Very Interesting – July-August 2019

If nothing can escape from a singularity,

how did the universe manage it?

Atandwa Sithole, Durban

E

instein’s theory of gravity

predicts that the universe

began in a singularity – a state of

zero size and thus infinite density

and gravitational force, which

would prevent it expanding. But

theorists believe that such a state

• also predicted to exist inside
  black holes – is the result of his
  celebrated theory ignoring quantum
  effects. These would prevent a truly
  point-like singularity from forming,
  eliminating the infinitely strong
  gravity, and thus allowing the
  universe to expand.

W

hen fish, shrimp or other aquatic

creatures swim together in a loose

cluster, this is typically called a shoal. It

can be a mix of different species. A

school is a group of the same fish

species swimming together in synchrony;

turning, twisting and forming sweeping,

glinting shapes in the water. Fish

probably do this to confuse predators

and to save energy (by using the

‘slipstreams’ of other fish). Pods are

herds of marine mammals including

whales, dolphins, walruses and seals.

What’s the difference

between a shoal, a

school and a pod?

Hannah Miles, Margate

How do ocean tides

create magnetic fields?

Tina Mgabadeli, Port Elizabeth

W

e’re taught in science lessons that it’s possible

to create electric current by moving electrical

conductors through magnetic fields. Known as

Faraday’s law of induction, it’s the basic idea behind

electricity generation in power stations. But shortly

after discovering the effect in 1831, Michael Faraday

wondered if it might lead to a natural source of

electricity. To find out, he tried to detect the current

produced by the electrically conducting river water

flowing through the Earth’s magnetic field under

London’s Waterloo Bridge. The experiment, conducted

in January 1832, was a failure, but Faraday remained

convinced the currents did exist – if only

extremely weakly.

Earlier this year, a trio of ESA satellites called Swarm

were able to detect electric currents generated in the

world’s oceans as they are dragged through the

Earth’s magnetic field by the gravitational pull of the

moon. These currents are then able to induce their

own feeble magnetic fields – around 20,000 times

weaker than the Earth’s magnetic field. Mapping the

oceans’ magnetic signature required state-of-the-art

equipment unimaginable in Faraday’s time. But as well

as vindicating the Victorian genius’s claim, the

research is expected to provide a whole new way to

monitor the movements of the oceans.

Q&A

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