Tea with Science

Imagine yourself a space tourist, standing on the moon and looking back at those fluff-white clouds gliding across the Earth. You can gaze on that view as long as you like, but you’ll never see Earthrise nor Earthset from the surface of the moon. The Earth will stay in one place and instead of watching it travel across the sky, you'll get to watch it spin. Our 1st glimpse of the far side, 1959/ Luna 3 , by  OKB-1 You would see the Earth spin from the moon because the moon takes the same time to make one full rotation as it takes to orbit the Earth, a little over 27 days. As a result, the moon always shows us the same face. It’s a leisurely rotating pace compared to the Earth’s whirling, 365 times for each single orbit around the Sun. Long ago, when the moon was young, it span a lot faster. As it did so, the Earth’s gravity was felt more strongly on whichever part of the moon was facing the Earth, just as the moon’s gravity tugs at the Earth’s oceans to produce tides. Th...

It’s not the prettiest of telescope images. It doesn’t have the majesty of spiral galaxies, nor the sharp chic of Saturn’s rings. The color scheme is not exactly appealing, and there’s nowhere obvious to focus. Yet it's one of my favorites, a snapshot of the universe as it was in its infancy. Planck CMB / Image: ESA and the Planck Collaboration Some 13.7 billion years ago, a mere 380,000 years after the Big Bang, photons of electromagnetic radiation were set loose to journey across the universe. Up until that time, photons couldn’t travel far without being scattered by free electrons, in the same way that photons of light on Earth get scattered by fog. As a result, the universe itself was opaque, one giant fog. That changed when the universe cooled enough that electrons could no longer roam free, but were bound to protons as hydrogen atoms. With the electrons tied up, the photons were on their way. Those photons are travelling still, some of them are passing us now, but the ...