Science Photo Library/Alamy
Will there ever be a time when all the planets of our solar system line up in a row, one behind the other, as seen from Earth? (continued)
Richard Swifte
Darmstadt, Germany
An exact line-up would mean that each of our seven neighbouring planets eclipses those behind it, which, given their small angular sizes as seen from Earth, is incredibly unlikely.
Realistically, you should allow a lining-up to within at least a few degrees.
As an example, just considering longitude, Mercury (nearest the sun) laps Venus every 0.396 years. Allowing 1.8 degrees of separation gives an arc of 3.6 degrees,…
