Time dilation in space travel

• DaveC426913
In summary, the conversation discusses the use of the Lorentz transform formula and time dilation formula to calculate subjective travel times for space travel. It also explores the idea of using a round trip with a stopover at a distant destination to measure the difference in time between Earth and the spaceship. The conversation also touches on the concept of non-simultaneity and the effects of high-speed travel on time and distance. It is mentioned that there is a graphical way of representing these concepts, but it is not yet complete. The conversation ends with a question about the nature of photons and their perception of time and distance.
DaveC426913
Gold Member
Many short story ideas I have involve space travel. I'm looking at the Lorentz transform formula and scratching my head.

Is there a relatively straightforward way to use the time dilation formulae and calculate subjective travel times for space travel?

Presume a spaceship accelerates at a=1g for the first half of its trip, and a=-1g for the second half, to stop at its destination. If the distance to its destination is d light years, how long does the trip take subjectively and how long does the trip take from stationary observer's PoV?

OK, now what if I change a to, say, 2g?

Two novels based on the time dilation formula are To The Stars by L. Ron Hubbard (a lush coming-of-age operetta), and Tau Zero by Poul Anderson (a sensawunda barn burner).

You should be able to use http://math.ucr.edu/home/baez/physics/Relativity/SR/rocket.html
to piece-together the trips of interest.

Last edited by a moderator:
That's great, thanks.

OK, so for a trip to, say, Vega, which is 27 ly distant, it would take 6.6 years ship's time.

But how long does that take Earth-time? I guess the only way to know is to come back. So a round trip, with a stopover at Vega would take 13.2 years ship-time. How much time has passed on Earth?

Oh wait. I see. That's covered. It takes 28 Earth years one-way. So, the round trip takes 56. Thus, upon reaching home, people on Earth will be older than astronauts by (56-6.6) 49.4 years.

And this holds true regardless of how long their stopover is. So, they fly to Vega, build their colony, and then in 20 years, they come back for supplies or shift-change. The Earth they come back to is 49.4 years older than they are.

Is there a graphical way of representing this? Light cone stuff?

My next step is to time events of multiple spacecraft in the story, so I understand sequence of events. (such as, if you accelerate at 2g instead of 1g, how much earlier do you arrive?)

DaveC426913 said:
Is there a graphical way of representing this? Light cone stuff?

Actually, there is... but it's not ready yet.
It's an extension of http://www.phy.syr.edu/courses/modules/LIGHTCONE/LightClock/

Last edited by a moderator:
Cool.
10char

DaveC426913 said:
That's great, thanks.

But how long does that take Earth-time? I guess the only way to know is to come back. So a round trip, with a stopover at Vega would take 13.2 years ship-time. How much time has passed on Earth?

.

Contarary to many explanations offered on these forums and in the literature, there is no need to return to Earth to explain the difference in time - When the spaceship arrives at Vega, the clock at Vega will read the same as a clock on Earth (since Earth and Vega are in the same inertial frame at all times during the one way journey). The spaceship clock will have logged less time than all of the clocks in the earth-Vega frame, and the difference is easily deteminable when the spaceship docks on Vega. If the traveler decides to return, under the same rates of acceleration and velocity, the time difference is simply doubled.

yogi said:
Contarary to many explanations offered on these forums and in the literature, there is no need to return to Earth to explain the difference in time - When the spaceship arrives at Vega, the clock at Vega will read the same as a clock on Earth (since Earth and Vega are in the same inertial frame at all times during the one way journey). The spaceship clock will have logged less time than all of the clocks in the earth-Vega frame, and the difference is easily deteminable when the spaceship docks on Vega. If the traveler decides to return, under the same rates of acceleration and velocity, the time difference is simply doubled.
Well yes, I deliberately doubled the trip, but not out of a misguided necessity. My intent was to avoid any additional complexity in terms of non-simultaneity of events between Earth and Vega. While you're on Vega, how do you know for sure what time it is on Earth?

travelling at almost the speed of light, so fast in fact that it would arrive just a few millimeters behind the photons that were emitted at the same time.

one section of this article, has a chart of the Time Dilation experienced by this high speed particle.

it show that this particle would travel a distance of 2000 lightyears but due to its speed, its would make that trip in 3.5 minutes, (IN ITS frame of reference).

so you are looking through a telescope at an object 2000 yl away, and you say "what does it look like NOW??".

its 1pm Nov 19, 2006, you just into your spaceship, that travels at just under the speed of light, and you travel to that object 2000 ly away.

your watch now reads 1:03:30, and 3.5 minutes have elapsed since you viewed this object that YOU ARE NOW AT.

you turn your spaceship around, and point towards earth, and flash your headlights. at the same time, you get on your faster than light space phone and ring up earth.

you ask them to look out at the object, and to see if they can see you.

you ask the person on Earth what year it is, and they say, the time is 1:04year 4006.

only 3.5 minutes are elapsed for the traveller, and 2000 years for the people who stayed on earth.

to me that puts into question about when an event actually occures, because if this high speed particle was an atomic clock, and you times how land ago that event occued, its would say that an event that occurred 2000 yl distance, happened 3.5 minutes ago,

and if you asked the photon how long ago that event occured, its would say "just then". or NO time. and therefore for the phone no distance either.

(is a photon just a sub-atomic particla with a zero half life, as soon as it experiences "TIME", its decays ?? )

sorry for long post, and for not really asking anything, my question is this correct. or way off track.

but the "oh my god particle" article is a good read

http://www.fourmilab.ch/documents/ohmygodpart.html

That's one seriously fast - and heavy - proton.

"OK, so for a trip to, say, Vega, which is 27 ly distant, it would take 6.6 years ship's time.
But how long does that take Earth-time? I guess the only way to know is to come back. So a round trip, with a stopover at Vega would take 13.2 years ship-time. How much time has passed on Earth?
Oh wait. I see. That's covered. It takes 28 Earth years one-way. So, the round trip takes 56. Thus, upon reaching home, people on Earth will be older than astronauts by (56-6.6) 49.4 years.
And this holds true regardless of how long their stopover is. So, they fly to Vega, build their colony, and then in 20 years, they come back for supplies or shift-change. The Earth they come back to is 49.4 years older than they are."

That doesn't sound right. Wouldn't it be 49.4 years elapsed on Earth plus stopover time, since you aren't traveling while stopped.

I've always wanted to try and make a well programmed spreadsheet where I can plug in the distance and the acceleration and it would give me the time on the clock, I've always failed :(

EDIT: Oops, didn't realize how dead this thread was. Apologies for the necropost.

Dave, please see link to the very new and exciting explanation of time dilation:

Time Dilation – Explained. Description of the experiment verifying the interpretation of time dilation of the Theory of Relativity

Last edited by a moderator:
ryan_m_b said:
I've always wanted to try and make a well programmed spreadsheet where I can plug in the distance and the acceleration and it would give me the time on the clock, I've always failed :(

EDIT: Oops, didn't realize how dead this thread was. Apologies for the necropost.

There are lots of relativity calculators online that will do this.

Calls said:
Dave, please see link to the very new and exciting explanation of time dilation:

Not a chance am I opening an unknown .doc file. Save it as a PDF and I'll look at it.

Last edited by a moderator:
DaveC426913 said:
There are lots of relativity calculators online that will do this.

Really? I've never found any. All I've managed to find are calculators that give the time dilation factor and once found a journey time calculator for continuous thrust. What I want is something where I can plug in distance, acceleration and if there is a midway turnover (to decelerate/intercept) and get back the total time as measured by the ship and by an observer who is relatively at rest.

ryan_m_b said:
Really? I've never found any. All I've managed to find are calculators that give the time dilation factor and once found a journey time calculator for continuous thrust. What I want is something where I can plug in distance, acceleration and if there is a midway turnover (to decelerate/intercept) and get back the total time as measured by the ship and by an observer who is relatively at rest.

Try this one:
http://www.orionsarm.com/fm_store/RTTCalc.htm

This one is kind of cool too. Although you won't see the math behind the calculations.
http://www.cthreepo.com/lab/math1.shtml

I found this one rather useful.

http://johanw.home.xs4all.nl/PhysFAQ/Relativity/SR/rocket.html

Although not a calculator it gives you the math to work it out.

Last edited by a moderator:

What is time dilation in space travel?

Time dilation in space travel is a phenomenon in which time appears to pass slower for objects in motion compared to objects at rest. This is due to the effects of special relativity, which states that the perception of time is relative and can be affected by the speed and gravity of an object.

How does time dilation occur?

Time dilation occurs because of the constant speed of light in the universe. As an object approaches the speed of light, time for that object appears to slow down relative to an outside observer. This is because as an object's speed increases, its mass also increases, which in turn affects the perception of time.

What is the difference between time dilation and time travel?

Time dilation is a scientific phenomenon that occurs due to the effects of special relativity, while time travel is a concept that is mostly explored in science fiction. Time dilation only affects the perception of time for an object in motion, while time travel involves physically moving through time to a different point in the past or future.

Can time dilation be experienced on Earth?

Yes, time dilation can be experienced on Earth, but the effects are very small and can only be observed in extremely high-speed scenarios or in the presence of strong gravitational fields. For example, astronauts in orbit around the Earth experience a very slight time dilation compared to those on the surface due to their high speed.

What implications does time dilation have for space travel?

Time dilation has significant implications for space travel, as it means that time passes slower for objects in motion. This can lead to astronauts aging at a slower rate than people on Earth, which could potentially allow for longer space missions. However, it also means that time would pass differently for travelers compared to those on Earth, which could have social and logistical implications for long-term space travel.

• Special and General Relativity
Replies
25
Views
617
• Special and General Relativity
Replies
65
Views
4K
• Special and General Relativity
Replies
20
Views
1K
• Special and General Relativity
Replies
17
Views
2K
• Special and General Relativity
Replies
27
Views
1K
• Special and General Relativity
Replies
17
Views
741
• Special and General Relativity
Replies
63
Views
3K
• Special and General Relativity
Replies
21
Views
1K
• Special and General Relativity
Replies
5
Views
1K
• Special and General Relativity
Replies
98
Views
2K