Planets & Relativity: Time Dilation in Our Galaxy

In summary, the stars in a galaxy are stable relative to each other, and there are relativistic effects that are not great.
  • #1
Runei
193
17
Hey there

I was wondering: Are the stars and their systems in our galaxy stable relative to each other? I mean - how fast do they move in relation to one another. Are there significant time dilation on some planets or systems in our galaxy relative to us?

I'm thinking about this because I was watching Star Trek, and I was wondering if it wouldn't create problems of time determination if different systems have significant time dilation :)

Just a funny thought :)
 
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  • #2
The orbital velocity of stars in a galaxy is pretty much constant regardless of the distance from the galactic centre.
http://en.wikipedia.org/wiki/Galaxy_rotation_curve
Which, by the way, is a result that seems to contradict the Keplerian intuition(slower orbital velocity the farther you get - as in e.g.our solar system), and which led to the idea of dark matter.
The orbital speed in Milky Way is roughly 200-250 km/s.

Note that this still means that the galaxy should(intuitively) "wind itself up" into an ever tighter spiral, as the stars closer to the galactic disk's rim have to travel longer distance(2∏R, R=distance from the centre) than the ones closer to the centre, despite having very similar speed.
So, accordingly, stars do not stay in the same places relative to each other. The ones close to the centre overtake those farther away on a regular basis.

That there exist well-defined arms inspite of that is addressed by the density wave theory:
http://en.wikipedia.org/wiki/Density_wave_theory(nice animation included)

Additionally, stars may have some additional velocity unrelated to their orbital speed, due to e.g.close encounters with other stars.


As for the relativistic effects - these velocities are still significantly lower than the speed of light, so the effects are not great (in the order of magnitude of miliseconds per day).
Still, seeing how the relativistic effects cause e.g. clocks on Earth to run differently than those of Earth's satellites( http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit5/gps.html ), it's not completely negligible - especially for precise measurements.

Note that the gravitational relativistic effects(time runs slower near massive bodies) are much greater in the case mentioned above.



Bottom line: disregarding all the other problems that warping around the galaxy might pose, time synchronisation might be necessary upon arrival, but it wouldn't be anything large.
 
  • #3
Thank you! Great answer! :)
 

What is time dilation?

Time dilation is a phenomenon predicted by Einstein's theory of relativity, where time appears to pass slower for an object moving at high speeds or in a strong gravitational field compared to a stationary observer. This means that time is not constant and can be affected by factors such as velocity and gravity.

How does time dilation affect planets?

Time dilation affects planets in two main ways. First, it is responsible for the difference in the passage of time between planets with different gravitational fields. For example, time would pass slightly slower on a planet with a higher gravitational pull, such as Jupiter, compared to a planet like Earth. Second, time dilation also plays a role in the orbit of planets around the sun, causing them to experience a slight time dilation effect as they move at high speeds.

What is the role of gravity in time dilation?

Gravity plays a significant role in time dilation. According to Einstein's theory of general relativity, gravity is not a force but rather a curvature of spacetime. Objects with mass, such as planets, create this curvature, and the stronger the gravitational pull, the more significant the effect on time dilation.

Can time dilation be observed in our galaxy?

Yes, time dilation has been observed in our galaxy. One of the most famous examples is the Hafele-Keating experiment, where atomic clocks were flown on airplanes in opposite directions. The clocks showed a difference in time when they returned, confirming the effects of time dilation due to the high speeds of the airplanes.

How does time dilation impact our daily lives?

While the effects of time dilation may seem insignificant in our daily lives, it is a crucial factor in modern technologies such as GPS. GPS satellites orbit at high speeds and experience time dilation, which must be accounted for in the calculations to provide accurate location data. Time dilation also plays a role in space travel and the aging of astronauts on long-duration missions.

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