- #1
Planck energy density is a max, is there a minimum too?
Intuition, though sometimes helpful, does not always lead to a good scientific answer.
We now know that where classic theory meets QM we find a maximum for obtainable mass density (Planck density) thus energy density.
Space as we now know can expand (Hubble expansion) at the cost of energy density.
By intuition I have a feeling that it might be a good question to ask whether it is possible to dilute energy density almost to zero. Is it possible from theory (e.g. QT) to expect that there must be an end to such a dilution? IMO it can’t be so that there are voids with absolutely nothing in the space filled with energy. So if energy density, (has a minimum), can not be diluted to whatever low level and if voids, with really nothing, don’t exist then as a consequence expansion of space must come to a halt too?
Do you think my intuition is wrong in this case?
marcus said:Hurk, Wallace is right.
In the standard cosmology picture there is the dark energy, to account for accelerated expansion, and it is usually assumed to be constant throughout space and time.
marcus said:it may be a little confusing the way I and several other people use the word 'standard' in two contexts
there is the socalled standard model of particle physics (which does not have any explanation for dark energy 73 percent, and only some shaky speculations about dark matter IIRC)
there is also the standard cosmology model, LCDM. It is the one nearly everybody seems to use most of the time, so it is natural to call it standard too
this model has a dark energy with constant energy density (corresponding to Lambda) and a constant ratio of pressure to density, namely w = -1, but it does not say what this should be in terms of laboratory particle physics.
I hope it will continue to be all right with everybody for us to refer to both these two models as standard----one is the prevailing model in cosmology and the other in particle physics.
Please correct 0.73J/km to 0.6J/cubic-km.hurk4 said:Hi Marcus,
Here is my attached file
hurk4 said:Hi Marcus,
But I hope I can learn something.
I think I still have further questions or remarks.
marcus said:Hurk4, I just now saw your posts, which have questions to me. I'm sorry to say that I am not prepared to respond! Dark energy is a complete mystery to me. I think you have the accepted estimate for it's density----about 0.6 joules per cubic kilometer. ==========================
Ah hah! I got the doc file to open.
Characteristics of spaces.
Hubble space (HS) and dark-energy space (DES) compared.
1) If space is inversely related to its energy density then Hubble space expands when its energy density content only relates to non dark energy. Dark energy related space does not expand because of its constant energy density (roughly 6E-10Jm^3)?
2) DES seems to be of different nature (QM nature?) compared to HS (Classic nature?)?.
3) Locality seems to play its role in HS where non locality might play its role in DES (Quantum nature?)?
4) HS is contained in DES?
5) In HS, DES related energy density increases from roughly zero % at Planck time to about 73% now to maybe 100% where as NDE related density dilutes from about 100% to roughly 0%?
6) In how far as is suggested by 1) to 5) is non dark energy (NDE) related to dark energy (DE)?
7) Is the Casimir effect a manifestation of a relation between CE and NDE?
8) In HS there is no action at distance maybe there is in DES?
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I got the other file to open too!
I can see you are calculating how it will be (assuming DE is constant as in the LCDM model) when space expands a lot more so that matter density instead of being 27 percent will be more like zero percent.
Then the total density will be just about 0.6 joules per cubic km.
this will mean that the Hubble paramter goes down from around 71 (what it is now) to around 60.
Have to go. Will try to respond more tomorrow
Amp1 said:So Wallace is saying that energy (that we readily observe) and darkenergy are not quite the same thing and although energy can approach zero, dark energy doesn't? I'm wondering what are the two together?
The Planck energy refers to the maximum amount of energy that can exist in a given space and time. It is named after German physicist Max Planck who first proposed the concept in 1900.
Yes, there is also a minimum energy known as the Planck energy scale. This is the smallest possible unit of energy that can exist in the universe and is approximately 10^19 GeV (gigaelectronvolts).
According to quantum mechanics, energy can only exist in discrete units rather than continuously. The Planck energy serves as the upper limit because at this scale, the laws of physics as we know them break down. The minimum energy, on the other hand, is a fundamental limit that is a result of the uncertainty principle.
The Planck energy is much larger than any other unit of energy commonly used in physics. For comparison, the energy released in a nuclear explosion is about 10^10 GeV, while the energy of visible light is around 1 eV (electronvolt). The Planck energy is also equivalent to about 10^32 Kelvin.
No, the Planck energy is far beyond the capabilities of current technology and is unlikely to ever be observed or measured directly. However, scientists can study its effects through theoretical models and experiments at smaller energy scales.