Narrator:

The universe began its cosmic life in a Big Bang nearly fourteen billion years ago, and has been expanding ever since.

But what is it expanding into?

That’s a complicated question.

Here’s why:

Einstein’s equations of general relativity describe space and time as a kind of interconnected fabric for the universe.

This means that what we know of as space and time exist only as part of the universe and not beyond it.

Now, when everyday objects expand, they move out into more space.

But if there is no such thing as space to expand into, what does expanding even mean?

In 1929, Edwin Hubble’s astronomy observations gave us a definitive answer.

His survey of the night sky found all faraway galaxies recede, or move away, from the Earth.

Moreover, the further the galaxy, the faster it recedes.

How can we interpret this?

Consider a loaf of raisin bread rising in the oven.

The batter rises by the same amount in between each and every raisin.

If we think of raisins as a stand-in for galaxies, and batter as the space between them, we can imagine that the stretching or expansion of intergalactic space will make the galaxies recede from each other.

And for any galaxy, its faraway neighbors will recede a larger distance than the nearby ones in the same amount of time.

Sure enough, the equations of general relativity predict a cosmic tug-of-war between gravity and expansion.

It’s only in the dark void between galaxies where expansion wins out, and space stretches.

So there’s our answer.

The universe is expanding unto itself.

That said, cosmologists are pushing the limits of mathematical models to speculate on what, if anything, exists beyond our spacetime.

These aren’t wild guesses, but hypotheses that tackle kinks in the scientific theory of the Big Bang.

The Big Bang predicts matter to be distributed evenly across the universe, as a sparse gas — but then, how did galaxies and stars come to be?

The inflationary model describes a brief era of incredibly rapid expansion that relates quantum fluctuations in the energy of the early universe to the formation of clumps of gas that eventually led to galaxies.

If we accept this paradigm, it may also imply our universe represents one region in a greater cosmic reality that undergoes endless, eternal inflation.

We know nothing of this speculative inflating reality, save for the mathematical prediction that its endless expansion may be driven by an unstable quantum energy state.

In many local regions, however, the energy may settle by random chance into a stable state, stopping inflation and forming bubble universes.

Each bubble universe — ours being one of them — would be described by its own Big Bang and laws of physics.

Our universe would be part of a greater multiverse, in which the fantastic rate of eternal inflation makes it impossible for us to encounter a neighboring universe.

The Big Bang also predicts that in the early, hot universe, our fundamental forces may unify into one super-force.

Mathematical string theories suggest descriptions of this unification, in addition to a fundamental structure for subatomic quarks and electrons.

In these proposed models, vibrating strings are the building blocks of the universe.

Competing models for strings have now been consolidated into a unified description, and suggest these structures may interact with massive, higher-dimensional surfaces called branes.

Our universe may be contained within one such brane, floating in an unknown higher-dimensional place, playfully named “the bulk,” or hyperspace.

Other branes — containing other types of universes — may coexist in hyperspace, and neighboring branes may even share certain fundamental forces like gravity.

Both eternal inflation and branes describe a multiverse, but while universes in eternal inflation are isolated, brane universes could bump into each other.

An echo of such a collision may appear in the cosmic microwave background — a soup of radiation throughout our universe that’s a relic from an early Big Bang era.

So far, though, we’ve found no such cosmic echo.

Some suspect these differing multiverse hypotheses may eventually coalesce into a common description, or be replaced by something else.

As it stands now, they’re speculative explorations of mathematical models.

While these models are inspired and guided by many scientific experiments, there are very few objective experiments to directly test them, yet.

Until the next Edwin Hubble comes along, scientists will likely be left to argue about the elegance of their competing models…

and continue to dream about what, if anything, lies beyond our universe.

🧠 Vocabulário

⭐ Expressões e estruturas avançadas

Ever since

The universe has been expanding ever since.

Significa desde então.

I’ve lived here ever since.

= Eu moro aqui desde então.

What we know of as…

What we know of as space and time…

Estrutura usada para falar sobre algo que conhecemos ou chamamos de determinada maneira.

What we know of as reality may be very different.

= O que conhecemos como realidade pode ser muito diferente.

Stand-in for

Raisins as a stand-in for galaxies.

Significa servir como representação ou substituto de algo.

Sure enough

Sure enough, the equations predict…

Expressão usada quando algo acontece exatamente como esperado.

Pode ser entendida como:

“E, de fato…” / “Como esperado…”

If, anything

What, if anything, exists beyond our spacetime.

Essa estrutura é muito comum em inglês acadêmico.

If anything significa algo como “se é que existe alguma coisa”.

Save for

We know nothing of this speculative reality, save for…

Save for = exceto por / com exceção de.

É uma construção mais formal.

As it stands

As it stands now, they’re speculative explorations…

Significa:

“Como as coisas estão atualmente…”

É muito utilizada em discussões acadêmicas e profissionais.

Come along

Until the next Edwin Hubble comes along…

Aqui come along significa aparecer / surgir.

We need someone who can solve this problem when they come along.

❓ Questões de compreensão

1. What does the video mean when it says that the universe is “expanding unto itself”?

Explique a ideia com suas próprias palavras.

2. What did Edwin Hubble’s observations reveal?

A) Galaxies are getting closer to Earth.
B) All galaxies are stationary.
C) Distant galaxies are moving away from Earth.
D) The universe is getting smaller.

3. Why is the raisin bread used as an analogy?

4. What happens to galaxies that are farther away?

A) They recede more slowly.
B) They recede faster.
C) They stop moving.
D) They move toward us.

5. What is the “cosmic tug-of-war” described in the video?

6. What problem does the inflationary model attempt to address?

7. What is a “bubble universe”?

Explique o conceito em inglês.

8. According to string theory, what are the building blocks of the universe?

A) Galaxies
B) Atoms
C) Vibrating strings
D) Black holes

9. What are branes?

10. Why can’t scientists currently confirm these multiverse theories?

11. What does “as it stands now” mean?

A) According to historical evidence
B) As the situation currently exists
C) In the distant future
D) According to ancient theories

12. What question does the narrator leave us with at the end of the video?

✍️ Writing Practice

Imagine that you are explaining the concept of an expanding universe to someone who has never studied cosmology.

Write 8–10 sentences in English explaining:

• what the expansion of the universe means;
• why galaxies appear to move away from each other;
• what the raisin-bread analogy represents;
• one hypothesis about what may exist beyond our universe.

Try to naturally use at least 5 expressions from the lesson, such as:

ever since · stand-in for · sure enough · if anything · save for · as it stands · come along