot stand up to scrutiny when all factors are considered. So, all of this, and the steps I have not listed (for example, fuel delivery), have to pass physics as a complete proposal: - Mine massive far-away lava fields - Likely use explosives, strip mining and very large machinery - Burn large amounts of diesel and other fuels - Generate massive amounts of CO2 through this process - Cause serious environmental damage - Transport what you mined - Burn large amounts of diesel and other fuels - Generate massive amounts of CO2 through transportation - Crush it into a fine dust - Consuming very large amounts of energy - Generate massive amounts of CO2 through this process - Transport massive quantities again - Burn large amounts of diesel and other fuels - Generate massive amounts of CO2 again - Likely need for massive amounts of chemicals as part of all of the above - Use a high carbon footprint process to distribute the dust - Burn large amounts of diesel and other fuels - Use a high carbon footprint process to bury the dust to the required depth - Burn large amounts of diesel and other fuels - Hope and pray for enough rain - Hope and pray you don't destroy the fields for agricultural use - Etc. What I said is that phase 1 should be about proving that the entire thing passes physics. For that stage, it is OK assume that the proposed final element passes physics (whether we know it or not). What you are trying to quantify is everything else, which, in this case, is everything before a particle of volcanic dust finds itself 30 cm deep in dirt at a farm. That's what you have to prove before the physics of that dust particle in dirt is even remotely relevant in the context of the proposal.

philipkglass 3y ago
Using electrolysis to extract hydrogen from water is, to use your phrase "a known quantity and doesn't need to be repeated for every new study in the field". In other words, that process is real and "passes physics". If, on the other hand, we propose to use electrolysis to generate liquid hydrogen to use as fuel, the ENTIRE PROCESS has to pass physics. It does not. Why? Well, it takes approximately 55 kWh of electrical energy to extract 1 kg of gaseous hydrogen from water. Great. However, 1 kg of gaseous hydrogen contains 40 kWh of energy. In other words, you have to use MORE energy to extract the hydrogen than the energy it contains. This idea, at the most basic level, does not pass the physics test. It's a fantasy. If the creation of hydrogen fuel via water electrolysis is an example of something that "doesn't pass physics" then the idiom "doesn't pass physics" obscures more than it clarifies. There is nothing physically implausible about water electrolysis. Despite the energy losses, water electrolysis to produce hydrogen fuel may be better than the alternatives; for example, you can launch a rocket to orbit with hydrogen fuel but you can't do that with electricity. If "doesn't pass physics" is supposed to be shorthand for economic implausibility relative to alternatives, just make the economic argument instead of referring to physics.
- robomartin 3y ago
  > There is nothing physically implausible about water electrolysis. You are getting lost in the semantics and an example I grabbed as an illustration and ignoring the message, which is simple: Anyone can propose anything. And that's fantastic. No problem. However, at some point, it has to make sense. And it has to make sense while looking at the entire process, not just a small element of it. There are a lot of things in life that sound fantastic, until you run a full analysis and understand that they don't really make sense, particularly at scale. This has to be the first step. Beyond that, after that step, the project has to be compared to other proposals that can deliver similar or better results. This, again, can usually be done before launching into these projects. It's about that list of dependencies I posted in my other comment. Why? Because we are wasting valuable time and money on fantasies, that's why. Making a business comparison to try to further illustrate the point. In business you have to run through top level before jumping head-first into anything at scale. You also have to run competitive analysis and decide if your proposal is actually realizable and competitive. In my work in aerospace I have to do this all the time. We are used to conducting what's usually called "Trades Analysis". This is a document where you present and analyze, to a sufficient level, all reasonable options to solve the problem you are trying to address. This is the starting point for a discussion that usually leads to choosing the solution or approach that makes the most sense within the stated objectives and constraints. > If "doesn't pass physics" is supposed to be shorthand for economic implausibility relative to alternatives No. That's not it. It really is about everything else first and foremost. Before you consider economics you have to consider science. Again, for the entire process, not a small portion of it. Of course, there are cases where the economics is so obviously ridiculous that scientific analysis quickly becomes irrelevant. A ridiculous example would be something like mining materials from the moon to make common concrete on earth. We don't need to look at science to know that would be economically and ecologically ridiculous. > for example, you can launch a rocket to orbit with hydrogen fuel If you change the problem, you change the required analysis methodologies. Still, you have to look at the process in its entirety and in the context of comparisons to other ideas. That's why nobody launches rockets into orbit using hydrogen. It doesn't make sense when looked at from a macro perspective. My advice: Always take a very large step back. Try to understand and quantify the entire picture. Things have to make sense at the macro level.

philipkglass 3y ago

Using electrolysis to extract hydrogen from water is, to use your phrase "a known quantity and doesn't need to be repeated for every new study in the field". In other words, that process is real and "passes physics". If, on the other hand, we propose to use electrolysis to generate liquid hydrogen to use as fuel, the ENTIRE PROCESS has to pass physics. It does not. Why? Well, it takes approximately 55 kWh of electrical energy to extract 1 kg of gaseous hydrogen from water. Great. However, 1 kg of gaseous hydrogen contains 40 kWh of energy. In other words, you have to use MORE energy to extract the hydrogen than the energy it contains. This idea, at the most basic level, does not pass the physics test. It's a fantasy. If the creation of hydrogen fuel via water electrolysis is an example of something that "doesn't pass physics" then the idiom "doesn't pass physics" obscures more than it clarifies. There is nothing physically implausible about water electrolysis. Despite the energy losses, water electrolysis to produce hydrogen fuel may be better than the alternatives; for example, you can launch a rocket to orbit with hydrogen fuel but you can't do that with electricity. If "doesn't pass physics" is supposed to be shorthand for economic implausibility relative to alternatives, just make the economic argument instead of referring to physics.

robomartin 3y ago
> There is nothing physically implausible about water electrolysis. You are getting lost in the semantics and an example I grabbed as an illustration and ignoring the message, which is simple: Anyone can propose anything. And that's fantastic. No problem. However, at some point, it has to make sense. And it has to make sense while looking at the entire process, not just a small element of it. There are a lot of things in life that sound fantastic, until you run a full analysis and understand that they don't really make sense, particularly at scale. This has to be the first step. Beyond that, after that step, the project has to be compared to other proposals that can deliver similar or better results. This, again, can usually be done before launching into these projects. It's about that list of dependencies I posted in my other comment. Why? Because we are wasting valuable time and money on fantasies, that's why. Making a business comparison to try to further illustrate the point. In business you have to run through top level before jumping head-first into anything at scale. You also have to run competitive analysis and decide if your proposal is actually realizable and competitive. In my work in aerospace I have to do this all the time. We are used to conducting what's usually called "Trades Analysis". This is a document where you present and analyze, to a sufficient level, all reasonable options to solve the problem you are trying to address. This is the starting point for a discussion that usually leads to choosing the solution or approach that makes the most sense within the stated objectives and constraints. > If "doesn't pass physics" is supposed to be shorthand for economic implausibility relative to alternatives No. That's not it. It really is about everything else first and foremost. Before you consider economics you have to consider science. Again, for the entire process, not a small portion of it. Of course, there are cases where the economics is so obviously ridiculous that scientific analysis quickly becomes irrelevant. A ridiculous example would be something like mining materials from the moon to make common concrete on earth. We don't need to look at science to know that would be economically and ecologically ridiculous. > for example, you can launch a rocket to orbit with hydrogen fuel If you change the problem, you change the required analysis methodologies. Still, you have to look at the process in its entirety and in the context of comparisons to other ideas. That's why nobody launches rockets into orbit using hydrogen. It doesn't make sense when looked at from a macro perspective. My advice: Always take a very large step back. Try to understand and quantify the entire picture. Things have to make sense at the macro level.