As we know, many students ask one common question: Where does space actually begin?
The simple and most accepted answer is Kármán Line.
Let’s understand this topic आसान भाषा में, step by step.
What is the Kármán Line?
The Kármán Line is an imaginary boundary that separates Earth’s atmosphere and outer space.
- It is present at a height of 100 km above sea level
- Below this line → atmosphere exists
- Above this line → space begins
Means, after crossing this line, an object is considered to be in space.
Why 100 km is taken as the boundary?
Now the main logic comes here.
At around 100 km height:
- Air becomes extremely thin
- Normal aircraft cannot fly
- Wings stop producing enough lift
At this height, an object must move at very high speed (orbital speed) to stay up.
So, flight is no longer aerodynamic, it becomes orbital motion.
This idea was given by Theodore von Kármán.
That’s why this boundary is called the Kármán Line.
Simple example to understand
मान लो:
- Below 100 km → airplane flies using wings
- Above 100 km → satellite moves using speed, not wings
So, the change from flying to orbiting happens near the Kármán Line.
Is the Kármán Line officially accepted?
Yes, mostly.
- Fédération Aéronautique Internationale (FAI) defines space starting at 100 km
- Many countries and space agencies follow this rule
- Some organizations use 80 km, but 100 km is globally popular
For exams and academic purposes, 100 km is the correct and safe answer.
Why is the Kármán Line important?
This line is important for many reasons:
- To clearly define where space starts
- To decide who is an astronaut
- For space laws and international agreements
- For satellite and rocket classification
- For designing rockets and spacecraft
Kármán Line and rockets
When a rocket is launched:
- It crosses 10 km → commercial aircraft zone ends
- It crosses 50 km → upper atmosphere
- It crosses 100 km → Kármán Line crossed (entered space)
Usually, rockets cross the Kármán Line in 3 to 5 minutes after launched.
Author
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Aditya Raj Anand (Msc Physics student) is a dedicated book author and the founder of Science laws a well-regarded blog that deliver science related News and Education. Aditya holds a Bachelor of Science (B.Sc.) in Mathematics, currently doing Master in Physics. A discipline that has fueled his lifelong passion for understanding and demonstrating complex scientific principles. Throughout his academic journey, he developed a deep interest in simplifying challenging concepts in science and making them more accessible to a wider audience. He is written science for more than 5 years. He has served as a writer, editor and analyst at science laws since its inception.
As an author, He published Physics for class 9, physics for class 10, General science and technology For BPSC & UPSC
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You can also connect with Aditya on Instagram at @sciencelaws.in, where he shares his thoughts and provides explanations on topics related to space, Technology, Physics, Chemistry and Scriptures.
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