How could the universe expand faster than the speed of light? That seems impossible!

- asks Paul

By | Posted July 9, 2007
Posted in: Ever Wondered?, Physical Science
Tags: , ,

In science fiction universes, traveling the galaxy is a snap – just engage the “warp” or “hyperspeed” drive, and off you go, cruising the cosmos at several times the speed of light. But back in reality, we’ve all been taught that the speed of light is a strict traffic law that can’t be broken. This is true, but slightly misleading.

Einstein’s theory of special relativity, first published in 1905, asserted that the speed of light is a constant (300 million meters per second), no matter who measures it. It’s always the same whether you are in motion or at rest. This line of thinking is a lot different than we’re used to experiencing. For example, if you try to measure the speed of an oncoming car from a moving vehicle, you end up getting the combined speed of both cars. This is why cops have to stay parked. Light is different, because no matter what you’re doing it always goes the same speed.

The speed of light affects us more than we realize – it helps us understand the difference between cause and effect. If things could move faster than the light we see them by, we’d be in for weird experiences. If you were a catcher trying to catch a superluminal fastball, you might feel the ball hit your glove even before the pitcher starts his wind-up: The effect before the cause. That’s because the image of object would be traveling at the speed of light, trailing the faster baseball like the slower sound of thunder trails after the image of lightning.

Now that we have a taste for Einstein’s theory, we know that baseballs don’t go faster than the speed of light. But is there anything that can? It turns out that the speed of light is only a limit on objects – like baseballs – as they move through space. The movement of space itself, however, can make the speed of light seem slow.

Right after the Big Bang, the universe had a monstrous growth-spurt called inflation. The whole thing was over in less than a trillionth of a trillionth of a second, but the universe grew exponentially in that brief blip, repeatedly doubling in size. At the end of inflation, although the universe was still smaller than a car, the outer edge had traveled many times faster than the speed of light. Since then, the universe has continued its expansion, but at a more reasonable, steady pace.

This ultra-fast growth seems to contradict what we’ve just discussed, but it makes sense if you understand the distinction between expansion and motion. When astronomers say that the universe is expanding, they’re talking about the rather abstract concept of space-time. Basically, space-time is the three physical dimensions of our existence-length, breadth and depth-combined with the additional dimension of time; think of it as a wire grid that connects every part of the universe to every other part. When we say an object has motion, we’re referring to its change in position relative to the space-time grid. The speed of light is only a constraint for objects that exist within space-time, not for space-time itself.

To better visualize the theory, astronomers often illustrate the expanding universe as a loaf of raisin bread rising in the oven. The raisins are galaxies and the rising dough represents space-time. As the dough expands, the raisin galaxies find themselves farther apart from each other, even though they are not moving relative to the dough between them.

Now let’s imagine that there’s a beetle in the loaf and it starts crawling toward a faraway raisin (don’t worry- we’re not going to eat it anyway). The beetle represents anything within space, such as baseballs, spaceships or photons. When the beetle burrows through the bread, he is moving relative to the dough, and all the other raisins. The speed of light limits how fast the beetle can travel, but not how quickly the bread can rise. Just because the expansion of space can break the speed limit, it doesn’t mean that we can go faster than Einstein said we could.

So, while the speed of light remains an unbreakable barrier for those of us within the universe, it can’t limit the expansion of space-time itself. The universe keeps right on expanding, but the speed of light limits how much of it we can see, and how fast we can move. It may not be fair, but that’s physics.

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  1. Joshua Romero, thanks for your article. I think it clears up a lot of confusion, at least in my mind, by emphasizing that the distinction between motion and expansion must be appreciated.

    WWJ, April 27, 2015 at 5:49 am
  2. tony, that is the paradox of tachyons, flowing backwards in time from the particles destruction to the end of their existence their birth. these particles also defy the light speed limit…but alas in math they can exist. but in reality they they more than likely dont. the only thing, which doesnt actualy move faster than light, but does some how comunicate faster than light is quantum entanglement, which is just as strange if not stranger than space time.

    greg s, May 12, 2015 at 4:55 am
  3. @gregs, what am trying to say is that no matter how weirder things get out there. I dont believe you can ever, ever get an effect before the cause.

    tony, May 27, 2015 at 7:12 pm
  4. i agree tony. effect before cause seems illogical to me too. thats the reason i pointed out the paradox of the tachyon. i dont think tachyons exist either. yet head scratchingly true (its been theorized and then proven) quantum entanglement is real. going faster than light also begins to change how energy is used. if you are travelling faster than light rather than adding energy to go faster, you remove energy to speed up and add energy to slow down. usually i would add an explietive because lets be clear on this, its well fudging mad. well back to the poor tachyon r i p i loved you in science fiction…. (wipes a tear from eye at the passing of the tachyon)

    greg s, May 31, 2015 at 4:33 pm
  5. Well Greg, sorry for your loss. And thanks for pointing that out to me. But if effect before cause seems illogical to you, that means your perspective on things are about what things seems, and not what they are.The paradox of the tachyon sounds simple and seems possible, but if you think about it realistically, you know it can’t happen. Am more about what is, not what seems like. Alot of stories can be concocted by what seems like just like in science fiction. I know you like science fiction.

    What am trying to make you understand greg is even if two people could communicate among themselves using tachyon device and it seems from ones perspective that he got a response before the othe sent the signal this is never actaully the case, it merely seems to them as the case because of relativity. But realistically it can never happen. Thats why i have trouble with what seems like. If you add a third observer that is outside the equation from the other two. He will tell you how things are and not what it seems like.

    tony, June 5, 2015 at 5:20 pm
  6. See just like you greg I dont believe in the paradox as well.

    tony, June 5, 2015 at 7:22 pm
  7. The law of cause and effect does not exist.If you go back to God and he allways existed you have an effect without a cause,same accounts for the beginning of the universe how and whatever it may be,you allways end up with an effect without a do you have some effects today that do not have a cause?? Scary!!!.

    willy gauchew, June 14, 2015 at 2:56 am
  8. In the 5th paragraph of this piece, the author states that the universe continued at a “constant steady pace”. This is wholly inaccurate as it was discovered by mr Hubble(yep..that hubble)that the universe is actually “Accelerating”. Which has been a major mystery even to this day( for which I have a very practical but controversial theory, that does not include dark matter.)
    is the formula that proves the acceleration..

    If anyone knows how to publish a scientific paper properly, I would appreciate an email and some help. ( not financial, only academic) thank you.

    Marcus Jetson, June 20, 2015 at 11:43 pm
  9. I would like to put forth the idea of time dilation with respect to the raisins in the loaf of bread. My thought is that those raisins depending on their own positions relative to massive objects are stuck in gravity wells that slow their time relative to the rest of the universe. The thought is that while we see objects in the universe based on the light we receive and make measurements from that light have we truly accounted for the dilation of time with respect to how the light got to us in the first place? What if we have been in a gravity well here on earth that dilutes time for us, slows it down, relative to objects out in the universe such that they our perception of them is that they are much further away than they really are or some other scenario?

    Ben, June 23, 2015 at 8:28 am
  10. u guys hav not considered the human mind to be anything or u would have speedily grasp the fact that the human mind is the fastest entity in existence for now anyway

    BKS RAY, August 18, 2015 at 5:16 pm
  11. I’ve been watching How the Universe Works and it led me eventually to here. My mind is well and truly blown. I was aware of these concepts, but when you actually have them explained to you by people who know what they are talking about it is incredible. I really feel like going back to the planetarium. Thanks so much for the fascinating discussion.

    iamdamo, August 22, 2015 at 11:41 am
  12. How can we see ANYTHING in the sky, if we’re moving away from it faster than light? But we can. Ergo we’re not.

    Joe, September 8, 2015 at 8:18 am
  13. Dear All commentators,

    I myself agreed with your commennts, but the question is this, which is begin to create me mad mad and mad, how the Sciencetist assume the speed, about the Big bang, what is Big Bang,how it started, while there was nothing, let suppose, there was abig black hole, what was beside and inside the hole?
    no body have perfect answer, am I right, now how big bang started without any molucules or elements, how its collied with each other, which one, is the big bang automatically create the sand soil,rock gases, air and every thing which we are discovering gadually after experiment.Everywhere about the Big Bang, but actually no body can explain about big bang, how the big bang started, which elements, molucles or something else force for big bang, is big bang create it self the soil rock,star, sun moon, gases,earth and other live things even water and gases, so it is clear now that before big bang there were every thing may be in black hole and God created the big bang to make the universe.The formula=There is nothing= to nothing, if there is something, resulting something, these topic s are foolishness, and just making fool himself who thinks about how create the universe, , I question you, which power create the big bang? wjhich elements or molucules in big bang, from where those elements or molucles came?, have you any solid answer, no never, so my dear, now faith upon God he is almighty, and notjhing else, he is from the very begining even before big bang , name of God started from where when our thinking reached up to end, but there is a super power, name God, so do not go against the nature or God,big bang not create the man,animal, wild and each and every things on earth even on another planet, which we do not know, and never can reach up to there, even the NASA build the engine more faster i.e the speed, billion miles per second or trillion miles per second. we just create to pass our life as the almighty God bestow us his book Bible, Quran Sherif, and send the prophet time to time to teach us the truth and fact, we can not comapare our self Nauzbillah with almighty God,our thinking is finished and his nature sart. No doubt God mentioned in his Quran that I made every thing for you you find out for the sake of you, but it does not mean,you discover about me nauzbillah, what was before God, what is over the sky, where the end of the universe,how I create the things, man animal trees, and each and every things,These are the evils thinking, he ever tried to humen against almighty God, and the foolish men think all the time about these foolish things.Big Bang, I myself do not believe, we jus assume no evidence, no prove.

    B.Tariq Iqbal, October 8, 2015 at 8:29 am
  14. B.Tariq Iqbal, whatever we cannot comprehend, we attribute it to God. No wonder it is the most exploited term in any language. Sadly for you, science does not work that way.

    Lol, November 27, 2015 at 10:51 pm
  15. at the speed of light, 0 really is the value of every governing factor. so my question is this. 1. how did the universe slow down? at the speed of light you need to remove energy, but there isn’t anything to remove because all factors are zero (or infinite) ? 2. did the universe shed nearly all its mass to slow down? 3. do i win a fiver? that last one was a joke

    greg s, December 5, 2015 at 7:39 am
  16. one more thing though, a being without mass could in theory be at the speed of light, and more importantly be everywhere. (i’m an atheist by the way). an omnipotent being without mass could have generated what we observe, but still be out of our plane of sight. we dont see light, but we do see what it effects. that is the molecules and atoms it bounces off of, passes through etc. i dont personaly believe, but hey logicaly it is up for debate (even if it is/is not hokum).

    greg s, December 5, 2015 at 7:48 am
  17. speed requires a relative point in space in order to be measurable. and acceleration requires a fixed starting point. so how can the big bang, or expansion, have a speed? how can it have an acceleration? everything we know of physics tells us that the big bang is impossible

    jeff k., December 15, 2015 at 8:03 am
  18. Here’s something else I struggle to understand. I read that the Hubble telescope can see light 10-15 billion years old. The Hubble Deep Field is apparently light from objects that took that long to reach us. So if the Universe is approx 15B years old how did those objects get 15B light years away from here if the Universe has been expanding all this time? Does this mean it ‘inflated’ almost instantly to 15B light years across and has only been slowly expanding since then? I read somewhere that it could inflate above light speed because time-space didn’t exist until after it happened so the limits don’t apply. Sounds a bit like a neat trick to stop the theories falling apart to me!

    Robin R, December 16, 2015 at 5:05 pm
  19. I agree with you Robin.what worries me is when did the law of cause and effect come into being? If it was always a law then something must have caused the big bang,but then what caused that something etc. is cause and effect the samething? Then where does time come into the picture? Which means that an effect will always in turn become a new cause!!!! which in effect means there is no beginning and no end?

    willy gauchew, December 18, 2015 at 12:39 pm
  20. The speed of light is zero.
    In the beginning all energy was used for moving in all directions at the same time ,so relativity did not exist.when some matter here and then slowed down some of the energy became available for other purposes and relativity was born.
    Those particles that came to a compled standstill became light,and the rest of matter moved away from it at its origianal relative light is not moving at all,

    willy gauchew, December 21, 2015 at 9:38 pm
  21. In the beginning all matter was moving in all directions at the same time (inflation) all available energy was used for to an observer it would seem as though nothing was moving,relativity did not exist.
    Then some of the matter slowed down using some of its movement energy to slam on thus changed its relative position to the rest of matter that was using all its energy to move (relativity came into being)
    To an observer it would seem as though the matter that had slowed was the one that was moving,because it was changing its relative position to the rest that was all moving in the same direction at thesame speed.
    If a particle had to use all its movement energy and slow down to astandstill ,the rest of matter would be moving away at the maximum speed.ln other words the speed of light. I therefore make the point that the speed of light is used up all of its energy to put on the brakes and come to a standstill i therefore postulate that light is standing still and the rest is moving away.
    Opinions please.
    Willy Gauche’

    willy gauche, December 22, 2015 at 2:14 am
  22. In the beginning all the energy of matter was used for movement at the so called speed of light.
    For some or other reason some of the matter used some of the energy to produce heat and slowed down creating the illusion of moving away from tne rest of the matter.(relativity was thus created)
    Photons changed all the energy used for movement into light thus coming to a total standstill.the rest of the matter kept on moving away at full speed.(the speed of light).
    An observer would not know that the photons were standing still and the rest were moving away at the so called speed of light.
    So light is standing still and the rest of matter is moving.
    Any opinions please

    willy gauchew, December 22, 2015 at 3:03 pm
  23. Special Relativity is called “special” for a “special” reason ya know!!!! :-D What does E=mc2 really calculate, after all? What is “c2” anyway?

    Kevin Almaroad, January 13, 2016 at 10:34 pm
  24. Should we not do as Albert said, and “simplify” things to their simplest form? Even things he didn’t get around to simplifying? Should the equation not be simplified to E=md? Not that the mathematical value of the numeric variables change, only the description to what it really is, c2=d.

    Kevin Almaroad, January 13, 2016 at 10:39 pm
  25. The argument between classic and quantum physics is, “classic says there was a Big Bang, quantum suggests that there was no Big Bang, that the Universe had no beginning, that it always has existed in a sense of time.” Which of these is correct? The answer, BOTH are correct. But how can this be? Easy! Postulate! :-D

    Kevin Almaroad, January 13, 2016 at 10:49 pm
  26. And why does so much Dark Energy exist, more than existed at Big Bang? Common sense here on this one LOL!!!

    Kevin Almaroad, January 13, 2016 at 10:54 pm
  27. I have not read the above article because I don’t have to. The answer to the question in the title is: the special relativity applies to the material universe. The universe may expands in excess of speed of light (inflates) but does not expand in anything. Outside the universe is nothing, no any space. Outside of the universe does not exist. With expansion space is created. The relativity theory does not apply to the edges of the universe.

    Two years ago I posed a hypothesis of a grain-structure photon (provided on my google+ website) that explain ostensible expansion of the universe as well its acceleration with time. To me, grain-structure photon eliminates any expansion and makes cosmological model much simpler (and more reasonable to me).

    Andrzej Baniukiewicz, January 15, 2016 at 3:00 am
  28. Kevin Almaroad: If you have a contribution, then contribute. Are you serious in asking what is E=mc2? What is c2? If so, then take intro to physics and learn. If not, what is your point? Special Relativity expresses the relationship between energy and mass, that each can be expressed by the other in terms of the speed of light per second per second.

    Einstein did not mean simplify by substituting one connotation for another. c = speed of light. In his formula, c2 means the speed of light x the speed of light. Substituting d for c2 is not simplifying — rather it makes things messy as one would have to know to calculate the square root of d to understand that the relationship concerns the speed of light.

    Big Bang does not distinguish classic theory vs quantum mechanics. Classic/relativity theory concerns atomic values (from atoms to galaxies) while quantum mechanics concerns the intra workings of atoms (quantum = small + mechanics = workings).

    Now, pray tell, share your great wisdom of postulating common sense to explain the origins of the universe and the energy that makes it exist. Share with us lowly humanoids that which Einstein failed to explain to us yesteryear and what the Stephan Hawkings of today still fail at understanding. Clearly, you have a great intelligence that surpasses us mere mortals.

    BTW, if God is your answer, then please give us an ignostic definition of God (as in, not “the Bible is so because the Bible says its so” definition of false logic).

    Mike in Asheville, January 18, 2016 at 3:55 pm
  29. Very very disappointed. This used to be the most epic article and thread on the internet with 100’s of replys. Please I beg you, restore this thread in some form so as to respect all contributions to it. Today was the day I was about to link this article to a website. Not now in it’s current edited form. Thank you.

    Mind Blown, January 25, 2016 at 12:57 pm
  30. while spacetime can behave anyway it wants what you said about galaxies moving apart and spacetime expanding faster than light should have been applicable to the space time between the earth and moon or the earth and sun? logically we should be able to detect the distance changing over the last 5 billion years, but it hasn’t therefore that “theory” doesn’t seem to be viable

    anthony marino, February 6, 2016 at 6:07 am
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