A few days back on Zhihu.com at home, there was an astronomy question that made it onto the “Trending Q&A” list (quite impressive for my homeland), “What is the most frightening celestial object known to science?”

Not surprisingly, in the scientifically literate answers — many of which I might be interested in covering in the near future — there were neutron stars, so dense that a star is compressed is a giant pulsating nucleus capable of destroying your credit card from across the solar system; there was Kepler-1 b, the darkest planet known to modern astronomy, absorbing upwards of 98% of its received radiation; there was Eta Carina et al, gamma ray canons aimed at us that is waiting to burn to a crisp anything crossing their light-cones*; there were also black holes and quasars, of course, I suppose that I follow the keyword “black hole” was why this question made it into my recommendation list.

By the time this is posted here, I have already written an answer, actually.

(CH: https://www.zhihu.com/question/268873123/answer/345000237)

I thought that it was quite ironic that the list did not include the one I always pictured as frightening, one that not everyone recognized as “Celestial object”, even.

— Planet earth.

Just for now, perhaps, picture this, shall we?

The earth is a speck of dust weighing less than 10^-30 of all matter in the observable universe, and occupies a volume lower than 10^-60 of it. Earth weighs a millionth the mass of the sun, who have already consumed many earth masses in its lifetime work of taking advantage of E=mc^2. This mass and scale, we round off in even the most precise computations. On paper, we might mean nothing to this great and empty place.

However, it is from earth that we measured the distance to the fuzziest dot of primordial galaxy; it is on earth that we heard the birthcry of space and time; it is on earth that we weighed stars and clusters; it is on earth that we, with all our history, confusion, suffering and terror, emerged onto a galactic stage, and left acts of greatness behind on the scrolls of time.

It’s fair to say this is rather a slightly non-traditional call to protect the environment ⋯ I love it, and am often frightened by it.

The planet’s sheer mass, resources, their finesse also: climate, tectonics, geomagnetism, ores… At the same time, our insignificance to the planet, and the planet’s obscurity to our cosmos.

It’s dark out there, and no one knows if there’s any audience, but we can bring our own light to the show.

//

Taking GR at Berkeley is really a good choice.

Featured Image: Ringed Earth, Me, 2015