Physicists extend special relativity | Hacker News Reader

Physicists extend special relativity

phys.org

61 pointssoofy19 comments

Don't editorialize the title. The title of the article is "Physicists extend special relativity beyond the speed of light"

Several comments here are reminding me of general objections to PhysOrg as a source. As I recall, PhysOrg appears to have been banned as a site to submit from by Reddit. Users here on HN think there are better sites to submit from.

Comments about PhysOrg:

http://news.ycombinator.com/item?id=3077869

"Yes Physorg definitely has some of the worst articles on the internet."

http://news.ycombinator.com/item?id=3198249

"Straight from the European Space Agency, cutting out the physorg blogspam:

http://www.spacetelescope.org/news/heic1116/ (press release),

http://www.spacetelescope.org/videos/heic1116a/ (video),

http://www.spacetelescope.org/static/archives/releases/scien... (paper).

"PhysOrg: just say no."

http://news.ycombinator.com/item?id=3611888

"The physorg article summary is wrong, I think."

http://news.ycombinator.com/item?id=4108857

"Phys.org is vacuous and often flat wrong."

I also gave link to the original article. PhysOrg also gives link to the original article and cites a few other sources. I thought in this particular cases it was fine as an overview article.

Could you point to alternatives?

I read phys.org since it has a useable mobile interface, which is a lot cleaner than the somewhat cluttered main page. Reading news by categories is also a bonus, I especially like the Other Sciences category.

I know of eurekalert.org, but since they have no mobile site that's a no go.

Also, I think of them less as blogspam than as a news aggregator. I can't read all the direct press releases, so having the info all in one place and categorized is nice.

..I was under the impression that special relativity only forbade accelerating to the speed of light - particles that always traveled FTL (i.e. tachyons) were explicitly fine.

So.. what have they added with this work, exactly? IDGI.

That was my understanding too. Although its worth noting that the existence of Tachyons is entirely speculative.

Tachyons have complex mass, for one thing. The authors described the way to move between frames of reference of superluminal particles, so that they (particles) seem to have real finite physical properties. At least that's my understanding.

There are two different concepts of tachyons: Quantum fields with imaginary mass and faster-than-light particles.

Tachyonic fields still (anti)commute at space-like separation, which preserves causality. Such fields are maximally unstable and do not permit a particle picture. They are used to describe spontaneous symmetry breaking.

Tachyonic particles are a concept from special relativity. While one can also attribute an imaginary mass to such particles, this basically encodes a sign convention. These theoretical particles exhibit some perculiar properties (zero-energy particles which travel at infinite velocity and finite momentum, different observers will disagree on emitter and absorber - in fact, during a tachyonic interaction, both endpoints may claim to be emitter or absorber in their respective rest frames depending on their relative motion, ...). According to Recami[1], no causal paradoxa occur.

[1] http://dinamico2.unibg.it/recami/erasmo%20docs/SomeRecentSCI...

Quote from original paper: "In this highly controversial topic, our particular purpose is not to enter into the merits of existing theories, but rather to present a succinct and carefully reasoned account of a new aspect of Einstein's theory of special relativity, which properly allows for faster than light motion." http://bit.ly/RswJIr

I wish the full paper were available.

Stepping into general relativity, there's been a fair amount of work lately on Alcubierre's warp drive idea. The original required enormous amounts of negative mass and was infeasible in other ways, but more recent papers have modified it in ways that almost sound workable. Now a guy at NASA named Harold White is trying an experiment. (Google turns up plenty of articles.)

Not directly related: experiments continue on Woodward's Mach effect idea.

> I have a feeling the world will change in some dramatic way as we move through the speed of light. All sorts of things could happen. Time and space could interchange.

Penrose diagrams, light cones and scenarios like approaching a black hole event horizon help a lot on gathering what he means here.

Seems like an interesting article, sad that it is behind a paywall.

Apologies. Did you mean this? http://rspa.royalsocietypublishing.org/content/early/2012/09...

The article on phys.org is a summary of a paper published in Proc Royal Soc, the abstract for which is at [1]. The full paper is paywalled, and I believe that this is what @_of is referring to. Unfortunately there doesn't seem to be a preprint on ArXive.

Edit: All articles since November 2010 seem to be paywalled.

[1] http://rspa.royalsocietypublishing.org/content/early/2012/09...

Well the answer is obvious. Just make light go faster.

I've giv'n her all she's got, an' I canna give her no more.

So is this just saying that a particle traveling at .75 c will appear to be moving at 1.5 c to another particle moving towards it at .75 c? If so then duh?

> So is this just saying that a particle traveling at .75 c will appear to be moving at 1.5 c to another particle moving towards it at .75 c? If so then duh?

The real DUH is that it doesn't. A particle that is moving at .75c towards an observer going at it at .75c would appear to move at .96c. Velocities cannot be composited like that when you are moving really fast.

No.

If: V(a)=0.75c (relative to observer at (c)) and V(b)=0.75c (relative to observer at (c))

and (a) and (b) appear to be on parallel and oppositely signed vectors from (c)'s vantage point, the observed velocity of (b) @ (a), or (a) @ (b) will not equal 1.5c.

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