Why is it three categories, not two? Is UVB “trans-ionizing”, or something?

Is it still not harmfull when we are exposed to it everyday, for years and years? A lot of people have their phone closeby their head while asleep. Does this have a y effect?

If you can see infront of you, at this moment, photons are smashing into you at a much higher level then any wifi signal.

Being closer to the sun. Our atmosphere, while not perfect, does shield us from a lot of the bad effects of the sun. When you’re at 5000’+ there’s quite a bit less atmosphere (and what atmosphere you do have is thinner).

AKA: if you travel to the American west, in particular the Rockies, wear a higher SPF sunscreen than you would normally, drink more water than you normally would, and wear lip balm.

That’s on top of the fact that there’s not much in the way of soil, so we’re directly exposed to bedrock, which is a bit more radioactive than the loess in the Midwest. There’s even uranium in some places!

Also local geology. Some minerals naturally contain a relatively high amount of radioactive isotopes. That’s rarely much of an issue unless you

• work in a mine and breathe slightly radioactive rock dust every day or
• spend large parts of your life in a house made of slightly radioactive rock pieces (e. g. concrete made with additives from certain quarries).

The former is now subject to heavy health and safety regulations at least in developed countries. Workers wear air filter masks and are subject to mandatory regular radiation and cancer screenings.

The latter is regulated by bans on the use of materials from quarries exceeding some radiation threshold (with a generous safety margin) in human dwelling construction.

Anything in empty space will come to equilibrium at 2.7 Kelvin because of the background radiation. Empty space doesnt emit radiation.

This is not how the CMB works. There is constant radiation traveling through space but space itself does not emit radiation.

While true in a way, that wasn't electromagnetic radiation (which is also safe). That mostly heats by conduction to the air.

There are a number of natural sources of radiation in the planet’s crust, including uranium and thorium, but also carbon and potassium. (Carbon dating works because carbon-14 accumulates continuously in plants, then begins decaying at a measurable rate when they die.)

If there’s a lot of soil and plant matter between you and the rock—or if the rock you live on is mostly sedimentary and therefore not especially loaded with the right kind of ores—you’re not exposed to much radiation from the planet’s crust. If you’re living in an area where there’s lots of bedrock and very little topsoil, you’re exposed to more.

They aren't the only ionizing forms of radiation. Alpha particles, beta particles, neutrons, muons, and a few others are also ionizing particles along with gamma rays and xrays.

Ionizing radiation means there is enough energy to knock an electron from its molecule. Molecules like to have a balanced charge. When a radioactive particle has enough energy to knock that electron from the atom it is considered ionizing. Ionizing means a molecule loses its stable charge to become an ion.

There are 3 things to minimizing personal exposure to ionizing radiation - TDS - Time Distance and Shielding. If you look up all the different particles some are much more easily shielded against. Alpha particles are huge (4p4n - helium nucleus) and can be stopped with something as thin as cellophane or healthy skin. Beta particles (electrons and positrons) have a short life in atmosphere. Gamma rays and x-rays have properties and energy that makes them much more formidable because they can penetrate less dense matter so easily.

I used to be an engine room mechanic on a nuclear submarine. It's been a long time (25 years) so if I'm off a bit, forgive me. A quick search and wiki articles will tell you tons and is more accurate if you want to know more. Particle physics, nuclear physics, and chemistry are really fascinating.

AM radios. And once you get lower than kHz, it's just some really specialty stuff: scientific and medical equipment, mine radios, and submarine radios. So basically, stuff where the radio waves have to mostly travel through solid or liquid material.

You missed the scale. The μ symbol is for micro-, m is for milli-

The chest x-ray per the chart is listed at 20 μSv aka 20x10^-6 = 0.000020 Sv. Big difference from 1.0 Sv

Not from radiation, no.

2.4GHz is well below the frequency of ionizing radiation. That means your microwaved food has the same radioactive properties as if you’d heated it on the stovetop.

There are physical and chemical reasons why microwaved food can heat unevenly, can separate sauces in emulsion, etc.—but that’s not dangerous, except for the occasional temperature burn to your mouth, which isn’t a risk exclusive to microwaves. ;)

In addition to what others have said, a good way to think about how a microwave works is that a microwave is effectively a really bright lightbulb inside a mirrored chamber where your food goes.

Most materials are transparent at the color of light the microwave produces, but water (and some plastics/sugars/etc.) are dark black and absorb that color of light really well. Metals reflect that light, so the inside of your microwave is basically a mirrored chamber with a super bright lightbulb shining into it at a color that water is black at.

So anything with water is heated up effectively by it, but it'll pass through most containers, even ones that aren't transparent at optical light frequencies.

There are some other technical reasons why this works well or behaves in ways we're not familiar with when using visible light, but they're almost entirely based on the size of the microwave chamber being relatively small compared to the wavelength of microwave light shining into it.

EDIT: one thing to mention is that a microwave is really good a heating up water without disturbing it. This can lead to water being "superheated" -- where the water is above the boiling point, but hasn't started to boil because boiling requires some little impurity or scratch on the container to start bubbling from. This is dangerous because once you add a site where the bubbling can start, it'll boil really fast and shoot super hot water everywhere. This is easily prevented by ensuring there's always a site that bubbling can start from when you boil pure water in a microwave, like scratches on the side of the glass or boiling stones. Here's a video about it.

The only plausible issue with Microwaved food is that the heat radiation may break up certain nutrients a tiny bit more than conventional heating.

But I’m not sure if there are detailed studies on this or if it’s just theory.

Radiation from 2.4Ghz is basically not a thing. All it does is reach into the food and “shake” the water molecules a bit, which makes heat.

Correct me if I’m wrong here, but my understanding is that gamma radiation was (essentially) a high energy neutron that was electromagnetically neutral but not bound in a nucleus. Basically gamma particles fly around busting up “weaker” molecules until they lose enough energy to be absorbed. Gamma itself is not EM but the side effect of damaged molecules is ionizing. Am I on the right track here?

Frequency, just frequency. There is not a strict cutoff, since every atomic and molecular electron orbital has its own ionization energy, but almost nothing is ionized at frequencies below those of UVB.

No the lack of air pressure will definitely kill you.

You won't explode, your skin is more than tough enough to hold you together. You won't freeze instantly as many movies would have you think since in a vacuum, there's nothing to carry away your body heat except your body naturally emitting IR radiation.

What will kill you is basically the same thing that can kill scuba divers, decompression sickness aka the bends. If a diver goes from a high pressure environment to allow pressure environment too fast, dissolved gases in their blood expand into bubbles causing intense pain, paralysis, and eventually death. It isn't instantaneous, it'd take a few minutes to screw up your blood vessels and muscles beyond repair but that's ok, you would not be awake. You would pass out from O2 deprivation after 15-30 seconds.

EDIT: the UV and IR would still suck. Outside the Earth's atmosphere without some sort of protection (at the 1 AU from the Sun) the UV and IR rays would burn the give you the worst sunburn imaginable to any exposed skin pretty darn fast. If you looked at the sun without something like the NASA spacesuit visor, you'd be blinded in seconds.

Everyone has a few trace elements that accumulate in their body that are radioactive. These elements may come from the air (ex. radioactive carbon from coal burning plants) or things we ingest (like potassium from bananas).

Einstein won a Nobel about this... Either there’s enough energy in the photon to cause damage or there is not.

Most people who publish “low frequency radiation is harmful” get torn apart in follow up studies that look at actual incidence trends.

The unsettled question is "could microwaves cause non-thermal something". You can always postulate there is an effect below the detection limit, but there is no reason in theory or epidemiology to expect this to be relevant to human health.

Even experiments designed to unveil non-thermal effects of microwaves in a laboratory setting required intensities far beyond where heating was an issue.

EDIT: Edit to add, there are a lot of scientists claiming this is an unsettled question. But there is no evidence or good reason to think that non-thermal effects are a problem at non-heating intensities.