It must have some kind of chip inside it that stores my information so it can identify me when I hold it up to the scanner.

No, it doesn't necessarily mean that other gases like O2 are decreasing. The increase in CO2 is due to human activities like burning fossil fuels, and it's causing a shift in the composition of the atmosphere.

It's likely because the same basic processes that cause cancer in humans, like mutations, also occur in other animals.

[removed]

Have you ever hit 70kph when biking? Yeah me neither

Most of the earth’s atmosphere is nitrogen and oxygen, making up 99% of the atmosphere (approximately). So the small changes in oxygen are insignificant to the total—changes in trace gases though, especially greenhouses gases, are significant at much smaller changes in concentrations.

[removed]

Honestly a fair question since all helmets are designed for hits to the head.

They all protect for a specific type of hit to the head. Simplifying your example to a bicycle helmet vs. hockey helmet: A bike helmet is likely to be hit directly from the front, it is lightweight for ease of riding, and it will sacrifice itself to absorb as much impact as possible, making it single use only. Hockey helmets are designed for multiple hits, and protection from a projectile. H hockey puck might punch a hole through a bike helmet.

Quaaludes fall under the " muscle relaxants" class of drugs, which was generally prescribed as an aid to dela with insomnia due ot the conditions it induced.

they were somewhat freely available aswell since you could get them both as a free base or dilluted in a "salt"(the "disco tablets") but when they became used as a recreational drug this became a problem, since both overdosing on them leads ot nervous system shutdown(aka: coma and eventual Death) and the Lethal dose required drops dramatically if taken with alcohol.

the drug also carried a darker connotation as its properties also made it a choice for a " date rape drug" in the same lines as GHB(except in this case if the prepertrator wasnt careful they could upgrade their assault into manslaughter), and for this it was flagged as a controlled substance.

[removed]

[removed]

I know some of this, but not the whole answer.

One really important thing for helmets, carseats, etc is whether the material is multi-use or one-use.

One-use materials are generally far lighter for the same level of protection (protection itself a multi-faceted concept but I’m sticking with simplicity here).

Hockey helmets are generally lined with vinyl nitrile or polypropylene foam. Vinyl nitrile is the same stuff thats in HVAC gaskets, yoga mats, and all sorts of seals. It returns to its previous shape when you are done squishing it.

The inner foam of a motorcycle helmet is typically expanded polystyrene. It is designed to collapse and absorb force in an impact. Polystyrene foam is what many foam cups are made of (though obviously very different in structure in a helmet than a cheap cup). That foam has a bit of bounce and flex, but it is designed to permanently crush/collapse when it gets hit.

Both helmets have an outer shell that is designed to spread an impact over a large area.

But overall: multi-use vs one-use. Skateboard and hockey and snowboard helmets are multi-use (and weigh more for the same level of protection). You replace them when you take a massive hit that cracks the shell or sometimes after you use them a ton over time. Bike and motorcycle helmets and car-seats have to be replaced once they do their job - that foam does not work twice, but it’s much lighter for the same level of protection and used in applications where you don’t ever plan to actually need it.

[removed]

We have slightly more atmosphere than we used to. That's really the short answer to it. We added "stuff" without taking away "stuff". So we have more "stuff". A little bit more. Not a lot.

Which doesn't sound like much but little changes can have major impact to life that's evolved to a very narrow band of conditions.

[removed]

Fluffy snow vs. asphalt/trail

EDIT: as /u/mfb- notes below, these numbers are off by a factor of 10 - all these percentages should be one decimal point to the right (e.g. 0.2% -> 0.02%).

Yes. Most of the CO2 was made by burning carbon-containing molecules using oxygen from the atmosphere, so each CO2 molecule roughly corresponds to one less O2 molecule.

But since CO2 is a small portion of the atmosphere's total, this doesn't make a big difference. Today, CO2 is about 420 ppm, or about 0.42%, of the atmosphere; prior to humans it was about 280 ppm (~0.28%). That's a huge difference in terms of how much CO2 there is; there's almost 50% more today than there was a couple centuries ago. But it implies a change of only about 0.14 percentage points in the oxygen amount.

Since oxygen is about 21% of the atmosphere, that's a relative change of only about 1 part in 150 of the oxygen content, which isn't a big deal. Air pressure already varies by more than that (it's the equivalent of about 7 mb of pressure, roughly the difference between a mild storm and a clear day) as weather systems pass by, so your body is already well-adapted to handling such small changes in oxygen content.

(Actually, I wonder if typical sea-level pressure is a bit higher today than it used to be. CO2 is heavier than oxygen, so the atmosphere should "weigh" slightly more than it used to - by a factor of, give or take, about 0.07 ppt. That's not nothing! It should correspond to a global increase in surface atmospheric pressure of about a millibar, which should be detectable. [EDIT: okay, a tenth of a millibar is less.])

Even today, CO2 represents just 1/2,375th of the atmosphere.

Before the industrial revolution it was 1/3,571th

That's a change of less than 1/7,000th of the atmosphere.

Oxygen represents 1/5th of the atmosphere.

Some of that oxygen will have been consumed to make CO2, but not enough to matter, and more will have been emitted because CO2 is a limiting factor for plants.

The atmosphere has gotten very slightly thicker.

No genuine question is ever dumb. If someone legitimately doesn't understand something and is trying to learn, then we can help them learn. We don't chastise people because they weren't exposed to information we've already learned.

They're designed for the vertical speed you pick up falling off a bike, not really for moving collisions or collisions with moving objects. They're better than nothing, but you would need a much more robust helmet to protect you from the sorts of injuries sustained in motor vehicle collisions.

I wish I had a free award to give you for the phrase “bonking your noggin”

Ski helmets also assume you'll be traveling much faster than you would be on a bike. If memory serves the basic helmets we sell where I work assume you may be traveling upwards of 40 mph. And apparently ski race helmets assume you'll be going as fast as 80 mph if not faster

Oops, yes. Fixed.

this is sort of a dumb question to be honest. "why do people were a different helmet for a motorcycle versus playing hockey?" or any other random helmets

Near-field*