Randall Munroe Explains General Relativity

[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.

People have known for a long time that you can’t say how fast something is moving until you’ve said what it’s moving past. Right now, you might not be moving over the ground at all, but you (and the ground) are moving very fast around the sun. If you say that the ground is the thing sitting still, you’re not moving, but if you say that the sun is, you are. Both of these are right: it’s just a question of what you say is sitting still.

Some people think that this idea about moving was the space doctor’s big idea, but it wasn’t. This idea had been around for hundreds of years before him. The space doctor’s idea came up because there was a problem with the old idea of moving.

The problem was light.

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

 

[Greg Bernhardt]

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

 

[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/

 

[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

 

[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

 

[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.

 

[bhobba]

I'm not sure how that is incorrect. If you go really fast, time does go slower for you.

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

 

[lightarrow]

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.

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 traveled 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 traveling 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

 

[mfb]

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/

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.

 

[newjerseyrunner]

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

 

[UncertaintyAjay]

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 traveled 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 traveling 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

Thanks.

 

[mheslep]

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

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.

 

[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.

 

[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?

 

[Smattering]

We have a large machine making sky bag air very fast,

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

 

[Smattering]

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

That was really nice. So probably you study epigenetics?

 

[Smattering]

No "particles" makes particle physics hard to explain.

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.

 

[Ygggdrasil]

That was really nice. So probably you study epigenetics?

Yup. You got it. ATP-dependent chromatin remodeling enzymes in particular.

 

[mheslep]

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

 

[OmCheeto]

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

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

It was my first introduction "Thing Explaining".

Perhaps this could be an idea for a Insights article.

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.

 

[Tolklein]

"Hey Jimmy, what do you want to be when you grow up?"
"A SPACE DOCTOR"

I think Fireman and Astronaut are going to take a back seat to that profession.