Beyond Geologic Time
Week 30-Earth Science
How old is it?
Radioactive Decay Reaction Used to Date Rocks1 | ||
Parent | Daughter | Half-Life (billions of years) |
Samarium-147 | Neodymium-143 | 106 |
Rubidium-87 | Strontium-87 | 48.8 |
Thorium-232 | Lead-208 | 14.0 |
Uranium-238 | Lead-206 | 4.47 |
Potassium-40 | Argon-40 | 1.31 |
The Universe’s History | Cosmic Inflation | Big Bang and Nucleosynthesis | Recombination | Dark Ages | First Stars | Reionization |
When? | 13.8 bya | a fraction of a second later… | 380,000 years later | next 200 million years | 200 million years + | 1 by + |
What? | Universe expanded! (>speed of light!) | Energy transfers to matter/light, atomic start to form (H, He, Li, Be), too hot for electrons to bond with nuclei | Electrons bond with the nuclei, light can now travel because electrons are no longer scattering them | Dark b/c new H gas absorbing the light that is being produced. Still mostly H and He | First stars/galaxies (Thanks gravity!) | UV light breaks up the newly formed H gas into protons and elections (ions!) |
The Universe’s History | Cosmic Inflation | Big Bang and Nucleosynthesis | Recombination | Dark Ages | First Stars | Reionization |
When? | 13.8 bya | a fraction of a second later | 380,000 years later | Up to 200 million years later | 200 million years plus | Up to 1 billion years later |
What? | Universe expanded | energy transfers to matter/light, atomic nuclei form but too hot for electrons to attach | electrons combine with atomic nuclei, new nuclei created light (cosmic microwave background radiation) | Newly formed hydrogen gas absorbs all the light… most of the universe is H and He | First stars/galaxies! (Thanks Gravity!) | UV light breaks up the H gas into protons and electrons (ions!) |
The Universe’s History | Cosmic Inflation | Big Bang and Nucleosynthesis | Recombination | Dark Ages | First Stars | Reionization |
When? | 3.8 bya | 3.8 bya | | | | 3.7 bya |
What? | The universe expanded, lots of energy | Energy becomes matter/light, first elements | Cools enough that electrons can stick to atoms, emit first light “cosmic glow” (microwaves) | New hydrogen atoms are absorbing all the light | Cooler denser regions become first stars, clump to form first galaxies (Go Gravity!) | UV radiation breaks up H gas into protons and electrons (so we can now see through things) |
Cosmic History
How Far? How Old?
How Far? How Old?