Main content

## Breakthrough Junior Challenge

### Course: Breakthrough Junior Challenge > Unit 1

Lesson 3: 2015 Challenge — Physics- Special theory of relativity - 2015 Challenge Winner!
- A visualization of special relativity
- Chromatic aberration
- Orbital mechanics
- What is light?
- Special and general relativity
- The science of fireworks
- Quantum tunneling
- Antimatter
- Special Relativity
- What Einstein missed: The EPR paradox
- Virtual particles and gravity
- Interstellar and Hawking radiation
- All about superconductors
- Entropy and the direction of time
- Magnetism, light and the magneto optic Kerr effect
- The theory of everything

© 2023 Khan AcademyTerms of usePrivacy PolicyCookie Notice

# Special theory of relativity - 2015 Challenge Winner!

By Ryan Chester

110 years ago Albert Einstein published a theory that revolutionized the way we think about the universe. In this video I'll show you how to proveits two postulates using easy-to-understand real-world experiments, and how even the simplest understanding of quantum mechanics can be used to wrap your mind around why time must slow down the faster an object moves.

110 years ago Albert Einstein published a theory that revolutionized the way we think about the universe. In this video I'll show you how to prove

## Want to join the conversation?

- So...time doesn't actually slow down at near light speeds, but rather it's just the distance the subatomic particles travel increasing? Mind blown.(11 votes)
- Or, to restate that per Ryan's explanation (in so many words), the biological effect of traveling at or near the speed of light is that time appears to slow down because subatomic particles have to move across greater distances in order for the chemical processes that cause matter to change to occur, thus aging does not happen as fast (time appears to slow down) as a body that is traveling much slower through space (photons travel shorter distance, aging occurs faster).

So, the secret to longevity is to do everything as fast as you can to stretch the distance those photons must travel through your body. No wonder that 58yo delivery guy from that sandwich shop still looks like an 18yo! :-)(8 votes)

- Can someone give me a list of einsteins laws?(3 votes)
- Hmm... let's see...

(In no particular order)

Special Relativity

General Relativity

Brownian motion

Photoelectric Effect

Photons (Quantization of light)

Contributions to the development of Quantum Theory

Mass-energy equivalence

Introduction of the cosmological constant

Spacetime

And much more. Whew!(10 votes)

- When moving near light speed in one direction, the photons would be traveling at almost double the speed in the opposite direction you are moving though, right? Here's what I mean.

Say a photon wants to get from A to B.

A --------- B

P >>>>>> P

We are moving though, so the photon needs to go even faster.

A >>>>>> B

P >>>>>>>>>>>>>> P

But.... What if it wants to go the other direction?

B >>>>>> A

P <<< P

Wouldn't this even out the effect?(5 votes)- Good point. Your point does not assume all photons are travelling the same direction as a body traveling through space at or near light speed, but are likely travelling in random directions, some even the opposite direction as the body, in which case a photon may appear to move little to none as point B moves to the photon instead.

What can we expect the biological effect to be? Is there a way -- a formula -- to determine the aging process at a given speed?(2 votes)

- Nice video. But you don't really need to 'prove' postulates.(1 vote)
- Good point! However, he is not attempting to 'prove' it, he is showing why we are assuming it. It is still a postulate because it is "assumed true without proof", but he is trying to 'prove' why we assume it is true, to people who may not understand the logic behind the statement.

eg. Like some people may not understand 'Angle Side Angle' postulate for proving congruence. We can show examples, and explain the reasoning, but it is a postulate.

Also, it is not really "assumed true" yet, because it is still a theory.(7 votes)

- To the 'Winning-D' student in math:

1. You showed that acceleration broke your inertial frame: How did you fix it?

2. When length contracts, which end contracts towards which: What is math?

3. Did you measure your inertial equivalence faster than 10⁻⁷ c? [*]

4. A teaser before you blast your brains in college: You believe in Stellar Aberration, which is Angular, Should you believe in Linear, Stellar Aberration by math only, an unknown physics experiment?

5. (This should be a college entry question.) Isaac Newton, likely, knew that colored light was constant speed by looking at comets through his new reflector telescope showing no prismatic effects: heads of comets were white without separating blue and red; But Isaac also noted Roemer's experiment proving the speed of light was finite... Question: If Isaac had math'ed on this, and found that there was an incredible distortion of time-and-space-coordination that neither the Church nor, Galileo himself, would have believed, would Isaac have remained silent, let others do the math and find the same distortion, or would he have written a Secret Principia?

Ray.

* [N.B. that was 1e-7 if 10⁻⁷ doesn't look right in your font space](4 votes) - In the example of the car in the first postulate, what is the significance of the windows blacked out as he said in1:15?(3 votes)
- So the system is closed and your reference frame stays within the car.(2 votes)

- What happens if the frame of the spaceship is considered? Also, does that mean that she actually
*has*grown and that the person left behind just sees her as the same age?(2 votes)- If the frame of the spaceship is considered, time passes much quicker on Earth than on the spaceship. And she actually has grown/aged, just much slower than everyone else on Earth.(2 votes)

- how earth is an internal frame of reference?(2 votes)
- Great question!

Consider a scenario in which only a car (driving on earth), earth (orbiting the sun), and the sun (not moving).

The car is moving relative to the earth. The earth is moving relative to the sun. Because the earth is a frame of reference, but also moving relative to something else (part of another frame) in our scenario, it is an internal frame of reference.

Let's take it a step further and add you into our equation: you are driving the car. You are moving relative to the car. The car is moving relative to the earth. The earth is moving relative to the sun.

Now we have two internal frames of reference! We have one frame where the car provides the reference for the motion of you, another frame where the earth provides the reference for the motion of the car, and a final frame where the earth is moving. This means the car and the earth are both internal frames of reference.

I hope this helps!

If you want more explanation, ask me your questions in the comments for this answer and I'll do my best to answer them.

Or watch this other video on the theory of relativity: https://www.khanacademy.org/partner-content/bjc/2015-challenge/2015-physics/v/bjc-special-theory-relativity(2 votes)

- Omg thanku i finally understood special relativity 😭😭😭(2 votes)
- I don't understand the experiment at2:47. If the one light was traveling against the ethers, would it really go slower? I mean the other light also has to fight against the ethers. But also assuming that other light wasn't effected by the ethers wouldn't the first light make it back faster because it flows with the ethers?

I hope I spelled ether correctly.(2 votes)- well... either way... the ideas of the experiment was that the ether should change the movement of the light... so the interference wouldn't be at the same time or place....

Because it never happened what we were looking for... it means that the experiment failed... demonstrating that there wasn't any ether around...

This became the most Famous Fail Experiment in Modern Physics... showing that light never change and stay constant in all frames of references, specially its velocity (C=300000km/s).

Thanks to this experiment, the wonders of Special Relativity surged!(1 vote)