So that's it! The "flow of time" in the hourglass is actually like this | Science Museum

"Time is money, but money can't buy time"

If there is something

Able to clearly see the passage of time

The timer must be on the list.

If we go further

Let people intuitively see the remaining time

Every drop in the hourglass will be cherished

One flower, one world; one tree, one bodhi

Today, Fat Science will take you to start from a scientific perspective

Talk about the "perspective of time" in the hourglass

How does an hourglass tell time?

The hourglass is an ancient timekeeping device.

Before the invention of the clock

Once widely used to measure time

The Western hourglass consists of two glass balls and a

Narrow connecting pipes

Through a glass ball filled with sand

Pass through the narrow pipe from above

Flow into the bottom glass ball

The time required to measure time

Once all the sand

All have flowed to the bottom of the glass ball

The hourglass can be turned upside down to measure time.

The earliest hourglass discovered in the West

Around 1100 AD

It appeared later than the hourglass in my country.

According to records, the hourglass in my country

First appeared in the Western Han Dynasty

It is also an ancient instrument for measuring time.

The manufacturing principle of the hourglass is roughly the same as that of the clepsydra.

It is like quicksand leaking from a container

Measure time to another container

my country also had timers such as sundials and clepsydras.

But since the sundial can only be used during the day and on sunny days

The clepsydra is also limited by weather and climate.

So the scope of use of hourglass will be wider

The most famous hourglass is

The " Five-wheel Hourglass " invented by Zhan Xiyuan in 1360

Five-wheeled hourglass worker's daily

Quicksand from funnel-shaped sand pool

Flowing into the sand bucket beside the first wheel

Driving primary wheel

This drives the mechanical gears at all levels to rotate

The last gear

Drives the middle wheel to rotate on the horizontal plane

There is a pointer on the axis of the middle wheel

The pointer is on a scaled

The instrument rotates on a disc

This shows the time

This hourglass is separated from the auxiliary astronomical instruments

It has become an independent mechanical clock structure.

No water pressure limitation

An hourglass is more accurate than a clepsydra

Can the falling speed of an hourglass be changed?

The hourglasses commonly seen in life are made of

Two closed glass cavities

Contains smooth glass beads

These microbeads are individually

They are all ordinary solids.

But gathered inside the hourglass

It is formed

A new group state that flows like liquid

This is called " granular flow " in chemical industry.

Such as flowing sand, snow, rice, etc.

All belong to granular flow

Even in daily life

Traffic flow, people flow, bulk materials

Transport, avalanches and debris flows

Also belongs to granular flow

The movement of a single particle

Newton's laws of motion can be used to accurately describe

Its state of motion at a certain time

When a group of particles come together

When exercising together

The description of its behavior becomes complicated.

Found in the study

Falling from the same vertical height

Particles of different sizes flow at different speeds

It is easy to form an arch structure at the exit and cause blockage

so

In the process of falling in the hourglass

Sometimes this happens

At this time, you can use external force to

Breaking the status quo

Affects the falling speed of the hourglass

besides

You can also use the pressure change

To change the speed of the hourglass falling

In 1993, Wu and Bideau et al.

In the study it was shown

The falling speed of the hourglass is not uniform.

Instead, the overall trend is fluctuating.

——Sometimes fast, sometimes slow

The study explains this phenomenon

When the sand falls

The volume of the upper glass cavity increases

The pressure decreases

The volume of the lower glass cavity is reduced

The pressure increases

It is this tiny pressure difference that slows down the hourglass's fall.

Then the upper and lower gases are reconnected

The pressure difference disappears and the hourglass falls faster

The whole process of the hourglass falling is

The pressure increases and decreases alternately.

If you want to change the falling speed of the hourglass

From the outside

Affects the upper and lower glass cavities of the hourglass

The pressure can be large or small

Other ways to time

In addition to the hourglass,

Clepsydra and sundials

It was also a common way of telling time in ancient times.

The clepsydra is a clepsydra with a small hole filled with water, and then another container with a scale-marked arrow is used to collect the water that leaks from the hole. The arrow is engraved with 96 grids, each grid is 15 minutes, and people can report the time according to the mark on the arrow that the water reaches.

Sundial : Also known as sundial, it is a device that uses the shadow cast by the sun to measure time. It is usually composed of a copper pointer and a stone disc. Among them, the copper pointer is called the "dial needle", which is perpendicular to the center of the disc, and the stone disc is called the "dial face", which is placed on a stone platform. The dial face is parallel to the celestial equator. The upper end of the sundial needle points to the north celestial pole, and the lower end points to the south celestial pole. There are 12 large grids carved on the front and back of the dial face, and each large grid represents two hours. When sunlight shines on the sundial, the shadow of the sundial needle will be projected onto the dial face. The sun moves from east to west, and the shadow of the sundial needle projected onto the dial face slowly moves from west to east. Therefore, the moving shadow of the sundial needle seems to be the pointer of a modern clock, and the dial face is the surface of the clock, which is used to display the time.

After reading the above introduction, are you

Conquered by wisdom

If you feel that just reading text is not enough

Then you must come to the China Science Museum's Light of China exhibition hall .

There are exhibits from different times and dimensions here

Wait for you to experience it yourself

Fat Science will see you at the Chinese Science and Technology Museum

Creative team: China Science and Technology Museum New Media Team

Review expert: Liu Yuhang, postdoctoral fellow at Beijing International Center for Mathematical Research

The pictures are from the Internet