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If the universe is 13.8B years old, how can we see 46B light years away? (2018)

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Re: If the universe is 13.8B years old, how can we see 46B light years away? (2018)

#31

Post by beisner »

coding123 wrote: post #29

I feel like we are all idiots repeating "space is expanding" if humans could live 14billion years in age, and we were present when it started, but we left good old Bob on the part of the universe that was travelling away from us, he would have traveled FTL from us. Even if you said space expanded, the traveling has been accomplished. So now we know that space expansion is how you travel FTL. In other words if humans…

Just a minor technicality, it’s not that Bob travelled faster than the speed of light, it’s that the distance between you and Bob increased faster than the speed of light. Nothing can travel FTL through space, but space itself can be made smaller or larger.

Re: If the universe is 13.8B years old, how can we see 46B light years away? (2018)

#32

Post by ssijak »

If you are turning in bed and can't sleep I'll give you some questions to think about. Even though some are non-sensical in a way, they are a good starting point to ponder about:

- Is space really flat (infinite) or curved (finite)?

- If it is flat and the universe had the beginning (big bang) then does it just have "potential infinity", by ever-expanding?

- If it is curved is it implied that it is encompassed by something that has at lease 3+1 dimension into which it is curving?

- What would happen if you would happen to stand at the edge of space/universe and push a hand through the edge?

- Space could be infinite but at the same time with a boundary. Can you imagine that boundary without trying to imagine what it is bounded from?

- Where does new space, created by the universe expansion, come from?

- What is space fabric actually made from? Is it discrete or not.

- Are there other universes outside ours?

- If there are, do we live in an infinite Russian doll type of universes?

- What gives the initial conditions and laws in the universe?

- If the universe is cyclic or there is a multiverse, are there universes with totally different laws and if yes what generated/allowed that?

- Try to imagine nothing.

- Try to imagine infinite.

- You can't imagine how any of these 2 things would work (nothing or infinite), but one or both must exist. Either all existence existed in some way forever, or it had some genesis from nothing.

- Is there free will?

- Can you even imagine a proper mechanism that would allow for free will to exist?

- What would prevent you from "cutting" the smallest possible particle in 2 parts?

- Are there several dimensions of time?

- Is there a beginning of time?

- Is math invented or discovered?

- Can we ever, in theory, discover every law in the universe if we are looking at it only from the inside.

- Try to imagine 4.5 billion years of evolution (or more if life crashed to earth from a comet). How many organisms lived, and died, how many actions were made, how many found a partner and reproduced for you to be here and read this text at these exact moment. How many chances for failure at any point in that period were there?

...

Enough for tonight. Happy dreaming.

Re: If the universe is 13.8B years old, how can we see 46B light years away? (2018)

#33

Post by mellosouls »

lmilcin wrote: post #25

And... another author that doesn't get it or looks for a controversial, clickbaity title. The correct way to state it would be to say: "We are seing things that are currently 46B light years away but since they are so far away we see them as they were 13.8B years ago when they were much closer than they are now." I see absolutely nothing difficult about that statement unless you really need to create some piece of co…

Your dismissal underestimates the qualifications and pedigree of an established and excellent populariser of "cool" scientific topics.

Sure he goes for clickbaity articles now and then, but he's pretty good at them in my experience, and your summary is both incorrect (there is no "current" over that distance scale) and leaves all explanation out.

Re: If the universe is 13.8B years old, how can we see 46B light years away? (2018)

#34

Post by Retric »

Zenst wrote: post #26
nvrspyx wrote: post #20

If what we’re seeing was 13.8B light years away 13.8B years ago and are now 46B light years away, wouldn’t that mean that those things traveled ~32.2B light years in 13.8B years. Wouldn’t that thus mean they travelled faster than the speed of light? Maybe I’m misunderstanding though. EDIT: I guess you also have to take into account the expansion of the fabric of space as well and not just the movement of the galaxies…

Interesting ratio of 1:3.3141210374639769452449567723343 not exactly Pi. But then that expansion ratio may of been different over time, but it is a bit like sampling the second hand on a clock in a photo and working out the entire motion and workings of the clock - at least on the scale of the data/measurements we have and the age of the universe. Currently we are still not 100% sure when midnight was, but as always…

We have more recent data on closer objects. It’s a sequence of thin shells that expands as you go backward in time, or a 3D light cone aimed backward in 4D space time. https://en.m.wikipedia.org/wiki/Light_cone

Re: If the universe is 13.8B years old, how can we see 46B light years away? (2018)

#35

Post by gesman »

All this assumes that time is a single thing (sort of gigantic X-axis with "t") that works for everyone in universe equally.

What if we have multiple (billions) of realities with their own t-axis and with us being only one of these with our own timeline?

Re: If the universe is 13.8B years old, how can we see 46B light years away? (2018)

#36

Post by rhinokungfu »

nvrspyx wrote: post #20

If what we’re seeing was 13.8B light years away 13.8B years ago and are now 46B light years away, wouldn’t that mean that those things traveled ~32.2B light years in 13.8B years. Wouldn’t that thus mean they travelled faster than the speed of light? Maybe I’m misunderstanding though. EDIT: I guess you also have to take into account the expansion of the fabric of space as well and not just the movement of the galaxies…

Some of the confusion is, I think from referring to speed of light as "speed of light". When it really is speed limit of causality between 2 points in space. And light (em waves) just happen to be able to hit that limit. Now since expansion of space is itself not going to allow one point in space to cause any effect on another, it (the expansion) can be faster than speed of causality.

PBS space time has a good video on this - https://www.youtube.com/watch?v=msVuCEs8Ydo

Re: If the universe is 13.8B years old, how can we see 46B light years away? (2018)

#37

Post by rhinokungfu »

hunter2_ wrote: post #9
leonroy wrote: post #3

Earlier quoted context omitted.

The universe is expanding, at a rate which I believe is heading past the speed of light. This limits our ability to reach galaxies further away from us as they are speeding away faster than we could conceivably travel since our engines would of course be bound by the speed of light. Some more info: https://www.forbes.com/sites/startswithabang/2016/06/10/can-...

Why would some things be bound by the speed of light and not others? I always thought of this limitation as an all-or-nothing law.

Posted this to a point above, but probably more pertinent here, so reposting - Some of the confusion is, I think from referring to speed of light as "speed of light". When it really is speed limit of causality between 2 points in space. And light (em waves) just happen to be able to hit that limit. Now since expansion of space is itself not going to allow one point in space to cause any effect on another, it (the expansion) can be faster than speed of causality. PBS space time has a good video on this - https://www.youtube.com/watch?v=msVuCEs8Ydo

Re: If the universe is 13.8B years old, how can we see 46B light years away? (2018)

#38

Post by kr4 »

ssijak wrote: post #32

If you are turning in bed and can't sleep I'll give you some questions to think about. Even though some are non-sensical in a way, they are a good starting point to ponder about: - Is space really flat (infinite) or curved (finite)? - If it is flat and the universe had the beginning (big bang) then does it just have "potential infinity", by ever-expanding? - If it is curved is it implied that it is encompassed by som…

I can give one thing for you to ponder: what's the true difference of the world you experience in the waking state and the world you experience during dreaming state and the cause behind both of these? The puzzle of the universe, infinity and multiverse can become apparent if you ponder over the above question.

Re: If the universe is 13.8B years old, how can we see 46B light years away? (2018)

#39

Post by jeffdavis »

lmilcin wrote: post #25

And... another author that doesn't get it or looks for a controversial, clickbaity title. The correct way to state it would be to say: "We are seing things that are currently 46B light years away but since they are so far away we see them as they were 13.8B years ago when they were much closer than they are now." I see absolutely nothing difficult about that statement unless you really need to create some piece of co…

It's at lesst a little confusing how something went from 14B light years away to 46B light years away (seems to be a distance of 32B light years total travel) in 14B years.

Re: If the universe is 13.8B years old, how can we see 46B light years away? (2018)

#40

Post by cortesoft »

nvrspyx wrote: post #20

If what we’re seeing was 13.8B light years away 13.8B years ago and are now 46B light years away, wouldn’t that mean that those things traveled ~32.2B light years in 13.8B years. Wouldn’t that thus mean they travelled faster than the speed of light? Maybe I’m misunderstanding though. EDIT: I guess you also have to take into account the expansion of the fabric of space as well and not just the movement of the galaxies…

Yeah, the intuitive view of universe expansion is that it expands from the edges out.... but in reality, it expands everywhere at once, so really the space between us is expanding as well.
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