A question about time

[Ratman]

I'm confused. Can the speed of light be broken?

In the first attosecond did not the universe expand faster than the speed of light?

I know there must be some obvious answer that presently escapes me.

 

[IrBubble]

I'm confused. Can the speed of light be broken?

In the first attosecond did not the universe expand faster than the speed of light?

I know there must be some obvious answer that presently escapes me.

Well, the expansion of the universe is still accelerating.

 

[ImprobableJoe]

I'm confused. Can the speed of light be broken?

In the first attosecond did not the universe expand faster than the speed of light?

I know there must be some obvious answer that presently escapes me.

I'm willing to take a swing at it, although I'm no expert and I'm just giving a VERY rough idea of my understanding of the concepts.

When we talk about "speed of light" there is an implied and sometimes stated concept of that being the speed light travels, dependent on the medium through which it travels. The speed of light in a vacuum is higher than the speed of light through air or water. That's why when you stick a pencil in a glass of water, the pencil looks like it has a crook in it.

The speed of light in the air is faster than the speed of light in the water.

In the same way, in that first moment of space-time, the universe was expanding into nothing. Not vacuum, but literally nothing in a way that is really difficult to understand. Vacuum is the absence of stuff. The nothing that the universe expanded into was an absence of space-time.

In a similar way(perspective-wise, if not physics-wise) that the speed of light in air is faster than the speed of light in water, the speed of expansion into nothing can be faster than the speed of light in a vacuum.

 

[JacobEvans]

If you go faster than the speed of light in medium you can even get some cool glowing radiation!

 

[ninja_lord666]

Theoretically speaking (according to Einstein's Relativity), in order for an object with matter to go the speed of light, it would need infinite energy. Therefore, it would be very simple to go faster than the speed of light. All you'd need is more than infinite energy.

 

[IrBubble]

Theoretically speaking (according to Einstein's Relativity), in order for an object with matter to go the speed of light, it would need infinite energy. Therefore, it would be very simple to go faster than the speed of light. All you'd need is more than infinite energy.

Well, energy cannot be utilized to accelerate something past luminal speeds since it travells in luminal speed.

 

[ninja_lord666]

Well, energy cannot be utilized to accelerate something past luminal speeds since it travells in luminal speed.

Oh, come on! Of course it's possible! I just need to find some way to produce > ∞ Joules...Let's see, a typical fire produces around 5000-6000 Joules, so I'll need...*begins counting fingers*...an infinite number of fires? Ah, screw it. I'll just try and find a bottle of liquid Schwartz. That'll work.

 

[JacobEvans]

Theoretically speaking (according to Einstein's Relativity), in order for an object with matter to go the speed of light, it would need infinite energy. Therefore, it would be very simple to go faster than the speed of light. All you'd need is more than infinite energy.

But then according to the Lorrentz Equation the object's time would be the square root of a negative number, so you'd enter the realm of imaginary time.

 

[ninja_lord666]

But then according to the Lorrentz Equation the object's time would be the square root of a negative number, so you'd enter the realm of imaginary time.

Imaginary time!? Damn, I need to check out that Lorrentz guy...

 

[IrBubble]

That really tickles your imagination

Please press the red button for desired effect.

 

[imorio]

But there was also the conclusion that there could exist particles which go faster than the speed of light and need infinite energy to go slower than the speed of light?

Idea for a perpetuum mobile: making a machine that gains energy by slowing down particles that go faster than the speed of light=infinite energy!

 

[Ciraric]

That's why when you stick a pencil in a glass of water, the pencil looks like it has a crook in it.

I always though it was to do with the differences between the refractive indices of the water, the air and the glass.

 

[ImprobableJoe]

I always though it was to do with the differences between the refractive indices of the water, the air and the glass.

What do you think a refractive index is? From Wikipedia:

The refractive index (or index of refraction) of a medium is a measure of how much the speed of light (or other waves such as sound waves) is reduced inside the medium. For example, typical soda-lime glass has a refractive index of 1.5, which means that in glass, light travels at 1 / 1.5 = 2/3 the speed of light in a vacuum.

 

[ninja_lord666]

I always though it was to do with the differences between the refractive indices of the water, the air and the glass.

Yes, and the refractive indexes are based on the speed of light through that medium.

n = refractive index
c = speed of light (in a vacuum)
v = phase velocity for the specific medium

 

[IrBubble]

But there was also the conclusion that there could exist particles which go faster than the speed of light and need infinite energy to go slower than the speed of light

There are tachyons, but I don't think you'll have any luck catching them, as they are both hypothetical and travel backwards in time.

 

[Marcus]

To return to the original question, this is part of the misconception that the Big Bang was an explosion in space. It's perfectly true that no explosion (or part thereof) can move through space faster than the speed of light. However, there is no such limit on the rate of expansion of space, which is what was going on at the BB.

 

[Ciraric]

Yes, and the refractive indexes are based on the speed of light through that medium.

n = refractive index
c = speed of light (in a vacuum)
v = phase velocity for the specific medium

Well darn my tooting.

I never took physics past (very) early University level.

 

[ninja_lord666]

Well darn my tooting.

I never took physics past (very) early University level.

University? I learned about refractive indexes in high school.

@ Marcus: An expansion of space and time. Don't forget that last part. I'm thinking the reason that the universe is expanding faster than the speed of light is because it's space and time that are expanding. Distance/time = speed. I'm sure this whole expansion thing is seriously messing around with distance and time. For all we know, it could be expanding slower than the speed of light but due to the creation of new space and/or time, it seems faster.
Now, I have nothing to back this up, obviously. I'm just making what seems like a logical guess. You know, for the sake of discussion.

 

[Ratman]

To return to the original question, this is part of the misconception that the Big Bang was an explosion in space. It's perfectly true that no explosion (or part thereof) can move through space faster than the speed of light. However, there is no such limit on the rate of expansion of space, which is what was going on at the BB.

Thanks Marcus for this answer.

Let me attempt to re-state my original question.

If you left Earth at the speed of light after 400,000 years you would have only just left the Milky Way galaxy. The "Local Group" is 10 million light years in diameter. This all seems slow in comparison to the size and scale of the entire universe.

To my untrained mind I wondered if the rules were different during the first attosecond of expansion, right after the Big Bang.

Are either of these statement true?

1: As space expanded to fill in the void, where nothing existed before, the constraints of the speed of light had no effect.

2: Or, Space continues to expand at the speed of light and over the next 14 billion years reached it's current size. It can never exceed the speed of light.

Thanks to all who have attempted to educate me on this issue.

 

[Pulsar]

The speed of light is the maximum speed of a particle (more precisely, a massless particle) traveling through space, as described by special relativity.

The expansion of space itself is described by general relativity. It has nothing to do with the speed of light. In fact, the expansion rate isn't a velocity at all: the best way to describe it is an increase of the amount of space.

As a consequence, distant galaxies 'riding along' within the universe recede from each other, with an apparent velocity: the further away a galaxy, the faster it appears to move away from us. It's not a physical velocity, they don't travel through space (apart from their local environment).

Because of this observational effect, it is convenient to express the expansion rate of the unverse in terms of this apparent velocity: the Hubble constant,

H0 ~ 72 km/s/Mpc,

where 1 Mpc = 1 Megaparsec = 3.26 million lightyears. So, it's not a velocity either, but a velocity per distance. So galaxies with a proper distance larger than c/H0 ~ 13.6 billion ly appear to move faster than the speed of light. This distance c/H0 is called the Hubble sphere. And no, this is not the entire observable universe: we can see much further, upto a theoretical limit of 46.5 billion ly.

1: As space expanded to fill in the void, where nothing existed before, the constraints of the speed of light had no effect.

The constraints of the speed of light had no effect, not during the inflation period, and not today.