# does E really equal MC-squared? **URL:** \ **Category:** Factual Questions\ **Created:** [June 1, 2003, 1:01pm UTC](https://boards.straightdope.com/t/does-e-really-equal-mc-squared/178937 "2003-06-01T13:01:21Z")\ **Posts on this page:** 11\ **Page:** 1
**Author:** ![drhess](https://avatars.discourse-cdn.com/v4/letter/d/94ad74/32.png) [@drhess](https://boards.straightdope.com/u/drhess)\ **Post date:** [June 1, 2003, 1:01pm UTC](https://boards.straightdope.com/t/does-e-really-equal-mc-squared/178937/1 "2003-06-01T13:01:21Z")
I think a few months ago there was an article in the NYT about a possible rewrite of E=MC^2. Anybody recall this? Is it a sure thing? I recall it was a kinda small adjustment, so it seems to a layman. Is it a BIG deal? Thanks. ---
**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\ **Post date:** [June 1, 2003, 3:22pm UTC](https://boards.straightdope.com/t/does-e-really-equal-mc-squared/178937/2 "2003-06-01T15:22:33Z")
I’ll bet you are referring to this article: > [@](#): > > Science Desk | December 31, 2002, Tuesday > E and mc2: Equality, It Seems, Is Relative > > By DENNIS OVERBYE (NYT) 2322 words > Late Edition - Final , Section F , Page 1 , Column 5 > ABSTRACT - Article on recent interest among physicists over whether Einstein’s general theory of relativity, bedrock of all modern physics and technology, has limits and may need to be overhauled; photos (M) Roll over, Einstein. > > In science, no truth is forever, not even perhaps Einstein’s theory of relativity, the pillar of modernity that gave us E=mc2. The website wants money for the full article so I don’t know exactly which aspects Overbye might be referring to. Maybe somebody else here remembers. One possibility is that there have been many recent experiments suggesting that constants, such as the speed of light, may have shifted slightly in the early universe. From the New Scientist website, I found [Black hole theory suggests light is slowing](http://www.newscientist.com/news/news.jsp?id=ns99992650) An earlier related article, [Light may have slowed down](http://www.newscientist.com/news/news.jsp?id=ns99991158) ---
**Author:** ![DarrenS](https://avatars.discourse-cdn.com/v4/letter/d/977dab/32.png) [@DarrenS](https://boards.straightdope.com/u/DarrenS)\ **Post date:** [June 1, 2003, 4:30pm UTC](https://boards.straightdope.com/t/does-e-really-equal-mc-squared/178937/3 "2003-06-01T16:30:21Z")
IIRC from Special Relativity, E = mc[sup]2[/sup] is a (good) approximation that neglects higher order terms. ---
**Author:** ![Fernmeldetruppe](https://avatars.discourse-cdn.com/v4/letter/f/e99b99/32.png) [@Fernmeldetruppe](https://boards.straightdope.com/u/Fernmeldetruppe)\ **Post date:** [June 1, 2003, 5:30pm UTC](https://boards.straightdope.com/t/does-e-really-equal-mc-squared/178937/4 "2003-06-01T17:30:25Z")
There have been a lot of articles about this within the last year. Almost all trajectory calculations are still done using classical physics anyway, so I don’t think modifying relativistic physics will make much a difference today. Here’s a lay article: [http://www.cnn.com/2002/TECH/space/06/04/einstein.wrong/](http://www.cnn.com/2002/TECH/space/06/04/einstein.wrong/) And a JPL press release from a year ago: [http://www.jpl.nasa.gov/releases/2002/release\_2002\_123.html](http://www.jpl.nasa.gov/releases/2002/release_2002_123.html) A pro-“special relativity is not completely correct” paper: [http://wbabin.hypermart.net/paper/jr/joseph.htm](http://wbabin.hypermart.net/paper/jr/joseph.htm) ---
**Author:** ![SRVick](https://avatars.discourse-cdn.com/v4/letter/s/e36b37/32.png) [@SRVick](https://boards.straightdope.com/u/SRVick)\ **Post date:** [June 1, 2003, 6:08pm UTC](https://boards.straightdope.com/t/does-e-really-equal-mc-squared/178937/5 "2003-06-01T18:08:11Z")
In the May 26, 2003 issue of _U.S. News and World Report_, they cover this in “Taking a Shot at Einstein.” Basically, one of the problems is that _c_ is not necessarily constant. Here’s the link to the article, which unfortunately is not available online for free. [Taking a Shot at Einstein](http://www.usnews.com/usnews/issue/archive/030526/20030526040398_brief.php) ---
**Author:** ![Apollon](https://avatars.discourse-cdn.com/v4/letter/a/e47774/32.png) [@Apollon](https://boards.straightdope.com/u/Apollon)\ **Post date:** [June 1, 2003, 8:18pm UTC](https://boards.straightdope.com/t/does-e-really-equal-mc-squared/178937/6 "2003-06-01T20:18:05Z")
> [@](#): > > \*Originally posted by DarrenS \* > \*\*IIRC from Special Relativity, E = mc[sup]2[/sup] is a (good) approximation that neglects higher order terms. \*\* I have heard similar things of many formulae. I.e. that they are actually incorrect, but that they are still so precise that the difference does not matter. Why is that? Is it just a coincidence or does it actually mean anything? ---
**Author:** ![3\_14159265358979323846](https://avatars.discourse-cdn.com/v4/letter/3/eada6e/32.png) [@3\_14159265358979323846](https://boards.straightdope.com/u/3_14159265358979323846)\ **Post date:** [June 1, 2003, 10:54pm UTC](https://boards.straightdope.com/t/does-e-really-equal-mc-squared/178937/7 "2003-06-01T22:54:01Z")
[nitpick] E[sup]2[/sup] = m[sup]2[/sup]c[sup]4[/sup] + p[sup]2[/sup]c[sup]2[/sup] which simplifies to E=mc[sup]2[/sup] for the case where momentum, p, equals 0 (that is, a particle at rest). [/nitpick] ---
**Author:** ![Meatros](https://avatars.discourse-cdn.com/v4/letter/m/b4bc9f/32.png) [@Meatros](https://boards.straightdope.com/u/Meatros)\ **Post date:** [June 1, 2003, 10:58pm UTC](https://boards.straightdope.com/t/does-e-really-equal-mc-squared/178937/8 "2003-06-01T22:58:54Z")
Well [this person](http://www.setterfield.org/MassandEnergy.htm#anchor16006681) seems to want to rewrite the speed of light and a host of other things in order to get a young earth. Debating with his wife about the matter actually leads one to migranes… ---
**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\ **Post date:** [June 2, 2003, 2:13am UTC](https://boards.straightdope.com/t/does-e-really-equal-mc-squared/178937/9 "2003-06-02T02:13:08Z")
The equation that Pi gives also explains how to show energy when rest mass = 0, as is the case for photons. ---
**Author:** ![drhess](https://avatars.discourse-cdn.com/v4/letter/d/94ad74/32.png) [@drhess](https://boards.straightdope.com/u/drhess)\ **Post date:** [June 2, 2003, 2:58am UTC](https://boards.straightdope.com/t/does-e-really-equal-mc-squared/178937/10 "2003-06-02T02:58:13Z")
Hmm, wouldn’t that then be and E of zero, if m and p are both zero? What is p measured in? For that matter, what are they all measured in? Was this Enstien’s equation? ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [June 2, 2003, 3:06am UTC](https://boards.straightdope.com/t/does-e-really-equal-mc-squared/178937/11 "2003-06-02T03:06:55Z")
> [@](#): > > \*Originally posted by drhess \* > \*\*Hmm, wouldn’t that then be and E of zero, if m and p are both zero? > > What is p measured in? For that matter, what are they all measured in? Was this Enstien’s equation? \*\* They can be measured in any applicable units. In the mks system of SI units, mass (m) is in kilograms, the speed of light in a vacuum © is in meters/second, momentum § is in kilogram-meter/seconds and energy is in joules. AFAIK, m and p cannot simultaneously be zero. Butr if they can be, then, yes E would be zero too.