Tuesday, February 16, 2016

PBS Digital Studios produces its "Space Time" channel on YouTube, great little short films about cosmology

PBS Digital Studios offers a large collection of videos called “PBS Space Time”, narrated mostly by two British physics professors, each thirty-somethings, in casual dress.  They range in length from 8 to 15 minutes each, and end with a quiz question, and a review of last week’s take-home physics test.

Let’s look at three of them for now.

The Real Meaning of E=mC-Squared” (link) looks at the idea that the mass of an object is not exactly just the sum of the masses of component parts.  It also includes energy of the component pieces.  The mass of a chess clock that is running (like in a five minute game) is greater than the mass of one that is turned off, because of the kinetic and heat energy of component pieces. However, there is such an idea as negative energy.  The mass of an atom is less than the sum of the masses of the individual protons, electrons and neutrons, for most elements of the Periodic Table.

I can remember in physics class in eleventh grade high school (in 1960), being taught that the neutrino has no rest mass.  But “rest mass” is now an antiquated, pleonastic term.

He says that “mass is a property”, the way Microsoft uses the term. (In OOP, objects in a class share properties.)

There is a certain film (Drama blog, Nov.4, 2012) when a teen picks up several children off the ground at a single moment.  The physics question is, does the mass of the Earth increase because the potential energy of the smaller kids increases?  I think the answer is no, because energy has already been expended to hold them securely.  But it’s a tricky physics question with possibly a subtle moral point about engagement.

The next two films deal with traveling to other solar systems, even the nearest one, a triple-star, the Centauri system, about 4.5 light years away.  They are not thought to have as good a chance of habitable planets as some stars hosting the Gliese systems about 20 light years away.

5 Real Possibilities for Interstellar Travel” (link) asks, what if, to survive, we have to send a cohort of survivors away to another system, say because of an approaching black hole.  That sounds like the “Evacuate Earth” NatGeo movie scenario (Aug. 30, 2013, “CF” blog).  We’d have to worry about family values and fertility and baby viability in space.  (Artificial gravity isn’t quite as good as the real thing.) The “quick and dirty” if we have to act quickly is rockets from nuclear weapons.  Much cleaner might be fusion reactors (and Taylor Wilson already built one – a mini star --  in his family garage in Reno, NV at age 14 and is now proposing radical changes to the power industry – Wilson, now 21, could very well host some episodes of this series if PBS wanted him to).  Then there is the sapphire pion light sail idea.  There is also the idea of building a small black hole from lasers to provide the thrust.  It might be possible for robots to build such a machine on the Moon, away from people.

 Another film would be “Is the Albucierre Warp Drive Possible?” Wikipedia explains the drive here. The idea is that, while the speed of light is absolute for matter and energy (and maybe information), space-time itself can change in unlimited ways.  The warp drive eats space, like a pac-man.  This gets into metric tensors and negative energy.  It also considers ball lightning, maybe Kugelblitz, Rydberg Matter, maybe the stuff of Brown Mountain lights after all.

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