We're Clay-- 

And Christina from Mrs. Hood's second grade class in Columbia, Missouri. Our question is-- 

Why do stars twinkle instead of shine steadily? 

Hello. My name is Anna Frebel, and I'm a professor here at MIT. I'm actually an astronomer, and I'm going to answer your questions about space. You ask why the stars are twinkling at night, and we even have little songs-- "Twinkle Twinkle Little Star." 

But you're right. The stars themselves are actually not twinkling. It is the Earth's atmosphere that makes the stars twinkle. The real stars, of course, are spheres of hot gas, and they don't have spikes at all. 

But when the light from the star travels through the atmosphere of the Earth, which is what we call the sky, what you see, all the air where the clouds are and so forth, that air, the mass of air, actually distorts the star light. You can imagine there's a lot of wind going on in the atmosphere, and it just sways the starlight a little bit left and right, and back and forth, and so forth. And so the round star light suddenly gets distorted in all sorts of direction, and it looks like it has spikes. 

I'm Ashley from Ms. Nelson's second grade class in Columbia, Missouri. My question is do stars move at night, or do they just look like they're moving because of the Earth spinning? 

Someone else asked a related question about stars and why it looks like that they're moving on the sky. The stars themselves are actually not really moving. Sometimes they move a tiny, tiny little bit, but it takes years for astronomers to actually see that they've moved with respect to each other on the sky. 

However, every night, the stars come up, they rise, and then they go down in the same way that the sun rises in the morning and goes down in the evening, and that is because Earth is actually moving. So you have to imagine that all the stars in the sky are actually fixed, and what we are doing on Earth is we're doing this. 

Here are the stars, and I'm doing this. I'm essentially moving my head across the star, and that is exact same thing as me looking in one direction and the stars doing this. So to us, it looks like the stars are moving because we think we are fixed on Earth, but that is just the perception that we have living on this planet. For real, the stars are fixed in the universe, and we are moving. We're spinning around, and we are even moving with the Earth around the sun, so that results in a lot of apparent motion on the sky.