21

Physics, Astronomy & Cosmology / Re: Has the distance between the sun & earth changed?

« on: 23/01/2022 23:42:32 »

Im the one that asked the question; and thank you for posting this Origin.

I would like to know if this distance is a big cause of Climate change.

I see from posts that the distance does change, though is there an on going change that is climbing (a distance change or orbit change), and not staying nominal?

It can have an effect to some extent, and there are some cyclical changes in earth's orbit (see more here: https://www.fs.usda.gov/ccrc/education/climate-primer/natural-climate-cycles)

But the current (fast) changes in the climate are driven primarily by greenhouse gases (mostly carbon dioxide and methane).

We can see the effects of the cycles, as well as the recent trends (the practically vertical line at the far right) by looking at atmospheric carbon dioxide concentrations found in ice cores, the record of which goes back almost a million years (https://keelingcurve.ucsd.edu/)

co2_800k.png (110.13 kB . 1000x600 - viewed 11076 times)

22

Physics, Astronomy & Cosmology / Re: Whats a branch of physics with high potential that has unjustified disinterest

« on: 10/01/2022 22:11:01 »

I may be biased (as a chemist), but I would recommend physical chemistry. It has all the mathematical rigor and knowledge of "standard" physics, but it's also much more easily explored experimentally than high energy physics, astrophysics, cosmology etc.

Physical chemistry (or chemical physics, or materials science, depending on what you're looking at) involves a lot of quantum mechanics (because it largely deals with collections of photons, electrons, atomic nuclei, and how they interact with each other). It also involves relativity, when considering very heavy atoms (like gold or uranium), in which electrons that get close to the nucleus have enough kinetic energy that reletivistic considerations must be taken.

Bridging the gap between physics and chemistry means that it is very useful, and often overlooked by purist physicists and chemists alike. But physical chemistry is critically important for "sexy" topics like (among other things):
• quantum computing (and regular computing)
• LEDs (and OLEDs)
• Photovoltaics
• Drug design
• Protein folding
• Sensing
• Spectroscopy
• Making new dyes (for aesthetics, cellular imaging, light emission, light harvesting)

23

General Science / Re: Is this a feasible system for recycling CO2?

« on: 02/01/2022 18:57:56 »

24

Physics, Astronomy & Cosmology / Re: How can we see ultraviolet light in Balmer series?

« on: 02/01/2022 17:59:12 »

I think it is also important to note that the Balmer series (and Lyman, and Paschen etc.) are for atomic hydrogen, not molecular hydrogen (H vs H₂). H is not stable at standard temperatures and pressures, but is stable at temperatures where electronically excited H atoms are thermally accessible.

25

Physics, Astronomy & Cosmology / Re: How can we see ultraviolet light in Balmer series?

« on: 28/12/2021 16:19:30 »

In the image provided, notice that the leftmost lines appear less intense than those on the right but still appear (to the eye, and on the screen) to be the same hue. The emissions are not actually less intense (if anything, they should be more intense, depending on how the atoms are being excited...) It's just that our eyes (and/or whatever camera was used to capture the image shown) are significantly less sensitive there.


human_cone_action_spectra.gif (7.91 kB . 766x369 - viewed 7492 times)
https://www.unm.edu/~toolson/human_cone_response.htm

26

Chemistry / Re: Why does HNO3 exist but HPO3 does not?

« on: 29/11/2021 21:17:22 »

One can think of it as a hydration/dehydration equilibrium:
H₂O + HXO₃ H₃XO₄

There are two reasons that the equilibrium favors the left-hand side when X = N, but the right-hand side when X = P, As, (or Sb, I believe):

1) (the simple answer, pointed out by Bored chemist) nitrogen is the smallest of the bunch (covalent radius of N = 75 pm, P = 106 pm, and As = 119 pm), so it is simply harder to fit the extra oxygen on there.

2) (the complex answer) the 2p orbitals on nitrogen and oxygen have fairly similar energies** (–13.1 and –15.9 eV vs vacuum, respectively) as well as very similar sizes (as noted in point 1), as well as shorter σ bonds (also due to point 1). This means that the p orbitals on neighboring O and N atoms can form very strong π interactions, and that the electrons in the π bonding and π anti-bonding orbitals would both be shared fairly equally.

In contrast, the valence of the phosphorus atom is a 3p orbital, with a much higher energy** (–10.2 eV; again comparing to –15.9 eV for O), and extends much farther away from the nucleus (but not towards a neighboring atom).

Screen Shot 2021-11-29 at 4.15.13 PM.png (42.56 kB . 794x624 - viewed 7353 times)

This means that in HNO₃ the nitrogen atom has much more electron density compared to the P atom in HPO₃ (the N is less electrophilic than the P, making the N less likely to accept electron density from another O), while the oxygen atoms bound to N have less electron density than those bound to P (the P-bound O atoms are more basic than N-bound, making them more likely to gain H⁺) and much stronger N=O bonds than P=O bonds (so it is easier to break the double bonds).


Screen Shot 2021-11-29 at 8.08.24 PM.png (45.63 kB . 546x680 - viewed 7331 times)

* https://www.schoolmykids.com/learn/interactive-periodic-table/covalent-radius-of-all-the-elements
** https://www.colby.edu/chemistry/PChem/notes/AOIE.pdf

27

Geology, Palaeontology & Archaeology / Re: How to genetically classify a weathering mineral?

« on: 16/11/2021 22:26:12 »

I would say this is a question of "taxonomy" not "genetics" (rocks don't have genes)

I think the OP is right that minerals as a result of weathering would be an exogenic classification, but I am not sure... I think the best member to answer this would be @Bass

28

The Environment / Re: Is Rising CO2 level a Problem?

« on: 15/11/2021 14:38:47 »

Climate change aside, there is another *major* problem with increasing CO₂ in the atmosphere. It is literally and figuratively changing the bedrock of our marine ecosystems!

As it dissolves in ocean water, it causes a shift in this equilibrium:

CO_2(aq) + H₂O(aq) + CaCO_3(s) Ca²⁺_(aq) + 2 HCO₃^–_(aq)

While this looks innocuous enough, here is the catch: CaCO_3(s) is the primary component of sea shells, and coral reefs. More CO₂ released into the environment means that animals at the bottom of the food chain have weaker shells, and less healthy coral reefs, which then translates to major disruptions to the ecosystems that depend on the reefs.

https://ocean.si.edu/ocean-life/invertebrates/ocean-acidification

As with climate change, the problem isn't necessarily how much CO₂ there is at any given time (over the course of geological history, it has been much higher and much lower than it is today). The problem is how quickly things are changing. Sea creatures need time to evolve shells with slightly different compositions, or attain new behaviors to adapt to their new reality. Ecosystems need time to adjust to new status quo. And it is a good time to remind everybody that many of these systems are susceptible to positive feedback loops: small but sudden disruptions in an ecosystem can lead to odd boom-bust cycles that then really mess everything up.

(imagine that the oysters' shells become weaker, making it initially easier for otters to eat them. The population of otters will grow quickly while the oyster population shrinks. At a certain point, the oyster population cannot sustain itself, and crashes. Then the otter population crashes. If this were a "normal" predator-prey equilibrium, a brief disturbance would cause some oscillation in populations for a while before settling back down on the original equilibrium. But if the "balance point" is continuously changing because the environment is changing during the oscillation, then both species could go extinct in a matter of decades!)

29

Physics, Astronomy & Cosmology / Re: Energy loss in electrolysis

« on: 11/11/2021 05:35:06 »

Often it depends on how patient you are. If you want to move or exchange lot of energy very quickly, you have to pay for it (energetically). Energy efficiency for splitting water into hydrogen and oxygen can be done with >90% efficiency using precious metal catalysts and low current densities. But once the currents involved are large enough that it is limited by the resistance of the solution, then you can basically view it as a resistor in the cell, producing heat with a power of current times overpotential (applied potential minus the thermodynamic potential). Energy efficiencies of <70% are acceptable if the energy/time is more important than energy/cost.

You didn't specify whether the recombination is electrochemical or not, or how you would like your energy.

If you want heat, I can get you a virtually 100% efficient source as any power you like up to a few thousand degrees °C. (ie a hydrogen oxygen flame, anywhere from a 50 W jewler's torch to a 2,000,000,000 W space shuttle engine).

If you want that energy in the form of DC electricity, you can use an acidic proton exchange membrane-based fuel cell to get 50–60% of your energy back from combining hydrogen and oxygen. (the rest goes to heat)

If you want AC, then either you burn it and drive a turbine, or convert DC to AC and take yet another conversion hit.

If you want light energy...

30

General Science / Re: Can Medicine solve Global Warming?

« on: 10/11/2021 15:10:54 »

It would be interesting to compare the carbon footprints of recreational drugs vs other forms of recreation and consumption.

IMHO a dozen milligrams (or so) of THC* and a plate a falafel is more enjoyable than a glass of bordeaux* and a filet mignon.


*which is legal for. recreational use for those 21 years and older in many parts of my country.

31

Technology / Re: What are some low-tech ways to address climate change?

« on: 08/11/2021 20:38:57 »

Regarding livestock, the ingested/exhaled carbon is going to balance out perfectly. That is, until we find a way to convert fossil fuels directly into feed, and then we will have to count animal exhaust too.

One aspect, however, is that much of the nitrogen needed for agriculture (the footprint of which is dominated by livestock and production of feed for livestock) is fixed through highly energy intensive methods. The Haber Bosch process accounts for roughly 1 % of global energy demand (and associated emissions). So, this is a big deal. We wouldn't need nearly as much nitrogen if we were eating the crops directly, but since we are feeding it animals, we need much, much more plants (and therefore more fertilizer).

Again, the problem isn't the animals themselves. Rather, it is that we have found a way to intervene in natural processes to speed them up, using fossil fuels.

32

Technology / What are some low-tech ways to address climate change?

« on: 02/11/2021 16:54:18 »

NOTE: this thread will assume that anthropogenic climate change real, as it is generally accepted by the scientific community—any attempts to shift discussion towards questioning accepted science will be removed.

Since it seems that there is not yet enough political or economic will to shift to renewable energy sources or make major societal changes (like population control, limiting meat-based agriculture/diet, not clear-cutting our forests, different approach to transportation, less materialism etc.), I am hoping to identify methods that are economically viable to be undertaken by individuals and small communities/organizations that can have significant impacts in the near term.

Feel free to propose solutions or discuss others' proposals. I'll start:

1) A significant percent of the global energy budget is producing low-grade heat for residential and commercial buildings during the winter months. Insulation is the first step.

After that though, we need better ways to heat our homes and businesses. While heat pumps, solar heaters are better than gas-, oil- or coal-powered heaters (which essentially directly converting valuable fuel or electricity into waste heat), wind-powered heaters may well be the way to go. Essentially, the mechanical energy of the rotor can be converted directly into heat either by using a Joule heater (like a water brake) or an induction heater (spinning a magnet around near a conductive material to produce eddy currents)

I found this:
https://solar.lowtechmagazine.com/2019/02/heat-your-house-with-a-water-brake-windmill.html

2) We might be able to send some energy back out to space more efficiently.
Just simple mirrors or white paint over dark surfaces that get direct sun would be useful. This could be especially important in tropical regions where sunlight is most intense, in polar and high-altitude regions that have lost ice/snow cover, revealing dark rock/water/etc.

Also, to increase the rate of energy loss from the ground during the night time, wind, hydro, or thermoelectric power could extract usable energy out of the surrounding environment and be used to power LEDs or lasers that can be used to emit visible light into space. (obviously the cost to power ratio of these devices would be significant, but they also serve a purpose that is otherwise not being done.

33

General Science / Re: What's 0^0 ?

« on: 02/11/2021 14:20:36 »

0 + 0 = 0.

0 * 0 = 0.

0 / 0 = 1.

0 ^ 0 = Undefined.

0 - 0 = Nothing.

Ps - Dyscalculia!
👻

I would switch the third and fourth: 0/0 = undefined and 0⁰ = 1

34

General Science / Re: What's 0^0 ?

« on: 02/11/2021 06:03:12 »

(edited to correct inequality direction)

y = x^x is well-defined for all x > 0. The limit as you approach from positive side is clearly 1. Sure, the limit as you approach from the negative side, it's not well defined (in the reals), but neither are any of the points for x < 0, so I'm not sure that's a problem.

y = 0^x is (boringly) well-defined as 0 for all x > 0. The limit as you approach from positive side is clearly not 1, but again, because the limit as you approach from the negative side is not well defined (in the reals), it doesn't seem that odd to me to have a jump discontinuity for one point before all hell breaks loose.

y = x⁰ is clearly (and boringly) 1 across all reals.

I was taught to think of y = x^a as y = 1 × x^a, interpreted as 1 times x, a times. So if a = 0, you're multiplying 1 by x zero times, and it doesn't matter what x is.

35

The Environment / Re: If the Earth is losing mass, is the atmosphere expanding?

« on: 02/11/2021 00:50:49 »

The topic of discussion changed after this point, so I have taken the liberty of splitting the thread. Please find the other thread here: https://www.thenakedscientists.com/forum/index.php?topic=83465.0

Or continue the original discussion in this one.

36

That CAN'T be true! / Re: Why can't water vapour be the driver of today's climate change?

« on: 31/10/2021 06:49:34 »

Quote from: chiralSPO on 29/10/2021 18:47:17

CO2 is probably NOT a driver of climate change historically

So when did the laws of physics change? The current warming cycle began about 20,000 years ago and so far looks pretty much like all the others, with CO2 following around 500 years behind a steeply rising temperature until very recently when the CO2 graph has accelerated.

Are you being intentionally daft? (I hadn't pegged you for a troll)

Nobody said the laws of physics changed (that's a straw man argument). Human activities changed. Most importantly, starting about 250 years ago, and accelerating nearly exponentially since then (is this the "fairly recently when the CO2 graph has accelerated" bit?): we have been extracting carbon that has been out of the atmosphere for several million years (ie orders of magnitude longer ago than the timespan of ice core histories), and converting it into carbon dioxide with great efficiency.

You might never believe it, but the amounts of coal, oil, and gas that have been extracted over the course of history have actually been documented quite well. (something about book-keeping, I dunno...) It also turns out that the ¹²C/¹³C/¹⁴C ratios in fossil fuels is different from that which was in the atmosphere up until we started burning them (ie in the ground, is old carbon, so is depleted in radioactive ¹⁴C, and ¹²C and ¹³C are fixed by photosynthesis at slightly different rates, and 100% of C in fossil fuels is from biological organics). Though nuclear weapons testing also disrupted atmospheric ¹⁴C levels a bit so...

So we can actually see (using CO₂ from the ice cores) how this isotope ratio has varied historically. And wouldn't you know it! It's been quite constant* for eons and only when we started digging up the other stuff and burning it did the concentration of CO₂ change significantly, AND the isotope ratio shifted. And, here's the really cool part. We can see from how much the concentration of total CO₂ has changed, and how much the ¹²C/¹³C/¹⁴C ratio has changed, and knowing the original atmospheric ratio ratio and the ratio in the ground, we can see that we are responsible for essentially 100% of the increase in CO₂, in the form of burnt fossil fuels.

https://www.climate.gov/news-features/climate-qa/how-do-we-know-build-carbon-dioxide-atmosphere-caused-humans


RubinoCO2Isotopes.jpeg (54.01 kB . 750x462 - viewed 4837 times)

F1.large.jpg (126.41 kB . 1280x803 - viewed 4769 times)

*Isotope ratios associated with other changes in historical CO₂ concentration do not appear to be the same in magnitude nor flavor. (for example, the last deglaciation:  https://www.pnas.org/content/113/13/3465)

37

That CAN'T be true! / Re: Why can't water vapour be the driver of today's climate change?

« on: 28/10/2021 20:42:10 »

In that case there must be more more than co2 responsible for the vast majority of heat retention.

Well, the sun plays an important role too... (it's where the retained heat comes from)

But a sudden change in one parameter can often lead to a slow change in others. Like plugging the drain of a running shower. The water keeps flowing in at a steady rate, and the drain stopper was only added once, a few minutes ago, so why does the water level continue to rise?

38

That CAN'T be true! / Re: Why can't water vapour be the driver of today's climate change?

« on: 28/10/2021 18:08:59 »

If carbon dioxide has increaced 25 percent in 100 years, the temperature of the earth was 300k in 1900, why has earth not increaced in temperature to 400k?

One reason is that it is not a linear relationship between average temperature and CO₂ concentration. (the relationship is complex enough there is not just one equation that can be used to model it well, but we can know for sure that it isn't linear)

Another major issue is that the Earth's average temperature is still increasing because of the excess carbon dioxide put out last century, and even if the carbon dioxide concentration were to suddenly stop and remain constant right now, temperatures would still continue to increase for decades (the earth is a big place and it takes a while for it to warm up)

39

That CAN'T be true! / Re: Why can't water vapour be the driver of today's climate change?

« on: 27/10/2021 20:10:34 »

Now either all the published papers on CO2 absorption are wrong or plagiarised from two flawed sources, or the hypothesis that increasing p[CO2] will increase surface temperature is nonsense.

The atmosphere absorbs effectively 100% of the radiation at these wavelengths (if you're looking down the whole length of the atmosphere), but the % absorbance or % transmittance or however you choose take your IR spectrum has very little bearing on the greenhouse effect (it's mechanism, magnitude or cause).

Even if the atmosphere is treated as 100% opaque to the wavelengths absorbed by CO₂, it is straightforward to see that changing the concentration of CO₂ will still change the mean free path of the photons that are interacting with CO₂.

We can think of a photon emitted from the ground and needing to reach "space". It will start out going straight until it runs into a CO₂ molecule and gets absorbed, hangs out for a time before being re-emitted in a random direction until it bumps into the next CO₂ molecule or escapes to space. Essentially it have to take a random walk from the surface to some altitude sufficiently high. And the time it takes has nothing to do with the speed of light (we can assume it is c for this), but rather in how many stops it has to take (each one being a significant delay compared to whizzing by at c), and how much time is being spent traveling the "correct" way.

The higher the CO₂ concentration, the shorter the mean free path of the photons.
The shorter the mean free path of the photons, the more hops need to be taken to escape (exponentially so!)
The more hops needed to escape the slower the rate of energy transfer through the atmosphere.

40

The Environment / Re: If the Earth is losing mass, is the atmosphere expanding?

« on: 26/10/2021 00:39:00 »

Anyway, back to atmospheric thickness, a fairly established and accepted fact is the temperature is rising.  The gas laws mean  either increaced pressure or increased volume or a bit of both, pressure in this case would be the gravitational attraction, so the atmosphere must be expanding . An increace in 2 degrees k would mean a significant variance in pressure and volume.

As I think about it more, I think the magnitude of temperature variation of the atmosphere by altitude is far more important than a few degrees K. Also, while, the greenhouse effect will lead to overall increased temperatures at low altitudes, at high altitudes the temperature can actually be slightly decreased.

us_atmosphere_temperature_vs_elevation.png (88.83 kB . 1125x1275 - viewed 6475 times)