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1. ### I Why the speed of light is constant?

I always connect it to the Principle of Relativity: the requirement that the equations describing the laws of physics have the same form in all admissible frames of reference. If the laws of physics were actually to vary from one frame of reference to another, then what is physically normal in...
2. ### The beginning of everything?

The bane of theoretical physics is the equivocation that arises when we are trying to communicate novel ideas but the only words we have were coined for older ideas that may be similar, but not identical to the new ideas. The electron is NOT a particle, nor a wave, nor a wave function. It is...
3. ### Is the distance between any object infinite?

This discussion just provoked a thought. General Relativity allows that space and time can be interchanged by motion. This is a continuous function of velocity (itself a continuous variable) as described by the Lorenz transforms. It is this continuity that precludes the 'granularity' of space...
4. ### Is it theoretically possible for a star to orbit a planet?

Imagine two objects on a lever - one large, and one small. The balance point of the lever will be closer to the larger one. The quantities called "moments" must be equal. The "moment" is the mass times it's distance from the balance point: M1 * d1 = m2 * D2 It is the same for stars and planets...
5. ### Is the mass of the universe finite (collection of objects)?

The observable universe has a finite volume. Density is (locally) the ratio of mass to volume. For the mass of the universe to be infinite, the local density of the universe must be (somewhere) infinite. At the location where infinite density is to be found, the curvature of space-time (i.e...
6. ### Where is my calculation of sun angle incorrect?

I could not help but notice that you are using the term "latitude' as an input, but the equations are citing "lattitude" (with a double-t). Are the equations with the problematic results really using "lattitude" as an argument in lieu of "latitude"?
7. ### Why do things have color?

The light you see is the light that gets reflected or scattered of an object. This is not the same as the light that strikes the object because the object absorbs some light. To absorb light, the material of which something is made needs to be able to put the energy of a single light wave...
8. ### Boundary Conditions for Hydrogen Schrodinger Equation

The usual method of separation of variables imposes a 'boundary' condition that the spatial components of the solution are independent of time - i.e. time-invariant. This may be excessive, as the requirement that the final wave function be square-integrable permits wave functions that are...
9. ### Large crater(s) in Siberia

Just a couple of pieces of data from a chemist: when flammable gases mix with air they may or may not form an explosive mixture. Too much gas (above the Upper Explosive Limit) and the ignited gases starve for oxygen to support combustion. Too little gas (below the Lower Explosive Limit) and the...
10. ### Center of gravity of a 3d triangle using weight

In plane geometry there is a theorem that the COM of a triangle is where the geometric medians meet: http://en.wikipedia.org/wiki/Median_%28geometry%29 This can be extended to non-uniform mass distribution. Calculate the fulcrum point between each pair of points where load indicators are...
11. ### Here's an idea: let people "work off" their criminal records

The entire purpose of any government, and by inheritance its sub-divisions such as the 'Judicial branch,' is (or at least should be) to protect the public. In this respect, there should be two major classes of crimes - those that harm people, and those that deprive people of the use of their...
12. ### Pycnometer equation

The second term: - \frac{ \rho_a m_b}{ \rho_b} is the correction to the weight of the bottle for the buoyancy of air. In the most precise work, this must be determined using air temperature, pressure, and humidity. This can amount to a correction of a few parts per million.
13. ### Is our universe inside a blackhole?

The "No-Hair" Theorem applies. It is a mathematical statement that demonstrates that a BH can only have a very limited number of properties, and no internal structure of any kind. Basically, a BH is a quantum mechanical object on a cosmic scale, with charge, mass, and angular momentum, but no...
14. ### How far from Event horizon are you safe?

The determinant would be the tensile strength of the object. As it nears the BH, the gravitational gradient (the difference between the strength of gravity on end of the object versus the other) will result on gravity pulling harder on the near ('downhill') end harder than on the far...
15. ### Flying disk - Why not

Aerodynamics involves countering weight with lift by 'pushing down' on air, which pushes 'up' on the vehicle according to Newton's Third Law. How you push down on the air makes all the difference. The further from the leading edge of an airfoil you are, the less efficient will be the...
16. ### Product to prevent car hyperthermia

One driver has a simple solution. She removes her shoes and places them on the back seat before starting the vehicle. To leave the vehicle she has to retrieve her shoes - from beside the child seat.
17. ### Difficult time understanding altruism

Look up "Tit for tat" in Wiki. It is a simple and effective strategem in game theory for balancing cooperation (altruism) with retaliation (being cheated).
18. ### Isomer of butene

The names seems to be confused about exactly which carbon on the propene skeleton is the #1 carbon. By convention, the #1 carbon in propene is the one on the end that has the double bond to its neighbor. That said, you have attached a substituent group (methyl) to the #3 carbon, not the #1...
19. ### Isomer of butene

Putting the methyl on the #1 carbon of the propene makes the carbon skeleton 4 carbons long and linear - the same as 2-butene.
20. ### Difficult time understanding altruism

My thinking is that altruists are generally better company, and have less trouble attracting mates.
21. ### Alcohol and dehydration

Hangover headaches are attributed to dehydration of the brain. They can be prevented by rehydration before bed. The weakest alcoholic beverage I have ever had was Colorado's 'famous' 3.2 beer - 3.2% alcohol (6.4 proof). It is so weak it is legal to serve to minors. It can still give you a...
22. ### Richard Feynman - Proportion

(W)e are the first life forms on this 'mindboggingly, discombabulatingly, bamboozingly insignificant speck of dust' (meaning 'Earth') to be able to realize this.
23. ### Richard Feynman - Proportion

The 'mindboggingly, discombabulatingly, bamboozingly' simple truth is that "God" = physics, creator of all things, font of Universal Law. Non-equilibrium thermodynamics is how life was created, and evolution is how life has diversified. We humans are 'special' to God because we are the...
24. ### Cycle of blue moons from year 0

http://www.timeanddate.com/calendar/moonphases.html?year=1&n=0 shows full moons for UTC, with a full moon on 28 Jan at 00:44 http://www.timeanddate.com/calendar/?year=1&country=1 shows a full moon in the US on 27 Jan (time not specified because there are several US time zones) 28 Jan 00:44...
25. ### Doubt of Mizar and Alcor

The wikipedia article "Big_Dipper" shows that in different cultures the asterism is identified as 7 persons (sages or gods), a canoe, a wagon, a plow, a bear, a dipper, a coffin with mourners, a butcher's cleaver, a drinking gourd, a she-bear followed by 3 cubs/hunters, and a Fisher cat (weasel).
26. ### Turning a model car with no steering.

Different speeds for each wheel will steer the car. Omni wheels will completely eliminate wear from lateral motion without the need for a conventional differential or accommodations for Ackerman steering geometry.
27. ### How Large Can a Planet be and Still Have Earth's Mass?

Does a hypothetical planet HAVE to be stone? Low density solids include H2O (917 kg/m3) - NH3 (817 kg/m3) - CH4 (423 kg/m3) - methane clathrate (900 kg/m3) - ammonium hydroxide (880 kg/m3) - all of which can be abundant enough in planetary space to form an earth-mass planet. These can be taken...
28. ### How Large Can a Planet be and Still Have Earth's Mass?

Newton's Law of Gravitation: F = G*M1*M2/r^2 The surface acceleration of a planet (M2) is: g = G*m2/r^2 but m2 = (4/3)*pi*r^3*d where d is the average density of the planet so g = (4/3)*G*pi*r*d Choose your favorite g and d and solve for r.
29. ### How Large Can a Planet be and Still Have Earth's Mass?

I would call that a 'comet.'
30. ### Milankovitch Cycles and change of seasons

There are several 'years' of astronomical importance. The sidereal year (avg 365.256363004 mean solar days) is the time it takes for the sun to apparently move 360° relative to the (so-called 'fixed') stars. The tropical year (avg 365.24219 days) is the time it takes the sun to to apparently...
31. ### Is constant planetary alignment (syzygy) possible ?

"Constant" is a relative term. For celestial mechanics, where time is reckoned in billions or years, a constant syzygy for a three-body problem (any of the 5 Lagrange solutions to the gravity potential well problem) can only exist if 2 of the bodies are point masses. Otherwise tidal forces...
32. ### Larger molecules have smaller HOMO-LUMO Gaps?

When it comes to chemistry, in general there are no reliable generalities.
33. ### Is there a physical explanation for why we can't see certain colors?

The human lens normally absorbs most UV-B and some UV-A radiation. When I had cataract surgery my natural carbon-based lenses were replaced with silicone lenses that are more transparent to the UV. Most of the UV-A and some UV-B gets through these lenses (and my optical humors) and stimulates...
34. ### Separation of variables to solve Schrodinger equations

Mathematically, separation of variables works best when the variables are orthogonal. In static problems Time is always orthogonal to the spatial variables. In dynamic problems (time-dependent) the separability occurs when the chosen coordinates represent represent independent modes of...
35. ### Separation of variables to solve Schrodinger equations

Technically, a time-dependent field is not a 'potential' field. The S equation is soluble by separation of variables because the equation can be arranged so that the time-dependence is entirely one one side of the = sign. The other side of the = sign has no time-dependence. Mathematically, this...
36. ### Why search for exoplanets

Because Education is always preferable over Ignorance. Because the more we learn about planets, the more we can understad about OUR planet. Because there is almost certainly other intrelligent life out there, and the laws of strategy and tactics tell us Offense (whomever contacts the other...
37. ### Calculating Expected Value: A Multiple Choice Quiz Question

According to the Texas Department of Education Trilingual English/Spanish/Ebonics Program, "two 'n' dos be fo".
38. ### Glass silvering phenomena and further studies upon reflective layers

Reflection of visible light at the interface between the glass rod and the metal in NOT total internal reflection. That can only occur when moving from an optically denser medium into a less dense one (i.e., n1 > n2). Wiki has a nice little blurb on the Complex Index of Refraction...
39. ### One 3rd degree equation with two variables. Can it be a solution?

If x = y, then (x-y) = 0 and you have a set of solutions (a straight line). If x <> y, then your other solutions satisfy x^2 + xy + y^2 = 727 (an ellipse).
40. ### Glass silvering phenomena and further studies upon reflective layers

Fermat's Principle and Snell's Law (the same thing, really) dictate that you can only get total internal reflection if the refractive index on the outside of the rod's surface is LOWER than the index on the inside. http://en.wikipedia.org/wiki/Total_internal_reflection#Critical_angle
41. ### Wave Function Collapse and Entropy

Entropy is a statistical concept: S = k ln W (to quote Bolzmann) wherein the W irepresents the number of possible microstates corresponding to the macroscopic state of a system. For a single particle, W = 1, so S = 0. I have always found it useful to recall that mathematically a single...
42. ### Experimental calculated values and Uncertainties

I use the ASTM protocol for rounding (5's round to an even number: .15 rounds up while .25 rounds down). By that rule your 0.3765 rounds to 3 sig figs as 0.376, 0.1274 rounds to 3 sig figs as 0.127, 0.69897 rounds to 2 sig figs as 0.70, and 0.0789 rounds to 2 sig figs as 0.08.
43. ### Mason-Weaver equation and time dependend solutions

The concept of "settling velocity", the terminal velocity of a particle in a medium exhibiting non-zero bouyancy (either positive or negative), might be useful here. Terminal velocity is dependent on the size (radius) of the particle, the difference in density, and the viscosity of the fluid.
44. ### If entropy is a state function, how can it keep on increasing?

Plot the state of the system using Entropy and Temperature as coordinates.
45. ### Artificially increased rainfall ?

Any child who has lived on the plains can tell you that thunderstorms are triggered by updrafts - humid air rising in "thermals", usually over warm dry ground. The circulation develops from the Coriolis forces applied to the updraft by the rotation of the earth. Other children raised in...
46. ### Artificially increased rainfall ?

"This "lake effect" could overwhelm flood defences which are often built without taking it into account." is the claim. The reservoir IS the flood defence. I would like to see how the Law of Conservation of Matter is circumvented here - a reservoir cannot hold enough water that the evaporation...
47. ### Will there ever be a 2nd ice age?

In other words, "we don't know." It could start tomorrow, it may not start for another 50,000 years. If the Yellowstone caldera erupts or some other VERY large volcanic event blows, we could have a mini-ice age precipitated by the volcanic dust, ash, and sulfur injected into the stratosphere...
48. ### Why is KE = 0 at escape speed?

The spaceship has both potential energy (due to its position in the Earth's gravitational field) and kinetic energy (due to its speed). If the potential energy (negative) is greater in magnitude that its kinetic energy (positive), then the Total Energy is negative and the spaceship is trapped...
49. ### Some questions for want of answers:

1. How long does a black hole exist? Black holes grow as the acquire mass from infalling material and shrink slowly through Hawking radiation. A BH will 'evaporate' when it can no longer gain mass. How long that takes will of course depend on the mass of the BH and the rate of evaporation...
50. ### Angular momentum of rod

In the second link the 'bubbles' are hot links. Navigate through "Mechanics", then "Rotation", then "Moment of Inertia". Click on "Common Forms" for Enlightenment!