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### You Can Play With Escape Velocity--Without Leaving the Planet

If you like cool-sounding science terms, escape velocity should fit the bill. But what the heck does it even mean? What goes up, must come down. But how about an experiment to see if it's really true? I'm going to take a ball and toss it up.

### You Can Find the Gravitational Constant with String and a Mountain

There are quite a few fundamental constants. These are things like the speed of light (c) the charge on an electron (e), and the Planck constant (h). These constants are determined with some type of interesting experiment. The first values of these constants were often difficult to find--the speed of light, for example, was calculated by tracking the moons of Jupiter. Of course, now we have much better methods to get a very precise value for the speed of light. We don't need to resort to moons anymore.

### In 'Guardians of the Galaxy Vol. 2,' Planet Sovereign Defies Physics

One of the great things about movies set in space is that the writers have the opportunity to come up with some fantastically crazy situations. Just look at the planet Sovereign, revealed at the beginning of Guardians of the Galaxy Vol. 2. Don't worry about why the Guardians are on this planet too much--instead, let's just focus on the planet itself. However, there is a small physics problem here. Planets, you might have noticed, are spherical. The planet Sovereign is decidedly not.

### The Independence Day: Resurgence Spaceship Has Its Own Gravity

I'm not sure what's happening in this trailer for Independence Day: Resurgence, but here's what I think: The aliens are back and not at all happy about losing the battle on Earth. The ship is so massive that it gravitationally pulls objects (like buildings) toward it. Again, this is just my speculation from the video. What kind of mass would a spacecraft need to pull things off Earth? Let's take a look at gravity and then make an estimate.

### How to Weigh the World - Facts So Romantic

Straining under the task of holding up the Earth, this Titan god likely got a good idea of how much the Earth weighed. But none of us are so conveniently situated. How could a mere mortal, a tiny person residing on Earth's surface, carry out their own estimate of Earth's weight? Where would--where could--you possibly place the scale? A firm answer didn't arrive until the Englishman John Michell figured out a way.