Someone asked if I liked to watch horror/scifi movies. It depends...
A few years ago I was trapped on a cross country flight and saw The Black Hole - one of those scripts that is so bad it is almost, but not quite, worth watching. Check out the trailer...
Most special effects and animated movies take liberties with physics. Starting with Disney many of the classic animation films created increasingly more interesting variations on physics to improve the storytelling physical worlds. There were any number of tricks to trick the viewer to better immerse them in the story.1
Special effects tend to suffer. I'm able to enjoy films like Guardians of the Galaxy, but poor scripts and acting break the story telling and I find myself spending most of my time thinking about the physics.
With that a mini-analysis of The Black Hole - (no plot is spoiled as I didn't notice one)
Somehow an there is an accident in a secret physics lab a hundred feet below St Louis. Physicists have managed to create a tiny black hole that escapes and trolls around under the city coming up for buildings like the great white shark in Jaws. At this point I'm completely out of story space and am thinking about small black holes.
Hmmm... about 30 meters underground and buildings on the surface are collapsing. I'll make the assumption it is a miniature classical black hole, more on that later, and suggest that the gravitational force from it at the surface is about ten times Earth's gravity - that should be enough to flatten a building. I could have picked other numbers, but we're just doing a little thought experiment and don't need to accurately understand how strong buildings are. With this you can work out its mass - roughly about twenty trillionths the mass of the Earth - a bit over 100 trillion kilograms. Now we're getting into interesting territory..
The event horizon of a black hole that mass is roughly a tenth of a trillionth of a meter - about ten thousand times smaller than a hydrogen atom.2 Put it on the ground and it won't feel any resistance to any material on or in the Earth. As soon as its created it will fall toward the center of the Earth picking up speed as it goes. It whizzes through the center at about eight kilometers a second and starts slowing down as it heads towards a point, judging from my globe, on the surface of the Indian Ocean well off the Australian coast. Maybe it dines on a fish before reversing direction and heading back about 42 minutes later.3 Back and forth, back and forth - we have an odd sort of clock.
Games like this turn out to be a central part of play in physics. You make a non-physical assumption - assume a miniature black hole is created just under St Louis - and follow what happens using established physics. In the process you can quickly deal with many questions and decide on those that are the best candidates for serious study. Now that we have our black hole tic-tocking between St Louis and the Indian Ocean, let's look at smaller black holes.
I mentioned this was a classical black hole. In 1974 Stephen Hawking proposed black holes can evaporate. The time required for one formed from a collapsed star is extremely long - it would take about 1067 years for one with our Sun's mass ... approximately forever when you consider the age of the universe is 13.8 billion years. But the rate of evaporation has a strong dependence on the black hole's mass and lighter black holes evaporate faster. The little St Louis black hole would last about a hundred times longer than the current age of the Universe.
Smaller black holes can have lifetimes small even on time scales we're used to. One with the same mass as a small car - about 1,000 kg - would evaporate in a billionth of a second and would be about 200 times as bright as the Sun. These super tiny black holes would make a very powerful and completely impractical doomsday devices - even more impractical than antimatter. In other words the perfect plot device for a movie.
I'll end with a problem for those who like to work things out. Send mail if you'd like hints.
The Master from Dr Who or a slightly annoyed Vogon captain approaches the Earth with a super slicer beam that instantly makes a cut through the Earth. What happens if the cut is through the equator and is one centimeter wide? What happens with a one meter cut? How about ten meters? Now work the problem with the same three cuts, but this time slicing from pole to pole. How does humanity make out in each scenario?
1 If you have the slightest interest in animation The Illusion of Life: Disney Animation by Olie Johnson and Frank Thomas is just wonderful. Go for the hard cover and treasure it. Disney did amazing groundbreaking work, and other expanded wrote new rules. Chuck Jones created an animation for roadrunners and coyotes that is an art form. Even today the tricksters are still at it.
2 the Schwarzschild radius is proportional to mass rs = 2GM/c2. The point is it only goes linearly with mass while the mass of a star goes as the cube of the radius - the event horizon get small very quickly as mass drops. The Sun has an event horizon of about 3 kilometers ... far too small to contain it. rs for the Earth is 0.9 centimeters.
3 42 minutes through a frictionless tunnel is the result everyone calculates in physics 101, but that assumes the Earth's interior has a uniform density. Recent work giving a better understanding of the Earth's density distribution cuts a few minutes off the transit time.
I grilled some asparagus and used a homemade olive based dressing. Ideally the trick would be to layer pieces of tomato on a bed of the grilled asparagus before adding the dressing, but it isn't good tomato season (yet). Here's the dressing...
° 3 tbl finely chopped kalamata olives
° 3 tbl extra virgin olive oil - a good one pays off
° 3 tbl red wine vinegar
° 3 tbl crumbled feta (leave off if you want it to be vegan)
° 2 tbl finely chopped red onion
° 1 clove garlic - very finely chopped or grated
° 1 tbl honey
° 1 tbl dijon mustard
° 1 tsp oregano
° salt and pepper to taste
° mix the ingredients