Tired light

High school (ages 12+)
Space & Astronomy

Name:

Date:

Step 1 · Read the article

Open the article and read it at the level above. Then answer the questions below in your own words.

https://smallwhale.org/articles/tired-light

Write what each word means, using the article.

Do not copy the article. Write two things you learned, the way you would explain them to a friend.

Answers below are taken from the article’s stored facts, so they match what the student read.

1. What is the hypothesis proponent?Fritz Zwicky
2. What is the year of introduction?1929
3. Why did scientists test tired light?They wanted to see if the red color of far stars could be explained by light getting tired, not by the universe stretching.
4. How did observations show tired light is wrong?Distant galaxies look sharp and not blurry, and their brightness and supernova light curves match expansion, not tired light.

Photon: The quantum of the electromagnetic field, a fundamental particle of light.
Redshift: The increase in the wavelength of electromagnetic radiation, typically due to the Doppler effect or cosmological expansion.
Cosmological Redshift: The redshift of light from distant galaxies caused by the expansion of the universe stretching spacetime.
Surface Brightness Relation: The relationship between the apparent brightness of an object and its distance, which is affected by cosmic expansion.