# Explaining to a layperson

1. Oct 26, 2009

### runner

How would you explain the Theory of Relativity to someone in non-mathematical, everyday language?

2. Oct 26, 2009

### ice109

going in circles is the same as being on a spaceship that´s speeding up

3. Oct 26, 2009

### magpies

First I would learn it as a layperson...

4. Oct 26, 2009

### DavidSnider

Cosmos Part 8:

Last edited by a moderator: May 4, 2017
5. Oct 26, 2009

### sokrates

I hope you mean the "special relativity"..

(1) speed of light is constant for all non-accelerating observers contrasting everyday classical relativity...
(2) All physical laws are equivalent for non-accelerating observers.

You can even skip (2) in the beginning.
Then contrast (1) by giving an example: You run with 5 mi/h and a car passes by 10 mi/h (same direction) you'd "conclude" that it travels by 5 mi/h in the same direction. Have her/him accept it for a fact that with light your observation is always c!

Then the rest is easy: Two observers. One in a train, other on the ground. Put a mirror in the train (vertical), and the observers measure different lengths traveled by light, yet they observe the same speed of light. Then obviously their clocks must be running differently! Now you can easily jump to time dilation and the twin paradox (not mentioning how the paradox arises, or is resolved because they involve more subtle points). But that should be enough.

Voila!

Last edited: Oct 26, 2009
6. Oct 26, 2009

### Pinu7

Einstein's Relativity which you can find at any bookstore.

I explained it to my little sister( 8th grade, but smart) starting with this.

Me: Let us say you were racing a cheetah, you are going 12 mile/hr and he is going at 32 miles an hour, how fast is does he LOOK LIKE he's moving to you.

Her: What do you mean?

Me: If you and the cheetah are moving at the same direction, it looks like he is going slow...

Her: Oh! 20 miles an hour!

Me: Good! How did you obtain that

Her: I subtracted.

Me: Good, this is known as Galilean Relativity. Which means if you are moving and another object was moving, you would subtract your speed form the object's speed to obtain how fast the object LOOKS LIKE it is moving. This is known as relative speed.

Her: Mmhhhhmmm..... I get it.

Me: What about a beam of light? Let us say that light moves at c miles an hour, where c is just a positive number. And you moving at c-1 miles an hour, what is the relative motion of light.

Her: *thinks about it* one mile an hour?

Me: According to Galilean relativity, yes, you are correct. However, scientific experimentation done over a hundred years ago surprisingly found that the speed of light's relative speed is always c, no matter how fast you are moving.

Her: I'm confused, that makes no sense.

Me: It didn't to the scientists ,either, until Albert Einstein discovered that Galilean relativity is wrong and only worked approximately when your and the object's speed is far less than the speed of light, which is about 670 million miles an hour. He found another principal of relative speed called special relativity.

7. Oct 26, 2009

### jgens

"When a man sits with a pretty girl for an hour, it seems like a minute. But let him sit on a hot stove for a minute and it's longer than any hour. That's relativity."

~Albert Einstein

Edit: I realize that this quote isn't really pertinent but it's the first thing that came to mind when I read your question.

8. Oct 26, 2009

### Jimmy Snyder

When I have the opportunity to do so, I explain using Pinu7's approach. I also point out that speed is distance divided by time. The only way that the speed of light can be the same for all observers is if distance, or time, or both get distorted somehow.

9. Oct 26, 2009

### runner

Great replies so far, and I like the way the explanations are becoming easier and easier to explain so far. I may have some luck with my grandmother yet.

10. Oct 26, 2009

### WhoWee

Try using dollars.

11. Nov 24, 2009

### solarflare

Me: What about a beam of light? Let us say that light moves at c miles an hour, where c is just a positive number. And you moving at c-1 miles an hour, what is the relative motion of light.

Her: *thinks about it* one mile an hour?

Me: According to Galilean relativity, yes, you are correct. However, scientific experimentation done over a hundred years ago surprisingly found that the speed of light's relative speed is always c, no matter how fast you are moving.

Her: I'm confused, that makes no sense.

Me: It didn't to the scientists ,either, until Albert Einstein discovered that Galilean relativity is wrong and only worked approximately when your and the object's speed is far less than the speed of light, which is about 670 million miles an hour. He found another principal of relative speed called special relativity.[/QUOTE]

what was the experiment conducted and who conducted it. i would like to explore this in more detail. very interesting

12. Nov 24, 2009

### mgb_phys

13. Nov 24, 2009

### OmCheeto

I see where you're going with this: