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Gamma-Ray Photon Observations Indicate Space-Time Is Smooth

Soulskill posted more than 2 years ago | from the as-an-android's-bottom dept.

Space 81

eldavojohn writes "Seven billion light years away (seven billion years ago), a gamma-ray burst occurred. The observation of four Fermi-detected gamma-ray bursts (GRBs) has led physicists to speculate that space-time is indeed smooth (abstract and a pre-publication PDF both available). A trio of photons were observed to arrive very close together, and the observers believe that these are from the same burst, which means there was nothing diffracting their paths from the gamma-ray burst to Earth. This observation doesn't prove that space-time is infinitesimally smooth like Einstein predicted, but does indicate it's smooth for a range of parameters. Before we can totally discount the theory that space-time is comprised of Planck-scale pixels, we must now establish that the proposed pixels don't disrupt the photons in ways independent of their wavelengths. For example, this observation did not disprove the possibility that the pixels exert a subtler 'quadratic' influence over the photons, nor could it determine the presence of birefringence — an effect that depends on the polarization of the light particles."

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I guess we're not a huge-scale game of Minecraft (4, Funny)

InvisibleClergy (1430277) | more than 2 years ago | (#41192457)

At least we know for sure that we don't need to deal with Creepers.

Re:I guess we're not a huge-scale game of Minecraf (4, Funny)

Anonymous Coward | more than 2 years ago | (#41192537)

I don't know....here in the U.S. they seem to be campaigning every day...

Re:I guess we're not a huge-scale game of Minecraf (0)

Anonymous Coward | more than 2 years ago | (#41193671)

The Voyager probes would kill us all when the server crashed.

from the as-an-android's-bottom dept. (-1)

Anonymous Coward | more than 2 years ago | (#41192467)

bite my shiny metal ass.

In the words of Sheldon Cooper (0)

Anonymous Coward | more than 2 years ago | (#41192469)

Bazinga.

Not getting laid is your superpower! (0)

Anonymous Coward | more than 2 years ago | (#41192721)

Bazinga!

its time... (0)

Anonymous Coward | more than 2 years ago | (#41192491)

to walk the plank Planck-scale pixels

Size matters... (1)

bugs2squash (1132591) | more than 2 years ago | (#41192611)

" theories suggest the pixels should measure the size of the "Planck length," or about a billionth of a billionth of the diameter of an electron"

I thought electrons and all truly elementary particles had no size whatsoever, they were ideal points

Re:Size matters... (3, Funny)

invid (163714) | more than 2 years ago | (#41192699)

Just try to collide two ideal points in a particle accelerator.

Re:Size matters... (3, Informative)

maxwell demon (590494) | more than 2 years ago | (#41192755)

The electromagnetic field of a point particle is infinitely large. In the collisions, the particles don't really collide; they just get so close that the force between them gets quite large.

Re:Size matters... (1)

timeOday (582209) | more than 2 years ago | (#41192869)

I don't think things "touching" each has any literal meaning, does it? Two things "touching" means they're close enough that nuclear forces dominate. But you can always move them even closer by pushing harder.

Re:Size matters... (1)

maxwell demon (590494) | more than 2 years ago | (#41192891)

The post I answered to obviously interpreted it literally.

Re:Size matters... (1)

invid (163714) | more than 2 years ago | (#41193151)

Actually I was just being snarky.

Re:Size matters... (1)

rossdee (243626) | more than 2 years ago | (#41192881)

I thought they collided Protons which are much bigger than electrons

Re:Size matters... (1)

bugs2squash (1132591) | more than 2 years ago | (#41193195)

Protons are supposedly not elementary particles, since they are made of quarks, hence, to my mind, dimensions make sense for protons since their constituent quarks presumably range around some nominal volume.

Re:Size matters... (3, Informative)

invid (163714) | more than 2 years ago | (#41193305)

Some particle accelerators collide electrons and positrons.

Re:Size matters... (5, Informative)

maxwell demon (590494) | more than 2 years ago | (#41192719)

Probably they refer to the electron's Compton length, which in some sense can be viewed as effective size of the electron. If you try to resolve the electron beyond that size, you inevitably get particle creation.

However if I'm not mistaken, a billionth of a billionth of the electron's Compton wavelength is still about five orders of magnitude larger than the Planck length.

Re:Size matters... (1)

mbone (558574) | more than 2 years ago | (#41192965)

Yes, I think you are right (and that they were sloppy about their orders of magnitude).

Re:Size matters... (0)

Anonymous Coward | more than 2 years ago | (#41192777)

Nope. Electrons are not points; They are waveforms.
They don't have a size in the usual manner, but they have a wavelength, which is probably what TFA is calling a "diameter."

Re:Size matters... (0)

Anonymous Coward | more than 2 years ago | (#41196875)

The waveform concept deals with uncertainty of the electron's position (or other properties), while still treating it as a point particle. In principle, you could resolve the electron's position as finely as you want assuming you can create an electron or photon of sufficient energy to probe that position, and you won't know much about the momentum after the high energy collision. A lot of quantum mechanics and field theory is built around the idea they are point particles. Additionally, the wavelength is a bad size to use in general, since it varies with many orders of magnitude depending on the electron's momentum. Most likely they are referring to one of the several semi-classical electron sizes that are derived from how they act in collisions (i.e. roughly like treating them as hard billiard balls instead of particles with a 1/r^2 field) or some rough length scale derived from their rest mass or energy.

Re:Size matters... (1)

mbone (558574) | more than 2 years ago | (#41192795)

" theories suggest the pixels should measure the size of the "Planck length," or about a billionth of a billionth of the diameter of an electron"

I thought electrons and all truly elementary particles had no size whatsoever, they were ideal points

Not on the Planck scale (or ,at least, it was assumed, not on the Planck scale). Nothing should be ideal (i.e., a point) on the Planck scale.

Re:Size matters... (4, Funny)

Antipater (2053064) | more than 2 years ago | (#41192849)

I thought electrons and all truly elementary particles had no size whatsoever, they were ideal points

Don't worry, there's always more to learn. Before I came to Slashdot, I thought there were gnomes in my computer, riding gnus and drinking wine.

Re:Size matters... (1)

Anonymous Coward | more than 2 years ago | (#41194437)

Before I came to Slashdot, I thought there were gnomes in my computer, riding gnus and drinking wine.

And now you've been to Slashdot? "Now I know it for certain".

Re:Size matters... (1)

marcosdumay (620877) | more than 2 years ago | (#41193499)

Do we even know anything for sure? As far as I know, people ruled out anything bigger than a very small size, but saying that it has no size is a big jump from there.

Re:Size matters... (3, Informative)

walter_f (889353) | more than 2 years ago | (#41194459)

For a number of scientific considerations, one can treat elementary particles (like the electron) as point-like objects, and legitimately so.

But the Planck length is a unit that is about 18 magnitudes (i.e., 18 powers of 10) smaller than anything one might define as the "size" of an electron.

If you imagine a ruler with a dozen Planck lenghts as units printed on it instead of inches, then in comparison an electron would be an enormous object, much bigger than the size of a planet.

Re:Size matters... (3, Informative)

thrich81 (1357561) | more than 2 years ago | (#41194803)

It is not so much that elementary particles are mathematical points (zero dimensional objects) as that they have no internal "structure" like the 'non-elementary' particles (protons, for example) and no even more 'elementary' constituents. At the deepest level in the Standard Model all 'particles' are described as excitations of quantum fields and have positive probability density over a region in space which is not a point. Electrons are conventionally referred to as "point particles" but that is slang for the deeper description.

Model vs "reality" (0)

Anonymous Coward | more than 2 years ago | (#41198635)

Well, the fact that they can be modelled as ideal points does not mean they actually are ideal points.

Unit overlap (3, Interesting)

jovius (974690) | more than 2 years ago | (#41192677)

Shouldn't all of the points of space have their own frames of references and not be synced anyway? The planck length units would overlap practically infinitely.

Re:Unit overlap (1)

TheRealMindChild (743925) | more than 2 years ago | (#41194687)

Forget should. They DON'T have their own frame of reference. It is all consistent (based upon what we know, as per the arcticle)

Sensational (4, Insightful)

tanujt (1909206) | more than 2 years ago | (#41192747)

I am not qualified to comment on the accuracy of the findings and their subsequent interpretation of the data. However, as the senior scientist Giovanni Amelino-Camelia suggested, "But the claim that their analysis is proving that space-time is 'smooth with Planck-scale accuracy' is rather naive." (He was the first one to theoretically suggest methods with which one could test for the "discreteness" of space-time)

Is it the artifact of the social media/e-news and the ever growing need for public attention to science (which translates into the elusive funding dollars), that lately a lot of discoveries are being touted as "physics defying", "life altering" etc before they are scrutinized thoroughly? We've already had a faster-than-light and a second-law-of-thermodynamics-broken debacle, and who knows how many more (scour the arXivs and you shall find!). A lot of the stories of scientific discoveries diffuse out of public interest fast, especially now that people are cynical about groundbreaking claims. I wonder if we need to make a conscious effort to not make a big deal out of every discovery, at least not before the data is converted to valuable information. Although, I see the catch-22 here, as the scientific community is trying to break the stereotype of "hard, cold truths presented in a bleak technical manner" or "how does that even remotely affect me", to appease their indirect, impatient employers: the public.

Re:Sensational (2)

mbone (558574) | more than 2 years ago | (#41192997)

I am not qualified to comment on the accuracy of the findings and their subsequent interpretation of the data. However, as the senior scientist Giovanni Amelino-Camelia suggested, "But the claim that their analysis is proving that space-time is 'smooth with Planck-scale accuracy' is rather naive." (He was the first one to theoretically suggest methods with which one could test for the "discreteness" of space-time)

Is it the artifact of the social media/e-news and the ever growing need for public attention to science (which translates into the elusive funding dollars), that lately a lot of discoveries are being touted as "physics defying", "life altering" etc before they are scrutinized thoroughly?

Maybe, but I don't think so in this case. Note that Amelino-Camelia is not saying that they can't be right, just that there is some more due diligence that needs to be done. That is rather different from, e.g., the superluminal neutrino case (which actually, note, disagreed with neutrino speed estimates from the 1987-A supernova). This particular case has actually been building for a while (this is not the first look at the dispersion of spacetime over cosmic distances).

Re:Sensational (2)

slinches (1540051) | more than 2 years ago | (#41193199)

Please stop trying to bring rational thought into science journalism. If you succeed, I'll lose my main source of income [xkcd.com] .

Smooth? (1)

wcrowe (94389) | more than 2 years ago | (#41192835)

I guess I don't really understand physics well enough. I thought at the quantum level space was all knobbly and twitchy.

Re:Smooth? (2)

PolygamousRanchKid (1290638) | more than 2 years ago | (#41192967)

I thought at the quantum level space was all knobbly and twitchy.

It depends on how you touch it.

Re:Smooth? (1)

mbone (558574) | more than 2 years ago | (#41193009)

Supposed to be, on purely theoretical grounds. This is evidence against that notion.

Re:Smooth? (0)

Anonymous Coward | more than 2 years ago | (#41193127)

The assumption is that because the earth was hit by three photons that took nearly identical paths at nearly identical times, that the entire universe must be uniform except for the parts that we can see that aren't, and the assumed giant globs of dark matter.

Unlike the title, the summary is at least accurate enough to say that it leads to speculation of a smooth universe. Even in a universe chock full of strange dramatic, invisible gravitational anomalies (like Star Trek's universe), getting hit by a bunch of photons from a singular event at roughly identical timing doesn't actually prove anything either way, but since there was not a significant difference in arrival times, it fails to prove that the universe is full of awkward time-space shifting phenomena.

Re:Smooth? (0)

Anonymous Coward | more than 2 years ago | (#41193599)

So, it's like looking up at the sky in the middle of the day though a straw and seeing that it's blue over the who straw aperture. From that we can postulate that the sky all over the world is blue, except in places where we know it's not, like when there are clouds. Or planes. Or hot air balloons. Or it's dark outside.

It does prove that the sky is blue right then and there, though, and there are reasons to think it would be blue elsewhere.

Re:Smooth? (0)

Anonymous Coward | more than 2 years ago | (#41196907)

It does provide evidence one way, in the sense it sets some reasonable upper bounds on the extent of such anomalies if they existed. At some point, if those anomalies were so common, the chances of getting such an observation would be incredibly unlikely.

Re:Smooth? (1)

macromorgan (2020426) | more than 2 years ago | (#41193875)

I guess I don't really understand physics well enough. I thought at the quantum level space was all knobbly and twitchy.

I thought from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly, timey wimey stuff.

A blow against Quantum Gravity? (5, Interesting)

mbone (558574) | more than 2 years ago | (#41192871)

If you ask, at what scale do virtual particles (the stuff continually popping in and out of existence) get so massive that they have gravitational effects (i.e., form little mini black holes), you get the Planck mass, and the Planck length and time come from that. It is, however, very hard to see how you can reconcile these experimental results with the notion that mini-black holes really are popping in and out of existence at the Planck scale. That may mean no space-time foam (what is supposed to result from this violent behavior at the Planck scale).

This is not a problem for General Relativity, but it is a problem IMHO for quantum gravity. The old question, at the Planck scale does General Relativity become more like quantum mechanics, or does quantum mechanics become more like General Relativity, may get an answer that the quantum mechanicians do not like.

Re:A blow against Quantum Gravity? (4, Interesting)

maxwell demon (590494) | more than 2 years ago | (#41193125)

I'm no expert in quantum gravity, but I have sometimes the impression that the pictures of spacetime quantization are often a bit naive; basically the pictures of quantum spacetime look to me more like a classical discrete spacetime. I can't of course exclude the possibility that it's just the presentation.

Think for example of the quantization of the electron spin: It has only two states, up and down. Does that mean that the electron has a certain preferred direction, because, after all, it can only be up and down? Definitely not! You can choose an arbitrary direction, and for each direction you'll find that it is either up or down, and nothing else. But that isn't a contradiction, because the electron isn't just a classical particle whose spin points in a certain direction, and when you measure it, you find out which spin it had. Instead, it's the measurement itself which determines the direction in which you get up or down, and it is the measurement which forces the electron into one of the states. Before it might have been in a superposition. And if you choose another direction, you'll find that the very same state corresponds to another superposition of the up and down states corresponding to that direction. Indeed, for the electron all directions are equal (the current state may be associated with a specific direction, but every direction has an associated state, making no direction fundamentally different than the others).

Now when we come to the Planck length, I can imagine that the very same happens: The spacetime itself is not discrete, just as the directions of the electron spin are not discrete. But if we try to measure it, we can only get discrete values. But those discrete values are not a property of the spacetime itself, because we can make another measurement, and then maybe our discrete values are half a Planck length shifted, just as we can make a measurement of the electron's spin in z direction, and then in x direction, and we will find that the electron's spin after the second measurement is rotated by a right angle, despite the fact that for each measurement individually the only possible values are in opposite directions.

Re:A blow against Quantum Gravity? (1)

TheRealMindChild (743925) | more than 2 years ago | (#41194701)

You can choose an arbitrary direction, and for each direction you'll find that it is either up or down, and nothing else

Except for when it is both

Re:A blow against Quantum Gravity? (2)

FrangoAssado (561740) | more than 2 years ago | (#41195513)

That's not how the electron spin works. When you're talking about the spin state of a single, non-entangled electron, the state "both up and down" is exactly the same as the state "up" in a direction perpendicular the original "up/down".

Re:A blow against Quantum Gravity? (1)

khallow (566160) | more than 2 years ago | (#41199077)

The first order quirk of quantum mechanics is a different counting of states than you get classically. For example, if you flip two coins, you have a quarter chance of them both ending up heads or tails each. And a fifty percent chance of them ending up mixed. If those two coins are bosonic quantum states then there's a one third chance of each outcome, both heads, both tails, or mixed. There is only one mixed state because the two mixed states of the classical case are identical in the quantum case.

If the coins are fermionic quantum states, then there's no case where they can have identical flips (this is the case with two electrons trapped in a small space). Then the only state possible is the mixed state (and for what it's worth, it only appears once for the same reason as above).

Re:A blow against Quantum Gravity? (1)

bcrowell (177657) | more than 2 years ago | (#41199419)

I'm no expert in quantum gravity, but I have sometimes the impression that the pictures of spacetime quantization are often a bit naive; basically the pictures of quantum spacetime look to me more like a classical discrete spacetime. I can't of course exclude the possibility that it's just the presentation.

The two main contenders are string theory (ST) and loop quantum gravity (LQG). ST doesn't quantize spacetime at all. LQG gives quantization of area and volume, but not lengths. It is definitely wrong to present either theory as existing on a discrete grid: http://math.stackexchange.com/questions/186076/is-there-such-a-thing-as-discrete-riemannian-geometry [stackexchange.com]

Re:A blow against Quantum Gravity? (2)

BitZtream (692029) | more than 2 years ago | (#41193485)

Just for pedantic reference, if anyone 'Likes' or 'does not like' these answers, they aren't scientists.

There is no Like, only facts and theorys. Anything else is religion.

Re:A blow against Quantum Gravity? (1)

joe_frisch (1366229) | more than 2 years ago | (#41194501)

Do all quantum gravity models require spacetime to be non-smooth at the plank scale?

The data only looks like 3sigma so it could be the mini-bursts of gammas were coincidence, but more data should really nail it down.

If true this is a really important bit of research.

Re:A blow against Quantum Gravity? (2)

bcrowell (177657) | more than 2 years ago | (#41196573)

What you're presenting is similar to a point of view that was being pushed ca. 2006 by some folks at the Perimeter Institute doing loop quantum gravity (LQG). They were talking like they had a theory that really made predictions about vacuum dispersion that would be testable by the GLAST gamma-ray telescope. That was exciting, because if your theory doesn't expose itself to the possibility of falsification, then you're not really doing science. Unfortunately it then became clear that LQG doesn't actually make any such definite prediction. LQG might predict much less vacuum dispersion, or none at all. This puts LQG back in the same category as string theory: theories that aren't really theories yet, because they don't make predictions. (String theory does kinda sorta require supersymmetry at the electroweak scale, so in that sense it has failed an experimental test, because the LHC doesn't seem to be finding supersymmetry.)

Re:A blow against Quantum Gravity? (0)

Anonymous Coward | more than 2 years ago | (#41214623)

Numerical relativity has been producing some interesting results that go to the question of whether GR should go away for physics in the limit of high individual particle energies and short length scales. In particular, the Post-Newtonian Approximation has been remarkably effective in helping explore the mechanisms at these scales and how they influence the generation of the metric.

It is certainly a stretch to imagine that some approximation of GR will become the formalism of choice of high energy physicists exploring outside the weak field limit, but a useful effective theory is a useful effective theory, and almost all the useful metrics and theories that use GR have far fewer free parameters than the standard model, and (arguably) they seem more natural than those from e.g. the string theory landscape.

I think one of the problems is that everyone is taught SR first and it's hard to unlearn it when first encountering GR; hopefully future students will benefit from pedagogical materials that can take them from classical mechanics to some form of QFT and GR without passing through the less general theories first.

Incidentally, it's not just the quantum mechanicians who might not like the answer - it may be that a suitable choice of coordinates leads to a correct metric for things like black hole thermodynamics, or to a more natural approach for discovering the initial values at the early boundary condition of the universe, but if the result is hard (computationally and/or intuitively) to relate to the classical limit, relativists won't be happy either ! (And anyway, there are fewer and fewer working relativists who aren't also gauge theorists by necessity, so it's not like they aren't keen on preserving the successes of QM.)

Doctor Who Premieres tomorrow (1)

omnichad (1198475) | more than 2 years ago | (#41192899)

So it's not a wibbley-wobbley timey-wimey stuff?

Re:Doctor Who Premieres tomorrow (1)

mbone (558574) | more than 2 years ago | (#41193045)

I would not go against the good Dr. [youtube.com] .

  I assumed, however, he was talking about the macro scale, not the micro.

Re:Doctor Who Premieres tomorrow (2)

wonkey_monkey (2592601) | more than 2 years ago | (#41193503)

I would not go against the good Dr. [youtube.com].

I wouldn't call him "Dr." unless you want to chased out of town by rabid fans :) He's the Doctor [youtube.com] .

Re:Doctor Who Premieres tomorrow (1)

mbone (558574) | more than 2 years ago | (#41194831)

I didn't see any spelling... And, 53 seconds in, he calls himself "a Doctor," not "the" Doctor.

Re:Doctor Who Premieres tomorrow (1)

geekoid (135745) | more than 2 years ago | (#41194937)

The video was only 15 seconds.

Re:Doctor Who Premieres tomorrow (1)

mbone (558574) | more than 2 years ago | (#41195099)

Mine was, but his was 16:45 [youtube.com] .

I may have understood every 5th word in that blurb (0)

Anonymous Coward | more than 2 years ago | (#41193073)

maybe

Feinman (1)

Anonymous Coward | more than 2 years ago | (#41193147)

I don't remember exactly but Feynman said something to the effect that a sign of a bogus theory is that it makes predictions just beyond what is observed. An when observations improve, the theory is modified to predicted an even smaller effect.

e=mc SQUARED. (0)

Anonymous Coward | more than 2 years ago | (#41193487)

A photon isn't big enough.

7 billion years isn't long enough.

No 7B years ago (-1)

gstrickler (920733) | more than 2 years ago | (#41193551)

At least, not in our causal reference. It happened here very recently. It happened as a space-time distance of 7B ly. It was only 7B ly ago in the frame of reference of the origin.

Space/time duration/distance (4, Interesting)

wonkey_monkey (2592601) | more than 2 years ago | (#41193579)

Seven billion light years away (seven billion years ago)

I may not have this right, but due to the expansion of space, wouldn't it have been closer than seven billion light years away at the time of the kaboom? And if the light's taken seven billion light years to get here, space will have expanded further, so the remnants would now be further than seven billion light years away. Right?

Or is this the sort of thing where you can be specific about the distance, or the time, but not both?

Re:Space/time duration/distance (3, Interesting)

whoisisis (1225718) | more than 2 years ago | (#41193953)

Seven billion light years away (seven billion years ago)

I may not have this right, but due to the expansion of space, wouldn't it have been closer than seven billion light years away at the time of the kaboom? And if the light's taken seven billion light years to get here, space will have expanded further, so the remnants would now be further than seven billion light years away. Right?

Or is this the sort of thing where you can be specific about the distance, or the time, but not both?

Wikipedia [wikipedia.org] has an answer, but I think the above is just meant to give the layman some rough understanding of what's going on.

Beware that it is extremely difficult to measure these kinds of distances exactly. The figure may be a few orders of magnitude wrong, so whether you take into account the expanding universe or not may not be that important...
Cosmologists measure everything in gigaparsec. 7b light years is only 0.3 GPc so it may not be that important.

Re:Space/time duration/distance (3, Interesting)

wonkey_monkey (2592601) | more than 2 years ago | (#41194559)

My new fact for the day, from that Wikipedia page: the matter which emitted the CMB photons was "only" 42 million light years away at the time.

Re:Space/time duration/distance (4, Informative)

mbone (558574) | more than 2 years ago | (#41194785)

There are multiple distance measures in cosmology - they are all in principle exact (at least, if you know all your cosmological parameters), but they differ significantly once you start getting above about 1 billion light years. Much above that, and they can differ incredibly much. Some of these measures are based on idealized measurements, others on the physics directly.

Some measures used in cosmological work are,

- proper motion distance (the distance a parallax measurement would give you)
- luminosity distance (the distance you would infer from the apparent brightness of a standard candle)
- angular diameter distance (the distance you would infer from the apparent angular size of a standard sized object). The angular diameter distance is notorious for getting smaller if you get far enough away in many cosmologies (including, apparently, the one we live in).
- look back distance (if you imagine that everyone has a clock synchronized at the big band, the difference between your time and the time you would read on the remote clock, if you could read it). This is also called the light travel time.
- proper distance (what some long yardstick would read).
- comoving distance (the proper distance divided by the scale factor - 1 plus the redshift, z - for the remote observer, to get a distance that doesn't change with cosmological time).

And, finally, each cosmological model will have a coordinate distance (the difference between the coordinates of two different places), which need not have a simple relation to any of the above.

It is fair to say that one of the easiest ways to make a fool of yourself in cosmology is to mix up distance scales. (As an additional cause of mixups, only proper distances can be subtracted - for the rest, the distance between A and B is NOT the difference of the distance to A and the distance to B, even if A and B are on a straight line as seen from the Earth.)

In this case, the Gamma Ray Burst 090510A was at a red shift of 0.897. Go to the Cosmology Calculator [ucla.edu] and you find that that

For Ho = 71, OmegaM = 0.270, Omegavac = 0.730, z = 0.897

It is now 13.666 Gyr since the Big Bang.
The age at redshift z was 6.376 Gyr.
The light travel time was 7.290 Gyr.
The comoving radial distance, which goes into Hubble's law, is 3053.8 Mpc or 9.960 Gly.
The angular size distance DA is 1609.8 Mpc or 5.2505 Gly.
The luminosity distance DL is 5793.1 Mpc or 18.895 Gly.

The proper distance is (1+z) times the comoving distance, or 18.89 Gly.

Re:Space/time duration/distance (1)

mbone (558574) | more than 2 years ago | (#41196677)

Argh - a typo - there is both a parallax distance and a proper motion distance, and they are not the same.

Neither are used much as we can't measure proper motions or parallaxes at cosmological distances... yet.

Re:Space/time duration/distance (0)

Anonymous Coward | more than 2 years ago | (#41194917)

I suggest that you listen to Astronomy Cast, a really nice podcast; it will answer this question for you with a lot more eloquence than I can.

To answer succinctly, though, you are correct. This explosion happened 7 billion years ago and, now, it is farther away. When astronomer's talk about "now" they are usually referring to the observations in the sky, not what is "actually" going on in the objective they are viewing. So the scientists are aware of the fact that something is now farther than we see it is, but it's just a fact they live with and incorporate into their understanding.

Astronomy can be kind of confusing.

Before we can totally discount the theory that... (1)

Anita Coney (648748) | more than 2 years ago | (#41193715)

"Before we can totally discount the theory that space-time is comprised of Planck-scale pixels..."

And you lost me.

Re:Before we can totally discount the theory that. (1)

93 Escort Wagon (326346) | more than 2 years ago | (#41197159)

"Before we can totally discount the theory that space-time is comprised of Planck-scale pixels..."

And you lost me.

The author is simply referring to the Ultra-Retina Display that was added to the New Universe (3rd gen).

Truly, you have a dizzying intellect... (0)

Anonymous Coward | more than 2 years ago | (#41194623)

Just wait until I get started!

Until you make it angry (1)

Culture20 (968837) | more than 2 years ago | (#41194639)

SpaceTime Smash!

OW! (1)

uslurper (459546) | more than 2 years ago | (#41194759)

OW! MY HEAD!

Fixed summary (1)

Shavano (2541114) | more than 2 years ago | (#41195217)

This is what I THINK the author meant:

"Seven billion light years away (seven billion years ago), a gamma-ray burst may have occurred. The observation of four Fermi-detected gamma-ray bursts (GRBs) has led physicists to speculate that space-time is indeed smooth (abstract and a pre-publication PDF both available). A trio of photons XwereX was observed to arrive very close together, and the observers believe that these are from the same burst, which XmeansX suggests that there was nothing diffracting their paths from the gamma-ray burst to Earth. This observation doesn't prove that space-time is infinitesimally smooth like Einstein predicted, but does indicate it's smooth for a range of parameters. Before we can totally discount the theory that space-time is XcomprisedX composed of Planck-scale XpixelsX voxels, we must now establish that the proposed XpixelsX voxels don't disrupt the photons in ways independent of their wavelengths. For example, this observation did not disprove the possibility that the XpixelsX voxelsexert a subtler 'quadratic' influence over the photons, nor could it determine the presence of birefringence — an effect that depends on the polarization of the light particles."

Writing is not entirely a lost art, but it's close.

MWEEEP, wrong. Try again. (0)

Anonymous Coward | more than 2 years ago | (#41195835)

"Seven billion light years away (seven billion years ago), "

doesn't make sense to me (0)

slashmydots (2189826) | more than 2 years ago | (#41196267)

Well since space/time obviously warps based on speed an gravity (proven by atomic clocks on satellites orbiting Earth) then that's completely wrong. Since photons travel at the speed of light, don't they all independently max out the level of warping capable of space so they appear to all be 100% unaffected by anything else? Why wouldn't they get misaligned slightly from gravity though? They can't say the timing matched but the vectors didn't, indicating the same absolute distance through space, as the timing would be off for one traveling at a slight angle relative to whatever sensor they used. Also, how could they even determine the angle with a single plane as a receiver, like it sounds like they perhaps used. Not a word of that article makes sense or sounds remotely true.

Re:doesn't make sense to me (1)

DMUTPeregrine (612791) | more than 2 years ago | (#41198451)

Smooth is not the same as flat. A sine wave is smooth, but certainly not flat.

Smooth because... (0)

Anonymous Coward | more than 2 years ago | (#41196273)

There's nothing there. Space as a thing doesn't exist. There are only things that exist relative distances apart from each other floating amid the nothing. To say that space exists is to accept aether, which at best is background radiation.

Likewise, time doesn't exist as a physical thing. There is only decay. Time travel will never be possible.

Accept it. Move on. The theories and formulae based on those two things existing don't need to be tossed away, because they are a reasonable facsimile to explain phenomena, but never make the mistake of believing that existence and reality are defined by mathematical formulae. They can only explain why we find things in existence and reality, never create it.

"Seven billion" (0)

Anonymous Coward | more than 2 years ago | (#41196523)

"Seven billion light years away (seven billion years ago)"

I dont get, can you explain how seven billion light years is seven billion years???

Re:"Seven billion" (1)

Azure Flash (2440904) | more than 2 years ago | (#41196575)

It's seven billion light years away, but since it took light seven billion years to get to us, that also means it's seven billion years ago.

Re:"Seven billion" (0)

Anonymous Coward | more than 2 years ago | (#41196613)

That didnt take long.

Anyone else want to explain this to us dummies that have not heard this a billion time already?

Re:"Seven billion" (0)

Anonymous Coward | more than 2 years ago | (#41197191)

It's seven billion light years away, but since it took light seven billion years to get to us, that also means it's seven billion years ago.

no. It's nearly 19 billion light years away. See comment above concerning differing cosmological scales.

Ricky Gervais (1)

Azure Flash (2440904) | more than 2 years ago | (#41196567)

"Hey, look at that, there's a gamma-ray burst seven billion light years away. I guess that means space-time is smooth, huh?"

What kind of maniac thinks like that?

http://www.youtube.com/watch?v=6ktBQ51iGWw#t=106s [youtube.com]
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