Time flies like an arrow, fruit flies like a banana

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Shipping containers after an earthquake off the Pacific coast of Tōhoku.
Japan, 2011
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An invisible force at the center of our galaxy
Scientists have theorized that our Milky Way galaxy has a super massive black hole at the center of it, but how did this idea come about?  How do astronomers measure something that has actually never been seen in our telescopes?
Above is an animation of star movements in our galaxy over the past 16 years.  They all orbit around a point that emits no light in our galaxy.  We can measure the mass of these stars and calculate that their orbits require an object with the mass of 4 million Suns.  So far this points to a super massive black hole in our galaxy.
Read more about how galaxies obtain these supermassive objects →

The nothing made of something at the center of everything…
This headline got me thinking… is there a force that is not invisible? I mean we’re all comfortable with the idea that gravity, magnetism, and electrical forces are invisible. We can see their effects, but you can’t point to a force.
Even when it comes to tension, friction, or applied force, we always discuss the effects of the force when we discuss them. The force itself is not a thing that we can point to or see. Even pushing a chair across a room, if we could zoom into the atoms of my hand pressing near the atoms of the chair, we would ultimately see nothing there, just space. The electrons in my hand are in an odd sense “aware” of the electrons in the chair, and they repulse each other, due to electromagnetic force (also invisible) and the exclusion principle.
So really, isn’t all force invisible? Someone call Yoda.
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