- 3252 - UNIVERSE - how much does it weigh? By combining measurements using different techniques, astronomers were able to determine a best combined value, concluding that matter makes up 31.5±1.3% of the total amount of matter / energy in the universe. Only 5% is “Normal Matter”. You , me, and everything we see.
------------------ 3252 - UNIVERSE - how much does it weigh?
- How can we possible precisely measure the total amount of matter in the universe? A daunting exercise.
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- Astronomers determined that matter makes up 31% of the total amount of matter and energy in the universe, with the remainder, 69%, consisting of “dark energy“.
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- If all the matter in the universe were spread out evenly across space, it would correspond to an average mass density equal to only about six hydrogen atoms per cubic meter.
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- However, since we know 80% of matter is actually “dark matter“, in reality, most of this matter consists not of hydrogen atoms but rather of a type of matter which cosmologists don't yet understand. You kids are going to have to figure this out for yourselves. We don’t get it?
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- The technique for determining the total amount of matter in the universe is to compare the observed number and mass of galaxy clusters per unit volume with these predictions from simulations.
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- Because present-day galaxy clusters have formed from matter that has collapsed over billions of years under its own gravity, the number of clusters observed at the present time is very sensitive to the total amount of matter that exists.
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- A higher percentage of matter would result in more galaxy clusters. "The 'Goldilocks'“ challenge for our team was to measure the number of clusters and then determine which answer was 'just right.' But it is difficult to measure the mass of any galaxy cluster accurately because most of the matter is “dark” so we can't see it with telescopes.
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- To overcome this difficulty, astronomers developed "GalWeight," a cosmological tool to measure the mass of a galaxy cluster using the orbits of its member galaxies. The Sloan Digital Sky Survey (SDSS) was used to create "GalWCat19," a publicly available catalog of galaxy clusters.
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- Then they compared the number of clusters in their new catalog with simulations to determine the total amount of matter in the universe.
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- This is the first use of the galaxy orbit technique which has obtained a value in agreement with those obtained by teams who used noncluster techniques such as “cosmic microwave background anisotropies“, “baryon acoustic oscillations“, “Type 1a supernovae“, and “gravitational lensing."
- Using the GalWeight galaxy orbit technique astronomers were able to determine a mass for each cluster individually rather than rely on more indirect, statistical methods.
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- By combining these measurements with those from the other teams that used different techniques, they were able to determine a best combined value, concluding that:
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---------------------------- Matter makes up 31.5±1.3% of the total amount of matter / energy in the universe.
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- I thought you needed to know that. Only 5% is “normal matter“. I left the rest for you to figure out. You can convert these percentages to pounds or kilograms if you like.
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- August 18, 2021 UNIVERSE - how much does it weigh? 3252
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--------------------- --- Thursday, August 19, 2021 ---------------------------
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