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Serious blow to dark matter theories?

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Posted (edited)

The most accurate study so far of the motions of stars in the Milky Way has found no evidence for dark matter in a large volume around the Sun. According to widely accepted theories, the solar neighbourhood was expected to be filled with dark matter, a mysterious invisible substance that can only be detected indirectly by the gravitational force it exerts. But a new study by a team of astronomers in Chile has found that these theories just do not fit the observational facts. This may mean that attempts to directly detect dark matter particles on Earth are unlikely to be successful.

Serious blow to dark matter theories? New study finds mysterious lack of dark matter in Sun's neighborhood

If dark matter doesn't exist you can say bye bye to enhanced greenhouse gas theory.

Edited by BFB

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I would assume this dark matter would be outside of the sun's reach.

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If dark matter doesn't exist you can say bye bye to enhanced greenhouse gas theory.

What does ``enhanced greenhouse gas theory'' have to do with dark matter?

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This is one of those concepts that most of what we assume to be true about physics rather depends on, doesn't it.

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This is one of those concepts that most of what we assume to be true about physics rather depends on, doesn't it.

It isn't that serious. Dark matter and dark energy have a major bearing only on cosmology and astrophysics. If dark matter doesn't exist then either:

  • General Relativity is wrong at large scales, or
  • General Relativity cannot be linearized at large scales, or
  • Our observations of distant galaxies are misinterpreted.

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What does ``enhanced greenhouse gas theory'' have to do with dark matter?

It came out wrong. We just have to re-right the theory in respects of Earth's radiative heat transfer.

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It came out wrong. We just have to re-right the theory in respects of Earth's radiative heat transfer.

Why? I've yet to come across an explanation of Earth's heat transfer using dark matter.

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Why? I've yet to come across an explanation of Earth's heat transfer using dark matter.

Because dark matter is an energy source?

First, its hypothesized that dark matter contributes about one megawatt of energy to Earth.

Second, if dark matter is an illusion, space isn't cold and there would be no "heat loss blanket effect" - which would be a major blow to the AGW theory hence a lot of rewriting needs to be done.

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Because dark matter is an energy source?

First, its hypothesized that dark matter contributes about one megawatt of energy to Earth.

Second, if dark matter is an illusion, space isn't cold and there would be no "heat loss blanket effect" - which would be a major blow to the AGW theory hence a lot of rewriting needs to be done.

First, dark matter is not an energy source in any sense other than that it produces a gravitational field.

Second, 1 megawatt of energy? How is such a tiny amount even measurable?

Third, how does the existence of dark matter have any influence on whether or not space is cold? Are you confusing dark matter with dark energy?

Fourthly, space is cold. We've been up there. We've measured it. We know the average temperature of space. This is completely independent of whether or not dark matter or dark energy exists.

And finally, Venus has the highest average surface temperature of any planet in the solar system, but Mercury is the closest to the Sun. If there is no ``heat blanket effect'' how does this occur?

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Because dark matter is an energy source?

First, its hypothesized that dark matter contributes about one megawatt of energy to Earth.

Second, if dark matter is an illusion, space isn't cold and there would be no "heat loss blanket effect" - which would be a major blow to the AGW theory hence a lot of rewriting needs to be done.

Sorry, but where are you getting this?

Dark matter or not, space is cold (around 3 Kelvin), this has been verified. Still not seeing the connection between dark matter and heat loss.

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Posted (edited)

First, dark matter is not an energy source in any sense other than that it produces a gravitational field.

Second, 1 megawatt of energy? How is such a tiny amount even measurable?

Third, how does the existence of dark matter have any influence on whether or not space is cold? Are you confusing dark matter with dark energy?

Fourthly, space is cold. We've been up there. We've measured it. We know the average temperature of space. This is completely independent of whether or not dark matter or dark energy exists.

And finally, Venus has the highest average surface temperature of any planet in the solar system, but Mercury is the closest to the Sun. If there is no ``heat blanket effect'' how does this occur?

First incorrect. Any moving* particle creates the energy form called heat.

Second, i understand what you are saying.

Third, I think so, my mistake*.

No particles, no temperature. So to keep space "cold" we need some slow moving particles, And after realizing my mistake with dark energy - dark matter, dark energy needs to exist if you want to valid the COBE measurements.

and finally did i say greenhouse gases didn't exist? I said if space didn't have a temperature, there would be nothing called blackbody radiation hence the reason why we needed to rewrite our theory.

But all this doesn't really matter as i confused dark matter with dark energy.

* - EDIT

Edited by BFB

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Sorry, but where are you getting this?

Dark matter or not, space is cold (around 3 Kelvin), this has been verified. Still not seeing the connection between dark matter and heat loss.

See my post above was confusing dark matter and dark energy.

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I understand that you mistook dark matter for dark energy. That is an easy mistake to make.

However there are several mistakes in your post:

First incorrect. Any moving* particle creates the energy form called heat.

Not really. ``Heat'' is random kinetic motion in a statistically significant ensemble of particles.

Individual particles have no heat.

I believe space is a sufficient vacuum, even in gas nebulae, to seriously stretch the thermodynamic definition of heat.

No particles, no temperature. So to keep space "cold" we need some slow moving particles

Not really. At least, not if by ``particles'' you are referring only to fermions.

An electromagnetic spectrum can have disorder that is equivalent to heat. Such a spectrum exists in space.

The ``temperature'' of space is primarily the average energy of photons in space; namely the cosmic microwave background which, as Rlyeh pointed out, has an energy that is equivalent to a temperature of 3 K.

This has more to do with statistical mechanics than pure thermodynamics, and it does not mean that the temperature of a radiation bath is in all cases equivalent to the thermodynamic temperature of a physical object.

But they are in some sense equivalent.

I said if space didn't have a temperature, there would be nothing called blackbody radiation hence the reason why we needed to rewrite our theory.

Blackbody radiation is a consequence of ``black bodies''. I don't see what this has to do with space. Space is not a physical object.

I guess I was sloppy by suggesting that ``space has a temperature'', I suppose a more correct statement would be that ``the electromagnetic radiation in space is sufficiently disordered to possess a temperature''

------

But I still don't see what AGW has to do with dark energy.

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Posted (edited)

You got my attention sepulchrave, i like where this is going.

I understand that you mistook dark matter for dark energy. That is an easy mistake to make.

However there are several mistakes in your post:

Not really. ``Heat'' is random kinetic motion in a statistically significant ensemble of particles.

Individual particles have no heat.

I believe space is a sufficient vacuum, even in gas nebulae, to seriously stretch the thermodynamic definition of heat.

Every particle with a degree of freedom has a temperature. Dark matter needs to at least have one degree of freedom, if not how do you then explain its existence?

Not really. At least, not if by ``particles'' you are referring only to fermions.

An electromagnetic spectrum can have disorder that is equivalent to heat. Such a spectrum exists in space.

The ``temperature'' of space is primarily the average energy of photons in space; namely the cosmic microwave background which, as Rlyeh pointed out, has an energy that is equivalent to a temperature of 3 K.

This has more to do with statistical mechanics than pure thermodynamics, and it does not mean that the temperature of a radiation bath is in all cases equivalent to the thermodynamic temperature of a physical object.

But they are in some sense equivalent.

I'm a student in the field of atmospheric science. When we covered thermodynamics we were taught that electromagnetic waves are a part of thermodynamics called radiation. Radiation is when heat is transferred through electromagnetic waves.

So are you are saying the background noise isn't electromagnetic waves?

Blackbody radiation is a consequence of ``black bodies''. I don't see what this has to do with space. Space is not a physical object.

I guess I was sloppy by suggesting that ``space has a temperature'', I suppose a more correct statement would be that ``the electromagnetic radiation in space is sufficiently disordered to possess a temperature''

------

But I still don't see what AGW has to do with dark energy.

Sorry sepulchrave, blackbody HAHA. :rolleyes: This is what happens when you type to fast, i thinking of background radiation and not blackbody radiation.

Okay let me see if you get it now.

If dark matter and dark energy was just an illusion. Photons wouldn't have a good chance of escaping directly back into space since "space" itsself was just an illusion. It was my ignorance in the field of astronomy, which made me capable of making that statement. Sorry for that.

Edited by BFB

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Every particle with a degree of freedom has a temperature. Dark matter needs to at least have one degree of freedom, if not how do you then explain its existence?

I disagree with this statement. Abstractly, temperature is a measure of randomness in a degree of freedom - if you have only a single particle in free space there is no inherent randomness (in the particle's time-like evolution - not to be confused with probabilistic wavefunction collapse under measurement).

You need a collection of particles to have a sensible definition of temperature - especially thermodynamic temperature.

I would assume that dark matter would have some inherent randomness, and therefore a temperature, but most theories of dark matter that I am familiar with suggest that it is decoupled from the electromagnetic spectrum - and therefore could not radiate heat in the conventional sense.

I'm a student in the field of atmospheric science. When we covered thermodynamics we were taught that electromagnetic waves are a part of thermodynamics called radiation. Radiation is when heat is transferred through electromagnetic waves.

So are you are saying the background noise isn't electromagnetic waves?

I agree that background noise is electromagnetic waves.

If dark matter and dark energy was just an illusion. Photons wouldn't have a good chance of escaping directly back into space since "space" itsself was just an illusion.

I don't know about that - photons obviously escape from the Sun to reach Earth. I don't think dark matter or dark energy have any direct effect on electromagnetic fields.

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Miles Mathis has some insights, for anyone interested:

milesmathis.com lostmass

..

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Miles Mathis has some insights, for anyone interested:

milesmathis.com lostmass

..

I briefly read some of his papers, and I don't think he has any ``insight'' on the issue.

He is quite good at misinterpreting simple concepts though.

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Posted (edited)

I disagree with this statement. Abstractly, temperature is a measure of randomness in a degree of freedom - if you have only a single particle in free space there is no inherent randomness (in the particle's time-like evolution - not to be confused with probabilistic wavefunction collapse under measurement).

You need a collection of particles to have a sensible definition of temperature - especially thermodynamic temperature.

I would assume that dark matter would have some inherent randomness, and therefore a temperature, but most theories of dark matter that I am familiar with suggest that it is decoupled from the electromagnetic spectrum - and therefore could not radiate heat in the conventional sense.

I disagree with this statement sepulchrave :P

inherent randomness? As soon as a particle has degree of freedom you either have translational kinetic energy, rotational kinetic energy or vibrational kinetic energy i.e a temperature.

A single particle in free space* should at least have 3 degrees of freedom. Therefore should at least have translational kinetic energy, if you dont want to break the law of physics.

But then as you say shouldn't that be detectable? So dark matter breaks the current known laws of physics, right?

* - edit

Edited by BFB

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Posted (edited)

Astronomers from the University of Bonn in Germany have discovered a vast structure of satellite galaxies and clusters of stars surrounding our Galaxy, stretching out across a million light years. The work challenges the existence of dark matter, part of the standard model for the evolution of the universe. PhD student and lead author Marcel Pawlowski reports the teams findings in a paper in the journal Monthly Notices of the Royal Astronomical Society.

Do the Milky Way's companions spell trouble for dark matter?

Edited by BFB

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inherent randomness? As soon as a particle has degree of freedom you either have translational kinetic energy, rotational kinetic energy or vibrational kinetic energy i.e a temperature.

Again, I disagree. Neither kinetic, rotational, nor vibrational energy implies a temperature. The energy contained in collision-less translational or rotational modes, or coherent vibrational modes does not transfer across boundaries in the same manner as ``heat energy''.

In statistical mechanics temperature is defined as the logarithm of the number of microstates that correspond to the same macrostate, in other words the number of ways a given amount of energy can be arranged in an ensemble of particles. Without a statistically significant number of particles there is no thermodynamic temperature.

Internal degrees of freedom are related to temperature (namely the heat capacity of an ensemble), but the existence of these degrees of freedom does not imply that the ensemble has a meaningful temperature.

For single particles each arrangement of energy corresponds to a different overall behaviour; there is no sensible definition of temperature.

Temperature and heat energy are emergent properties of a large number of particles.

A single particle in free space* should at least have 3 degrees of freedom. Therefore should at least have translational kinetic energy, if you dont want to break the law of physics.

But then as you say shouldn't that be detectable? So dark matter breaks the current known laws of physics, right?

Dark matter is hypothesized to only interact via gravitational force. That is why it is ``dark''. An ensemble of dark matter would have a temperature, but it would be very difficult to transfer any heat energy to or from an ensemble of regular matter since the main thermodynamic and chemical force for regular matter is electromagnetism.

Since dark matter is presumably very sparse it may be difficult to define a meaningful temperature, and it almost certainly would be much lower than the 3 K of space.

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Again, I disagree. Neither kinetic, rotational, nor vibrational energy implies a temperature. The energy contained in collision-less translational or rotational modes, or coherent vibrational modes does not transfer across boundaries in the same manner as ``heat energy''.

In statistical mechanics temperature is defined as the logarithm of the number of microstates that correspond to the same macrostate, in other words the number of ways a given amount of energy can be arranged in an ensemble of particles. Without a statistically significant number of particles there is no thermodynamic temperature.

Internal degrees of freedom are related to temperature (namely the heat capacity of an ensemble), but the existence of these degrees of freedom does not imply that the ensemble has a meaningful temperature.

For single particles each arrangement of energy corresponds to a different overall behaviour; there is no sensible definition of temperature.

Temperature and heat energy are emergent properties of a large number of particles.

Dark matter is hypothesized to only interact via gravitational force. That is why it is ``dark''. An ensemble of dark matter would have a temperature, but it would be very difficult to transfer any heat energy to or from an ensemble of regular matter since the main thermodynamic and chemical force for regular matter is electromagnetism.

Since dark matter is presumably very sparse it may be difficult to define a meaningful temperature, and it almost certainly would be much lower than the 3 K of space.

Sepulchrave before I move on and explain why your disagreement doesn't hold up i would like to ask you 2 questions.

1. Heat and temperature are two different things. I'm sure you know that. But then you say this: Neither kinetic, rotational, nor vibrational energy implies a temperature. The energy contained in collision-less translational or rotational modes, or coherent vibrational modes does not transfer across boundaries in the same manner as ``heat energy''.

You do know what defines temperature right? Its the particle speed. No transfers are needed! Do you agree with this?

2. Regarding degrees of freedom. What do you define as a meaningful temperature? I simply said EVERY particle which has a degree of freedom has a temperature. First you denied this, now you are saying its not meaningfull! And i totally disagree with that statement. Any temperature is meaningfull and you should know that if you understand physics. Do you agree with this?

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1. Heat and temperature are two different things. I'm sure you know that. But then you say this: Neither kinetic, rotational, nor vibrational energy implies a temperature. The energy contained in collision-less translational or rotational modes, or coherent vibrational modes does not transfer across boundaries in the same manner as ``heat energy''.

You do know what defines temperature right? Its the particle speed. No transfers are needed! Do you agree with this?

I do not agree with that statement at all.

The temperature of an ideal gas is defined as the average kinetic energy of the molecules of that gas. In (and only in) this case can particle speed be related to temperature. This situation requires not only ideal, Maxwellian particles, but also a statistically significant quantity of those particles.

Not only that, but average particle speed is only a measure of temperature when it is statistically random. Otherwise all gusts of wind (with an average coherent kinetic energy) would be warmer than still air (with no net kinetic energy) - which is obviously not the case.

2. Regarding degrees of freedom. What do you define as a meaningful temperature? I simply said EVERY particle which has a degree of freedom has a temperature. First you denied this, now you are saying its not meaningfull! And i totally disagree with that statement. Any temperature is meaningfull and you should know that if you understand physics. Do you agree with this?

Temperature (in the statistical sense) can strictly defined as I stated previously; as proportional to the logarithm of the number of microstates corresponding to a given macrostate. This definition provides a consistent bridge between the purely mathematical concept of ``the law of averages'' and the purely physical concept of ``the law of increasing entropy'' (second law of thermodynamics).

However this definition of temperature does not always have a thermodynamic meaning. For example, one can use this definition to define a temperature for the light in a laser, the magnetic moments of a paramagnet, or the result of rolling 2 dice.

The thermodynamic meaning of temperature, which I believe is the meaning you want, is that it is defined as ``the quantity of a substance to transmit heat energy to the surroundings''.

In your mind, does a ``hot'' object next to a ``cold'' object imply that heat energy can be transfered to from the hot object (lowering it's temperature) to the cold object (raising it's temperature)?

(This is the thermodynamic definition of temperature, it is not the only definition of temperature.)

For the example above, a roll of 7 on two six-sided dice has a higher ``temperature'' than a roll of 2, but if you put the 4 dice (after being rolled!) in proximity to one another obviously there will be no transfer of numbers from one to the other.

The thermodynamic definition of temperature is one of the reasons why you need a statistically significant number of particles, and why kinetic energy alone is not a measure of temperature. If two identical objects, one with a temperature of 50 C and the other with a temperature of 20 C are placed side by side, then (assuming no transfer of heat to the environment) I know that eventually they will both end up with the same temperature of 35 C. However, if two identically objects, one with a speed of 50 km/s and another with a speed of 20 km/s collide, I do not know what their speeds will end up being, or the directions they will end up travelling in (without further information, at least).

In your arguments, it seems like you are equating ``kinetic energy'' with ``temperature'' (or at least ``heat energy''). This is not so. They are related - but not equivalent.

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Once we understand the effects of dark energy, humans will be able to measure exactly how fast the universe is expanding. We will be able to measure the increasing speed between galaxies and more accurately calculate the future affect.

I believe dark matter is sub-atomic matter that has a neutral or positive charge that has not achieved the state of an atom. All of the super novae within a galaxy eventually "pushes" this primordial matter outside and circles the galaxy. All normal matter and dark matter will eventually be consumed by its galactic black star.

As far as science is concerned, we have learned to build and keep a fire, but have yet to invent the wheel.

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Again, I disagree. Neither kinetic, rotational, nor vibrational energy implies a temperature. The energy contained in collision-less translational or rotational modes, or coherent vibrational modes does not transfer across boundaries in the same manner as ``heat energy''.

In statistical mechanics temperature is defined as the logarithm of the number of microstates that correspond to the same macrostate, in other words the number of ways a given amount of energy can be arranged in an ensemble of particles. Without a statistically significant number of particles there is no thermodynamic temperature.

Internal degrees of freedom are related to temperature (namely the heat capacity of an ensemble), but the existence of these degrees of freedom does not imply that the ensemble has a meaningful temperature.

For single particles each arrangement of energy corresponds to a different overall behaviour; there is no sensible definition of temperature.

Temperature and heat energy are emergent properties of a large number of particles.

Dark matter is hypothesized to only interact via gravitational force. That is why it is ``dark''. An ensemble of dark matter would have a temperature, but it would be very difficult to transfer any heat energy to or from an ensemble of regular matter since the main thermodynamic and chemical force for regular matter is electromagnetism.

Since dark matter is presumably very sparse it may be difficult to define a meaningful temperature, and it almost certainly would be much lower than the 3 K of space.

from the gist of what you are saying- I get the impression you appear to be contadicting yourself by stating there is no temperature ... then again saying there is no meaningful temp ..

but not being able to measure a temperature , isnt the same as there not being one..

mmm, I doubt if Frank Lambert would agree with you http://entropysite.oxy.edu/

but I could be wrong , I often am.

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From what I've researched, it would seem that Warm and cold Dark Matter both work in simulations. Here is a nifty page explaining such..

Warm dark matter just works better. So if warm dark matter turns out to be the answer to our astronomy conundrums, what does this mean for the physics?

It means that we're not going to find dark matter where we're looking right now. Perhaps it's a sterile neutrino; a fourth family of neutrino that doesn't couple to the other ones the way we're accustomed to? Perhaps it's a new type of particle that we haven't considered before? Or perhaps it is something like an axion, only they aren't born either cold (like standard theory predicts) or hot (like a thermal relic would be), but warm, due to a new type of interaction or coupling?

Whatever the case may be, it's time to reopen the door for warm dark matter, and not to merely dismiss it because there are no satisfying particle candidates. Gravity and structure formation don't lie, so let's listen to what they're telling us!

http://scienceblogs.com/startswithabang/2011/09/and_the_temperature_of_dark_ma.php

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