Hacker News Reader

Comment by londons_explore | Hacker News Reader

> 'accelerated puberty'

> "at the turn of the 20th century, the average age for an American girl to get her period was 16 or 17. Today, that number has decreased to 12 or 13 years." -- Hector O. Chapa, MD, FACOG, clinical assistant professor of obstetrics and gynecology at the Texas A&M College of Medicine

As a government, I would be really worried about such a change in my population, especially if I didn't understand the exact cause. Previously the age of marriage was mostly based on this puberty age - if societal norms change and 12 year olds start having babies, that will be a huge impact on the economic outlook of the country.

View on HN

At the start of the 20th century the average American was probably malnourished and everyone had pellagra, because we cared more about growing cash crops than whether poor people were fed or not. This eventually changed because it meant we couldn't draft enough people healthy enough to go to war.

I wasn't asking what the problem was supposed to be with consuming BPA. I was asking what the problem was supposed to be with using BPA under the assumption that it can't get into the food. There really shouldn't be a problem in that case.

Parallel answers seem to state that dissolving is not a reaction, which seems weird to me, but OK.

I suppose it is a reaction, just not in the chemical sense

Wikipedia tells us that dissolving occurs when differences in electrical charge across molecules of solvent (e.g., a molecule of water is famously negative around the oxygen and positive around the hydrogens) interact with differences in electrical charge across molecules of solute such that the molecules of solute get stripped out of the structure they were in and surrounded by molecules of solvent, held in place by what appears to be essentially an ionic bond between the solute and the solvent.

I'm not sure why that's not considered "chemistry".

a chemical reaction is a specific thing within the realm of chemistry, rather than attempt to define it myself and get it wrong, I will quote Oxford Languages (via google) here:

chemical reaction: process that involves rearrangement of the molecular or ionic structure of a substance, as distinct from a change in physical form or a nuclear reaction.

So, a chemical reaction is not just what you would colloquially describe as a reaction of something that belongs to the realm of chemistry, it has a specific definition. A reaction is H + O2 = H2O (omitting concerns of stoichiometry for simplicities sake). A reaction is not e.g. salt dissolving in water, because salt stays salt (NaCl) and water stays water (H2O)

When sugar dissolves in water, it stays sugar. When salt dissolves in water, it becomes separate Na+ and Cl- ions.

> When salt dissolves in water, it becomes separate Na+ and Cl- ions.

This is something I wonder about. How separate are the salt ions when salt dissolves in water? If you add a chunk of sodium to water it will explode; that doesn't happen when you add salt.

"Reaction" typically means "chemical reaction." Dissolving is not a chemical reaction. BPA is tasteless and odorless, so it wouldn't adulterate the taste of the food is the point.

> Dissolving is not a chemical reaction.

I see that that is the standard terminology (which I was not previously aware of), but setting the terminology this way makes about as much sense to me as saying that there is no difference, as far as the chemistry is concerned, between a measure of distilled water and a measure of strong acid.

Reply on news.ycombinator.com