The Friedmann equation includes the Hubble constant to give a much more accurate age of the Universe. In this equation, G is the gravitational constant = 6.67*10-11Nm2/kg2, ρr is the radiation density of the universe, ρm is the matter density of the universe, and ρd is the dark energy density of the universe.
29 June 2023
Dark energy and Dark matter in simple terms:
Dark Energy: Simply put, the anti-gravitational effect observed in galaxies and their drift leads to the concept of a mysterious energy called dark energy. Dark energy is usually described by w ≡ P/ρ, where P and ρ denote its pressure and energy density. Dark Energy is un-massive, roughly 10¯²⁷ kg/m³. Dark energy causes repulsive gravity through negative internal pressure.
10¯²⁷ = 0.000000000000000000000000001
Dark Matter: In the simplest terms, the observed extra-gravitational effects on galaxies and their similar behavior, such as unaccounted rotation, lead to the idea of an invisible mass effect called dark matter.
#darkmatter #darkenergy .
Dark energy and Newtonian gravity:
Dark energy is not very familiar to us.
But we can also observe the effect of dark energy on the Newtonian gravity of galaxies, especially in very large clusters of galaxies like the Coma Cluster.
Dark energy exists at least in intergalactic space and has effective mass <0.
Since dark energy dominates intergalactic space, Newtonian gravity has no effect where dark energy dominates.
Dark energy has no effect within the gravitational effects of galaxies.
The effect of dark energy is stronger than the effect of gravity, so it pushes away gravitationally bound galaxies or their clusters, mega or superclusters.
Dark energy causes antigravity, and engages in a tug-of-war with gravity, with dark energy always winning.
So antigravity due to dark energy pushes galaxies apart, expanding the distance between galaxies.
Affected galaxies have zero-gravity spheres around them, only outside of which dark energy dominates.
About 68% of the universe is believed to be dark energy.
Acknowledgement: The article is written from my memory of a forgotten reaserh work involving scientists of different countries.
#darkenergy #graviyy #newtonian
27 June 2023
Difference between relativistic Doppler shift and shift due to gravitational potential difference:
[Author ORCID: 0000-0003-1871-7803]
When an oscillating body is subjected to either relative velocity or a gravitational potential difference, it can experience a phase shift in its oscillations, which can be associated with an infinitesimal loss of wave energy.
However, the difference between the relative Doppler shift and the phase shift due to the potential difference is the relative energy difference between the propagating wave and the oscillating bodies in relative position, respectively.
Doppler shift considers the frequency change of a wave in propagation but gravitational potential difference considers the frequency change of the oscillating body'. Furthermore, propagating waves even become irrelevant in terms of velocity when the oscillating body itself is in motion.
26 June 2023
What happens when light intersects other light?
In answer I say that light is a bunch of photons and each photon has approximately the same frequency. So when light beams converge to collide with each other, the oscillations of the colliding photons will be immediately amplified but at about the same time the amplified oscillations of the photons will revert back to their previous state.
Photons will move in the direction of their motion with almost no energy expenditure. Almost no energy expenditure is possible because photons have no rest mass and therefore no reverse reaction to their collisions according to Newton's third law.
This explanation applies not only to light but also to any electromagnetic wave.
Note: Photons maintain their energy and momentum during their propagation and interactions. When two light beams converge and their photons collide, the resulting interaction can lead to the phenomena of interference. Interference occurs when the waves align constructively or destructively, resulting in amplification or cancellation of the wave amplitudes, respectively. This behavior is a characteristic of wave phenomena, including light.
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