The Near Side Of A Galaxy Is Tens Of Thousands Of Light-years Closer To Us Than The Far Side; Thus We See The Front As It Was Tens Of Thousands Of Years Before The Back. But Typical Events In Galactic Dynamics Occupy Tens Of Millions Of Years, So The Error In Thinking Of An Image Of A Galaxy As Frozen In One Moment Of Time Is Small.

-Carl Sagan

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The Near Side Of A Galaxy Is

Carl Sagan

The Near Side Of A Galaxy Is Tens Of Thousands Of Light-years Closer To Us Than The Far Side; Thus We See The Front As It Was Tens Of Thousands Of Years Before The Back. But Typical Events In Galactic Dynamics Occupy Tens Of Millions Of Years, So The Error In Thinking Of An Image Of A Galaxy As Frozen In One Moment Of Time Is Small.

Topic

Thinking

Errors

Light

Eratosthenes's Only Tools Were Sticks, Eyes, Feet, And Brains; Plus A Zest For Experiment. With Those Tools He Correctly Deduced The Circumference Of The Earth, To High Precision, With An Error Of Only A Few Percent. That's Pretty Good Figuring For 2200 Years Ago.

Eye

Errors

Zest