Whats the speed of dark ?

The speed of dark is outstripped only by the speed the Landlord of my local pub can remove money from his patrons - before serving the beer !
Oh, and we British have the correct vocabulary, and speak correctly - give or take the odd region ..........................

First, I think we should apply for a grant - someone out there must be willing to throw money at a project such as this.

I propose that we measure the the speed of cold instead of the speed of dark. If the speed of heat is the same as the speed of light, the speed of cold should match the speed of dark....

Anyone have a good watch and a tape measure?

Cheers,



Dana

Don't know - my watch has stopped due the cold, and i can't see to find a tape measure, as it's bl**dy dark in here !

Just found out that some members are more in the dark than others....

Yes, some are rather ... er.... dusky .......................

Exactly, in this case the dark was faster than the light. What does that tell you?

People are stupid?

Sorry Chaps but cold, like dark is NOT a physical entity and as such has NO speed or rate though we can measure a rate of transfer. Cold like dark is the absence of a measurable physical quantity. In the case of cold we are looking at the absence of heat which is the total Kinetic Energy of all particles in a system. Cold is also a relative term so that an object is only cold in comparison to a second object which has more energy, i.e. is hotter than the first object.
Temperature is essentially not directly measurable except in theory. It is the AVERAGE Kinetic Energy of all particles in a system. Thermometers do NOT actually measure temperature. They actually measure the effect temperature has on objects. Most things expand when heated and contract when cooled. Heated mercury or alcohol expand within their glass tubes and we measure that expansion or when cooled contract. A coiled metal spring expands as the temperature rises moving a pointer on a dial to a higher position. The reverse when cooled. Thus Heat and Temperature are not the same and this difference can lead to some very strange counterintuitive comparisons. Consider a white hot needle at 4000C and a 10 kg block of Ice at -5C. They have vastly different temperatures but the 10 kg ice block has vastly more heat content.
Heat pumps move the physical entity Heat from one spot to another. So there's a box in your kitchen that contains a heat pump. The pump removes the heat from inside the box and transfers it into the kitchen. You might also have heat pumps that sit in a window that pump the heat out of your house or perhaps a large reversible pump that can pump heat in either direction. Out during the summer and in during the winter

A platinum -platinum/rhodium thermocouple produces an induced current directly proportional to the temperature at the joint. A thermographic camera when correctly calibrated for emissivity gives a direct temperature reading accurate to less than 1% even in a cracking furnace running at 1100C.

In either case you are not directly determining the temperature but the change induced by the Kinetic Energy of the objects particles.
To directly measure an objects temperature you would have to locate every particle, measure each particles KE, and then average them. Since this is not physically possible we measure some physical change that is directly measurable and proportional like expansion/contraction, density changes, emission of electrons or photons as electrons transition energy levels within atoms

mikewint said:

In either case you are not directly determining the temperature but the change induced by the Kinetic Energy of the objects particles.
To directly measure an objects temperature you would have to locate every particle, measure each particles KE, and then average them. Since this is not physically possible we measure some physical change that is directly measurable and proportional like expansion/contraction, density changes, emission of electrons or photons as electrons transition energy levels within atoms

Click to expand...

But that is precisely what thermography does on a black box emitter. Temperature is an average KE, a measure of an individual molecule or atom's velocity and from that a calculation of its KE is just that, it isn't a temperature.

mikewint said:

Sorry Chaps but cold, like dark is NOT a physical entity and as such has NO speed or rate though we can measure a rate of transfer. Cold like dark is the absence of a measurable physical quantity. In the case of cold we are looking at the absence of heat which is the total Kinetic Energy of all particles in a system. Cold is also a relative term so that an object is only cold in comparison to a second object which has more energy, i.e. is hotter than the first object.
Temperature is essentially not directly measurable except in theory. It is the AVERAGE Kinetic Energy of all particles in a system. Thermometers do NOT actually measure temperature. They actually measure the effect temperature has on objects. Most things expand when heated and contract when cooled. Heated mercury or alcohol expand within their glass tubes and we measure that expansion or when cooled contract. A coiled metal spring expands as the temperature rises moving a pointer on a dial to a higher position. The reverse when cooled. Thus Heat and Temperature are not the same and this difference can lead to some very strange counterintuitive comparisons. Consider a white hot needle at 4000C and a 10 kg block of Ice at -5C. They have vastly different temperatures but the 10 kg ice block has vastly more heat content.
Heat pumps move the physical entity Heat from one spot to another. So there's a box in your kitchen that contains a heat pump. The pump removes the heat from inside the box and transfers it into the kitchen. You might also have heat pumps that sit in a window that pump the heat out of your house or perhaps a large reversible pump that can pump heat in either direction. Out during the summer and in during the winter

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Sorry Mike,

Perhaps I needed a little icon with its tongue punching a hole through its cheek!

Cheers,


Dana

Dana Bell said:

First, I think we should apply for a grant - someone out there must be willing to throw money at a project such as this.

I propose that we measure the the speed of cold instead of the speed of dark. If the speed of heat is the same as the speed of light, the speed of cold should match the speed of dark....Anyone have a good watch and a tape measure?

Cheers, Dana

Click to expand...

I'm up for the challenge. I'll need a government grant in the amount of random renewable millions, 2 assistants: one blonde, one red-head, a lab overlooking the French Riviera and no means of communication what so ever. Estimated time of completion.................

pbehn said:

Temperature is an average KE

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Yes exactly so as long as we/you/I understand that an AVERAGE is a total SUM of all things divided by the number of things that were summed.
The AVERAGE grade on an exam is the SUM of all individual scores divided by the number of scores averaged. Statistically we look at MEAN - MEDIAN - MODE. The MEAN is the average score - MEDIAN is the middle point - Mode is the most often occurring score.

pbehn said:

a measure of an individual molecule or atom's velocity and from that a calculation of its KE

Click to expand...

No, not exactly. Going back to the idea of AVERAGE there has to be more than one and the fewer the total number the less valid the average value becomes. Two coin tosses could easily both be heads or tails. The average is then 100% heads or 100% tails totally invalid. The idea of AVERAGE is a mathematical construct and as such may not represent a physical reality. Take a room filled with 100 people. 50 weigh 100lbs and 50 weigh 200lbs. The average weight is 150lbs yet no one in the room weighs the average of 150lbs
Let's take a sample of a gas as an example. If I were to place 32.0 grams of pure Oxygen gas in a container and ask you to DIRECTLY find the temperature of the gas you would be tasked with individually locating 6.023 X 10^23 molecules - measuring the speed of each one to determine each ones KE - then summing all 6.023 X 10^23 KEs - and then dividing by 6.023 X 10^23 to find the average, which would be just that an KE value in Joules (assuming MKS units). So YES it is not directly a Celsius/Fahrenheit/ Kelvin value. But Kelvins are directly relatable to KE since zero Kelvins or Absolute Zero is zero motion and thus zero KE. Kelvins can then easily be converted to Celsius and Fahrenheit degrees.

pbehn said:

But that is precisely what thermography

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Therography performed with a thermographic camera determines the wavelength/frequency of long wave (9000 - 14,000nm) infrared radiation. Through internal computer algorithms colors are assigned giving a visual depiction of the temperature degrees and their distribution within the image. This is possible because the frequency/wavelength of a photon is determined by its energy content. Thus as temperature increases the photons radiated also increase their energy content and have shorter wavelengths and higher frequencies. BUT this simplistic scheme is complicated by the fact that everything "seen" by the IR camera has a temperature thus there are multiple IR sources emitting, transmitting, reflecting, and absorbing. The interpretation of all this data is controlled by the cameras mathematical algorithms.
A further complication is the objects emissivity. Two objects in the cameras view at the same physical temperature may show different different images if they have different emissivity. Objects with a high emissivity will appear hotter than another object with lower emissivity even though both are at the same physical temperature.

In any case my point remains valid. You are NOT directly measuring temperature. You are detecting/measuring photons emitted because of a vibrational/rotational mode of the atom/molecules of an object determined by its temperature (average KE) though no particle of the object may actually be at that KE value

Just joshing mike. I used thermography equipment in Saudi Arabia with computer software to review results, it is FFFfffing incredible what it can do, from finding leaks in canals to overheating circuits (+5C higher) and thinning pipes in furnaces, it requires very little expertise to use it, just in interpreting results.

But what about dark matter Mike?

Marcel said:

But what about dark matter Mike?

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It has an emissivity value greater than 0.91.

Marcel said:

But what about dark matter

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At the present time along with Dark Energy we have "pie in the sky" theorems attempting to explain the accelerating expansion of the universe and the retention of a galaxy's peripheral suns.
Back in the early 1950s astronomers expected that stars near the center of a galaxy would have to travel faster than stars in the periphery. Just like Mercury has a higher orbital velocity (being nearer the sun) than the Earth whose orbital velocity (nearer the sun than) is higher than Uranus. Instead the observed measured velocities of both were the same. Calculating the total mass of all observable matter in the galaxy at such velocities the peripheral suns should fly off into space since the total mass of the observable matter in the galaxy did not provide sufficient gravitational force to hold them in place.
**N.B.** Gravity is a fictional force like Centrifugal Force but it offers a simple explanation so I'll pretend that it is real and use the term.
The only explanation in keeping with known physical laws was that the galaxy must contain matter that could not be observed, i.e. DARK Matter meaning that it did not radiate any detectable forms of energy but being matter it did generate a gravitational field. Black Holes themselves also do not radiate BUT at their edges an accretion disk forms which does radiate as matter crosses the event horizon and falls into the hole. To generate sufficient gravitational force to retain the peripheral sun meant that 80% of the galaxies total mass must be dark. More evidence came in in the form of gas movements within elliptical galaxies which again required the presence of much more mass than that observed and the movements of clusters of galaxies which should fly apart if the only mass present was that which could be observed.
Recently about Dragonfly 44 a galaxy as large as the Milky Way was discovered about 300 million LY from Earth. It emits about 1% the amount of light that the Milky Way does and has few observable stars within it that move very quickly. To keep these stars within the galaxy requires a LOT more matter, present belief is that it is 99% Dark Matter.
Now there do exist other possibilities such as very dim brown dwarf stars, neutrino stars. and super massive black holes but presently most feel tat they are not present in sufficient quantity to make up the missing mass.
SO...off to Neverneverland. Dark matter is not composed of regular baryonic (electrons, neutrons, protons) matter but of non-baryonic WIMPs (Weakly Interacting Massive Particles) with 10 to 100 times the mass of a proton. They even have a name: the Neutralino. Neutralinos are slower than, more massive than, a regular neutrino but show the same very weak interaction with regular matter.
**N.B.** Besides baryons (made of Quarks) there are LEPTONS, point particles with no internal structure. The best known is the electron. In addition there is the MUON and the TAU. All three are electrically charged and Symmetry requires 3 non-charged the 3 NEUTRINOS (the elusive neutrino was predicted back in 1931 but wasn't discovered until 1959. Neutrinos come in three flavors the electron-neutrino. the muon-neutrino discovered in 1962, and the tau-neutrino in 2000.) Dark Mater Neutralino fans propose a fourth flavor the Sterile or inert neutrino. The 3 known types oscillate in flavor as they zip along. The Sterile neutrino could only be produced when one of the other flavors morphs into it. Sterile neutrinos have 10 - 100 times the mass of the other 3 and only interact with ordinary matter through gravity hence their involvement in Dark Matter.
All of the above having been said, at the present date NO direct evidence of Dark Matter has ever been found.
More Pie in the Sky....DARK ENERGY
While Dark Matter makes up 80% of the matter in the universe it only makes up 25% of its composition. 75% of the universe is, yup you guessed it....DARK ENERGY.
Again turning to cosmology. After the Big Bang the Universe began expanding. Theory was that eventually gravity would slow the expansion, stop it, and then cause it to collapse and eventually go BANG again. Others theorized a Thermal Death for the universe where the expansion would go slower and slower and slower approaching but never reaching zero. Then starting in the 1990s astronomers studying distant supernovas determined that neither was happening, instead the expansion was accelerating going faster than it had in the past. This could only occur if a force greater than gravity were present driving the expansion faster and faster, i.e. Dark Energy. Modern Theory terms this QUINTESSENCE and ranks it as the Fifth Fundamental Force (Gravity - Electromagnetism - strong nuclear - weak nuclear).
This means that while energy is supposed to have a source either matter or radiation, dead empty space with all matter and radiation removed nonetheless contains a residual energy - QUINTESSENCE which on a cosmic scale results in a force sufficient to drive the accelerating expansion of the universe. Einstein's Theory of General Relativity has long since given a way to describe the physics of the large but fails to describe the physics of the small (atom sized). For that we turn to Quantum Mechanics which describes how these small particles behave and interact but fails above the size of an atom. If/when these two theories are reconciled a natural explanation for Dark Energy will emerge.
So as weird as it seems the Universe seems to consist of 4% visible matter - 22% Dark Matter - and 74% Dark Energy. Or simply put we know very little about 96% of our universe

Come to the dark side - we have speed.............. BwAHAAHAA !

It's getting to technical to keep up....