Y’know, if Shakespeare had been an astronomer, he’d have said that “there is a tide in the affairs of the Universe, and on such a full sea are we now afloat.”
He would’ve been right. You might just think of tides as the ocean going in and out every day, but in fact what astronomers call tides are a subtle but inexorable force that have literally shaped most objects in the Universe.
And to understand tides, we start with gravity.
Gravity is a force, and it weakens with distance. An important thing to note is that we measure gravity from the center of mass of an object, not its surface. One way to think of the center of mass of an object is the average position in an object of all its mass. For an evenly distributed sphere, that’s it’s …show more content…
These moons all show the same face toward their planet!
Now wait a second. If the Moon has gravity, which causes tides, and is the root cause behind all these shenanigans, what about the Sun? It’s even bigger than the Moon!
Tides depends on the gravity from an object, and your distance from it. The Sun is far more massive than the Moon, but much farther away. These two effects largely cancel each other out, and when you do the math, you find the Sun’s tidal force on the Earth is just about half that of the Moon’s. The way the Sun’s tidal force and the Moon’s tidal force interact on Earth depends on their geometry, which changes as the Moon orbits us.
At new Moon, the Earth, Moon, and Sun are in a line. The Moon’s tidal force aligns with the Sun’s, reinforcing it. This means we get an extra high high tide and an extra low low tide on Earth. We call this the spring tide.
When the Moon is at first quarter, the tidal bulge from the Moon is 90° around from the Sun’s; high tide from the Moon overlaps low tide from the Sun. We get a slightly lower high tide, and a slightly higher low tide. We call those neap
He would’ve been right. You might just think of tides as the ocean going in and out every day, but in fact what astronomers call tides are a subtle but inexorable force that have literally shaped most objects in the Universe.
And to understand tides, we start with gravity.
Gravity is a force, and it weakens with distance. An important thing to note is that we measure gravity from the center of mass of an object, not its surface. One way to think of the center of mass of an object is the average position in an object of all its mass. For an evenly distributed sphere, that’s it’s …show more content…
These moons all show the same face toward their planet!
Now wait a second. If the Moon has gravity, which causes tides, and is the root cause behind all these shenanigans, what about the Sun? It’s even bigger than the Moon!
Tides depends on the gravity from an object, and your distance from it. The Sun is far more massive than the Moon, but much farther away. These two effects largely cancel each other out, and when you do the math, you find the Sun’s tidal force on the Earth is just about half that of the Moon’s. The way the Sun’s tidal force and the Moon’s tidal force interact on Earth depends on their geometry, which changes as the Moon orbits us.
At new Moon, the Earth, Moon, and Sun are in a line. The Moon’s tidal force aligns with the Sun’s, reinforcing it. This means we get an extra high high tide and an extra low low tide on Earth. We call this the spring tide.
When the Moon is at first quarter, the tidal bulge from the Moon is 90° around from the Sun’s; high tide from the Moon overlaps low tide from the Sun. We get a slightly lower high tide, and a slightly higher low tide. We call those neap