INSTRUCTIONS TO WORK ON THE VIDEO :

Black holes are among the most destructive objects in the universe. Anything that gets too close to the central singularity of a black hole, be it an asteroid, planet, or star, risks being torn apart by its extreme gravitational field. And if the approaching object happens to cross the black hole’s event horizon, it’ll disappear and never re-emerge, adding to the black hole’s mass and expanding its radius in the process. There is nothing we could throw at a black hole that would do the least bit of damage to it. Even another black hole won’t destroy it– the two will simply merge into a larger black hole, releasing a bit of energy as gravitational waves in the process. By some accounts, it’s possible that the universe may eventually consist entirely of black holes in a very distant future. And yet, there may be a way to destroy, or “evaporate,” these objects after all. If the theory is true, all we need to do is to wait. 

In 1974, Stephen Hawking theorized a process that could lead a black hole to gradually lose mass. Hawking radiation, as it came to be known, is based on a well-established phenomenon called quantum fluctuations of the vacuum. According to quantum mechanics, a given point in spacetime fluctuates between multiple possible energy states. These fluctuations are driven by the continuous creation and destruction of virtual particle pairs, which consist of a particle and its oppositely charged antiparticle. 

Normally, the two collide and annihilate each other shortly after appearing, preserving the total energy. But what happens when they appear just at the edge of a black hole’s event horizon? If they’re positioned just right, one of the particles could escape the black hole’s pull while its counterpart falls in. It would then annihilate another oppositely charged particle within the event horizon of the black hole, reducing the black hole’s mass. Meanwhile, to an outside observer, it would look like the black hole had emitted the escaped particle. 

Thus, unless a black hole continues to absorb additional matter and energy, it’ll evaporate particle by particle, at an excruciatingly slow rate. How slow? A branch of physics, called black hole thermodynamics, gives us an answer. 

When everyday objects or celestial bodies release energy to their environment, we perceive that as heat, and can use their energy emission to measure their temperature. Black hole thermodynamics suggests that we can similarly define the “temperature” of a black hole. It theorizes that the more massive the black hole, the lower its temperature. The universe’s largest black holes would give off temperatures of the order of 10 to the -17th power Kelvin, very close to absolute zero. Meanwhile, one with the mass of the asteroid Vesta would have a temperature close to 200 degrees Celsius, thus releasing a lot of energy in the form of Hawking Radiation to the cold outside environment. The smaller the black hole, the hotter it seems to be burning– and the sooner it’ll burn out completely. 

Just how soon? Well, don’t hold your breath. First of all, most black holes accrete, or absorb matter and energy, more quickly than they emit Hawking radiation. But even if a black hole with the mass of our Sun stopped accreting, it would take 10 to the 67th power years– many many magnitudes longer than the current age of the Universe— to fully evaporate. When a black hole reaches about 230 metric tons, it’ll have only one more second to live. In that final second, its event horizon becomes increasingly tiny, until finally releasing all of its energy back into the universe. And while Hawking radiation has never been directly observed, some scientists believe that certain gamma ray flashes detected in the sky are actually traces of the last moments of small, primordial black holes formed at the dawn of time. 

Eventually, in an almost inconceivably distant future, the universe may be left as a cold and dark place. But if Stephen Hawking was right, before that happens, the normally terrifying and otherwise impervious black holes will end their existence in a final blaze of glory.

According to the video, are these statements true or false?

1. An object that enters a black hole will appear many years after.
2. It is certain that a black hole can be destroyed.
3. It is believed that in the future the universe can be made exclusively of black holes.
4. Stephen Hawking has a theory on how to destroy a black hole.
5. Smaller black holes have colder temperatures.
6. Black holes gain matter faster than they lose it.
7. The destruction of all existing black holes can also mean the destruction of the universe.

1. F
2. F
3. T
4. T
5. F
6. T
7. T

Take a look at the following sentences from the text:

There is nothing we could throw at a black hole that would do the least bit of damage to it. 

Black hole thermodynamics suggests that we can similarly define the “temperature” of a black hole.

Can you tell what is the difference between can and could?

Answer: Both can and could are modal verbs.

English students sometimes find these modals hard to distinguish. In general could is considered more polite (or formal) than can. Furthermore, we use could to show that something is possible, but not certain and can to make general statements about what is possible.

Exercise:

Complete the sentences using can or could.

1. Sophia _______ ride a bicycle. She rides it to school every day.
2. When  _______ I talk to you about the company report?
3. Most dinosaurs walked on land, but some  _______ fly or even swim.
4. I  _______ drive a truck when I was only eighteen years old.
5. David hit the tree because he  _______ stop his car. The brakes weren't working.

1. Can
2. Can
3. Could
4. Could
5. Couldn’t

Traduire les phrases suivantes en anglais, issues du texte, puis retrouver ces phrases dans les deux premiers paragraphes du texte en anglais:

1. Il n'y a rien que nous pourrions lancer sur un trou noir qui lui ferait le moindre degat.

2. Ces fluctuations sont generées par la destruction et la creation continue de pairs de paticules virtuelles, composé d'une particule et de son antiparticule d'une charge oposée.

Essential Grammar in use p 163-164

unit 78 somebody/anything/nowhere etc.

Put in somebody (or someone) / something /  somewhere

1. She said .............                                What did she said ?
2. I've lost ..........                                     What have you lost ?
3. They went ........                                   Where did they go ?
4. I'm going to phone .....                           Who are you going to phone ?

1. something
2. something
3. somewhere
4. someone/somebody

(please note that this definitions are according to the context)

Torn apart (phrasal verb, past participle of tear apart) - to completely destroy.

Well-established (adjective) - recognized, generally known about.

Thus (adverb) - in this way.

10 to the -17th power - that is -1 followed by 17 zeros.

Hold your breath (expression, to hold one’s breath) - to wait for something to happen, often feeling anxious; be in a state of suspense or anticipation.

Accrete (verb) - come or bring together under the influence of gravitation.

Traces (noun, plural of trace) - a mark, object, or other indication of the existence or passing of something.

Dawn of time (expression) - the first time period.

Impervious (adjective) - not able to be influenced, hurt, or damaged.

Blaze of glory (expression) - In an extraordinary and impressive manner; used to describe a final action.

Peseshet is a doctor and a teacher. The video describes a typical day of her life.

Now it is you turn. Write a text :

- Present yourself.

- Describe your profession.

- Tell what you did to get this job.

- Describe a typical day of your life : what usually happens when you are at work?

You can book a one to one class with a teacher who will correct your writing exercise.  One to one classes can be online, with a video call, anytime of the day. 

This gives you full flexibility for your timetable.

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