How are galaxies moving away faster than light?

October 13, 2015 by Fraser Cain , Universe Today
The space between the galaxies is expanding. How big is it? Credit: NASA/HST

So, how can galaxies be traveling faster than the speed of light when nothing can travel faster than light?

I'm a little world of contradictions. "Not even light itself can escape a black hole", and then, " and they are the brightest objects in the universe". I've also said "nothing can travel faster than the speed of light". And then I'll say something like, " galaxies are moving away from us faster than the speed of light." There's more than a few items on this list, and it's confusing at best. Thanks universe!

So, how can galaxies be traveling faster than the speed of light when nothing can travel faster than light? Warp speed galaxies come up when I talk about the expansion of the universe. Perhaps it's dark energy acceleration, or the earliest inflationary period of the universe when EVERYTHING expanded faster than the speed of light.

Imagine our expanding universe. It's not an explosion from a specific place, with galaxies hurtling out like cosmic jetsam. It's an expansion of space. There's no center, and the universe isn't expanding into anything.

I'd suggested that this is a terribly oversimplified model for our universe expanding. Unfortunately, it's also terribly convenient. I can steal it from my children whenever I want.

Imagine you're this node here, and as the toy expands, you see all these other nodes moving away from you. And if you were to move to any other node, you'd see all the other nodes moving away from you.

Here's the interesting part, these nodes over here, twice as far away as the closer ones, appear to move more quickly away from you. The further out the node is, the faster it appears to be moving away from you.

This is our freaky friend, the Hubble Constant, the idea that for every megaparsec of distance between us and a distant galaxy, the speed separating them increases by about 71 kilometers per second.

Galaxies separated by 2 parsecs will increase their speed by 142 kilometers every second. If you run the mathatron, once you get out to 4,200 megaparsecs away, two galaxies will see each other traveling away faster than the speed of light. How big Is that, is it larger than the universe?

The first light ever, the radiation, is 46 billion light-years away from us in all directions. I did the math and 4,200 megaparsecs is a little over 13.7 billion light-years.There's mountains of room for objects to be more than 4,200 megaparsecs away from each other. Thanks universe?!?

How are galaxies moving away faster than light?
WMAP data of the Cosmic Microwave Background. Credit: NASA

Most of the universe we can see is already racing away at faster than the speed of light. So how it's possible to see the light from any galaxies moving faster than the speed of light. How can we even see the Cosmic Microwave Background Radiation? Thanks universe.

Light emitted by the galaxies is moving towards us, while the galaxy itself is traveling away from us, so the photons emitted by all the stars can still reach us. These wavelengths of light get all stretched out, and duckslide further into the red end of the spectrum, off to infrared, microwave, and even radio waves. Given time, the photons will be stretched so far that we won't be able to detect the galaxy at all.

In the distant future, all galaxies and radiation we see today will have faded away to be completely undetectable. Future astronomers will have no idea that there was ever a Big Bang, or that there are other outside the Milky Way. Thanks .

I stand with Einstein when I say that nothing can move faster than light through space, but objects embedded in space can appear to expand faster than the of depending on your perspective.

Explore further: How fast is the universe expanding?

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18 comments

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Torbjorn_Larsson_OM
4.1 / 5 (9) Oct 14, 2015
Ogg_ogg, that is not very generous. Here is a generous criticism by a cosmologist:

"Breaking my radio silence here to get a little nitpick off my chest: the claim that during inflation, the universe "expanded faster than the speed of light." It's extraordinarily common, if utterly and hopelessly incorrect. (I just noticed it in this otherwise generally excellent post by Fraser Cain.)" [ http://www.prepos...f-light/ ]
Torbjorn_Larsson_OM
4 / 5 (8) Oct 14, 2015
Since we are doing nitpicks, here is my own:

"In the distant future, all galaxies and radiation we see today will have faded away to be completely undetectable. Future astronomers will have no idea that there was ever a Big Bang, or that there are other galaxies outside the Milky Way."

With a supermassive black hole in the center of the MW, and an ever diminishing but never zero supply of young large binaries from star production, the MW will always throw off hypervelocity young large stars. When they come out to ~ 0.1 Mlyrs or so, large stars will still be visible and cosmological redshift will be discernible. As for other galaxies, like our own early exoplanet search they can conclude that there were other galaxies while not seeing any. They can then conclude that dark energy moved them too far away to be visible.

Yes, they will have less certainty than we have, but they will have these ideas.
Bigbangcon
2.5 / 5 (11) Oct 14, 2015
Official cosmology is based on the presuppositions that 1) the universe has a beginning and a Big Bang started it, 2) velocity of light (though constant locally) is an absolute universal constant and everything else is relative, 3) redshift is a measure of distance, 4) Supernova Type 1a is the only kind of Supernova, 5) the cosmic monsters like black hole, dark matter/ energy exists etc.

None of these have any real basis and are mostly based on the unlimited extension of idealized mathematics. The universe is a living system (process) like a living animal whose cells continuously die off and new ones are formed; with the only difference that the universe is eternal in time and infinite in space. Quantum Electro-Dynamics (QED) and a Dialectical Perspective allow us to a have realistic idea of the universe without any mysteries and monsters.: http://www.amazon...40414445


jeffensley
2 / 5 (8) Oct 14, 2015
Ok so I'm going to combine a couple of theories here into one. The author suggests that space is forming everywhere, all the time. The greater the distance between two objects, the more "new" space is being formed between them and the faster they appear to be moving apart. Now since we haven't identified any particular celestial bodies "emitting" space, we can assume it's happening everywhere, slowly stretching out the bonds of matter as we know it. This being the case, isn't it possible that the Earth was actually smaller billions of years ago... lending credence to the oft-laughed at Expanding Earth theory? I'll be honest... Pangea just doesn't do it for me. I see no good reason for one blob of land to exist on one side of the planet like that. The Expanding Earth however, at least based on the illustrations I've seen, fits together quite neatly. I've even heard there is fossil evidence linking the West Coast of North America with East Asia. Thoughts?
jeffensley
4 / 5 (8) Oct 15, 2015
If expanding space is not detectable locally, why build a theory around the notion that it is happening "universally"?


Because it's fun? Ideas/hypotheses set the course for research which helps to confirm or deny their plausibility. Just because we lack the ability to measure something doesn't mean it isn't plausible... though it does make it hard to prove. We still seem to think the universe is limited to the things we can see with the instruments we design. When it comes to astrophysics, I think most everything deserves to be left on the table... we're sitting at one point in one minuscule part of the galaxy which is one minuscule part of the observable universe. To pretend we understand what's going on is unscientific IMO.
Returners
3.4 / 5 (9) Oct 17, 2015
The first light ever, the cosmic microwave background radiation, is 46 billion light-years away from us in all directions


This is not a fact, though you present it as one.
This is an extrapolation based on a mathematical model, which we already know does not correctly describe reality even at the galaxy/galactic cluster scale.

In fact, almost every measurement in modern cosmology is made under the assumption that every aspect of Special and General relativity is absolutely correct. This practise is inherently flawed, because you are re-interpreting observations through the theory, rather than re-interpreting the theory through observation....which is the exact opposite of the Scientific Method.
AGreatWhopper
3.5 / 5 (8) Oct 17, 2015
Resolved: PO is regularly crafting pure troll bait with no other purpose or use.
Returners
3.3 / 5 (7) Oct 17, 2015
Here's a challenge:

Measure the distance and age of the nearest Quasar....

...without relying on foregone assumption of SR and GR being true, and without using any formulas based on those theories...

Geometry should be able to do the distance.
I don't claim to know how to get it's age, because all the wavelength information you use assumes Relativity to be true, and assumes the laws to be the same for all space and time...which means you don't even have an independent methodology for studying any of this stuff without the foregone conclusion that SR and GR are always true...and that's a problem, because it once again violates the Scientific Method...which you people claim to adhere to so strongly.
Returners
3.4 / 5 (5) Oct 18, 2015
How can be sure that in other regions of cosmic space speed of light is not different than measured speed in our local region?


The answer is "You can't be sure."

That is axiomatic. You can never 100% confirm that assumption, regardless of local evidence.

Moreover, even local evidence is now flawed, because when they measure the "speed" of light they are now using atomic clocks to measure the speed of light...so they define "time" by the speed of light, and then they measure the speed of light, and then they say "aha, the speed of light is always the same in a vacuum!"

Well, duh...you re-defined the word "time" to ensure that the speed of light is always the same....

DM, DE and black holes as currenty theorized cause more problems...


I agree regarding DM and DE, but I can't say that I agree on Black Holes, since they are also predicted by both Newton's and Einstein's gravity, and we know there is "something" very like them by observation.
Returners
3.4 / 5 (5) Oct 18, 2015
Since we are doing nitpicks, here is my own:

Here's one.

If you solve the approximation for the differential to find out how big the radius of the universe is supposed to be, and you assume that it started 13.7Gly in radius (say at the end of alleged inflationary period,) and then expanded according to Hubble Constant, then according to my calculations it should expand by approximately another 22.5Gly in radius (every direction). This gives a total of about 36.2Gly radius, which is a lot less than the 46.5Gly calculated for the CMB via red shift calculation.

However, we don't know how much alleged inflation actually happened.

Moreover, the inflation is assuming that the CMB is red-shifted according to cosmic red shift formula from GR...which means if GR is wrong that value is wrong, but since they don't make a direct measure of that value and only produce it from a GR-based calculation, they will never know the difference...
Returners
3.4 / 5 (5) Oct 18, 2015
Official cosmology is based on the presuppositions that 3) redshift is a measure of distance,


Ironcially, the wave/particle duality of light produces a contradiction when trying to calculate distance.

A classical "wave" which is propagating in any direction, and expanding in radius as it progresses, must lose "something" at any given point along the wave, as it expands through space, even without space expanding. Which would mean that red shift is caused by the distribution/smearing of the wave across an expanding spherical shell in space, not by space itself changing.

But in the particle theory of light, the photon propagates in a straight line and experiences no such "smearing" from it's own local motion.

It appears the two theories produce mutually exclusive interpretations of the observations....which is quite problematic since we can prove by double slit experiment that Light, even individual photons, behaves as wave in-transit....
Returners
3.4 / 5 (5) Oct 18, 2015
Moreover, the loss of the "something" in the expanding spherical shell is proportional to the square of distance (Newton) rather than linear distance (hubble constant for alleged space-time expansion).

It is possible to graphically represent why Newton's law correctly predicts the behavior of both an expanding sphere of particles and simply an "expanding abstract wave"...or group of expanding abstract waves (representing wave model of photons).

turns out that for any given distance from the light source, the probability of intersections with your surface area of your detector si the same in both models. The difference is going to be in how you interpret the "red shift" effect.

In the wave model, objects differing from some sort of "unitary distance" (where they break even) would actually be roughly the square root of the distance calculated by the particle model...
Returners
3.4 / 5 (5) Oct 18, 2015
cont...

This would mean, for example, that a Quasar presently believed to be 10 billion ly distant might actually be just 100,000ly distant, a lot smaller, a lot less energetic, and producing light at a totally different wavelength than it is believed to be.

Moreover, the Milky Way might only be ~320ly or so across, instead of 100,000ly across...and shaped a bit differently than it is believed to be as well.
Returners
3.4 / 5 (5) Oct 18, 2015
I guess another way of saying it is if the "wave" is a probability distribution for the "particle", then "information" about the "particle" is smeared out across the expanding surface of the "wave".

This "information" must be derived from the tangibles of the "particle" therefore the "particle" must lose "something" just by moving through space itself, whether or not space is expanding....

This will be viewed as a "Tired Photon" argument, ro some such, but fact is if you observe other real-word waves, such as water in a tank, they behave that way...the more expansion the more energy any given point along the wave loses...
Protoplasmix
3 / 5 (6) Oct 18, 2015
How can be sure that in other regions of cosmic space speed of light is not different than measured speed in our local region?
The answer is "You can't be sure."
No, the answer is, "You can measure it with pulsars." That and your other objections are addressed in lots of places, e.g., here: "Determining Distances to Astronomical Objects"

You know more about being challenged than most, Returners. Pay close attention to "5) Standard objections by creationists" above.
FainAvis
3.5 / 5 (8) Oct 18, 2015
@ Returners This forum is not a place for you to wank at your ego.
jeffensley
1 / 5 (2) Oct 19, 2015
The problem with the DE driven spatial expansion theorized to be the reason we observe galaxies accelerating away is that it cannot be reconciled with local observations, no local verification for "universal" expansion.


I think the potential issue with that statement is that we are talking about very different scales... I would hypothesize that the red-shift associated with expansion on the local level would be so miniscule as to be undetectable. When you take the same phenomenon and expand it to outside the galaxy then it becomes more noticeable. Believe me, I'm not necessarily sold on the utilization of red-shift as a directional movement tool (recent research about star classification casts doubt on SOME of it). I would be curious to know if we have noticed increases in the wavelength of light over time for a single object. That may be telling.
Bigbangcon
1 / 5 (1) Oct 24, 2015
@Returners
["Official cosmology is based on the presuppositions that 3) redshift is a measure of distance,
Ironcially, the wave/particle duality of light produces a contradiction when trying to calculate distance."]

The following interpretation of the quantum phenomena may help: http://www.ptep-o...9-03.PDF

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