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If anybody has a more robust answer for the brain freeze question let me know! Sensation is complicated!!

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Good morning John.  
I just discovered that the way people used to ask the science side of Tumblr questions, people very very occasionally ask the science side Twitter questions, so I just searched for science side of Twitter and I'm going to answer as many questions as I can in 4 minutes.

"Are constellations different in the Southern Hemisphere? Like is the Big Dipper and Zodiac down there?"
The constellations themselves don't change, but you can see different ones depending on where you are on Earth. If you were on the North Pole, and the Earths' axis weren't tilted, then you could only ever see just the top half of the constellations, and the same for the South Pole. Now it's a little complicated, cuz it's tilting, so your perspective actually changes a little bit throughout the year. But if you're right on the equator, as the year goes by, you could actually see almost all of the sky, though a of of it will be really close to the horizon, so, hard to see.
If you find this confusing, it's because it's very confusing. The Earth is revolving while it's rotating, and we're also thinking about us being in different places on a rotating and revolving thing. There are some people who get their heads all the way around this, but they think about it for a living. 

"How do I stop?"
Well- God- I don't know. I've been told that you need an equal and opposite force, I haven't found one yet, but I've been assured that they exist. 

"What are these giant quasar-lookin' stars, though?"
That's just a star that is in our galaxy. All those background things in this image, those are galaxies that are like, billions of miles away, so its literally millions of times closer, so it looks a lot brighter, and super bright stuff, when seen by the James-Webb space telescope,  has these diffraction spikes which is caused by the shapes of the mirrors. 

"How many calories on average do you burn taking a massive dump?"
I mean not zero. Interestingly, the anus is a muscle that is almost always contracting. Um, so its always burning energy, until it is loosened, in that case it's burning less energy. But I think that that's more than outweighed by a lot of other muscle contractions that are probably going on during the dump, plus you know any anxiety you might be experiencing might also burn a little extra calories. 

"Why does ketchup have to be refrigerated? Isn't it primarily vinegar, salt and sugar, all of which are preservatives?"
Fascinating question. When we talk about preserving foods, we're talking about two different things. 
One is preventing bacteria from growing in it, which is gonna spoil it and make it dangerous. High concentrations of vinegar, salt, and sugar will all prevent bacterial growth.  
But we are also concerned about the complicated molecules in the food stuff breaking down into other molecules that might just, taste less good. Once the ketchup is exposed to a good deal of oxygen, those reactions are going to happen more quickly, and so we want to slow them down, and one way to do that is by having less heat in the system. So, putting it in the rfrigerator. 

"Hey Science Twitter: Any tips for reducing eye strain when using a microscope?"
Using a microscope is absolutely a lot of this, which is like hunch and eye strain, so I suggest you get one of these, which the Micro Cosmos Microscope comes with. It's a cellphone holder. You put the eyepiece in here, and then you clamp your cellphone in here, and you put it on, and then you're looking through your microscope like there's a screen! 
Now, you do have to be able to choose which lens your cellphone is looking through, which the Iphone doesn't let you do by default, there are apps that let you do that though, the one I use is called Procam.

And this one is specifically for me!
"How did I get an actual brain freeze without consuming any liquids purely from pouring cold water over my face?" 
So, a brain freeze is a kind of nerve pain. It's your brain misinterpreting a confusing signal. Getting suddenly cold will cause all the blood vessels near your nerves to contract. And then, when the warm back up very quickly, they will open back up and that will cause a flood of blood to the area that will just be confusing to the nervous system. And in your face and head, all these sensory nerves are really closely packed together, so it's just more common for signals to get confused. I think. I haven't heard of this happening before, but it totally seems like something that could happen. 

"Does sound travel in outer space?"
Sound is just a bunch of molecules slapping into each other, so you need a bunch of molecules really densely packed together to carry that signal. In an atmosphere, we have that. This is actually a pretty thick soup of molecules right here. In space, there are basically no molecules, so they can't knock into each other to carry sound, which is a good thing because the sun is so energetic that if space carried sound as well as our atmosphere, it would be a constant hundred-decibel roar that we would never not experience. 

"What's a good time to wake up my friends, because my phone is dying, and I need my charger block from their room."
What you're gonna want to do is get two potatoes and a copper wire. And I'm kidding. I've just looked at your tweet, it's from 2:27 AM, you don't need to be on Twitter any more. Bedtime, it's bedtime.

John, I'll see you on Tuesday.