# Galaxy plane and Earth's orbit. Connection to seasons?

From my understanding, the Earth (Solar System) crosses a center line of the galactic plane (ecliptic *edit wrong definition, sorry!), while orbiting around the Sun. The Sun also wobbles up and down along this same center plane, while orbiting the galactic center.

Are there any connections of this rhythm to our seasons or climate here on Earth? Are there any definitions or any sort of study, reference, or name, for this concept?

• There is no relationship between the ecliptic plane and the plane of the Sun's orbit around the galaxy. I don't understand what you mean by "galactic plane (ecliptic)". Please clarify. Commented Dec 20, 2022 at 23:31
• The plane of the galaxy is different from the ecliptic, so "centerline of the galactic plane (ecliptic)" is confusing. The plane of the galaxy runs through Scorpius/Sagittarius, Scutum, Aquila, Cygnus, Cassiopeia, and so on. The ecliptic plane runs through Virgo, Libra, Scorpius, Sagittarius, Capricornus, and so on. Please confirm you are asking about the plane of the galaxy. Commented Dec 21, 2022 at 3:37
• Yes I understand the ecliptic is different. To clarify, the ecliptic is angled and would be like the sun(our) as the hub, and the solar system the spokes/wheel. The sun is in the center and wobbles up and down along the galaxies center plane. Which is potentially too large for us to even measure. I’m wondering if the the change in galactic elevation, of the planet(s) on the ecliptic is affecting us biologically or the climate? Commented Dec 22, 2022 at 0:46
• The final para in ProfRob's answer is important: the Earth does NOT cross the galactic plane while orbiting the Sun, so there is no seasonal connection at all. Commented Dec 23, 2022 at 16:35

I think you are asking whether there are any consequences for the Earth of the Sun and Solar System crossing the galactic plane$$^1$$? Yes, there have been a number of studies suggesting that their might be an affect on the Earth in terms of an increase in cometary bombardment due to tidal forces in the Galaxy. However, there is no conclusive evidence that this has happened.

The orbit of the Sun around the galaxy is basically a circle, but superimposed on that are small, roughly sinusoidal excursions up and down and in and out. The vertical oscillation has a period of about 70 million years, which means the Sun passes through the Galactic plane every 35 million years. See for example How far is the Earth/Sun above/below the galactic plane, and is it heading toward/away from it? and What mechanism causes oscillations of the solar system's orbit about the galactic plane?

How could this affect the Earth? Well, the amplitude of the motion is about 100 pc, which is only half the scale height of the galactic disc. This will mean the local stellar density around the Sun will change a little. But since stellar close encounters are in any case rare, this is unlikely to provide a distinct modulation in any phenomena on Earth.

A better bet might be the changing tidal influence of the galaxy on the Oort cloud. Some calculations (e.g., Matese et al. 1995) have suggested there might be effects sufficient to modulate the rate of comets entering the inner solar system. This could result in impacts, mass extinctions, climate events etc. Gardner et al. (2011) calculate that the cometary flux would be modulated by about 30 per cent.

The observational evidence for such episodes is reviewed by Rampino & Prokoph (2020). They look at 58 analyses of cratering and conclude there is some evidence of a 26 million year periodicity and it is tempting to associate this with the galactic plane crossings (though the period is a bit discrepant). The problem with this interpretation is that most of the cratering isn't due to comets from the Oort cloud, and material in the inner solar system and asteroid belt would not be affected by galactic tides in the same way.

$$^1$$ The orbit of the Earth around the Sun has no bearing on this issue. You might be confused by the scale of the diagram in the source you link to. The Earth does not cross the galactic plane once per orbit and the size of the Earth's orbit is tiny compared with the excursions the entire Solar System makes above and below the galactic plane.

• Wonderful responses. Thank all of you for your input and help. I was under the assumption, earth would be so tiny - in comparison to the galactic plane. But, I had to ask. A metaphor here would be like, comparing hairlines to km? Commented Dec 23, 2022 at 18:20