/sci/ - Science & Math

>>9314820
>You are inside a box in a universe with nothing in it.
>You are inside a box
Two objects...
>in a universe with nothing in it.
So, we're not inside a box inside a universe?
Nice oxymoron, regular-moron.

>>9314820
It has been an infinite amount of time

>>9314826
With nothing else in it. Satisfied?

Constant acceleration, or increasing?

If we're in empty space, and the box is either of the two above, it means we're gonna be pushed by a force to the back of the box, against the wall, as the inertial frame is accelerating.

Increasing or decreasing acceleration means the force acting on us changes. Therefore sooner or later it will crush us, or make us break through the box, leaving us in space.

>>9314855
How to avoid answering a question 101

>>9314820
the man in the box wouldn’t know, since time will stop for him.

He could calculate when it will happen or when it happened tho.

>>9314852
Yeah. :)

you can't reach light speed though

>>9314820
it would take an infinite amount of energy to reach c, no meaningful answer can be given

>>9314927
Question is about when you would know you're approaching c

>>9314932
>How do you know the precise time at which the box reached light speed?
not worded like that at all, but if it is constant force you wouldn't notice as you asymptotically approached c from the perspective of "stationary" observer (just one in the reference frame you started in)

>>9314820
>it reaches light speed
into the trash it goes

You start noticing the protons around you decaying.
Assuming they even decay in the first place

If you accelerated at any rate for any length of time, you still wouldn't reach light speed, and you'd never notice anything unusual. Except that you might get really hungry.

In Newtonian mechanics, since we have constant acceleration, a = dv/dt = Δv/Δt. So Δt = c/a, where c is the speed of light.

In real life (special relativity), it would never reach light speed.

>>9315033
For you, yes, you haven't even moved.
An outside observer would notice some fucky shit as you got faster and faster from their reference frame, but as we've established, there is no outside observer

Since the box is accelerating you need general relativity to describe what it would be like. I don't think you'd be able to tell without something outside the box to look at but gen rel is beyond me.

acceleration is a vector, OP.

if there truly is nothing outside the box then there can be no direction, and if there is no direction you cannot have velocity or acceleration

>>9314820
>>9314927
>>9314932
>>9314941
You retards it's not moving if there's nothing in the universe but you and the box, it's speed will always be 0, The constant acceleration will be akin to gravity

>>9315219
There can be acceleration relative to the inside observer, but since the observer would be moved with the box there is no velocity

>>9314820
Kill yourself

>>9315219
What am I reading

>>9315222
>f there's nothing in the universe but you and the box, it's speed will always be 0

speed is always object A in relation to object B.

so it's relative... and all time fuckery is also relative... right?

The box would elongate toward the direction of travel indefinitely as you reach the speed of light. You would know you have reached it when the box appears to stretch for infinity. Time for you would stop once you hit the speed of light, so when the box stops elongating is another way to tell when you've reached it.

>>9314820
The speed limit is not defined for space outside of the universe. The acceleration could have happened without time, it's possible because it's outside of the ordered field.

>>9314841
But isn't the box an exclusion where infinity couldn't have been defined?

>>9314852
That's something entirely different. We could take x as an element of space and z as an element of time. Then we would take a as a variable and formulate it as (x/z)^a. The acceleration is described as the derivation function.

>>9315222
That would be the case if we were talking about particles

>>9314820
From a photons perspective at the moment of its creation it has already reached it final destination no matter the finite distance it has traveled. This is because photons do not experience time, if you were to map the universe for a photon you will just end up with a dot on a vertical line.

So to answer your question, you wouldn't know because the big rip would of already have happened, destroying you along with everything else.

There's no such thing as speed of light. Light doesn't travel, that is an incorrect assumption.

>>9315222
Someone throw me a bone here. I can understand how reference frames define motion within a mathematical model, for instance, on paper. But if we're being technical: On some level, empty space is like a foamy noisy medium yes? On that scale, at any instant, can't an observer's position still be defined relative to arbitrary points in this medium? With this in mind, can we answer OP's question?

>>9316083
bump

It depends on whether Ernst Mach was right.
He thought that inertia was an inductive effect from the gravitation of distant objects. In a totally empty universe there'd be no inertia and no way to tell you were accelerating.

Modern physicists _mostly_ disagree, feeling that "space" would still have a structure at the quantum level even if there were no substantial masses within it.

No one really knows, since the universe _does_ contain matter and the experiment is difficult to perform.

>>9315033
yes you would notice, it would feel like gravity

>>9315033
But what if another object moved in an opposite direction at near lights speed.
To the second object the first object would have a relative speed way faster than the speed of light.

>>9316625
Nah, it would just look a bit closer to the speed of light

>>9316625
Velocities don't add as they do in Newtonian mechanics. If two objects are coming straight at each other with velocities V1 and V2 (as seen by an "at rest" observer), then each object sees the other approaching at
Vsum = (V1+v2)/(1+V1*V2)
For example, if V1 and V2 are both 0.9 c, then Vsum = 0.9944 c.
If V1 is 0.95 c and the second object is a photon traveling 1.0 c, then Vsum = 1.0 c The photon _still_ closes on you at lightspeed.
Note that if the photon is going in the same direction as your ship, it passes you at Vsum = 1.0 c.
That just shows that all observers measure the speed of light to be the same.

If the objects are not moving parallel, the formulas are a little more complicated.
https://en.wikipedia.org/wiki/Velocity-addition_formula
but the end result is the same. Velocities can never add to greater than c.

>feel constant acceleration
>be aware of the magnitude of a
>know that v = a*t
>measure how long youve been feeling a
>thats how fast you are going
>wait until t is enough for you to be at c
>apparently you cant go faster so stop feeling the acceleration anyway.

>>9317031
Wrong.
1 gee for 1 year takes you to lightspeed -- by Newtonian physics.
Get into an anti-matter rocket with a ridiculous mass-ratio and accelerate for TWO years at one gee.
You're still moving slower than light.
You never reach cee no matter how long you boost because your clock slows down and your acceleration decreases.
But you, in the rocket, never feel the change in acceleration. You can't. Whole basis of Relativity.
Read >>9317012 and please learn a little physics before posting again.

>>9314820
You don't know the precise "time" brainlet
Time is relative and if you're going light speed you'd pretty much be frozen in time if you're measuring it in earth time. Even if there was a way to measure from inside the box its still a retarded question. Is the time being measured by the person in the box or by another observer? I assume not another observer since you and the box are all which exist in the universe. Therefore my original point stands. Your question is shit

>>9317119
sounds like a bunch of hokem nigga, we aint outside the rocket. physics is just normal to the driver and so using these simple formulations is fine. we arent even adding velocity or comparing two bodies. its the only rational way to think about it.

i would say that a perfectly acceptable end point is reached when the accelleration is non effectual to the change in velocity and instead radiates energy as spacetime turbulence.

>>9314820
You would experience a force like gravity on the side of the box opposite the direction of acceleration. When the box reached light speed you would become “weightless” meaning you would no longer experience a force pushing you against any side of the box.

>>9318235
Forgot to add, this is assuming that you cant accelerate past the speed of light.

>>9314820
It will never reach the speed of light.
You need infinite power and times to do that.

>>9317439
Your overly hostile, smug reply is contributing to the state of this boards continued decline. Your reply is shit.

>>9318235
Assuming infinite energy from fairy land or whatever this sounds the most reasonable from my physics ii level of understanding.

>>9314820
Time dilation means that, from your point of view, time no longer passes when you're moving at light speed. Therefore, from your perspective the box will never reach light speed.

>>9314885
>I don't know how time works: the post

>>9314820
Well, in our universe it wont ever, even if it has a constant acceleration with no stop, it would take an infinite time for it to reach light-speed.

I guess that's not an interesting answer.

If it could be reached. (bypassing the second law of thermodynamics) Then you could still never know, because at the moment you reach Light speed, all the particles in your body would be timeless like light, which stops interaction between them and therefore stopping time for you entirely. For a neuron in your brain to fire, its individual particles that make it up could not be going at light-speed at the direction you're traveling, and move within the neuron at the same time.

>>9314820
If you want to prove that you can never reach light, speed it easy.

As long as you accept that speed is relative.

See pic.

Space ship A and B is traveling at 0.95 C RELATIVE to earth.

Since we accept that all speed is relative, then spaceship B can now say:

Hey, I'm not traveling at any speed. I'm standing still. So I'm going to accelerate again away from spaceship A up to .95C RELATIVE to spaceship A

And he can do it again after that, because speed is relative and you can always consider your reference frame as not moving.

It seems counter intuitive that his speed relative to Earth wont be 0.95 * 2 before you get into special relativity, but the reason it can work is because time changes too.

you measure the force on yourself
if you have the force, you also have the acceleration
if you know the acceleration you can calculate how long it will take to reach light speed
easy

>>9318398
Troll physics?

How am I alive? What forces are keeping my body together? Am even made out of atoms? There are far more concerning things with your scenario than trying to figure out the acceleration of the universe that I am in.

>>9318402
you think you so smart? tell me what's wrong with this logic then

>>9318412
Velocity is relative
see:
>>9318390

>>9318390
so your argument is basically:
>you can't go faster than light speed, because if ship B accelerated to 0.95C relatively to ship A you would go faster than light
nice fucking logic

>>9318432
So we ignore special relativity now?

>>9318439
no retard, but your explanation is pointless, you could just say:
>you can't go faster than light because relativity
and the explanation would be the same

>>9314820
The box can never reach light speed. Massive objects cannot uniformly accelerate indefinitely. The premise of your hypothetical is impossible, so there's no way to answer it without breaking the laws of physics from the start.

>>9318302
Yea, i was assuming everything OP was assuming was possible. He said the box accelerated to the speed of light, so i took that at face value and answered the question instead of saying “muh infinite energy” like every other response ITT.

>>9318398
This.
You know how tall you are so you know the length of the box.

You can calculate how long it takes to get moved to the back of the box from jumping.

Then you know the acceleration. You can calculate how long it would take to get to near light speed. You wouldn't know where you are in the cycle tho.

>>9318515
But if you're not moving in regards to something, are you moving? Does acceleration have any meaning in such a scenario?

>>9318515
but if you jump you're gonna rotate the box

If the box is traveling in a circle path it will have a constant acceleration but its velocity going around in a circle will never change. So it would never reach the speed of light.

>>9318002
"Rational" is what you're used to. And that's low-speed motion.
Things are different when bodies move relative to each other at near-light speeds.
Notice I don't say "as you approach the speed of light", because you never approach the speed of light. It zips past you at the same rate regardless of what you do.
No experiment has _ever_ disagreed (so far) with General Relativity.
Believe what you want to believe. Don't expect the universe to agree with you. Don't expect to pass Physics 1A either.

You never feel any change in acceleration. and it isn't because you've "reached lightspeed". 'Radiating energy as spacetime turbulence' as you got close is technobabble. That'd let you know you were "getting close" and the whole point of Relativity is that speed can be measured _only_ relative to other objects. NO sensation of acceleration or experiment (short of looking out the window) can reveal your speed.

Relativity WORKS! GPS would accumulate several miles of error per day if it wasn't taken into account.

>>9318518
No one knows for sure.
See >>9316231 or look up Mach's Principle.

>>9318534
If it accelerates, how does the angular speed never changes?

>>9318518
>>9318531
You're moving relative to the box, and the box is moving relative to you so yes.

The box won't rotate. For sake of argument, the box could be accelerating under you instead of through you. So it would be like an elevator instead of a car.

>>9318540
Your assuming the box has some acceleration in the direction it is spinning i.e. the box is spinning faster as time goes on. But that does not give a constant acceleration according to the centrifugal acceleration [eqn] a = v^2 / r [/eqn] of course you would need to find the velocity instead of the angular speed

>>9314820
Your premise is terrible, ask an actual question.

>>9315445
And for all the same reasons i cant give an answer. I don't know the parameters of "nothing" in true nothing, if it could exist, 1+1 could be 3 and the rules of cuasality might not apply. How do I answer a question with that sort of premise.