# Time Dilation, Interstellar Travel, and "The Forever War"

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• hawi
In summary, the conversation discusses the book "The Forever War" by Joe Haldeman, which explores the impact of time dilation on interstellar travel and the effects it has on soldiers returning to Earth. The conversation also addresses a question about the implications of time dilation on the progression of war and the development of weapons and strategies. The conclusion is that time dilation may not directly affect the sequence of events, but it does make it difficult to predict the technological advancements of an enemy during a long journey through space.
hawi
Dear community,
I have no formal education in physics, but I think I have understood some of the basic concepts and ideas in SRT. I am currently trying to find a solution to a problem that came up during my reading of Joe Haldeman's "The Forever War", a Sci-Fi novel that deals with the impact of time dilation on intertsellar travel. A summary can be found here: http://www.tor.com/2012/01/17/future-shock-the-forever-war-by-joe-haldeman/.

Most people talking about Haldeman's novel focus on the impact of time dilation on returning soldiers: In order to reach the frontline and come back after the battle, they need to cover great distances at velocities close to c. The clocks on Earth and the soldier's clocks are heavily de-synchronized due to time-dilation and the veterans return to a society that is barely recognizable for them, with all their families and friends dead.

So far, so good. However, Haldeman mentions also a second consequence of time-dilation, but I am unsure if this consequence is legitimate. Here is the problem: We normally think of war as a process during which events occur sequentially and in which both parties evolve in reaction to each other. For instance, party A invents a new strategy/weapon and, as a reaction, party B develops a counter-strategy/adequate defensive weapon. Yet, Haldeman seems to imply that this conception of the sequentiality of events in the process of war is also undermined by time-dilation. Take, for instance, the following passage of Haldeman's book:

"And as with any engagement, because of time dilation, there was no way to tell what sort of weaponry they [the aliens] would have. They might have never heard of the stasis field. Or they might be able to say a magic word and make us disappear."

The point seems to be that, prior to an encounter with aliens, there is no way to know how sophisticated their weapons will be due to time-dilation. However, my problem is that I don't really see why time dilation should be relevant here: Assume that we have one common measure of time, for instance from the perspective of Planet Earth. A new technology, say the stasis field, is invented in the year t1. The aliens develop a counter weapon at some later point in time, t2. Now imagine a group of soldiers euqipped the stasis field that engages in a fight with aliens at some later point in time t3. Now, if this group of human soldiers wants to determine whether the aliens will be equipped with the counter-weapon against the stasis field, the only relevant piece of information is whether the aliens have left their base before or after t2. Time-dilation seems to be completely irrelevant here, because it only concerns how much objective time has passed for the aliens on their spaceship during their journey with velocities close to c. But time dilation doesn't mess up the order of events t1, t2 and t3, right? Or am I missing something here? Does the relativity of simultaneity play a role here?

Many thanks for your help,
HaWI

The way I read it, all that was meant was that information about anything takes time to travel. So you just don't know what tech will the Taurans have by the time you get there. Every piece of intel you get is always going to be outdated. Time dilation doesn't have anything to do with it, apart from messing with one's intuitions.

Also, if you're going to strike a base you don't know when the base last got upgraded. Since it takes you hundreds of years to reach your objective you may find that the base was closer to the bad guys' home than yours, and got upgraded with tech that's only fifty years old compared to your two hundred year old stuff.

I don't think that's an effect of time dilation so much as the size of the battlefield. Time dilation just let's you survive the journey.

## 1. What is time dilation?

Time dilation is a concept in physics that describes the difference in the passage of time between two objects that are moving relative to each other. This means that time can appear to pass at a different rate for two observers who are moving at different speeds.

## 2. How does time dilation affect interstellar travel?

Interstellar travel involves traveling at extremely high speeds, which can cause significant time dilation. This means that time may pass slower for the travelers compared to those on Earth. This can result in astronauts experiencing less time than their friends and family back on Earth.

## 3. Can time dilation be observed in real life?

Yes, time dilation has been observed in real life through experiments with atomic clocks and high-speed particles. For example, GPS satellites have to take into account time dilation effects in order to maintain accurate time readings.

## 4. How does "The Forever War" incorporate time dilation?

"The Forever War" is a science fiction novel that explores the effects of time dilation on a group of soldiers who are sent to fight an interstellar war. Due to the high speeds of their spacecraft, the soldiers experience significant time dilation, making them age at a slower rate compared to Earth, resulting in them being disconnected from the society they left behind.

## 5. Is time dilation a proven concept?

Yes, time dilation is a well-established phenomenon in physics and has been confirmed through numerous experiments and observations. It is a fundamental concept in Einstein's theory of relativity and has been used in various applications, such as GPS technology and space travel.

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