Question 1 of 12Correct: 0
Why can't a star get energy by fusing nuclei heavier than iron?
Where did the iron carrying oxygen in your blood come from?
What is the contradiction?
How strong a conclusion can we draw from finding nothing?
Why does life need a liquid?
What's wrong with cold solvents like methane?
What is the Drake equation for?
Which factors remain unknown?
Why do scientists look for water first in the search for life?
What keeps oceans liquid beneath the ice of icy moons?
What is the essence of the paradox?
Which explanation is the most alarming?
Questions from 6 articles
Each one takes 2 minutes to read. Stuck on a question? Peek at the article.
Are You Really Made of Stardust?0/2Why We Still Haven't Found Aliens0/2What Life Without Water Would Be Likein the app0/2How Many Civilizations Could Be in the Galaxyin the app0/2Where to Look for Life in the Solar Systemin the app0/2Where Are the Aliens If There Are Billions of Stars0/2
A quiz after every article
In the app, a quiz like this follows every article, and every read grows your streak and level.
Answers and explanations12 questions
- Why can't a star get energy by fusing nuclei heavier than iron? That fusion takes in energyAt iron, the chain breaks: fusing heavier nuclei no longer releases energy but requires it.From “Are You Really Made of Stardust?”
- Where did the iron carrying oxygen in your blood come from? Stars forged it, including white dwarf explosionsIron did not exist after the Big Bang: stars made it, and white dwarf explosions provide about half of it.From “Are You Really Made of Stardust?”
- What is the contradiction? There are many stars and much time, but no signs of alien lifeA civilization that arose 1 million years before ours would have had time to spread very far.From “Why We Still Haven't Found Aliens”
- How strong a conclusion can we draw from finding nothing? We've listened to a tiny fraction of the sky, so the conclusion is weakIt's like scooping a glass of water from the ocean, finding no fish, and concluding that there are no fish.From “Why We Still Haven't Found Aliens”
- Why does life need a liquid? As a medium where molecules meet and reactThat is why the search focuses on a liquid that exists for a long time, not water as such.From “What Life Without Water Would Be Like”
- What's wrong with cold solvents like methane? Chemistry proceeds extremely slowly at such temperaturesThe age of the universe may not be long enough for anything complex to arise.From “What Life Without Water Would Be Like”
- What is the Drake equation for? Breaking the question into measurable partsIt was designed as a framework for discussion, not as a prediction.From “How Many Civilizations Could Be in the Galaxy”
- Which factors remain unknown? The probability of life, intelligence, and civilization's lifespanWe have just one example, so any result can be obtained.From “How Many Civilizations Could Be in the Galaxy”
- Why do scientists look for water first in the search for life? You can build instruments to detect its signsWe only know life in which water acts as a solvent, so its signs can be detected with instruments.From “Where to Look for Life in the Solar System”
- What keeps oceans liquid beneath the ice of icy moons? Tidal heat from stretching and squeezingA planet's gravity deforms the moon, creating internal friction that releases heat and sustains the ocean.From “Where to Look for Life in the Solar System”
- What is the essence of the paradox? There is enough time and enough stars, but no tracesThe galaxy could have been colonized in millions of years - a tiny span by cosmic standards.From “Where Are the Aliens If There Are Billions of Stars”
- Which explanation is the most alarming? That the barrier is ahead: civilizations die out at a certain stageIn that case, finding simple life would be a bad sign for us.From “Where Are the Aliens If There Are Billions of Stars”