Fast enough to escape earth's gravity and begin the shuttle era.

使其能以足够度逃离力，从此开始航天飞机时代。

Plants have evolved over millennia using the strong gravity on Earth.

利用上强大力，植物已经进化了数千年。

So, they escape Earth's gravity and drift off into space.

因此，它们逃离力，漂向太空。

The Moon continues on its gravitational dance with Earth, swinging around its orbit.

月继续与力共舞，绕其轨道旋转。

Jupiter's tides are hundreds of times stronger than Earth's, so no surprise there.

木星力潮比强数百倍，所以这并不奇怪。

Rockets must travel at least 25,000 miles an hour to escape Earth's gravity.

为了逃离力，火箭必须以每小时至少2.5万英里度飞行。

The gravity of earth is what makes flames rise and look like they do.

力使火焰升起，呈现出我们看到样子。

A spacecraft and basically everything else on Earth is held down by Earth's gravity.

上几乎所有物体都受到力压制。

That is a place where the gravity of the sun, moon and Earth are balanced.

那是一个太阳、月和力平衡方。

If we mess up the earth gravity assist, we die.

如果力助推搞砸了，我们会死。

That's right. We bring him in too late, and he's pushed out of Earth's gravity.

没错。如果减变轨时间太迟，舱体将脱离力范围。

It has gravity, but much less than the Earth because it's less massive.

它有力，但因为它质量比小，力也就小得多。

This is a point where the gravitational forces of the sun and Earth balance each other.

太阳和力在这里达到平衡。

Others thought the moon formed elsewhere in the solar system and was captured by Earth's gravity.

其他人认为月形成于太阳系其他方，并被力捕获。

Say you increase the size of Earth, so Earth's gravitational constant increases.

假设你增加了大小，力常数就会增加。

Elsewhere study finds that spaceflight may pose health risks to anyone spending time beyond earth's gravity.

其他方研究发现，太空飞行可能会给任何在力之外度过时间人带来健康风险。

Gravity may be weak here on Earth, but it's not so weak across the cosmos.

上力也许确微弱，但放眼宇宙，情况并非如此。

The gravitational effect of the Moon keeps the degree of tilt on the Earth's rotational axis constant.

月力使得自转轴倾斜保持在一定角度。

Even the Moon's low gravity, just one sixth of Earth's, could present a hazard to a tourist.

甚至月低力只有六分之一，对旅游者是个冒险举动。

We learn at school that we're constantly pulled down by Earth's gravity and that's why things fall.

我们在学校里学过，我们不断被力拉下，这就是物体下落原因。