Начинаем рубрику "Просто на английском". В этой рубрике будут объяснятся различные термины на английском, объяснение будет перетекать от базовых слов, уровня Elementary/Pre-intermediate, до сложных концептов уровня Advanced ближе к концу текста. Попробуйте дойти до конца.
Сегодняшняя тема - гравитация.
Gravity
What is gravity?
Gravity is the force that pulls the objects to the ground. Zero gravity makes objects fly around. Astronauts in space feel zero gravity. Gravity in space pulls moons to orbit around planets, planets to orbit around a sun, suns to orbit around galaxies.
How does it work? If you put a heavy object in the middle of your bed, the sides of the bed will bend a little towards the center, where you have your heavy object. Same way gravity of a heavy object bends the space around it so the object "falls" towards it.
How strong is gravity?
Gravity is a weak force. It does hold planets in the solar system, but there are ways to break free from gravity and leave the planet or even solar system. We, humans, created devices which able to do so, such as rockets.
To leave the surface of our planet you have to create force big enough to make the rocket move 7.9 km/s. That speed is called escape velocity. In order to leave the gravity of our planet, the speed should go up to 11km/s. If you want to make some object leave our solar system you have to make it move faster then 618km/s.
How does gravity affect mass and time?
Everyone knows their weight, but would your weight be the same on different planets? Would you have wright in space? There is a difference between mass and weight. All of the objects have mass. Mass is basically the sum of all the atoms that make the object up. Weight, on the other hand, is the force of gravitational pull of the planet or the sun. For example, your weight will be different on the moon because the moon gravity is weaker compare to the Earth, but the mass will stay the same.
Another interesting property of gravity it makes things slower. The closer you are to the source of gravity, the slower your time relative to the further places. It was shown in The Interstellar when the group of main characters landed on the planet near the black hole, they spent only 2 hours there but for the guy who stayed on the board of the ship it was 27 years.
In the case of the Earth, our gravity pull is not that strong so the difference between our time and astronauts up on the orbit is less than a second, but nevertheless, those who spent quite a lot of time up there probably several minutes younger than they should be.
The end
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