ask a physicist

[Scott DeWar]

But then, I read the Silmarillion for fun, too.

there is a pill for that, you know. I now a few Psychiatrists to help you.

 

[Scott DeWar]

Re: post 95

I am going to have to re-read that a couple of times.

 

[Umbran]

Re: post 95

I am going to have to re-read that a couple of times.

Because it is dense, because it is hard to wrap your head around, or because I wasn't writing very well? I can try to fix the last, if that's the case.

 

[Scott DeWar]

Because it is dense, because it is hard to wrap your head around, or because I wasn't writing very well? I can try to fix the last, if that's the case.

it is dense. lots of new information for me to consider

*processing . . . . processing . . . . processing . . . . *

 

[Scott DeWar]

A new question: is this plausible? What makes it work??

https://www.youtube.com/watch?v=shkFDPI6kGE

 

[Morrus]

A new question: is this plausible? What makes it work??

The fact that the title of it seems to think it makes Obama quake in his bed is entertaining!

 

[Scott DeWar]

two different inks on a ceramic square. add a fuel source and it produces electricity. There is more to it, what would that be?

 

[freyar]

it is dense. lots of new information for me to consider

*processing . . . . processing . . . . processing . . . . *

There's also a shorter version of some of the same content in post 26.

Anyway, I was going to say something about string theory and the equivalence principle, that is, the idea that inertial mass and gravitational mass are the same. So, as has already been discussed, this is a feature of any theory where gravity is really just the geometry of spacetime. That includes general relativity, extensions of general relativity, and also string theory. String theory is interesting since you can start with strings moving on a flat spacetime, but you end up with (an extension of) general relativity (in more dimensions). In that sense, the equivalence principle is "derived."

But it is also possible to find many discussions of violations of the equivalence principle in string theory and elsewhere. The context is that you get a lot more than gravity in string theory and really in most other theories beyond the Standard Model of particle physics. These new types of particles can introduce new forces. If one of these forces interacts differently with, for example, protons than neutrons, then different elements will experience this force differently, so we might mistakenly think that gravity acts differently on different materials. This is sometimes called a "violation of the equivalence principle."

The problem I have with that wording is that no one says that electromagnetic forces violate the equivalence principle. Or the strong or weak nuclear forces. Or even the very short range Higgs force which also must exist. That's because these forces aren't gravity. Well, any other new force wouldn't be gravity either. But I think this is one of those cases where there's a phrase that gets stuck in usage, even though it isn't really appropriate. There are some others in physics I don't like much either.

 

[freyar]

A new question: is this plausible? What makes it work??

https://www.youtube.com/watch?v=shkFDPI6kGE

I believe I've found some news articles about this thing, and it just seems to be a fuel cell. You can kind of think of fuel cells as batteries that require, well, fuel. This is not really new technology, but I guess they claim to be able to make them smaller and cleaner. I can't say whether they have or not, of course --- part of how "clean" or "green" a fuel cell is depends on the fuel you give it --- but I don't think there's anything in principle that says they can't.

 

[Umbran]

A new question: is this plausible? What makes it work??

Yes, it is plausible. It is a fuel cell, and the basic idea dates back to 1838 - https://en.wikipedia.org/wiki/Fuel_cell

Now, when they say early in that video that there's no burning - that's technically inaccurate. The fuel cell takes some specific fuel, and combines it with oxygen to get energy. What do you think "combine fuel and oxygen" is? Oxidation, aka "burning". A fuel cell does it without an open flame, mediated by a catalyst on a substrate that takes a spare electron out of the process and feeds it into a wire.

Now, note something - you need fuel for this to work. In order to put one of those in your yard to power your house, you need it to be next to a fuel tank, or fed by a municipal fuel line, or something. So, yes, you can remove power lines and electrical distribution grids, but then you need to have fuel distribution instead. My house already gets natural gas, so I could install one of these in my basement. But for rural areas that don't have gas service? Carting around big bottles of flammable liquids to remote areas is not itself cheap, energy-wise.

Also note that whether the energy is "clean" depends on the fuel used. If you use pure hydrogen, then you get water and a bit of heat out - that's not bad, but pure hydrogen is actually pretty expensive. If you use a fossil hydrocarbon, you get CO2 out, which is not so good. If you use a biofuel (say, alcohol), then at least the carbon is coming from the biological carbon cycle - but typically you have to watch biofuels because their production processes are often not very clean.