Is the universe infinite
Chapter 1
The cosmic horizon of our sight
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Chapter 2
The shape and geometry of space
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Chapter 3
Is there an edge to everything
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Chapter 4
The expanding cosmos and cosmic speed limits
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Chapter 5
Three ultimate fates of the universe
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YOUR GOAL
Master of Is the universe infinite
Ch 3 · Is there an edge to everything
teacher There's no boundary wall and no center in sight, We are just in a bubble of far-travelled light.
Fun Fact
Archytas's spear: Archytas of Tarentum used a simple thought experiment with a spear in 400 BCE to argue that space must go on forever.
Glossary
observable universe (noun)
The portion of the cosmos that can be seen or detected from Earth. In 2013, the Planck satellite refined this visible boundary to approximately forty-six billion light-years.
The portion of the cosmos that can be seen or detected from Earth. In 2013, the Planck satellite refined this visible boundary to approximately forty-six billion light-years.
Quiz
Which of the following would be required for a universe to have a literal physical wall?
Quiz
What is likely true about the region of space just outside our observable horizon?
Quiz
What do scientists call the hypothetical collection of multiple co-existing universes?
Quiz
Which concept describes a space that has a limited volume but no physical boundary or wall?