# Gravity and the Vortex Table

When a Line Isn’t a Line or Who’s Line is it Anyway?

What is the shortest path between two points?  I bet most of you said a line, and in a lot of circumstances you would be correct.  The problem is that this is only true if you are using a flat space like a sheet of paper.  When your space begins to curve, you need to become more creative.  Let’s take the cities of New York and Tokyo as an example.  The shortest distance between them would be a straight line going through the Earth, but that’s no help to planes that need to stay above the ground.  So airlines need to figure out a more complex path to make the journey as efficient as possible.  This path is called a great circle! For our New York to Tokyo flight you need to travel north almost past Alaska to travel on the great circle.
Here is a fun site that you can use to map great circles connecting airports around the world: The Great Circle Mapper

Now you might think that outer space would be an escape from these silly curved geometries, but you would be very wrong.  Einstein’s theory of General Relativity showed us that space is very far from flat.  Any object with mass will warp space much like a weight will warp a trampoline.  The heavier the object, the greater the warping.  This is the basic principle of gravity!  One of the interesting effects of this curving of space is that light will behave like our airplane and always follow the shortest path between two points, which often isn’t a line. That is what our vortex table is meant to show.  The marbles are trying to go from one side of the metal ball to the other.  If the ground was flat, they could simply go right next to it, but in our curved fabric space, the shortest path is a nice even circle several inches from the metal ball.

In space, we have even more extreme cases.  For example, the light from a star might be split going around an object like a black hole.  Some of the light goes around to the left, some of the light goes around to the right.  After navigating the black hole, the two beams of light might eventually converge when they get to the Earth.  A telescope detecting these two beams would see two identical stars on either side of the black hole, one on the right one on the left.  In reality, there is only one star behind the black hole, but the telescope doesn’t know any better.  We call this gravitational lensing, just one of the mind-bending things that can happen in space.  Here is a diagram to make things slightly less clear than mud. The gray stars are what you see, the black is what is real.

# What to Freeze Series – Cryogenics

CAUTION: DO NOT TRY THIS AT HOME! LIQUID NITROGEN CAN CAUSE TERRIBLE BURNS! (Death of living tissue caused by the extreme cold.)

Liquid Nitrogen can be scary. We call it a cryogenic fluid because it can rapidly cool substances down to temperatures around -321 degrees Fahrenheit. Unprotected human body parts are not immune to the danger at all. The water in our body will cool down rapidly and cause them to freeze solid, to the point where they could potentially break. That’s where we got the idea to pull this little maneuver, but with a banana in the glove instead of a finger. Just be warned though, we are professionals that know the limits of liquid nitrogen and how far to keep it away from our bodies. Please do not try this at home!!

But in science fiction, cryogenic substance like liquid nitrogen have a long and storied history; mostly being used to put humans into a deep freeze from which they can awaken many years in the future. Cryostasis as it would be called, could be very convenient for a couple of reasons: it could preserve astronauts on interstellar voyages that would normally last longer than a human lifespan, or perhaps preserve a person dying of a terminal illness until the cure is discovered. This type of technology could be very useful if it ever proves feasible. Studies have shown that if the cooling is done slow enough living cells can be preserved using this method. So perhaps we’ll see the first cryogenic human in our lifetime. Sorry to disappoint the conspiracy theorists out there, but Walt Disney is not currently frozen in liquid nitrogen. That’s just a rumor.

In “The What to Freeze Series” we will experiment with freezing different objects. What do you want to freeze next?

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