Veeky Forums, help me with special relativity

Veeky Forums, help me with special relativity.

Say we send a probe to Alpha Centauri today, 1/11/18. It travels at near the speed of light. When it arrives, it takes photos and beams them back to us, which takes 4.5 years or so.

But, the probe traveled at, let's say, 0.9999999C over the whole journey. So it experienced time dilation such that its clock appears to be running about one twentieth the speed of clocks on Earth.

Which of these is true?
A) The journey only appeared to take about 3 months from the probe's frame of reference, but 4.5 years from Earths frame of reference, or
B) The journey appeared to take 90 years from Earth's frame of reference, but only 4.5 years from the probe's frame of reference?

In other words, when do those images arrive back here on Earth? Related question, if the probe puts a timestamp on the photos, what does the timestamp say?

Time dilation is a brainlet philosophy unsupported by actual science

at a speed of 0.9999999C, it would actually run at a 2000th the speed, so it would tactualy take around 17 hours from the probe's perspective but 4.5 years from Earth's perspective.

>he doesn't know about time dilation in cosmic rays and particle accelerators

Think about what you just typed and how it doesn't make sense.

wait fuck, i might have gotten that the wrong way round... yeah, it's the other way around. the time you put into the equation is how long the journey would be from the object's frame of reference, and the number you get out is the time someone at a frame of reference technically travelling at 0.9999999C away from you would see...

so 4.5 years for the probe, 10,062 years for earth

it doesn't make much sense to begin with, I see where i fucked up though

Oh, oops. In the OP I used a dumb online calculator thing... It gave me a value of 0.45, but that's actually a percentage, so yeah, on two-thousandth, not one twentieth. Still, you're saying that the answer is B?

So we wouldn't get the pictures back here on Earth for 10000 years?

yeah, the answer is B
because from the probe's perspective nothing changes, it still has to travel at 0.9999999C for the distance it originally needed to go. Specifically, it would take 10,066.8 years, assumming 4.5 light-year distance is correct.

The equation itself, for future reference, is

[math]t = \frac{t_0}{ \sqrt{1-\frac{v^2}{c^2}}}[/math]

with [math]t_0[/math] being the time for the probe, in any measurement unit you fancy, and [math]t[/math] being the time for the observer. you can replace [math]\frac{v^2}{c^2}[/math]

fugg
you can replace that with a speed relative to the value of the speed of light, squared, like 0.99999^2, if you already know it.

So we could actually get the pictures back sooner if we sent the probe at a slower velocity.

If we sent it at 0.5C, for example, it would only take about 9 years to get there from the probe's perspective and about 10 years from ours.

That seems crazy.

Wait a sec, so the "you cant travel faster than light" is a meme?

If I have an spaceship that goes near c, I would practically teletransport around the universe

Yeah, people in the earth would just see me travelling at near c, but who gives a fuck about the gay people in gay earth?

That's what I was thinking when I wrote the OP, but the answer in this thread is "no." You'd still feel like it took 4.5 years to get there, but 10000 years would have gone by on Earth.

It'd be near 4.5 years from our perspective to arrive and then another 4.5 years to get pictures sent back at normal light speed.

Wtf is going on ITT???

Idiots. This must be a troll...

You'd get your pictures 1/11/27.
They'd be time-stamped (in the corner) with the launch date plus 17 hours 38 minutes.

Tip: instead of squaring, subtracting, and taking square root, just hit "arcsin" and then "cos". That gives you "tau" directly.
Second tip: ignore the Veeky Forums clowns trying to screw with your head.

See >but who gives a fuck about the gay people in gay earth?

Yeah, that is crazy. Brainlets f***ing with you.
Always think about the physical meaning of the equations and ask "Is this answer reasonable?"

You would never get pictures beamed back because the distance is greater than the the ability to resolve a signal. The kind of wireless communication with extrasolar satellites is on the scale of bytes per minute with shit like the voyagers being rescinded to binary bit checks once a year.

If your problem was instead the probe took pictures then travelled back to earth at the same rate it left earth questioning only what the timestamps would be, it still probably wouldn't be dilated between earth time and on-board probe time. Thinking time's effects on an object change depending on the speed of the object is senseless malarky, especially when it's inverse to sensibility. Insects may be able to move around incredibly quick and live extremely short lives, but time dilation should say they would instead live extremely long lives relative to the observation reference of much slower humans or mammals, because the effects of time on them are lessened, while much slower creatures like giant tortoises should have comparatively shorter lives as relative to the tortoise an insect would be moving at an astronomical speed. That the tortoise should live for a hundred years and the insect live for a week is in contrast to the concept of time dilation implying something moving faster than our own frame of reference would internally experience less time than we record from the outside. That Cooper should near a black hole and 20 years pass from the outside only to return as if it'd only been 8 hours would say time dilation's mechanics of cooper moving faster than the frame of reference from the orbital station should mean that houseflies, moving faster than the frame of reference from mammals, should live years relative to human's ability to date events from the outside reference, and anything to imply that dilation occurs as predicted on the fly to extend it's otherwise 2 hour long lifespan to a length of the week relative to humans is goofy shit.

Time dilation is shit

>but 10000 years would have gone by on Earth.

>target is 4.5 light years away from Earth
>probe takes off from Earth and travels at near c
>it takes 10000 years from Earth's perspective

You guys are saying that the answer is A?

That's also kind of a crazy answer. It means that I could theoretically get anywhere in the universe I wanted in a very short time (from my perspective). So the "speed limit" of C really isn't a big deal.

>It means that I could theoretically get anywhere in the universe I wanted in a very short time (from my perspective)
that's right. according to this if you could travel at exactly light speed you wouldn't feel time at all

Then speed of light limit is a stupid worry

>invent a spaceship that goes at c
>give one to every human
>now we are a timeless species roaming inmortally around the universe

you'd need infinite energy to pull some mass at the speed of c though
anyway let's imagine you could travel at c in your human body just fine - you wouldn't even be living. none of your bodily functions could even develop because they'd be moving at a speed higher than c

>none of your bodily functions could even develop because they'd be moving at a speed higher than c

True, but thats only in the travel, you will recover after stopping in a destination

the point is you're not living immortally as you put it, you're just living a lot slower than people on Earth
the same way people on Earth are living a lot slower than ayy lmaos who might live in a planet with a much slower orbit

If you can travel very close to lightspeed, you CAN go anywhere in a brief period -- as measured by the clocks in your ship. You don't care that decades or millennia are passing on Earth unless you plan on going back there at some point.
So you can explore the cosmos in your own lifetime (Which isn't extended any. You still eat the same number of meals, sleep the same number of hours.)

There are a few ENGINEERING problems, however. Insane amounts of energy are required. A fusion rocket capable of accelerating to the point where time was dilated by a factor of 1000 (and then stopping) would need a mass-ratio of 6.8e55.
Then there's the issue of not frying from the interstellar hydrogen atoms you run into and the X-rays they release as your ship shoves them out of the way.

>travel at c
>relativistic Kintecic energy approaches infinity as v approaches c
>have literally infinite mass
>have finite size
>have infinite density
>instantly collapse into black hole
>size of black hole depends on mass
>have literally infinite schwarzschild radius
>entire universe gets engulfed by an infinite black hole expanding forever at the speed of light

>also you'd need to divide by zero in a lorentz transform

Special relativity tells us that clocks in motion run slower from our perspective, but if 4.5 years pass on Earth, While 17 hours pass for me then how can it be possible for me to see the Earth and it's clocks run slower, shouldn't I see Earth really sped up so such a long time on Earth can pass in a little of my time?

OP said "near" lightspeed. Strawman argument,

Furthermore, you wouldn't collapse into a black hole at 0.9999999... cee. Consider the view from another spacecraft moving just a bit slower. He observes you traveling at "only" 0.999 cee, well short of the "velocity which leads to collapse".
Now, a collapse is a distinct event in space-time. It either happens or it doesn't happen. And if it doesn't happen for one observer, it doesn't happen for any observer.

You failed or you didn't fail your Physics final. Different observers may disagree on when and where you took the test, but your grade-number is immutable. Written in red, right at the top.

Traveling at 0.9999999C, the light showing your takeoff arrives at AlphaCent while you're still 14 seconds from landing.
What do 'scopes on AlphaCent show? First, they see your takeoff. 14 seconds later, you arrive and land. During those 14 seconds they must have seen you shoot across the intervening lightyears. 4.5 years of Earth history is on the tape too.
What did telescopes on Earth see? You land on AlphaCent and the images get back 9 years after takeoff. So they see you making the whole voyage at half the speed of light. People on AlphaCent move at "normal" rates and the Terrans watch 9 years of history unfold between your launching and landing.

I know this is bait, but time dialation doesn’t come into effect at speeds that arent a significant fraction of the speed of light. The time difference between a house fly moving at maximum speed, and a tortoise moving at 0mph would be negligible. Best case scenario the housefly can manage 0.0000000014% of the speed of light (yes that is an actual figure) which means that after a period of 2 weeks of that housefly traveling as fast as physically possible(2 weeks is the average lifespan of a house fly) you would need one of the worlds most prescise atomic clocks to measure the difference it would experience due to time dialation.
The difference in life span for different animals has more to do with their metabolic rate and body temperature than it does time dialation, by a wide margin. Note that “a wide margin” in this example is one of the most severe understatements ever posted on Veeky Forums.

>Nobody on sci knows high school physics level special relativity
From the probes perpective its speed is 0.9999c but the distance between earth and the planet would shrink with the lorentz factor
Meanwhile from earth the distance and speed stay the same but a clock on the probe would appear to run slower with the lorentz factor

Therefor A is correct

Yes, at lightspeed you are instantly at your destination. If you fly back to earth the minimum time that has passed at your arrival in their reference time is still at least 2*distance/lightspeed.