# Tag Info

1

There is always air resistance, unless you are in space. If there was no air resistance, a bullet would land at the same speed it was shot at. On Earth, a spent bullet is rarely lethal. In big wars (like World War II) it was common for soldiers to get hit by spent bullets. Normally they will hit you and fall away, causing just a bruise, An unlucky hit ...

2

Yes the bullets can fall down and injure or kill you. In fact in countries were celebratory gun firing is possible people are often injured by falling projectiles. Shooting straight up is less dangerous than at an angle because the terminal velocity is much lower than the muzzle velocity of the projectile. When shooting at an angle some of the horizontal ...

1

If this article is to be believed, you would have no problem at all - in fact you could feel where the cities are, let alone the mountains.

2

The answer can be found at the sound stackexchange - if you take a pure tone and reverse the phase of one of the stereo channels, there is no "sensible" direction in front of the listener that the sound could come from. We then conclude that the sound comes from behind us (because we have poor ability to figure out the direction of sounds behind us because ...

0

The first is, is my understanding described above correct? Basically, yes. The second is, how does this affect us healthwise? We are stuck with these debris of cesium-137 and strontium-90 for the next 30 or more years, but what effect do they have on us? Stochastic health effects (induced tumors, cancers, leukemia,…) of ionizing radiation are ...

0

Well technically speaking, time (or better say passage of time) is identical in two frames of reference that are not accelerating with respect to one another (i.e. at rest or moving at constant speed). So yeah, if an ant and an elephant are put on a missile and accelerated into outer space and back, they would have aged identically with respect to one ...

-1

Of course the order in an open system always decreases. Locally, like on the Earth, beautifull orderly structures can evolve (wich wouldn´t be possible if the Earth always had one side directed to the Sun), and nonetheless the total order of the system Sun-Earth would decrease. But human activity, by wich I mean the changing of the surface of the Earth by ...

4

I am not 100% sure if I understand your question but this might clarify the concept of center of mass (COM) of an object. It is defined by the following equation $$\int_{\mathbb R^3} \rho(\vec r) \cdot (\vec r- \vec r_{com}) \, \mathrm d V =\vec 0$$ where $\rho(\vec r)$ is the density of the object at a position $\vec r$ from the origin. If you modify this ...

1

In every object, there is a unique point called 'center of mass (CM)' around which the object's mass is equally distributed in all directions. In other words, mass is balanced at the CM in all directions. For a human it depends on body posture and positions of the limbs. An example CM is given below, which was obtained by segmenting the body; see the source ...

1

The second law of thermodynamics says that order always decreases in a system. This is incorrect. My air conditioner alone proves that this statement of the second law of thermodynamics is incorrect. I live in Houston, TX; I rely on my air conditioner for about six months of the year. My air conditioner does not violate the second law of thermodynamics. ...

2

As mentioned in a comment, entropy cannot decrease in a closed system. When you are considered life on Earth, it is not a closed system. Energy comes into the earth from the sun and radiates away from the earth as heat. In thermodynamics, we normally consider mostly engines because they are really simple in comparison to other systems. If we ignore the ...

1

Here is what wiki has to say about Polonium radiological toxicity: By mass, polonium-210 is around 250,000 times more toxic than hydrogen cyanide (the LD50 for 210Po is less than 1 microgram for an average adult (see below) compared with about 250 milligrams for hydrogen cyanide[66]). The main hazard is its intense radioactivity (as an alpha ...

2

Let's suppose you have swallowed one of the Po-210 sources from this student kit. Its activity is 3700 Bq (0.1 μCi). Based on the Table 6 in the meta-study [1], it is probably safe to ingest up to 0.02 MBq/kg of the Po-210. This means, that for 80 kg person, it is probably safe to ingest 1.6 MBq of the Po-210, so you "need" to eat approx. 400 of these ...

2

The other answers are adequate, answering not a thing to the first part of the question in your title: Would a neutrino bomb do anything? But questions in titles are important, so I will reply to the second part, Or can weak force kill you? : Of course the weak force can be lethal. The simplest example is the decay of neutrons , it is a weak decay , but ...

2

The Earth is much more massive than its human population. If the Earth is transparent to neutrinos from this device, so are the people on it. In supernova explosions the neutrino flux is large enough to have an important effect on fluid transport. (Kip Thorne discusses this in "Black Holes and Time Warps.") Here is an estimate that to receive a lethal dose ...

1

There was also a science fiction story where somebody invented a neutrino bomb. It was claimed that such a bomb would turn all the matter in it to neutrinos, which would escape without damaging anything. The first part doesn't work (think baryon conservation) but the second does. It pointed out that a vacuum would be left, so air would rush in with a ...

2

let's talk about efficiency bounds The flux of solar neutrinos at the earth's surface is on the order of $10^{11}$ per cm²/s. Even the largest detectors detect less than a few hundreds neutrinos by day. 7Be Solar Neutrino Measurement with KamLAND Let's assume the incredible facts that such detector has only 10 cm² area and that all the ...

3

This is a common misconception. The function above can be interpreted as follows. Sound of frequency $\dfrac{\omega_1+\omega_2}{2}$ with amplitude modulated by the cos function of frequency $\dfrac{\omega_1-\omega_2}{2}$. The cosine function becomes zero twice every cycle as well as reaching a maximum magnitude twice every cycle. So the intensity of the ...

2

Such a thing is generally possible. You can test this really easy: take a tuning fork without resonator (so really just the fork itself), hit the desk, hold the fork in the air and listen. You will probably hear almost no sound. Now plug your ears, do the same and press the fork root against your forehead. You will see (hear :-) ). Practically, that's a big ...

1

You would. The bones in your arms would conduct the vibrations to your ears, though I'm not sure you could really call that hearing. The bones in your ears and near your ears would certainly feel the vibrations, but without some sort of mechanism that changes vibrations in solid matter to sound, you wouldn't exactly hear it. You hands, however, would ...

0

The Hamiltonians $H_S$ and $H_R$ both implicitly depend on their respective volumes (or confining potential strength). To allow volume exchange between the two systems, you simply impose the constraint $V_R = V_{tot}-V_S$. The joint Hamiltonian is always given by $H_S+H_R$. You can check that in mechanical equilibrium, \$\partial_{V_S} ...

1

Well let's say you weigh 220 lbs. Which translates over to 100 kg. The fall is 50 ft, so about 15.24 meters. The running thing that most people say is that it takes about 5000 Newtons of force to break a human bone, but we know that, this varies. We also know that it is not how hard you hit something that necessarily kills you, it's energy from the impact, ...

1

It's not the fall that kills you. Your chance of survival is 100% :) In regards to the suspected impact after the fall, you will need to expand on the parameters to your question. Divers survive 50ft drops routinely. The elderly are killed from 4 foot drops routinely. I'm sure this wasn't the answer you were looking for, but I think the best answer ...

1

There is an intriguing possibility that the answer is yes, in a very fundamental way! All amino acids (except glycine) come in two chiralities, left-handed and right-handed, related by parity. However, all amino acids used in living beings are left-handed. Evidently, by chance, early in Earth's history, left-handed compounds gained an advantage somehow. ...

3

What happens to photons when they hit our eye? Some of them pass through the iris and are focussed by the lens onto the retina where they are absorbed by rods or cones. where do they end up? Some of them end up absorbed by rods/cones, some by other tissues, some are reflected (c.f. red-eye in photography). why our eye don't get overheated? ...

0

Brain as a biocomputer is far to complex to expect an fully descriptive answer in a form of a forum post. Don't worry, the situation is even more riddled! :) The opinions on the topic of quantum behaviour affecting the perception of reality (and accordingly creation of "reality", but I am touching very metaphysical viewpoint here, which is usually avoided ...

2

The leading answer to this (closed) question gives some good reasons why IR vision did not develop widely across the animal kingdom. To paraphrase, sensing even the near-IR spectrum would require a different type of sensor compared to more or less regular chromophores, and there would be limited evolutionary pay-off for detection. The advantage gained over ...

13

i've programmed some shepard tones and even a voice generator. The human voice can't make that sound for the same reason that a single or even 3 trumbones couldn't make it. if you had 12 trumbones you could conceivably put them on a wheel system so that the pitch of each is increased and when the top one reaches to top is muted and send down to the lowest ...

19

The human voice box produces a fundamental frequency and its harmonics because the mechanism is like that of a relaxation oscillator. However, we have limited control over the relative amplitude of the harmonics (we do have some - that is how we change the "color" of a tone we sing, and the sound of vowels). In order to produce the Shepard scale, you need ...

3

There are definitely some serious scientific efforts going on today trying to explain and incorporate QM in brain processes. The following TED talk is just about that: http://www.ted.com/talks/jim_al_khalili_how_quantum_biology_might_explain_life_s_biggest_questions?c=922691 Other scientists hypothesize that the tiny dendrites or microtubules on neurons ...

2

The 'balloon in a jar' demonstration just illustrates the principle of lung ventilation, but really shouldn't accepted too closely in modeling the dynamics of breathing. In a real lung the only gas-filled space is the space that communicates with the upper ways, and terminates at the other extreme with sac-like structures called alveoli. The space outside ...

0

I think the referenced experiment is interesting but not an exact model of the lungs. But in the "close enough" realm, what's happening is that the movement of the diaphragm (and the ribcage) happens as various muscles act against the external air pressure. Once there's additional volume inside (and assuming no collapsed lung, the interior of your lungs, ...

20

Yes - but only in the sense that all macroscopic processes depend on underlying quantum mechanics at the microscopic scale. No - quantum mechanics is not the best model for describing what happens in the brain. In one sense, the behaviour of a neuron is similar to a quantum process, such as (for example) the decay of an electrically excited or radioactive ...

4

The brain is a de-facto a classical computer as explained in Alanf's answer. However, this then leaves open the possibility that what makes a classical system like our brain or some future AI conscious, could well be related to how quantum mechanics reduces to classical mechanics. One proposal along these lines (that I personally don't find compelling) has ...

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