/sci/ - Science & Math

God did it.

>you can't see the clock ticking so that means it isn't?
WELL I'M GOING TE LET YOU MEDITATE ON THAT QUESTION

>implying anyone on /sci/ has more than a highschool education if that considering most are that smug asshole who drops out because he's "too smart" when it's really jsut because he's a lazy bum

TBH, I want someone to explain time dilation to me too.
I consider myself fairly smart, but as it stands, it's perplexing to me that time suddenly starts going wonky as you begin to travel at higher speeds.

Why does reality start going haywire?

>PhD in mathematics
>any jon i want
>300k starting

I only barely get time dilation, but I think it's that as you approach the speed of light, time slows down for you, so something that is a 20 year trip seems like 2 months, and you will have aged 2 months.

>>1488450
>Why does reality start going haywire
Why do any of the laws of physics happen? They seem natural to us, but it's really just because. Just because.

>>1488451
See, I know that- but I'd like some guy who knows his shit to explain that to me.

I mean, YOU are going faster.You are going from point A to B. Why does suddenly time go HURRRR and fuck you up? The whole point of going fast is to save time in travel.

Is our universe an asshole or something?

>>1488452
Yeah, I get that much. Travelling at 87% of the speed of light makes you age half as fast. I've read the Ender's Game series and they talk about it a lot, so I don't have trouble understanding how it works, but rather why it works.

>>1488460
Special Relativity and Time Dilation are a major boner killer for an aspiring science fiction writer like me.

I like Hard Science Fiction, but goddamn if the universe takes great pains to make shit boring.

Thats why travelling at high speeds is kinda pointless.. because by the time you get there chances are they'd have discovered some other more efficient way of getting there.. and then you'd be all like.. Hai.. Im from the 80's.. wots your name.. there might be some interesting applications tho.. hehe.. I could like put all my food in this high speed thingy.. and then 10 years later it would still be fresh :D

>>1488469
Look at Forever War. They did it well.

In effect, there's nothing special about approaching light speed. Time is not universally fixed at all, but rather is relative to velocity. If you get up and walk around, time is passing slightly slower for you than when you sit still.

The effect just isn't perceptible until you get to relativistic speeds.

The reason why it works is because time passes normally for you.. but not for everyone else..

>>1488469
FUCKING ENDER'S GAME, MAN.

ENDER'S GAME.

>>1488492
Yes, but why is that? Is there a reason beyond what you just said?

So the way I had it explained to me, all things are moving through the spacetime continuum at the speed of light. However, the speed is diverted to both spatial and temporal travel. So when you travel faster, less speed goesto temporal movement.

>>1488462
>Is our universe an asshole or something?
No. On the contrary, out universe is quite a bro, actually.

If FTL technology proves to be impossible to create, time dilation may well be the key to interstellar travel. The biggest barrier to sub-light space travel is the long amount of time it takes to get anywhere; travel times are limited to a single human lifespan. However, if time is passing much slower for the crew, a lengthy voyage could pass in only a few years, allowing the crew to reach their destination alive and well, despite centuries having passed on Earth.

>>1488506
Wow. Okay.

>>1488492
>>1488490
OK, I get the goddamn effects!
The faster I go, the more noticeable the temporal slowdown for the objects in motion.
I need further understanding, though.

But here's a question.

If I leave from Earth to Alpha Centauri. I travel, say at 80+% of light speed.

Let us presume that going at that speed, my MATH tells me that I SHOULD arrive within X amount of time. After all, I can take my speed and distance, and calculate how much time I should take to arrive.

Let's say it SUPPOSEDLY takes me (throwing out a number) 5 years.
What happens to me?Do I age SLOWER?Am I actually not traveling as fast as I think I am?
I need context, please.

>>1488518
OP here, dunno if I can give you the deeper understanding you're looking for, but I can tell you that, yes, you WILL age slower. You'll be moving at 80% the speed of light and arriving in 5 years according to an observer, but to you it will feel more like 3 years (no idea why, which is what I want to find out).

>>1488518
Yeah, you'll age slower.

If the journey really takes five years, you might have only aged one year, and only have perceived the journey as having taken a single year.

There is an interesting problem here, in that you would have to take care not to overshoot your destination, expecting to travel five years, but arriving there in what seems to you like a single year.

Okay, thanks everyone.
I'm not op, but I 've always wanted to understand this a little better.

It's kinda convenient, actually, and I never thought about it.It's a little like cheating. (Trip takes 5 years? Lol, you only experienced 3!)

However, on a COMPLETELY unrelated note, how feasable is it to build something that goes 50% and up of the speed of light?

Is it even possible?

>>1488543
At the moment, no one has figured out a way to do it and probably won't for many centuries. However, it's likely that it'll happen eventually.

>>1488518
Depends what you mean by it takes five years. If it takes five years from a reference frame on Earth, then it might only take you one year in your own reference frame. From the Earth you will be travelling at 80% of the speed of light, in your reference frame the distance that used to look like five light years will look like one, and will approach you at 80% of the speed of light.

>>1488543
Very infeasible at the moment. The lack of friction in space gives a good medium though.

>>1488551
WAIT.

This has something to do with that whole 'speed of light is a constant' thing, doesn't it? You're not saying that you feel yourself travelling faster, but rather that your destination travels towards you to compensate for the lost time?

>>1488534
There is no why. it just is how it is. Like if you asked why e = mc^2 its just how it is. Sadly that's the best answer i can give you.

>>1488568
that's part of it. but then you'd ask why that is. it simply is

>>1488462
>Why does suddenly time go HURRRR and fuck you up?
"Why" on this level is not a scientific question, it's a philosophical questions.

Why do protons and electrons have opposite charges?
Why are neutrons composed of two down and one up quarks?
Why are there limits on the velocity with which one can travel?

Our Universe has certain properties that are natural to it. Asking why it has them is missing the point of science by suggesting that it's either purposeful for it to have those properties or that by revealing the answer you wouldn't arrive at the "why" question on a lower level again.

I feel sad knowing that while I can now understand the effects better (thanks again, fellas), I think that in my lifetime, I'll never learn the why.

Why is such an important thing, guys.Being told "Just because that how's it works"...is just a downer.

Maybe the LHC?

>>1488568
One important thing in relativity(and physics in general) is that you're stationary in your own reference frame and everything else is moving relative to you. It's not possible to tell how fast you're going unless you have an outside reference.

But yeah, if you accelerate then space contracts around you, possibly turns funny colours too with doppler shifting.

>>1488582
I doubt the LHC will explain a lot. The particles move pretty quick, but they're probably looking more at the protons than the photons, if you know what I'm sayin'.

>>1488477
But that's the cool thing. If you have the technology to accelerate yourself up to 0.999999999999% the speed of light (assuming you are protected from radiation, the course you plotted won't get you killed etc), you could set off toward the andromeda galaxy and get there in like.. a week lol ( didn't calculate that. I just picked an arbitrarily high percentage and then assumed it'd be fast enough to make the trip seem that short). then the funny thing is, you could get like a day into your trip before a million years pass. they dig up records of your voyage. they're like oh hey we have <insert epic FTL propulsion here> now. lets catch up and give it to em and then they'd like pull you out of speed safely and give you that shit.

Although they probably wouldn't look like what you and i call human anymore.

>>1488582
Sorry man. It sounds like faggotry but it kinda is what it is. Like maybe they'll explain the 'why' of gravity with the higgs boson. but then you'd have to explain the 'why' of the higgs boson. what if there's nothing (or at elast nothing for a long time) beyond the higgs boson? it'll just have to be accepted that it works the way it works, unfortunately :/

Hmm, theoretical applications.

Could I make a refrigerator whose outside shell vibrates/spins at a percentage of the speed of light, greatly extending my ability to preserve the shelf life of food?

After all, I could eat half of my sandwich, deposit it in my super refrigerator, start it up, and six months later, open it, and it's like I placed it inside a few minutes ago.

This is cool, no?

>>1488622
That's correct. That's pretty cool actually lol.

ITT many people who don't have a clue, some people who are misunderstood.

Let's go back to that Alpha Centauri example: Let's assume Alpha Centauri always holds the same relative position to the earth (distance stays the same). You travel at 80% speed of light to Alpha Centauri. While you travel someone sends a light beam to Alpha Centauri every five minutes that you can also recognize in your space craft.

The people on Alpha Centauri see that light beam every five minutes. They have the same perception of light as people on earth.
You on the spacecraft see the first beam while leaving earth. So far so good. But the second light beam does not come in after five minutes, because you are moving with 80% light speed. So it not only has to travel the 300s * c, but also the way that you have traveled in the mean time (think of a differential equation here, but the exact time doesn't matter), what takes more than five minutes.

So the people on earth and Alpha Centauri percieve the five minutes as five minutes, but you are moving relative to them and percieve the five minutes as a longer time.

Well if you guys can't explain the 'why', then how did Einstein figure it out? I don't even think anyone knew how to travel at the speed of sound when he came up with the theory. He used electromagnetism as his basis, didn't he?

read this http://en.wikipedia.org/wiki/The_Forever_War

>>1488626
That's more of the how than the why.

>>1488625

Sorry, that should say: They have the same perception of time as people on earth.

I don't see it as a question completely without a why answer. I see the speed of light as more of a speed of the forces of nature(or bosons), because light is just an electromagnetic wave, moving as fast as electromagnetism will allow. Makes sense that it should have a constant speed or else the universe would be crazy. Relativity basically follows from that.

>>1488625
That's just fucking weird.
You're going ridiculously fast, but you are also perceiving reality at a slower rate, because of some weird temporal loophole that occurs at near light speeds.

The applications are astounding.

Youtube search for carl sagan, time dilution, speed of light, etc.

You will find an explanation in laymans terms, and we won't think you stupid for watching it because we all love sagan.

I'm thinking of applications.

Same idea.

.9c Bed Chambers.

Are you the kind of man that has NO time to rest?24 hours in the day not GOOD enough for you?Buy one of our ridiculously expensive bed chambers, as the outside shell spins you at .9c, turning your hour of sleep into many!

Isnt that just lovely?

>>1488656
Awesome, you sleep for 8 hours and everyone thinks you've been gone for a week.

WAIT

So time travel is possible?

You go in an elliptical pattern so that you arrive at the earth in 100 years earth time, but you only experience, say 5 years.

You would have traveled to the future technically?

>>1488674
Wait, from what we;ve discussed on this thread, if you go at higher speeds, time slows down for you.

So, theoretically (lets presume you are one wasteful SOB), you could hop on your ship, cruise for what seems for a few days, but only a few hours have passed on Earth.

Is this not correct?

>>1488656

The problem here is, that you actually sleep a shorter time than the world outside. So while everybody had an 8 hours rest you only slept like 15 minutes.

If you want to be successful make everything else move 0.9c and the bed chamber stays steady.

But wait! When everything else moves relative to you, you move relative to them. Bummer.

>>1488674
Lol i guess he messed up D:. you'd have to make the rest of the world move faster to do that

>>1488694
Aye, that is not correct. Other way 'round.

>>1488656
actually, .9c would maybe turn one hour into a little more than two. Think of - what are they called - a hyperbola? It's kind of like that. At .9c you'd get noticeable but fairly minimal effects. At .99999999c, you'll outlive everyone you know in a matter of days.

>>1488700

But again, if the rest of the world moves faster, in fact they stay relative to each other and for them you move faster. So that concept doesn't work.

Okay, this is where it gets confusing.
This is getting fucking insane.

If I travel from point A to B at .9c, I only experience a % of the what I SHOULD have experienced due to time dilation.

This implies that if I have a 9.c vessel, I could extend ONE hour into many by going into my vesseland going vroom.Am I wrong?

>>1488717
You will experience less time than the people watching you.

>>1488717
Ok, I got it.
Time slows down for me, yadda, yadda, I actually LOSE time by going at .9c, not gain time.

>>1488710
>>1488717

Actually for you on the vessel it would turn your hour into a few minutes in your own perception. So your rest would be pretty short while everyone else has a one hour nap...

If you do that often you would get out overtired.

>>1488709
No. They'd experience time more slowly relative to you. so you could sleep 8 hours, rip em out of the super speed, then look at someone else's clock and realized only 5 minutes have passed :)

>>1488724
But you only lose time relative to everyone else. You're technically increasing your lifespan. Andrew Wiggin from Speaker for the Dead is 5,000 years old, but he only looks/feels 35 because of all the time he's spent travelling so close to light speed.

just because our laws of physics, human made constructs, don't permit faster than light travel, doesn't mean it isn't possible.

>>1488747
Screw the rules, I have money.

>>1488738

There are no absolute points, it is relative movement to the observer. In this case you would move relative to them, since they are the observers...

>>1488625
Wait, but when you slow down, the blips of light would catch up to you, wouldn't they? So then what's stopping time from cathing up to you too?

>>1488466
Science does not aim to find why, only how.

>>1488772

Define slow down. Do you mean stopping moving relative to them? That's right, if you hold the position relative to them, you will percieve the five minutes like them again, but you won't lose what you gained. The beams will hit you later than if you were on earth.

>>1488625
Just like dopplar shift?
That is incredibly groovy!

This is the bit that really confuses me...

Relative to the universe, you slow down and get shorter and heavier.
Relative to you, the universe slows down and gets shorter and heavier.

How the hell does this work?

>>1488787

Exactly. The dopplar shift works because if something approaches you, the frequency goes up and white light gets a bit more blue (towards ultra violet).

If something goes away from you, the frequency goes down and it gets red (towards infra red).

>>1488784
It's also worth pointing out that the speed of light, if you were to measure it on the ship, would still appear the same as the speed that would be measured on Alpha Centauri.

>>1488793
That means the visible light coming from the andromeda galaxy in my travel to andromeda galaxy at 99.9999999999999% the speed of light scenario would become gamma rays. osh

>>1488799
Why wouldn't it be...? I mean, the speed of sound is always constant too, right?

>>1488788

Well atctually you get heavier (have more energy) when you move faster. And you don't get shorter, but the perceptions get closer to each other ;-)

In the end it depends on the observer. So nothing is absolute, you always have a reference system and everything is relative to that reference system. So one of your statements is true at one time, but never both. It depends on who the reference system is. That is the basic concept of the theory of relativity.

>>1488788
>Relative to the universe, you slow down and get shorter and heavier.
You don't appear to slow down when you reach relativistic speeds.

>>1488803
No, the speed of sound depends on the medium it propagates in (and so does the speed of light actually).
The point is that if you move away from a source of sound, the particles that make up the mechanical wave will appear to move slower, while if you approach the source of a sound, they will appear to move faster - the subtraction and addition of speeds respectivelly is a good approximation at nonrelativistic speeds.

The problem is that it doesn't work that way with light. Whether you move away from a light source or towards a light source, the speed of light in a given medium is constant for every and all observers.

>>1488801

Yep, you should have some shield or something. Otherwise traveling at that speed would be a radiant experience.

>>1488816
So why do the blips catch up with you later?

>>1488824
Because at any given moment you're moving away from them, while Alpha Centauri is, in the thought experiment we're discussing, immobile relative to Earth.

>>1488824

They don't catch up. If you go to zero speed relative to earth, they come in every five minutes as on earth or Apha Centauri now. But you keep the distance, so they come in later. You have to go back to earth for them to catch up.

>>1488809

By heavier i meant mass increase.
By slower I meant time dilation.
By shorter I meant length contraction.

Still confused.
Change the observer = change the universe???