Dark Matter

[MikeAL]

23 minutes ago, Strange said:

Again, that doesn't say anything about the mass or gravity of a cold, dark rock decreasing with time. 

It was you that brought up the cold dark rock in outer space, not me. I have directed you to ideas on how entropy may affect it, but you don't want to listen to them or to the ideas laid out in the Heat Death of the universe, so I'm not sure how I can help you further with this idea.

My idea is about gravity alone being the force of Dark Matter, not the mechanism by which cold dark rocks in outerspace lose heat energy to the universe.

29 minutes ago, Strange said:

For example, in the case of a candle, the wax will be converted to (mainly) carbon dioxide and water, and small amount of the mass will be converted to light (the total mass of the CO2 and H2O will be less than the mass of the wax and oxygen used to burn it). In the case of an electron and positron, the two particles will disappear completely and the energy will be given to a pair of photons.

I think you forgot about heat. If you are determined to play games with me then let me ask you another question. What is the mass of a photon?

[Strange]

13 minutes ago, MikeAL said:

It was you that brought up the cold dark rock in outer space, not me.

As an example of why your claim was wrong.

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I have directed you to ideas on how entropy may affect it, but you don't want to listen to them or to the ideas laid out in the Heat Death of the universe, so I'm not sure how I can help you further with this idea.

It is not that I don't want to listen to them; I know they are irrelevant. You would know this too if you understood anything about thermodynamics or gravity.

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My idea is about gravity alone being the force of Dark Matter, not the mechanism by which cold dark rocks in outerspace lose heat energy to the universe.

They obviously lose heat energy (until they are at the same temperature as space). That isn't what you claimed. You said they would "lose gravity".

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I think you forgot about heat.

Yes, very good. Some of the energy will go into the kinetic energy (heat) of the reaction products and surroundings.

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If you are determined to play games with me then let me ask you another question. What is the mass of a photon?

What makes you think I am playing games?

Photons are, as any fool know, massless.

[MikeAL]

3 minutes ago, Strange said:

They obviously lose heat energy (until they are at the same temperature as space). That isn't what you claimed. You said they would "lose gravity".

 

4 minutes ago, Strange said:

You would know this too if you understood anything about thermodynamics or gravity.

3 minutes ago, Strange said:

Photons are, as any fool know, massless.

How much gravity does a massless object have? Do I really need to walk you through this step by step?

[Strange]

Just now, MikeAL said:

How much gravity does a massless object have? Do I really need to walk you through this step by step?

As you are being so cryptic, I don't know what you are talking about. Are you trying to get to the point that light / photons can create a gravitational effect? Or what?

It is, of course, impossible to answer the question ("How much gravity does a massless object have?") because you haven't provided any information about this "object". I don't even know what sort of object could be massless. But presumably you have a different concept of "object" than I do (which would be, roughly, something made of matter that therefore has mass and takes up space).

If you are asking about the gravity of a photon or its mass-equivalence, then the answer is obvious (and I'm sure it has already been mentioned in this thread).

[MikeAL]

1 hour ago, Strange said:

As you are being so cryptic, I don't know what you are talking about. Are you trying to get to the point that light / photons can create a gravitational effect? Or what?

Oh my goodness.

E = mc2

Mass can be converted to energy. If mass is converted to energy it is no longer mass. Mass is described by its effect on gravity. Less mass means less gravity.

As the universe expands it continues to cool. As the temperature drops thermal radiation is lost from your rock. Thermal radiation is a type of energy. The loss of thermal energy from matter therefore reduces mass. This leads to a reduction in gravity.

Hawking Radiation suggests that even black holes will evaporate as they lose energy in the form of radiation. An evaporated black hole has less gravity than one that is not evaporated. If it can happen to a black hole, I guess it can happen to your rock too.

Can we move on now?

[Strange]

8 minutes ago, MikeAL said:

As the universe expands it continues to cool. As the temperature drops thermal radiation is lost from your rock. Thermal radiation is a type of energy. The loss of thermal energy from matter therefore reduces mass. This leads to a reduction in gravity.

Of course. Although you might want to work out how large an effect this is. (Hint: it is immeasurably small).

Also, if you understood the stuff about entropy that you keep copying and pasting, you would realise that this process will stop when the rock reaches equilibrium. At that point there will be no more radiation and no more loss of mass.

[Strange]

Another good article on what colliding galaxy clusters tell us about dark matter and modified gravity theories: https://medium.com/starts-with-a-bang/the-bullet-cluster-proves-dark-matter-exists-but-not-for-the-reason-most-physicists-think-b6bc1320a21b

[interested]

Just in case no one else spotted this bit of news, Dark matter might not exist after all https://arxiv.org/pdf/1710.11425.pdf