Have you ever noticed how the sound of a car changes as it zooms past you? This change in pitch is called the Doppler effect. If light moved slowly enough, we would see a similar effect with colors. However, light travels too fast for us to notice such changes in our everyday lives.
Let’s explore the image of Galaxy GS z13. It appears red because its light has been shifted to a longer wavelength, a phenomenon known as redshift. This is similar to the Doppler effect but for light. The light from this galaxy has traveled for 13.6 billion years to reach us, allowing us to look back in time to when the universe was just a fraction of its current age.
Although the light from Galaxy GS z13 took 13 billion years to reach us, the galaxy is now over 33 billion light-years away. This is because the universe has been expanding, stretching the space between us and the galaxy. This expansion means that the galaxy is moving away from us faster than the speed of light, but not in the way you might think. It’s not the galaxy itself moving through space at this speed; instead, the space between us is expanding.
To measure the distance to such distant galaxies, scientists look at the color of the light. Light is a wave, and its wavelength determines its color. Our eyes can only see a small portion of the light spectrum, but telescopes like the James Webb Space Telescope can detect infrared light, which is beyond our visual range.
When a galaxy’s light is redshifted, it means the light waves have been stretched to longer wavelengths. By measuring how much the light has shifted, scientists can determine how far away the galaxy is and how long its light has been traveling.
To identify distant galaxies, scientists use a method called the Lyman technique. Light with a wavelength below 90 nanometers is absorbed by hydrogen, creating a noticeable drop-off in the light spectrum. When this light is redshifted, the drop-off point moves up the spectrum. By measuring this shift, scientists can find galaxies like GS z13, which have experienced significant redshift.
Since the Big Bang nearly 14 billion years ago, the universe has been expanding. This expansion doesn’t mean galaxies are getting bigger; rather, the space between them is increasing. Imagine a cookie with chocolate chips as galaxies. As the cookie bakes, the dough expands, moving the chips further apart. Similarly, the universe’s expansion stretches the space between galaxies.
Because of this expansion, the light from distant galaxies like GS z13 is stretched, making it appear redder. The James Webb Space Telescope can detect this stretched light, allowing us to study galaxies that are billions of years old.
As we explore the universe, we realize how much we can’t see and may never see. The vastness of the universe suggests that life could exist elsewhere, beyond our current reach.
In conclusion, the James Webb Space Telescope’s ability to capture light from distant galaxies like GS z13 provides us with a glimpse into the early universe. This understanding of redshift and the expanding universe helps us piece together the history of our cosmos and fuels our curiosity about the possibility of life beyond Earth.
Engage in a hands-on activity where you simulate redshift using a simple light source and colored filters. Observe how the color changes as you move the light source away from you, mimicking the redshift effect. Discuss how this relates to the light from distant galaxies like GS z13.
Create a model of the expanding universe using a balloon and markers. Draw galaxies on the balloon’s surface and inflate it to see how the galaxies move apart. Reflect on how this demonstrates the concept of the universe’s expansion and its impact on light traveling through space.
Use a prism or diffraction grating to explore the visible light spectrum. Identify the different colors and discuss how telescopes like the James Webb Space Telescope can detect wavelengths beyond our visual range, such as infrared light, to study distant galaxies.
Conduct an experiment to observe the Doppler effect using sound. Use a toy car with a sound source and move it past a group of students. Discuss how the change in pitch relates to the redshift of light from galaxies moving away from us.
Research and present on the Lyman technique used to identify distant galaxies. Explain how scientists use this method to measure redshift and determine the distance of galaxies like GS z13. Share your findings with the class in a presentation.
Here’s a sanitized version of the provided YouTube transcript:
—
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 slowly 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.
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 an 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 light-years away.
How does this make sense? We know that a light-year 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 light-years 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 light-years away, but its light from 13 billion light-years 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 determines the colors that we see. But our eyes are very limited, and so there is much more light around us that we simply can’t see.
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.
First, let’s imagine the galaxy as if it were 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.
Remember that this galaxy has gone from 13 billion light-years to over 33 billion light-years 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 solar system is really easy, thanks to KiwiCo, the sponsor of today’s video.
This is their Kiwi Crate Solar System project, a great way to introduce your kids to our fascinating world and teach them how our planets orbit the Sun. KiwiCo makes learning about space, science, engineering, and more topics super fun with their awesome monthly crates. Each crate is designed by experts and tested by kids, and with nine different lines to choose from, there’s something for every age and interest. All the supplies needed for each project come inside the crate, so there’s no need for extra runs to the store. KiwiCo also offers individual crates for purchase online in the KiwiCo store.
KiwiCo is the best way to get your kids away from the screen and learning about the wonders of space and science while having fun. Click the link in the description or use code 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 as 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 light-years of distance. So an object at that distance will be 70 kilometers further away after a second, and an object 3 million light-years 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 700,000 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; 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 outpacing 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 the James Webb Space Telescope, 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 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. 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 a specific point on the spectrum. For light that has been redshifted, that drop-off point will appear much further up the spectrum, and by doing a relatively quick spectroscopy measurement, Webb found four galaxies that all had a drop-off point that had been shifted into the mid-infrared range. One of these was Galaxy GS z13.
This galaxy had the highest amount of redshift that scientists had ever seen. Calculating the exact redshift amount 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.
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, 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. 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 giveaway. The winner of the previous giveaway is Kirk Bryson. Congratulations! In the next video, we’ll be giving away the awesome space shuttle Lego set. All you need to do is sign up at the link below, leave a like on the video, and 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]
—
This version removes any unnecessary or potentially sensitive information while maintaining the core content and educational value of the transcript.
Redshift – A phenomenon where the wavelength of light from an object is increased, typically observed in distant galaxies moving away from us, indicating the expansion of the universe. – The redshift of light from distant galaxies provides evidence for the expanding universe theory.
Galaxy – A massive system of stars, stellar remnants, interstellar gas, dust, and dark matter, bound together by gravity. – The Milky Way is the galaxy that contains our solar system.
Light – Electromagnetic radiation that is visible to the human eye and is responsible for the sense of sight. – Light from the sun takes about 8 minutes to reach Earth.
Universe – The totality of known or supposed objects and phenomena throughout space; the cosmos; everything that exists, including all matter and energy. – The universe is estimated to be about 13.8 billion years old.
Expansion – The increase in distance between any two given gravitationally unbound parts of the observable universe with time. – The expansion of the universe was first observed by Edwin Hubble in the 1920s.
Wavelength – The distance between successive crests of a wave, especially points in a sound wave or electromagnetic wave. – The wavelength of visible light determines its color.
Distance – The amount of space between two points, often measured in light-years in astronomy. – The distance to the nearest star, Proxima Centauri, is about 4.24 light-years.
Telescope – An optical instrument designed to make distant objects appear nearer, containing an arrangement of lenses or mirrors or both that gathers visible light, allowing direct observation or photographic recording. – The Hubble Space Telescope has provided some of the most detailed images of distant galaxies.
Hydrogen – The lightest and most abundant chemical element in the universe, consisting of one proton and one electron. – Hydrogen is the primary fuel for nuclear fusion in stars.
Big Bang – The prevailing cosmological model explaining the observable universe’s origin from a singularity approximately 13.8 billion years ago. – The Big Bang theory describes how the universe expanded from an extremely hot and dense initial state.
