If you have read about Einstein's relativity, or watched Interstellar, you would have read or seen that time can be dilated relatively. Objects moving close to the speed of light would have a slower observed time. The Twin Paradox would be a great example of this.

That said, what if maybe we are ahead in technological advancements because of Relativity? Our solar system is in a certain area in the Milky Way less dense than most parts: perhaps moving slower, thus relatively faster in time. So relatively, we are advancing in a much faster pace because of relativity. What are your thoughts on this?

Side question: If our star system happened to be close to the center of the galaxy, wouldn't it make sense to send a colony to slower parts of the galaxy and have them develop technology to be brought back to us?

My facts might be inaccurate, please edit if necessary.

  • $\begingroup$ Are you suggesting our Earth or the Entire Solar System are moving at relativistic speed compare the other celestial bodies in our galaxy? Don't forget time dilation is affected by mass too? And assuming we ain't alone there might be great difference in intelligent level also some star system could be much older/younger than ours. $\endgroup$
    – user6760
    Oct 13, 2016 at 5:21
  • $\begingroup$ I see three people have voted to close. I would like to state that I think the question should remain open. It contains some wrong assumptions but it is a well-formed, answerable question. $\endgroup$ Oct 13, 2016 at 8:00
  • $\begingroup$ Possible, but not likely. As @YoustayIgo pointed out, the time dilation is next to negligible. Also, the universe is 14 000 million years old. Humans have been around and advanced their technology for about 0.1 million years, the really big breakthroughs (civilization, writing, digital watches) happened in the past 0.01 million years, and space-faring happened in only the past 0.0001 million years. So if we are ahead or behind anyone else when it comes to development, the overwhelming probability is that this is due to other reasons than time dilation. $\endgroup$
    – MichaelK
    Oct 13, 2016 at 8:12
  • $\begingroup$ @Lostinfrance thank you for your support. I should have given more thought on the question. $\endgroup$
    – Brian
    Oct 13, 2016 at 11:42
  • $\begingroup$ @MichaelKarnerfors that is true. But he also pointed out that velocity is not the only factor for time dilation, which means in systems with a stronger force of gravity, the effects would be great too. I have yet to read about this. $\endgroup$
    – Brian
    Oct 13, 2016 at 11:45

3 Answers 3


You have several preformed misconceptions about relativity in your question. I will try to address them all here.

1- Time Dilation Due To Relativity/Speed

It happens that time dilation due to relativity becomes really evident at extremely high speeds. The time dilation experienced due to velocity is expressed as $$\Delta t = \frac{t}{\sqrt{1-\frac{v^2}{c^2}}}$$

where v is the velocity of the object under question and c is the speed of light in vacuum. If you solve the equation for various values of v, you would observe that while there is definitely some time dilation for every moving object, the effect is negligible, until we approach at least 10% the speed of light.

Now let us examine the speeds at which we (humans on Earth) are travelling. Earth is moving around the sun at a speed of nearly 30 km/s. While being much, much faster than a rifle bullet, it is nothing when compared to the speed of light, which is 300000000 m/s. So we are moving at 0.01% of the speed of light that way. Next is our speed in the solar system, moving around the galactic center. A quick google search tells me this speed is 828,000 km/h or 230 km/s (source). One again, while being mind bogglingly fast, it is only about 0.076% of the speed of light. Time dilation at these speeds is negligible for all practical purposes.

While our galaxy is also moving along in the cluster of galaxies and the cluster is adrift in the universe, but these speeds can hardly be calculated accurately due to the expansion of space in the universe which is increasing at the distance between far flung galaxies at velocities faster than the speed of light. So relativity equations don't really apply here.

2- If our star system happened to be close to the center of the galaxy, wouldn't it make sense to send a colony to slower parts of the galaxy and have them develop technology to be brought back to us?

While star systems near the galactic center have time dilated for them (not due to higher speeds, but due to gravitation), it would be a completely impractical idea to try and settle a colony at regions of faster time so that they develop technology faster and that be brought back to us. Some of the reasons I can think of, are following:

1- Galactic center is a really really supermassive blackhole with extremely high gravity. Sending a spaceship to large distances away from this monster would be very very difficult, specially considering that you want to send the spaceship from near the galactic center to the outer reaches of the galaxy.

2- Before you send the huge spaceship containing thousands of people to start a colony on another planet in the outskirts of the galaxy, you first have to find a habitable planet in the outskirts of the galaxy. That is not an easy task, considering the startlingly long distances involved, the next-to-nothing technology we have for detailed mapping of all star systems and their planets at such vastness and how we cannot tell about habitability of planets at those distances. There is 99.9999999999999999% chance we would send our pioneers to certain death.

3- Considering that the galaxy is really, really huge and interstellar space looking dark to the eye is fraught with horrors like blackholes and neutron stars with horrific magnetic and gravitation fields, the spaceship would be in for nearly certain doom when considering travelling from galactic center to galactic outskirts.

4- And when those pioneers would finally reach the outskirts of the galaxy (in tens of millions of years, even if they travel at 5% of the speed of light, which is a very fast speed, for human standards), the people who would be landing on the exoplanet would probably be biologically different than us and definitely have a completely different psychology. And you can be 100% certain they would not be interested at all at sending back the results of technological advancement they achieve. They would no longer be emotionally, culturally or biologically linked to us anymore.

5- Also, forget any meaningful communication between the planets. Our galaxy is 100,000 light years across (source) meaning that it would take at least 50,000 years just for one message to reach either side. And then you would have to consider where to focus your message at (considering that the position of the star systems and planets would be very different after 50,000 years) and then process the signal to undo the red or blue shift. Then there is gravitational lensing effect which might bend the communication waves away from their designated straight path. In short, forget any communication at all.

Edit to add: In response to Michael Kjörling

You have stated the correct statistics, but I'm afraid you have ended up with a limited view of the journey and the dangers it holds. While a straight trip from the galactic center to the outskirts of our galaxy would indeed take a few multiples of 50,000 years (when traveling at a significant fraction of the speed of light), travel is anything, but straight (due to gravitational and magnetic fields of stars).

For one, you have not considered the possibility of the source civilization living on north side of the galactic center and the destination start system occurring on the southern outstretch of the galaxy. You cannot travel through the galactic center. You would have to go around it, and considering its immense gravity and vast event horizon, travelling at 5% the speed of light, you would have to make very very large turn around it, taking tens of thousands of years.

Furthermore, stellar density is much greater near the galactic center, implying that the spaceship would have to endure gravitational tugs from multiple sources, the moment it reaches interstellar space. Neglecting the impossible fuel requirements, travel would hardly (if ever possible at all) be in a straight line, making the route very complex and lengthy.

Thirdly, you have not accounted the fact that in case (which is highly likely) the spaceship the spaceship is a couple dozen thousand years late, it will find that its destination stellar system has moves millions of miles ahead and will have to actually chase it to reach it, further increasing journey time.

  • 3
    $\begingroup$ As you say, the Milky Way is roughly 100,000 ly across, so from the center to the outer parts is 50,000 ly. At 5% the speed of light, such a trip will take about a million years. Hardly "tens of millions" of years. And interstellar space is virtually all empty. Sorry, this answer started out good, but then descended into something that feels anything but science-based. $\endgroup$
    – user
    Oct 13, 2016 at 7:50
  • $\begingroup$ @Youstay Igo I was wrong to assume that time is only affected by velocity. I was thinking of a way that the effects would practically be useful. You're right, the travel between worlds would require an immense amount of energy, and with the technology we have today, it would be impractical. $\endgroup$
    – Brian
    Oct 13, 2016 at 11:12
  • 4
    $\begingroup$ This is a nitpick, but all of your calculations involving the speed of light are off by a factor of a thousand. The speed of light is approximately 300,000,000m/s, not km/s as listed. $\endgroup$
    – Catgut
    Oct 13, 2016 at 12:23
  • $\begingroup$ You're making some weird assumptions to make things more difficult. Civ on the north side, destination on the south side, for instance. First, you wouldn't pick a destination on the south side, for exactly that reason. Second, it's really difficult to see through the galactic core, so they wouldn't even be able to find an exoplanet on the other side if they wanted to. Next, no navigator in their right mind would navigate to exactly where the star would be if everything goes as planned. They'd put in a buffer and constantly adjust course for exactly this reason. $\endgroup$
    – Azuaron
    Oct 13, 2016 at 14:47
  • $\begingroup$ Finally, the biggest assumption you're making is what space travel will look like. Brian never said what level of tech we were talking about. If we're talking about a civilization that can open wormholes and instantly bridge the gap between the core and the rim, then everything you've said in part 2 is irrelevant. In that scenario, it would make a lot of sense to have the science peasants of the galactic arms bring back rapidly advancing technology to the core elites (if the core elites could maintain control). $\endgroup$
    – Azuaron
    Oct 13, 2016 at 14:52

There are some wrong assumptions in your question. Other answers have already covered some of the issues, so I would like to focus on one misconception in particular.

If you have read about Einstein's relativity, or watched Interstellar, you would have read or seen that time can be dilated relatively. Objects moving close to the speed of light would have a slower observed time. The Twin Paradox would be a great example of this.

Actually the Twin Paradox is not an example of simple time dilation. There are two different ideas involved.

Two observers in non-accelerated (straight line, constant speed) motion relative to each other both perceive the other as undergoing time dilation. To see why, consider this description of a thought experiment from Einstein for Dummies involving two spaceships moving relative to each other. You are on one ship, your friend Amber is on the other. (It makes a lot more sense if you click on the link to see the diagrams.) First you do something involving just you:

Imagine that you’re on a spaceship and holding a laser so it shoots a beam of light directly up, striking a mirror you’ve placed on the ceiling. The light beam then comes back down and strikes a detector.

Now consider your friend Amber in a ship moving at a speed of 0.5 c relative to your ship. She does the same thing with the laser. From her own point of view it looks exactly the same for her as it did for you when you did it. But from her point of view looking at you,

Amber would see your beam of light travel upward along a diagonal path, strike the mirror, and then travel downward along a diagonal path before striking the detector. In other words, you and Amber would see different paths for the light and, more importantly, those paths aren’t even the same length. This means that the time the beam takes to go from the laser to the mirror to the detector must also be different for you and Amber so that you both agree on the speed of light.

And, of course, if you were looking at her exactly the same is true. That's why you both see the other as slowed down.

So how can all that be compatible with the Twin paradox? If there's no absolute frame of reference, how does the universe know which twin stays young and which twin gets old?

This is a very common question. I refer you to this question and its answers on Physics Stack Exchange.

Quoting the question,

The paradox in the twin paradox is that the situation appears symmetrical so each twin should think the other has aged less, which is of course impossible.

There are a thousand explanations out there for why this doesn't happen, but they all end up saying something vague like it's because one twin is accelerating or you need general relativity to understand it.

The top voted answer is more precise but heavy on the mathematics. I think that another answer by Jan Lalinsky is clearer for the layman:

Answer: equations of special relativity refer to quantities and coordinates measured in inertial frames only. Consequently the calculation of proper time elapsed on the moving watch corresponding to measured coordinate time can be done only if this coordinate time was measured in an inertial frame.

Only the Earth twin can be in an inertial frame all the time, while the traveler twin can't, as he needs to accelerate and decelerate to get back to the Earth.

So there is actually no paradox - although the two observations of speed are the same, other things are not and this destroys the symmetry of the twins. The traveler twin has no way to use the time dilation formula because he has no coordinate time measurements that would qualify.

There is an explanation of the term "inertial frame" here.

So, how does all this relate to your question? You said,

...what if maybe we are ahead in technological advancements because of Relativity? Our solar system is in a certain area in the Milky Way less dense than most parts: perhaps moving slower, thus relatively faster in time. So relatively, we are advancing in a much faster pace because of relativity. What are your thoughts on this?

Youstay Igo's answer has already said that the relative velocity of Earth compared to the sun and of the solar system compared to the galactic centre is at nowhere near relativistic speed. I'd add that the same is true going outward to the galactic rim. Youstay Igo also said that motion relative to other galaxies is irrelevant because the expansion of the universe makes the whole notion of "velocity" break down.

All this is true, but the point of my answer is that even if it were not true - even if there were two galaxies or parts of a galaxy* that happened to be moving at relativistic speeds relative to each other, given the scale their relative motion would be near as dammit unaccelerated. That means the two places both would consider the other to be undergoing time dilation. At the scale we're talking about there are no galaxies or part of galaxies that can be absolutely defined as slow moving or fast moving.

You also asked whether differences in density between parts of the galaxy could produce relativistic time dilation effects. It is correct that general relativity does predict gravitational time dilation. However Michael Kjorling's comment pointed out that interstellar space is virtually empty. There are incredibly massive objects such as black holes, particularly the supermassive black hole at the galactic centre, but you can't live in them. There is no widespread area (er, volume) of the galaxy where colonists could live that is so much less dense than another as to make any difference.

Side question: If our star system happened to be close to the center of the galaxy, wouldn't it make sense to send a colony to slower parts of the galaxy and have them develop technology to be brought back to us?

As I said earlier, there is no "slower part of the galaxy" that meets your requirements. But leaving that aside, in any situation whereby the colonists accelerate to travel to their destination and again to come back to Earth, the time dilation works the other way. It's the colonists who would be like the twin who stays young. They would experience less time passing and would return to find Earth incredibly advanced in technology, if we were lucky enough to have survived as a species.

*The only way I can envisage one "part" of a galaxy moving at relativistically significant speed compared to other parts of the "same" galaxy is as the result of two formerly separate galaxies colliding and passing through each other. I hope this doesn't happen often.

  • $\begingroup$ Correct me if I'm wrong, but the first part where you talked about the Twin Paradox, that describes how Special Relativity came to be, right? It is a thought experiment on how light is supposed to behave within a rocket travelling at extreme speeds as perceived by someone relatively still. Since they have observed beforehand that light, in every perspective, has a constant speed, the thought experiment suggests it should be wrong. Einstein suggested on the other hand that the thought experiment is correct, provided time is not constant. $\endgroup$
    – Brian
    Oct 13, 2016 at 14:02
  • $\begingroup$ As for the time of reference, does it matter if one is slower than the other? In that case, two objects at different speeds would still have different perception of time. $\endgroup$
    – Brian
    Oct 13, 2016 at 14:05
  • $\begingroup$ This is going to have to be quick because I have to go out. If I'm wrong I hope someone corrects me. Special relativity deals only with the motion of objects as seen from inertial frames. Acceleration and gravity are not involved. (Usually, anyway. I think there might be certain exceptions but I can't remember.) So it doesn't describe the happenings in the twin paradox, which involves someone accelerating. Other than that, correct, Einstein's insight was that c is always the same for all observers. You reconcile the apparent problems by fiddling with time and distance. $\endgroup$ Oct 13, 2016 at 14:22
  • $\begingroup$ Regarding the second comment, A's velocity relative to B is always equal in magnitude to B's velocity relative to A. So each perceives the other as undergoing equal time dilation. You could have a third observer C, from whose point of view A and B had different velocities and hence different levels of time dilation. $\endgroup$ Oct 13, 2016 at 14:24
  • $\begingroup$ Good point. I guess in this case, the relativistic observer would be the galaxy itself, if that makes sense. I'll wait for a third opinion. Thanks for your time. $\endgroup$
    – Brian
    Oct 13, 2016 at 14:28

Please read Youstay Igo's answer also!

"Is it possible that we are the most technologically advanced race in our galaxy?"
Yes, possible. The question itself targets on if there is any other race in an area which is not yet possible to map by humans to the detail of inhabitant races' technology, be more advanced in technology (which can have several areas). To prove or be against we can't collect facts, so it stays theoretical.

Technological advancement is also depending on countless parameters! One of it is how much effort does the given race put in researching, and how gifted they are in the process. It is race specific. A more peaceful race might figure nuclear theory in 25 000 years. Or maybe even in 2 years. They might have already discovered 75 millenia ago, but could face disaster.


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