All Questions
Tagged with cosmology experimental-physics
63
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Absolutism of speed [closed]
If we know that any photon emission travels with light of speed in vacuum, what theoretically stops us to create big enough detecting machine, where photons (lasers probably) are emitted in different ...
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1
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137
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Which evidences do we have that general relativity works at large scales?
Recently I've been reading Pedro Ferreira's SciComm book The Perfect Theory: A Century of Geniuses and the Battle over General Relativity. At one of the last chapters, which discusses modified ...
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Tests for general relativity
As a theorist, I’d guess that in Newtonian gravity we can check for proportionality to mass, and inverse square proportionality to distance, by measuring the ratios of gravitational forces.
Is there ...
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How would red (frequency) shift work for sound waves on the surface of a balloon?
Imagine an expanding balloon with a source of vibrations, in the fabric of the balloon, on one side (pole), and a microphone on the other side (pole). We would expect the sound to be 'red shifted' ...
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What do WMAP CMB Temperature map values represent exactly?
I understand that Cosmic Microwave Background Radiation Map provided by WMAP survey in HEALPix pixelization format is nothing but an array of temperatures associated with the cmb radiation coming from ...
2
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Problem with the Fisher information matrix in case of $N$ measurements of two observables
Let consider two observables, $x$ and $y$. Suppose that $y$ depends on the independent variable $x$ through the model $m(x; \boldsymbol{\theta})$, where $\boldsymbol{\theta}$ is a vector of model ...
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By what experiment is the vacuum energy density actually measured?
I have heard that the actual vacuum energy density which is up to 120 orders smaller than the predicted QED value can be measured in experiments or cosmological observations?
What are these ...
- 4,170
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How to rule out that the speed of light was different in the past?
The constancy of the speed of light is a fundamental principle in modern physics, and it is supported by a wide range of current experimental evidence.
There is no evidence to suggest that the speed ...
- 487
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*Observational* Consequences of Energy Nonconservation in GR
What are the experimental or rather observable consequences of the non-conservation (or conservation) of energy in GR? Imagine our instruments were $10^3$ or even $10^6$ more sensitive, better ...
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Spacetime of a quantum measurement
In a classical(or wave) picture, when we measure a doppler effect from a receding galaxy, we are working on two wave crests essentially. Therefore, there are two events in spacetime for such detection....
- 2,794
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Experimental Test for the cyclic $G_{earth}$ prediction of a Cosmological Model
Can anyone suggest a way to measure or rule out a tiny cyclic variation in the earth’s gravitational constant $G_{earth}$, predicted by an alternative cosmological model? It’s an annual cyclic ...
- 13.7k
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Frequency sensitivity of gravitational wave interferometer with its armlength and with mass of the mergers
To the best of my knowledge, LIGO is capable of observing gravitational waves (GW) from stellar mass black hole (BH) mergers but not mergers of supermassive black holes. In order to detect the latter ...
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How do we obtain matter-lambda curve?
I have 400 supernovas type Ia's distance modulus and its error and redshift.
how can I obtain an elliptic curve like the one in image for my datas?
where did that elliptic came from?
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Research in next decade on dark matter: sky surveys vs particle detectors
The next decade is very promising for cosmology as new surveys such as SPHEREx, Roman, Euclid, DESI which will shed light on inflation, dark matter/energy and more. At the same time there are particle ...
- 4,576
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What difference does the wavelength and/or frequency of a gravitational wave make? On the detector, for instance?
When they talk about the arms of LIGO or Virgo stretching by a thousandth of the width of a proton, they always emphasize that this is the wave's amplitude, not wavelength...
The wavelengths are ...
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