How do scientists know what percent of our brains we use?

Originally posted by sonhouse
On the organic farming thing, someone told me veggies and such have something like only 1/3 of the nutrients of the same plants say, 50 years ago. Anyone hear this one?
With the forced growing and intensive fertilization today, I tend to believe it but has anyone else come across this? Urban myth or fact?

I'm not sure on the 1/3 number, but it seems plausible to me that because of selective breeding and genetic modification plants grow a lot faster, which makes them contain more water and less nutrients per unit of mass.

Originally posted by KazetNagorra
I'm not sure on the 1/3 number, but it seems plausible to me that because of selective breeding and genetic modification plants grow a lot faster, which makes them contain more water and less nutrients per unit of mass.

“...but it seems plausible to me that because of selective breeding and genetic modification plants ...”

since organic crops are also nearly always selectively breed plants and genetic modification plants (either by hybridisation or selectively breed not to mention the fact that ALL plants are genetically modified be evolution!) that would not be a reason why there could be a difference in nutrition between the two.

Also, it is a myth that there is a significant difference anyway:

http://www.food.gov.uk/foodindustry/farmingfood/organicfood/

“...The available evidence shows that the nutrient levels and the degree of variation are similar in food produced by both organic and conventional agriculture. ...”

and:

“...An independent systematic review of the available published literature has shown that there are no important differences in the nutrition content of, or any additional health benefits deriving from, organic food when compared with conventionally produced food. ...”

Originally posted by Andrew Hamilton
“...but it seems plausible to me that because of selective breeding and genetic modification plants ...”

since organic crops are also nearly always selectively breed plants and genetic modification plants (either by hybridisation or selectively breed not to mention the fact that ALL plants are genetically modified be evolution!) that would not be ...[text shortened]... ealth benefits deriving from, organic food when compared with conventionally produced food. ...”

No, you're getting me wrong, I'm not aiming at a difference between organic and non-organic, but at a difference between crops now and say, 100 years ago.

Originally posted by KazetNagorra
No, you're getting me wrong, I'm not aiming at a difference between organic and non-organic, but at a difference between crops now and say, 100 years ago.

Oh I see 🙂
My mistake.

Originally posted by KazetNagorra
I'm not sure on the 1/3 number, but it seems plausible to me that because of selective breeding and genetic modification plants grow a lot faster, which makes them contain more water and less nutrients per unit of mass.

This would apply also to how healthy the vegetables are when they get to market. Many vegetables loose water over time, so the longer they sit on the shelves the less water they contain.

Originally posted by KazetNagorra
Could you enlighten me as to why a deterministic quantum measurement is necessarily a hidden variable theory (you don't have to hold back on the mathematics if required)? It was my impression that quantum measurements were simply not well-understood and might be an emergent phenomenon from more fundamental quantum theory (i.e. interactions between few particles rather than a macroscopic interaction).

Assuming you accept Bell's Theorem then it's not mathematical. My argument depends on Bell's assumptions about "hidden variable theories", basically that they have to be consistent and preserve local reality (in other words the momentum and position are both always well defined). The hidden variable doesn't have to be hidden, it just has to determine the measurable variables. His inequality depends only on those two assumptions.

Essentially it is a mater of whether the outcome of a single experiment can be predicted in advance - in a hidden variable theory it can, provided you have knowledge of the hidden variable. Even if you know all the information available about a quantum system you still cannot predict the exact result of a single experiment. A theory of fundamental measurements which is deterministic has to have things like the position "existing" before the measurement is made, otherwise it wouldn't be deterministic. If the momentum or position don't exist before the measurement then it isn't a hidden variable theory, and is not deterministic. If the quantum measurement process is deterministic, then the outcome of an experiment "exists" before the measurement happens (in the same way that the point where a classical projectile hits the ground is known before the shell is fired) which means that the theory fulfills Bell's requirements for hidden variable theories.

What this means is that although the theory of quantum measurements doesn't really exist, we know that candidate theories must have the property that they do not violate Bell's inequality. Which basically means that they have to non-deterministic.

You've got a good point about quantum measurement. It's difficult to imagine an experimental apparatus capable of measuring either the position or the momentum of a particle. Spin and polarisation of light is easy as you can just use polaroid or deflect the particle in a magnetic field, and then detect the presence of the particle in a region which would be forbidden if it had the wrong spin (or polarisation). How exactly does one measure the position of a particle though? Is this the position just before, just after, or at the exact moment you bounced a photon off it? Also since the measurement involves a particle interaction, it's not clear which particle's position is being measured.

Originally posted by DeepThought
A theory of fundamental measurements which is deterministic has to have things like the position "existing" before the measurement is made, otherwise it wouldn't be deterministic.

Why is that? Going back to my particle in a well, this does not have a definite position, but its state can be predicted deterministically.

Originally posted by KazetNagorra
A common one is that the Earth revolves around the Sun, as opposed to the Sun revolving around the Earth. But since there is no center of the universe, nor an ether, it's inaccurate to say the Earth revolves around the Sun. Instead, they revolve around each other.

actually they both orbit around their common centre of mass.

Originally posted by googlefudge
actually they both orbit around their common centre of mass.

Ah, but isn't their common centre of mass inside the sun? AFAIR, it is.

Richard

Originally posted by Shallow Blue
Ah, but isn't their common centre of mass inside the sun? AFAIR, it is.

Richard

Yes, but not in the centre of the sun.