How Can We See Galaxies 47 Billion Light Years Away When the Universe is Only 13 Billion Years Old?
This is my second post in the Just Science Week Challenge.
This 2003 paper in Physical Review Letters puts a lower limit on the size of the universe at no smaller than 46.5 billion light years in radius. If the universe is geometrically flat, that is.
In this video I made on the Hubble Deep Field, I mentioned this number and was immediately inundated with questions and comments from people screaming that that number could not possibly be correct. How can the universe be that big if the fastest anything can travel is the speed of light? The universe simply CAN’T be larger than the distance light travels during age of the universe, right?
Wrong.
It is true that the universe is 13.5 billion years old, and it is also true that nothing can travel faster than the speed of light. But it does NOT follow that the size of the universe is simply the distance light traveled in 13.5 billion years. You can’t stop there. Why?
Because the universe is expanding, and has been for 13.5 billion years.
Remember yesterday’s post? Everything in the entire universe is flying away from each other at a rate linearly proportional to its distance. That’s Hubble’s Law. The distance that light has to travel over time is continuously getting bigger and you MUST take that into account.
Technorati Tags: cosmology
Remember in my last post, we’ve established that the universe is expanding at roughly the Hubble Constant, and that number is a function of time. It matters WHEN you take your measurement of the redshifts of far away galaxies. Right now, the universe is expanding at about 71 km/sec/Mpc and is accelerating.
A somewhat simpler way to think of the expansion rate of the universe is that it expands at roughly the age of the universe to the 2/3 power: AgeOfUniverse^(2/3). Unfortunately, it’s not simply a plug and chug formula, since the expansion is occurring continuously, you need to apply some calculus. Here’s the formula, but I’ll go through a simple example a little later:
Illustration Credit: Ned Wright
The above integral just takes the ratio of elapsed expansion time to the age of the universe raises it to the 2/3 power and does this over the entire time the expansion is occurring.
What all of this means is that whenever you discuss the size of the universe, you need to apply a scale factor that is relevant TO THE TIME you are interested in. The issue of when is very important because the size of the universe, and the rate at which it was expanding has changed since the universe began.
So, for RIGHT NOW, the size of the universe has expanded to roughly 46.5 billion light years since the Big Bang.
Let’s break down the above integral into some smaller intervals and watch what happens. Let’s use 13 billion years as the age of the universe and let the universe expand for an average of five billion years at three different points in time: 2, 7, and 12 billion years after the Big Bang:
- At age of universe = 2 billion light years: the universe has expanded by a factor of (13/2)^2/3 = 3.48
- At age of universe = 7 billion light years: the universe has expanded by a factor of (13/7)^2/3 = 1.51
- At age of universe = 12 billion light years: the universe has expanded by a factor of (13/12)^2/3 = 1.08
So combining these scale factors over the two intervals above, the universe has expanded to a size of:
(average distance light travels over interval of interest) * (sum of all scale factors).
Plugging in the numbers (we used an elapsed time interval of 5 billion years):
(5 billion light years) * (3.48+1.51+1.08) = 30.37 billion light years.
The 5 billion light year number above is the average distance light traveled in 5 billion years so the units are in light years.
Now, this is a discreet example, taking only three points in time, but already we have a number bigger than 13 billion light years. Since the universe is expanding continuously, we actually need to do the integral above and when you do that, the answer approaches 47 or so billion light years.
Actually, this is a little misleading, the number cited in the above paper does a different analysis and I’m doing something a little different that what the authors of that paper did, so I’m trying to make a number fit that was derived using different techniques in my example above and it won’t work out that way. Still, the end results are similar and nothing is really lost by doing that.
But, ignoring the details for a minute, what I’m really trying to do here is show that the size of the universe isn’t simply the light travel time over the age of the universe. The expansion of the universe requires that you apply a scale factor as outlined above.
If the math is confusing you, just remember this: that scale factor is important. It accounts for the distance the universe has expanded over the time period you’re interested in. It doesn’t go far enough to say that the size of the universe is simply the distance light travels over the course of the age of the universe. Since the creation of time, everything has gotten farther apart, remember Hubble’s Law: everything is speeding away from everything else, all the time.
So, when the Hubble telescope took the deep field images, it provided us with the deepest views we’ve ever seen into the universe. Those galaxies were approaching the farthest edges of our cosmic home, and they weren’t 13.5 billion light years away, they were much, much farther.
UPDATE: Here’s a good graph I found on Universe-Review.ca, they have kindly given permission for me to post this.
Illustration Credit: Universe-Review.ca
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POSTED IN: cosmology
49 opinions for How Can We See Galaxies 47 Billion Light Years Away When the Universe is Only 13 Billion Years Old?
r06u3AP
Feb 12, 2007 at 8:37 pm
You have provided us with an excellent description of why the SIZE of the Universe is greater than 13.7 Glyr in radius. But the size of the Universe is NOT in dispute. The scale factor due to the expansion is WELL UNDERSTOOD (at least, I THINK that I understand it.)
But you entitle this article “How Can We SEE Galaxies 47 Billion Light Years Away When the Universe is Only 13 Billion Years Old?” and your final paragraph states:
“…the Hubble telescope … provided us with the deepest views we’ve ever SEEN … Those galaxies were approaching the farthest edges of our cosmic home, and they weren’t 13.5 billion light years away, they were much, much farther.”
I really don’t think so, Tony!
The argument is about what is “OBSERVABLE”. OF COURSE there are objects out beyond the horizon! OF
COURSE they’re greater than 13.7 Glyr away. But do we actually see them? NO! That’s why it’s an event horizon! There’s only been 13.7 Billion years worth of time for ANY electromagnetic emission from ANYTHING to travel across the Universe, regardless of the geometry and regardless of the
expansion.
Let’s see if I can simplify the problem. Let’s call the age of the Universe a “Cosmic Epoch”. Let’s further say that there are two objects, shortly after the big bang that are relatively close to each other. Now, follow what happens as the expansion pulls them apart to a distance of
2 light-epochs from each other. The expansion is nearly constant, but since more and more expanding space is being added between them, the rate at which they separate accelerates as time marches on until they each go beyond their mutual event horizon, when their velocity relative to each other exceeds the speed of light. Just prior to that point, cosmically speaking, the image of one as seen from the other is just 1 Cosmic Epoch old and is doppler shifted down far into the microwaves if not lower. It’s just like watching something fall into a black hole approaching the horizon.
So, there is obviously no way that the image of one object as seen from the other object can ever be greater than 1 epoch old; the universe has only been around that long! Which is also why you will never ever observe anything beyond the cosmic event horizon, which must >> of necessity
tony
Feb 12, 2007 at 10:26 pm
@r06u3AP:
Excellent comment. Thanks for taking the time to leave it, I really appreciate it.
I used to argue the same thing, until I read some texts and discovered that we can actually see these things from these distances.
I will admit, that this topic is stretching my writing ability, so let’s see if this helps (taken from Ned Wright):
“Another way of seeing this is to consider a photon and a galaxy 42 billion light years away from us now, 14 billion years after the Big Bang. The distance of this photon satisfies D = 3ct. If we wait for 0.1 billion years, the Universe will grow by a factor of (14.1/14)^2/3 = 1.0048, so the galaxy will be 1.0048*42 = 42.2 billion light years away. But the light will have traveled 0.1 billion light years further than the galaxy because it moves at the speed of light relative to the matter in its vicinity and will thus be at D = 42.3 billion light years, so D = 3ct is still satisfied.”
The key phrase there is: light is moving from the distant galaxy “relative to the matter in its vicinity”.
Taken from Ned Wright’s Cosmological FAQ:
http://www.astro.ucla.edu/~wright/cosmology_faq.html#DN.
He is talking about the integral that I left above (which was also taken from his FAQ).
Does this help?
Thanks again for leaving that comment!
tony
Feb 12, 2007 at 10:31 pm
@r06u3AP:
BTW, what’s the story behind that handle? It is quite unusual, I’ve been trying to figure it out, but I think it’s an inside joke or something, I’d have to know you to get it.
r06u3AP
Feb 13, 2007 at 1:14 pm
You are very perceptive, the handle is a whimsical sort-of inside joke. The hacker-esque “R06u3AP” refers to unauthorized wireless Access Points sometimes installed by people for convenience at their workplace, unbeknownst to their boss. The trouble with doing that is that they expose the company network and everything on it to unauthorized access by others outside the facility. Hence, they are termed “rogue AP”s. As a worker in the IT biz, dealing with wireless networks and the detection of such rogue APs, I thought it made a neat handle.
BTW, I noticed that my original comment didn’t post in its entirety, I don’t know if there’s a limit or if you cut it off. In any case, I’ll attempt to post the rest of it here:
…..Which is also why you will never ever observe anything beyond the cosmic event horizon, which must >> of necessity
r06u3AP
Feb 13, 2007 at 1:15 pm
ALWAYS be 1 light-epoch away in all directions, receding from the observer at the speed of light.
To see anything more distant would require that the light from it travel backward in time! If there is any other way for EM radiation of any wavelength to have travelled for longer than 13.7 billion years in our Universe, I certainly cannot see how.
If I’m wrong, just shoot me, because the reason I’m wrong must be totally beyond my ability to comprehend.
I also have a problem with the article “Constraining the Topology of the Universe”. Now, maybe I’m just not smart enough to get my head around all the fancy math and all but I always thought that EM radiation obeyed the principle of superposition such that even if you do have patterns of the CMB sky repeating around the 2-sphere they would necessarily have to combine additively(?) with what is naturally there to begin with thus yielding an essentially random pattern with no detectable repetition anyway. But I admit, I am by no means a brilliant degreed cosmologist so I’m sure that those more learned than I would surely have thought of that all too obvious hitch and clearly knows how to extract random patterns out from, uh….., random patterns???
Huh? Oh well, like I said, just shoot me because I’m just too dumb to understand it.
Astronomy Buff - Universcale: A Flash App to Put You In Your Place
Mar 31, 2007 at 1:25 am
[…] up to the size of the universe, which sadly, it reports as 13.7 billion light years. The actual value is closer to 46.5 billion, but who cares, right? Big is […]
Astrolink [Global Edition] » Universcale: A Flash App to Put You In Your Place | Latest astronomy news in 11 languages
Mar 31, 2007 at 5:29 am
[…] up to the size of the universe, which sadly, it reports as 13.7 billion light years. The actual value is closer to 46.5 billion, but who cares, right? Big is […]
100 Billion: The Only Number You Need to Know About the Universe
Sep 27, 2007 at 2:08 am
[…] concepts that were really pushing the boundaries of what we know or can even visualize (e.g. the size of the universe). I see now that I should take a slightly different tactic in my writing when it comes to certain […]
Dominic
Dec 2, 2007 at 11:14 pm
I’m just curious,if the big bang happened hurling our matter (planet) at the speed of light and then a millionth of a milisecond later there was a flash of light we would never see anything untill we slowed down to sub light speed relative to said light,so how can anyone know for sure how old any observed light really is without knowing how the universe accelerated or decelerated relative to the singularity?
James Dunn
Dec 30, 2007 at 10:09 am
I only have a trivial understanding of what is currently known about the Universe. However.
1) My problem with your supposition is that we are using a scale factor as a fudge factor.
2) The Hubble Telescope can detect energy that appears to be coming from beyond the limits of the distant galaxies it can see. So the size of the Universe is not known as yet.
3) The apparent expansion of the Universe is not as yet conclusive.
4) After the supposed Big Bang (interesting support, but still a theory), as the energy masses formed varying densities as the energies raced out into space (assuming for the moment that nothing travels faster than the speed of light, even though we now know that is not true; see “entangled pairs”) the energy bundles would dominantly be moving under the speed of light. Since mass at the speed of light supposedly is infinite mass and we would be living in fluidic space.
If the mass is escaping at a rate that continues to allow accelerating expansion, then at no time would the masses have slowed down. Unless there were multiple forces involved that acted on the masses non-linearly. As such, no simple calculation would explain the age of the Universe.
As I said, I only know a trivial amount regarding the Universe, but the supposition that the Universe is of any specific age seems to be nieve given all the variables we do not know about.
With respectful guarded interest,
James
dagnome,I think you’re referring to the estimated size of the uni… | Susuto
Mar 29, 2008 at 1:28 am
[…] old. Remember that the universe is expanding, so distance to furthest object!=age of universe. See http://www.astronomybuff.com/how-can-we-see-galaxi … for an explanation, or, if you don’t trust that source, google for […]
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cosmo
Sep 4, 2008 at 3:07 am
There is a simple reason why the scaling has to be taken into account, and while it’s true that you can say that a galaxy is “12 billion light years away” in our frame of reference, you have to remember that its redshift indicates (roughly) also how much space has expanded since the light was emitted by the galaxy.
Here 12 Glyr is just a measured distance in time, not necessarily in space. While the light has takes 12 billion years to reach us, space has expanded since then. There is no real limit to how fast space can expand, though c is the maximum speed at which any information can move within space.
Thus you can suppose that the object which we see at 12 Glyr is actually at 46 or more Glyr. It’s just looking at the same thing from a different point of reference. There’s no problem there, it’s all plain and simple general relativity.
DragonOak
Sep 4, 2008 at 6:09 pm
It boggles me mind…….my head hurts
Charlie Shread
Sep 4, 2008 at 6:10 pm
Hi, to put it in simple words: my opinion would originally be a state-the-obvious in that it is impossible to see anything older 13.5 billion years away, because there was no light created before that time. Is this not true?
But then again, you have almost made me reconsider this opinion with light traveling at a speed relative to other mass near by, which would mean you could see things further away. But I guess that also means that light has moved faster in our perception of time? This surely breaks the law that light has a constant SPEED (Distance/TIME). So I am a little confused at the possibility of light reaching us from further away than the age of the universe is. Please could you shed light (hehe) on these queries. thanks,
Charlie.
Si7ver6
Sep 4, 2008 at 9:30 pm
How do you know how fast the universe is expanding and put that into a number? And wouldn’t the universe have to be expanding between us and a distant object to make it further away. Is the universe expanding in places other than the event horizon or is the universe streaching rather than expanding? How do you know the universe is expanding at a constant rate? How do you know that the speed of light has keep constant from the start of time? How can you tell the universe is expanding at all? How do you know the age of the universe? Is there a way to mathmaticly calculate the age of the universe or is it a theoretical number? It seems like it would be impossible to prove mathmaticly or scientficly that any numbers regarding the age or size or expantion or anything in general about the universe as a whole or even as a part. Are there things bigger than science or our own minds can understand? If there is the size and age of the universe would be two of them.
Skip Atwater
Sep 5, 2008 at 12:29 am
To get my head around all this . . . by the time the light from an object reaches us on Earth, the thing we are seeing has moved further away from us. Seems simple enough.
Wiz Shack
Sep 5, 2008 at 5:04 am
The universe was never “born”…..based on 1 simple fact. “Matter or Energy cannot be created nor destroyed”
sil-chan
Sep 5, 2008 at 7:04 pm
James Dunn:
You betray yourself with the “it’s just a theory” quote.
A scientific theory is a set of ideas and formulae that describe the known facts about some phenomenon. A theory is a rather sound scientific principle with a lot of proof.
While no theory can be proven in totality, a theory is still not a “guess” as you make it seem with those words.
meiliken
Sep 6, 2008 at 3:39 am
Umm, yes, the universe is indeed expanding and all that jazz, but sorry, there is no way in hguman understanding, unless you’re divine or celestial or non mortal to know the age of the universe, or really existence. Without a common frame of reference, i.e. something before existence, there is nothing to calculate against. So anyone saying they know the age of the universe or existence is full of shit. Go back to the caves hippies, or stop doing drugs.
James
Sep 7, 2008 at 7:22 pm
I doubt the entire universe is expanding. We can only see a piece of it. There can always be something out there further away. We have only 1 perspective of the universe, and that’s from the milky way galaxy, we haven’t been to other galaxies yet. So I doubt such a general conclusion. There can be galaxies further out hiding behind the galaxies in front of your telescope and you wouldn’t be able to see past that.
Pot Head
Sep 7, 2008 at 10:53 pm
So…Basically, it’s like light is trying to walk DOWN the UP escalators? I mean I read all of this, and I understood most of it, but for people that might not quite catch it, would that be an acceptable analogy?
Phil E. Drifter
Sep 8, 2008 at 4:52 am
‘Things’ CAN travel faster than the speed of light, since a.) the ’speed of light’ constant IS a constant because it’s the measurement of how far light travels in one year IN A VACUUM. Scientists have recently been able to ‘fudge’ the speed of light, as well as actually beaming light into (i dont know the word for it) but they’ve actually been able to see the light *arrive at it’s destination* before it’s left.
try wrappin’ your head around that.
Anyway…light follows the predictions of matter and must therefore then have mass, because when astronomers see distant stars ‘wobble’ it is because of the gravitational pull of the planets that then must be orbiting them.
But because light only travels, ahem, at the speed of light, that doesn’t mean things can’t move faster than it, it only means that *we can’t see them moving faster*.
I’m somewhat interested in this discussion, being amazed by the universe myself, so I’m going to subscribe to follow up comments.
AMAZE ME!
Phil E. Drifter
Sep 8, 2008 at 4:54 am
ps: it was a ‘no-brainer’ for me to understand the title question; as soon as I read it I already understood it; things blasting away from each other 13 billion years ago, just as a rough estimate, says we’d be 26 billion light years apart.
Chris
Sep 8, 2008 at 1:49 pm
Ok, really simple question here:
If I just look at an object on one side of the galaxy (A) and an object on the other side (B), are the two objects moving away from each other at more than the speed of light? With my basic understanding of relativity, that surely can’t be possible, as from A’s perspective, B is moving faster than light speed away from it.
Basically I’m asking that if I’m in the middle, and to my right I see an object hurtling away at 0.6c (let’s say), and to my left is another going at -0.6c, surely from the view of one of the objects, the other is going at +/-1.2c relative to it. How can that be possible. It goes over the speed limit of 1c.
For the diameter of the universe (in light years) to be bigger than the age (in years), that would have to be possible, but I don’t see how. Saying, “relative to the matter around it,” doesn’t really seem to solve anything, as what about “relative to the matter on the other side of the universe speeding away from it”?
This is why I don’t feel I can begin to accept your scale factors as a solution (not that I really understand them, but as long as they don’t change the restrictions of light speed, I don’t really see how they’re relevant).
Daniel
Sep 8, 2008 at 10:50 pm
“For the moment, we lack completely the intellectual instruments to envisage in new terms the framework within which we could achieve our goals.”
-Michel Foucault
Greg
Sep 9, 2008 at 1:32 pm
The problem I see with this is the idea of redshift. It is only an assumption that the shifting of the electromagnetic energy observed from distant objects is the result of its movement relative to us. In actuality it is quite possible that this shifting is the result of the distance that the waveforms are traveling. Instead of slowing down the speed of light from these observed galaxies losses its energy indicated by the shifting; that is as an electromagnetic wave looses its energy through time and distance both its frequency and amplitude diminish. Remember space is not a vacuum. The quantum ’soup’ is all pervasive throughout space. The greater the time an electromagnetic wave spends travelling through this quantum soup the greater the potential to interact and loose energy; again both through amplitude and frequency. The so called microwave background radiation is not a remnant of the big band but the source of even further objects, which if its total energies where virtually amplified you would no longer have a dark sky; We would have a bright sky at night, as if the sky was filled with stars. In fact we do have a sky filled with stars completely, but because the distance of these stars and galaxies is so far they shift so far that we no longer see them. There is no end boundary to the universe, we can only see so far because of probabilities, the greater the distance the less the probability to observe.
Asadow
Sep 9, 2008 at 6:14 pm
Hmm… it’s a bit confusing, but first of all we should differentiate 4 things: size of the universe, size of the observable universe, distance to the object when the light which is reaching the observer now was emitted, and distance to the object at the moment in time when it’s light is reaching the observer.
Now:
1. Size of the universe - speed of light has nothing to do with it (at least there is no simple, direct relation). No object can travel faster then light but this doesn’t necessarily apply to the space, right?
2. Size of the observable universe = age * c + expansion factor. Light is LOCALLY traveling with the… speed of light, but as the SPACE itself is expanding, so the effective speed is higher.
3. Distance to the object when it emitted the light we see: will be bigger than c*t (t - relative age of the observable object) because of the space expansion.
4. Distance to the object NOW, when the light it emitted is reaching us: like above + the distance the object went according to the Hubble principle (integrated with Hubble const. variable in time).
But isn’t it that if the light is moving like the traveler going on a moving walkway (like they use in airports) ? We have source galaxy at the fixed end of the walkway (space between us and the galaxy) and we are moving on it (resting relative to the walkway’s surface) - as the universe expands. Now the galaxy emitted a photon (traveler) which is walking on the walkway (the later is actually changing speed, never mind). When the traveler/light is reaching us, the distance between us and the galaxy is bigger than the speed of light (speed of the traveler walking) multiplied by the time it has taken to reach us.
In Special Theory of Relativity all observers would measure the same speed of light, regardless of their relative speeds, but this is not applicable when the space itself is expanding.
Jonathan
Sep 11, 2008 at 1:23 pm
@Phil
The speed of light is a velocity, not a distance, but you are right in that the typically quoted speed (300,000 km/sec) is its speed in a vacuum. That being said, scientists can slow light down by passing it through various materials, but they cannot speed it up. No information, or “things,” can travel faster than the speed of light. Perhaps what you are referring to is the fact that you can slow a beam of light down, and thus beat that beam of light to its destination.
Light does NOT have mass. Photons are massless, but they follow the gravitational curvature of space, and thus are affected by strong gravitational fields. This has nothing to do with orbiting planets, however. See information on “gravitational lensing” for an explanation of light being effected by gravity.
Things in the Universe CAN be farther than 13.7 billion light years apart, due to the inflationary epoch seen on the above graph, but we cannot SEE anything that is farther away than 13.7 billion light years. During inflation, space itself was expanding, and thus objects were flung apart at relative speeds greater than the speed of light. Since space itself was expanding, nothing was actually traveling faster than the speed of light. However, since the Universe is only 13.7 billion years old, light emitted from objects that are farther that 13.7 billion light years away has not had time to reach us yet. Thus, we can see 13.7 billion light years in every direction, and no farther.
Colin
Sep 11, 2008 at 6:23 pm
Please correct me if I’m wrong. It seems you are trying to say the visible light from some distant galaxies were first emitted 13.5 billion years ago (our event horizon) but because of the rate of expansion, some of those galaxies are now over 40 billion light years away from us and moving further away.
Correct? Am I missing something? Thanks for the very intelligent post.
Cheers,
Colin
Symber
Sep 13, 2008 at 11:10 am
This is just a response to r06u3AP, who - while making good points I believe missed one key thing, which is what I believe Tony was trying to point out.
I believe he is saying that the objects pictured in the Hubble Deep Field were indeed 13.5 billion light years away when the light embarked towards Earth… but in that 13.5 billion years that the light was travelling, the actual objects pictured have continued to get farther away to the point where they were about 46.5 billion light years away when the light reached the Hubble telescope.
Common Sense
Sep 13, 2008 at 12:18 pm
scientists don’t know how old the universe really is. that’s why.
Al
Sep 13, 2008 at 1:34 pm
Here’s an easy way to picture it. Take two people Mr. A and Mr. B and put them at either end of a flat escalator measuring 100 ft. Have Mr. A roll a ball toward Mr. B. By the time the ball reaches Mr. B it’s traveled 100 ft. Now Start the escalator traveling toward Mr. A at half the speed that Mr. A rolls the ball. The ball has to travel 200ft before it reaches Mr. B 100ft away. Lastly add a constant acceleration to the escalator and have Mr. A roll the ball to Mr. B. You can do the math.
zboson
Sep 13, 2008 at 1:42 pm
Well, here, try this. Suppose light left a galaxy 5 billion years ago about the time our sun was being formed. We see the galaxy as it was 5 billion years ago. But, where is the this galaxy right now? 30 billion light years away according to the above calculation by the OP. Light leaving this galaxy today will arrive at our solar system (or where our solar system used to be) in 30 billion years.
Al
Sep 13, 2008 at 1:52 pm
Sorry to post twice here,
Phil:
Things with mass cannot move faster then the speed of light. As velocity approaches the speed of light, mass approaches infinity (see Einstein’s Theory of Special Relativity.) Since the universe does not contain infinite mass it is impossible to travel faster then c. Also, since energy = mc^2 that means that it would require infinite energy to accelerate anything with mass to c. The universe doesn’t contain infinite energy either. But since energy and matter are the same thing in different forms it really doesn’t matter.
Traveling faster then c doesn’t really mean traveling faster then c. We know pretty much nothing of the universe. Discovery and Technology are exponential. Sometime in the future we may be able to say… fold space, make the speed traveled 0 but the distance traveled quite a long way. But in the end anything with mass can never travel faster then the speed of light and speculation lays in the fiction part of science.
lulu
Sep 15, 2008 at 10:02 am
fuckin nerd, you rule!
tim
Sep 15, 2008 at 3:46 pm
what a dumb page. the answer to the original question is simple… the question is meaningless.
the idiot who asks the question thinks that light ‘years’ are measurements of time instead of disance. the question is fallacious.. exactly like… ‘how can london be 200 miles from liverpool when it’s only 3 hours since i had breakfast’
Jack Jaeger
Sep 18, 2008 at 6:17 pm
The universe is expanding into what?
hede
Sep 19, 2008 at 1:21 am
Your logic is flawed. We wouldn’t be able to see galaxies which are 45 billion years away if the universe wasn’t older than 45 billion years. Because these 45 billion years far galaxies’ light takes 45 billion light years to reach us ergo universe is older than 45 billion years.
Vlad
Sep 21, 2008 at 12:06 am
I became outraged before I even finished the article but wanted to see where it was going. Then it turned out that the very first post was talking about the issues I have with this article, so I will only contribute to it without restating what has already been said. So r06u3AP, no need to die, you’re absolutely right, I have been interested in astronomy since I learned how to read and have taken 2 years worth of astronomy courses in University of Toronto with professors who have been working among other things on research such as expansion of the universe, observations of the hubble, detecting the weakest of energies from outer space, etc. Tony, way to confuse us with your explanations and changing the subject… Going in chronological order, Dominic, we were never moving at at a speed of light, and especially relative to anything else. Funny you should use the word relative, since it is the theory of relativity that states that something magical happens as you approach the speed of light - time slows down, matter turns to energy, etc. One of these effects, the time change, will make sure to compensate for the fact that something else might be moving away in the opposite direction at the speed of light - it wont appear as such, physics as we know/percieve it breaks down. As for knowing the age/distance of observed light, astronomers know it with astounding precision using many fairly straightforward tools such as the doppler shift. Unfortunately I can’t for the life of me recall the whole procedure, but I’m sure if you look up this information you will find it in a breeze. Now James… oh James, “2) The Hubble Telescope can detect energy that appears to be coming from beyond the limits of the distant galaxies it can see.” The energy the Hubble detecs IS what it can see! “3) The apparent expansion of the Universe is not as yet conclusive.” The only thing not 100% conclusive is whether it is slowing down, accelerating uniformly, or speeding up. And even then, there is most evidence for the speeding up scenario, e.g. doppler shift again. “4) After the supposed Big Bang (interesting support, but still a theory), as the energy masses formed varying densities as the energies raced out into space (assuming for the moment that nothing travels faster than the speed of light, even though we now know that is not true; see “entangled pairs”) the energy bundles would dominantly be moving under the speed of light. Since mass at the speed of light supposedly is infinite mass and we would be living in fluidic space.” WOW - so you consider Big Bang, expansion of the universe, theory of relativity (nothing travels faster than light), and the fact that in your words “unless there were multiple forces involved that acted on the masses non-linearly” all just supposed propositions, but the far-fetched, new, theory-in-progress idea of entangled pairs as something “we [] KNOW [] is [] true”? And what is with mass at the speed of light being infinite mass? It isn’t, it just turns into energy, IN THEORY. The next thing you said is the most amusing “fluidic space”, at first I just thought “what the hell?” Then my Sci-Fi fan girlfriend laughed, it’s from Star Trek… Phil: now I don’t know at all what you’re talking about (in a good way), but I wrap my head around what you said by thinking maybe there was more than one scientist involved and/or there were devices at the other end to detect the light, I don’t think one guy sent a beam and ran to the other end to catch it… Also, what does seeing stars wobble have to do with the fact that light has mass? I apologize to anyone offended by my comments, it is just the way I talk, I’m an asshole, but I also feel like people need to have a better understanding and a broader idea about subjects before they talk about them, and especially write about them, listen more and talk less. Take a course in university and get the info first hand from the people that are involved in research thenselves - my prof was the guy that led the research in antarctica 3-4 years back (hope that’s enough info to google). Internet is a wonderful place except that you can’t believe most things on it because of, well, shit like this (just a figure of speech). Looks legit to most folk…
Chris S.
Sep 21, 2008 at 4:32 am
The age of the universe is about 13.5 Bn years, meaning we can’t “see” any further away than the 13.5bn light years, IF the universe was static.
However, Just for simplicity of explanation - assume the following, and it might be easier to understand how things relate:
Two cars (galaxies) are sitting next to each other, parked, at a distance of 100km. The speed of light is 100km/h, and hour universe is 1 hour old.
For us to see the light from the other galaxy, we would have to wait 1 hr for the light to travel 100km.
Now, assume that we instead have a universe that is expanding at a constant speed, meaning that the cars are driving away from each other at 10 km/h.
The light begins it’s travel from the observed car at a given point in time (1 hr), but when it arrives at our car, we will see it as it was 1.1 hour ago, this because the light has had to travel the extra distance we have traveled in that hour - that is the extra 10 km. (the speed of light is 100km/h relative to space, but relative to us, it’s 90km/h, and this is why you get the red or blue shift)
This means that while only 1.1 hour has passed when we observe the light from the other, the other car, is actually no longer 100km away, but the initial 100km, plus the 10km it has traveled, plus our 10 km, making a total of 120 km, and while our light is only 1.1 hour (10km = 6 light minutes or 1/10th of the hour), what we see, is actually 1.2 hour away, however, we just do not see it as it is now, but as it was 1.1 hour ago.
Now, remember that when we observe the light from the othert car, our universe is actually 2.1 hours old.
So, while our universe is only 2.1 hour old, we would actually be able to see the other car at a distance of 2.2 light hours.
This is due to the expansion factor of the distance between the cars, or the speed at which the cars drive away from each other, which in this case is 1.2.
This means that if we actually detect something being 30 minutes away (50km), it is actually 36 minutes (60km, or 30km + 3km + 3km) away when we see it, and likewise, 200km means 240 in reality, as you would have distance = expansion factor * time, where time is actually a distance in relation to our location.
The speed of the light is constant, but ours is not, as the universe is expanding, which means the distances in light years that we can see, grows beyond the age of the universe.
However, we can not see any further back in time than 13.5bn years, as that would be looking beyond the inflation (big bang), but as you can see from this, we can actually see objects a whole lot further away than 13.5 bn light years.
Distance is equal to time * speed, but again, since the speed increases over time, you can see that distance will not be linear, but actually grow as we look further away.
Hope this has managed to explain it in a bit simpler form, without any complicated maths.
Arun
Sep 22, 2008 at 9:38 pm
If the universe is only 13 billion years old…….then the maximum possible diameter or width of the universe can only be 26 billion light years…..not more than that….since any radiation/particle/object cannot travel more than the speed of light, lets assume 2 particles exploded in exactly opposite directions travelling at the speed of light….those 2 particles would now be 26 billion light years away. simple.
USFBULLSROCK
Sep 25, 2008 at 5:37 pm
OK, I posted this on another site. Maybe someone here can give me an answer. Since the big bang our universe is expanding and accelerating faster than the speed of light. How is it we can see objects on the other side of the universe? To paint a clearer picture, the big bang happened at a certain point. The stuff that eventually became our galaxy went in one direction while other stuff went in the other direction (yes I know in all directions). So if we are now traveling faster than the speed of light, how can we see past the point of the big bang to see the other galaxies traveling in the other direction in the same speeds? Wouldn’t it make sense that we can only see galaxies on our half of the universe since light travels at a constant speed? Which means it would only be possible to see half of the universe. Depending on the vectors of the other matter traveling we would see dimmed versions of other galaxies (redshift). Is that understandable???? Someone please let me know.
Joe Alien
Nov 16, 2008 at 8:57 pm
@Phil E. Drifter: You assume much in your statement. Keep in mind that “space” is not shaped as you think it is (relative to stuff blasting apart from each other). The shape of space may be more like the surface of a balloon as it expands (not the stuff inside the balloon). Imagine you on the surface of a balloon. As it expands, what you would see over time?
USFBULLSROCK
Nov 21, 2008 at 7:35 pm
Joe Alien: So if space is like the surface of a balloon expanding, why can we see galaxies and stars in all directions? If space is shaped like the surface of a ballon, from our view everything in the viewable universe should be viewable as an arc from our perspective. That makes no sense. So what’s inside the balloon? That logic makes no sense.
sonofaphysicist
Nov 23, 2008 at 9:10 am
First, a few things:
1) Before the Big Bang, there was no space and time. The Big Bang is the creation of space and time and so it occurred EVERYWHERE in the universe (as the universe is space) at approximately 13.7 billion years ago. The Big Bang did not happen IN space.
2) The universe is expanding at an ever faster rate (initially inflated by negative-pressure vacuum energy density and now accelerated by something called dark energy). Imagine a balloon with 2 colonies of ants on it. Initially the distance for an ant to travel from colony A to colony B is very close. But as the balloon gets inflated continuously, the distance between the 2 colonies increases but the speed at which the ant moves is constant. So when that ant tells colony B that it took him 1 hour to arrive from colony A, it would actually take a second ant from A 9 hours at that moment in time to get to B now moving at constant ant speed due to that inflating distance.
3) The diameter of the visible universe is approximately 93 billion light years. To simplify things (Galaxy A and B are at the edge of the universe), let’s say you point Hubble in one direction and observe light from Galaxy A that departed 13.7 billion light years ago near the instant of the Big Bang, it would take light 46.5 billion light years to reach you if that light were to leave Galaxy A right now. If you whip Hubble around 180 degrees to observe Galaxy B, you would see 13.7 billion-year-old light arriving, but Galaxy B is now 46.5 billion light years away. Add those two distances up and you get a diameter of 93 billion light years. You can think of the visible universe as a sphere with a diameter of 93 billion light years.
4) The universe is much bigger than the visible universe at 93 billion light years. See my crude drawing below:
Galaxy A ——–Hubble——–Galaxy B
An alien in Galaxy A maybe able to observe the Milky Way at the edge of HIS visible universe but he will not be able to observe Galaxy B, and vice versa. The universe maybe infinitely big as far as we’re concerned because we will not be able to observe anything beyond our observable universe.
christopher
Nov 26, 2008 at 9:08 am
what proof is there to say there are no other universe in existense there could many universes in existense which could be billions and billions of light years away.
christopher
Nov 26, 2008 at 9:13 am
there could be hundreds of universes beyond can you proove there is just one universe in existense?
Stephen Garramone
Dec 2, 2008 at 7:18 pm
Seems like you are saying the universe is some 14 billion years old but the distance to the furthest object we can “see” is some 40-50 billion years. That means the expanding universe carried the most distant objects out such that light travels some 40 billion light years when in original time it would have travelled only 14 billion light years. Hence, the expansion of the universe is actually functionally increasing the speed of light because that object we see at 40 billion light years is really only 14 billion years old.
Does that make sense???
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