Astrophysics for People in a Hurry

Points clés

• Les mêmes lois régissent votre cuisine et les galaxies lointaines
• Presque tout l'univers est fait de matière et d'énergie noires encore invisibles
• Les atomes de votre corps sont nés dans des étoiles disparues il y a bien longtemps
• La lumière voyage dans le temps : regarder au loin, c'est regarder le passé
• Vue du cosmos, nos querelles semblent dérisoires et notre curiosité, précieuse

À l'intérieur de ce bit

1. The cosmos in coffee breaks

   You are waiting for a delayed train, phone in hand, with 10 spare minutes. Neil deGrasse Tyson wrote this book for exactly that moment: short, self-contained chapters that give a busy person a working sense of how the universe operates.

2. One set of laws everywhere

   The most powerful idea in astronomy is that physics is universal. Gravity that drops a mango from a tree in Ratnagiri is the same gravity that keeps the Moon in orbit and the Milky Way spinning.

3. Most of the universe is dark

   Here is an uncomfortable fact: everything you can see, every star, planet, and person, makes up only around 5 percent of what is out there. Galaxies spin so fast that they should fly apart, yet they hold together, which means something unseen is providing extra gravity.

4. You are made of stardust

   Where did the calcium in your bones and the iron in your blood come from? Not from Earth originally.

5. Light is a time machine

   Light is fast but not infinitely fast, and that single fact turns telescopes into time machines. Sunlight takes about 8 minutes to reach you, so you always see the Sun as it was 8 minutes ago.

6. Passez à l'action

   This week, download a free sky app and identify one planet and one constellation from your balcony or terrace, even through city lights. When you next see the Sun rise, remind yourself that you are watching light that is 8 minutes old.