a4mula t1_j1dfkt3 wrote
While it is true that the speed of light is a constant, it is not the case that the universe is expanding faster than the speed of light. Rather, it is the space between galaxies that is expanding, and this expansion is occurring at a rate that is slower than the speed of light.
It is possible that the universe is much older than 13.8 billion years, and that it has been expanding for a longer period of time. However, the age of the universe is not determined by the speed of light or the expansion rate of the universe, but rather by the observed properties of the cosmic microwave background radiation and the rate of cosmic expansion. These observations are consistent with a universe that is around 13.8 billion years old, and this is currently the best estimate for the age of the universe.
zoicyte t1_j1dm3fs wrote
This is all wrong.
Galaxies are absolutely separating at rates faster than the speed of light. Or more specifically, space between galaxies is expanding faster than the speed of light, Altho the galaxies themselves are still moving at sublight speed. Light moves through this space at the speed of light however, and the furthest things we can see are approximately 13 billion light years away. We see them as they were 13 billion years ago however, “shortly” after the universe stopped being opaque. Those galaxies now however are actually more than 40 billion light years away now, but we haven’t had time to see them yet, for obvious reasons (the universe isn’t that old). The oldest thing we can “see” is the cosmic microwave background radiation - the last signal of the opaque universe which actually makes up a good chunk of radio static you can hear, and emanates from around the 400,000 year old point in the history of the universe.
All of this can be calculated using Einstein GR equations, and others sorted out in the subsequent 50 years.
Without getting into diffEQ, the math works out that all of space time was compressed into the same point (the big bang singularity) approximately 13.8 billion years ago, the total diameter of the universe that we can see now is actually closer to 80bly, but that’s just the part we can see now, the universe could be infinite and we wouldn’t know.
It’s a lot to take in, but you need to remember what we can “see” today is what existed when the light was emitted, not as it is “today”, and the farther away it is, the older that light would be, so the farther back in time you’re looking.
a4mula t1_j1dn5dl wrote
I think we should all be careful when we're talking about right and wrong. Perspective is important.
You are correct that the space between galaxies is expanding at a rate that is faster than the speed of light. However, it is important to note that this expansion is not a violation of the laws of physics, as it does not involve the movement of matter or energy through space.
The expansion of the universe is a phenomenon that is associated with the expansion of space itself, rather than the movement of matter or energy through space. The expansion of the universe causes the distance between galaxies to increase over time, and this expansion can occur at a rate that is faster than the speed of light. This is because the expansion of the universe is not limited by the speed of light, but rather by the properties of space itself.
zoicyte t1_j1do177 wrote
I don’t think I made any statements implying it was breaking any laws of physics?
[deleted] t1_j1duhk8 wrote
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Ennara t1_j1e1akv wrote
>the space between galaxies is expanding at a rate that is faster than the speed of light. However, it is important to note that this expansion is not a violation of the laws of physics, as it does not involve the movement of matter or energy through space.
Oh god, this breaks my brain. The amount of space between galaxies is expanding, but the galaxies themselves aren't moving as a result of the expanded space between them? I'm not saying you're wrong, but god dang I can't wrap my head around how that's actually possible.
The only vaguely coherent thing I can think of is like... a piece of taffy, where the two galaxies are sitting on the edges and you stretch the middle downwards. So the amount of space the taffy occupies increases, but the galaxies don't actually move. But I don't think that's accurate, because if space between us and a distant galaxy is expanding, then the distance increases which it doesn't in the taffy explanation... And I'm back where I started.
a4mula t1_j1e1s1h wrote
If you read the earlier analogy with the cake.
We can pretend, because its just an analogy. That space in the analogy is air in the cake.
The molecules of the cake aren't growing or moving. It's only that the air in between them continues to grow.
It will ensure that the cake molecules end up with greater distance between other cake molecules.
But it's not because the cake molecules moved. It's because the air in between them grew.
Now this is just pretend, because air is not space. Air is molecules too. So I don't want to confuse that.
But it does fit the analogy.
Ennara t1_j1e40x2 wrote
Yeah, I sort of get that, I think at the core of it all I'm just having trouble wrapping my head around the concept of increasing the amount of space between two objects without moving them. Using the cake analogy, I'm finding it difficult to understand how the air molecules move in such a way to take up more space without pushing the things that already occupy that space out of the way. I can accept that they are based on the studies and testimony by people far smarter than I am, but my brain is pitching a fit because I'm struggling to grasp the 'how.'
a4mula t1_j1e5iic wrote
That's okay. I mean these are Big topics. It's taken our species millions of years of slowly building up to this point right now that we have the understandings we do of them.
It's not easy. For anyone. Not for you, Not for me. Not for Einstein.
We're not born innately knowing this, we're educated about it. If they are concepts that we find interesting, perhaps we consider them. It's only through this education and consideration, not just the education itself, that we come to understanding.
Not everyone has the time or inclination to consider these topics, and that's okay.
But for those that do, understanding will grow in some type of correlation between the interactions of the education and your consideration of.
Ask for analogies, they're great tools of abstraction. It takes these difficult concepts out of the realms of mathematics, and puts them squarely into terms we can better understand, everyday language. Math is important, but if it's not a language spoken by us, it's not helpful.
Einstein's brilliance was never that he was a great mathematician. It was his ability to break down very complex thoughts into stories he could understand.
a4mula t1_j1eafan wrote
I wanted to add another reply here.
What If I wanted a really cool expandable cake like we talked about and asked you to make it for me.
But I've got a very special request.
After you bake the cake and add the frosting. I'd like to add a special flavoring. So that anyone can make this cake taste the way they'd like.
See if you can figure this out. Can I do this? What do the actual interactions look like? If I dropped the flavoring into one part of the cake, how would it distribute?
Would it be evenly? Could it ever fill the entire cake, assuming the cake never stopped growing? How would it travel from one cake molecule to the next?
This will help you to understand concepts like speed of light, and why we can't pass information faster than it.
It'll help you to understand localized events and how they interact with portions of the universe, but never the entirety of it.
Think about the relative movement. Without the flavoring now. The space between two cake molecules will always be a different relationship depending on the location of where they exist in relation to one another.
Two cake molecules side by side will always experience the same relative separation. But two molecules separated by the entire cake will always experience greater total separation because all the spaces of molecules growing in between them are cumulative.
We can pass flavor between two cake molecules, indefinitely. But assuming the cake never stops growing, what you'll find is the ability to spread the flavor becomes a function of the overall growth rate of the cake as a whole, meaning it can never keep up and that the total amount of the cake that is flavored in respect to the total cake, will always decrease.
That's odd. Because we're still getting more cake that is flavored. It's just that the amount we get will always represent a smaller percentage of the whole.
edit: We've taken our analogy in a very specific direction. One of infinite inflation of a mostly spherical object. Our universe doesn't need to meet those criteria. This is just one way to consider things. If the universe has different parameters, the interactions would inherently be different. What if our cake was really a doughnut? What if it were just a 2d plane of 3d information?
Keep these things in mind, as there are clear limitations to locking our thoughts into the ability of analogies to represent ideas.
ramsncardsfan7 t1_j1e0y0q wrote
Why do I see experts saying the universe wasn’t actually a singularity at the time of the Big Bang?
zoicyte t1_j1e1yw1 wrote
Well strictly speaking a singularity is just a breakdown in the known laws of physics. something has to be down their, we just don’t know really what, or how it behaves.
Why did expansion start? Where did it all come from? What came “before”, to the extent that statement even has any meaning? These questions are at the very bleeding edge of theoretical physics and aren’t really testable yet.
[deleted] t1_j1e2uq7 wrote
I wonder whether they ever will be. Our ability to peer back in time relies entirely on what we can see and the radiation we can capture and analyze. Looking back far enough, it all becomes opaque because "first light" hadn't happened yet. Perhaps some new tech will throw the doors open some day, but if we cannot see past a certain point, and that point happened after the "bang," then we will never know what came before the opaqueness.
For that reason, I don't know for sure that the singularity has any merit. If we run the clock backwards we get a singularity, but since we can't see past a certain point, we don't actually know whether singularity is a real concept.
zoicyte t1_j1e3hmo wrote
It’s not just about looking “out there”, a lot of the early-universe physics are probed in high energy particle colliders. It’s mostly about understanding quantum effects at that point.
Geodad478 OP t1_j1dg6cn wrote
Microwave radiation is still light though. At some point, the CMB radiation would not be visible due to the distance being to far for the light to ever reach us.
The CMB could be extending beyond what we could observe due to the speed of light.
a4mula t1_j1di7zx wrote
This is a challenging and subtle thing, right?
Let's look at it through analogy.
If we have a special kind of dough. One that that continues to grow after we bake it.
And we make a cake. The second that cake comes out of the oven, we put a layer of frosting across the top.
As time goes by, our special kind of dough grows. It makes the cake larger. But it never adds to the amount of icing we put on it. The icing is just stretched in ways so that it remains in the correct proportions.
We can measure that icing, and how it's stretched to determine how much time has passed since we applied it.
That's all this is.
RazeTheIV t1_j1dizhh wrote
This was a fascinating read, thank you and OP. Great question.
hreflet t1_j1dn8vm wrote
First off, I'm not very knowledgeable on the topic but always have trouble understanding how we can confirm things like age of the universe etc.. so forgive me if I'm asking stupid questions.
Your analogy is the first time I've been able to somewhat understand so thanks for that but to follow up, how can we know how much of this "icing" was there to start with in order to accurately tell the age? (Is the icing the cosmic radiation?)
Follow up question. Why do we confrm and deny things based on our limited knowledge? Who's to say that things don't work differently out there in the distant universe? I have trouble thinking that the far universe and even other planets work according to the same laws as we know.
a4mula t1_j1doh37 wrote
There are many different properties of the CMB. Temperature, intensity, spectrum. As time progresses these will all change. From there it's a matter of rewinding the clock back to its original, highest energy state.
We don't know. And the truth is, we can never know with absolute certainty. Science isn't a study of Truth, not really. It's a study of observable phenomena that we use to make models to help us accurately understand our reality.
From that stance, they've been very successful as it gives us technology. Regardless of any Truth statement.
We approach infinity, We approach Truth. Never is either reached.
hreflet t1_j1drti3 wrote
I understand what you're saying.
I just wish I could be alive when we can explore further into the unkown. Any knowledge on this topic fascinates me so much. Thank you again for that icing on the cake analogy. May you have a wonderful day.
a4mula t1_j1dsqm6 wrote
You are alive for that! Look around. So much is being discovered today that nobody can keep up with it all. That's mind blowing to me.
Even as a child in the 80s, I might go months without having some major discovery made, maybe years.
Today I can't get through a single news cycle.
Never fear that we'll run out of discovery. That's not possible. Novel information is created faster than it's absorbed, at least by any given individual.
We're delving into reality in ways today that are mind blowing on many different scales.
The real fear, is running out of time to explore.
shassis t1_j1doje1 wrote
What we “know” is what best fits what we observe. As observations improve then we we know becomes more refined. It appears that the sun revolves around the earth but as instruments and observations progressed we gained a different understanding. It takes time.
ishpatoon1982 t1_j1dpzzj wrote
As for your second question, confirming and denying things based on our knowledge is what science is. If we find new workable theories and/or facts that go against our current process, well...we change our process to fit the newly found evidence.
We work with our knowledge because it's all that we have. We don't have access to anything else besides how we as humans think and retain.
a4mula t1_j1dgkz8 wrote
Sure, but you're confusing the relationship. The age of the universe is determined by the observed properties of the CMB radiation and the expansion rate of the universe, rather than the size of the observable universe or the distance to the CMB radiation.
Geodad478 OP t1_j1difnb wrote
This is why I asked the question here. 🙂
[deleted] t1_j1do7kf wrote
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nicuramar t1_j1ds7we wrote
> The universe is not expanding faster than c. In the very early universe, this was true,
What’s that supposed to mean? Expansion is a rate, not a velocity. Relative velocity is only locally well-defined.
How did the early universe expand at more than c in any way that doesn’t just as well apply now, over enough distance?
drosse1meyer t1_j1e13q0 wrote
Well, if you want to be pedantic, velocity is a rate too, is it not? Distance over time.
Anyway, there are countless articles / studies about this that can explain it far better than anyone on this thread. Suffice it to say, the size of the universe expanded from the planck length to a factor on the order of 10^28 in an extremely short amount of time
Existing radiation would simply be stretched and omnipresent given this massive change. That is why we have the CMB.
nicuramar t1_j1e7dhd wrote
> Well, if you want to be pedantic, velocity is a rate too, is it not?
Yes, but expansion is velocity over distance, so it’s not units of velocity and thus isn’t c or below or above c.
> Suffice it to say, the size of the universe expanded from the planck length to a factor on the order of 1028 in an extremely short amount of time
The observable universe. Maybe, yes, but that doesn’t make it expand at a certain velocity unless you measure over a certain distance. And at this distance, relative velocity wouldn’t be well defined due to the curvature of spacetime, and wouldn’t be constrained to c anyway.
See first answer to this: https://physics.stackexchange.com/questions/400457/what-does-general-relativity-say-about-the-relative-velocities-of-objects-that-a
tr14l t1_j1dp6eg wrote
Some observations: the masses of celestial objects are all moving away from each other, as if expanding. If they are moving away from each other, it's a pretty good assumption that, if we were to rewind that, at one point, they were all together.
Measuring the velocity with which they are moving is easy enough. So, coming up with a model for rewinding that (and how long that would take) is actually not the most complicated thing in the world. If we were to "rewind" it, it would take ~14 billion years. Of course, there may be some variables that effect that age, but most of the biggest ones (gravity, expansion, etc) are fairly easily observed and accounted for. So it is unlikely based off current observations that we are trillions of years off. Millions perhaps, but that's fairly small.
Indigo816 t1_j1dpbbh wrote
Look up physics girl on YouTube. She’s got a video on that.
BrotherBrutha t1_j1dj8mi wrote
The question “is the universe expanding faster than the speed of light?” is not really a valid one anyway - the speed that two points in space appear to be moving away from each other depend on how far apart they are at the time of measurement.
[deleted] t1_j1dqutj wrote
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informativebitching t1_j1dogdc wrote
So the observable universe only?
eIImcxc t1_j1dwlkl wrote
>While it is true that the speed of light is a constant
Here is the problem. That is not even true. We're basing everything on things that we ~suppose~ true. We don't even know for sure if the speed of light is not dependent on direction or on anything else that we can't grasp as limited beings.
Now that's just one foundation on what we're measuring the age of the universe. Now imagine that every single other principle is also keen to a complete misunderstanding.
a4mula t1_j1dwzbo wrote
I'm sure there are many fundamental aspects of reality we get wrong, or could be more precise with, or could understand better.
I'm not sure the speed of light in a vacuum is one, but I do agree with the premise you're presenting.
But it's important to understand this isn't about Truth. It's about approaching it. It's not about defining reality. It's about creating models of it that help us to interact with it.
There can be no denying that we have increased our understanding, it's directly reflected in the fact that technology increases and works.
That's the benefit. Not the truth of any given statement. But how these models can advance our understandings.
eIImcxc t1_j1dywa4 wrote
Completely agreed but OP's question was about questioning our measure of the universe's age.
Considering what we just said, I think that the range park that we got has close to no chance to be right. Our entire theory is based on the observable universe and our very vicinity, be it in time or space.
All things considered, we're pretty much toddlers trying to find the Earth's radius.
a4mula t1_j1e0697 wrote
Perhaps, and we're all offered the same opportunity to observe our reality and put forth theories regarding it.
If the theories we propose do a better job of explaining the observed data and do not introduce any new problems. Those theories are typically accepted to represent a piece of the model.
Explore and plunge and theorize. Because maybe you're the next person that helps us to understand better.
Science doesn't claim to be correct. It's just a framework that is in place to judge the accuracy of predictions, and when it works properly the best predictions are kept, and the ones that are less successful are discarded.
It's certainly not a perfect system. Humans control it. But it's a good system in that it's iteratively accepting of new facts, while discarding any that have been shown to be incorrect.
eIImcxc t1_j1ek2ew wrote
> Science doesn't claim to be correct.
That's what the vast majority don't get.
Thanks for the encouragement but as an analogy I'm more a watch it from the couch kind of guy. I guess also a coach since I'm tutoring students (Maths and Physics), so maybe one of them will make a breakthrough :)
a4mula t1_j1fehth wrote
Most of us will never provide to the frameworks of science. Not directly. We could, but it requires an understanding of formalized language that most do not possess, including myself.
But we can contribute towards the concepts and ideas and goals. We can encourage one another to have considerations towards the basic principles. Be fair. Be honest. Be critical minded. Try to minimize bias.
And we don't know how that ripples through reality, but I'd like to believe it's a positive influence overall.
I appreciate your time in educating the youth. It's a very important job, and I'm glad that it's being done by someone that does consider these things.
eIImcxc t1_j1fgyxn wrote
>I appreciate your time in educating the youth. It's a very important job, and I'm glad that it's being done by someone that does consider these things.
Thanks for that. Be assured that I do it with passion.. and I'm quite lucky that they give me back the positivity.
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