The universe: origins and structure

Warmer: space quiz

Work through the questions with a partner. Feel free to add any extra information if you have some.

How old is the universe?

a) about 4.6 billion years

b) about 13.8 billion years

c) about 100 billion years

How long does light from the Sun take to reach Earth?

a) about 8 seconds

b) about 8 hours

c) about 8 minutes

What is the most common element in the universe?

a) hydrogen

b) oxygen

c) carbon

Which is the hottest planet in the Solar System?

a) Mercury

b) Venus

c) Mars

Which star is closest to the Sun?

a) Sirius

b) Polaris

c) Proxima Centauri

What is the nearest galaxy to the Milky Way?

a) Andromeda

b) Triangulum

c) Whirlpool

Which planet has the most known moons?

a) Jupiter

b) Saturn

c) Neptune

Roughly how fast does light travel?

a) 300,000 km per second

b) 300,000 km per hour

c) 30,000 km per second

Explain it to me like I'm 5

Sometimes we feel like we understand a concept fairly well. Then we try explaining it and notice the curious look on our interlocutor's face and we start to doubt ourselves. A good strategy when it comes to explainining complex subjects is to 'explain it like you would to a 5-year-old child.'

Look at the following things. Pick one and explain it to your partner like they're 5. Then alternate.

• a planet

• a moon

• a star

• a solar system

• a galaxy

• lightspeed

• gravity

• dark matter

• dark energy

• Einstein's theory of special relativity

I'm just kidding on the last three, but feel free to be ambitious!

Get ready for a challenging reading task.

Your goal is to try to follow the main idea and to accept that there will be many tricky / unknown terms and concepts here.

A brief history of everything

About 13.8 billion years ago, everything that exists today was packed into a state far hotter and denser than anything we can reproduce on Earth. Every atom in every star, planet and person was there. From that moment the universe began to expand and cool, and it has been doing so ever since. Scientists call this beginning the Big Bang.

In the first few minutes, the universe was a primordial mix of particles and energy. As it cooled, protons and neutrons began to fuse into the nuclei of the lightest elements: mostly hydrogen and helium, with tiny traces of lithium. By mass, about three quarters of ordinary matter became hydrogen and about a quarter became helium. Those proportions have barely changed since, and astronomers can still measure them today.

For the next 380,000 years, the universe was so hot that electrons could not stay attached to nuclei, and light could not travel far before it bounced off a free particle. When the temperature dropped to around 3,000 kelvin (roughly 2,700°C), electrons and nuclei combined to form the first neutral atoms, and light could finally travel freely. That ancient light is still reaching us. After billions of years of expansion it has been stretched into microwaves, and it arrives as a faint afterglow known as the cosmic microwave background.

What followed is known as the cosmic dark ages. There were no stars yet, only huge clouds of hydrogen and helium spread fairly evenly through space. The spread was not perfectly even, though. Some regions were slightly denser than others, and gravity gradually pulled more material into them. Dark matter, an invisible substance that neither gives off nor absorbs light, played a key role. It began to clump together first, forming a kind of scaffolding that ordinary gas could gather around.

Somewhere between 100 and 200 million years after the Big Bang, gas inside these clumps became dense and hot enough to ignite nuclear fusion, and the first stars were born. They were probably enormous, many times more massive than the Sun, and they used up their fuel in just a few million years. Many of them ended their lives as supernovae. In their cores and in these explosions, they forged heavier elements such as carbon, oxygen and iron, and scattered them into space.

Stars gathered into the first galaxies, which grew by pulling in gas and merging with their neighbours. The James Webb Space Telescope, launched in 2021, has observed galaxies that existed less than 300 million years after the Big Bang. Some of them are brighter and more developed than most astronomers expected. Over billions of years, small galaxies combined into larger ones. Our own galaxy, the Milky Way, contains stars more than 12 billion years old. Each generation of stars that lived and died added more heavy elements to the gas around them, so later stars formed from richer material.

About 4.6 billion years ago, in one of the Milky Way’s spiral arms, a cloud of gas and dust collapsed under its own gravity. The collapse may have been triggered by the shock wave from a nearby supernova. Most of the material fell inwards and became the Sun. The rest flattened into a spinning disc. Inside this disc, grains of dust collided and stuck together, forming pebbles, then rocks, then bodies several kilometres across. Through a process called accretion, these bodies gradually coalesced into planets.

Earth formed around 4.5 billion years ago. Early in its history it was largely molten, and it was constantly struck by debris left over from the formation of the Solar System. According to the leading theory, a body roughly the size of Mars crashed into the young Earth, and the material thrown out by the impact came together to form the Moon. Over time the surface cooled, a solid crust formed, and water collected in the first oceans.

Almost every atom of iron in your blood and calcium in your bones was made inside stars that died long before the Sun existed. The hydrogen in the water you drink is even older. It dates back to those first few minutes.

Explain it to me like I'm 5

Work in small groups and try to explain the meaning of the following:

• a primordial mix of particles and energy

• protons, neutrons and electrons (and nucleus)

• the cosmic microwave background

• to clump together

• to ignite nuclear fusion

• one of the Milky Way's spiral arms

• a supernova

• a process called accretion

• a solid crust formed

discussion

How challenging did you find the text?

What was the biggest obstacle?

a) difficult lexical items (words and phrases)

b) unfamiliarity with the theme

When contemplating the size and age of the universe, some people report having deep and profound feelings. Others report feeling fear. Others still report feeling nothing in particular. How do you feel when thinking about such things?

How often do you find yourself wondering about the scale of the universe?

Some people, in particular (but not only) deeply religious people, are incredibly suspicious about this explanation of our origins. Even if you're not particularly religious, can you understand why?

Do we have a volunteer brave enough to explain to the class, as if we are all 5, what on Earth the big bang is / was?

Let's turn to Kurzgesagt, one of my favourite edutainment channels, for an explanation of the Big Bang.

Again, just watch and try to follow the main thread.

Discussion

The whole point of this channel is to explain important, interesting but complex things in a simple way by using analogies, easy-to-understand language and simple animations to get the idea across. Did they fail here?

"The Big Bang was not an explosion." A big surprise or something fairly obvious?

"The universe didn't expand into anything. Space was just expanding into itself." Is that even possible to get your head around?

Quarks and gluons. Did you get lost at all here?

The strong nuclear force, electromagnetic force, the weak nucelar force and gravity. Did you study this at school?

What happened before the big bang? 😊

vocabulary

All forms of science require proof, and there is a lot of potentially confusing language here. Let's take a look at some lexical items. Match 1-2 with the definitions (A-L)

1. theory

2. hypothesis

3. evidence

4. peer-reviewed

5. the scientific method

6. observation

7. prediction

8. data

9. consensus

10. confirm

11. challenge

12. findings

a) to show that something is definitely true

b) general agreement among most experts

c) facts, numbers or measurements collected for analysis

d) a proposed explanation that has not yet been properly tested

e) checked by other experts in the same field before publication

f) the results or conclusions of a study

g) a well-tested explanation supported by a large body of evidence

h) a statement about what will happen, based on a theory or data

i) the process of watching or studying something carefully

j) to question whether something is true or correct

k) information that shows whether something is true

l) a process of observing, forming hypotheses and testing them through experiments

Complete the sentences with the words and phrases in the box. Use each one once.

consensus · challenged · hypothesis · the scientific method · observation · evidence · confirmed · prediction · theory · peer-reviewed · findings · data

1. Before the experiment, the team stated their ______: that plants grow faster when music is played to them.

2. Evolution by natural selection is a ______ supported by more than 150 years of evidence.

3. Without any ______, the court could not find him guilty.

4. The study was published in a ______ journal, so other experts had checked it before publication.

5. There is now a broad ______ among doctors that smoking causes cancer.

6. The weather service’s ______ of heavy snow turned out to be completely wrong.

7. The researchers collected ______ from 5,000 patients over ten years.

8. A new study has ______ the idea that coffee is bad for your heart.

9. Further tests ______ that the drug was safe for children.

10. The ______ of the survey surprised everyone: most people said they were happy at work.

11. Careful ______ of the patient over several nights showed that she stopped breathing in her sleep.

12. Galileo is often described as one of the first people to use ______, testing ideas through experiments rather than relying on authority.

Reflection

Typically, modules start light and get progressively difficult. You've been hit with a hammer today. How does it feel?

In the module, we're going to come across a variety of interesting but unfamiliar things, such as lunar exploration, the search for extraterrestrial life, black holes and much more. How much of an interest do you have in topics like these?

Both for your linguistic skills and for the purpose of understanding the topic better, I would highly recommend that you all watch a follow-up video after each class. Do you agree that this is a good idea? How realistic is it?

Alternatively, you can show the lesson to your favourite AI buddy and ask them to test you on your understanding. Is this feasible?