[Music]
thanks to Squarespace for sponsoring
today's video how would the universe
change if you approached the speed of
light what would everything around you
look like how would space and time act
the answer is a lot different from what
you are currently used to to travel the
speed of light isn't actually possible
for anything other than massless
particles like photons it would require
infinite energy to get something with
mass to that speed the energy required
exponentially goes up the closer you get
but there are instances of matter coming
close we've observed some particles
traveling 99% of the speed of light now
for you and me
we have no hope of ever approaching
these speeds but if you did manage it
what happens the space and time from
your perspective would be very
noticeable let's ease you into this as
is going to be a bit tricky to wrap your
head around we will simulate going from
standing to traveling almost the speed
of light this is a fun little game
called
a slower speed of light released by MIT
demonstrating what would happen if the
speed of light got progressively slower
eventually to walking speed at first my
character looks around and sees the
world normally but as I start to pick up
these orbs instead of speeding me up the
game slows the speed of light down to
simulate what it would look like if we
were traveling extremely fast over vast
distances as the speed of light slows
what becomes apparent to you
the first thing I notice is that the
colors start to change this is because
of something called the relativistic
Doppler effect you see when you look
around and you see color on objects this
is because light is reaching your eyes
at specific wavelengths the longest
wavelengths you can see are Reds the
shortest wavelengths are violets beyond
the range of our sight our the infrared
and ultraviolet but when you are going
very fast because of the Doppler effect
some of the wavelengths that were in the
infrared and ultraviolet now shift to
wavelengths you can detect suddenly
things that were invisible to us before
become visible like heat in infrared and
fluorescent substances in ultraviolet
the faster you travel the larger your
visible range now becomes light does
travel in waves but it is also a stream
of particles called photons as you head
into the flow of particles at speed the
more particles will hit your eye making
everything ahead of you brighter on the
other hand if you look behind you as you
travel forwards everything will get
darker because less photons are reaching
you this is known as the searchlight
effect
what else do you start to notice you may
notice that we seem to be gradually
speeding up but actually our speed
always stays the same throughout the
game we are just walking like we were at
the beginning this is the result of
special relativity namely time dilation
one of the laws of the universe is that
the speed of light is a constant
however space and time are not and can
be warped so when you are moving two
things change your time and your
distances relative to stationary
observers let me explain time goes
slower for an object that goes faster
this has been proven if you have two
clocks one stationary and the other in
rapid motion say on a rocket the times
on each will go out of sync this is why
the times on satellites in orbit around
Earth need to be occasionally adjusted
or they'd go out of sync with
earth-based clocks not by much
a few milliseconds per year but they
would add up eventually the faster you
go the more time dilation happens until
should you hit the speed of light the
rate of time reaches zero this means
photons or light particles traveling the
speed of light are unaffected by the
passage of time but let's go back to how
time dilation affects us in the game
removing the lighting effects will help
us see this a lot more clearly now
remember throughout the game our walking
speed stays the same it's the speed of
light that slows down as we collect more
orbs and yet it seems that we move a lot
faster towards the end of the game than
at the beginning what is happening here
is that our time is going slower than
everything around us as a result it's
like the distances of space are shorter
meaning we get somewhere quicker from
our perspective in practice this means
that if we travel in a vehicle that
approaches the speed of light we travel
for one year at that speed it all seems
normal for
but ten years have passed two people on
earth should you actually be able to
travel the speed of light you could get
anywhere in the universe instantaneously
from your perspective but on earth
however far in lightyears your journey
takes you will equal the equivalent
amount of years from their perspective
so do you want to go 40 light-years away
and can travel the speed of light you
get there instantaneously from your
perspective but for people on earth you
show up there 40 years later again
though in practice light speed travel is
impossible for anything made of matter
the last effect is a weird one it's like
our field of view changes this is from
the effects of the aberration of light
and the Lorentz transformation light
takes time to reach our eyes and when we
see anything we are seeing that object
in the past even now you are watching
this video with a tiny tiny tiny time
delay as light takes time to leave your
screen and reach your eyes as we move in
the game that object we are seeing isn't
where we think it is anymore you may
have thought as you've been watching
this video that I must be useless at
computer games because I keep crashing
into walls and missing orbs but this
effect means that I'm not standing where
I think I am because the more orbs I
have the slower light is traveling so I
actually need to start turning a little
ahead of what I'm used to which is
difficult to comprehend while navigating
it's like playing with lag this effect
also means that I can see much more of
my surroundings in one go
this animation helps show why the light
source is moving relative to me as I
move forward but because the beam of
light takes time to reach me I see where
it was relative to me in the past
when there is a lot to see around me
it's as if my field of view increases
the faster I travel as I'm suddenly
seeing all these objects as they were
relative to me in the past light space
and time get more complicated still but
I won't delve into it in this episode
all I can say is that I'm glad light
appears almost instantaneous for us this
game was a bit of a thought experiment
to see what the world would be like if
light was slow but it hasn't even gone
into the other really problematic
scenarios like earth traveling around
the Sun at the speed it does how all our
electronics would be affected and other
major issues in the opposite vein as
being able to approach the speed of
light would be beneficial for travelling
large distances in short times however
time is passing normally for people on
earth meaning travelling anywhere in the
universe and coming back again could be
possible for you but earth would look a
lot different on your return with years
decades millennia or more having passed
depending on how far you went on your
journey due to the various effects
outside your ship everything would look
warped your field of view would be
greater a greater range of light
wavelengths become visible and in front
of you would be much much brighter so
there we have it how your universe would
change if you approach the speed of
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