THE LOW FULL MOON…
Tuesday, 3 July, is a full moon, the night of the Thunder or Hay moon. This year’s Thunder moon will also be the “lowest” moon in the sky. What do I mean by “low” moon?
Head outside around 10 to 11 pm or later and note how low the Moon is off the southern horizon. The full moon nearest summer solstice is the “lowest” moon of the year in the northern hemisphere. The opposite is true for those south of the equator.
Why is this so? Let’s get some terms straight. The ECLIPTIC is the Sun’s apparent path across the sky. Professor James Kaler at the University of Illinois offers an excellent explanation here. The ecliptic can also be thought of as the “plane” of the solar system. The planets of our solar system and the Moon appear within a few degrees of the ecliptic in our sky. Think of the ecliptic as a great looping see-saw in the sky.
Earth’s axis is tilted 23.4 degrees to the plane of our orbit. As we circle the Sun we tilt toward (summer) or away (winter) from the Sun. This tilt also determines how the ecliptic cuts across the sky as viewed here on Earth. In the northern hemisphere summers the Sun tracks high across the sky.
Look at the point on the chart labeled “summer solstice”. That is right about where the Sun is these days….but it’s already “heading south for the winter.” When the Moon is “full” it is opposite the Sun in our view and on the lower side of the “see saw”at the spot marked “winter solstice”. In northern summers while the Sun is arcing high across the sky, at full phase the Moon is on the low side. If you happen to be in the southern hemisphere the opposite is true. The full Moon of July will appear high in your sky while the Sun rides low not far above your horizon. Check it out for me and let me know what you see!
Check this for yourself by going outdoors around mid-day and noting the position of the Sun off the southern horizon. NEVER LOOK DIRECTLY AT THE SUN! Do the same thing late in the evening with the Moon.
These early summer evenings are also a good time to check out the Moon illusion
WE’RE FURTHEST FROM THE SUN! WHY IS IT SO HOT?!!!
Thursday, 5 July at about 03 hours Universal time ( 11 pm EDT 4 July) planet Earth will be a aphelion, furthest from the Sun. We’ll be about 1.017 astronomical units from old Sol, roughly 152 million kilometers from our star or about 3.4% further away than at perihelion which happens on 3 January. Here in the midwest we have been suffering through nearly a week of high temperatures above 100 F so my saying we’re furthest from the Sun may seem crazy, but it is true. Our distance from the Sun varies because Earth’s orbit is ever so slightly elliptical.
The reason for the seasons is something I mentioned above, the tilt of Earth’s axis toward or away from the Sun. We’re having Summer now in the northern hemisphere because we’re leaning over toward the Sun. Those in the southern hemisphere are into winter and tilted away from the Sun. The seasonal changes have very little to do with the Sun’s distance.
Have an astronomy or stargazing question? Email the StarGeezer.