the universe is a vast bubble of space
and time expanding in volume run the
clock backward and you get to a point
where everything was compacted into a
microscopic singularity of
incomprehensible density in a fraction
of a second it began expanding in volume
and it's still continuing to do so today
so how old is the universe how long has
it been expanding for how do we know for
a good long while astronomers assume the
earth and therefore the universe was
timeless that had always been here and
always would be but in the 18th century
geologists started to gather evidence
that maybe the earth hadn't been around
forever perhaps it was only millions or
billions of years old maybe the Sun - or
even the universe maybe there was a time
when there was nothing and then suddenly
pop universe it's the science of
thermodynamics that gave us our first
insight over vast lengths of time
everything moves towards entropy or
maximum disorder just like a hot coffee
cools down all temperatures want to
average out and if the universe was
Infinite in age everything should be the
same temperature
there should be no stars planets or us
the brilliant Belgian priest and
astronomer George Lumet proposed that
the universe must either be expanding or
contracting at some point he theorized
the universe would have been an
infinitesimal point he called it the
primeval atom and it was Edwin Hubble in
1929 who observed that distant galaxies
are moving away from us in all
directions confirming limitless theories
our universe is clearly expanding which
means that if you run the clock
backwards it was smaller in the distant
past and if you go back far enough
there's a moment in time when the
universe began which means it has an age
the next challenge figuring out the
universe's birth date in 1958 the
astronomer Allan Sandage used the
expansion rate of the universe otherwise
known as the Hubble constant to
calculate how long it had probably been
expanding he came up with a figure of
approximately 20 billion years a more
accurate estimation for the age of the
universe came with the discovery of the
cosmic microwave background radiation
the afterglow of the Big Bang that we
see in every direction we look
approximately 380,000 years after the
Big Bang our universe had cooled to the
point that protons and electrons could
come together to form hydrogen atoms at
this point it was a balmy 3000 Kelvin
using this and by observing the
background radiation and how far the
wavelengths of light have been stretched
out by the expansion astronomers were
able to calculate how long it has been
expanding for initial estimates put the
age of the universe between 13 and 14
billion years old but recent missions
like NASA's W map mission and the
European Planck Observatory have
fine-tuned that estimate with incredible
accuracy we now know the universe is
13.8 two-for-two
billion years plus or minus a few
million years we don't know where it
came from or what caused it to come into
being but we know exactly how old our
universe is and that's a good start
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challenge figuring out the universe then
was the next check okay