Evidence of Expansion: Redshifting of EM Radiation

In summary, there is plenty of evidence for the expansion of the universe other than the redshifting of EM radiation. The existence of the Cosmic Microwave Background (CMB) and the interpretation of galaxies moving away from each other as a result of this expansion are two key pieces of evidence. However, there are also alternative interpretations, such as successive shrinkage of space-time, that have been proposed but are not as widely accepted due to non-scientific reasons. It is important to note that the redshift cannot be solely attributed to the expansion of space as it would also result in a blueshift, indicating that there may be other factors at play.
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Calimero
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Are there any evidence that universe is expanding other then redshifting of EM radiation?
 
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The existence of the CMB shows that the universe was once a lot hotter and denser, which is the conclusion you reach if the universe is expanding.
 
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The redshift in the EM radiation from galaxies increases in proportion to their distance from us.

If interpreted as a Doppler shift, galaxies are rushing away from each other, matter inside galaxies remaining largely unaffected. This interpretation has lead to the Big Bang model, which has been so eagerly defended against evidence by postulating inflation, dark matter and dark energy.

It can also be interpreted as a successive shrinkage of space-time, if it is assumed that light is not shrunken. This leads to various models of the Universe that are dispreferred, mainly for non-scientific reasons.

Although some text-books say so, the redshift cannot be interpreted as due to an expansion of space as such. Such an expansion could not be observed, unless the light was not expanded on its way. But in this case, we would see a blueshift.
 

Related to Evidence of Expansion: Redshifting of EM Radiation

1. What is redshifting and how does it provide evidence of expansion?

Redshifting is a phenomenon observed in the electromagnetic (EM) radiation emitted by distant galaxies. It refers to the stretching of the wavelength of the radiation as it travels through expanding space. This provides evidence of expansion because the greater the distance between the observer and the source of the radiation, the more redshifted the radiation appears. This is consistent with the idea that the universe is expanding, as more distant objects would have had more time to travel through expanding space.

2. What types of EM radiation exhibit redshifting?

All types of EM radiation, including visible light, radio waves, and X-rays, can exhibit redshifting. This is because all of these forms of radiation are made up of waves, and the stretching of the wavelength is what causes the redshift.

3. How does the amount of redshifting relate to the distance of the source?

The amount of redshifting is directly proportional to the distance of the source. This means that the farther away the source is, the more redshifted the EM radiation will appear. This is a key piece of evidence for the expansion of the universe, as it supports the idea that more distant objects are moving away from us at a faster rate due to the expansion of space.

4. Can redshifting be used to measure the expansion rate of the universe?

Yes, redshifting can be used to measure the expansion rate of the universe. By analyzing the amount of redshift in the EM radiation emitted by different objects at various distances, scientists can calculate the rate at which the universe is expanding. This is known as the Hubble constant, named after the astronomer Edwin Hubble who first discovered the relationship between redshifting and distance.

5. Are there any other explanations for redshifting besides expansion?

While redshifting is primarily seen as evidence for the expansion of the universe, there are other possible explanations. For example, the Doppler effect can also cause the wavelength of EM radiation to appear stretched as a result of the relative motion between the source and the observer. However, this explanation is not as consistent with the observed redshifts seen in distant galaxies, which is why the expansion of the universe is currently the most widely accepted explanation for redshifting.

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