Atheist Universe: Not Impossible

[mpok1519]

I'm not sure where you're getting the collapsing star from... the big bang is not theorized to be anything like a super nova (an exploding star).

It's a general misconception that the big bang happened somewhere in the universe. But as the theory suggests, it happened everywhere in the universe because space sprang from the bang. As this following article calls it- it was not an explosion in space, but an explosion of space.

Misconceptions about the Big Bang: Scientific American

I know dude; I was using it as an example to put an illustrative image in peoples' heads for visualization. IF we were to watch the big-bang taking place, what would we be witnesses? Whats a good description of what we'd be seeing?

I do believe in BBT; its the best theory as far as we know. Its just, if space doesn't exist, then, whats in the space of that space? anti-space?

and Im very interesting in anti-matter studies. Do positrons and negatrons(?) tell us anything about these kinds of physics?

 

[Wiccan_Child]

More of a word game, actually. You said "anything else," implying there is something.

No. What I said was: "But the point is that nothingness is not restricted by anything else because, by definition (and thus beyond mere tautologies), there cannot be anything else"

I was making the same point you are: that there are no things. By definition, there is not anything. There are no things.

I don't know how else to say it. I said there is not anything else, not that there is.

I suppose you might have gotten confused by the 'else' part, though.

Once a thing has the possibility to become something, it has potential.

Since I'm not saying that nothingness has the possibility to become something, your point is moot.

Potential is an inherent property of existence(name something existent that does not have potential),

Why? Analogising existence with non-existence is, quite literally, apples and oranges.

and since potential can only be realized by progression,

Only with continuous probability. Given the unique circumstances, temporal continuity doesn't really make sense, so your point is again moot.

there has to be at least something to progress from.

Not necessarily from a thing, but rather from one state to another. Namely, from "nothing exists" to "something exists".

IS there a law telling nothing this? Yes, the fact that it is nothing and by its nature a comparative state(we have know something to know nothing).

I beg your pardon?

Because potential is an inherent quality of existence. If it does not exist, it does not have potential. If it exists, it has potential.
If nothing has potential, it is not nothing but simply potential something. Like a hunk or marble is not "not a statue," but "potentially a statue." But with that potential is implied the ability to become, which makes it existent.

I disagree that a) potential requires existence, and that b) I implied nothingness has potential.

Well, to address your last statement, us observing things without apparent causes has two problems, one being that we could simply not understand this universe of ours completely(we don't), and thus be missing the cause,

That's certainly a possibility, but so to is the existence of magic gnomes at the bottom of my garden. Moreover, indeterminate behaviour is crucial to our explanations of radioactive decay, virtual particles, the Casimir effect, vacuum energy, etc. While we may no

and another thing is that the apparent causelessness only occurs in certain environments. Which means, as far as any observed or theorized causelessness is concerned, existence is a prerequisite.

On the contrary, the spontaneous generation of particle-antiparticle pairs occurs everywhere, without exception.

 

[Wiccan_Child]

Well, from what I know and the physics classes I've taken, physicists generally understand that the Big Bang created space itself.

That is, they can observe that space itself is currently expanding.

The three main evidences that the Big Bang even occurred are:
1. Space is expanding
2. Cosmic Background Radiation
3. Small atoms making up most of the universe

So, it's not like there is evidence that shows the Big Bang created space. More specifically- space is expanding, and if extrapolated along with the evidence, shows that it must have come from an infinitely small point. So the fact that space is expanding is evidence of the Big Bang, not the other way around.

The expansion of spacetime over the past 13.5 billion years is what is called the 'Big Bang'. I agree that the evidence supports it, but I don't see how go from 'space has been expanding from 13.5 billion years from a singularity' to 'space was created 13.5 billion years ago'. That it's been expanding all this time doesn't mean it wasn't doing anything before then.

 

[Wiccan_Child]

I know dude; I was using it as an example to put an illustrative image in peoples' heads for visualization. IF we were to watch the big-bang taking place, what would we be witnesses? Whats a good description of what we'd be seeing?

There isn't. To witness the Big Bang, we'd have to be in the singularity.

I do believe in BBT; its the best theory as far as we know. Its just, if space doesn't exist, then, whats in the space of that space? anti-space?

If there's no space, then there is nothing for anything to be 'in'. Space doesn't exist anywhere, it just is.

and Im very interesting in anti-matter studies. Do positrons and negatrons(?) tell us anything about these kinds of physics?

No. Every particle has a corresponding antiparticle, which is exactly the same but has the opposite charge. For example, the electron has a charge of -1, and its corresponding antiparticle (the positron) has a charge of +1.

Anti-matter isn't that exciting, and it certainly doesn't tell us much about then nature of spacetime. But I have to ask: what's a negatron? As far as I can tell, it's an old term for the electron.

 

[mpok1519]

There isn't. To witness the Big Bang, we'd have to be in the singularity.

I think I've smoked enough pot to understand what that means. heh.

If there's no space, then there is nothing for anything to be 'in'. Space doesn't exist anywhere, it just is.

Ok, I havn't. =P

Anti-matter isn't that exciting, and it certainly doesn't tell us much about then nature of spacetime. But I have to ask: what's a negatron? As far as I can tell, it's an old term for the electron.

Negatron....a negative proton....I mean, a positive electron.....or wait, no....heh...

 

[Wiccan_Child]

I think I've smoked enough pot to understand what that means. heh.

Negatron....a negative proton....I mean, a positive electron.....or wait, no....heh...

Well, the anti-electron is called a positron (because it's positively charged), and the anti-proton is just called an anti-proton. We ran out of names .

 

[MaxP]

No. What I said was: "But the point is that nothingness is not restricted by anything else because, by definition (and thus beyond mere tautologies), there cannot be anything else"

I was making the same point you are: that there are no things. By definition, there is not anything. There are no things.

I don't know how else to say it. I said there is not anything else, not that there is.

I suppose you might have gotten confused by the 'else' part, though.

Eh, it's just semantics.

Since I'm not saying that nothingness has the possibility to become something, your point is moot.

Yeah you are. By saying nothing can progress to cause our universe, you say no thing can become existant. Progress.

Why? Analogising existence with non-existence is, quite literally, apples and oranges.

Exactly. We can safely assume non-existence is the complete opposite of existence. So they do not share properties.

Only with continuous probability. Given the unique circumstances, temporal continuity doesn't really make sense, so your point is again moot.

You moot your own point by disregarding any potential laws in the way to logically proving your point. Logic doesn't exist if you disregard all other rules, therefore you make your own point pointless in the process of proving it.

not necessarily from a thing, but rather from one state to another. Namely, from "nothing exists" to "something exists".

But there is not a state of nothing existing. Assuming nothing is a state also assumes a greater system(you cannot have a state of nothing, a state is associated with an already existent system).

I beg your pardon?

I was saying the nature of nothing is tied to something.

I disagree that a) potential requires existence, and that b) I implied nothingness has potential.

Well, for a, nothingness has no potential because it has nothing for which to have potential. And you implied nothing has potential by saying it can, at some point(which is ridiculous, because progression is impossible out of time), can be or give rise to something.

That's certainly a possibility, but so to is the existence of magic gnomes at the bottom of my garden. Moreover, indeterminate behaviour is crucial to our explanations of radioactive decay, virtual particles, the Casimir effect, vacuum energy, etc. While we may no

Well, like i said, we do not yet know, and even assuming we do, the causelessness requires existence.

On the contrary, the spontaneous generation of particle-antiparticle pairs occurs everywhere, without exception.

Hmmm. Still existence is a prerequisite.

 

[ragarth]

I do believe in BBT; its the best theory as far as we know. Its just, if space doesn't exist, then, whats in the space of that space? anti-space?

Whatever it is we're expanding from: Holographic principle - Wikipedia, the free encyclopedia

"In a larger and more speculative sense, the theory suggests that the entire universe can be seen as a two-dimensional information structure "painted" on the cosmological horizon, so that the three dimensions we observe are only an effective description at low energies. Cosmological holography has not yet been made mathematically precise, partly because the cosmological horizon has a finite area and grows with time."

The holographic principle is something I'd be keenly interested in knowing more about. Anyone have a link for more information on this stuff?

 

[R3quiem]

I know dude; I was using it as an example to put an illustrative image in peoples' heads for visualization. IF we were to watch the big-bang taking place, what would we be witnesses? Whats a good description of what we'd be seeing?

I don't think there is any way to describe what we would see. Space itself would be expanding into non-space, so if we were to be "witnesses" of it, we'd have to have a reference frame in non-space, which doesn't make sense. Plus, light wouldn't be getting to us yet, so any visual perception wouldn't work.

Folding space into non-space makes human being heads explode.

I do believe in BBT; its the best theory as far as we know. Its just, if space doesn't exist, then, whats in the space of that space? anti-space?

and Im very interesting in anti-matter studies. Do positrons and negatrons(?) tell us anything about these kinds of physics?

I can't answer what the opposite of space is. Physicists like to use a balloon as an analogy, but that doesn't really capture what is happening. It's like trying to show someone what the curvature of space looks like using 2D models- it gets the job done but 3D space is much more difficult to conceptualize a curve in. It's apparently understandable through math, but visual descriptions really don't do justice. We humans have brains wired to comprehend space, so we can't really comprehend non-space.

As far as anti-matter goes, I don't know anything about how it relates to the Big Bang- maybe one of the physicists here does. I do, however, remember a program where theoretical physicists were asking the unanswered question of why the observable universe seems to be made entirely of matter instead of anti-matter. Apparently, anti-matter and matter are exactly identical but opposite- that is, for every charged particle there is a particle of the opposite charge with the same qualities. If they are equal, then one would assume they'd be made in equal quantities and then annihilate each other into pure energy, but obviously that has not occurred. For whatever reason, the universe as we can see it appears to be made only of matter, and that creates symmetry issues. Why did one side win over the other? How did this happen? The answer to these questions may involve the Big Bang.

 

[R3quiem]

The expansion of spacetime over the past 13.5 billion years is what is called the 'Big Bang'. I agree that the evidence supports it, but I don't see how go from 'space has been expanding from 13.5 billion years from a singularity' to 'space was created 13.5 billion years ago'. That it's been expanding all this time doesn't mean it wasn't doing anything before then.

This little tug of war of our last few posts started because you pointed out to me that we cannot know what happened before the Big Bang, and asked me to prove that space was created with the Big Bang.

The post you were criticizing was my post #133. Apparently you skipped post #134, which was a post of mine all about how we shouldn't discuss with authority what happened before the Big Bang, because it's all speculation.

My post 133 was to address a common misconception that the Big Bang occurred somewhere in space, as opposed to creating space in and of itself. If you read post 134 before addressing me, it would have been clear that I was not stating anything about what, if anything, occurred "before" the Big Bang, and I doubt these posts between us would have existed. I think you are addressing details of what "creation" means instead of understanding why I posted that- to address a misconception.


The Big Bang theory, along with the timeline of it, is an extrapolation. It is taking into account the observation that the universe is expanding, as well as other observations such as the magnitude and quality of the background radiation, to form a mathematical model of the timeline of our universe. To say that space existed in our universe prior to the Big Bang is awkward- seeing as how the Big Bang is more or less defined as the birth of the spacetime of our universe, or at least the expansion of it from a singularity (which could hardly be called space). When the expansion of spacetime, as well as the other factors are extrapolated backwards, they get a timeline of about 13.5 billion years for when all of this would have been in a singularity- and they call this moment the Big Bang.

As to whether concepts like "space" or "time" could have had any meaning prior to the Big Bang is speculation at this point. That gets into things like oscillating universe theories, branes bumping into each other to create universes, and all sorts of other ideas concerning what may have caused the Big Bang. But what is understood is that at the moment of the Bang, there was some sort of singularity lacking space, and now we have an absurdly large universe- hence the creation of space. More space from less space or no space.

 

[Chesterton]

Whatever it is we're expanding from: Holographic principle - Wikipedia, the free encyclopedia

"In a larger and more speculative sense, the theory suggests that the entire universe can be seen as a two-dimensional information structure "painted" on the cosmological horizon, so that the three dimensions we observe are only an effective description at low energies. Cosmological holography has not yet been made mathematically precise, partly because the cosmological horizon has a finite area and grows with time."

The holographic principle is something I'd be keenly interested in knowing more about. Anyone have a link for more information on this stuff?

I have a copy of The Holographic Universe by Michael Talbot. He based his ideas on the ideas of David Bohm and Karl H. Pribram.

It's not a very good book; interesting at first but just sketchy and speculative and filled with anecdotals. I don't think Talbot was a physicist himself, but a science fiction writer.

 

[Wiccan_Child]

Yeah you are. By saying nothing can progress to cause our universe, you say no thing can become existant. Progress.

Since I never said that nothingness can progress to cause our universe, your point is still moot.

Exactly. We can safely assume non-existence is the complete opposite of existence. So they do not share properties.

What? How?

Let's say that the totality of existence has a net charge of +1C. Does that mean that nothingness has a net charge of -1C? No: charge is a property of matter, and a net charge of zero is the same as having no charges at all.

Existence and non-existence can share properties, which harkens back to my point about apples and oranges: the idiom refers to the fact that the two are incomparable. Knowing something about one tells us nothing about the other. Knowing that existence has some property doesn't tell us whether nothingness has it either.

You moot your own point by disregarding any potential laws in the way to logically proving your point. Logic doesn't exist if you disregard all other rules, therefore you make your own point pointless in the process of proving it.

I don't understand. Potential laws? Logic not existing? Huh?

But there is not a state of nothing existing. Assuming nothing is a state also assumes a greater system(you cannot have a state of nothing, a state is associated with an already existent system).

I am using the word 'state' in a very loose sense. The point is that initially nothing exists, and then later (inasmuch as time exists) something exists.

I was saying the nature of nothing is tied to something.

Undoubtedly: nothingness is defined in terms of things.

Well, for a, nothingness has no potential because it has nothing for which to have potential.

Which begs the question: why must potential be a property of an existent thing? Why can't nothingness have potential? Or rather, why must something exist for there to be potential?

And you implied nothing has potential by saying it can, at some point(which is ridiculous, because progression is impossible out of time), can be or give rise to something.

That was not my intention.

Well, like i said, we do not yet know, and even assuming we do, the causelessness requires existence.

My point was that it doesn't: the spontaneous generation of matter occurs regardless of what does or doesn't exist.

Hmmm. Still existence is a prerequisite.

Why?

 

[Wiccan_Child]

This little tug of war of our last few posts started because you pointed out to me that we cannot know what happened before the Big Bang, and asked me to prove that space was created with the Big Bang.

The post you were criticizing was my post #133. Apparently you skipped post #134, which was a post of mine all about how we shouldn't discuss with authority what happened before the Big Bang, because it's all speculation.

My post 133 was to address a common misconception that the Big Bang occurred somewhere in space, as opposed to creating space in and of itself. If you read post 134 before addressing me, it would have been clear that I was not stating anything about what, if anything, occurred "before" the Big Bang, and I doubt these posts between us would have existed. I think you are addressing details of what "creation" means instead of understanding why I posted that- to address a misconception.

Perhaps, and I apologise for missing post #134. But strangely, the rest of your post here reads as an argument for the Big Bang being the creation of space.

The Big Bang theory, along with the timeline of it, is an extrapolation. It is taking into account the observation that the universe is expanding, as well as other observations such as the magnitude and quality of the background radiation, to form a mathematical model of the timeline of our universe. To say that space existed in our universe prior to the Big Bang is awkward- seeing as how the Big Bang is more or less defined as the birth of the spacetime of our universe, or at least the expansion of it from a singularity (which could hardly be called space). When the expansion of spacetime, as well as the other factors are extrapolated backwards, they get a timeline of about 13.5 billion years for when all of this would have been in a singularity- and they call this moment the Big Bang.

No they don't . "The Big Bang is a cosmological model of the initial conditions and subsequent development of the universe." - Wiki
The Big Bang isn't the singularity itself, or the moment when it started expanding, but what happened after. It's a common misconception.

As to whether concepts like "space" or "time" could have had any meaning prior to the Big Bang is speculation at this point. That gets into things like oscillating universe theories, branes bumping into each other to create universes, and all sorts of other ideas concerning what may have caused the Big Bang. But what is understood is that at the moment of the Bang, there was some sort of singularity lacking space, and now we have an absurdly large universe- hence the creation of space. More space from less space or no space.

A singularity doesn't lack space. As I said, the evidence only leads us back so far. We simply don't know enough about how space, time, and energy operate under such conditions.
For example, quantum mechanics predicts that the singularity of a black hole is of small, but finite, volume, while general relativity predicts that it is of infinitesimal volume (that is, quantum mechanics predicts a discrete spacial gradient). But both agree that space (and, in this case, matter) nonetheless exists.

But like I said, we can only look back so far. We know there was a singularity, but we don't know what went on before it. We can model it when it was of a certain size and density, but we can't model it when it was any smaller. So to say that the singularity was spaceless is to wander into blind conjecture.

 

[ragarth]

The post you were criticizing was my post #133. Apparently you skipped post #134, which was a post of mine all about how we shouldn't discuss with authority what happened before the Big Bang, because it's all speculation.

It's possible that the recently launched Herschel satellite will give us some answers about what existed before the big bang. It theoretically will have sufficient IR resolution to be capable of looking at the distribution of hot and cold spots within the cosmic background radiation. If they're evenly distributed then it's unlikely that our universe is the result of a cylce of expansions and contractions (cyclical universe model). If they're not evenly distributed then it's more likely that our universe is either one in a series or the last one in a line of expansions and contractions.

(WARNING: From here forward I'm talking out my blowhole, fact-check everything I say.)

If I remember correctly, we don't actually know what lies beyond our 3d space. It could be the non-existance of space itself, or it could be higher-dimensional space. I read an interesting proposal a while back that stated our universe is the result of a collapse of higher dimensional space, and the inflation is a product of this expanding collapse.

 

[R3quiem]

Perhaps, and I apologise for missing post #134. But strangely, the rest of your post here reads as an argument for the Big Bang being the creation of space.

No they don't . "The Big Bang is a cosmological model of the initial conditions and subsequent development of the universe." - Wiki
The Big Bang isn't the singularity itself, or the moment when it started expanding, but what happened after. It's a common misconception.

Firstly, I didn't say that the Big Bang was the singularity itself- though I did argue that it was the moment that singularity became no longer a singularity. One could argue that the Big Bang is still occurring, though it started at that moment.

Secondly, read the definition you posted- it includes initial conditions. That is, it doesn't just cover what happened after the bang, but also what conditions were present initially.

A singularity doesn't lack space. As I said, the evidence only leads us back so far. We simply don't know enough about how space, time, and energy operate under such conditions.
For example, quantum mechanics predicts that the singularity of a black hole is of small, but finite, volume, while general relativity predicts that it is of infinitesimal volume (that is, quantum mechanics predicts a discrete spacial gradient). But both agree that space (and, in this case, matter) nonetheless exists.

But like I said, we can only look back so far. We know there was a singularity, but we don't know what went on before it.

We can model it when it was of a certain size and density, but we can't model it when it was any smaller. So to say that the singularity was spaceless is to wander into blind conjecture.

Nowhere did I argue that space itself existed in no form whatsoever prior to the big bang. My point was simply that not all of this space, in the form that we know it, was just sitting around like it is now. I didn't take the time to word it perfectly because I was just pointing out a misconception, not writing an essay as though it was going to be peer reviewed by a professor. My point is simply to express the understanding that the Big Bang was not just some explosion spewing matter and energy into a large universe that already existed in space- but instead began expanding all of the space in the universe at that moment. Nothing more, nothing less. Nowhere in my posts did I state what occurred before the Big Bang, if such a statement even makes sense, other than to point out some of the more prominent theories/speculations.

Let's say we have a singularity with infinitesimal volume. Now let's say we have a universe billions of lightyears across. What happened- little or no space became lots of space. Space was "created" (see below before commenting), at least the kind of three dimensional space we are familiar with. That is not to say that no space existed. Imagine a drop of water turning into an ocean- water existed in the drop, but now exists more so in the ocean, hence more water came from either somewhere or nowhere, but now is here.

Of course one could argue with all sorts of speculation. We might say that multiple higher dimensions were unfolded- hence expanding space to something we are familiar with, not creating it. We might say that there existed a previous universe, with space just like ours, that collapsed into a singularity and then expanded back to include space again, hence it was just a conversion. Or perhaps space really did come from non-space. This speculation, however, is something people with PhD's cannot answer, let alone two university students online. Nobody currently has the tools to measure what occurred during the early stages of the Big Bang, especially before the Planck time. It is above and beyond the point I was making initially. And my point was simply that the space in the universe as we know it was not just sitting around the way it is now prior to the Big Bang.

 

[R3quiem]

It's possible that the recently launched Herschel satellite will give us some answers about what existed before the big bang. It theoretically will have sufficient IR resolution to be capable of looking at the distribution of hot and cold spots within the cosmic background radiation. If they're evenly distributed then it's unlikely that our universe is the result of a cylce of expansions and contractions (cyclical universe model). If they're not evenly distributed then it's more likely that our universe is either one in a series or the last one in a line of expansions and contractions.

(WARNING: From here forward I'm talking out my blowhole, fact-check everything I say.)

If I remember correctly, we don't actually know what lies beyond our 3d space. It could be the non-existance of space itself, or it could be higher-dimensional space. I read an interesting proposal a while back that stated our universe is the result of a collapse of higher dimensional space, and the inflation is a product of this expanding collapse.

I'm looking forward to what that satellite brings back in terms of information.

As far as a cyclical universe is concerned, I remember reading that such a cyclical universe is already very much in doubt due to the fact that the expansion of space is currently observed to be accelerating, leading to assumptions that it doesn't look like it will ever collapse.

Lastly, you are correct in saying that we don't know what lies beyond our 3d space. Maybe it's non-space, maybe it's higher dimensional space, who knows. One theory I've heard suggests that if the universe is a closed system, that is, the omega parameter is below 1, then if one could somehow go to the end of the universe, they would appear on the other side of the universe much like how one can sail around the spherical world. But, all of that is speculation because we don't have enough data.

 

[Penumbra]

I have a question about the age of the universe...

Supposedly the universe came into existence 13.7 billion years ago, but according to Einsten's Special and General Relativity, all frames of reference are valid and there is no universal reference frame.

Reading up on the subject, I discovered that astronomers use a specific reference frame called the cosmological reference frame that has something to do with the background radiation being the same in all directions. Why is this reference frame more valid than any other reference frame? Wouldn't relativity mean that depending on how fast your frame of reference has been moving, the age of the universe varies? What about particles that move at light speed? How can a reference frame be applied to them? From their perspective, wouldn't the universe be timeless? How old is the universe relative to our reference frame on Earth?

So ends 20 questions...

 

[Wiccan_Child]

I have a question about the age of the universe...

Supposedly the universe came into existence 13.7 billion years ago, but according to Einsten's Special and General Relativity, all frames of reference are valid and there is no universal reference frame.

Yep.

Reading up on the subject, I discovered that astronomers use a specific reference frame called the cosmological reference frame that has something to do with the background radiation being the same in all directions. Why is this reference frame more valid than any other reference frame? Wouldn't relativity mean that depending on how fast your frame of reference has been moving, the age of the universe varies? What about particles that move at light speed? How can a reference frame be applied to them? From their perspective, wouldn't the universe be timeless? How old is the universe relative to our reference frame on Earth?

So ends 20 questions...

The universe is still 13.7 billion years old (assuming the 'start' was the beginning of the Big Bang). Relativity says that the time it takes for something to travel between two points depends on how fast your inertial frame is moving.

So if I'm on a spaceship that travels from Earth to Alpha Centauri, the clock on my ship tells me it took Δt seconds to travel there .
But someone on Earth who's watching me measures my transit time to be Δt' seconds (notice the ' inverted comma).

The relationship between Δt and Δt' (i.e., how long it I think it took, and how long Earth thinks it took) is given by:

Where v is how I'm travelling with respect to Earth, and c is the speed of light.
If my speed is very small, then this factor γ is very close to one. So, when I travel slowly, there is very little difference between my perception of the transit time time and the Earth's.
But if I travel very fast, this γ gets very large, meaning that the Earth's sees me taking a very long time to travel between the two points (which is slightly counter-intuitive, because we're used to things taking a shorter time if they go faster).
This phenomenon is called time dilation, and only has to do with how a moving clock ticks slower than a (relatively) stationary clock.
Apologies if you already knew all this .


Basically, this has nothing to do with the age of the universe: the time between the start of the Big Bang and the present moment doesn't change. What does change is that, as you travel faster, everyone else moves faster too. You're still at the same time interval as them (if you imagine everyone on a timeline, we're all moving along it at the same speed (1 second per second). But fast-moving objects undergo processes slower than relatively stationary objects (we age slower on spaceships than people on planets, for example)).

In other words, the universe is 13.7 billion years old .


With regards to particles moving at the speed of light... yes, they don't experience time like we do. If we try to apply time dilation to them, everything ends up happening at once (which would explain how a photon travels all possible paths at once...).

 

[Penumbra]

Yep.

The universe is still 13.7 billion years old (assuming the 'start' was the beginning of the Big Bang). Relativity says that the time it takes for something to travel between two points depends on how fast your inertial frame is moving.

So if I'm on a spaceship that travels from Earth to Alpha Centauri, the clock on my ship tells me it took Δt seconds to travel there .
But someone on Earth who's watching me measures my transit time to be Δt' seconds (notice the ' inverted comma).

The relationship between Δt and Δt' (i.e., how long it I think it took, and how long Earth thinks it took) is given by:

Where v is how I'm travelling with respect to Earth, and c is the speed of light.
If my speed is very small, then this factor γ is very close to one. So, when I travel slowly, there is very little difference between my perception of the transit time time and the Earth's.
But if I travel very fast, this γ gets very large, meaning that the Earth's sees me taking a very long time to travel between the two points (which is slightly counter-intuitive, because we're used to things taking a shorter time if they go faster).
This phenomenon is called time dilation, and only has to do with how a moving clock ticks slower than a (relatively) stationary clock.
Apologies if you already knew all this .

No apologies necessary, but I am familiar with the basic application of relativity. I've had physics classes where I had to understand it quantitatively, at least to a certain depth.

Basically, this has nothing to do with the age of the universe: the time between the start of the Big Bang and the present moment doesn't change. What does change is that, as you travel faster, everyone else moves faster too. You're still at the same time interval as them (if you imagine everyone on a timeline, we're all moving along it at the same speed (1 second per second). But fast-moving objects undergo processes slower than relatively stationary objects (we age slower on spaceships than people on planets, for example)).

In other words, the universe is 13.7 billion years old .

With regards to particles moving at the speed of light... yes, they don't experience time like we do. If we try to apply time dilation to them, everything ends up happening at once (which would explain how a photon travels all possible paths at once...).

Maybe I'm slow, but I still don't get it.

Let's assume a space ship leaves earth traveling very quickly. On Earth time, they travel for a year. On the space ship, they haven't experienced a year of time yet, because they witness time as passing more slowly. If you ask them both how long ago the ship left earth, wouldn't you get different answers? Earth people would say a year, space people would say a few months. Or am I missing something???

If we apply that to the Big Bang, let's assume two particles begin traveling at time = 0. If, over the last 13.7 billion years, one of the two particles has been traveling at an average velocity that is higher than the previous one, wouldn't the two particles have experienced different lengths of time since they began traveling?

Let me know where my misunderstand is.

 

[Wiccan_Child]

No apologies necessary, but I am familiar with the basic application of relativity. I've had physics classes where I had to understand it quantitatively, at least to a certain depth.

Kewl .

Maybe I'm slow, but I still don't get it.

Let's assume a space ship leaves earth traveling very quickly. On Earth time, they travel for a year. On the space ship, they haven't experienced a year of time yet, because they witness time as passing more slowly.

Not quite: they witness time going normally in the spaceship, and going slow outside.

A person on Earth sees their watch go normally, but a clock on the spaceship tick slowly. But confusingly, a person on the spaceship sees Earth's clocks running slowly! This leads to the wonderful world of simultaneity: events that are simultaneous in one inertial frame might occur at different times in another frame.

So someone driving alongside a train at a slightly lower speed than the train's speed (as measured by an observer on the train station) measure two events on the train to have occurred at the same point in time. But the observer on the platform sees the two events as occurring at different points in time.

Confused? It's all relative, m'dear.

If you ask them both how long ago the ship left earth, wouldn't you get different answers? Earth people would say a year, space people would say a few months. Or am I missing something???

You'd get the same answer: there is nothing special about the spaceship that would make its answer differ to the Earth's.

If we apply that to the Big Bang, let's assume two particles begin traveling at time = 0. If, over the last 13.7 billion years, one of the two particles has been traveling at an average velocity that is higher than the previous one, wouldn't the two particles have experienced different lengths of time since they began traveling?

The question makes no sense, because you've assumed absolute motion. One of the fundamental points about relativity is that motion is relative (hence the name ). It makes no sense to say one particle is travelling faster than the other without defining some origin point (or a stationary observer, or whatever). Moreover, each particle sees itself as stationary, and the other particle moving away.

So particle A sees particle B whizzing away at some speed v, and thus sees B's clocks ticking slowly and sees B as being shorter than when it stationary (relative to A).
B also sees the same things about A.

A sees itself as being of normal length and its clocks ticking normally, but so does B. Length contraction and time dilation are phenonema observed by stationary observers watching moving objects. People on the moving object see themselves as being the stationary objects, and the previous observes as being the moving ones.

I hope I made sense! Relativity boggles everyone .