Name: 為什麼行星是球形的？ 加上9個更多的視頻。#aumum (Why are planets spherical? plus 9 more videos.. #aumsum)
Uploaded: 2021-01-14T08:10:38.000Z
Duration: 10 min 59 s
Description: 【看影片學英語】數萬部 YouTube 影片，搭配英漢字典即點即查，輕鬆掌握單字發音與用法，長久累積看電影不必再看字幕。

Planets are round because of the force of
gravity.

Gravity acts as if it originates from the center of a planet and pulls each point of the planet towards it.

Hence, the only way for everything on the surface to be equally close to its center is to form a round shape.

This is because planets spin on their axes.

When planets spin, things near the equator
tend to move away from the center due to centrifugal force, resulting in formation of an equatorial bulge.

Because of this bulge, the equator of a planet becomes farther from its center than its poles, creating a roughly spherical planet.

It is because a magnifying glass is actually
a convex lens.

A convex lens is thicker in the middle and
thinner at the edges.

This shape of the convex lens makes the parallel rays of sunlight to refract such that they converge or come together at a point.

So, when they come together, do they have
a party?

As the rays converge, the concentration of sunlight at that point increases, thus producing heat.

This heat starts a fire which eventually causes the paper to burn.

The twinkling of stars is due to atmospheric refraction.

Atmospheric refraction is the bending of light caused by the earth's atmosphere.

I thought atmospheric refraction is the bending of my body due to earth's atmosphere.

Earth's atmosphere is changing continuously.

When the light of a star travels through space towards us, the continuously changing earth's atmosphere refracts or bends the light by different amounts and in different directions every moment.

When the atmosphere refracts more starlight towards us, the star appears bright and when the atmosphere refracts less starlight, the star appears dim.

In this way, the amount of starlight reaching our eyes increases and decreases causing the star to appear twinkling.

Because personally, I am fond of spherical
shapes as compared to squares.

Surface tension is the property of liquids
by which surface molecules of a liquid try to hold the liquid together by acquiring minimum surface area and acting like a stretched membrane.

You know what, everything just went over my head.

Inside a drop, each water molecule is pulled with a force by its neighboring molecules.

As these forces are equal and opposite, they get neutralized.

However, the molecule present at the surface is not attracted outwards.

It is attracted only inwards and sideways.

But because of the inward force, each surface molecule contracts to form a shape that has minimum surface area which is a sphere.

Resonance means to keep calm and balance.

Every object when struck vibrates at its natural frequency.

If we make sound having a frequency which matches the object's natural frequency, then that object starts to vibrate.

So, this was the reason why my legs started to move when the music system was switched on.

Every glass is made up of different materials.

However, all of them have a natural resonant frequency.

Hence, when we make sounds which match their resonant frequencies, the glasses start to vibrate.

As glass is a brittle material, louder the
sound, more violently will it vibrate causing the glass to shatter into pieces.

Why is it difficult to pull a boat on the
beach than on the sea?

You will find it difficult to pull the boat
on the beach.

At least now try to pull the boat on the sea.

Friction is the force which opposes the motion of an object.

It always acts in the direction opposite to
the direction of motion.

The amount of friction depends upon the texture of an object and the surface on which it is being moved.

Rough textures or surfaces offer greater friction as compared to smooth textures or surfaces.

Do you want to say that my brand new boat
has a rough texture?

Even though the texture of the boat is almost smooth, the small particles of sand present on beach form a rough surface.

Hence, when we pull the boat on beach, the
sand particles offer greater friction and oppose the motion of the boat.

Thus making it difficult to move the boat on beach.

字幕列表影片播放

為什麼行星是球形的？加上9個更多的視頻。#aumum (Why are planets spherical? plus 9 more videos.. #aumsum)

eventually

acquire

force

texture

為什麼行星是球形的？ 加上9個更多的視頻。#aumum (Why are planets spherical? plus 9 more videos.. #aumsum)

eventually

acquire

force

texture

為什麼行星是球形的？加上9個更多的視頻。#aumum (Why are planets spherical? plus 9 more videos.. #aumsum)