Thanks to Skillshare for supporting this episode of SciShow.

The first 1000 people to click the link in the description can get a two-month free trial of Skillshare's Premium membership. {♫Intro♫}. On an average day, it can be easy to forget that you live on a rock in space that's constantly interacting with other celestial objects.

There are obvious clues from the Sun and the Moon, like the sunset and the tides. But those aren't the only noticeable effects of celestial bodies on Earth. Scientists have found at least three cycles in nature that can be traced back to the alignment of the planets.

And while they won't tell you anything about your love life or personality, by studying them, we can learn about our planet's past and future—and even how the solar system has changed. People have known for a long time that the Sun goes through an 11-year cycle. At the peak, its surface is full of flares and sunspots, and at the lowest point, things are pretty calm.

And, since at least the 1800s, scientists have suspected that that cycle might somehow be tied to the positions of the planets. Problem was, the gravitational pull of the planets on the Sun is pretty weak—so no one understood exactly how that would work. Then, in studies published in 2016 and 2019, scientists examined a thousand years' worth of data on solar activity and planetary positions.

They concluded that there are three planets that have a weak but noticeable effect on the Sun, especially when they all line up: Venus and Earth, because they're relatively close, and Jupiter, because it is so massive. Every 11 years, those planets form a line with the Sun, either on the same side or the opposite ones. And over that thousand years' worth of data, that alignment has been followed by a minimum in solar activity a few years later.

Now, scientists think they finally understand why. While the combined gravitational tug of these planets doesn't add up to much, it's enough to k influence the plasma at the Sun's surface. And according to models, that's enough to cause a flip in the Sun's magnetic field—resetting the cycle of solar activity every eleven years.

We haven't had a memorable solar storm in a while, so this idea of solar activity might seem kind of abstract, but powerful outbursts from the Sun can have a significant impact on Earth. Back in 1859, a severe solar storm wiped out telegraph systems, and a similar storm would be very bad for our electric grid today. Even relatively mild solar weather occasionally blocks radio communications or messes with satellites.

So the alignment of the planets, which drives solar activity, has real effects on our lives. But other planets don't just affect us indirectly. Through their interaction with the

Sun: the positions of Jupiter and Venus can also directly influence Earth. Once again, scientists predicted this was the case long before they had any evidence of it. See, models of the planets' orbits show that when Jupiter and Venus line up with Earth on the same side of the Sun, they stretch out Earth's orbit, making it 5% more elliptical than usual. That happens every 405,000 years, and scientists had a pretty good idea that it drove shifts in climate, but they didn't get their first concrete evidence until 2018.

That year, a team of researchers dug up a sediment core—basically, a tube of dirt—extending more than 500 meters below the Arizona desert, and representing hundreds of millions of years of history. Once they'd established the ages of the different layers of the core, they saw that, on a large scale, climate patterns repeated themselves every 405,000 years. Since that stretched-out orbit ever-so-slightly changes the amount of sunlight reaching our planet, it makes summers and winters more extreme, and wet and dry periods more intense.

In fact, from that one column of earth, scientists were able to confirm that this climate cycle has been repeating like clockwork for at least 215 million years. The effect is subtle over short time periods, but researchers have already begun pinning certain environmental and ecological events to this climate pattern—like changes in the types of dinosaurs that were around. So, the movements of the planets can help us understand patterns in Earth's geological record and even help us predict certain events in the future.

But the effect of the planets' movement on Earth may also help us understand the movement of the planets themselves. See, the previous two cycles dealt with pretty short timescales, astronomically-speaking. And in the short term, planetary motions are basically like clockwork.

But thanks to subtle gravitational interactions, planets' paths slowly change over time. We don't know exactly how they've changed, though—because you can only assume so much based on how planets move today. In fact, orbital models can only go back about 60 million years, which is a blink in the life of the solar system.

To get a model that goes back any further, you need more data about the planets' positions in the past—and scientists have found exactly that… in Earth's geological record. Back in the 1980s, scientists analyzed another core of sediment drilled from the Earth—this one from a former lakebed in New Jersey. Layers of mud preserved records of different water levels in the past—and in those layers, there was an unusual cycle.

It started out repeating every 1.75 million years, but it slowed down until, today, it's repeating just every 2.4 million years. In 2018, scientists found the same irregular cycle in the core from Arizona. They believe it's caused by changes in the orbit of Mars, which, again, subtly warps.

Earth's orbit in a way that creates shifts in the climate. What's exciting is that by connecting the climate cycle to planetary positions, scientists could use this evolving cycle to pin down the movements of the planets. Essentially, this gives us new data to put into models of the solar system and look back even further than 60 million years.

In other words, climate clues locked in Earth's soil could help us figure out how planets moved in the past. So not only do other planets have real effects on Earth, but those effects can help us understand our relationship with other celestial bodies over time. While our planet documents history in its soil, maybe you are interested in documenting some stories of your own.

And no matter how you want to do that, Skillshare can help you learn the ropes. Skillshare is an online learning community to help you create and explore. For instance, if you ever wanted to try filmmaking but don't have all the expensive equipment, you might like Skillshare's course on iPhone filmmaking—which shows you how to make cinematic films with just your phone.

An annual Skillshare subscription is less than $10 a month, and with a Premium membership, you can get unlimited access to its classes and communities. To try out a two-month free trial of a Premium membership, click the link in the description. And as always, thank you for watching SciShow Space. {♫Outro♫}.