Relativity is Relatively Misunderstood

[Martin Hash]

There seem to be a lot of intelligent people who misunderstand Einstein's Theory of Relativity, and think time actually speeds up and slows down. I've seen articles that explain that astronauts age slower when they are in space. This misconception has been propagated through science fiction movies & books, and isn't well repudiated. Time does NOT slow down any more than it speeds up, it only seems to RELATIVE to the viewer because light travels at a constant speed. It's the light of past events that the spaceman sees as slowing down because he is also moving. His heart's still pumping blood, he's still aging at the same rate: if he was blindfolded while leaving and coming back to earth, it would be exactly the same as if he had been held in a dungeon.

[Martin Hash]

Let's say an alien on Alpha Centuri is looking through a telescope at Earth and wants an iPhone 10 that just came out in 2017. The Centurian jumps in his speed-of-light spacecraft and goes to Earth to get one. What iPhone does the alien actually end up buying?

[Martin Hash]

An astronaut travels at lightspeed to Alpha Centuri. When he gets there he looks through his telescope and sees the first customers getting an iPhone 10. What year did he leave Earth?

[K@th]

The astronaut left in 2017. He gets to Alpha Centuri in 2021 and then looks through a telescope that is looking at what happened 4 light years ago.

I admit I could be way wrong about this. Not my area - it's my best guess based on what I know.

[heydaralon]

The way I always try to explain relativity to people is to think of a textbook. A boring ass physics textbook. Now think about how much slower time would seem if you were trying to read about relativity in this textbook. Are you gonna read it? Fuck no. Me neither. Let's go watch Mob Wives. Time will speed way up when you watch a well-made gripping show like that. Forget this physics relativity shit.


And that, is the theory of relativity in a nutshell.

[Speaker to Animals]

The problem with your question, Martin, is that it presumes constant speed, which means no relativistic time dilation.


To capture relativistic effects, you need constant acceleration. So assuming this ship was accelerating at 1 g the whole trip (flipping over at the midway point to accelerate away from Alpha Centauri in order to arrive at that system in order to reach a parking orbit)..


Alpha Centauri: 4.37 light years from Sol system.

δTearth = γ·δTship

γ = 1 / √ 1 - v2/c2
v - velocity of the star ship
c - speed of light in vacuum = 299,792,458 [meters/second]

http://convertalot.com/relativistic_sta ... lator.html


Time passed on Earth: 6.002906337443892 years.
Time passed on spaceship: 3.583014607222012 years.


It takes 4.37 light years for the light to reach Alpha Centauri, so the year on Earth when he observed late 2017 would be 2022. He left 6 years earlier from Earth's perspective (though only 3.5 years ago from his perspective). So he left Earth in 2011.


Because Alpha Centauri is so close, this is the only way this scenario is really possible. You have to accelerate up to 100% C and then again to match the relative velocity of Alpha Centauri system. Just maintaining a constant 1 g acceleration would get you to about 95% C at one point, and then you'd need to flip over and start accelerating down retrograde anyway.

It's the acceleration that causes time dilation, not a constant speed no matter how fast.

[C-Mag]

Shoot a Nuke down a bug hole N you get a lot a Dead Bugs

[Martin Hash]

The astronaut left in 2017. He gets to Alpha Centuri in 2021 and then looks through a telescope that is looking at what happened 4 light years ago.

I admit I could be way wrong about this. Not my area - it's my best guess based on what I know.

You're correct, and the alien ends up with an iPhone 18; but did the alien go into the future 8 years? No, it only traveled for four years and retraced another 4 years worth of light. There was no time travel. Similarly, if the astronaut returns home, he would have lived 8 years during the round trip, and 8 years of time on earth would have elapsed, no time travel involved.

I've even read articles that say a quickly moving jet causes the pilot to have experienced time slower than the people watching him, but he didn't, he just saw the light leaving the clock arrive at his eyes slower, and as he heads back to the clock, time will seem to be speeding up, resyncing. That second part, the relationship between distance & perceived time due to the fact that light is not instantaneous, gets turned into "time travel" by a lot of pseudo-intellectuals.

[heydaralon]

Shit, where I grew up, you would get your ass kicked for even talking about relativity. Many of the Hispanic gangs in my area were Newtonian to the core. They didn't want to hear about anything else. You bring up Einstein, or Neils Bohr they would put you in the ICU. Gang initition mainly consisted of asking a white man Newton's Laws of Motion. If he failed to identify the laws, he would get lead straight to the dome. Fortunately, I knew the laws, so my life was spared from this thrill killing. The Hispanics even let me into their gang when I said that my grandfather grew up in Cuba and had an apple fall on his head. I will always remember those tough Hispanics. They were street smart, but they knew how to throw down in the classroom too. I ended up copying their homework and getting a Disney Dreamers and Doers award, and a scholarship at a prestigious university. I threw it all away though because its not easy to give up that lifestyle, and I got caught breaking into the Physics building stealing some triple beam balances and a pendulum that my ese's wanted to conduct some street experiments. I kept my mouth shut, and the homies had my back. They made sure when I got to jail, I had some 8th street muscle looking out for me. As soon as I showed them my inertia tattoo, I knew I was a motherfucking untouchable. I still talk to some of those crazy vatos to this day.

[Speaker to Animals]

Acceleration and gravity work the same way with respect to time dilation.

Time dilation is one of those things that makes the universe seem planned for intelligent life. Because of that, actually colonizing the galaxy is feasible. Sitting on a spaceship for a century sucks balls. Traveling the same distance with a nice 1 g of gravity from your constant acceleration and getting there in a few years is feasible.

We just have to figure out how to build ships that constantly accelerate (always applying thrust of some kind).