This isn’t the usual twin paradox that always grabs the headlines… The version involving gravity is actualy the one that keeps your phone working. Instead … Read More

We usually think of gravity as a force that pulls us down. But it is more complex than that; it is actualy the opposite of … Read More

Think about it: Gravity is something you consider to be pretty much constant. Like your fridge humming in the background, right? Because you live on … Read More

The currency of spaceflight is exhaust velocity. It show up on the data sheet as just a number, but it’s a measure of how much … Read More

There’s one number that matters most in rocketry: specific impulse. It’s the efficiency metric for converting fuel into movement. A bigger number mean more thrust … Read More

To get something into low Earth orbit, you drop some serious money in fuel (millions of dollars per satellite). Then you send it high up … Read More

The idea behind escape velocity is that it’s the speed at which an object will never again fall back down once propulsion stops. Think more … Read More

But the universe is not a sound wave reflecting off a speeding automobile. When you’re measuring the light coming from something traveling at a significant … Read More

As light traverses space, it stretches and compresses in response to that journey. And that tells us what happened along the way. Called the Doppler … Read More

Heat rises they say, right? And heat radiates, too. Your hand resting on a desk give off energy, as does a light bulb’s glowing filament. … Read More