Hello backers! We’re back from China on Tuesday, and we’re getting closer to finalizing our terms with the factory. Here are my answers to the great physics questions you asked me. Thanks for your support!
Ranjit: I’d love a concise explanation of why the twin who takes the high speed round trip on a rocket ends up younger than the twin who stayed on earth- if motion is relative, how do we distinguish between the twin who moved real fast and the twin who didn’t?
In general relativity, we all travel through “space-time” at the same rate. Therefore, something moving near the speed of light through space does not experience time passing by as quickly as something at rest.
It is important to note that in this case, the two twins can distinguish themselves from each other. While motion is relative (there is no correct “rest” frame), it is possible to measure acceleration. Both the twin on the rocket and the twin on earth agree on which of them accelerated and therefore would have aged less (assuming they have an understanding of special relativity).
Bryan: What is the opposite of a sandwich, physics-wise?
To me, a sandwich is a convenient way to deliver messy food to my mouth using bread and my hands. It would be very inconvenient if my attempt to push a sandwich into my mouth instead pushed the food away from me.
However, this is just the behavior of matter with negative mass. Any force acting on such an object causes acceleration in the direction opposite to which the force is applied. If you push a negative-mass sandwich to the left, it will move to the right. If you squeeze it together, it will fall apart.
I think this would be incredibly frustrating and would cause me to give up eating. Therefore, I think the opposite of a sandwich is a negative-mass sandwich.
Patrick: Could you explain to me how Shadowcat from X-men’s power works?
Shadowcat is able to walk through walls and pass through other objects and people. This is possible with quantum tunneling. In quantum tunneling, a particle (like Shadowcat) can pass through a barrier (like a wall) despite not being energetic enough (or far enough off the ground) to pass through classically. Because there is no known way to manipulate quantum tunneling on the scale Shadowcat exhibits, I can only conclude that she is very, very lucky.
William L: I’ve heard that the majority of our mass is made of up of the kinetic energy derived from gluons (source: http://www.youtube.com/watch?v=TbtjLVRVy7Q&feature=plcp ). How did this kinetic energy come into being, and how does it interact with a proposed Higgs Boson?
First off, this is not my field, so I’m happy to yield to someone more knowledgeable.
It is true that most of our mass is made up of gluon kinetic energy, but this is more accurately described as Quantum Chromodynamics Binding Energy (QCBE). This energy comes about from the interactions of quarks within the proton or neutron. When the quarks are close together, there are many possible interactions, which take the form of high energy real and virtual gluons. This is what binds quarks together into individual protons and neutrons.
Gluons, however, have no rest mass and do not interact with the Higgs Boson. The Higgs mechanism only gives mass to massive particles (quarks, leptons, and bosons).
Elleinad Niksab: Can ‘mental states’ exist outside the brain?
I think this is more of a philosophical question. Since the entire state of our body (position and velocity of every atom) could possibly be encoded outside the body, I’m going to go with ‘yes.’ Although the encoding of this state might not be comprehensible to anyone, it could in theory be recreated at any time.
J. Cortés Mayor: What are potential uses for plasma, anything we shall see in the next few years, and how well are its properties known?
Plasma is ubiquitous in our lives: fluorescent bulbs, fire, lightning, and the sun are all examples of plasmas. Plasmas can be used for anything from semiconductor fabrication to curing athlete’s foot to nuclear waste separation. Most research in the field is focused on fusion energy, but this is still several decades from being commercialized.
The properties of plasmas are fairly well understood, at least on a short scale. However, we can still be surprised by large-scale behaviors because simulating all of the interactions among many particles quickly becomes intractable. This is what makes plasma science so exciting!
Jason L: I want a Theory of Everything or point me to that moon where we’ll find those Engineers. Thanks!
Here is my never-before-published theory of everything, known as Gnome Theory. Everything we see and measure is caused by the behavior of tiny, undetectable gnomes. The gnomes follow the instructions of the Gnome King, who is detectable but lives at the center of the earth (or universe, some scientists argue). The instructions of the Gnome King should be chosen such that they are consistent with all past experiments.
Thomas Symborski: Assuming you had 3 spheres of mass at random locations within a cube of space. They are all uniform and homogenous. Assume one of them has an atmosphere. Now imagine a new small solid sphere moving through the randomly-heated turbulent liquid atmosphere. What is a closed form solution for its trajectory taking into account the gravitational pull of the three spheres.
Since I am given control over the initial three spheres, I will throw them all out of the problem. The solution is then, for a sphere travelling through empty space:
x(t) = x_0 + v_0 t,
where x_0 is the position at time t=0 and v_0 is the velocity at t=0.
Xande Macedo: How does sous vide really work?
“Sous vide” works by cooking food at a low temperatures. This allows the heat transferred to the food to be precisely controlled, allowing only the desired chemical reactions to take place.
Kurt: From a biochemical perspective, why does cooking food at a temperature below boiling result in more tender, more flavorful food?
Focusing on meat, traditional cooking leads to overcooked regions of muscle fibers. The myosin filaments around the fibers contract and squeezes out the juices. Within the cells, the proteins coagulate and form solid cores surrounded by liquids. These liquids are easily lost on a grill or in a pan, leading to chewy, dried-out meat. There is usually not enough time for the collagen in the cells, which contributes to toughness, to turn into a tender gelatin.
With low temperature cooking, the myosin fibers are contracted enough to give the steak some texture. However, because there isn’t a high temperature source boiling away the liquids, the steak remains juicy. In addition, a long time in the water bath allows the collagen to dissolve into gelatin, making even a tough steak tender without losing the juiciness.
In terms of flavor, cooking at low temperatures allows more flavor molecules to remain intact in the meat, instead of being denatured or boiled off.
Food and Wine Maven: What are the physics behind your favorite food tip? Perhaps letting meat rest after cooking or the salad spinner…
Obviously, my favorite tip is to cook at low temperatures in a plastic bag :) See above for the physics!