Joe Raedle via Getty Images But even staging is not enough; eventually the rocket will run out of propellant. But if the rocket goes fast enough, it can run out of propellant and still continue to coast away from Earth forever, without gravity pulling it back. It’s like riding a bike: build up enough speed and eventually you can coast up a hill without pedaling. And just like there’s a minimum speed required to coast the bike, there’s a minimum speed a rocket needs to coast away into space: 25,020 mph (about 40,000 kilometers per hour). Scientists call that speed the escape velocity. A rocket needs to go that fast so that the momentum propelling it away from Earth is stronger than the force of gravity pulling it back. Any slower, and you’ll go into an orbit of Earth. Escaping Jupiter Bigger, or more massive, objects have stronger gravitational pull. A rocket launching from a planet bigger than Earth would need to achieve a higher escape speed. For example, Jupiter is the most massive planet in our solar system. It’s so big, it could swallow 1,000 Earths. So it requires a very high escape speed: 133,100 mph (about 214,000 kilometers per hour), more than five times the escape speed of Earth. But the extreme example is a black hole, an object so massive that its escape speed is extraordinarily high. So high, in fact, that even light – which has a speed of 370 million mph (about 600 million kilometers per hour) – is not fast enough to escape. That’s why it’s called a black hole. Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to CuriousKidsUS@theconversation.com. Please tell us your name, age and the city where you live. And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.