the life of the universe is
characterized by the presence of many
extraordinary events
some of them involving huge amounts of
energy but have you ever wondered what
is the most powerful type of event in
the universe and did you know that it is
something so powerful that could
potentially even cause
life extinction on earth curious to know
what it is
stick with me and i'll tell you in a few
[Applause]
moments
in the universe extremely powerful
events happen all the time
think for example to a supernova a
supernova
is an immense explosion that occurs when
a massive star runs out of fuel the star
collapses on itself producing a huge
explosion
these events are so energetic that a
supernova occurring in our galaxy
would be visible during daylight in our
sky
the amount of energy produced by a
supernova in a few seconds
is more than the energy emitted by the
sun during its whole lifetime
that's impressive however supernovas are
not even the most powerful events in the
universe
in this special ranking the honor
belongs to another type of event called
a gamma ray burst or grb for our friends
but what are they grb are brief bursts
of gamma rays
gamma rays are the most energetic form
of electromagnetic radiation
what does it mean there are different
types of electromagnetic waves
in fact they are classified into seven
categories depending on their frequency
radio waves microwaves infrared
visible light ultraviolet x-rays and
gamma rays
you should be familiar with some of them
microwaves for example are used to cook
food
radio waves are used for
telecommunications while
x-rays are used for medical imaging
these
seven types of radiation are ranked from
lowest to highest frequency
lower frequency means lower energy while
higher frequency means higher energy
this also means that radio waves are the
electromagnetic waves with
the lowest energy while gamma rays are
the most energetic ones
in fact gamma rays are very dangerous to
humans
they are for instance emitted by some
radioactive source
and they can penetrate through the human
body causing damage to tissue and organs
they can even cause dna mutations with
long-term effects
such as increasing the risk of cancer so
gamma-ray bursts
are intense short-lived bursts of
extremely energetic gamma rays
but how are they produced it depends
in fact they are classified into two
types depending on their duration
short grbs and long grbs short gamma ray
bursts have a duration of less than two
seconds
and they can even last a few
milliseconds only although scientists
are not exactly sure about their origin
they think that short gamma-ray bursts
are produced during events known as
neutron star merger
in which two neutron stars collide
producing a more massive one or a black
hole
when these huge cosmic collisions occur
a lot of energy
in the form of gamma rays is released
producing a gamma-ray burst
it is believed that short gamma-ray
bursts are also produced when a neutron
star
merges with a black hole on the other
hand long gamma ray bursts are those
lasting more than 2 seconds
some can even last a few minutes these
represent the majority of grb events
and they are usually produced during a
supernova explosion
in the collapse of a star a lot of
energy is released producing a grb
but how were they first discovered well
this is interesting
in fact they were discovered by accident
during the 1960s during the cold war
the united states sent a group of
satellites the vila satellites into
space
these satellites were equipped with
gamma ray detectors
and their main purpose was to detect
possible nuclear explosions
on earth or in space which would have
been a sign
of military activity on behalf of the
soviet union
however on july 2nd 1967
two of these satellites detected a
sudden flash of gamma radiation
whose nature was very different from the
signal emitted by known
nuclear weapons in the following years
dozens of other similar signals were
detected
by analyzing all the data from the
satellites it became clear
that the origin of these gamma-ray
flashes was in space
not on earth in fact these were the very
first detections of gamma ray bursts
in 1973 all these findings were
published in an article of the
astrophysical journal
and the astronomical community finally
started to acknowledge the existence of
these events
how does a gamma-ray burst look like
although we never took a clear picture
of one of them
in fact all the grbs we observed so far
were too distant from us
scientists believe that most of the
energy produced by a gamma-ray burst
is concentrated in two narrow cones
on the opposite sides of the source so
contrary to most types of events in the
universe
here the energy is not emitted in all
directions instead it is focused
into one precise direction we can think
therefore
a grb as a narrow beam of gamma rays
extremely energetic radiation but how
powerful
are gamma-ray bursts before finding out
the answer to this question
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so we have seen how gamma-ray bursts
were discovered and how they are
produced
but how energetic are they well before
answering this question we need to
clarify the difference between
energy and power first energy is a
concept we are very familiar with for
instance if you need to boil the water
in a pot
you turn on the stove and the heat will
provide a certain amount of energy to
the water
the longer you leave it on the more the
energy transferred to the water
energy is measured in joules so we can
say for example that if you leave the
stove on for
one second one thousand joules of energy
will be transferred to the water
power instead is the rate at which
energy is transferred
so it also takes into account how much
time is required for that transfer of
energy to occur
in the previous example a more powerful
stove may be able to transfer
2 000 joules of energy in one second
instead of 1000 joules only
in that case we say that the power of
this new stove is twice that of the
first
stove power is measured in watts where
one watt means one joule of energy
transferred each second
so in our example the first stove is a
power output of a thousand watts
while the second stove has a power
output of 2000 watts
now that we have clarified this
difference we can talk about the energy
and the power of a gamma-ray burst the
amount of energy released by grbs is
impressive
a typical gamma ray burst can emit
around 10 to the power of 44 joules of
energy
this number is huge it is one followed
by 44 zeros
there's no event occurring on earth
whose energy can be compared to this
value
for instance the most powerful nuclear
bomb ever tested on the earth released
only 10 to the power of 17
joules of energy one followed by 17
zeros
in fact the amount of energy emitted by
a gamma ray burst
is comparable to the energy emitted by
the sun during its whole life
however what is even more impressive is
the fact that while the sun releases all
this energy
over 10 billion years a gamma ray burst
can release it in less than a second
that's why grbs are said to be the most
powerful events in the universe
it's because their duration is extremely
short although other phenomenon in the
universe are able to release a similar
amount of energy
none of them can do it in such a short
time like a gamma-ray burst
to give you an idea of how powerful
gamma-ray bursts are
think about this fact the farthest
object in the universe we have ever been
able to observe with the naked eye is
indeed a grb
i'm talking about grb 0a
yes not really an easy name to remember
this gamma-ray burst was observed for
the first time by a nasa satellite on
march 19
2008 it was so powerful that it emitted
not only gamma radiation
but also a lot of visible light in fact
it remained visible
in the sky for about 30 seconds although
as a very faint object given its extreme
distance
what is really astonishing here is that
this event was visible
despite the fact its distance from the
earth was about 7.5 billion light years
this was in fact the farthest object
ever visible to the human eye
to give you an idea of what we are
talking about if this gamma-ray burst
occurred at the same distance as the sun
it would have been a thousand trillion
times brighter than our star
now that we have understood how powerful
these events are
we may ask ourselves the following
question are gamma-ray bursts dangerous
for the earth the answer is yes and no
yes they are potentially very dangerous
in fact if the earth was along the
direction of the cone of energy
of a hypothetical future gamma-ray burst
we would be in serious trouble
gamma rays in fact are extremely
dangerous for the atmosphere
since they can trigger several chemical
reactions that would lead to a dramatic
reduction of the ozone level
as a consequence a larger amount of
ultraviolet radiation from the sun
would reach the earth's surface causing
devastating effects both on the climate
but also on living organisms such as a
potential increase of cancer risk
although it is hard to make accurate
predictions such an event could
potentially lead to a mass extinction
in fact there are a few evidences
suggesting that one of the earth
extinction events in the past occurred
450 million years ago
could have been triggered by a gamma-ray
burst however
you want to wait a minute before
freaking out the chances of this to
happen
are not so high in fact there are two
points to consider here
first gamma-ray bursts occur not that
frequently
in fact these events are quite rare it
is believed that in a galaxy
only a few grbs occur over a million
years
to give you an idea no gamma-ray bursts
have been observed
so far in our galaxy at least since we
are able to detect them
second even if a gamma-ray burst occurs
in our galaxy
we have to keep in mind that most of its
energy is concentrated in a narrow cone
therefore earth would be affected only
if it was along the direction of this
beam of energy of the grb
however since this beam is very narrow
the probability of this to happen is
very low
no panic the chances that we will be hit
by a gamma-ray burst in the near future
are quite low so in conclusion gamma-ray
bursts are very fascinating events
nothing else in the universe can produce
such large amounts of energy in such
short times somehow gamma-ray bursts are
a reminder to us
of the immense power that some objects
in the universe have
and some of the incredible amounts of
energy that are produced in certain
monster collisions between cosmic
objects
and we are the lucky spectators of these
wonderful shows
that's all for this video thanks for
watching everyone
did you find gamma-ray bursts exciting
are you amazed by the immense power of
these events
are you afraid about the possibility of
one of them hitting the earth
is there anything more you want to hear
about grbs let me know in the comments
below be sure to subscribe
and i'll see you next time on the
channel