A black hole is the most powerful astronomical object, because it can say the n word.
Could We Create A Bottomless Pit On Earth?
“A round-trip journey, from the North Pole to just shy of the South Pole and back to the North Pole again, all through the Earth’s center, should take just a whisker under 90 minutes. Under ideal conditions:
* creating a vacuum,
* straight through the Earth’s rotational axis,
* starting with no tangential velocity,
* devoid of any type of air resistance and subject only to gravitational forces,
you’d wind up right back where you started just 90 minutes later: roughly the same time it takes the international space station to orbit the Earth. So long as you brought an oxygen supply with you, you’d be no worse for the wear.”
From tourist traps to Alice in Wonderland to modern entertainment like Gravity Falls, bottomless pits are tropes that hardly seem physically possible. Sure, you can always envision a thought experiment, but that doesn’t mean you could actually build one. Despite the engineering challenges and the enormous expense that would be associated with such a project, this one turns out to be physically plausible with not-too-distant-future technology. There are a number of obstacles we’d have to overcome, including the Earth’s rotation, drilling a shaft clear through the planet, and stabilizing a passenger against the heat and radioactivity of the natural interior of our world. But if we could do it, and not get stuck at the center, we’d come back to where we started just 90 minutes later.
Here’s the story behind how to create and successfully use a bottomless pit here on Earth!
Ask Ethan: What Happens When A Black Hole’s Singularity Evaporates?
“What happens when a black hole has lost enough energy due to hawking radiation that its energy density no longer supports a singularity with an event horizon? Put another way, what happens when a black hole ceases to be a black hole due to hawking radiation?”
One of the most puzzling things about Black Holes is that if you wait around long enough, they’ll evaporate completely. The curved spacetime outside of the event horizon still undergoes quantum effects, and when you combine General Relativity and quantum field theory in exactly that fashion, you get a blackbody spectrum of thermal radiation out. Given enough time, a black hole will decay away completely. But what will that entail? Will an event horizon cease to exist, exposing a former black hole’s core? Will it persist right until the final moment, indicative of a true singularity? And how hot and energetic will that final evaporative state be?
Incredibly, even without a quantum theory of gravity, we can predict the answers! Find out on this week’s Ask Ethan.