We're all familiar with the sound of
a car passing by. This distinctive drop in Pitch is known as the Doppler effect If light moved slow enough, we would also see the
car change color as it passed us by. The reality is, light moves far too fast for us to notice anything like this But take a look at this image of Galaxy GS z13 it should look something like this, but its
color has been changed all the way to Red. In fact, the light from this galaxy has been changed so
much, that it isn't even visible to the human eye. This is the Doppler effect in action
or for light, it's known as redshift. In this video we're going to look at this
newly discovered Galaxy and how we are able to see almost right
back to the start of our Universe. We'll also be giving away this awesome space shuttle Lego set, so stick around to the end of the video to see how you could win. Although it may not look like much, this tiny red blob is the most distant thing anyone has ever seen. With this picture we are looking back
13.6 billion years into the past when the universe was only two percent of its current age. But the Galaxy itself is over 33 billion lightyears away.
How does this make sense? We know that a lightyear is the distance light travels in a year, so if it took the light 13 billion years to reach us it should be 13 billion lightyears away. Well it's not quite as simple as that. In the time that light has spent traveling toward us,
space itself has been constantly expanding and the galaxy has been moving further away from us. Because of this, the Galaxy in 2023 is now over
33 billion lightyears away but its light from 13 billion lightyears away has only just reached us. But how could we possibly measure this distance? The answer lies within the color of the Galaxy. All of the light we see is just a small fraction
of the light that actually exists. Every form of light can be thought of as a wave and the length of that wave can be smaller or longer;
this is what determines the colors that we see. But our eyes are very limited, and so there is much more light bouncing around us that we simply can't see. So when we discover a Galaxy that has changed color, something must have happened to it. Just like the moving car, the light from this
Galaxy is being changed or redshifted but there are two kinds of redshift;
Doppler redshift and cosmological redshift. In the Doppler scenario, the Galaxy is moving
through space, but with cosmological redshift the Galaxy is both moving and stationary at the
same time - we'll get to that one later. First, let's imagine the Galaxy as if it was stationary.
The light leaves the Galaxy in every direction at a constant speed. When the Galaxy moves through space
the waves at the front get slightly compressed and the waves at the back get stretched out. Since
it's traveling away from us, we are receiving the stretched light which has a longer wavelength and
therefore a different color. But why is the galaxy moving in the first place? The planets in our solar system have movement,
our solar system has movement and our galaxy itself is also moving through space,
but this isn't enough to see a dramatic effect in redshift since this relative movement is nowhere
near the speed of light. But remember that this galaxy has gone from 13 billion lightyears to
over 33 billion lightyears away - a distance only possible if it was going considerably faster
than the speed of light. Understanding how this happened is pretty complicated but understanding the basics of our
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PRIMALSPACE to get 50 off your first month. Since the Big Bang nearly 14 billion years ago,
our universe has been constantly expanding but understanding what this actually means is pretty
difficult. We Imagine the Big Bang is an explosion that radiates out from a central point, but in
reality there is no center of the universe and no single point where space expands from. If you take any point in the universe, everything will appear to be expanding away from it at the same rate. It's
not that planets, stars, or galaxies are getting bigger but the space between those galaxies
is getting bigger. The rate of this expansion is around 70 kilometers per second for every
3 million lightyears of distance, so an object at that distance will be 70 kilometers further
away after a second, an object 3 million lightyears further down the line will be 140 kilometers
further away, and so on. If we extrapolate that out to Galaxy GS z13, it will be moving away from us
at around 7 hundred thousand kilometers per second but we're told that objects can't move faster
than the speed of light, but that is only true for objects moving through space - this is where
cosmological redshift comes in. If we look at an unbaked cookie we have a random scattering of
chocolate chips which we can think of as galaxies When the cookie gets baked, the dough expands and
the chips end up further away from each other but it's not that the chips have moved relative to
the dough, but the dough in between the chips has expanded just like our universe. The galaxies in
our universe can't move through space faster than the speed of light, but there is no limit to how
fast the universe can expand. This means that the light currently being
emitted from this galaxy
will never reach us since the expansion of the universe at this distance is out- racing the speed .of light but how do we know all of this? How do we know
how far away this galaxy is? Well, although our planets and galaxies don't
grow with the expansion of space light waves do. As the light
from the galaxy has been traveling through space the expansion of space itself has stretched this
wave of light to a much longer wavelength, and so by the time the light reached James Webb it had
been stretched well outside of our normal viewing range. But the James Webb Telescope was designed
to view light in the infrared range, so it was just capable of picking up this light. The trick
to measuring how old and distant the light is lies within measuring how much that light has been
shifted. So James Webb looked for galaxies whose
light had been shifted the most. It first focused on a tiny area of our night sky
called the Ultra Deep Field. This area is the equivalent of a coin placed 18 meters away, but it features over 100,000 galaxies many of which have gone through a
large amount of redshift, but the problem is that James Webb's time is precious and it would take
forever to survey every little dot in the galaxy. So, in order to choose which galaxies to study
it used something known as the Lyman technique. Light with a wavelength below 90 nanometers gets
completely absorbed by hydrogen - this shows up as a dramatic drop-off at around here on the Spectrum.
So below this, no light should reach us. For that has been redshifted, that drop-off point will
appear much further up the spectrum and so by doing a relatively quick spectroscopy measurement, Webb found four galaxies that all had a drop-off point that had been shifted
all the way into the mid-infrared range One of these was Galaxy Gsz13. This galaxy had the highest amount of redshift
that scientists had ever seen. But calculating the exact redshift amount is what allows us to find out
how old and distant this galaxy is. We can use the spectrum of light as a reference
point. Light gets absorbed by various elements at different wavelengths creating a signature on
the spectrum - a recognizable pattern that will be the same for all light. As the light from the
galaxy gets redshifted, that signature will also be shifted by the same amount. And so, with the light
from Galaxy GS z13 we should see this signature appear further up in the spectrum. By taking specific points and measuring how
much they have been shifted divided by the original wavelength,
we get an exact redshift value. This alone doesn't tell us much, but after some complex calculations
that are too long for this video, we can arrive at the travel time - this is how long the light we
see has been traveling through space to get to us. We can calculate this because we already know
some important characteristics about the universe. We know that the universe is expanding and the
rate at which it expands, and although this rate is constant, galaxies actually accelerate away from
us. This is because the rate at which galaxies move away from us changes over distance and not time.
When Galaxy GS z13 was much closer to us there was less space in between us, therefore less space to
expand. Now the space between us is much larger and so there is much more expansion going on. And so
by understanding how this expansion changes over time we can calculate the light from this galaxy
to be around 13.6 billion years old. What is most shocking about all of this is just how
much we can't see and will never see. We talk about if there is life on Mars, but looking at the sheer scale of the universe we can't even see, it seems completely inevitable that life exists somewhere
out there. And now for the Primal space giveaway. The winner of the previous giveaway is Kirk
Bryson. Congratulations! In the next video we'll be giving away this awesome space shuttle Lego
set. All you need to do is sign up at the link below, leave a like on the video, post a comment
with your thoughts on the possibility of life in our universe. Thank you very much for watching
and I'll see you in the next video. [Music]
