Did Eating Meat Help Our Brains Evolve?

[Si14]

Hi everyone:

Have you ever heard anything about the effects of the microwave on body?

..

 

[Pythagorean]

I don't know about the food; I trust it in general, but I can tell you something about frustrated total internal reflection:

Under "ordinary conditions" it is true that the creation of an evanescent wave does not affect the conservation of energy, i.e. the evanescent wave transmits zero net energy. However, if a third medium with a higher refractive index than the second medium is placed within less than several wavelengths distance from the interface between the first medium and the second medium, the evanescent wave will be different from the one under "ordinary conditions" and it will pass energy across the second into the third medium.

When teaching us about frustrated total internal refraction, my optics teacher stated that he never got his face close to the microwave to check his food while it was running anymore.

 

[Moonbear]

Hi everyone:

Have you ever heard anything about the effects of the microwave on body?

..

Yeah, it's bad to microwave your body. Did you have a more specific question? Are you asking about eating the foods cooked in a microwave, or the shielding on microwave ovens, or something else entirely?

 

[Si14]

I don't know about the food; I trust it in general, but I can tell you something about frustrated total internal reflection:



When teaching us about frustrated total internal refraction, my optics teacher stated that he never got his face close to the microwave to check his food while it was running anymore.

Thank you. but I didn't understand, what does it mean by 1st, 2nd and 3rd medium? Is the 3rd medium food? and the 2nd medium air? and 1st is the medium where microwave generated?
Am I correct?

Yeah, it's bad to microwave your body. Did you have a more specific question? Are you asking about eating the foods cooked in a microwave, or the shielding on microwave ovens, or something else entirely?

Thank you. Of course they have some standards for radiation dosage emitted from microwave ovens. And they can test them simply by measuring the radiation and power around and far away from ovens, BUT, how about the food which is prepared by this method? I think I read some where that some Russian groups are working on the effects of microwave cooked foods on body? Have you heard about that?

 

[D H]

Of course they have some standards for radiation dosage emitted from microwave ovens.

Of course they don't, because microwave ovens do not emit *any* ionizing radiation.

 

[Si14]

Of course they don't, because microwave ovens do not emit *any* ionizing radiation.

wait a minute, as far as I know, these ovens are working with high frequency waves. at those frequencies, if you stand near them, they will penetrate to your body and damage your tissues. but they damp in the air, so standing far away form them can reduce this damage. in ovens, they shield the device, that means it will absorb the waves and keeps them inside. so it minimizes the radiation dose outside the shield. But what is Ionizing radiation? you mean after bombarding the food by these waves, they will be ionized (for example hydrogen or carbon) and will radiate also?

 

[D H]

wait a minute, as far as I know, these ovens are working with high frequency waves. ... so it minimizes the radiation dose outside the shield. But what is Ionizing radiation? you mean after bombarding the food by these waves, they will be ionized (for example hydrogen or carbon) and will radiate also?

Your use of words such as "high frequency waves" and "radiation dose" makes me think that you are thinking of things like x-rays and gammas given off by radioactive elements such as uranium, radium, etc. That is not what goes on in a microwave oven. The electromagnetic radiation in a microwave is of a much lower frequency than the electromagnetic radiation that comes out of the light bulbs in your house. It is a very low frequency compared to the radiation you are familiar with. It is an extremely low frequency compared to the damaging ionizing radiation associated with radioactive elements. The only ones who think of microwave frequencies as being high frequencies are radio wavelength physicists and engineers.

The problem with microwaves isn't that they are radioactive. The problem is that the very feature that makes microwaves able to cook foods placed inside the oven makes microwaves able to heat things up outside the oven if the oven is not properly shielded.

 

[Pythagorean]

Thank you. but I didn't understand, what does it mean by 1st, 2nd and 3rd medium? Is the 3rd medium food? and the 2nd medium air? and 1st is the medium where microwave generated?
Am I correct?

I was referring to when you get your face close to an operating microwave. There's a glass wall between you and the microwaves, so we normally assume total internal reflection: that is, the microwaves are bouncing around inside the microwave, and staying inside there.

BUT, frustrated total internal reflection happens when you get your face close to the microwave. The waves will transmit through the 2nd medium (the air) to the third medium (your face) because the distance between your face and the microwave is on the order of microwaves (meters to millimeters). I don't know if enough power actually makes it through to be concerned about, but I don't NEED to put my face there, so I won't test it, personally.

 

[waht]

The only ones who think of microwave frequencies as being high frequencies are radio wavelength physicists and engineers.

Yes that's true. Microwaves are not ionizing - the standard designation does not reflect the whole electromagnetic spectrum.

http://img405.imageshack.us/img405/6813/rfband2.jpg

 

[Pythagorean]

Yes that's true. Microwaves are not ionizing - the standard designation does not reflect the whole electromagnetic spectrum.

http://img405.imageshack.us/img405/6813/rfband2.jpg

hey, what is voice frequency doing in there? Isn't voice frequency a pressure wave?

 

[chroot]

I was referring to when you get your face close to an operating microwave. There's a glass wall between you and the microwaves, so we normally assume total internal reflection: that is, the microwaves are bouncing around inside the microwave, and staying inside there.

I believe you are spreading misinformation. Your thoughts on FTIR are accurate, but you are applying the concept indiscriminately. The glass is wholly irrelevant to the propagation of the microwaves, or the safety of the people who use the oven.

The microwave door includes a fine mesh of metal, behind the glass. The holes in the mesh are large enough for you to be able to see your food (high-frequency visible photons pass right through the holes), but too small for the low-frequency microwave photons to escape. The microwaves have wavelengths on the order of 12 centimeters, and the holes are much, much smaller. The mesh is essentially a solid piece of metal, as far as the 12 cm radiation is concerned. The oven cavity is completed contained by this conductive metal, forming a Faraday cage. As you are aware, conductors block EM radiation.

You don't need to guess how much energy escapes microwaves -- it's easily measurable, and is certainly measured by the engineers who design it and qualify it.

Your microwave oven is not unsafe, even if you put your face near it. Relax.

- Warren

 

[Si14]

D H and others:
Thank you for your time. Helpful answers.

The only ones who think of microwave frequencies as being high frequencies are radio wavelength physicists and engineers.
.

This is applied to me. I am electrical eng. )

The electromagnetic radiation in a microwave is of a much lower frequency than the electromagnetic radiation that comes out of the light bulbs in your house.

exactly!

The problem with microwaves isn't that they are radioactive. The problem is that the very feature that makes microwaves able to cook foods placed inside the oven makes microwaves able to heat things up outside the oven if the oven is not properly shielded.

That's what I meant. and I think that they can make good shields for that. Since it looks simple, for shielding each frequency (at microwave ovens, I think they are around 2.5GHz), a good absorber needs to be fabricated.

The problem is with the high power at this frequency, I assume.

But my question is about the FOOD which is cooked with microwave oven.

Do you know what happens to them?

 

[Si14]

Thank you chroot and Pythagorean:

The oven cavity is completed contained by this conductive metal, forming a Faraday cage. As you are aware, conductors block EM radiation.

So, can we have evanescence waves (as Pythagorean mentioned)inside a metallic cavity? I mean there's no loss inside the cavity and if we assume that the cavity is designed for the operating frequency of the power generator (like a resonating cage), there should be a standing wave. Right?

 

[Pythagorean]

I believe you are spreading misinformation. Your thoughts on FTIR are accurate, but you are applying the concept indiscriminately. The glass is wholly irrelevant to the propagation of the microwaves, or the safety of the people who use the oven.

The microwave door includes a fine mesh of metal, behind the glass. The holes in the mesh are large enough for you to be able to see your food (high-frequency visible photons pass right through the holes), but too small for the low-frequency microwave photons to escape. The microwaves have wavelengths on the order of 12 centimeters, and the holes are much, much smaller. The mesh is essentially a solid piece of metal, as far as the 12 cm radiation is concerned. The oven cavity is completed contained by this conductive metal, forming a Faraday cage. As you are aware, conductors block EM radiation.

You don't need to guess how much energy escapes microwaves -- it's easily measurable, and is certainly measured by the engineers who design it and qualify it.

Your microwave oven is not unsafe, even if you put your face near it. Relax.

- Warren

So FTIR doesn't apply to conducting surfaces (remembering that they're not perfect conductors so there's some penetration depth)? It was my optics professor who brought up the concern, but he's a physicist, not an engineer.

You're right though, I've never seen a microwave without the mesh on the glass; I should have considered that.

 

[Pythagorean]

also, I do have a microwave meter, and i DO pickup over 1mw/cm^2 (the needle tops out) into the front of the meter. But I haven't measured area of the front of the box. It's roughly 4x6 cm^2. This has been true for all three of the microwaves (~10 year old models) that I've measured it on.

I don't know if that's significant with regards to biology. The device I used was the TriField Meter: http://www.trifield.com/EMF_meter.htm

Also, I don't trust manufacturer claims, as I've been taught not to in my engineering courses (especially considering the economics of LEDs), so this:

You don't need to guess how much energy escapes microwaves -- it's easily measurable, and is certainly measured by the engineers who design it and qualify it.

isn't satisfying to me. But then, on the same token, I don't know how trustworthy my TriField meter is.

 

[Moonbear]

But my question is about the FOOD which is cooked with microwave oven.

Do you know what happens to them?

It gets cooked. It's fine to eat, if that's your question. Once the microwave oven is turned off, there is no more emission of the microwaves. It's not like a radioactive isotope that would contaminate something and linger.

The only potential issue is whether some foods are exposed to the microwaves long enough to kill bacteria with such a short cooking time.

 

[Si14]

It gets cooked. It's fine to eat, if that's your question. Once the microwave oven is turned off, there is no more emission of the microwaves. It's not like a radioactive isotope that would contaminate something and linger.

The only potential issue is whether some foods are exposed to the microwaves long enough to kill bacteria with such a short cooking time.

Thank you. I somehow got the answer.

 

[russ_watters]

...isn't satisfying to me. But then, on the same token, I don't know how trustworthy my TriField meter is.

Though I'm not sure of the mechanism for enforcement, they are required to be tested to meet government standards on leakage:

All new microwave ovens produced for sale in the United States must meet the Food and Drug Administration/Center for Devices and Radiological Health (FDA/CDRH) performance requirements in Title 21, CFR, Part 1030.10. This requirement states that new ovens may not leak microwave radiation in excess of 1 mW cm–2 at 5 cm from the oven surface. It also states that ovens, once placed into service, may not leak microwave radiation in excess of 5 mW cm–2 at 5 cm from the oven surface. The "Procedure for Field Testing Microwave Ovens" (HEW Publication (FDA) 77-8037) is the standard method for verifying that these oven performance criteria are met.

http://www.hps.org/hpspublications/articles/microwaveoven.html

 

[russ_watters]

It's not like a radioactive isotope that would contaminate something and linger.

Not that I want to create an additional fear, but this was the fear that people had about irradiation sterilization of food. Irradiated food is exposed to high energy radiation from a radioactive source. But it does not become/stay radioactive and eating irradiated food does not expose the consumer to that radiation. I have gotten the impression from past discussions that these fears/issues tend to bleed together.

http://en.wikipedia.org/wiki/Food_irradiation

 

[Pythagorean]

Not that I want to create an additional fear, but this was the fear that people had about irradiation sterilization of food. Irradiated food is exposed to high energy radiation from a radioactive source. But it does not become/stay radioactive and eating irradiated food does not expose the consumer to that radiation. I have gotten the impression from past discussions that these fears/issues tend to bleed together.

http://en.wikipedia.org/wiki/Food_irradiation

What kind of materials can store radiation, and then release it as radiation anyway?

 

[chroot]

What kind of materials can store radiation, and then release it as radiation anyway?

Depending upon what you mean by "radiation," the answer might be any material. If you bombard just about anything with protons or neutrons, it'll end up radioactive.

- Warren

 

[Pythagorean]

Depending upon what you mean by "radiation," the answer might be any material. If you bombard just about anything with protons or neutrons, it'll end up radioactive.

- Warren

I suppose I was referring to electromagnetic radiation, specifically microwaves in this case. Is there even a material that you could stick in the microwave oven and "charge up" and then it would release microwaves after it's taken out of the microwave oven?

 

[Moonbear]

Not that I want to create an additional fear, but this was the fear that people had about irradiation sterilization of food. Irradiated food is exposed to high energy radiation from a radioactive source. But it does not become/stay radioactive and eating irradiated food does not expose the consumer to that radiation. I have gotten the impression from past discussions that these fears/issues tend to bleed together.

http://en.wikipedia.org/wiki/Food_irradiation

Yes, they're generally the same question, because people simply don't understand enough about radiation vs. radioactive materials to know the difference. I thought we'd answered that question here before. It's a pretty common fear due to ignorance issue.

 

[chroot]

I suppose I was referring to electromagnetic radiation, specifically microwaves in this case. Is there even a material that you could stick in the microwave oven and "charge up" and then it would release microwaves after it's taken out of the microwave oven?

One could probably invent a device with an antenna and a battery that could do the job, but no ordinary, simple materials -- certainly not foods -- would do this.

- Warren

 

[Pythagorean]

thank you for your input, russ and chroot.

 

[Jasongreat]

What is the purpose of the shield in a microwave? Isnt it to keep the dangerous microwaves inside the oven? Since microwaves are not good for organic material outside the oven wouldn't it be not good to the organic material inside? Granted the organic matter outside is alive and the organic matter inside is dead and that could be the reason microwaves are dangerous to us but not to the food we are cooking, but I am not so sure. I am probably over reacting but I try not to use the microwave for anything if at all feasible.

 

[D H]

False analogy.

The heat of your oven or range is not all that great for living tissue, either. One of the key reasons we cook food is precisely because heat is not all that great for living tissue. That heat kills all of (or at least most of) those nasty microbes that grow on our food. Moonbear in post #16 did raise one issue regarding microwave ovens: The short cooking time might not be hostile enough to living tissue.

 

[mgb_phys]

Is there even a material that you could stick in the microwave oven and "charge up" and then it would release microwaves after it's taken out of the microwave oven?

Any material above absolute zero should manage to do that

 

[Jasongreat]

=D H;2432070]

The heat of your oven or range is not all that great for living tissue, either.

Agreed, however I haven't noticed a shield around my conventional oven to keep the microwave radiation in. I don't think that it is just about heat, but how that heat is made. I am probably wrong and over reacting like I said before, but when it comes to radiation I am very conservative, I try not to eat irradiated foods either.

One of the key reasons we cook food is precisely because heat is not all that great for living tissue. That heat kills all of (or at least most of) those nasty microbes that grow on our food.

I agree, but do we use heat because it is the best/only way or is it just the the easiest way? When governments started to mandate cooking milk to kill the microbes it was far easier and less expensive than making the dairies clean up, atleast from what I've read on that subject. Or the fact that it is pretty much impossible to order a hamburger less than well done, we can get away with a far dirtier food supply if we just accept the fact that everything needs to be cooked until it has been killed twice. Like today it is far easier to irradiate food than to clean up the food supply. I could be wrong and am probably so, but it only takes a little longer and the food tastes better when cooked conventionally imo, so I will continue not cooking in the microwave.

Moonbear in post #16 did raise one issue regarding microwave ovens: The short cooking time might not be hostile enough to living tissue.

Isnt it the heat value that kills microbes and not the length of time? On cooking shows they say you need to cook to a certain temp, not that you need to hold at that temp for a certain amount of time. Moonbear is far smarter than me though so I will accept that opinion and I have one more reason not to use a microwave.

 

[mgb_phys]

but when it comes to radiation I am very conservative, I try not to eat irradiated foods either.

Microwave radiation is only radiation in the electro-magnetic sense, your regular stove uses infrared radiation, a light bulb uses visible radiation

but do we use heat because it is the best/only way or is it just the the easiest way?

It also breaks down tissue to make it easier to eat - it's a lot easier to eat chicken casserole than raw chicken.

When governments started to mandate cooking milk to kill the microbes it was far easier and less expensive than making the dairies clean up,...impossible to order a hamburger less than well done, we can get away with a far dirtier food supply

Sometimes the bacteria are in the source however clean the processing. Milk inside the cow can contain dangerous bacteria. You can get a variety of diseases straight form the teat, just as you could 100 years ago.
Pasteurizing is a cheap and easy way of partially cleaning milk - at least enough for it to be safe for two weeks. If you want it to last longer you can heat it more to kill more bacteria but you destroy more milk proteins and end up with nasty sterilized milk.

You can eat (almost) raw steak because unless the animal is badly diseased there are no bacteria in the meat, there is only a risk of contmination on the surface. The problem with hamburger is that you take surface and mix it right through the meat. If you start with steak and mince it (in a clena kitchen) just before serving it's safe = steak tartare.

Isnt it the heat value that kills microbes and not the length of time? On cooking

It's the energy that the microbes absorbs - which is a combination of heat and time. The danger of a microwave is that the food might not have time to heat up fully all the way through and so the centre might not get hot enough for long enough to kill the microbe.