What is the speed of dark
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Understanding the Concept of the Speed of Dark
Theoretical Background: Speed of Light and Dark Energy
The concept of the "speed of dark" is often discussed in the context of dark energy and dark matter, which are fundamental components of the universe. Dark energy, which is responsible for the accelerated expansion of the universe, can be characterized by its equation of state and the sound speed of its perturbations. Studies have shown that as the sound speed of dark energy drops below the speed of light, inhomogeneities in dark energy increase, affecting cosmic microwave background and matter power spectra2 5. However, current observational data do not significantly constrain the sound speed of dark energy, although future data may provide more insights2 5.
Observational Constraints on the Speed of Light
The varying speed of light (VSL) theory suggests that the speed of light may not be constant over time. This theory has been tested using observational data from type Ia supernovae, baryon acoustic oscillations, and the cosmic microwave background. The results indicate that the speed of light has remained almost constant for redshifts less than 0.1, with only minor variations at higher redshifts1. This supports the notion that the speed of light is a constant with high significance, making it difficult to differentiate between the VSL dark energy model and the standard ΛCDM model1.
Dark Matter and High-Speed Particles
Dark matter, another critical component of the universe, also has implications for the concept of speed. The highest-speed local dark matter particles, originating from the Large Magellanic Cloud, can reach speeds of 700-900 km/s relative to Earth. These high-speed particles can significantly impact direct-detection experiments for dark matter, extending the reach of these experiments to lower mass and elastic scattering cross sections6.
Speed in Darkness: Human Perception and Movement
In a more literal sense, the speed of dark can also refer to human movement in dark environments. Experiments conducted in completely darkened tunnels have shown that walking speeds are significantly reduced in the absence of light. Participants' walking speeds were found to be approximately lognormally distributed, with a mean value of 0.49 m/s, highlighting the challenges of movement in dark conditions7.
Conclusion
The concept of the speed of dark encompasses various interpretations, from the theoretical implications of dark energy and dark matter to the practical challenges of human movement in darkness. While the speed of light remains a constant in the universe, the behavior of dark energy and dark matter continues to be a subject of intense study, with future observations expected to shed more light on these mysterious components.
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Most relevant research papers on this topic
Observational constraint on the varying speed of light theory
The speed of light appears to be constant with high significance, as observed by the type Ia supernova, Baryon Acoustic Oscillation, Observational $H(z)$ data, and Cosmic Microwave Background.
Measuring the Speed of Dark: Detecting Dark Energy Perturbations
Current data can't constrain dark energy's sound speed when it's a recent phenomenon, but may reveal interesting results for early models.
Highly CitedTachyons, tactility, drawing and withdrawing: cinema at the speed of darkness
Contemporary mainstream cinema's increased darkness may relate to the interconnected, ultra-rapid nature of the digital world, expressing uncertainty and disorientation.
Constraints on the dark matter sound speed from galactic scales: The cases of the modified and extended Chaplygin gas
The observed rotation curves of spiral galaxies constrain the sound speed of dark matter to be $c_s 10-4 c$, providing the most stringent constraint on the constant contribution to the equation of state parameter in unified dark energy models.
Constraints on the sound speed of dark energy
Current observations have no significant sensitivity to the sound speed of dark energy, but models with and without dark energy perturbations provide roughly equal good fits to observations, potentially impacting future parameter estimations.
Highly CitedThe highest-speed local dark matter particles come from the Large Magellanic Cloud
The highest-speed local dark matter particles come from the Large Magellanic Cloud, with two populations contributing at high speeds: bound particles and accelerated halo particles.
Walking speed in completely darkened full-scale tunnel experiments
The mean walking speed in a dark tunnel is 0.49 m/s, with age and gender having a small influence, and the study found that walking speed in a dark tunnel is approximately lognormally distributed within a 95% interval, crucial for assessing tunnel fire safety.
Non-RCTDark Energy after GW170817 and GRB170817A.
Gravitational waves travel at the speed of light, simplifying dark energy models and allowing for stable solutions under quantum corrections.
Highly CitedVariable sound speed in interacting dark energy models
Interacting dark energy models can produce a variable dark energy sound speed, leading to a deviation from unity and potentially impacting cosmic microwave background and linear matter power spectrum.
CONSTRAINTS ON THE SOUND SPEED OF DYNAMICAL DARK ENERGY
The sound speed of dynamical dark energy is weakly constrained by current observations, requiring future precision measurements of the cosmic microwave background on a large angular scale.
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