引力中心

Alternatively, the spectral softening above 2 GeV could be due to gamma-ray absorption via photon-photon pair production on the soft X-ray photon field of the host active galactic nucleus, but such an interpretation would require the dissipation region to be located very close (l~100 gravitational radii) to the black hole, which would be inconsistent with the X-ray spectrum of the source.

另外的关于2 GeV以上能谱变软的可能解释是高能光子和寄主活动星系核的软X射线辐射场通过电子对产生反应而被吸收，但是这个解释要求反应区域要很靠近中心黑洞(1~100倍引力半径)，这和3C 454.3的X射线测量谱相矛盾。

In the core of the larger spiral structure of NGC 1300, the nucleus shows its own extraordinary and distinct "grand-design" spiral structure that is about 3,300 light-years long. Only galaxies with large-scale bars appear to have these grand-design inner disks — a spiral within a spiral. Models suggest that the gas in a bar can be funneled inwards, and then spiral into the center through the grand-design disk, where it can potentially fuel a central black holes. NGC 1300 is not known to have an active nucleus, however, indicating either that there is no black hole, or that it is not accreting matter.

星系演化除了像两个星系相撞那样的剧烈作用之外，还有自己内部很慢的演化，因为一个星系总会有一些引力不稳定，如上图中的NGC1300，它是一个棒旋星系，这种bar结构导致的引力不完全对称会驱使很多气体和尘埃损失角动量往里面落，我们可以清楚的看到dust lanes，有点像黑洞的吸积，但这个星系是个非活动星系，目前还没有黑洞存在的明确证据，but我相信肯定是有的，没有比在星系中心放一个黑洞再完美不过的事情了，或许这些下落的dust lanes是黑洞发光的开始呢。

What is the center of gravity?

地球引力的中心是什么？

Challenges are gifts that force us to search for a new center of gravity.

挑战是强迫我们寻找新的引力中心的礼物。

"This changes the mother's center of mass, which is a critical point in any three-dimensional body on which gravity acts."

"这改变了母亲的身体中心，这在地球引力作用于任何三维身体上是非常重要的一点。"

The total gravity force on the star from the stars enclosed by its circular orbit can be treated as if they are concentrated at the center.

对于一个离中心为 r 的恒星来讲，来自轨道内的恒星的引力与把它们集中在星系中心的一样，来自轨道外的恒星的引力合力为零。

Enceladus' orbit around Saturn is eccentric," Mitchell says. It's just enough off of circular that the effect of gravity on the moon is different from one point to another, and different from the planet's other moons."

Enceladus的公转轨道是离心圆，"Mitchell说，"是围绕一个中心绕圈转动，所以在圈的每一个点上的引力是不同的。

All objects are pulled towards the centre of the Earth by the force of gravity.

所有的物体都由于引力而拉向地球中心。

The dark matter only interacts gravitationally and so it stays at the center of the sound wave, the origin of the overdensity.

暗物质仅通过引力进行相互作用，所以其呆在声波的中心，也即声波起源的高密度区域。

Newton showed that the motions of objects on Earth and of celestial bodies are governed by the same set of natural laws by demonstrating the consistency between Kepler's laws of planetary motion and his theory of gravitation, thus removing the last doubts about heliocentrism and advancing the scientific revolution.

他通过论证开普勒行星运动定律与他的引力理论间的一致性，展示了地面物体与天体的运动都遵循着相同的自然定律；为太阳中心说提供了强有力的理论支持，并推动了科学革命。

With Death guitarist Schuldiner adopting vocal duties, the band made a major impact on the scene.

随着死亡的吉他手Schuldiner接受主唱的职务，乐队在现实中树立了重要的影响。

But he could still end up breakfasting on Swiss-government issue muesli because all six are accused of nicking around 45 million pounds they should have paid to FIFA.

不过他最后仍有可能沦为瑞士政府&议事餐桌&上的一道早餐，因为这所有六个人都被指控把本应支付给国际足联的大约4500万英镑骗了个精光。