All About Space - UK (2020-02)

IfI goclosetoa blackhole,time

slowsdownforme.Infact,itwill

slowdowncompletelyifI get

totheeventhorizon– whichis

essentiallythesurfaceofa black

hole.Thismeans,forinstance,

ifweputinenoughmoneyto

builda spacecraftandgothere,

andthenwaita fewmonthsina

closeproximityoftheblackhole,

andthenI turnmyengineonand

I comeout,whenI comeout,I

amverymuchinthefuturewith

respecttowhenI wentin.

I couldstaythereforten

minutesforme,andwhenI

comeout,maybe3,000years

havepassed.Ablackholeisa

time-slower.It’ssomethingthat

whenyougothereandyoujump

tothefuture,timeforyougoes

extremelyslower,whileoutside

itcontinuesfaster.Weknowthat

itisoneofthephysicaleffects

thatallowedustocomputewhat

happensintheproximityofa

blackholeandpredicttheimage

oftheblackholethatwasseen

in2019.

CarloRovelliisatheoretical

physicistattheCentrede

PhysiqueThéorique

deLuminyofAix-

MarseilleUniversity

Howdoestime

actaround

blackholes?

ASTROPHYSICS

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abouttheSolarSystemandbeyond.I think

there’s a sense in which we feel detached from

nature, and that would be a mistake. Science is

an attempt to understand nature, of which we’re

a part, and that’s vital for our survival. There

is a legitimate question we could ask: how do

planetary atmospheres evolve? What we’ve found

is that planetary atmospheres are rather fragile

things in a sense, and they can evolve in response

to quite small changes, and we’ve seen that not

only by measuring the Earth’s atmosphere and

modelling it, but also trying to model Venus’

atmosphere. In particular where we also deploy

our climate models, and also Mars’ atmosphere

and how it lost its atmosphere, which is also a

target for our climate models. Investigating the

Solar System allows us to test our understanding

ehave

differentlaboratories,sothat’snumberone.

But number two, the threat of an asteroid

strike, for example, is very real. It does happen.

Carl Sagan – this is one of my favourite quotes,

I always quote it – he said, “If the dinosaurs had

a space programme, they’d still be around.” But

he was making a serious point that we do live

in a challenging environment, and the more we

understand about it, and the more we develop our

technologies, it may allow us to mitigate some

of these threats. This makes it more likely we

are able to survive. I think that’s also important.

That’s not science fiction, it’s a real issue.

Brian Cox OBE is a professor of particle

physics in the School of Physics

and Astronomy at the University of

Manchester, UK

UlUltiimatelelyy,we llm wewawa fifi t Ea. TT ’’stheh point, becausew

Does the greater threat to

Earth come with climate

change or from space?

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