1 Watch the video and put the
words into the gaps in the text.
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Our Sun and the Earth, and all the planets and moons and dwarf planets
and asteroids and 1____ - the solar system, in short, formed about 4.6
billion years ago from a nebulous cloud of swirling gas and dust which
coalesced thanks to the irresistibly attractive force of 2____. However, this
nebula started off more or less as a big 3____ blob. So how did our solar
system end up with all the planets and their moons 4____ in a flat disk? I
mean, we’ve all seen the planetary model of the atom, which is definitely
wrong when applied to atoms, but it also kind of suggests that 5____ might revolve
around the sun every which way. So is our solar system somehow special in its
flatness? Or is the 6____ model of the atom doubly wrong?
Well, our solar system definitely isn’t alone, many exoplanets’ star
systems are 7___, a lot of galaxies are flat, black hole accretion disks are
flat, Saturn’s 8___ are flat etc. So why, when there’s all of 3D space to
fill, does the universe have this preference for flatness? The answer has to
do with two things: 9___ and the fact that we live in three dimensions. Bear
with me. Anytime a bunch of objects held together by 10___ are zooming and
circling around, their individual paths are nearly impossible to 11____, and
yet, collected together they have a 12____ total amount that they spin about
their center of mass. It may be hard to figure out exactly what direction
that rotation is in, but the 13____ implies there must be some plane in which
the cloud taken as a whole spins.
Now, in two dimensions a cloud of particles rotating in a plane is
flat by definition, it’s in two 14____. But in three dimensions, even though
the rotation of the cloud is given by one plane, 15____ can whiz around far
up and down from that plane. As the particles 16____ into each other, all the
up and down motion tends to cancel out, its energy lost in crashing and
clumping. Yet the whole mass must continue spinning 17____, because in our
universe the total amount of 18____ in any isolated system always stays the
same. So over time through collisions and crashes, the cloud loses its loft and
flattens into a spinning, roughly 2 dimensional 19____ shape, like a solar
system or a spiral galaxy.
However, in four spatial dimensions, the math works
out such that there can be two separate and 20____ planes of rotation which
is both really, really hard for our 3D-thinking brains to 21____ and also
means there’s no up and down direction in which particles lose energy by
collisions. So a cloud of particles can continue being just that... a 22____.
And thus, only in three dimensions can a nebula or infant galaxy start out
not flat and end up flat which is 23_____ a good thing because we need all
that matter to clump together in order for stars and planets to form, and for
us, even those of us who think atoms look like this, to 24_____.
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shapeless
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planets
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comets
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planetary
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orbiting
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gravity
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gravity
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single
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rings
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mathematics
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collisions
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flat
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predict
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bump
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inexorably
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dimensions
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disk
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spinning
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particles
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cloud
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definitely
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complementary
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exist
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picture
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2 Vocabulary focus. Study the words and word combinations, practise
their translation, spelling. Check your knowledge
in the test. Play vocabulary game and set your own vocabulary game record.
3 Mark the following statements as True or False.
1.
The solar system is flat.
2.
There aren’t any other planets beyond our solar system.
3.
It’s easy to predict the way of a particle in a system
of many particles.
4.
The total amount of spinning in any isolated system
always stays the same.
5.
It’s possible for the solar system and us to exist
because of the phenomenon of flatness in three-dimensional space.
6.
The rules of mathematics are the same in three- and
four- dimensional space.
4 Answer the Questions.
1.
When was the solar system formed?
2.
What objects in our universe are flat?
3.
What motion tends to cancel out in the spinning cloud
of particles?
4.
What characteristic of isolated spinning system of
particles always stay the same?
5.
Why is flatness of nebulas and systems of particles in
general so important in our universe?
