Comparing Types Of Time Travel In Fiction

MinutePhysics (which, if haven’t checked out already would be worth spending a little of your time on) and a fun whiteboard explainer on the different types of time-travel in various films and books. Specifically, the video synopses how time travel causally affects the perspective of characters’ timelines (Who has free will? Can you change things by going back to the past?).

I appreciate time travel stories that have a nice logic to them. I have to agree with Henry Reich when he says that, “Logical consistency is a thing that you may have noticed I think lays the foundation for good time travel stories.” Which explains why I didn’t like Star Trek: First Contact or the Original Superman.

Mapping Earth’s Gravitational Pull

The data from the GOCE satellite reveals a potato-shaped earth defined by varying gravity. The globe seen below is a highly exaggerated rendering that neatly illustrates how the tug we feel from the mass of rock under our feet is not the same in every location. In fact, it varies widely. In this model gravity is strongest in yellow areas; it is weakest in blue ones.

The BBC says,

Technically speaking, the model is what researchers refer to as a geoid. It is not the easiest of concepts to grasp, but essentially it describes the “level” surface on an idealised world.

It is the shape the oceans would adopt if there were no winds, no currents and no tides. The differences have been magnified nearly 10,000 times to show up as they do in the new model.

Even so, a boat off the coast of Europe (bright yellow) can sit 180m “higher” than a boat in the middle of the Indian Ocean (deep blue) and still be on the same level plane. This is the trick gravity plays on Earth because the space rock on which we live is not a perfect sphere and its interior mass is not evenly distributed.

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1.21 Gigawatts!

Less than two seconds in real-time, this video of a lightning strike in Rapid City, South Dakota is spectacular. The video is slowed down to 9,000 frames per second. ZT Research describes the video as a preceding downward positive ground flash that triggers upward leaders from seven towers, three of which are visible in the video. I love how hundreds of “mini strikes” flicker around the central strikes. ZT Research has more cool lightning strike videos on their site.