Question About Time Dilation

[spazfest]

Hi!

 

I'm an amateur writer and one of my stories runs on the premise of time dilation. I was wondering if there are any experts here who can answer my questions.

 

So we have Earth and what we will call Planet X on opposite sides of the LIC. Now, in my story, citizens of Planet X travel to Earth, but when they come back they realize they have experienced some time dilation (7 Earth years to about 25 Planet X years).

 

Assuming travel between both planets was instantaneous (magikz), what kind of explanation would I have to give to avoid making a plot hole? I know time dilation is caused by gravity differences, but can the stars these planets are going around cause noticeable effects at least to this scale?

 

Thanks so much for answering my silly question!

 

-Spaz

[pavelcherepan]

What is LIC?

[Spyman]

What is LIC?

The Local Interstellar Cloud (or Local Fluff or LIC) is the interstellar cloud roughly 30 light-years (9.2 pc) across through which the Earth's Solar System is currently moving.

Diagram of the local clouds of matter that the Solar System is moving through, with arrows indicating cloud motion.

http://en.wikipedia.org/wiki/Local_Interstellar_Cloud

 

----------

 

Hi!

 

I'm an amateur writer and one of my stories runs on the premise of time dilation. I was wondering if there are any experts here who can answer my questions.

 

So we have Earth and what we will call Planet X on opposite sides of the LIC. Now, in my story, citizens of Planet X travel to Earth, but when they come back they realize they have experienced some time dilation (7 Earth years to about 25 Planet X years).

 

Assuming travel between both planets was instantaneous (magikz), what kind of explanation would I have to give to avoid making a plot hole? I know time dilation is caused by gravity differences, but can the stars these planets are going around cause noticeable effects at least to this scale?

 

Thanks so much for answering my silly question!

 

-Spaz

I am not an expert on general relativity but from my understanding gravitational time dilation on the scale your story needs doesn't sound feasible for somewhat similar stars and planets, you need to get very close to a very massive and dense body to get large effects.

 

To illustrate then, without accounting for the effects of rotation, proximity to the Earth's gravitational well will cause a clock on the planet's surface to accumulate around 0.0219 fewer seconds over a period of one year than would a distant observer's clock. In comparison, a clock on the surface of the sun will accumulate around 66.4 fewer seconds in one year.

http://en.wikipedia.org/wiki/Gravitational_time_dilation

 

You need to either use scientific accepted travel speeds close to the speed of light to get a substantional time dilation due to realtive velocity during the travel forth and back to their home planet or simply invoke a new (magikz) time dilation that happens from the instantaneous movement or due to a strange effect from the device (magikz) they use for this kind of travel.

 

Consider a space ship traveling from Earth to the nearest star system: a distance d = 4 light years away, at a speed v = 0.8c (i.e., 80 percent of the speed of light).

 

(To make the numbers easy, the ship is assumed to attain its full speed immediately upon departureactually it would take close to a year accelerating at 1 g to get up to speed.)

 

The parties will observe the situation as follows:

 

The Earth-based mission control reasons about the journey this way: the round trip will take t = 2d/v = 10 years in Earth time (i.e. everybody on Earth will be 10 years older when the ship returns). The amount of time as measured on the ship's clocks and the aging of the travelers during their trip will be reduced by the factor , the reciprocal of the Lorentz factor. In this case ε = 0.6 and the travelers will have aged only 0.6 × 10 = 6 years when they return.

 

The ship's crew members also calculate the particulars of their trip from their perspective. They know that the distant star system and the Earth are moving relative to the ship at speed v during the trip. In their rest frame the distance between the Earth and the star system is εd = 0.6d = 2.4 light years (length contraction), for both the outward and return journeys. Each half of the journey takes 2.4/v = 3 years, and the round trip takes 2 × 3 = 6 years. Their calculations show that they will arrive home having aged 6 years. The travelers' final calculation is in complete agreement with the calculations of those on Earth, though they experience the trip quite differently from those who stay at home.

 

If twins are born on the day the ship leaves, and one goes on the journey while the other stays on Earth, they will meet again when the traveler is 6 years old and the stay-at-home twin is 10 years old. The calculation illustrates the usage of the phenomenon of length contraction and the experimentally verified phenomenon of time dilation to describe and calculate consequences and predictions of Einstein's special theory of relativity.

http://en.wikipedia.org/wiki/Twin_paradox#Specific_example Edited May 5, 2015 by Spyman

[pavelcherepan]

 

 

The Local Interstellar Cloud (or Local Fluff or LIC) is the interstellar cloud roughly 30 light-years (9.2 pc) across through which the Earth's Solar System is currently moving.

 

Thanks!

 

 

 

Assuming travel between both planets was instantaneous (magikz), what kind of explanation would I have to give to avoid making a plot hole? I know time dilation is caused by gravity differences, but can the stars these planets are going around cause noticeable effects at least to this scale?

 

If the travel is instantaneous, then travel backwards in time and possible time paradoxes would be a bigger worry than some time dilation Maybe like in the movie Interstellar you can have Planet X orbit a black hole and close enough for the time dilation to be sufficient. Obviously that opens even more holes like why the planet isn't torn apart from tidal forces or why isn't everyone dead from radiation coming from an accretion disk around the hole (assuming it has one).

[swansont]

when they come back they realize they have experienced some time dilation (7 Earth years to about 25 Planet X years).

 

Assuming travel between both planets was instantaneous (magikz),

 

 

Time dilation is caused by gravity and by relative motion. Trying to ascribe this to gravity would require very different gravitational potentials, but leaving the local value of g similar. That's probably going to lead to the remote planet being geologically unbelievable.

 

In reality, the difference in their elapsed time due to motion would be due to the time dilation (which is a change in rate of time) and the duration of their travel. Once you invoke instantaneous travel you have broken relativity, so it's a tough call to try and invoke some other aspect relativity. It's not fixable.

 

One option is to say the travel is not instantaneous, just very fast, such that the time dilation works out.