Recent comments in /f/askscience

Bwyanfwanigan t1_j9y7fn4 wrote

Reply to comment by CrustalTrudger in How much do the different factors affect sea level rise? by Natural-Cap4008

Serious question. I've never understood how sea levels measured in the past can be compared to now that we are using satellites. Before satellites was there even a means of measuring global sea level? The same question has bothered me about climate measurements which in the past were not digital and inaccurate. Not a denier, just always wondered about this and never thought to ask.

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CrustalTrudger t1_j9y6iau wrote

Reply to How much do the different factors affect sea level rise? by Natural-Cap4008

> In my minimal research and remembering university classes on environmental issues, I believe that sea level rise is caused predominantly by the increase in temperature of the ocean, which is caused by multiple different factors. My question (well kind of 2 questions) is/are, do we know how much h the different factors cause the seawater to expand?

This is largely incorrect. For current rates, this is pretty easy to find e.g., this page from NASA. The total sea level rise rate is 3.4 mm/yr. Of that, 2 mm/yr (or ~60%) is from increasing ocean mass (i.e., addition of mass to the ocean from melting land-based glaciers and ice sheet) and 1.2 mm/yr (or ~40%) is from steric changes (i.e., changes in volume related to both temperature increases - thermosteric changes - and salinity decreases - halosteric changes).

> And/or do we know how much the different factors cause the sealevel to rise?

This is described on those linked NASA pages as well. For the total sea level rise, this is something that is now measured directly from satellite altimetry, i.e., we measure the surface height of the ocean over time and find average changes in height. In terms of attributing the components, we can estimate changes in mass from satellite gravity measurements and we can estimate changes in temperature and salinity (and in turn estimate their contribution to steric changes) through measurements from "floats".

It's also worth noting that the above are effectively current rates. If we look at longer term averages over the last 100+ years (e.g., Frederikse et al., 2020), we find that the long term average is ~1.5 mm/yr (i.e., the current rate represents an acceleration). In terms of long-term contributions, changes in ocean mass again dominate with the steric (whether talking about thermosteric or halosteric) components being more variable in both time and space (i.e., at a global average level, their relative contribution varies through time, but also at a given time, their relative contribution are not consistent spatially).

In short, whether we're considering current rates or average rates over the last 100 years, changes in ocean mass dominate the signal of sea level rise. Steric changes are definitely important, but it's incorrect to say they are the largest component.

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sticklebat t1_j9y2cji wrote

Reply to comment by Implausibilibuddy in What does it mean for light to be an excitation in the electromagnetic field? by Ethan-Wakefield

Superficially, kind of? There are many differences though. One is that the ether was proposed in order to provide a rest frame for light, whereas the fields upon which modern physics is based are fully relativistic. Another is that the ether was thought of as a physical thing thing with density, velocity, etc., and whereas fields can’t really be described in those terms, at least not as directly. It’s more that fields can give rise to them.

TL;DR an ether theory is similar to fields in that they permeate all of space, but they’re fundamentally different from each other in properties and mechanics.

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phonetastic t1_j9y0425 wrote

Reply to comment by amestrianphilosopher in Does the common flu vaccine offer any buffer against H5N1 (Bird Flu)? by Esc_ape_artist

All squares are rectangles, but not all rectangles are squares. And parallelograms are kinda rectangles, but not. Think of a door when you're building a house. A one-degree shift in the angles on the door might still fit the frame. A ten degree shift won't at all. Seems small, but it's functionally massive.

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619364290163 t1_j9xyzd1 wrote

Reply to comment by theluckyfrog in After a surgery, what happens to the air that was inside the incision? by cimmic

(Was asleep therefor a bit late of a response) That can also be due to the pressure used to inflate the abdomen. different levels of pressure are used to inflate the abdomen depending on where to operate and what to do (I.e. more pressure thus more expansion (and possible pain) can be required if you have to manoeuvre around a big cyst and less can be used to clip someone’s tubes. But it also depends ik how the internal organs and peritoneum (inner lining of the abdomen) are manipulated

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