Sciencespeaking topic
Everything in the universe is moving away from everything else, but the galaxies aren't moving through space; space itself is expanding. Can we drift apart from each other without going anywhere?
— expansion of the universe / metric expansion
practice with this topic
Set the timer (5-30 min), take 20 seconds of prep if you like, start talking. Jot your thoughts onto the sticky-note board.
similar topics
- There's a physically blind spot in your eye at every moment; where the optic nerve exits, there are no light-sensing cells. But you never notice it, because the brain 'makes up' that gap by looking around it. Of the world you think you see, how much is real and how much is the brain filling in?
- Your body sweats to cool down when it's hot, but you also sweat when you're excited or afraid; the sweat on your palms runs on a separate system driven by emotion, not heat. For our ancestors, 'stress sweat' may have made gripping or fleeing easier. What danger are your sweaty palms before an exam preparing for?
- Ask hundreds of people one by one to guess the weight of an ox and average their guesses, and the result is often more accurate than the expert butcher's. How can a crowd know so precisely when none of them alone does, and when does this flip into mob madness?
- A rising fever isn't a malfunction, often it's a strategy: the body deliberately raises itself to a temperature that disturbs microbes. So most of what makes you feel sick isn't the illness but the body's defense. Is feeling terrible sometimes the very act of healing?
- The tragedy of the commons: why does everyone taking a little too much from a shared resource eventually destroy all of it? Why does individual reason clash with the common good?