Beta

×

Welcome to the Slashdot Beta site -- learn more here. Use the link in the footer or click here to return to the Classic version of Slashdot.

Thank you!

Before you choose to head back to the Classic look of the site, we'd appreciate it if you share your thoughts on the Beta; your feedback is what drives our ongoing development.

Beta is different and we value you taking the time to try it out. Please take a look at the changes we've made in Beta and  learn more about it. Thanks for reading, and for making the site better!

Most Distant Galaxy Gives Clues to Early Universe

samzenpus posted more than 7 years ago | from the in-the-beginning dept.

104

NinjaT writes "From CNN, 'Scientists said on Wednesday that they have found the most distant galaxy yet, nearly 13 billion light-years away, in a discovery that could help explain how stars were formed at the dawn of time. The galaxy, named IOK-1, is so far away that the light waves that reached Earth depict it as the system of stars existed shortly after the Big Bang created the universe 13.66 billion years ago. That period, known to astronomers as the Dark Ages, saw the formation of the first stars and galaxies from elementary particles. Scientists had been unable to directly observe that time period until now.'"

cancel ×

104 comments

Sorry! There are no comments related to the filter you selected.

What I find difficult to understand (2, Interesting)

BadAnalogyGuy (945258) | more than 7 years ago | (#16102489)

This is offtopic, so it'll probably be marked down as such.

I was thinking about matter and how it was created and what we have here on earth.

The sun is made up of mostly hydrogen, through nuclear fusion, these hydrogen atoms smash into each other and bind into helium. The helium, being heavier than the hydrogen sinks to the center of the sun (or somewhere in there). As the sun uses up its hydrogen fuel, it slowly changes itself into a helium-based star.

Since we are made of stardust, where do the elements above helium come from? Did an iron star go super-nova and scatter peta-tons of iron atoms that then settled into spheres and became our earth? Carbon stars? Every element has to come from somewhere, and theoretically it needs to come from stars or stardust in order to exist at these low energies.

Where are these higher-element stars?

Re:What I find difficult to understand (4, Informative)

Oizoken (562241) | more than 7 years ago | (#16102511)

I think this will answer your questions:

http://en.wikipedia.org/wiki/Star#Massive_stars [wikipedia.org]

Re:What I find difficult to understand (1)

BadAnalogyGuy (945258) | more than 7 years ago | (#16102526)

Cool. That does answer my question. How do the elements above 26 get formed?

Re:What I find difficult to understand (3, Informative)

$RANDOMLUSER (804576) | more than 7 years ago | (#16102721)

That's here [wikipedia.org] .

Re:What I find difficult to understand (1)

linzeal (197905) | more than 7 years ago | (#16105196)

and here [ukaff.ac.uk] . This is one of my astrophysics textbooks [amazon.com] . Unfortunately, it is not in print anymore.

Re:What I find difficult to understand (1)

Tired and Emotional (750842) | more than 7 years ago | (#16107793)

http://en.wikipedia.org/wiki/Silicon_burning_proce ss [wikipedia.org] This article answers the particular question of creation of heavy elements.

Essentially, simplifying somewhat, everything up to Iron gets created inside stars. The heavier elements (than iron) get created in end of life stellar events.

Simplifications here are that some elements get created inside the star in the last few days to hours of its life rather than over long periods of time and some heavier than iron but unstable elements get created before the final cataclysm.

BTW, how does the postulated existence of dark matter affect stellar evolution? I have not been able to find anything on the web on that. It should mean stars have less hydrogen than classically calculated and therefore die faster - but what else and why is this not a problem with the dark matter hypothesis?

Re:What I find difficult to understand (1)

Alsee (515537) | more than 7 years ago | (#16111829)

BTW, how does the postulated existence of dark matter affect stellar evolution? ...why is this not a problem with the dark matter hypothesis?

Because in any meaningful sense, quantity of dark matter inside a star is zero.

Let me clarify what I mean by "zero". By my quick estimate about .000000000000000000005% of the mass inside the sun would be dark matter and the remaining 99.999999999999999999995% would be normal matter.

Why? To the extent dark matter is gravitationally attracted to a star, it just passes right through without interacting. The gravitational speed it picks up by falling inwards just kicks it right out the other side. So dark matter does not meaningfully collect inside a star. The amount of dark matter inside a star is the same as the interstellar density of dark matter.

Now consider the density of a star verses the general density of dark matter. Dark matter makes up about 90% of all mass, so for each star there is nine times as much dark matter. But that star is a tiny blob a few hundred thousand miles across. Very dense - something like 1.4 trillion kilograms per cubic kilometer inside the sun. Now consider nine times as much dark matter... not just spread across the entire volume of the solar system... but spread across a sphere several light years in diameter. It works out to about one microgram of dark matter per cubic kilometer of volume.

It's quite possible I got a decimal point wrong somewhere in my calculations. I didn't work very hard on it or double check anytghing. However even if I was off by a factor of a thousand cubed or more, it makes no difference. Even if I were off by a factor of million cubed (which I'm not), it would still mean less than one one-hundreth of one percent of the mass in the sun would be dark matter. Still zero for all practical purposes.

-

Re:What I find difficult to understand (0)

Anonymous Coward | more than 7 years ago | (#16105687)

did anyone else find it amusing to have something called a "balmer line" assosiated with massive explosions?

Re:What I find difficult to understand (1)

Lijemo (740145) | more than 7 years ago | (#16106000)

You're question's already been answered by others, but I just wanted to add a tangental thought.

In 1056, there was a supernova bright enough and close enough that it was visible in the daytime sky. This was also a time when alchemists were still trying to learn how to turn lead into gold.

I wonder how many alchemists saw the "new star"-- not realizing that they were witnessing the very transformation they were seeking: since lead CAN be changed into gold-- it just requires (much, much) higher temperatures and pressures than the alchemists were able to reproduce in the lab.

Re:What I find difficult to understand (1)

$RANDOMLUSER (804576) | more than 7 years ago | (#16109933)

The accepted date is probably(July 4), certainly(1054) [wikipedia.org] , and the remnant can still be seen: the Crab Nebula [wikipedia.org] .

And no, element 82: lead [wikipedia.org] is actually heavier than element 79: gold [wikipedia.org] , so you would have to remove protons and neutrons.

But thanks for playing, we have a lovely parting gift...

PS:
your == belonging to you
you're == "you are"

Re:What I find difficult to understand (1)

Lijemo (740145) | more than 7 years ago | (#16110097)

Well, if I measured intelligence in terms of snark, then I'd be forced to bow to your superior intellect.

However, it would seem that some sources disagree with you (search for "gold" on these pages):

  • http://www.astrosociety.org/education/publicatio ns/tnl/08/08.html
  • http://www.pbs.org/wgbh/nova/origins/univ-nf.htm l
  • http://www.newton.dep.anl.gov/askasci/chem03/che m03691.htm

I am not an astrophysisist, so it's possible there is more recent information I'm unaware of that makes this assertation out of date. But it's what I was taught, and there are still sources around to support it, so if you are going to declare it wrong, a source would be helpful.

You are correct abuot my spelling errors. It's true that I was focued more on getting back to my real job quickly, rahter than proofreading for typos and grammer.

Re:What I find difficult to understand (2, Funny)

$RANDOMLUSER (804576) | more than 7 years ago | (#16111978)

I'm sorry, which one of those links said you could turn lead into gold???

Re:What I find difficult to understand (1)

MichaelSmith (789609) | more than 7 years ago | (#16102519)

Where are these higher-element stars?

IANAA (I am not an astophysicist) but supernova explosions create most of the heavy elements. There should be a good writeup on wikipedia.

Re:What I find difficult to understand (3, Funny)

Anonymous Coward | more than 7 years ago | (#16102642)

Please, don't use acronyms ending in AA around here. You're scaring the nerds.

Re:What I find difficult to understand (2, Informative)

KitsuneSoftware (999119) | more than 7 years ago | (#16102535)

Helium fuses into heavier elements, in a cycle which ultimately leads to carbon for Sun-mass stars, and ultimately to iron for heavier stars. IIRC, elements heavier than iron are only produced in significant quantities by supernova. Such heavy stars are all over the place, and are fairly easy to see because they are so bright; on the other hand, they are also fairly short-lived, lasting only a few million years instead of about ten billion like our sun or the hundred-billion odd years predicted for stars much lighter than the sun.

Re:What I find difficult to understand (1)

Opportunist (166417) | more than 7 years ago | (#16102536)

In a nutshell, everything up to iron can be done with fusion. Up until iron, you gain more energy out of fusion of cores than it costs to fuse them. Even though it's very, very little when you fuse iron, and only VERY heavy stars get there at all. Fortunately, heavy stars are also those that burn through their fuel the fastest (i.e. they are done after a few million years).

When iron is done, it's over. The machinery stops. Suddenly. I.e. the pressure from insides stops, the star collapses VERY fast (within milliseconds) which causes the outer layers to crash onto this rather dense iron ball. This in turn results in a nova, where heavier cores are produced.

Re:What I find difficult to understand (1)

BadAnalogyGuy (945258) | more than 7 years ago | (#16102540)

So a nova is like a last-gasp fusion step as the star blows itself apart?

Re:What I find difficult to understand (1)

MichaelSmith (789609) | more than 7 years ago | (#16102556)

So a nova is like a last-gasp fusion step as the star blows itself apart?

Actually I think he meant supernova. Some stars can go nova many times without ending their lives.

Re:What I find difficult to understand (1)

Opportunist (166417) | more than 7 years ago | (#16102576)

Yes. Sorry, matter of a really bad translation. Shouldn't post before I had my first coffee.

Re:What I find difficult to understand (4, Informative)

FirienFirien (857374) | more than 7 years ago | (#16102552)

Fusion reactions in stars will combine everything up to iron. Hydrogen - being the most abundant - will be the major fusion to form Helium; there's so much of it that that's pretty much all you'll see. However as the amount of He goes up, it'll become combined with H and other He to form Li and Be, and so on - all the way up to iron. Past that the energy of fusion required is simply too high, and with a normal star you'll never see anything with a higher atomic mass. Your iron star going supernova is a little misleading, as the supernova star won't be made of iron - at that mass it'll very likely have a good amount of iron compared to other stars, but in general the greatest part of its mass will still be H and He. Only from that supernova energy, (and the occasional cosmic ray collision, but I think those are negligible in comparison to the amount of matter in a supernova) do you get the energy required to fuse higher elements.

So - the elements above Helium come from normal fusion in a star; they don't have their own phases, everything just bumps into everything else at once. All your elements above iron have a greater fission energy than fusion energy, and with the amount of trigger radiation inside a star they don't generally last long. When they get ejected from a supernova, there's less to trigger them, so they stay stable for longer; that's why we have everything higher than iron, though even on earth they're in relatively minute quantities.

One last thing to point out is that your question about carbon seems odd - bear in mind that a carbon atom only has an atomic mass of 12, while iron has an atomic mass of 56. Carbon is relatively abundant compared to iron. To hazard a guess, if you laid the periodic table in a straight line you would probably see an approximately logarithmic amount of each element, up to iron and beyond; it'll be a little complicated since some elements are more likely to decay back to lighter elements faster than others, but that's the gist.

Disclaimer: this is all out of what I remember from courses; it may not be 100% accurate, though I believe it should clarify things enough.

Abundance of elements (5, Informative)

Roy Ward (14216) | more than 7 years ago | (#16102607)

> To hazard a guess, if you laid the periodic table in a straight line you would probably see an approximately logarithmic amount of each element, up to iron and beyond; it'll be a little complicated since some elements are more likely to decay back to lighter elements faster than others, but that's the gist.

Not quite right:

http://www.seafriends.org.nz/oceano/abund.htm [seafriends.org.nz]

Some elements (Oxygen, Carbon, Neon) seem to form more easily than Lithium, Beryllium etc.

Re:Abundance of elements (1)

FirienFirien (857374) | more than 7 years ago | (#16103523)

I was surprised by this so have looked into it; a Wikipedia page seems to explain why the lithium goes, and implies that most of the Be formed is 8Be which degenerates back to two 4He. Must have been asleep in that lecture or something...

Re:Abundance of elements (1)

FirienFirien (857374) | more than 7 years ago | (#16103547)

Er, damn, it would probably help to include the link [wikipedia.org] .

Re:What I find difficult to understand (-1, Troll)

allfunandgames (1000948) | more than 7 years ago | (#16103236)

What I find difficult to understand is how you know all of this? Were you there? If not, then your argument is really just some kind of religion based on a set of beliefs that some guy thought up after some extrapolation from other OBSERVABLE phenomena commonly know as variations in species. I have a question: If evolution were true, how do you explain that some of the planets and moons are rotating backwards? How do you explain that some of the moons are going backwards around their planets?

Re:What I find difficult to understand (1)

hutchy (31659) | more than 7 years ago | (#16103401)

I find you to be incredibly dense. You must be from another planetary system

Evolution and planetary motion (1)

Alien54 (180860) | more than 7 years ago | (#16103916)

If evolution were true, how do you explain that some of the planets and moons are rotating backwards? How do you explain that some of the moons are going backwards around their planets?

Simple troll. Evolution is impacted by planetary motions, such as speed of rotation, distance from stars, etc. but does not grok the concept of 'backwards motion' - 'Backwards Motion' is an illusion based on conventions of human perception. Planets in motion around a star are seen as moving clockwise or counter clockwise depending purely on the direction that you use to approach the star system in the first place. Living things on the planetary surface do not care how you enter the star system, except, perhaps, as a matter of self defense.

Re:What I find difficult to understand (1)

MBGMorden (803437) | more than 7 years ago | (#16104192)

I have a question: If evolution were true, how do you explain that some of the planets and moons are rotating backwards? How do you explain that some of the moons are going backwards around their planets?

Backwards rotating planets (such as Venus) are the result of collisions in the early solar system. Basically something hit it (hard) and spun it around. The same applies to Uranus (which rotates on it's side, though not backwards). A moon that rotates opposite of it's parent planet was likely a captured object rather than something that formed with the planet.

I'm also wondering what in the world this has to do with evolution :?.

Re:What I find difficult to understand (1)

allfunandgames (1000948) | more than 7 years ago | (#16108142)

Tell me something guys: Where did all the matter in the Universe come from? Where did the energy come from to create it? Have you heard of thermodynamics? How about a phenomenon known as the conservation of angular momentum? Look guys, the earth is slowing down ok? That means it was going faster. So, millions of years doesn't work let alone billions. Centrifugal force anyone? You do the math but it really screws up the so-called theory of evolution. We came from and oscillating singularity? We came from nothing? Sounds way too far-fetched to me. It also diminishes my value as a human being. There is simply no evidence what-so-ever for evolution. Show me some evidence. Show me something. Or, stop calling me a troll. I don't think I deserve to be personally attacked because of my opinion. I don't belive evolution is part of real scientific work. It is speculation at best. In addition, I think that it's a worthless excersise. It has no benifit--even if it were true.

Re:What I find difficult to understand (1)

Rakshasa Taisab (244699) | more than 7 years ago | (#16102729)

Iron is the last step in fusion, and stars that go supernova do build up 1.2 solar masses of the stuff. Except when they implode, everything is turned into neutrons. So, fusion as a positive energy reaction doesn't happen above iron, and supernova's only contribution would be what happens to be outside of its core.

Re:What I find difficult to understand (1)

Ferretman (224859) | more than 7 years ago | (#16103014)

Fundamentally the universe isn't old enough yet to have any (or many...I guess somewhere out there might be one or two) higher-element stars. From the stars' point of view most heavier elements are "trash" in one form or another...if they're made largely by previous stars fusion process and/or when they supernova you can't have any significant amount of heavier elements until a first generation star burns through its fuel, blows up, forms a second-gen star, IT blows up, etc.

I think I read that right now the universe is mostly second and third generation stars (including our sun). Got a ways to go yet before there are enough heavier elements out there to make a significant difference.

Ferretman

Re:What I find difficult to understand (0)

Anonymous Coward | more than 7 years ago | (#16105396)

No, it is a matter of the iron phase being very short duration, not rare or needing previous stars to manufacture their composition. High element stars make their own high elements and do not need supernovae to have made them... in fact if they were made of higher elements from the get go they would not have been stars in the first place due to the fusion reactions not supplying any energy to repel gravity.

No bad analogy? (1)

rbarreira (836272) | more than 7 years ago | (#16103019)

BadAnalogyGuy, I'm highly dissapointed that your post doesn't contain a bad analogy. Damn, not even any analogy! I hereby express my desire to see a bad analogy in each of your future posts (and I know you've done it in the past :P).

Re:No bad analogy? (1)

Bad Car Analogy (1001944) | more than 7 years ago | (#16105766)

Why're you surprised? BadAnalogyGuy's posts are like getting a used car, they may not live up to expectations. It'd be like if you go to a used car lot called "Honest Bob's", and then are surprised that you get a slimy deal.

Re:No bad analogy? (0)

Anonymous Coward | more than 7 years ago | (#16105869)

Whoa, there are over a million user ids? I wonder who got 1000000.

Re:No bad analogy? (0)

Anonymous Coward | more than 7 years ago | (#16105926)

This guy [slashdot.org]

You can search for slashdot ids like this [google.com] (don't ask me why the second * is needed, I think it's very strange too!).

Re:What I find difficult to understand (1)

MBGMorden (803437) | more than 7 years ago | (#16104138)

I'm not an astronomer either (I do read a good bit about it though), but yes, the heavy elements that make us and all the "heavy" planets up were formed in supernova explosions.

It's also just a guess, but overly massive stars and accompanying supernovas would have have been much more common in the early universe. Combine that with a greatly reduced lifespan for these massive stars (last I heard the really big ones might have a life cycle measure by a couple dozen millions of years, rather than billions), and it's not hard to imagine a lot of heavy elements being blasted all over the place in the "good ol' days" of the universe.

The galaxy, named IOK-1 (2, Funny)

Anonymous Coward | more than 7 years ago | (#16102493)

Well I think that name is A-OK.

Re:The galaxy, named IOK-1 (1)

d_54321 (446966) | more than 7 years ago | (#16103121)

It's all explained in my forthcoming intergalactic self-help book "IOK, You OK".

I know cosmology is an inexact science but (2, Funny)

Silver Sloth (770927) | more than 7 years ago | (#16102497)

From TFA
The scientists found another object similar to IOK-1, but could not say if it was a distant galaxy or something else such as a black hole.
  • Galaxy - lots of stars spread over a vast area - low average density
  • Black hole - one star compressed into a relatively small area - high average density
Easily confused then.

Re:I know cosmology is an inexact science but (4, Informative)

HuguesT (84078) | more than 7 years ago | (#16102534)

From very far away they are not so easy to tell apart. Essentially these are two objects that emit extremely red-shifted light.

Re:I know cosmology is an inexact science but (1)

clickclickdrone (964164) | more than 7 years ago | (#16102774)

>Essentially these are two objects that emit extremely red-shifted light.
So it's very, very old and emits red light? Sounds like they've just spotted the first ever brothel.

Re:I know cosmology is an inexact science but (1)

HuguesT (84078) | more than 7 years ago | (#16108293)

Hello, the straight-type, no fun answer is that red-shifted doesn't mean red. Extremely red-shifted gamma rays might be X-rays for instance.

Re:I know cosmology is an inexact science but (1)

MichaelSmith (789609) | more than 7 years ago | (#16102543)

Easily confused then.

TFA doesn't say but I suspect they are not actually looking at pictures of the object. More likely a spectrum. Perhaps the acretion disk of a black hole has a similar spectrum to a young galaxy when using these instruments.

Re:I know cosmology is an inexact science but (1)

Opportunist (166417) | more than 7 years ago | (#16102544)

Well, considering it's really far away (I mean, 13 bil LJ ain't just 'round the corner), I can well see that it's hard to discriminate between a galaxy and a black hole. From that distance, both are just huge things in space with lots of (singular or combined) gravity.

Re:I know cosmology is an inexact science but (1)

tygerstripes (832644) | more than 7 years ago | (#16102545)

"The thing about black-holes is, they're black. And thing about space - the colour of space; your basic space colour - is it's black.

"So 'ow you s'posed to see 'em?"

</geek>

Re:I know cosmology is an inexact science but (1)

legoburner (702695) | more than 7 years ago | (#16102722)

Ahhh Red Dwarf. Up until season 7 was perhaps the greatest Sci-fi comedy ever. (Though futurama might have overtaken it now). If you have not yet seen it then do yourself a favour and watch it [thepiratebay.org] . (but bare in mind it dates back to 1988).

Re:I know cosmology is an inexact science but (1)

Aladrin (926209) | more than 7 years ago | (#16103063)

It's 'bear in mind' but other than that, spot on. Absolutely hilarious. Don't get turned off by the first ep, though. It's a tad slow at the start.

Not quite science reporting (3, Insightful)

svunt (916464) | more than 7 years ago | (#16102554)

Whoever wrote up the Reuters summary that CNN are running must've been filling in for the science reporter.


I was well impressed by this guy confirming the Big Bang, and its precise timing. Correct me if I'm wrong, but I thought that the exact origin of the universe and its date were still debated issues. We've changed the age of the universe enough times that you'd want to be wary about putting two decimal places in your statement.


Disclaimer: I'm not a creationist or one of the "evolution's a theory, not a fact" crowd, I just like my science to come appropriately qualified.

Re:Not quite science reporting (1)

MichaelSmith (789609) | more than 7 years ago | (#16102565)

I thought this was a bit bold:

Either way, it shows that the universe changed substantially in the 60 million years that separate IOK-1 and the next oldest galaxies to be observed on Earth, the astronomers said.

Considering that we are talking about the first billion years after the big bang.

Re:Not quite science reporting (2, Insightful)

svunt (916464) | more than 7 years ago | (#16102580)

Yep, all in all, whoever wrote this really lacks any understanding of the scientific process. I'm sure the astronomers who made the find would've been a little bit more careful about their claims than the article suggests.

Re:Not quite science reporting (1)

aadvancedGIR (959466) | more than 7 years ago | (#16102763)

The headline is so lame that I bet it was submitted by Roland when opening it.

Re:Not quite science reporting (0)

Anonymous Coward | more than 7 years ago | (#16103191)

'Scientists make shocking discovery that theory X, already well supported, in case of being true has a most probable parameter range of between 13 and 17, as opposed to the previously thought 12 and 16. Discovery is also partially explainable by theory Y however, and does not infringe upon theory Z, both of which would refute theory X.'

Re:Not quite science reporting (1)

LordVader717 (888547) | more than 7 years ago | (#16103366)

Not so much anymore. Since WMAP [wikipedia.org] it has generally been accepted that 13.7 billion years is the best bet, with a few theories here and there that claim to give a more accurate date.

A long time ago, (2, Funny)

psicop (229507) | more than 7 years ago | (#16102749)

in a galaxy, far, far away...

I finally made my first post, it's just now arriving from IOK-1.

--Not enough Bothans died to bring you this message.

Question for the cosmologists (0)

Anonymous Coward | more than 7 years ago | (#16102826)

If there was a Big Bang from which all matter arose... and light is the fastest thing in the Universe... how is it that we got to this point before the light from this ultra-early galaxy got here?

Re:Question for the cosmologists (2, Informative)

donaggie03 (769758) | more than 7 years ago | (#16102845)

I believe the short answer to that question is that you have to distinguish between objects moving in space and space itself moving. The speed of light is the limit that objects are able to move through space. Space itself has no such limitation and can expand at a greater pace than the speed of light.

Re:Question for the cosmologists (0)

Anonymous Coward | more than 7 years ago | (#16102997)

The is no proof that light is the fastest objects can move, only that we dont think we have seen it.

Also, and more to the point of my post, if the universe was expanding faster then light, and objects are "tied" to the universe (the universe moves, so do objects), then wouldent the objects move apart faster then light, meaning they are moving faster then light, which is either impossible by some theories, impracticle if it was possible, or we can move faster then light without much side effects.

Re:Question for the cosmologists (0)

Anonymous Coward | more than 7 years ago | (#16103016)

Depends what you mean by "proof". All evidence we have at the macroscopic scale is consistent with Relativity, which says objects cannot travel at the speed of light. Also, the Universe does not "move", according to BB Theory, space just "expands". Hence, objects do not accelerate or decelerate relative to one another, so Relativity isn't violated.

Re:Question for the cosmologists (0)

Anonymous Coward | more than 7 years ago | (#16106789)

How conveeeeeenient.

Re:Question for the cosmologists (0)

x2A (858210) | more than 7 years ago | (#16103436)

If you travel at 80% the speed of light away from an object travelling 80% of the speed of light in the opposite direction, the distance between you is growing at 160% speed of light, so your speed relative to the other object is faster than the speed of light.

Re:Question for the cosmologists (1)

boyfaceddog (788041) | more than 7 years ago | (#16103654)

Thank You! I know understand relativity.

Re:Question for the cosmologists (2, Informative)

brunascle (994197) | more than 7 years ago | (#16103762)

i dont think that's right. i dont know the math exactly, but i dont think 2 objects can be moving apart faster than the speed of light (unless space itself is expanding).

there's no difference between 2 objects moving in opposite directions and only 1 moving and the other standing still. if that were true, it would be the same as if one object stood still and the other moved at 160% the speed of light, which is impossible.

remember, as you move, time itself changes (relative to whatever object youre moving relative to). the faster you move, the slower time gets. that's the reason you cant break the speed of light, because at that speed time stands still.

relativity! (1)

kwikrick (755625) | more than 7 years ago | (#16103872)

No no no no! Given object A is moving away from you in one direction at light speed and object B is moving away from you in the other direction at the speed of light, then the speed of A relative to B is still the speed of light. And that is because time passes slower for objects near or at light speed. Don't ask me why, but that's how it works.

Re:Question for the cosmologists (0)

Anonymous Coward | more than 7 years ago | (#16105344)

Just adding the velocities works when the speeds are much less that the speed of light. But relativity says that the exact result for speeds u and v is

w = (u + v)/(1 + u*v/c^2)

which is close to u + v when u,v are much smaller than the speed of light. (Taken from this site [ucr.edu] .)

This gives about 97% the speed of light in your case.

There's a few good links if you just google [google.com] it.

Incidentally, things like this are part of the reason why I understand that I don't understand relativity.

Re:Question for the cosmologists (2, Informative)

qeveren (318805) | more than 7 years ago | (#16105529)

That's incorrect, since at these velocities Special Relativity takes over from Classical Mechanics.

The relative velocity between two objects (in the case of parallel or antiparallel velocities) is given by:

v(rel) = ( w - v ) / ( 1 - ( ( w * v ) / c^2 ) )

Which means two objects, travelling in opposite directions at 0.80c, will have a velocity relative to each other of 0.98c.

Re:Question for the cosmologists (1)

syntaxglitch (889367) | more than 7 years ago | (#16106098)

If you travel at 80% the speed of light away from an object travelling 80% of the speed of light in the opposite direction, the distance between you is growing at 160% speed of light, so your speed relative to the other object is faster than the speed of light.

Incorrect. In this circumstance, a "stationary" observer sees both travelling at .8c and thus could infer a relative velocity of 1.6c, and from your perspective the stationary observer would be travelling away at .8c, but the other object would be seen to be travelling away at about .98c. No, it doesn't seem to make sense, but yes this is how it works. The rules are different, however, when you're talking about the expansion of space, not actual velocity.

13 BILLION LYS! (0)

Anonymous Coward | more than 7 years ago | (#16102883)

The fact that we receive now this light means that the galaxy (or whatever) that sent it was then 13 BILLION LIGHT YEARS away from where we are right now.

Given that we cannot move faster than light, it means that the universe was not "substantially" smaller then. And this means that the "edges" of the universe expanded substantially faster than light during the fisrt billion of years. This of course asuming the universe is not closed over itself and this light has done at least one "orbit".

Whoah, I think I will stop here for the moment.

Re:13 BILLION LYS! (1)

Gotung (571984) | more than 7 years ago | (#16103704)

The light emitting from that galaxy is being emitted in all directions. No matter where we are in the universe or what time it is (unless some other object was blocking it) the light from that Galaxy has ALWAYS been shining on us. We just didn't notice it till now. Since this galaxy is obviously very far away, it can be assumed that the clump of matter we're riding on and the clump of matter that makes up that galaxy shot out of the Big Bang at very different angles. Since we are moving away from each other at a very fast rate, every moment that passes means that light emited from that galaxy takes longer to get here then the light emitted just before. We have essentially been getting a "slow motion" view of this galaxy since the beginning of time.

Re:13 BILLION LYS! (1)

popsicle67 (929681) | more than 7 years ago | (#16104635)

That is exactly what bothers me about all of this talk about fossil light. Everytime you read about a distant star there is always the statement"You are viewing light that has taken however many thousands or millions of years to be visible on earth". I wonder,Does that mean that if that star turns off right now for whatever reason that we won't know about it for those thousands or millions of years? I cannot fathom that the light would still be visible that long after the star quit eminating. I cannot believe that there wouldn't be some instance of simultaneity that would allow us to see the end of that star as it happened. A lot of coverage was given recently to a star going nova and being very polite about about extending it's death for a comprehensive view. It hit me then how funny it would be for everyone to assume that the event was years old only to have their own measurements prove that they were realtime witnesses. That is,of course,blasphemy, but then many geniuses of history were "blasphemes"

Re:13 BILLION LYS! (1)

qeveren (318805) | more than 7 years ago | (#16105604)

Since light travels at a finite speed, any changes in the appearance of an object are only going to become apparent when the light that left the object when it was changing finally reaches you.

If a new star suddenly 'turns on' 10000 light years away from us, we're not going to see it until its light reaches us, 10000 years later. If that star burns out, there'll still be 10000 years worth of light already travelling towards us from it, so in our sky it will continue to shine for those 10000 years. Everything we see of that star will be suffering from a 10000 year delay.

There is no aspect of simultaneity in the universe. It's all governed by the limitations of Special (and General) Relativity. If it were otherwise, all sorts of causal paradoxes would be springing up, and reality would make very little sense.

Re:13 BILLION LYS! (1)

gstoddart (321705) | more than 7 years ago | (#16107068)

If it were otherwise, all sorts of causal paradoxes would be springing up, and reality would make very little sense.

But ... reality already makes very little sense. ;-)

Re:13 BILLION LYS! (1)

popsicle67 (929681) | more than 7 years ago | (#16108217)

I would love to see the proof on that mathmatically. I have an itching feeling that one day we will find out that we have been operating under assumptions that are at least as asinine as the flat earth theory or the belief in the existance of any GOD

Re:13 BILLION LYS! (0)

Anonymous Coward | more than 7 years ago | (#16106841)

Wait - Thank you! You've just enabled me to intuitively grasp something.

The light from this galaxy has been shining on the Earth from the moment it formed, over 13 billion years ago... but the light we are seeing now is 13 billion years old. That's because of the relative velocity of our two galaxies, 660 million years of light (The time from the big bang to when the light we are currently seeing left the other galaxy) has been stretched out (redshifted) so much that it has taken 13 billion years to fall on Earth.

Distance Question (1)

astralbat (828541) | more than 7 years ago | (#16103141)

What doesn't make sense to me is how galaxies nearly 13 Billion light years away are determined to be nearly as old as the Universe. My intuition tells me that light that old would have already passed us by soon after the big bang happened?

Re:Distance Question (1)

LordVader717 (888547) | more than 7 years ago | (#16103466)

The Universe is about 78 billion lightyears accross. Although it doesn't seem to make sense, I think it is to do with relativity.
The oldest radiation that can reach us is from about 400 000 years after the big bang when atoms formed, which let light pass through and the universe became transparent.

Re:Distance Question (1)

brunascle (994197) | more than 7 years ago | (#16103485)

13.7 billion years is the best guess at the age of the universe now. that light arriving at us now is depicting the galaxies as they were 13 billion years ago, very close to the big bang.

i believe that around 380,000 years ago is the earliest we'll be able to observe, because before then, the universe was so hot that it was opaque, and no light escaped without being abosorbed by other particles.

Re:Distance Question (1)

brunascle (994197) | more than 7 years ago | (#16103504)

actually, i think because of the expansion of the universe, it was probably less than 13 billion years ago, but i'm not sure how much less.

Re:Distance Question (1)

x2A (858210) | more than 7 years ago | (#16103573)

"My intuition..."

oo you don't wanna be using a thing like that here! What you have to remember is that this galaxy we're viewing is in the same location that the big bang occured... and so are we. :-/

Re:Distance Question (0)

Anonymous Coward | more than 7 years ago | (#16103816)

In the moments just after the Big Bang the Universe underwent a period of incredibly rapid exponential expansion (much faster than the speed of light; we're referring to the expansion of space here not the movement of objects within it so this is fine). This expansion, called "inflation", effectively separated objects by large initial distances (and also set seed perturbations that led to useful things like galaxies). The Universe has been expanding ever since. Since it takes a finite time for light to propagate through the Universe and meanwhile the Universe expands, we are only now seeing the light from these distant galaxies. "The first light from much nearer galaxies did indeed pass us a long time ago (although neither we nor our Solar System was around to notice). Distance relates to history in the Universe because of the finite speed of light. The light from these earliest galaxies is indeed near to the earliest light we could see.

[IAAC]

What if... (1)

Drakin020 (980931) | more than 7 years ago | (#16103376)

There are galaxy's we can see that are further away...its just the light waves have not hit us yet cause they are infact so far away...who known we could witness the Big bang theroy at work from a galaxy farrrr away. /Christian

Re:What if... (0)

Anonymous Coward | more than 7 years ago | (#16103998)

Yes. This is completely correct. The only trouble is that what we use to see throughout the Universe is almost exclusively light (photons) and the Universe was opaque to light until about 300,000-400,000 years after the Big Bang. Thus our view is limited to this epoch and we can't see beyond. The cosmic microwave background that we see pervading space is exactly the last light from this time.

[IAAC]

Original article (1)

VincenzoRomano (881055) | more than 7 years ago | (#16103768)

The original article is, of course, here [naoj.org] .
I'd like to see science news announced here by quoting the original source rather than a news company.

Moo (1)

Chacham (981) | more than 7 years ago | (#16104835)

The galaxy, named IOK-1, is so far away that the light waves that reached Earth depict it as the system of stars existed shortly after the Big Bang created the universe 13.66 billion years ago.

Amazing how it is just taken as a fact.

Re:Moo (0)

Anonymous Coward | more than 7 years ago | (#16106693)

Not when you consider just how much these people have riding on that assumption; they pretty much have their necks stuck out so far they can see the thing without a radio telescope!

How long was this light travelling? (1)

CopaceticOpus (965603) | more than 7 years ago | (#16104957)

The article states the galaxy is 13 billion light years away. At first I read this as "the light took 13 billion years to reach us," but that doesn't make sense if you think about it. To get 13 billion light years away in a galaxy which is a mere 13.6 billion years old, each galaxy would need to be moving at nearly 0.48c. Assuming that the galaxies are moving in opposite directions at the same speed, this means that the light has been catching up to us at a rate of 0.52c since the time it left the other galaxy.

Here are two equations we can write, with T being the time the light travelled (years), and D being the distance between our galaxies at the time the light was emitted (light years).

A) T = D * 0.52
B) D + 0.96 * T = 13 billion

D + 0.96 * (D * 0.52) = 13 billion
D = 8.67 billion
T = 4.51 billion

So the light departed the other galaxy about 4.5 billion light years ago, when our galaxies were about 8.7 billion light years apart. I know I've made some big assumptions, but am I on the right track with this?

Re:How long was this light travelling? (1)

mmmmbeer (107215) | more than 7 years ago | (#16106846)

Sorry, but no. Remember that the fundamental given that underlies all relativity is that light moves at the same speed regardless of the motion of the observer. In other words, regardless of our relative movement, the speed of light must be c, not 0.52c. Therefore, this galaxy would have had to have been 13 billion light years away from us at the time the light left it and began travelling towards us. Of course, that's assuming relativity is correct, which is much less certain than many people believe.

Re:How long was this light travelling? (1)

wanerious (712877) | more than 7 years ago | (#16107008)

Therefore, this galaxy would have had to have been 13 billion light years away from us at the time the light left it and began travelling towards us.

This isn't right. The "13 billion ly" is an unfortunately inaccurate, and probably meaningless number. It typically comes from plugging the value of the *redshift* of the galaxy (what is actually observed) into a particular cosmological model or, more commonly and naively, into simple Doppler redshift formulae. The distance of the galaxy at the time of emission was much closer than 13 billion ly away, since the size of the observable universe then was around a factor of 10 smaller than it is now --- this scale factor is what is given by the redshift. That's why we (astronomers) don't typically give distances of "billions" of light years. For objects at cosmological distances, there is no "now" (we're not in their light-cone yet), so no real meaning to "distance". We usually just report the redshift (z).

Of course, that's assuming relativity is correct, which is much less certain than many people believe.

I'm intrigued by your offer and would like to subscribe to your newsletter.

Re:How long was this light travelling? (0)

mmmmbeer (107215) | more than 7 years ago | (#16107648)

The "13 billion ly" is an unfortunately inaccurate, and probably meaningless number.

I agree, but I didn't feel like taking on this assumption. I was simply stating that if something were indeed seen from 13 billion ly away, it would mean they were 13 billion ly away 13 billion years ago, when the light began travelling, as opposed to being 13 billion ly away right now. On the other hand, if the other galaxy is calculated to be 13 billion ly away now, it was much closer when the light we are now seeing had left it. I addressed the former possibility because it related to the parent post.

I'm intrigued by your offer and would like to subscribe to your newsletter.

Here's the short version: It is well known that relativity is flawed. There's a common demonstration used to introduce people to relativity: a ship, a planet, and a light exist in space. The light blinks in a regular pattern. The ship starts next to the planet and flies to the light and back at a relativistic speed. In the process, we see that the ship has experienced less time than the planet. I'm not explaining this here; I assume you are familiar. If not, there are demonstrations available on the web.

So, once that is shown, take it one step farther. Four ships in a line; two have blinking lights on them. The two without lights start next to each other, the other two are the same distance from them (on opposite sides) that the light was from the planet in the previous example. Each of the outer ships flies inward, while the other two fly outward in opposite directions; for simplicity, make the speed of each be half the speed of the ship in the previous example. When the outer and inner ships meet, they turn around and return to their original positions. So now you can see that by removing either of the outer ships, you have a model equivalent to the first example. Thus, each of the middle ships experiences less time than the other! Nothing in relativity can account for this contradiction (yet).

Relativity is wrong. We don't know the exact nature of what is wrong. Most of us, myself included, do not discount it altogether, but some do. Thus I say again, relativity is much less certain than many people believe.

Re:How long was this light travelling? (2, Informative)

wanerious (712877) | more than 7 years ago | (#16108701)

I agree, but I didn't feel like taking on this assumption. I was simply stating that if something were indeed seen from 13 billion ly away, it would mean they were 13 billion ly away 13 billion years ago, when the light began travelling, as opposed to being 13 billion ly away right now. On the other hand, if the other galaxy is calculated to be 13 billion ly away now, it was much closer when the light we are now seeing had left it. I addressed the former possibility because it related to the parent post.

I understand, and forgive me for pressing a point that you may not care about, but neither of the possibilities you outline above are correct: The statements (a) "The galaxy was 13 billion light years away when the light was emitted" and (b) "The galaxy is now 13 billion light years away" are both not only wrong, but meaningless. The expansion of the universe renders all such distance and time estimates subject to a particular cosmological model in which they are evaluated; and it's only the redshift number, indicating the scale factor of the expansion, that carries any real meaning.

Here's the short version: It is well known that relativity is flawed.

I'd assert that it is far from well-known. Among physicists, to my knowledge, there is no known thought experiment or demonstration that cannot be reconciled with special relativity. The usual suspect in such "paradoxes" is to wrongly assume some simultaneous measurements in two frames in relative motion.

There's a common demonstration used to introduce people to relativity: a ship, a planet, and a light exist in space. The light blinks in a regular pattern. The ship starts next to the planet and flies to the light and back at a relativistic speed. In the process, we see that the ship has experienced less time than the planet. I'm not explaining this here; I assume you are familiar. If not, there are demonstrations available on the web.

Nope, not familiar with that one so much. What's the purpose of the blinking light?

So, once that is shown, take it one step farther. Four ships in a line; two have blinking lights on them. The two without lights start next to each other, the other two are the same distance from them (on opposite sides) that the light was from the planet in the previous example. Each of the outer ships flies inward, while the other two fly outward in opposite directions; for simplicity, make the speed of each be half the speed of the ship in the previous example. When the outer and inner ships meet, they turn around and return to their original positions. So now you can see that by removing either of the outer ships, you have a model equivalent to the first example. Thus, each of the middle ships experiences less time than the other! Nothing in relativity can account for this contradiction (yet).

Are you certain? I'm having trouble diagramming the setup, but I'd be glad to look at some kind of picture to make it more clear.

Relativity is wrong. We don't know the exact nature of what is wrong. Most of us, myself included, do not discount it altogether, but some do. Thus I say again, relativity is much less certain than many people believe.

These people must not be physicists, or at least this ground-shaking refutation of special relativity has not gotten the publicity your bald assertion would seem to warrant. I'd be glad to believe you, but as a teacher of relativity, color me skeptical.

Re:How long was this light travelling? (0)

mmmmbeer (107215) | more than 7 years ago | (#16109235)

The statements (a) "The galaxy was 13 billion light years away when the light was emitted" and (b) "The galaxy is now 13 billion light years away" are both not only wrong, but meaningless.

If you're going to trivialize all values of distance to the point that they are meaningless, then you're a fool. It's certainly possible to say that variations in theoretical values (or entire cosmological models) could cause these values to be different, but the gist remains the same: the light left the other galaxy and travelled to the earth at the speed of light RELATIVE TO THE EARTH, and the relative speeds of the earth and the other galaxy are irrelevent. Yes, this is dependent on a particular cosmological model, but to refuse to accept any such model because there are competitors renders all of your statements meaningless. You might only care about red shift, but it means exactly jack to most people, thus we render it to distance (and often time) based on a model that seems most likely to fit.

Nope, not familiar with that one so much. What's the purpose of the blinking light?

And you claim to be a teacher of relativity? Ok, I'll assume for the moment that somehow that's true and yet you've never seen this basic thought experiment. I didn't intend to explain it, because it really needs a visual presentation, but here's the short version: both the planet and the ship count the number of blinks they see during the ships journey. The planet sees the last blink at the same time the ship gets there; the ship sees it earlier. Thus, it presents a contradiction in Newtonian physics, which can be resolved through length and time dilation.

Among physicists, to my knowledge, there is no known thought experiment or demonstration that cannot be reconciled with special relativity.

Actually, if you want to get specific, there's a significant flaw in relativity in every thought experiment - from an outside perspective, there is no difference between the planet sitting in place with the ship moving, and the ship sitting in place with the planet moving. There is no explanation why it must be the ship that experiences less time - it's all a matter of perspective. The same can be said of the twins experiment or any other. That is what I modeled in the example I gave before - a perfectly symetrical system. Length and time dilation do not resolve this one, because they can't each experience less time than the other. If you honestly believed that there were no thought experiments that couldn't be resolved by relativity, then I suggest you consider a nice career in the food service industry.

These people must not be physicists, or at least this ground-shaking refutation of special relativity has not gotten the publicity your bald assertion would seem to warrant.

Of course this doesn't get publicity - what physicists want to be the one that publicly states, "Hey, we don't know!" But in my experience, all of them (except you, if I'm to believe your claims of teaching relativity) are aware of it. It will become more widely exposed when and if someone comes up with an answer for it. However, if you'd done just a little bit of research on google, you'd have no problem finding plenty of examples of physicists who quite publicly address the flaws in relativity.

Re:How long was this light travelling? (1)

mmmmbeer (107215) | more than 7 years ago | (#16109370)

I'm afraid I've been unable to find a visual example of the thought experiment I mentioned. I know I've seen it on the web before, but there are so many search results that I couldn't find that specific one. There is a similar one where "Bob" flies a ship to another planet and back and "Ann" stays on Earth and watches, but it doesn't show the reasoning behind relativity - ie. the fact that light has the same constant speed regardless of inertial frame. It just shows the application of time dilation. However, I did find this: http://members.aol.com/carmam1534/Hollings1.html [aol.com] - another thought experiment which outlines the same type of asymetrical flaw in relativity.

Re:How long was this light travelling? (1)

wanerious (712877) | more than 7 years ago | (#16113344)

If you're going to trivialize all values of distance to the point that they are meaningless, then you're a fool.

Ok, I'll try again --- we can basically agree on local values of distance because, for a receding car on the freeway, the light travel time between the car and us is much shorter than the increase in the distance of the car during this light travel time. On larger scales, where the increase in separation due to the expansion of the universe is still significantly less than light speed, it's not too imprecise to measure distances to galaxies on the order of a hundred megaparsecs or so. At a redshift of, say, 10, the universe (and the galaxy, accordingly) was a factor of 10 (really 11, since it's z+1) closer to us at the time the light we observe now was emitted. To say that the light has crossed 13 billion light years of distance in the meantime is not right --- it is this distance itself that has increased in the meantime due to cosmological expansion, regardless of the particular model of how quickly the expansion occurred. This is related to the fundamental misunderstanding of special relativity that keeps popping up. To measure a *distance*, one needs *simultaneous* measurements of the boundaries in the rest frame of the observer. Here, with one end of the boundary possibly increasing its distance from us at speeds greater than that of light (it's certainly possible, in GR, for the coordinate distance of two galaxies to far exceed the speed of light in the expansion), assuming such a simultaneous measurement is meaningless. Sure, we all agree that light travels at speed c always, but it's the distance to be covered that keeps stretching during the transit.

And you claim to be a teacher of relativity? Ok, I'll assume for the moment that somehow that's true and yet you've never seen this basic thought experiment. I didn't intend to explain it, because it really needs a visual presentation, but here's the short version: both the planet and the ship count the number of blinks they see during the ships journey. The planet sees the last blink at the same time the ship gets there; the ship sees it earlier. Thus, it presents a contradiction in Newtonian physics, which can be resolved through length and time dilation.

We usually just say they carry identical, synchronized clocks. The distant blinking light makes the situation much more complicated because it doesn't measure the proper (local) time aboard the spaceship --- we need a clock *at rest in the frame of the ship*. I'm not sure how you're trying to interpret the results as being time dilation when you're not comparing the proper time in both frames. Using synchronized clocks, the seeming contradiction is not that the ship sees the light earlier, but that it will (if comparing proper clocks) count *fewer* blinks. Your example actually shows the opposite, that the ship will count *more* blinks in a shorter time.

Actually, if you want to get specific, there's a significant flaw in relativity in every thought experiment - from an outside perspective, there is no difference between the planet sitting in place with the ship moving, and the ship sitting in place with the planet moving. There is no explanation why it must be the ship that experiences less time - it's all a matter of perspective. The same can be said of the twins experiment or any other. That is what I modeled in the example I gave before - a perfectly symetrical system. Length and time dilation do not resolve this one, because they can't each experience less time than the other.

No! There is a huge difference between the frames in the twin experiment. One of the frames is no longer inertial (non-accelerating). This is also the running flaw in the link you provided. You simply can't compare a frame where special relativity applies with a frame where it doesn't. In inertial frames, length and time work together to resolve the seeming paradox. In the case of muon production and decay in the atmosphere, from a rest frame on the ground, it seems that muons created in the upper atmosphere travel at 99% of the speed of light towards the ground and reach the ground because of a dilated lifetime (normally, we'd think they'd decay long before reaching the ground). From the point of view of the muons, they register a normally short proper lifetime, but see the distance to the ground as being contracted, so again in their frame they reach the ground. The fact that we see the correct number of atmospherically produced muons is a beautiful confirmation of both time dilation and length contraction.

If you honestly believed that there were no thought experiments that couldn't be resolved by relativity, then I suggest you consider a nice career in the food service industry.

For one so mistaken in basic relativity, you are strangely brave to suggest I change my career.

Of course this doesn't get publicity - what physicists want to be the one that publicly states, "Hey, we don't know!" But in my experience, all of them (except you, if I'm to believe your claims of teaching relativity) are aware of it. It will become more widely exposed when and if someone comes up with an answer for it. However, if you'd done just a little bit of research on google, you'd have no problem finding plenty of examples of physicists who quite publicly address the flaws in relativity.

Oh, you're not going to play the conspiracy card, are you? That we physicists all know there is something dreadfully wrong, but we cover up the truth? Believe me, the first person to show *any* hint that special relativity is wrong in inertial frames is due serious Nobel consideration and international fame. Let him/her step forward. Seriously, you really might enjoy checking out *any* freshman/sophomore text on the subject, any of which will spell out the fundamentals of the theory in much more convincing detail that I have room to do here. Any modern physics text will do --- I've used Tipler, Halliday/Resnick, Serway. The best undergrad preparation in relativity I've seen is Moore's "6 Ideas that Changed Physics" text, and of course the Feynman Lectures are indispensable.

Re:How long was this light travelling? (1)

mmmmbeer (107215) | more than 7 years ago | (#16114889)

Once again, you completely misunderstand. I, along with the author of the article, am using a simpler cosmological model so that we can give a number that means something to others, instead of stupidly reducing everything to meaningless jargon. Actually, I was simply trying to correct the previous poster's misconception that light has to "catch up" to us at a speed of "c minus our speed." I never denied that cosmological expansion would effect the real value of the distance, but I chose to use a model that would make more sense to my target audience.

You've completely missed the point of the thought experiment. It assumes Newtonian physics, along with the premise that light travels at the same speed regardless of inertial frames. Thus it demonstrates the need for length and time dilation. The follow-up experiment then assumes l/t dilation, but still fails to resolve the contradiction; ie. that each ship experiences less time than the other. If you'd like to see a clearer example of relativity's failure to resolve certain paradoxes (particularly those in which l/t dilation is symmetrical), see the link in my other post. (Oh, and by the way, special relativity ALWAYS applies to ALL inertial frames. Newtonian physics is simply a special case. From the muons' perspective, it is the Earth that moves to them.) To try to explain it again, consider the twins experiment - it can also be modelled with the twin on the ship staying still, and the planet flying away and returning. Thus it would be the twin on the planet that experiences less time. Acceleration is the apparent difference between the two, but that is NOT currently accounted for in relativity.

I never said there was a conspiracy. It is simply that nobody with enough significance in the physics community is making a big deal out of this. And no, it won't shake the Earth if they do. First, it wouldn't surprise anyone who really knows the field, and second, no one has an answer yet. Absolutely, anyone who could answer it would certainly be in line for a Nobel.

Re:How long was this light travelling? (1)

wanerious (712877) | more than 7 years ago | (#16115173)

You've completely missed the point of the thought experiment. It assumes Newtonian physics, along with the premise that light travels at the same speed regardless of inertial frames. Thus it demonstrates the need for length and time dilation.

No, I get the point of the thought experiment, it's just a really poor and misleading demonstration that something like special relativity must be true. Glancing at any elementary-level text will reveal many better thought experiments that utilize the correct concept of proper time.

The follow-up experiment then assumes l/t dilation, but still fails to resolve the contradiction; ie. that each ship experiences less time than the other. If you'd like to see a clearer example of relativity's failure to resolve certain paradoxes (particularly those in which l/t dilation is symmetrical), see the link in my other post. (Oh, and by the way, special relativity ALWAYS applies to ALL inertial frames.

That each ship experiences less time than the other is *not* a contradiction. It only appears to be when we devise a way for them to return to each other to compare measurements, where the symmetry of the problem is broken --- one of the ships must *accelerate* to return to the other, and therefore special relativity no longer applies. As I indicated, I visited the link you supplied, and the arguments there suffer from this precise fallacy. You make the parenthetical remark as if that's something I'd argue with, when that's exactly the point I'm making. SR applies to all inertial frames, and *doesn't apply to non-inertial ones*.

To try to explain it again, consider the twins experiment - it can also be modelled with the twin on the ship staying still, and the planet flying away and returning. Thus it would be the twin on the planet that experiences less time. Acceleration is the apparent difference between the two, but that is NOT currently accounted for in relativity.

Of course it isn't accounted for. SR is not relevant in this domain. Your premise is false --- it *can't* be equivalently modeled by a stationary ship and a moving planet, because it's the ship that undergoes the accelerations. In other words, it's easy to distinguish between the frames: in both frames, keep a little box with a ball in the center. The ball will stay in the middle of the "stationary" box on the earth, but will roll around the ship's box since it has to accelerate and decelerate a couple of times. This will be true no matter which frame we're in, so we can easily distinguish which frame is accelerating. There is no way to set them up as equivalent (or relative) frames.

The fact that SR does not apply for non-inertial frames is indeed widely (universally) known. To say that this limitation implies that SR is "broken" or "wrong" is like saying that the spring force F=-kx is wrong because it doesn't work for objects sliding down inclined planes. It simply doesn't apply there.

I never said there was a conspiracy. It is simply that nobody with enough significance in the physics community is making a big deal out of this. And no, it won't shake the Earth if they do. First, it wouldn't surprise anyone who really knows the field, and second, no one has an answer yet.

You certainly insinuated that, even if someone knows something damning about SR, they wouldn't dare step forward. No one is making a big deal out of this because it's obvious to anyone who has successfully taken a course in SR. It's covered in the first couple days of a SR unit.

Re:How long was this light travelling? (1)

mmmmbeer (107215) | more than 7 years ago | (#16115312)

I most certainly did not insinuate that there was a conspiracy. What you inferred is your fault. However, if there were a need for such a conspiracy, you would clearly be a part of it. I'll tell you what, if you think that acceleration can account for the differences in the thought experiments given, why don't you show me the formulae in which said acceleration is accounted for?

Re:How long was this light travelling? (1)

mmmmbeer (107215) | more than 7 years ago | (#16115385)

Let me clarify - give the formulae in which the force behind the acceleration is taken into account. Acceleration, just like velocity, is symmetrical. From the perspective of the ship, the planet accelerates away from it.

Re:How long was this light travelling? (1)

wanerious (712877) | more than 7 years ago | (#16116393)

Let me clarify - give the formulae in which the force behind the acceleration is taken into account. Acceleration, just like velocity, is symmetrical. From the perspective of the ship, the planet accelerates away from it.

No. This is what I'm saying --- it's *not* symmetrical. Only the ship is in an accelerating, non-inertial frame. Giving an observer in each frame the little box with a ball in the center, only the one on board the ship will move in response to its acceleration. Both observers will agree on this. Here's another example: say I hold a pendulum bob at the end of a string, and you hold one while driving away from me in a car. As long as you're traveling at a constant velocity away from me, both bobs hang vertically, and the frames are indistinguishable. As soon as you hit the brakes, accelerate, or round a curve, the bob will deflect from the vertical position. Only your bob does this. You can't say that, from your point of view, your bob stays vertical and you see mine deflecting. As soon as one frame becomes non-inertial, all bets are off and we can't use SR any more. I can't give you a "formula" that will get you what you want, because SR doesn't apply. You can look up the formulae for relativistic forces and accelerations as they would appear to observers in other frames, they're pretty easy to derive and appear in all elementary texts, but that's not what we're talking about here.

Re:How long was this light travelling? (0)

mmmmbeer (107215) | more than 7 years ago | (#16116664)

I agree. Only one observer will see the ball move. BUT RELATIVITY DOES NOT ACCOUNT FOR THIS IN ANY EQUATION! That is why it is fully possible to model the planet moving and the ship sitting still. Also, this does not address the cases in which both observers are moving equally.

Re:How long was this light travelling? (1)

wanerious (712877) | more than 7 years ago | (#16117127)

BUT RELATIVITY DOES NOT ACCOUNT FOR THIS IN ANY EQUATION!

Of course not. It doesn't apply in that case. The Second Law of Thermodynamics does not account for the motion of an electron in a magnetic field, but we shouldn't infer that there's anything wrong with the thermodynamics because of this. There are regimes where we should use results from SR, and regimes where we shouldn't.

That is why it is fully possible to model the planet moving and the ship sitting still

Nope. It's completely different physics. The force required to accelerate the planet is very different from the force required to accelerate the ship. You're free to model the situation, but you're not free to say that it's the functional equivalent of the system where the ship is the one accelerating, and you're not free to use SR to compare results. Again, you can't use SR in a non-inertial frame. You just can't. If you want to make a big deal about the fact that SR is "broken" for non-inertial frames, it's hardly news, since it's only *defined* to be valid for inertial ones. That is, in fact, the *only* postulate you need to derive SR (the constancy of the speed of light is sort of a consequence of the postulate that all laws of physics give identical results in inertial frames).

Also, this does not address the cases in which both observers are moving equally.

I don't understand this. By "equally", do you mean that they're moving at a constant velocity with respect to each other? If so, there is no contradiction as I pointed out somewhere above.

a little flaw in their logic (0, Troll)

Desolator144 (999643) | more than 7 years ago | (#16105777)

First of all, I read the title and say "hey, we've known that for hundreds of years." Far away = old in the universe, duh! But really, it's not quite right. Surely I'm not the only one that realizes that when this supposed big bang happened, the things they're looking at weren't 13 billion light-years away. They started at the origin point and moved that far away now. The way they have it stated, it seems like they instantly teleported 13 billion light-years away during the big bang 13 billion years ago and the light is just getting to us now. Then there's the whole our position relative to the origin point relative to the galaxies they're looking at problem.
Load More Comments
Slashdot Login

Need an Account?

Forgot your password?
or Connect with...

Don't worry, we never post anything without your permission.

Submission Text Formatting Tips

We support a small subset of HTML, namely these tags:

  • b
  • i
  • p
  • br
  • a
  • ol
  • ul
  • li
  • dl
  • dt
  • dd
  • em
  • strong
  • tt
  • blockquote
  • div
  • quote
  • ecode

"ecode" can be used for code snippets, for example:

<ecode>    while(1) { do_something(); } </ecode>