1

Physics, Astronomy & Cosmology / Re: Can planets form without a star

« on: 17/01/2020 08:45:15 »

I don't see any reason planets couldn't form under these conditions.

There are plenty of brown dwarf "failed stars" that are essentially large gas giant planets that never quite got big enough to ignite and turn into stars.

There are thought to be many starless "orphan" planets, but they are essentially impossible to detect with current methods (most of which detect the planets indirectly through measurements of their host stars). But even if the universe is teeming with orphan planets, it is still unknown what proportion of them were born in interstellar space, and what proportion were born near stars, and then tossed out through interaction with some more massive bodies.

2

General Science / Re: Are man-made things the nemesis of nature?

« on: 26/12/2019 16:44:48 »

The distinction between natural and unnatural is rather... artificial 

People are naturally occurring, and all that we do is part of our nature... so everything is natural (why is a skyscraper any less natural than a termite mound, or a beaver dam, or a wasp's nest?)

That said, the OP points out that there is an apparent oppositional relationship between our economic goals and a stable environment/ecosystem.

From my perspective, I think this has more to do with how our economic system is structured than the money itself: we don't typically ascribe much value to resources until they have been extracted for use, and don't recognize the value of services rendered by nonhuman, non-industrial systems, and even in cases where that value is recognized, there is no mechanism to integrate it into our economic systems.

For example, imagine a mangrove forrest that protects a coast from erosion, prevents seawater from contaminating freshwater, and provides a breeding ground and nursery for ocean-dwelling fish. Landowners don't pay the mangroves for keeping their properties from falling into the sea. Residents don't pay the mangroves for keeping their water potable. Fishermen don't pay the mangroves (or the sea, for that matter) for providing them with fish.

If a developer comes along and offers to buy the mangrove-filled real estate for a paltry $200000, with plans to build a marina, what mechanisms are in place to protect the millions of dollars of real estate and millions per year of fishing revenue?

https://www.sciencedirect.com/science/article/pii/S2212041612000046

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Physics, Astronomy & Cosmology / Re: Can Atoms Touch Each Other?

« on: 18/12/2019 18:01:55 »

well... atoms don't have hands, but there are several reasonable definitions of touch that would include two atoms "touching."

There are also some definitions that would have requirements that one (or two) atoms couldn't possibly satisfy.

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General Science / Re: why are omega fatty acids called Omega?

« on: 08/12/2019 03:26:19 »

typically, the omega will be followed by a number (like 3, or 5)

omega (ω) is the last letter of thee Greek alphabet, and is used in chemistry to denote the end of a long chain. an ω-3 unsaturated fatty acid is one that has a C=C bond three bonds in from the last carbon of the chain.

https://en.wikipedia.org/wiki/Omega-3_fatty_acid

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The Environment / Re: How much heat is generated from methane from burning vs. the greenhouse effect?

« on: 02/12/2019 18:06:22 »

Long story short: it is better to burn it.

Burning 1000 kg of methane releases about 5×10¹⁰ J. But methane that is released into the atmosphere ends up "burning" anyway (converting methane and oxygen to carbon dioxide and water), in the upper atmosphere, releasing the same amount of energy, just over a longer timescale, and higher up in the atmosphere. The different location and timescale of the conversion of methane and oxygen to carbon dioxide and water may introduce a small difference in how much of that energy goes into heating the air near the surface, but this also ends up being minuscule compared to the amount of energy that can be trapped by adding 1000 kg of methane to the atmosphere.

Before degrading into carbon dioxide, methane is much more potent as a greenhouse gas. Over the course of 100 years, 1000 kg of methane "traps" about 30 times as much energy as 1000 kg of carbon dioxide.

Calculating precisely how much energy gets trapped in not straightforward, and depends on many assumptions (for example adding 1000 kg of methane to an atmosphere with 400 ppm carbon dioxide will not necessarily have the same effect as adding to an atmosphere with 600 ppm carbon dioxide). But as a rough approximation, having increased atmospheric carbon dioxide concentrations from 300 ppm to 400 ppm required about 5×10¹⁴ kg of carbon dioxide being released into the atmosphere. This is predicted to change the temperature by about 1.5 °C over the next century, which would require on the order of 10²⁵ J (based on the heat capacity of the atmosphere and oceans--as worked out in the 3rd reference below). This works out to about 2×10¹⁰ J/kg or 2×10¹³ J for 1000 kg of carbon dioxide, so this would be on the order of 6×10¹⁴ . (10000x as much as burning--and probably 1000000x as much as the difference between burning on purpose and slow oxidation in the upper atmosphere)

https://en.wikipedia.org/wiki/Global_warming_potential
https://www.epa.gov/ghgemissions/understanding-global-warming-potentials
https://scholarsandrogues.com/2013/05/09/csfe-heat-capacity-air-ocean/

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General Science / Re: Herb and marijuana anxiety

« on: 17/11/2019 18:45:03 »

Hey guys... chill out. 

Cannabis has unfortunately not been studied very well under rigorous scientific conditions. Much of this is because it has historically been very difficult to get permission to study in human subjects, and approval often comes with stipulations that limit the sample sizes, or what the source of the test materials is (for a long time, in the US, studies needed to get their cannabis from the DEA... not exactly an uninterested party--there are actually instances in which researchers acquired official permission from their university, hospital, IRB, and local, state, and federal law enforcement agencies, only to be told that there was no cannabis for them to conduct their studies with (oh well). Many of the organizations in the USA, that researchers must satisfy in order to get permission or funding to run controlled tests involving cannabis have specific directives not to facilitate research that shows anything other than harm. It remains schedule 1 here because there is "no proof of medical utility" while researchers are banned from conducting studies looking specifically for benefits. (see more here: https://www.ncbi.nlm.nih.gov/books/NBK425757/ and here: https://www.rollingstone.com/culture/culture-features/why-is-it-so-hard-to-study-pot-124767/)

This means that most studies done in the US are specifically looking for harm, are often looking at longitudinal or epidemiological studies (which have sooo many confounding factors), and it is difficult to publish null results, so altogether, we are left with a significant bias in the literature.

Luckily, there has been some research done in Israel (https://cannabinoids.huji.ac.il/), among other places, with some promising results. I am skeptical of many of the medicinal cannabis claims (also often made by interested parties, and then hyped by those who wish to believe and those who profit by having others believe). But it would seem that there is serious research that is getting underway.

As far as recreational use goes, cannabis poses some very real, but relatively mild health risks.

For instance, many users (especially those who started using early in life) do use it habitually. It is not physically addictive (unlike drugs like alcohol and benzodiazepines, which have potentially lethal withdrawal symptoms, or drugs like opioids, nicotine, and amphetamines which can have significant physiological distress caused by withdrawal. Even drugs like caffeine have a greater physiological withdrawal effect.)

Smoked cannabis carries with it many of the dangers of inhaling any burning plant matter. And apparently vaporized extracts may be even more dangerous (it may be that this has more to do with lack of regulation, and greedy @$$holes willing to dilute their products to make a buck without any care for the consumers, or there could be some as-yet unknown reason why vapors are more harmful than smoke...)

The connection to psychosis is somewhat troubling, but I have yet to see studies showing a causative link conclusively, or providing any sort of insight into how this could happen mechanistically. High dosages of THC (in the absence of CBD, or with only traces of it) can certainly precipitate acute psychosis. But this is temporary. I'm sure there are cases of people frequently who get so high that they have episodes routinely, but I don't see this accounting for the supposed long-term risks.

My opinion is that the risks and benefits both need to be studies much more rigorously. But that in the meantime, cannabis be allowed as a legal product for both medical and recreation use, so long as the industry is heavily regulated, taxed enough to pay for costs to society (as should be done with alcohol and tobacco), and is kept away from children. So much more harm has been done to society by the war on cannabis than by the drug itself.

(wow, that turned into quite the rant! sorry)

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Chemistry / Re: Why does egg white turn from translucent to white when whipped?

« on: 01/11/2019 14:02:45 »

I think it's the same reason that snow is white while ice is translucent/transparent.

Light will scatter at every interface of two environments with different refractive indices. When the egg white is undisturbed, there is only the one surface. One it begins to fill with little air bubbles, there are many surfaces, each with its own reflections, refractions and dispersions--so no images can make it through, and it just appears as diffuse white light.

(note that cream does not need to be whipped to become white--it is already an emulsion of two liquids with different refractive indices)

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Physics, Astronomy & Cosmology / Re: What is the weakest sound that can be detected?

« on: 07/10/2019 20:57:20 »

Thanks but I didn't say by human ear.

Ok, then I think the most sensitive detectors we have for vibrations are those that are looking for gravitational waves (LIGO and VIRGO), which can detect minuscule vibrations. (I can't find the numbers now, and gotta run--but I will say that they are the equivalent of using a seismometer to hear a mouse fart on the other side of the globe.)

Found it: One example is 10⁴⁹ Watts at the source, but the source is 410 Mpc away, or 1.26x10²⁵ meters away. (so not as faint as I thought...)

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Chemistry / Re: Why are most molecules in singlet state if the triplet state is lower energy?

« on: 01/10/2019 16:46:56 »

Molecules adopt the lowest energy state they can, subject to laws of thermodynamics (zero point energy and boltzmann distribution) and QM (Pauli exclusion principle). (sometimes it can take a while for a metastable state to decay into the most stable state--especially when a change in spin state is involved)

The energy of an electronic state involves contributions from electron-nucleus interactions (energy shell, n), electron angular momenta (L and m_L) and electron-electron interactions (electrostatic repulsion and exchange energy).

For molecules with an odd number of electrons, there will always be at least one unpaired electron (doublet).

For molecules with an even number of electrons the choice beetween singlet and triplet (or higher) will be determined by the interplay of the aforementioned contributions. Typically differences in orbital energy due to n, L, and m_L are sufficiently large to favor the singlet state. However, if there are multiple orbitals with the same energy (degenerate) or very close, then the energy due to exchange can lead to triplet (or higher) states being favored. (essentially, if there are multiple electrons in degenerate orbitals, it is slightly favorable for their spins to align, leading to a high spin state)

Subtle effects in molecular geometry or composition (breaking or forming degeneracies) can thus lead to more stable high spin states, or more stable low spin states.

O₂ is an example of a simple molecule that is more stable in the triplet state (having two electrons in two . degenerate π* orbitals--singlet oxygen can be produced by either chemical or photochemical methods, and is incredibly reactive).

Ni(II) atoms have 8 d electrons, which favor a singlet state when the ligands around the Ni ion are in a square planar arrangement, but favor a triplet state when the ligands adopt a tetrahedral or octahedral arrangement. Elements near the middle of their respective rows in the periodic table an form very high spin states because they have half-filled orbitals (like Fe(III) which can adopt a sextet state with five parallel unpaired electrons, or Gd(III) which can have an octet state with seven parallel unpaired electrons)

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Physiology & Medicine / Re: Why Is It Easier To Complete A Puzzle After A "time-out" ?

« on: 13/08/2019 15:56:29 »

It is also quite possible that you are still working on solving the problem subconsciously.

11

Chemistry / Re: What is the proton number in NH3 and NH4+?

« on: 24/07/2019 17:31:14 »

If you add a proton to the actual nucleus of a chloride ion (which has 17 protons and 18 electrons), it becomes an argon atom (with 18 protons and 18 electrons). However, if you don't combine nuclei, and just "stick" the proton "in" the electron cloud of the chloride it forms a molecules of hydrogen chloride (which has 18 electrons surrounding a nucleus with 17 protons and a nucleus with 1 proton.)

Cl^– + H⁺ → HCl (chemical reaction)
Cl^– + H⁺ → Ar (nuclear reaction)

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Chemistry / Re: What is the proton number in NH3 and NH4+?

« on: 24/07/2019 03:49:05 »

Like I said in another of your threads, the number of protons in a given element never changes. Nitrogen always has 7 protons, regardless of what molecule it is in or what its electric charge is. The number of protons is what defines the element. If the number of protons was different, it would no longer be nitrogen.

I also agree with you but I am confused about why N got positivie charge on it. As I know positive charge means proton. one positive charge means one extra proton. could you explain it, please?

Yes, protons have positive charge. But, as has been pointed out many times, changing the number of protons in the nucleus changes the identity of the element. Instead, electrons are exchanged between atoms. Any atom (or molecule) with an equal number of protons and electrons in it will be neutral, any atom (or molecule) with more electrons than protons will be negatively charged (magnitude of charge scales linearly with the difference is), and any atom (or molecule) with fewer electrons than protons will be positively charged (again magnitude of charge scales linearly with the difference is.)

Note that it is also possible to add one or more protons to an atom (or molecule) without changing the element. each proton just has to be its own nucleus, ie a H⁺ ion. Chemists and biologists will often talk about the "protonation state" of a species, meaning how many of theoretically exchangeable protons are still on there.

13

Chemistry / Re: How to find sigma and pi bond?

« on: 23/07/2019 12:09:55 »

The COOH part has a pi bond between the C atom and one of the O atoms. That is the fourth.

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Chemistry / Re: In this reaction How many electrons carbon anion has?

« on: 22/07/2019 16:53:53 »

H⁺ has no electrons (just one proton--this reaction is a "protonation")
There are a total of 10 electrons in CH₃^– (6 from the C atom, 1 for each of the 3 H atoms, and 1 extra electron for the negative charge.) Two of these electrons form the inner "core" of the carbon atom (a full 1s orbital), and the remaining 8 electrons are all in the "valence." We can think of there bing 2 electrons in each of the 3 C-H bonds, and another 2 electrons as a lone pair on C.

When the H⁺ comes close to the electrons in the lone pair, it will be attracted electrostatically, and will get closer and closer until it is trapped and "bonded." The product molecule, CH₄ is neutral and has 10 electrons (the proton didn't bring any electrons with it.) The mechanism can be represented by a single curved and double-headed arrow, pointing from the lone pair of the methyl anion (CH₃^– and going to the proton (H⁺).

15

Chemistry / Re: How many protons and electrons of C and Cl are in this compound?

« on: 22/07/2019 15:38:18 »

Every H atom has 1 proton and 1 electron
Every C atom has 6 protons and 6 electrons
Every Cl atom has 17 protons and 17 electrons

These are all conserved when the atoms come together to form (neutral) molecules.

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New Theories / Re: How will buckyballs fired at a double slit behave?

« on: 17/06/2019 21:09:23 »

Not everyone on this forum is an expert, certainly not in all topics discussed here. However, some of the members posting in this thread (including myself) are very well educated in QM. You would do well to try to understand what we are saying. Based on the types of assertions and confusions you (pittsburghjoe) appear to be making, and the great degree of confidence you appear to be displaying, I suspect that you currently reside somewhere near the top of "Mt. Stupid" (https://www.theengineeringmanager.com/growth/mount-stupid/)


Screen Shot 2019-06-17 at 4.06.15 PM.png (127.11 kB . 990x690 - viewed 2126 times)

Don't worry, it is possible to scale back down (and to the right side), but it's a very disconcerting climb...

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Physics, Astronomy & Cosmology / Re: Can tunneling work with gravitational potential wells?

« on: 15/06/2019 12:34:43 »

Tunneling amplitude is proportional to e^{–width of barrier}

https://en.wikipedia.org/wiki/Quantum_tunnelling

even empty space can be viewed as a barrier through which to tunnel.

Electric potentials within molecule-scale systems can have very high gradients, so the distances involved are small.

For gravitational wells, gradients are typically not very strong (except in the hypothetical cases mentioned by evan_au), so the distances are likely to be such that tunneling can only happen once every million universe lifetimes or so (not actually calculated, but you get the idea)

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New Theories / Re: How will buckyballs fired at a double slit behave?

« on: 14/06/2019 03:53:18 »

Mass has little to do with how big a slit something needs to get through... (so the proposed experiment can neither confirm nor challenge the notion that waves can have mass--spoiler alert, waves can have mass)

...but there is a somewhat nifty way to see that mass is important for calculating tunneling barriers for particles (which depends on the wave function treatment of the particles):

We can measure the rates of chemical reactions, and see how much they change when hydrogen atoms are switched for deuterium (chemically identical isotope, but with twice the mass). This is called the kinetic isotope effect (or KIE). Sometimes a hydrogen atom has to tunnel from one place to another for the reaction to occur, and sometimes (especially when the reaction is very cold) this is the rate determining step, which means that we can directly measure how long (on average) it takes for protons to tunnel from x to y, and compare with hoe long it takes deuterons to tunnel from x to y. When this tunneling is the rate determining step, the KIE is very large, sometimes even slowing down by a factor of 100 when doubling the mass of the tunneling particle. This means that mass is an important property of a quantum object, even when considering it as a wave.

https://en.wikipedia.org/wiki/Kinetic_isotope_effect#Tunneling

19

General Science / Re: Can you make a huge prism, and disperse light in different colors?

« on: 04/06/2019 02:45:57 »

I just found this reference online: https://www.nnin.org/sites/default/files/files/Karen_Rama_USING_CDs_AND_DVDs_AS_DIFFRACTION_GRATINGS_0.pdf

The CD peeling methods might be of interest to those, likeJMerrill, who wish to incorporate rainbows in artwork, and the equations shown might be of interest to those, like Colin2B, who wish to examine the mechanism of forming those rainbows--it turns out that one can even calculate the spacing of the ridges with some accuracy using a laser and a ruler (I am certain the error bars would drop if one used multiple lasers, each with a different wavelength...

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Chemistry / Re: Does magnesium sulphate react with hydrochloric acid?

« on: 01/06/2019 21:48:41 »

And thanks @chris and @Colin2B