# Randall Munroe Explains General Relativity

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1. Nov 24, 2015

### Ygggdrasil

Randall Munroe, creator of the webcomic XKCD, wrote a piece for the New Yorker, in which he explains special and general relativity using only the thousand most common words in the English language. Here's an excerpt.

Read the full piece at: http://www.newyorker.com/tech/elements/the-space-doctors-big-idea-einstein-general-relativity

2. Nov 29, 2015

### Greg Bernhardt

Really fantastic idea! We need more of these for the general public!

3. Nov 29, 2015

### Ygggdrasil

Perhaps this could be an idea for a Insights article. Take your favorite topic and write an explanation of it using only the one thousand most common words in the English language. XKCD even has a tool to check whether what you have written fits the criteria: http://xkcd.com/simplewriter/

4. Nov 30, 2015

### UncertaintyAjay

I reckon its also a good way to test whether you understand something really well. Fun thing to do at home - explaining something to yourself using the thousand most common words

5. Nov 30, 2015

### lightarrow

I appreciate when he writes:

"To make the ideas easier to explain, people will often tell you to imagine something more familiar, like a big flat sheet with weights on it. These pictures are good, but sometimes they make you think of new questions, and when you try to use the picture to answer the new questions, you get answers that don’t fit with each other."

The problem is that other things he writes are incorrect the same, as:

"If you go really fast, time goes slower."
"He showed that if time itself goes slower near heavy things,"

--
lightarrow

6. Nov 30, 2015

### UncertaintyAjay

I'm not sure how that is incorrect. If you go really fast, time does go slower for you. Time also slows down near heavy things. I do not think those statements are incorrect.

7. Nov 30, 2015

### bhobba

Since you are in a rest frame relative to yourself nothing at all happens. Time slows down for the person moving relative to you. The same thing happens for the other person - its symmetric like that.

Thanks
Bill

8. Nov 30, 2015

### lightarrow

There is a difference in the time intervals signed by different clocks in relative motion or in different gravitational potentials, but you have to refer those time intervals to the same couple of events. Said another way: those two clocks have to be compared before and after one of the two goes very fast or goes to a lower gravitational potential. But the fact they sign different times when finally compared does not mean that all the physical/chemical/biological processes of the one which travelled fast or went near the massive object, have slowed: it's due, instead, to the different paths through spacetime.

Using a metaphor: two cars start from the same position A and reach the same position B travelling at the same constant speed v, but when in B they compare their odometers and find that they sign a different number of km covered. Why? Their odometers have worked at the same exact speed, neither one nor the other have "slowed down". The two cars have simply gone through two different paths. Here the km covered stay for the time interval in the relativistic case.

--
lightarrow

9. Nov 30, 2015

### Staff: Mentor

We have a large machine making sky bag air very fast, and hit each other. We are looking for new kinds of stuff created in the hits. 2012 we found a new kind of stuff that we did not see before. Its life is very short: It disappears and other (known) kinds of stuff appear at its place. Those we can see with the big machine.

Ouch :D
No "particles" makes particle physics hard to explain.

10. Nov 30, 2015

### newjerseyrunner

I'm going to call probes "space boats" from now on.

11. Nov 30, 2015

### UncertaintyAjay

Thanks.

12. Dec 1, 2015

### mheslep

Yes, but easier said than done. Randall Munroe is a quite a talented communicator of scientific ideas. I find it is no trivial task to make complicated technical ideas accessible to the layman while maintaining accuracy, and Munroe masters the challenge while adding humor at the same time.

13. Dec 1, 2015

### Ygggdrasil

Here are some examples from around the internet of simple explanations of science:
Drug discovery: http://blogs.sciencemag.org/pipeline/archives/2013/01/16/drug_discovery_with_the_most_common_words
Organic chemistry: http://justlikecooking.blogspot.com/2013/01/make-new-things-with-window.html
A Tumblr with many more examples: http://tenhundredwordsofscience.tumblr.com/

And, since @mfb gave it a shot, I might as well:

We all have a body plan inside of us that tells our body how it should look and work. Humans, fish, and other animals look very different because they have very different body plans. Different people also have different body plans, and this is why people have different hair colors or different eye colors. Babies look like their parents because they get their body plans from their parents: half of the body plan comes from their mother and half of their body plan comes from their father.

Different parts of our bodies also look very different from each other. Skin looks very different from hearts, which are both very different from brains. However, the same body plan is inside of our skin, hearts, and brains. I study how the same body plan can make different body parts. This is important because if something goes wrong in how our body reads the body plan, people can grow up to have many problems or get sick. Like if your head reads the wrong part of your body plan you might have a leg growing out of your head (this happens in some flies with problems in their body plan).

Part of the reason why the same body plan can make different body parts is that not all of the body plan is open for our bodies to read. In the parts of our body that will become skin, the parts of the body plan that tell the body how to be skin are open, but the parts of the body plan that tell the body how to be brain or how to be heart are closed. What I look at are tiny engines inside of our bodies that help change what parts of the body plan are open or closed. How do these engines work? What tells these engines to open up certain parts of our body plan and not others? How does our body turn these engines on or off? These are the questions I try to answer when I go to work.

I guess I know whether my explanation is any good if people can come up with the technical term for the thing I study.

14. Dec 2, 2015

### anorlunda

Einstein's own book, Relativity, explains SR as you say in the article with relative motion on a train. But his 1905 SR paper was about electromagnetism.

The same book used the windowless elevator, not the bending of light, to introduce GR.

What does history say about which thinking led the doctor to his conclusions?

15. Dec 3, 2015

### Smattering

I do get the overall meaning, but I am still wondering what you are referring to by "sky bag air".

16. Dec 3, 2015

### Smattering

That was really nice. So probably you study epigenetics?

17. Dec 3, 2015

### Smattering

But at least "part" is among the most common words. So, you probably would have to go for "smallest parts that all things are made of" or something like this.

18. Dec 3, 2015

### Ygggdrasil

19. Dec 3, 2015

### mheslep

20. Dec 3, 2015

### OmCheeto

I recall "sky bag air" from "Up Goer Five".

It was my first introduction "Thing Explaining".

This was my first thought when I first saw the article.
A couple of PFers have been egging me on to write an electrical analogy, which so far, I've only come up with the title for: "Why did the electrically charged spherical chicken cross the road?"
But the "Simple Writer" thing says that "chicken" is a big word, so this may further delay my progress.