Mars Retrograde 2018

It has begun. Mars is making the turn from its usual eastward progress across the sky. It will appear to move westward for the next two months. At the end of August it will slowly turn and head eastward again. Why? How can that be?

Mars in retrograde 2018 | Click to embiggen

The answer is simple. Earth orbits closer to the Sun than Mars. We move faster than Mars. We are passing Mars at this time. It is the same perspective as when passing another car. The passed car appears to move backward relative to your faster car.

In addition, Mars grows in size when viewed through telescopes until the end of July. After that, it will decrease in size. If you have access to a telescope, look for Mars in the east after sunset. You’ll need a high power to see any detail. Let’s hope the dust storm settles to reveal those details.

The graphic below from BinTel illustrates the apparent change in diameter given in arc-seconds (“). At the end of July, the Moon will appear about 24″ wide. For reference, the angular diameter of the Sun, or a full moon, is about 1800”, half a degree. That is the width of your little fingernail seen at arm’s length.

BinTel | Andy Casely

5 thoughts on “Mars Retrograde 2018

  1. My astrologically inclined friends often talk about the havoc raised when Mercury goes retrograde, but I’ve never heard about any effects — positive or negative — from Mars going retrograde. I’ll have to inquire and find out if there’s any cosmic chaos awaiting us. (I suspect not.)

  2. Very fine post Jim. Do you ever wonder if you could figure out the moon and planets if not for all the science that came before? Imagine being an ancient person without telescopes or running plumbing 🙂 watching the bright planets move contrary, or not in time, to the star filled sky. It must have been something to witness.

    • It would certainly take a lot of long-term observing to witness some of those long patterns. It’s good the ancients paid attention and made notes and constructed stuff to mark the solstices and equinoxes. People have always been pretty smart. Not everyone is able to show it. If you knew when an eclipse would occur, you were powerful.

    • Maybe we should have a world-wide holiday each year to express our gratitude for the discoveries and inventions that have gradually made the world more comprehensible and human existence much better for so many people.

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