读 NG 的 Black Holes: Star Eater# LeisureTime - 读书听歌看电影
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三月份的这篇 Black Holes 文章很有趣,连我这种科学白痴都读懂了。。
Copy 其中的一部分关于suck和time的讨论。最后一段说的,不就是我们古人说的,天
上一天,地上万年吗?
这里是原文链接:http://ngm.nationalgeographic.com/2014/03/black-holes/finkel-text
It’s important to clarify a couple of things about black holes. First is
the idea, popularized in science fiction, that black holes are trying to
suck us all in. A black hole has no more vacuuming power than a regular star
; it just possesses extraordinary grip for its size. If our sun suddenly
were to become a black hole—not going to happen, but let’s pretend—it
would retain the same mass, yet its diameter would shrink from 865,000 miles
to less than four miles. Earth would be dark and cold, but our orbit around
the sun wouldn’t change. This black hole sun would exert the same
gravitational tug on our planet as the full-size one. Likewise, if the Earth
were to become a black hole, it would retain its current weight of more
than six sextillion tons (that’s a six followed by 21 zeros) but be shrunk
in size to smaller than an eyeball. The moon, though, wouldn’t move.
So black holes don’t suck. Easy. The next topic, time, is way more of a
mind bender. Time and black holes have a very strange relationship. Actually
time itself—forgetting about black holes for a moment—is an unusual
concept. You probably know the phrase “time is relative.” What this means
is that time doesn’t move at the same speed for everybody. Time, as
Einstein discovered, is affected by gravity. If you place extremely accurate
clocks on every floor of a skyscraper, they will all tick at different
rates. The clocks on the lower floors—closer to the center of the Earth,
where gravity is stronger—will tick a little slower than the ones on the
top floors. You never notice this because the variances are fantastically
small, a spare billionth of a second here and there. Clocks on global
positioning satellites have to be set to tick slightly slower than those on
Earth’s surface. If they didn’t, GPS wouldn’t be accurate.
Black holes, with their incredible gravitational pull, are basically time
machines. Get on a rocket, travel to Sgr A*. Ease extremely close to the
event horizon, but don’t cross it. For every minute you spend there, a
thousand years will pass on Earth. It’s hard to believe, but that’s what
happens. Gravity trumps time.
Copy 其中的一部分关于suck和time的讨论。最后一段说的,不就是我们古人说的,天
上一天,地上万年吗?
这里是原文链接:http://ngm.nationalgeographic.com/2014/03/black-holes/finkel-text
It’s important to clarify a couple of things about black holes. First is
the idea, popularized in science fiction, that black holes are trying to
suck us all in. A black hole has no more vacuuming power than a regular star
; it just possesses extraordinary grip for its size. If our sun suddenly
were to become a black hole—not going to happen, but let’s pretend—it
would retain the same mass, yet its diameter would shrink from 865,000 miles
to less than four miles. Earth would be dark and cold, but our orbit around
the sun wouldn’t change. This black hole sun would exert the same
gravitational tug on our planet as the full-size one. Likewise, if the Earth
were to become a black hole, it would retain its current weight of more
than six sextillion tons (that’s a six followed by 21 zeros) but be shrunk
in size to smaller than an eyeball. The moon, though, wouldn’t move.
So black holes don’t suck. Easy. The next topic, time, is way more of a
mind bender. Time and black holes have a very strange relationship. Actually
time itself—forgetting about black holes for a moment—is an unusual
concept. You probably know the phrase “time is relative.” What this means
is that time doesn’t move at the same speed for everybody. Time, as
Einstein discovered, is affected by gravity. If you place extremely accurate
clocks on every floor of a skyscraper, they will all tick at different
rates. The clocks on the lower floors—closer to the center of the Earth,
where gravity is stronger—will tick a little slower than the ones on the
top floors. You never notice this because the variances are fantastically
small, a spare billionth of a second here and there. Clocks on global
positioning satellites have to be set to tick slightly slower than those on
Earth’s surface. If they didn’t, GPS wouldn’t be accurate.
Black holes, with their incredible gravitational pull, are basically time
machines. Get on a rocket, travel to Sgr A*. Ease extremely close to the
event horizon, but don’t cross it. For every minute you spend there, a
thousand years will pass on Earth. It’s hard to believe, but that’s what
happens. Gravity trumps time.