ClassX Video Lessons What we know for certain about the universe—and what we don’t | Michelle Thaller
Galaxies are enormous groups of stars, with each galaxy containing hundreds of billions of stars. Our galaxy, the Milky Way, has about 500 billion stars. To understand its size, imagine that the Milky Way is around 100,000 light-years wide. Since one light-year is about six trillion miles, this makes our galaxy incredibly huge.
Here’s a fun way to picture it: if the sun were the size of the dot on the letter “i” in a book, the Milky Way would be as big as Earth. This shows just how massive a single galaxy can be.
We still don’t know exactly how many galaxies exist, but the Hubble Space Telescope has helped us learn a lot. Hubble looked at a tiny, seemingly empty part of the sky for over a month and found more than 5,000 galaxies that were too faint to see before.
To understand this, think about holding a book at arm’s length and looking at the dot on an “i.” That tiny spot is like the area Hubble studied, yet it contained thousands of galaxies. If we apply this to the whole sky, scientists think there could be several trillion galaxies that Hubble could see if it had enough time.
Even though Hubble has taught us a lot, there are limits to what we can see. The universe is about 13.8 billion years old, so we can only see as far as light has traveled since the Big Bang. This creates a boundary called the observable universe, beyond which we can’t see.
The James Webb Space Telescope, launched in 2020, aims to look even further back in time to see galaxies that formed early in the universe, helping us learn more about the cosmos.
Despite our progress, we still don’t know the true number of galaxies. The universe might be much larger than what we can see, and it could even be infinite. If that’s true, there could be an endless number of galaxies out there.
On the other hand, the universe might have a shape or boundaries we don’t understand yet. Just like how Earth seems flat when we look at it, the universe might have a complex structure we can’t perceive.
In conclusion, while we’ve made great strides in estimating the number of galaxies in the observable universe, the big question remains: how many galaxies are there? We still don’t have a definite answer as we continue to explore the vastness of space and try to understand its true nature. For now, we can only imagine the endless possibilities beyond what we can currently observe.
Using craft supplies like paper, glue, and glitter, create a model of a galaxy. Think about the size and shape of the Milky Way and try to represent it in your model. This will help you visualize the vastness of galaxies and their components.
Use an online telescope simulator to explore different parts of the sky. Try to identify galaxies and note how many you can find in a small section. This activity will give you a sense of what astronomers do and how they discover new galaxies.
Conduct a research project on the Hubble Space Telescope. Present your findings on how it has contributed to our understanding of galaxies. This will deepen your knowledge of the tools scientists use to explore space.
Participate in a class debate on whether the universe is infinite or has boundaries. Use evidence from the article and other sources to support your argument. This will help you develop critical thinking and public speaking skills.
Write a short story about a journey through the universe, exploring different galaxies. Use your imagination to describe what you might find and how it would feel to travel through space. This will encourage creative thinking and application of what you’ve learned.
Galaxies – Large systems of stars, gas, and dust held together by gravity. – Example sentence: Our solar system is part of the Milky Way, which is one of billions of galaxies in the universe.
Universe – All of space and everything in it, including stars, planets, and galaxies. – Example sentence: Scientists study the universe to understand its origins and the forces that govern it.
Telescope – An instrument that makes distant objects appear closer and larger, used for observing celestial bodies. – Example sentence: The astronomer used a powerful telescope to observe the rings of Saturn.
Light-year – The distance that light travels in one year, about 9.46 trillion kilometers. – Example sentence: The nearest star to Earth, Proxima Centauri, is about 4.24 light-years away.
Stars – Massive, luminous spheres of plasma held together by gravity, producing light and heat. – Example sentence: Stars are born in nebulae, where gas and dust come together under gravity.
Milky Way – The galaxy that contains our solar system, characterized by its spiral shape. – Example sentence: On a clear night, you can see the Milky Way stretching across the sky as a faint band of light.
Observation – The act of watching and studying something carefully to gain information. – Example sentence: Through careful observation, astronomers can determine the composition of distant stars.
Cosmos – The universe seen as a well-ordered whole. – Example sentence: The cosmos is vast and full of mysteries waiting to be discovered by scientists.
Infinite – Without limits or end; extending indefinitely. – Example sentence: The concept of an infinite universe challenges our understanding of space and time.
Big Bang – The scientific theory that explains the origin of the universe as a rapid expansion from a hot, dense state. – Example sentence: According to the Big Bang theory, the universe has been expanding ever since its inception about 13.8 billion years ago.
