What if Ganymede was the Earth’s second moon?

Jupiter’s moon Ganymede is the largest and most massive of the Solar System’s moons. It has a mean radius of 2634.1±0.3 km (about 1636 miles, 0.413 Earths). For comparison, our Moon’s radius is 1,737.1 km (1079 mi). What if Ganymede was the Earth’s second moon? How would it look in the sky, if it was […]

How many great minds does it take to invent a telescope?

On 11 January 1672, the Fellows of the British Royal Society were treated to a demonstration of Isaac Newton’s reflecting telescope, which formed images with mirrors rather than with the lenses that had been used since the time of Galileo. Afterward, the fellows hailed Newton as the inventor of this marvelous new instrument, an attribution […]

Earth can be a model for detecting vegetation on exoplanets

Back in December 1990, during its flyby of Earth, NASA’s Galileo spacecraft, which studied the planet Jupiter and its moons, as well as several other Solar System bodies, pointed its instruments towards Earth, at the urging of Carl Sagan. And, it has found evidence of life on our planet. This can be a key to detect […]

A bowling ball and feather falling in a vacuum – do they fall at the exact same speed?

A beautiful video published by BBC: the English physicist Brian Cox tests how a heavy object (a bowling ball) and a lightweight object (feather) falling in a vacuum – if they fall at the exact same speed or not.