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Yes, Virginia, Black Holes Exist! (A synopsis) [Starts With A Bang]
Do black holes exist? The world’s most famous scientist vs. the actual science.
“My goal is simple. It is a complete understanding of the Universe, why it is as it is and why it exists at all.” -Stephen Hawking
Here in our little corner of the Universe, the Earth is a pretty intense source of gravity for us. If we want to escape its gravitational pull, we’d need to accelerate ourselves up past the escape velocity, or the speed necessary to climb out of the gravitational potential well that Earth’s mass creates. We can (and have) accomplished this, in fact, but it would take a speed of around 11.2 km/s (or 0.004% the speed of light) to make it so.
Image credit: NASA / Apollo 17; modifications by Wikimedia Commons user Ultimate Roadgeek.
But that’s not so fast, after all, not compared to a great many things in this Universe. The reason that we don’t need higher speeds to escape from our planet is that despite having a decent amount of mass — some 6 × 10^24 kg, or some 10^49 heavy atoms — our Earth is spread out over a relatively large volume of space.
But if the laws of physics were somewhat different, we might be able to compress the mass of our Earth down into a much smaller region of space. And if we could, it would take greater and greater speeds to escape from it. At some point, when all the mass of the Earth was compressed into a sphere a little smaller than a centimeter in radius, you’d suddenly discover that nothing in this Universe — not even light — could escape from it.
You’d have turned the Earth into a black hole.
[Go read the whole thing -- in which the firewall paradox is resolved -- at Starts With A Bang on Medium. Yes, I brought it up as a possibility yesterday; let's try it and see if you respond!]
Source: http://scienceblogs.com/startswithabang/2014/02/01/yes-virginia-black-holes-exist-a-synopsis/
