“Even today, more than eighty years after Oort's bold guess, we still don't have a clue what this dark matter is made of. We know it exists. We know where it is. We have maps of its presence within and around galaxies throughout the universe. We even have stringent constraints on what it is not, but we have no clue what it is. And yes, its presence is overwhelming: for every one kilogram of ordinary matter made out of neutrons and protons and electrons, there are five kilograms of dark matter, made out of who-knows-what.” MatterUniverseMapsOverwhelmingClueGalaxyPresenceKnowConstraintsWhatElectronsExistDark MatterGalaxiesMapWhereNeutronsGuessExistsProtonsOort Book:The Universe in Your Hand: A Journey Through Space, Time, and Beyond Source: The Universe in Your Hand: A Journey Through Space, Time, and Beyond
“Waking up in the same place in which you dozed off has never happened either to you or to anyone else. Ever. Earth does not stop moving when you sleep. Every hour that passes, Earth travels a little more than 800,000 kilometres around the centre of our galaxy. And so do you. That's the equivalent of about twenty trips around the planet. Every hour. No one minds, though, as long as their bed stays still beneath their body.” BodyEarthSleepMovementBedCentreGalaxyNeverMoveWaking UpTripHourTripsKilometresDoze Off Book:The Universe in Your Hand: A Journey Through Space, Time, and Beyond Source: The Universe in Your Hand: A Journey Through Space, Time, and Beyond