The universe is made of the stuff on the periodic table
The core idea stands, but key numbers or details have changed.
TaughtEverything in the universe is made of atoms: the elements in the periodic table, arranged into stars, planets, and people.
NowOrdinary atomic matter is about 5% of the universe's energy content. Roughly 27% is dark matter and 68% is dark energy, and we do not know what either is.
What actually happened
Evidence for dark matter goes back to Fritz Zwicky in the 1930s and Vera Rubin's galaxy rotation curves in the 1970s: galaxies spin too fast for the visible matter to hold them together. That was known when many people reading this were in school, but it was often a footnote, framed as an anomaly rather than as most of reality.
The precise budget came from mapping the cosmic microwave background. WMAP in 2003 and Planck in 2013 measured the faint temperature ripples in the afterglow of the Big Bang finely enough to weigh the universe's ingredients. The answer: everything you have ever seen, touched, or measured chemically is a 5% rounding error.
Be careful with the word "disproved" here. Nothing about atoms turned out to be wrong. What changed is the scope of the claim. Chemistry describes a small and unrepresentative fraction of the universe, and the majority is made of something we have never identified in a laboratory.
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Sources
- NASA: Dark matter and dark energyscience.nasa.gov
- ESA: Planck cosmic recipeesa.int
Who was taught this
Still standard through 2003, so anyone who finished school between 1950 and 2003 learned the earlier version.