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/sci/ - Science & Math

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2367910 No.2367910 [Reply] [Original]

Ok, i am trying to grasp this concept but i think i am missing something.

If you look deep enough into space you can see what the Universe looked like in its early stages. But the universe is also expanding. Does that mean that all of the galaxies and stars you see looking deep into space are no longer there? Or how should i put it better.

They aren't still there but they once were, and now what we see is galaxies that could actually be somewhere else.
But if the universe is expanding does that not mean that there should either be nothing there currently, or there are actually new things there that we can't see because the light hasn't reached us.

Basically want I am trying to figure out is, is that we have no idea whats going on right now FAR out in the universe because all we can see is the past?

Hopefully i explained that well enough, if not i can elaborate on certain parts

>> No.2367941

We can see back to the point where light existed in the Universe.

>> No.2367952

I can safely say this is the greatest question all astronomers ask them selves, then turn to god for reassurance for. in theory the universe is expanding so what we see from the naked eye is completely different from what we see from a powerful telescope just because of this theory. not because we see deeper into space but theoratically deeper into the past. Even though its expanding. its an incredibly hard concept to grasp

>> No.2367966

We can see back in time bike looking far enough away because the speed of light is not infinite. It takes a billion years for light to travel a billion light years, so when you look at something a billion light years away you are seeing photons it emitted a billion years ago. The object has almost certainly moved since emitting those photons.

Try thinking of it as watching home movies recorded years and years ago.

>> No.2367970

>>2367966
>We can see back in time bike looking far
>bike looking
>bike

>> No.2367974

>>2367952
Ok, well at least its a hard concept to grasp, I was thinking I was missing a few key components and making something easy to understand, harder than it should be.

So no matter how you look at space you are always looking into space, and at something that is no longer in the same position?

>> No.2367979

>>2367970
I meant to write "by". Why did I write "bike". This shall haunt me forever.

>> No.2367985

the basic idea of astronomy is you can never actually win, you can have a telescope so powerful it can loom 1000000 years into the past (light years in distance) but if you loo again 10 seconds later it will be different purely based on the theory that the universe is expanding.

I have a question, is ther univernse expanding faster than the speed of light? How can you tell? how can you measure it? i would like to know

>> No.2367986

>>2367952

>I can safely say... Turn to god for reassurance
>safely say... Turn to god
>turn to god
>god

>> No.2367987

>>2367979
I don't know. I found it funny. Shit like that happens a lot.

>> No.2367988
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2367988

>>2367974
>So no matter how you look at space you are always looking into space

Fuck, meant you are always looking back in time.

>> No.2367991

>>2367952
I thought everything in space stay where they are and space in between them were expanding making light expanded and slow down also.

>> No.2368006

Head is imploading, but I refuse toreturn /x/
Bump derp.
Herp.

>> No.2368013

>>2367991 everything in space stay where they are
No. Space is expanding, but objects are still completely free and regularly do move through this expanding space as a result of gravity and other forces. Try getting out out of your chair if you don't believe me.

>> No.2368012

I still don't get how this is a hard concept to grasp... It... Makes perfect sense to me...

Time is relative to light... If you look far enough, you're seeing "backwards" in time, from the point of origin. The light had to come from somewhere, a really long time ago, and really far away. By looking at it, were essentially seeing a snapshot of time itself progressing.

Not a hard concept to understand, but it's fucktarded to try to explain.

>> No.2368017

>>2367985
Thanks for more clarification.

I was reading up on things, and part of it was looking at a picture from the hubble telescope that showed a picture looking deep into space and that picture would basically show what was going on in the early stages of the universe.

But what was confusing me is that if the universe was expanding how would that be accurate. Because if we came from a central point wouldn't we have already received light from the center and instead we should be only getting light from newer sources.


But I think i was just thinking too hard and it wasn't clicking that we were just receiving old light and i wasn't grasping that this was the past not present.

>> No.2368018

>>2367974
>>2367974
Thats basically it, astronomy is measuring what we have seen, fuck all this dooms day shit. if we see a comet heading towards earth we have about 24 hours to live max. we cant predict comets that will hit in 100 years thats fucking sci fi shit. anything can happen within that time, or better yet did happen but we dont know yet. lol

>> No.2368024 [DELETED] 

>>2368018
Yep. We are safe as fuck. The earth depends just on us.

>> No.2368037

>>2368012
I already grasp that we are looking at the past basically when we look into space, but what i wasn't getting is how we are still seeing the beginning of the universe if we also started at the beginning. Shouldn't the parts in the center be expanding with us, so we should see newer light instead of light that old, unless we caught up with the light already sent out from long ago and we are seeing it now.

>> No.2368079

Well the closer you travel to the speed of the light, the closer to stopping time you get, though you dont actually stop time. In other words you look into space and can only look backwards because the universe IS expanding there is no possible way to loom foward unless you warpdrive or go sidewards in time.

If you travel 1 second off the speed of light for a year from the planet earth, the back. what seems for you is 2 seconds you will come back to planet earth 2000 years in the future. try put your head around that

>> No.2368083

then*

>> No.2368089
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2368089

>>2368079
Wait so are you saying the speed of light is time travel?

Cause you are confusing me and blowing my mind at the same time.

>> No.2368100

OP, you are completely right. Since you are looking into the past, the stars and galaxies could have died, smashed together into black holes, reformed new stars.
A lot can happen in 13 billion years.
Also, the structure of the universe 10 billion years ago is actually remarkably different to what we see today. Here's one thing: If you want to know what the universe 13 billion light years away might look like, look at the universe that's less than 1 billion light years away.
It'll be about the same.

>> No.2368103

OP, how much have you done in special relativity?

(I've done a little, but some of it still gives me a cramp in my head)

>> No.2368108

Thats exactly what im saying, and to make matters worse it all relates to to the universe expanding and why we see into the past and rather the present. which is why its hard to measure how muich faster than light the universe is travelling

>> No.2368106
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2368106

not me...the universe.

now you know why the general population says, "fuck this shit!" and elects to go have a beer and watch the game or react in a violent manner when you inquire for serious discussion upon the matter.

>> No.2368111

>>2368089
No, it's just time relatively slows down the faster you get to light speed. It's kinda nuts, but it's what happens.
So a clock going 0.99 the speed of light ticks slower than one going 0.1 times the speed of light. It's only time travel 'kinda'.

Oh and what I said about stars- you can only see galaxies when you're 13 billion lightyears away. You don't quite have the resolution to pick out stars.

>> No.2368129

>>2368108
>>2368106
>>2368100
Well i am glad it is a generally confusing topic and I am not missing something easy. I understand whats going on a lot more than before.
Just the universe expanding and then looking into the past was confusing me at first because everything you were looking at wouldn't be there anymore/how are we seeing it if we are also expanding along with everything else.

>>2368103
Same as you, just a little.

>> No.2368141

>>2368111
Ok that makes a lot more sense. i understand now.

Still fascinating.

>> No.2368144

>>2368111
>>2368111
this is correct , the closer you get to the speed of light the slower time travels, but only in space and you cant ACTUALLY stop time. its imposssible. BAD LUCK RAPSTS unless you invent a machine that manipullates time and matter. have fun with that

>> No.2368148

>>2368129

Time slows as you near the speed of light, length becomes smaller, mass becomes larger; it's all a mind-fuck.

>> No.2368162

>>2368148
>>2368144
This is why i love science, i love the feeling of my mind being blown/trying to grasp certain concepts.

It's even more satisfying when it begins to make sense.

>> No.2368166

>>2367910 1)
>>2368089 2)
1) Firstly yes, we are seeing into the past, where objects used to be oriented with respect to us thousands/millions/billions of years ago. If we ever wanted to travel to a distant star in the sky, we wouldn't want to travel in the direction that we saw the light. If we did, we'd be travelling in the direction that it used to be, and as we got closer - still following the light - we'd eventually trace out a giant arc, chasing the star's path through the universe.

2) Secondly, light is a sort of cosmological constant of the universe - its the limiting speed at which things can travel. Einstein, with the help of generations of mathematicians and physicists, related light to time and space in what is called a Lorentz transformation. If you study this transformation, it says that nothing can travel faster than the speed of light. If you pretend for a moment that an object can, then you'll find that time is reversed from that objects perspective.

TL DR: 1) Yes, the star's image is older than your grandma.
2) If things go faster than light then they go backwards in time.

>> No.2368168

>>2367974
>something that is no longer in the same position?

You're asking whether something is in the same position at a later time.

In special relativity, in order to answer whether something is in the same place at a later time, you MUST specify the reference frame.

In general relativity (needed for cosmology), this all breaks down. Special relativity and its inertial reference frames only work approximately, and only over short distances and times.

You can introduce coordinate systems, and talk about an object being at the same x, y, and z at a later t, but those coordinate systems are just a tool for calculation. They're not real. And the answer you get depends on what coordinate system you use.

The best answer is to switch to the spacetime perspective. From the spacetime perspective, the answer "is something in the same place after some time has past?" is obviously no -- since it's at a different time, it's not at the same point.

>> No.2368172

>>2368162

I'm a sophomore physics major and it still doesn't make sense. I'm taking Quantum this year and my teacher's hilarious. He'll constantly remind us that "[scientists] don't even understand this stuff".

It's interesting as hell though.

>> No.2368177

>>2368166
2) is a mistype. Should read: the object goes backwards in time from everyone else's perpective. From the object's point of view, it's still moving forwards in time, and everything around it is moving backwards

>> No.2368189

>>2368166
>>2368168
I made a point somewhere else that i left out of my main topic.

But if the universe is expanding. How do we know we are looking towards the center to see the early stages of the universe? and how is it that we are seeing the light from those stages if we started off in the center also?

That is what really gets me and what i wasn't able to explain at first.
Unless...and i may answer my own question. If we are looking at the opposite side of the universe we are still getting light from the beginning because those galaxies are heading in the opposite direction.

>> No.2368194

>>2368166
>2) If things go faster than light then they go backwards in time.

How? I don't understand this part.

>> No.2368206

>>2368189

I can't answer you question exactly, but I think it has to do with the Doppler Effect (that's my educated guess, but don't quote me on it)

>> No.2368209

>>2368189
There is no center of the universe. The Big Bang happened everywhere, and ever since, from any part of the universe you'll see everything else moving away from you.

You see earlier stages of the universe when you look farther out because the light takes time to get to you.

>> No.2368217

>>2368194
It's not true.

It is true, however, that an object moving faster than light in one reference frame is moving backwards in time in another.

>> No.2368218

for more on the whole "time travel at the speed of light thing" see Time Dilation on wikipedia. It has actually been proven using atomic clocks (dilation due to gravity) and particle accelerators(dilation due to velocity).

http://en.wikipedia.org/wiki/Time_dilation

>> No.2368225

>>2368209
>There is no center of the universe. The Big Bang happened everywhere
>there is no center

Holy shit my mind has been blown for the 3rd time tonight.

Every time i learned or was taught about the big bang, i either missed that part, or assumed it was from a central point.
But if it started everywhere, well then that makes everything make complete sense now.

Thanks, things are a lot clearer now.

>> No.2368238

A good way to see is look at the different Hubble deep field images. The first image taken that was taken purely from the light frequency we can see (i.e., if Hubble had an eye piece and you looked through it, you'd see what Hubble saw), you see all the galaxies there etc.

Take the next Hubble deep field image that was taken at near infrared and the galaxies have moved slightly.

Get the image that was taken at infrared and they've moved again.

If you find the most redshifted Galaxies on there. The chances are them Galaxies are no longer there.

>> No.2368239

>>2368209

Isn't there a coordinate-center though? Like, granted I've never done much with astrophysics, but there's always that "inflating balloon" analogy. Couldn't we find the center of the Universe like we could find the "center" of a balloon?

>> No.2368240

>>2368189
Let me clarify this more. The light that we're seeing isn't from the early universe, that light is long 'gone'. Keep in mind that the rate at which our planet is moving away from everything else is far less than the speed of light, so the light from the early universe has definitely outpaced us by now.
The light that we're seeing, and it's apparent 'delay' is a consequence of the distance between us and the emitting star. If the star is 12 million light years away from us, then the light will take (12million + the time it takes light to travel any extra distance we move away from the star's initial point) year to reach us.

>> No.2368250

>>2368240
Ok, thats even more clarification.
I think all my concerns have been answered now. A few new ones have popped up but its more speculation then anything.

A lot of things make a lot more sense now to me though.

>> No.2368255

>>2368240
> The light that we're seeing isn't from the early universe, that light is long 'gone'.

That's wrong. We can detect light all the way back from the time the universe first cooled down enough to become transparent. Before then it was a glowing red plasma.

Of course, due to extreme redshift, we have to detect that early light with a microwave receiver.

http://en.wikipedia.org/wiki/Cosmic_microwave_background_radiation

>> No.2368271

>>2368255
Note the ' ''s around gone

>> No.2368283

If you want a relatively easy way of visualizing the connection between of time, the speed of light, and relativity, look up light cones :D