Down the relativistic rabbit-hole (Split from official news)


Eight Bit

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Note: These posts originated around page ten of An Update of the Waiting Game - some context may have been left behind during the split. - Binky

But perception of time is relative isn't it? Also someone ages faster when moving faster iirc. Or was it the other way around?:cool:
 
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levi

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But perception of time is relative isn't it? Also someone ages faster when moving faster iirc. Or was it the other way around?:cool:
It's the other way round. Actually, I don't think it can be related to the speed at which you travel, since you taking a spaceship from earth to mars is entirely analagous with your spaceship staying still and the earths propelling itself away from you and mars zooming towards you. I think the trick is acceleration (and deceleration which is just negative acceleration) - the faster you accelerate the slower local time passes for you.
 

Grench

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It's the other way round. Actually, I don't think it can be related to the speed at which you travel, since you taking a spaceship from earth to mars is entirely analagous with your spaceship staying still and the earths propelling itself away from you and mars zooming towards you. I think the trick is acceleration (and deceleration which is just negative acceleration) - the faster you accelerate the slower local time passes for you.
I suspect your answer may have missed relativity.

Consider it this wrong answer that gets the concept closer: There is a maximum velocity (c=light). The faster you go, the closer you get to c. If two time synchronized clocks start with the same absolute velocity then one is propelled to a faster velocity and subsequently slowed, the clock that was moving closer to c for a period will be somewhat behind.

An astronaut in a can, accelerated to 99.9999999% of c (leave off energy requirements/etc.), would still perceive things as 'normal'. From the perception of those he's flying past, the astronaut would appear dead.
 
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levi

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I think that blurb about a spaceship flying to mars is largely equivalent to the planets spontaneously doing a step to the left around the space ship is the core of relativity.

In as much as I understand it, it's because e is constant that causes time to dilate. If you're travelling in some sense at 99% of e, you'll see light still moving at e. Because at normal time you'd see light travelling only 1% faster than you, time slows down by a factor of 100 to bring that 1% back up to 100%. But that would suggest it's speed, not acceleration that causes it, and how you square that with a dynamic universe without any fixed reference to measure against, I'm at a bit of a loss.
 

Grench

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I am not a physicist. So, someone with a better understanding please correct me when I mess this up.

I think that blurb about a spaceship flying to mars is largely equivalent to the planets spontaneously doing a step to the left around the space ship is the core of relativity.
That is points of perception in a Newtonian model, not relativity. Within a Newtonian model, all motion is relative to the position or velocity of the point of view, but that is not Einstein's relativity. Concepts date back to Galileo. Nothing is 'fixed', everything is in motion relative to any other thing. There is no 'Jail' on the cosmic Monopoly game board. Simultaneously, though, proclaiming oneself as a 'static point' can make the math a lot easier.

In as much as I understand it, it's because e is constant that causes time to dilate. If you're travelling in some sense at 99% of e, you'll see light still moving at e. Because at normal time you'd see light travelling only 1% faster than you, time slows down by a factor of 100 to bring that 1% back up to 100%. But that would suggest it's speed, not acceleration that causes it, and how you square that with a dynamic universe without any fixed reference to measure against, I'm at a bit of a loss.
That is a lot closer to 'special relativity'.
Code:
https://www.space.com/17661-theory-general-relativity.html
https://en.wikipedia.org/wiki/Principle_of_relativity
https://en.wikipedia.org/wiki/Special_relativity
Special principle of relativity: If a system of coordinates K is chosen so that, in relation to it, physical laws hold good in their simplest form, the same laws hold good in relation to any other system of coordinates K' moving in uniform translation relatively to K.
— Albert Einstein: The Foundation of the General Theory of Relativity, Part A, §1
  1. The laws of physics are invariant (i.e., identical) in all inertial systems (i.e., non-accelerating frames of reference).
  2. The speed of light in a vacuum is the same for all observers, regardless of the motion of the light source.
The bit that always fascinated me has more to do with the equivalence of mass and energy - and what happens when a theoretical object approaches the speed of light. The old E=mc^2 thing. The Wikipedia article on Special Relativity cited above explains this well: "As an object's speed approaches the speed of light from an observer's point of view, its relativistic mass increases thereby making it more and more difficult to accelerate it from within the observer's frame of reference." Conclusion: Interstellar star ships are really difficult to steer as their relative mass becomes infinite - as well as the energy needed to change direction...
 

ible

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i'm a physicist. (or at least trained as one.) no general relativity is necessary to understand the "twin paradox," but you do need to apply your special relativity carefully.

time appears to move slowly for objects that are moving at high speeds. a spaceperson zooming past the earth would see that clocks on earth are moving slowly. an astronomer observing the spaceperson would see the clocks in the spaceship moving slowly.

suppose the spaceperson is moving an appreciable fraction of the speed of light. the person does a round trip from earth to alpha centauri and back. they will be younger than their corresponding twin on earth.

the reference point is confusing (since you can swap two points and say the astronaut will see slower clocks on earth). but if you do the math carefully with acceleration, you see that the astronaut is the one who ages less.

in the end, a person traveling very nearly the speed of light would experience almost no time at all, and can get to any destination, no matter how remote. since people have mass, true timelessness is impossible, but photons can do that; they don't feel the passage of time. they are born and die in an instant according to their internal clock.
 

Grench

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i'm a physicist
...
the reference point is confusing.
I thought of an interesting experiment to maybe measure our absolute velocity through space.. It will need a 20 mile long space based LIGO. Fire light at either end from the center to measure how long it takes to return. The difference can translate as velocity in that direction. Change the axis orientation, repeat. Again. At that point it should be possible to draw a vector for our velocity relative to true 0 velocity. Then we should be able to point to what absolute stillness is.

What happens if you remove all energy from a system including absolute motion? Anything? Nothing? Is that when branes become findable? Are we simply moving too fast for higher orders to be found? At true zero motion, can a thing become detached from our known space?
 

spud42

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time is definitely relative..... time passes slower or faster depending on which relative is visiting you...
mother in law's can make time seem to flow backwards and have the added disadvantage of being micro black holes.
 

ible

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I thought of an interesting experiment to maybe measure our absolute velocity through space.. It will need a 20 mile long space based LIGO. Fire light at either end from the center to measure how long it takes to return. The difference can translate as velocity in that direction. Change the axis orientation, repeat. Again. At that point it should be possible to draw a vector for our velocity relative to true 0 velocity. Then we should be able to point to what absolute stillness is.
hm? you're still measuring velocity relative to the laser setup. that's not absolute velocity. that's what the "relative" in special relativity is all about...

What happens if you remove all energy from a system including absolute motion? Anything? Nothing? Is that when branes become findable? Are we simply moving too fast for higher orders to be found? At true zero motion, can a thing become detached from our known space?
if you can reword your question to not use "absolute," you'll have a better formed question.
 

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I thought of an interesting experiment to maybe measure our absolute velocity through space.. It will need a 20 mile long space based LIGO. Fire light at either end from the center to measure how long it takes to return. The difference can translate as velocity in that direction. Change the axis orientation, repeat. Again. At that point it should be possible to draw a vector for our velocity relative to true 0 velocity.
Won't work, even if we ignore the relativity of light. Any change in time it takes to reach one end or the other from the center point will be mitigated do to the return trip.
 

ible

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oh is the giant space laser the thing you're trying to measure the speed of?

in relativity, the laser apparatus is at rest with respect to itself, so light fired from the center will bounce off of the ends at exactly the same time and return to the center at exactly the same time. -- in the reference frame of the giant space laser.

in the reference frame of someone outside the laser, watching the laser go by, light fired from the center hits the back end of the laser first, then the front. on the return journey, it happens in reverse, so that the light meets in the middle again, at the same time.

things that collide (at the same space-time location) always collide in every reference frame (light meeting back in the center, or being fired in the first place), but everything else is relative, even time.
 

Binky

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You know, this sounds suspiciously similar to the Michelson-Morley experiment...
 
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There is this talk about Higgs' boson on thinkerview which is quite enlightening. It says that mass and time are intertwined. A photon has no mass, so from its point of view it is 'born' and 'dies' almost at the same time. Also earth is going in a straight line, its course is altered by a space-time distortion caused by the sun we call here gravity.
It's okay if the talk sounds like Chinese to you, well, it's because it's French actually.
I guess the pyra's Two Months™ could be altered by serious gravity
 
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