## Real world attempt to reach the Earth’s core (OK, really just the mantle)

After watching “The Core,” I couldn’t help but share this article about a proposed real-world attempt to drill into the Earth’s mantle (not the core, but the mantle, but, hey, we haven’t even done that before). Enjoy!

http://www.nature.com/news/quest-to-drill-into-earth-s-mantle-restarts-1.18921

## The Core

This movie gets my vote for the worst movie physics of any of our feature films this semester; it even got ISMP’s vote as the #1 worst physics movie they’ve ever reviewed. To me, the bad physics is made even worse by the fact the movie takes itself way too seriously; there is very little humor; and I just don’t find myself connecting emotionally with any of the characters. So, how bad is it?  Here’s my list:

1. The wavelength (and speed) of sound changes when it passes from one medium to another, but not the frequency.
2. Birds don’t have enough mass or fly fast enough to have the momentum required to break through a piece of glass.
3. The shuttle does not spin around nearly as quickly as portrayed. The amount of angular momentum involved would require a huge (and perfectly timed) thruster burn. The real thing would be done much more gradually. You’ve watched NASA television, right?
4. The Earth does not have an electric field, only a magnetic one.
5. THE BIG ONE: Angular momentum conservation requires that if the Earth’s core stop spinning, something else must take up the angular momentum lost by the core. In the movie angular momentum apparently can just disappear. The movie claims that there are “a trillion tons of hot metal moving at 1000’s of miles per hour”. That’s a lot of momentum. Of course, that’s Hollywood, and nobody apparently bothered to calculate what the real values are. The Earth’s outer core has an estimated mass of roughly 2×10^{24} kg, which is 2×10^{21} metric tons, or 2 billion trillion metric tons. On the flip-side, Hollywood overestimated the speed, which is more like 200 m/s or 450 mph.
6. OK, another big one: conservation of mass. What happens to all the matter that makes up the rock that the laser obliterates. Even if the laser completely vaporizes the rock, that vapor has to go somewhere. And at the tremendous pressures inside the Earth, it would likely resolidify very quickly.
7. An explosive charge inside the Earth would not restart its rotation. Again, conservation of angular momentum must apply and angular momentum can only change whenever a torque is applied. An explosion inside Earth would not create a torque.
8. When they break through the “geode” the terranauts would be in freefall. They would “float” like astronauts, not dangle in their seatbelts.
9. Not quite sure how walking from compartment to compartment works with the whole gimbal system… Seems like the terranauts would need to climb ladders or something to get from compartment to compartment.
10. Microwaves don’t fry the planet, though they are pretty useful for making a quick bag of popcorn. Also, your cell phones work in the microwave band. They are not particularly harmful and certainly the intensity of microwaves from the Sun is not enough to do any damage (microwaves make it right through the Earth’s magnetic field, anyway, and a lot of them make it through the atmosphere, too).
11. Just having some extra plutonium around is not going to make a nuclear bomb stronger; it just makes it “dirtier.”

If you’re thinking that I let a few other bad physics examples pass, you’re probably right. I tried to just concentrate on some of the really big ones.

Good physics:
1. An electromagnetic (EM) pulse could disrupt all electronics within some specified radius. However, the only weapon that is known to create an EM pulse this large is a nuclear bomb, which creates many things other than just an EM pulse. [FYI, a supposed prototype EM pulse weapon was used by Ocean’s gang in the movie “Ocean’s 11″ to knock out the electricity in Las Vegas.]
2. Earth’s auroras are the result of the interaction between the solar wind, the Earth’s magnetic field, and the Earth’s atmosphere. Changes in our magnetic field would affect the auroras over time.
3. The Earth does have a crust, a mantle, and a core made of two components: a solid inner core and a molten outer core.
4. The deepest humans have ever penetrated inside the Earth’s surface is indeed 7 miles as claimed in the movie. However, that is still not deep enough to even penetrate the crust. After that the mantle goes down to a depth of 1800 miles or so, hundreds of times deeper than we’ve ever gone.

1. Some birds do navigate using the Earth’s magnetic field. However, this is for long-distance navigation, not to fly around in a public square. I doubt birds would suddenly start flying into objects even if the Earth’s magnetic field suddenly changed (birds can see after all).
2. The solar wind is not “radioactive particles and microwaves”. It’s made of ions, protons, and electrons. But the Earth’s magnetic field does deflect the solar wind away from the Earth.

## Interstellar

I still have mixed feelings about this movie.  It has some great physics in it, things no film has tried to portray this accurately before.  But it also has some far-fetched aspects and Hollywood touches that detract from the overall experience for me.  Maybe I’ll have more to say after I watch it again tonight.

Assignment: This week I want you to pick a physics topic from the movie to analyze.  There are plenty of things to choose from, including space travel, black holes, wormholes, higher dimensions, extreme time dilation, and many others.  To help you in this task, you are required to choose a topic that has a corresponding chapter in the book, “The Science of Interstellar.”  You can then use that chapter as a guide to help, but NOT limit, you in writing your blog.

Please post on your blog by Sunday, 22 Nov.

At least one chapter from “The Science of Interstellar”

pp. 208-225 – Don’t Try this at Home

## Star Trek

I love this movie. It’s still one of my favorites. I’ve already watched it a number of times, and I’m happy we’ll be watching it again tonight. First off, I grew up a Trek fan. Not an over-the-top, wear a Federation uniform and speak in Klingon, kind of a fan, but a science geek who certainly appreciated some of the very fine ideas Star Trek brought to us. And from a Physics in Film perspective, this movie has some good moments, like the absence of sound in space when the ship’s hull is breached and a crewman is pulled out into space. The “red matter” and time travel are complete fiction, but they make for an exciting plot, and I guess I’m willing to let it go because of how cool it is to see the Star Trek brand reinvigorated like this. (BTW, ISMP has a very lengthy preview and review of this movie.)

As with all great science fiction, Star Trek has always done its best to weave great science and great fiction into a very imaginitive tapestry. Many of the technologies introduced in Star Trek were predictive of technologies we have today – the communicator devices in the original Star Trek series are eerily similar to the push-to-talk cell phones that are commonly used by businesses today. Other technologies in the series are likely many centuries away or even impossible. But even here, the Star Trek series tried whenever possible to stay within the realm of things that were at least physically plausible based on our current understanding of science. Only a few of the technologies are the stuff of pure fiction.

Assignment: Most of the technologies introduced in the Star Trek series were necessary to fulfill one plot requirement or another. There were very few gratuitous technologies, which is consistent with how new technologies are really developed. Necessity is the mother of invention, after all. So what I want you to do for your assignment this week is to explain the plot need behind two of the technologies in the Star Trek series. For your first technology, I want you to consider the “warp drives” on the USS Enterprise. Why was the warp drive a necessary plot device in Star Trek? Remember, this is a physics question. So discuss what some of the physical limitations were, and why it was necessary to go beyond current technology. The choice for the second technology is yours, but I’d like for you to talk about why the technology was necessary for the plot and what the feasibility of the technology is in the real world.

Please post your blog by Sunday, 15 Nov.

Ch. 24 – Bad Astronomy; Ch. 2 & 4 – Physics of Star Trek

Ch. 4 – ISMP

## “Fat Man and Little Boy” and “Gojira”

Thematically, this week’s double feature deals with the morality of having scientists design and build weapons of mass destruction. Many scientists who do this hide behind one of the moral shields presented in “Fat Man and Little Boy”: the scientists are only responsible for developing the weapons, not using them. Other scientists openly embrace their role. Edward Teller was one prominent Manhattan Project scientist who felt that the only way to keep the world safe was for the United States to have weapons of such terror that no other nation would dare step too far out of line. Even after WWII ended, Teller advocated further development of atomic and then nuclear weapons. In a very real sense, he was the architect of America’s modern nuclear arsenal. Still other scientists have felt that there is no way to divorce the results of such weapons’ use from their development, and therefore have refused to work on weapons-related research. (Sadly, that right to refuse to work on weapons research is not afforded to scientists of all countries.)  Clearly, “Gojira” takes the position that the scientists of the Manhattan Project are just as morally culpable for the bombing of Japan as the politicians and military generals who conceived of and planned the actual bombing.  This is probably why this version of “Godzilla” was not played in the U.S. until 2004, 50 years after its original release in Japan!

Assignment: You have a choice of what to discuss in your blog this week: Option 1) Compare and contrast the moral positions of the scientists in “Fat Man and Little Boy” and “Gojira.” If you were going to be a scientist, what would your position be on doing research that had weapons applications?  Would you be OK with it?  Would you embrace it?  Would you avoid it?  What if it were the only career option open to you in science?  Option 2) Discuss the science of the Godzilla monster.  You can incorporate other movie monsters if you like, but I am very specifically interested in monsters that are abnormally large or abnormally small.  There are some very basic principles of physiology that make it practically impossible to supersize or supershrink any given creature.  If you need some help getting started on this topic, have a look at Ch. 4 of “Insultingly Stupid Movie Physics.”  You can also discuss genetic mutations if that is up your alley.

Please post your blog by Sunday, 8 Nov.