Can an object like spaceship reach speed of light? In space with

>>8016744
You can raise your speed forever, but not linearly. See Relativity for more.

>>8016744
You would need infinite energy to accelerate an object with non-zero rest mass to [math]c[/math].

(Expectedly enough, other weird things would happen too even if you assumed you could do it with a finite amount of energy.)

In the future smart fuckers will find ways to cheat the laws of nature so we can travel to planets full of sexy slave alien grils

>>8016744
>Can an object like spaceship reach speed of light?

No.

>In space with constant thrust you can raise your speed forever,

Well not exactly. Velocity is relative. Relative to yourself, your speed is always zero. That probably sounds either very obvious or very stupid, but it's true and it's a very important concept. There is no such thing as "going 100 mph" unless you also specify what you are going 100 mph relative to.

The other important concept is that relative to yourself, the speed of light is always the same. No matter how "fast" you think you are going, when you turn on the headlights, the beams go away from you at the speed of light (which we call "c"). Someone watching you go by from a planet, moving at 0.9c RELATIVE to them, will also see the beams going at c (NOT 1.9c, by the way). This sounds self-contradictory, but it isn't. And the set of concepts that explain why it isn't is called Special Relativity.

The end result:
From your perspective: you will be accelerating forever, but seemingly never get any closer to the speed of light.
From the perspective of someone watching you: you will be accelerating less and less as time goes on, getting ever closer to the speed of light but never reaching it.

but why can't you reach speed of light?

>>8016744
E=mc^2

No.

>>8016788
>infinite energy
That's such a cop out. Infinite isn't a number. There's no such thing as "infinite" energy.

There's no such thing as a cosmic speed limit

>>8016855
That's why reaching [math]c[/math] while being material isn't a thing.

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>>8016851
>Thread about objects moving

>Posts the formula for rest energy

>>8016744
>why can't you reach speed of light?
Because eventually the particle propelling the ship forward are no longer colliding with the shape ship.

You'd need a light-speed propellant.

>>8016788
explain the "infinite" thing. The speed of light isn't infinite so why would the energy be?

>>8016878
It all basically comes from the (experimentally supported) idea that the speed of light is always the same in every reference frame. It's not exactly intuitive but re-deriving expressions for energy and such like leave you with these results.

>>8016878
Have you seen a function with a horizontal asymptote? You can increase the argument indefinitely, but the function value will never quite match, let alone exceed the asymptotic value. Why this is so is due to the laws of physics that reign our Universe (specifically Special Relativity, as >>8016847 already pointed out).

>>8016870
Non-zero rest mass implies its impossible to go the speed of light.

>>8016889
Correct

How did you get that from the rest energy equation though?

>>8016883
>>8016847
I know you guys are gonna get mad about this but that seems logically unsound to me. If our ship is going 0.9c, and we turn on the lights, it follows that the light would accelerate away from us at 0.1c/s. What am I missing?

>>8016894
m=o
E=pc

>>8016902
Congrats, that's from the total energy equation which you haven't mentioned until now. Why didn't you post that in the first place instead of just posting the meme equation with insufficient info?

>>8016904
>insufficient info
>can't extrapolate from simple implications

>>8016917
I think you have very high estimations if you think that someone with no exposure to relativity other than the rest energy equation should be able to derive the total energy.

Also you still haven't explained exactly why >>8016902 means that only objects with no mass can travel at c. This whole time you've just been posting equations that don't immediately answer the question at hand.

>>8016897
>If our ship is going 0.9c, and we turn on the lights, it follows that the light would accelerate away from us at 0.1c/s. What am I missing?
Time dilation. Length contraction. All that fancy relativity jazz.

Special relativity works even if you assume that one inertial frame is true stationary, for instance, the one that's stationary with respect to the cosmic background radiation (so it's not redder on one side than the other due to redshift/blueshift/oneshift/twoshift). You just can't detect true stationary in an isolated, boundless environment ("no preferred frame of reference") using light and stuff.

I find it helps people grasp the basics if you explain SR in terms of an assumed true stationary.

Think of time dilation this way: an object can move through space and evolve internally. Like, a space ship is moving from point to point, and also the people on it are moving around, the clocks are running, etc. Obviously, moving through space has a rate: speed. But internal evolution also has a rate: time dilation.

The rate of internal evolution is at its maximum in a stationary object: clocks run at full speed. It slows down as you move faster.

If you're going at 0.9c, and you turn on the light, it travels at 1c relative to stationary, 0.1c relative to the ship, but the people on the ship are slowed down so they perceive the 0.1c as 1c.

>>8016927
Are you memeing me or are you just that dense?

>>8016878
Because spacetime is Minkowski, not Reimannian.

This means, when considering distance between two events in space-time, the distance ("interval") formula isn't [math][math] d^2 = t^2 + x^2 + y^2 + z^2[/math] like you might expect, but [math] d^2 = t^2 - ( x^2 + y^2 + z^2 ) [/math] instead. Note the minus sign, it's important.

For an observer moving at a constant velocity between two events, the interval is equal to the time that passes for them between those events. (Since in their stationary reference frame, they're only moving in time, not space, so their path along that line aligns with their time axis.)

For brevity's sake, we'll shorten the space component of the distance to just x. Starting from 0, as the velocity x/t gets bigger, the overall interval becomes smaller, and eventually when x / t = 1, the interval is 0 - no time passes for an observer travelling along this line. Obviously, if you're frozen in time, you can't accelerate any further.

For the same reason, you need infinite energy to reach c. Say you wanted to accelerate at a constant rate relative to a stationary observer. As you go faster and faster, time begins to slow down for you, so you have to exert more and more power relative to your clock to maintain the same acceleration from that stationary POV. The needed power increases so rapidly that the total energy needed to reach the speed of light adds up to infinity.

>>8016868
Why would it require "infinite" energy?

>>8016935
How can something add up to infinity?

continued from >>8016928
The actual relationship is that the squares of the speed as a fraction of the speed of light and the rate of internal evolution as a fraction of what the rate would be for a stationary object add up to 1.
S^2 + R^2 = 1
So: R= square root(1 - S^2)

If you time a pulse of light from the back of the ship to the front and to the back, it will travel slower forward, and faster backward, and your clock will be slower than a stationary one, and these always work out so the time it takes to travel is consistent with the pulse travelling at 1c.

Keep in mind: if you synchronize two clocks at the back of the ship, and you carry one forward, it will be slowed down additionally due to its higher speed while it's being moved forward.

Any way you try to measure the speed of light in the ship, without knowing that it's moving, you will come out to 1c.

>>8016928
>>8016935
interesting

>>8016932
No, I just don't think your explanations are adequate for people who don't already have a grasp of relativity, making them kind of useless.

Your first post was just the equation for rest energy with zero context. Using only that equation you can't get anything meaningful about motion because it contains no information about motion.

Then you just posted the energy for a massless object, without defining what momentum would even mean in this case. You're considering motion this time but you didn't post anything explaining why this implied that only a massless object could travel at light speed.

All you've done is post tangentially relevant equations with no further explanation in a thread made by someone who has clearly never studied relativity. It's like posting the schrodinger equation without explaining what a wavefunction is. Congrats, you know the equations but you're really just dickwaving at this point rather than providing useful information.

>>8016897
It's not intuitive and it is hard to grasp at first but it's how it works.

One of the things that tipped people off to it working this way was the definition of the speed of light from the electromagnetic wave equation. Maxwell found that light could be explained as a wave of periodic disturbances in electric and magnetic fields, from this he found an expression for the velocity of this wave which was [math]v=\frac{1}{\sqrt{\epsilon_0\mu_0}}[/math], where [math]\epsilon_0[/math] and [math]\mu_0[/math] are the permittivity and permeability of free space.

This was big news because it meant that the speed of light was solely defined by these fundamental constants. The thing is, these constants don't change when you're moving, that makes no sense, it would mean that your magnets would behave differently when you started walking away from them. This was the basis for Einstein's proposition that the speed of light was the same in all reference frames, because these constants were.

If this was true it meant that general equations of motion had to be overhauled. To ensure that the speed of light remained constant in all frames several weird things had to be the case, such as lengths appearing to shrink and time slowing down as you increase in speed. Another requirement was that massless objects be unable to reach the speed of light with a finite amount of energy. I can't go fully into the maths here but hopefully the context that led to this is interesting to you.

>>8016938
>Why would it require "infinite" energy?

General relativity gives you two choices: >Progression of time
>Progression of velocity

As your velocity increases, time is compressed. This is a consequence of the nature of space and time itself. Increasing velocity means you need more energy for each bit of velocity gained, and compress time further and further. There is an asymptote at the speed of light that cannot be reached.

>>8016947
Consider:
I give you a penny.
Half an hour later, I give you a penny.
A quarter of an hour later, I give you a penny.
An eighth of an hour later, I give you a penny.

The interval continues to halve in the same pattern. Assuming no other complicating factors like not being able to move fast enough or running out of pennies arise, how much money will you have after two hours?

>>8016947
It's less that it adds up to infinity more that any finite amount of energy would not be enough to propel you to light speed, no matter how large a number you plug into the formula you would get a result less than c.

>>8016744
Time keeps slowing down as you reach closer to light speed. So you'll never pass it because the game won't let you

>>8016897
Because space and time are not separate.

Draw a chart on some paper, with one axis labeled "space" and one labeled "time". (No units.)

Now, obviously an object moving at a constant velocity would be represented on this graph as a straight line at some angle, because it has a constant ratio of x/t. So draw a sloped line on your graph passing through the origin, to represent a moving object, say 30° from vertical.

Pick a point (x1, t1) on that line. So, from the point of view of the guy drawing the chart, t1 seconds pass between the object passing the origin and the selected point.

But velocity is relative; everything has to work if we assume that the moving object is actually stationary and look at things from its point of view. So turn your paper and draw a new space and time axis, perpendicular and parallel to the moving object. Measure the time t'1 between the origin and the point on this axis, and you'll get a different number. And the distance along the new space axis to the previous stationary observer along the previous time axis will be different too.

(But, no matter what angle you draw your axes at, or where you put the origin, all observers will agree on the total length of that line - they'll just disagree about the values of the space and time components)

Space and time being one thing, plus velocity being relative, means time and space must bend for different observers.

Now, the real world isn't quite like that chart - it's got a very crucial difference. Instead of distance along a line using the ordinary Pythagorean formula of distance^2 = time^2 + space^2, we live in Minkowski spacetime, where d^2 = t^2 - x^2. So instead of a space-time vector being longer than its components, it gets shorter, and eventually becomes 0 when x = t. This means that x/t = 1 is a "magic" velocity - since overall spacetime length is absolute, and the only way to have the length along a moving object's worldline be 0 is if it's moving at x/t = 1...

>>8017051
...then an object moving at x/t = 1 relative to one reference frame is moving at x/t = 1 for *all* reference frames. No matter how fast you're going, something going at 1 is still going at 1 relative to you, as your space and time axes skew to render what an outside observer sees as increasingly small differences in velocity into a constant impassable gap. From a different point of view, you seem to be struggling just as much to go from 0.9 to 0.99 as going from 0.99 to 0.999* You can never catch up.

Of course, since our unfortunate inability to align a meterstick with the time axis means we've awkwardly chosen to use different units for both axes, we do need a conversion factor between meters and seconds to tell us how much 1 meter of time actually is, so we know how what x/t=1 means when converted to meters per second, instead of meters per meter. As it turns out, this conversion factor 'c' is around 300,000,000 m/s.

Why it is that light travels at c is a bit more complicated, and I have yet to come up with a good way to derive it that is layman-friendly and doesn't rely on skipping difficult math.

*Not actually correct numbers

OP.
From Einstein, you know that as one approaches C the mass increases. In reality this does not matter much assuming one has good propulsion. The problem is that as the mass of the atomic elements increases so does their fields and the distance between them. Your ship gets bigger. Theoretically infinitely bigger. You could end up 'gigantified' and flying a ship as big as our solar system.
"Sub-light rokz"

>>8017499
but the amount of atoms does not increase? so you'd just explode?

>>8017499
This is a troll answer

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in theory if you induce liquid mercury in a vacuum, which is also not magnetic. with the proper housing to allow the fluid to act as a propellent because in space you aren't really fighting anything so if you can get yourself to move in a direction and create a source of nature like wind then in theory you should be able to reach something close to tralvralleing the light year in theory if your ship could hold up to that maybe an asteroid modded ship might be your best bet nothing man made come close to the strength needed to travel at such speed but hey just a theory

>>8016994
$[math](\frac{1}{50} \cdot \aleph_0)[/math]

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>>8016744
Why can't a spaceship reach the speed of light?

=

Why can't a spaceship reach the speed of a photon?

=

Why can't an obese amerifat reach the speed of Usain Bolt?

??

>>8016744
because speed of light is a constant, whatever speed you may go, light will always have the same speed.

>>8017962
to make it clearer,
Like even if you were to reach a speed of 3x10^8m/s
Light would still travel at the speed of 3x10^8m/s so you can never reach the same speed as light, since light is a constant. What will happen is, time dilation.
Since time is relative, it wont change anything either. However, like the 5 minute you spent travelling at light speed, would be let's say 2 days for a person living on earth.
Those were just illustration, because according to the time formula, if you reach the speed of light, end up dividing by zero which would give you a local time reaching infinity (you would basically be a photon, because the future, present and past would be the same for you)

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Is faster-than-light travel just a science fiction meme? Or are wormholes and shit like that actually plausible as ways to get around the c barrier?

>>8018434
Wormholes are science fiction. Presumably warping space time would physically allow for FTL, but this is also a mega-hyped up notion that disregards the fact that we most likely can't build a ship that would be able to survive such a process.

So, short answer is no. Long answer is its theoretically conceivable, but no where near realistic unless some fat brain comes alone and fucks up all of our physics.

>>8016902
Hi I'm retarded what is m?
What is o? what is E? what is p? what is c?

>>8016847
>>8016782
>>8016788
>>8016887
>>8016935
>>8016928
>>8017051
>>8017093
>>8018445
>all these General Relativity experts
>in the "would a drone fly on mars?" thread nobody could understand newton's second law
>in the "which shape cup containing water at the same height has more pressure?" thread nobody could apply pascal's principle
>yet in this thread everyone is suddenly able to teach the works of minkowski
i don't get this board.

>>8017093
>>8016953
I'm a little confused about the effect of velocity on perceived time. What reference frame determines when you're approaching c? What if the galaxy is actually moving at 0.99c relative to whatever's bigger than galaxies and your propulsion is actually just decelerating you relative to the galaxy?

>>8018434
there's a theory that black holes make a deep enough dip in spacetime that they can intersect with another point, so yeah in short it's a scifi meme

>>8018493
most of us have high IQs and low study habits

>>8018493
That's special relativity, not general relativity.

The basics of special relativity, as far as time dilation and Lorentz contraction and the invariant speed of light go, can be understood reasonably well by anyone reasonably clever with a solid grasp of at least high school algebra.

(Understanding relativistic physics, in terms of notions of energy and momentum, is somewhat more difficult but can be explained at an introductory level to anyone with a solid grasp of high school physics and at least high school calculus.)

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>>8018509
People actually believe that they're smart but lazy?
>>8018688
No friend, if you think you can understand relativity with just high school algebra you are firmly on mount stupid.

Furthermore my original point was that how can you "know" Lorentz contraction but be unable to approximate the power consumption of a propeller?

>>8018704
One of those requires actually knowing something practical and useful, and so can obviously be ignored.

The second, however, is something that popsci tells you is deep and impressive, and so knowing it obviously makes you more powerful. It's the IFLS principle at work.

Also, what I actually said is that you can understand the very basics of special relativity (time dilation, Lorentz contraction, the invariance of c) with high school algebra. This is because those can be re-derived pretty clearly in the simplifying assumption of one space dimension, with a few arguments from analogy and intuition to quickly wallpaper over a few necessary assumptions so that they sound plausible without having to rigorously show why they must be the case. (Which cannot be done with high school algebra.)

>>8018704
>Anon posts mount stupid and laughs at all the plebs ascending it.
>Doesn't realize his arrogance is consistent with being at the apex of mount stupid.

>>8018739
So you are saying /sci/ only reads about science that makes them sound impressive?
>>8018740
I have not opined on OP's topic.

>>8018704
that picture is awesome, but I'd say it's not an unrealistic belief, of course stupid people pass off their failures on other factors, but not all smart people are academically inclined

>>8018756
>I have not opined on OP's topic.
No, you came to a thread where on-topic discussion was happening and started posting off-topic from an unrelated Mt. Stupid.

>>8018756
>So you are saying /sci/ only reads about science that makes them sound impressive?

By post count, yes. People who are actually experience and knowledgeable in a field are generally speaking too busy to shitpost constantly, so almost every post here is the armchair popsci type, or their closely related cousin the fucking-hate-armchair-popsci-types type. These naturally gravitate to the subjects that seem most interesting and important, (and hence impressive), so surface-veneer-level fundamental physics, "cool" technological developments (speculative or otherwise), folk social science, and the intersection of philosophy and neuroscience/biology.

OP here, thanks for answers everyone.

Here is another question, If theory of relativity suggests that at higher speeds time moves slower, does it affect organic material?

For example if I travel from earth to somewhere in space with speed half of lights speed for 20 earth years, will after I return, will I be younger than human on earth? And if I will, does that mean that Human in space accelerating at constant speed will live longer than human on earth?

>>8018851
the one in space will experience less than 20 years while earth experiences 20 years, so if someone lived and died on a spaceship with constant acceleration he would live longer from the perspective of time on earth, but it would feel like a regular human lifetime for that person

>>8018843
>folk social science
Excellent oxymoron you have there.

>>8018851
>If theory of relativity suggests that at higher speeds time moves slower, does it affect organic material?

The fact that you'd even ask this question suggests that you, at a very deep level, don't understand what the fuck you're talking about. It's not a trick of perception or some weird magic that only affects clock-shaped objects.

Anyway
>will I be younger than human on earth?
Yes.

(Although there's actually some interesting subtleties here; it hinges on the fact that you have to change directions in order to come back to Earth. If you just kept moving away, you'd observe Earth's clocks ticking in slow-mo, but Earth would observe your clocks ticking in slow-mo. See https://en.wikipedia.org/wiki/Twin_paradox for this specific problem.)

>does that mean that Human in space accelerating at constant speed will live longer than human on earth?

No. The human on Earth will just die sooner.

>>8018885
>No. The human on Earth will just die sooner.

And again, that's only if the human actually returns to Earth - if he just kept moving away, he'd see the one on Earth age slower, while the one on Earth would see the one on the spaceship age slower.

[Very rough and inaccurate analogy:]
Think of two metersticks, lying at an angle to each other. If you lie along one meterstick, the other will appear shorter than 1 meter due to perspective foreshortening, while if you lie along the other meterstick the first will appear shorter instead.

https://youtu.be/NnMIhxWRGNw

2 minute video explaining why something like a spaceship cant go the speed of light.

This is the simplest explaination ive ever seen or heard.

>>8016994
I believe it was Zeno the philos/math that developed the concept of diminishing returns.i.e. To go from point A to Point B...you have to travel 1/2 the distance, then you have to travel 1/2 the remaining disntance, then 1/2 of the remaining...and so forth ad nauseum.

>>8018931
Its called Zeno's paradox

>>8016871
Terrible post tripfag

>>8017944
Legitimately lol'd at this post

This man is drunk/high

>>8017944
>in space you aren't really fighting anything so if you can get yourself to move in a direction and create a source of nature like wind then in theory you should be able to reach something close to tralvralleing the light year
This

>>8018972
I don't see how it's terrible. Eventually the velocity of the ship exceeds the rate at which particles of fuel bounce off of the rockets. Their momentum is made irrelevant by the sub-light velocity. It's not a relativistic theoretical answer, but chances are OP doesn't understand non-chemical propulsion either way.

>>8018493
Classical mechanics is hard.

What is it with /sci/ and denying the existence of the universal stationary reference frame?

>>8019118
Show it, if you're so great

>>8019124
It's pretty obvious. How could velocity exist without an objective stationary reference frame?

>>8019131
When things move relative to each other. One thing moves right, one thing moves left, boom there has to be some velocity involved, e.g. the rate of change of the distance between the two objects.

Don't need no universal frame for that.

>>8019131
>without an objective stationary reference frame
Relatively.