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3 Dec 2025
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Understanding Space: GCSE Physics Triple Higher
H
Hannah
@hannnah_study
Planets, Satellites and Orbits
Your understanding of planetary motion starts with a simple fact: Earth orbits the Sun in an almost perfect circle, whilst other planets follow slightly squashed circular paths called ellipses. The Moon, as Earth's natural satellite, demonstrates the same circular orbital principles on a smaller scale.
Gravitational attraction between two bodies creates the force that keeps objects in orbit. This force always points towards the centre of the circular path, which is why satellites don't fly off into space. Think of it like swinging a ball on a string - the tension pulls inward just like gravity does.
Here's what makes orbital motion so clever: as a body moves around its circular path, its speed stays constant but its direction constantly changes. This continuous change in direction creates acceleration towards the centre, and each orbiting body must travel at exactly the right speed to maintain its distance from the larger object.
Key Point: The faster you want to orbit, the closer to the central body you need to be - this is why the International Space Station orbits much faster than the Moon!
Red-Shift and Expanding Universe
You can actually see the universe expanding by studying red-shift - one of the most important discoveries in modern physics. When light from distant galaxies reaches Earth, its wavelength appears stretched towards the red end of the spectrum because those galaxies are moving away from us.
Edwin Hubble made the groundbreaking observation that all distant galaxies show red-shift, and crucially, the further away a galaxy is, the greater its red-shift. This means more distant galaxies are moving away faster than closer ones - exactly what you'd expect from an expanding universe.
The balloon analogy makes this easier to visualise: imagine galaxies as dots on a balloon's surface. As you inflate the balloon, every dot moves away from every other dot, with the furthest dots separating fastest. This is precisely what's happening to our universe on a cosmic scale.
Remember: Red-shift occurs because light wavelengths get stretched as the source moves away, making the light appear more red and less blue.
Evidence for the Big Bang
The Big Bang Theory explains how our universe began from an incredibly small point and has been expanding ever since. This cosmic explosion didn't just create matter - it created space and time itself, which sounds mental but is supported by solid evidence.
Cosmic Microwave Background (CMB) radiation provides the smoking gun evidence for the Big Bang. When the universe was young and incredibly hot, it emitted intense, short-wavelength radiation. As the universe expanded over billions of years, this radiation got stretched into microwaves that we can still detect today.
What makes CMB so convincing is that it's everywhere - point a telescope in any direction and you'll detect this background radiation. This uniform distribution proves the entire universe was once in an extremely hot, dense state that has since cooled and expanded.
The combination of red-shift observations showing universal expansion and CMB radiation proving the universe was once much hotter makes the Big Bang the most widely accepted scientific model. However, mysteries like dark matter and dark energy remind us there's still loads we don't understand about our universe.
Think About It: The CMB radiation you can detect today is literally the afterglow of the Big Bang - you're seeing evidence of the universe's birth!
We thought you’d never ask...
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This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
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Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
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Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
Understanding Space: GCSE Physics Triple Higher
H
Hannah
@hannnah_study
Ever wondered how planets stay in orbit or why the universe is expanding? This fascinating topic explores how gravitational forceskeep celestial bodies moving in predictable paths and how scientists discovered that our universe began with the Big Bang through... Show more
Planets, Satellites and Orbits
Your understanding of planetary motion starts with a simple fact: Earth orbits the Sun in an almost perfect circle, whilst other planets follow slightly squashed circular paths called ellipses. The Moon, as Earth's natural satellite, demonstrates the same circular orbital principles on a smaller scale.
Gravitational attraction between two bodies creates the force that keeps objects in orbit. This force always points towards the centre of the circular path, which is why satellites don't fly off into space. Think of it like swinging a ball on a string - the tension pulls inward just like gravity does.
Here's what makes orbital motion so clever: as a body moves around its circular path, its speed stays constant but its direction constantly changes. This continuous change in direction creates acceleration towards the centre, and each orbiting body must travel at exactly the right speed to maintain its distance from the larger object.
Key Point: The faster you want to orbit, the closer to the central body you need to be - this is why the International Space Station orbits much faster than the Moon!
Red-Shift and Expanding Universe
You can actually see the universe expanding by studying red-shift - one of the most important discoveries in modern physics. When light from distant galaxies reaches Earth, its wavelength appears stretched towards the red end of the spectrum because those galaxies are moving away from us.
Edwin Hubble made the groundbreaking observation that all distant galaxies show red-shift, and crucially, the further away a galaxy is, the greater its red-shift. This means more distant galaxies are moving away faster than closer ones - exactly what you'd expect from an expanding universe.
The balloon analogy makes this easier to visualise: imagine galaxies as dots on a balloon's surface. As you inflate the balloon, every dot moves away from every other dot, with the furthest dots separating fastest. This is precisely what's happening to our universe on a cosmic scale.
Remember: Red-shift occurs because light wavelengths get stretched as the source moves away, making the light appear more red and less blue.
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Evidence for the Big Bang
The Big Bang Theory explains how our universe began from an incredibly small point and has been expanding ever since. This cosmic explosion didn't just create matter - it created space and time itself, which sounds mental but is supported by solid evidence.
Cosmic Microwave Background (CMB) radiation provides the smoking gun evidence for the Big Bang. When the universe was young and incredibly hot, it emitted intense, short-wavelength radiation. As the universe expanded over billions of years, this radiation got stretched into microwaves that we can still detect today.
What makes CMB so convincing is that it's everywhere - point a telescope in any direction and you'll detect this background radiation. This uniform distribution proves the entire universe was once in an extremely hot, dense state that has since cooled and expanded.
The combination of red-shift observations showing universal expansion and CMB radiation proving the universe was once much hotter makes the Big Bang the most widely accepted scientific model. However, mysteries like dark matter and dark energy remind us there's still loads we don't understand about our universe.
Think About It: The CMB radiation you can detect today is literally the afterglow of the Big Bang - you're seeing evidence of the universe's birth!
We thought you’d never ask...
What is the Knowunity AI companion?
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
Where can I download the Knowunity app?
You can download the app from Google Play Store and Apple App Store.
Is Knowunity really free of charge?
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
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Most popular content in Physics
Most popular content
English - inspector calls quotes and analysis
Quotes from every main character
English Literature10
Can't find what you're looking for? Explore other subjects.
Students love us — and so will you.
4.9/5
App Store
4.8/5
Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user