Why is the Solar System Flat?

1 Watch the video and put the words into the gaps in the text.

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_____.
	shapeless
	planets
	comets
	planetary
	orbiting
	gravity
	gravity
	single
	rings
	mathematics
	collisions
	flat
	predict
	bump
	inexorably
	dimensions
	disk
	spinning
	particles
	cloud
	definitely
	complementary
	exist
	picture

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?

Physics. What if the Earth was hollow?

1 Watch the video and put the words into the gaps in the text.

Flying in a 747 from one side of the Earth to the exact opposite side would take about 22 hours… and while I know there’s a bit of rock in the way, that’s really going the long way round. So what if we did dig a hole all the way through the Earth, through the center, and jumped in? Well, Michael, you probably wouldn’t make it very far - that’s because of the Coriolis 1_____ (which is why a ball curves weirdly when you toss it while riding a 2_____ and why hurricanes always spin 3________ in the northern 4______). At the equator, the Earth is rotating eastwards at 1670 km/hr. As you go deeper, the bits of Earth around you are still spinning around once per day, but they don’t have as far to travel so they’re going at slower and slower 5______. If you jumped into a vertical 6_____, you’d soon be traveling east faster than the rock around you so that after falling only a few kilometers, you’d crash into the eastern wall. It might not be a 7______, but some miners near Lake Superior tried to test this by dropping cannon balls down a mile-long shaft - and the balls never reached the bottom. Ok, so what if the tunnel went from pole to pole, so the Coriolis effect didn’t 8______, and let’s also assume that there’s no air resistance, or 9______. Ok. Since the Earth’s mass is more concentrated close to the middle, 10____ would pull you down with roughly the same amount of force for the first 3000 km, or halfway to the center of the Earth - this familiar, constant force would 11 ______ you until you were falling 8 km every second, and the trip halfway to the middle of the Earth would only take 13 minutes. Soon after, you’d reach the Earth’s outer 12 ______, and this is the point in your journey where the pull of gravity would be strongest - but only slightly stronger than the force we’re used to on the 13 ______. As you continued to fall closer to the 14 ______, so much of the Earth’s mass would now be above you that it would begin to seriously cancel out the 15 ______ of the mass below, and the pull would weaken until you reached the center. Here, you’d experience no gravitational pull at all - or rather, the Earth would be pulling on you the same amount in all 16 ______, so you could 17 ______ freely around with no sense of ‘up’ or ‘down’. Except, remember, that you’d be speeding past at 22,000 miles per hour, or 6 miles a second. Once you passed the center, the whole process would 18 ______ and you’d gradually slow, pulled down weakly at first and then more strongly, until when you got to the other side, you’d stop moving and could step out on the surface, a mere 37 minutes, or one dryer cycle, later. Of course, the deepest we’ve ever been able to dig is the Kola Superdeep Borehole in Russia. But it only went down 12 km, which is only two thirds the length of Manhattan. They had to stop because it got too 19 ______: 180°C. And this is sort of the problem with digging a hole through Earth - Earth is hot, and 20 ______  in the middle. You can’t just dig a hole through it with shovels. But here is a question: wasn’t the middle of Earth wasn’t all ‘liquidy’, what if Earth was 21 ______, but weighed the same? Well, with its entire 22 ______  concentrated in a thin shell right under our feet, the Earth wouldn’t have a 23 ______  field any more, because that comes from the molten 24 ______  core. So we’d be totally 25 ______  to radiation from the solar wind and storms, and this means we’d see the 26 ______  everywhere. Look! The Northern-Southern-Eastern lights! And if you jumped inside the hollow Earth to escape the solar storm? Well, 27 ______ from the different parts of the 28 ______ Earth-shell would perfectly cancel out and you’d float freely about inside as if the Earth weren’t there at all! Of course, you’d better bring a 29 ______ suit, because there’s not nearly enough air ON Earth to fill up the entire INSIDE of Earth. But what if the entire inside of the hollow Earth were covered with mirrors? Henry, that’s ridiculous… for now. Ok, so back outside of the Earth, we wouldn’t really notice much difference from a gravitational 30 ______ - falling things would still accelerate at 9.8 m/s2, a baseball would follow the same 31 ______, and the moon would follow the same orbit around the Earth. Hey, Henry. Let’s go to outer space, right now. Bring your gun - this’ll all make sense later. C’mon.
	shaft
	merry-go-round
	disaster
	counterclockwise
	effect
	speeds
	hemisphere
	friction
	apply
	core
	attraction
	accelerate
	float
	directions
	gravity
	reverse
	surface
	center
	magnetic
	vulnerable
	hollow
	hot
	aurora
	molten
	mass
	iron
	spherical
	space
	gravity
	trajectory
	perspective

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 bits of Earth around you are going at slower and slower speeds. 

2.            The balls always reached the bottom, if they were dropped down a mile-long shaft.

3.            The Coriolis effect doesn’t apply to the falling objects.

4.            The Earth’s mass is more concentrated close to its middle.

5.            If the middle of the Earth had no air resistance, no friction; the result of passing through its center would be gradual acceleration.

6.            Digging Kola Superdeep was stopped because it was too cold.

7.            The Earth wouldn’t have a magnetic field anymore if Earth was hollow, but weighed the same.

8.            If the Earth was hollow people wouldn’t really notice much difference from a gravitational perspective.

9.            People wouldd be totally invulnerable to radiation from the solar wind and storms, if Earth was hollow, but weighed the same.

10.       Hurricanes always spin counterclockwise in the southern hemisphere.

4 Answer the Questions.

1.       What would happen if Coriolis effect didn’t apply and the tunnel through Earth went from pole to pole?

2.       How long would the trip halfway to the middle of the Earth take without air resistance, or friction?

3.       What is the deepest borehole?

4.       What is the problem with digging a hole through the Earth?

5.       Under what circumstances would people be able to see the aurora everywhere?