The Universe is expanding. This cartoon on redshift explains how we know.

What is redshift and how does it prove the expansion of the Universe?

NGSS Standards

HS-ESS1-2. Construct an explanation of the Big Bang theory based on astronomical evidence of light spectra, motion of distant galaxies, and composition of matter in the universe.

Activity_Modeling the Big Bang

Ever since the Big Bang around 13 billion years ago, our Universe has been expanding. While the rate of expansion has been hotly debated within the astrophysics community, the space in between galaxies is growing. But how do scientists know the Universe is getting bigger? It’s due to a phenomenon known as the Doppler Effect in which the frequency of a wave changes based on how an object is moving.

In 1929, astronomer Edwin Hubble, from whom the famed Hubble Space Telescope is named after, observed that light from distant galaxies was appeared redder than would normally be expected. Hubble concluded the wavelengths of light being emitted were being stretched as space in between galaxies increased. Called redshift, it was one of the first pieces of evidence for the Big Bang Theory – ever since all matter and space exploded into creation from an infinitely small point in space, the Universe has been expanding like a balloon being inflated.

The cartoon from Wandering.Planet below explains how the Doppler Effect works and how light waves are either stretched or compressed depending on how the object that is emitting the light is moving compared to you, the observer. The cartoon also explains how gravity can change the path and behavior of light as it travels through space.


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After my last post about using the Doppler Effect to find planets someone asked me if it is the same as the term redshift, a word we astronomers use a lot Then I thought "I could use the same illustrations to explain that" So I have arranged these illustrations in a couple of minutes to explain the difference between the Doppler effect and redshift. I would love to get opinions from you. If it is not clear I can do it again and do it better! Also if you think that a particular page has too much information or doesn't look right (aesthetics) please tell me, that helps a lot! . . . #astronomy #redshift #illustrator #illustration #infographic #gravity #astrophysics #physics #science #art #space #universe #expansion #colors #cosmos

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