Good morning! While I let my #coffee cool, I thought I'd kick off a thread describing my area of #astrophysics / #astronomy #research which I'll add to throughout the day. At the end, I'll mention how my work relates to what I think is the most amazing #fact about our time and place in the #universe.

Follow along and feel free to ask questions! I will try my best to get to them all!

Now... On to Tidal Dynamics... 🌎🌔

You might have heard that the #tides that cause #Earth's #oceans to rise and fall twice each day are caused by our Moon, but did you know that the same #Physics has the power to flex & churn other worlds to the point of melting?

Here is #Jupiter's moon #Io captured in the early 2000s by the Galileo spacecraft. It's surface looks really odd, so many different yellows, reds, and oranges. In the image a strange blue plume gives us a hint to what is going on...

#Volcanoes! 🌋and lots of them!

Io's close orbit to Jupiter leads to intense tidal forces which cause the moon to flex and squeeze like a rubber ball. That flexing grinds rocks inside the moon against one another creating _a lot_ of friction & #heat. There is so much heat that the entire moon's surface is covered by 🌋 and #lava flows!

The best part? Io isn't alone in experiencing this phenomenon! Here is #Saturn's moon #Enceladus taken in 2009 by the #Cassini spacecraft. There are strange whisps flowing from the surface.

By flying closer (and even through!) those clouds we learned that they are actually plumes of #water, #ice, and salts ejected from large gashes in #enceladus' south pole that we call the #tiger #stripes (📷: Close view of plumes taken by Cassini).

But Enceladus is tiny! Only about 15% the size of our Moon. Something so small should not have the energy to melt this much water let alone eject it into #space; the moon should be a frozen ball of ice and rock!

The reason? You guessed it, #tides!

But how do #tides work? Why is this happening to these moons and not other ones? What does this mean for our Moon and the Earth? What about #exoplanets??

Well my coffee has cooled down almost to Enceladus' temperature so we will have to pick this back up later today!

I ran out of coffee so its time to return to #tides!

We left off with some cool worlds that are affected by tidal forces, but what causes these forces?

To answer that we have to talk about #gravity! You know the force that keeps us down all the time? That stuff. Gravity is also what keeps our #Moon orbiting #Earth. Did you know the Moon is actually falling just like us? But it is also moving really fast to the side, so it keeps missing the Earth, we call this an #orbit.

Get ready for some #science (I will leave the #math for another day 😉)!

The force of #gravity is stronger the closer you are to a more massive object, like a #planet or #star, and weaker the further away you are.

In this image there is large circle which represents a planet. The arrows represent the pull of gravity. Their length represents the strength of that pull being exerted by a massive object (shown as a black dot). The further away you are from the dot, the weaker the pull of gravity.

You might wonder, if the force of #gravity is stronger the closer you are to an object, does that mean that if you are standing upright that your feet, being closer to the center of the Earth, feel a stronger pull of gravity than your head? You'd be right! A 1.7 meter tall person's head at sea level experiences about 0.00005% stronger pull than their feet!

This is wayyy too small for us to notice or to impact our #biology.

#Earth, our #Moon, and even you and I are mostly #rigid such that when one part of us moves the rest (hopefully!) follows pretty quickly. So the fact that our feet are being pulled slightly more than our heads doesn't really matter when it comes to keeping us on the ground. The _average_ force exerted across our body is more important.

This is also true for planets & moons, but in some circumstances all those little differences can start to matter.

These tiny differences are what we call #tidal #forces. Going back to the image from before, if we subtract the average length of all the arrows from each individual arrow we are left with this new image on the right: arrows closer to the dot are still pointing towards it while those on the opposite side are now pointing away from it!

This is what tidal forces look like on #Earth! Those peaks or "tidal bulges" are where our #ocean's high #tide occur (the dot in that case would be our Moon).