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jimjohnson
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The cosmological constant (Ʌ ) is equated to dark energy and has units of energy/volume. Why have I read that Ʌ equals the Hubble constant squared (H2) which has units of 1/sec2? There must be an obvious explanation.
jimjohnson said:...Why have I read that Ʌ equals the Hubble constant squared (H2) which has units of 1/sec2? ...
jimjohnson said:Marcus, thanks for the explanation relating a curvature constant to energy density.
A number I have referenced for the value of dark energy is 5.81 x 10-30 gm/cm3 (assuming it exists) which is very close to what you quoted (5.2 joule/km3 to your .54 joule/km3).
Is there an online reference that shows the Friedmann and Einstein equations with units (setting c = 1 is always confuseing)?
Is the calculator you referenced the Ned Wright calculator?
Oh no! You sound discouraged. I've failed to understand what you were curious about, and proceeded in the wrong way.jimjohnson said:Thus, my question on scale is beyond my math ability.
marcus said:I've failed to understand what you were curious about, and proceeded in the wrong way.
No, you answered my conern on the units which I needed. I am researching dimensionless constants. Thanks
marcus said:As far as we know "dark energy" is fictional--an artificial convention. I think it became a fashionable idea after 1998 when it was found that instead of being zero (as most people had assumed) the Ʌ constant in GR equation was a small positive curvature.
The cosmological constant is a term in Einstein's theory of general relativity that represents the energy density of empty space. It was originally proposed by Einstein as a way to balance the force of gravity in the universe and maintain a static universe. However, it is now considered to be a measure of the expansion rate of the universe and is closely related to dark energy.
The cosmological constant is thought to be the physical manifestation of dark energy, which is a mysterious force that is causing the expansion of the universe to accelerate. It is still not fully understood, but many scientists believe that the cosmological constant is the most likely candidate for explaining dark energy.
The units of the cosmological constant are typically given in units of energy per unit volume, such as Joules per cubic meter or ergs per cubic centimeter. In some cases, it may also be given in units of pressure, such as Pascals or atmospheres.
The value of the cosmological constant is determined through observations and calculations using data from various cosmological surveys and experiments. It is a fundamental constant of nature, and its value is currently estimated to be extremely small, but not zero.
The value of the cosmological constant has a significant impact on the future of the universe. If the value is positive, it will continue to accelerate the expansion of the universe and eventually lead to a "big rip," where everything in the universe is torn apart. If the value is negative, it could potentially lead to a "big crunch," where the universe collapses back in on itself. However, if the value is close to zero, it could result in a stable, eternal universe.