<p>The <a href="https://en.wikipedia.org/wiki/Sunyaev%E2%80%93Zeldovich_effect" rel="nofollow noreferrer">Sunyaev–Zeldovich effect</a> (SZ effect) is useful in determining the Hubble constant because it is independent of the cosmic distance ladder. This effect occurs when CMB (cosmic microwave background) photons scatter off of plasma in the intracluster medium.</p>
<p>I am lost as to how this effect is used to determine Hubble's constant. Can someone explain it <em>like I'm five?</em> I'm assuming the SZ effect produces a distance which is then combined with the redshift to determine <span class="math-container">$H_0$</span>. I would like help understanding how a distance is determined from this effect.</p>

CC BY-SA 4.0
2021-06-22T02:46:58.890Z
I've made some small edits to your question, please feel free to edit further. Potentially related: answers to [Is the universe macroscopically transparent to CMB? Is the fraction intercepted by stars and dust so tiny that it doesn't have a correction factor?](https://astronomy.stackexchange.com/q/43458/7982) and [Conventional matter to dark matter ratio, outside of galaxies](https://astronomy.stackexchange.com/q/16201/7982)
uhoh
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2022-02-01T11:12:48.783Z
No, I can't explain it to a 5-year old and I doubt anyone else can.
ProfRob
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2022-02-01T15:35:58.853Z
*Can someone explain it like I'm five?... I would like help understanding how a distance is determined from this effect.* So you want to understand it like a 5 year old would?
Daddy Kropotkin
<observational-astronomy><cosmology><hubble-constant><cosmic-microwave-background><sunyaev-zeldovich-effect>
Explain as simply as possible how the Sunyaev-Zeldovich (SZ) effect is used to estimate the Hubble constant
Astroturf
# Explain as simply as possible how the Sunyaev-Zeldovich (SZ) effect is used to estimate the Hubble constant

(Asked by: username_0 on 2021-06-22)

The [Sunyaev–Zeldovich effect](https://en.wikipedia.org/wiki/Sunyaev%E2%80%93Zeldovich_effect) (SZ effect) is useful in determining the Hubble constant because it is independent of the cosmic distance ladder. This effect occurs when CMB (cosmic microwave background) photons scatter off of plasma in the intracluster medium.

I am lost as to how this effect is used to determine Hubble's constant. Can someone explain it *like I'm five?* I'm assuming the SZ effect produces a distance which is then combined with the redshift to determine $H\_0$. I would like help understanding how a distance is determined from this effect.

**Tags:** observational-astronomy, cosmology, hubble-constant, cosmic-microwave-background, sunyaev-zeldovich-effect

> **Comments:**
> **username_1**: I've made some small edits to your question, please feel free to edit further. Potentially related: answers to [Is the universe macroscopically transparent to CMB? Is the fraction intercepted by stars and dust so tiny that it doesn't have a correction factor?](https://astronomy.stackexchange.com/q/43458/7982) and [Conventional matter to dark matter ratio, outside of galaxies](https://astronomy.stackexchange.com/q/16201/7982)  
> **username_2**: No, I can't explain it to a 5-year old and I doubt anyone else can.  
> **username_3**: *Can someone explain it like I'm five?... I would like help understanding how a distance is determined from this effect.* So you want to understand it like a 5 year old would?  

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## 0 answers

