Why Is Gravity So Weak?

humanity is obsessed

with the superlative

the biggest the fastest the strongest

the most destructive

even after the world witnessed the

devastation wrought by atomic weaponry

during world war ii

we inexplicably built them bigger

bolder

and more deadly

on october the 30th 1961 a tupolov tu95v

bomber opens its doors and drops its 27

ton load over nevaya zamla island in the

soviet arctic ocean

the immense bomb descends almost

gracefully beneath parachutes allowing

its plane to speed away as fast as its

propellers will take it

which is just as well

for when this tsar bomba or king of

bombs detonates

it produces

the largest man-made blast

the world

has ever seen

the thermonuclear weapon explodes with a

force of 50 megatons of tnt more than 3

800 times stronger than the bomb dropped

on hiroshima

its mushroom cloud reaches 60 kilometers

in height and the flash of the

detonation could be seen a thousand

kilometers away

the heat from the explosion is enough to

cause third degree burns at the distance

of a hundred kilometers

the colossal destructive force of the

tsar bomber explosion was hard to fathom

but earlier that year astronomers had

witnessed an explosion that was some 10

billion billion times stronger

in a spiral galaxy 45 million light

years away from our own a giant star

reached the end of its life in

spectacular fashion

as fusion came to a halt in its core the

repulsion of its electrons could no

longer resist the crushing force of

gravity and it collapsed in on itself at

nearly a quarter of the speed of light

the sudden implosion sends temperatures

soaring and results in a supernova

explosion that spews stellar material

over many light years

but if supernova explosions are more

powerful than anything we can conceive

of on earth

hypernovas put even them to shame

these rare super powerful stellar

explosions result from the death of

stars more than 30 times more massive

than our sun a black hole is created in

the center and scorching winds of newly

forged nickel and jets of radiation

plough through and ignite what was left

of the star

hypernovae can be 10 to 100 times

brighter and more powerful than a

supernova

they are believed to be the most

powerful single event in our observable

universe

and all of this destructive force

results

ultimately from the pull of gravity on

the atoms that make up these dying stars

so you could be forgiven for thinking of

gravity as vastly powerful

indeed every moment of our lives is

shaped and defined by gravity

from the convenience of remaining stuck

to the surface of the earth to the

mental calculations we make when playing

sports even to the immense challenge of

engineering rockets to escape our

planet's inexorable pull

but gravity is just one of four

fundamental forces that control our

universe

the strong nuclear force holds our atoms

together the electromagnetic force

permeates all of space and delivers the

radiation which lights and warms the

cosmos even the weak nuclear force has a

vital purpose driving the nuclear fusion

in the hearts of stars

indeed when compared to these other

heavy hitters the force of gravity pales

in comparison

the strong force is fittingly the

strongest force known to nature followed

by the electromagnetic force and then

unsurprisingly the weak force

and at the bottom of the scale

gravity

by some distance

it is weaker even than the so-called

weak force

to be exact

by 10 to the 25th power or 10 trillion

trillion times

in order for us to feel the effects of

gravity we must work on cosmological

scales with entire stars and planets

worth of accumulated matter

in simple terms the stored chemical

energy in the legs of an ant can

overcome the gravity of an entire world

[Music]

gravity's relative weakness has baffled

scientists for years and has come to be

known as the hierarchy problem

and this mystery may be linked to

another cosmological puzzle

where does this omnipresent but

practically powerless force

originate

to answer these century-old questions we

will have to take a trip billions of

years back in time

billions of light years away in space

and possibly even

to another dimension

[Music]

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[Music]

gravity was the first force to be

recognized by scientists and yet to this

day

remains the most shrouded in mystery

isaac newton may have been a brilliant

mathematician but he was by all the

counts a dower and serious man with no

time or interest for the opposite sex or

indeed any sex at all he remained a

virgin all his life and what joy he

experienced was scarcely visible on his

face

legend has it he only laughed in public

twice

but of course it was under this ultimate

focus distracted by neither jolity or

intimacy that newton was able to

formulate his famous theory of universal

gravitation

[Music]

in 1666 the deadly outbreak of plague

forced cambridge university to close and

newton returned to his family home

wolves thought manor in lincolnshire

here in an isolation much like that

experienced by many of us in the last

two years newton found himself uniquely

inspired

he continued to experiment with light

and optics and took long walks around

the grounds where it is said he

witnessed something that would come to

define physics

whether or not this is myth it was a

myth perpetuated by newton himself

after dinner the weather being warm we

went into the garden and drank tea under