I thought I read it's the other way round, so if you travel at close to the speed of light then come back to earth, everyone else will have aged more than you.
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You see, even I am getting confused now, it is very confusing believe me! Let me quote this from
MIT's technology review, this will explain it far better than I ever could.
"Time dilation goes back to Einstein’s theory of special relativity, which teaches us that motion through space actually creates alterations in the flow of time. The faster you move through the three dimensions that define physical space, the more slowly you’re moving through the fourth dimension, time––at least relative to another object. Time is measured differently for the twin who moved through space and the twin who stayed on Earth. The clock in motion will tick more slowly than the clocks we’re watching on Earth. If you’re able to travel near the speed of light, the effects are much more pronounced.
Unlike the Twin Paradox, time dilation isn’t a thought experiment or a hypothetical concept––it’s real. The
1971 Hafele-Keating experiments proved as much, when two
atomic clocks were flown on planes traveling in opposite directions. The relative motion actually had a measurable impact and created a time difference between the two clocks. This has also been confirmed in other physics experiments (e.g., fast-moving muon particles
take longer to decay).
So in your question, an astronaut returning from a space journey at “relativistic speeds” (where the effects of relativity start to manifest—generally at least
one-tenth the speed of light) would, upon return, be younger than same-age friends and family who stayed on Earth. Exactly how much younger depends on exactly how fast the spacecraft had been moving and accelerating, so it’s not something we can readily answer. But if you’re trying to reach an exoplanet 10 to 50 light-years away and still make it home before you yourself die of old age, you’d have to be moving at close to light speed."
The wording in the first paragraph is a little convoluted there, but when he says;
The clock in motion will tick more slowly than the clocks we’re watching on Earth
He is specifically referring to when you are watching the clock from earth, which he references earlier in the paragraph by saying;
the more slowly you’re moving through the fourth dimension, time––at least relative to another object.
The first paragraph basically takes the assumption you are watching from earth.
Time has travelled the same for all parties from the perspective of their own party, but, one party has clearly travelled at a different rate of time than the others, because when they come back to earth, they are different ages. While this specific article doesn't use the words time travel per say, (many do) when you travel through time at a different rate relative than others, you have time travelled.
If you came back to earth and you were younger than everyone else because time had physically slowed down for you, like was suggested. You wouldn't have time travelled. That slowing down of time for the person moving, would be the way everything stays in synchronisation within space time. Because that would mean the slowing of time for you would make many of your seconds on the spaceship, equal to a single earth second. The amount of seconds that would make up an earth second, would match up exactly and correctly to the proportions that you are younger, compared to the people on earth. Which is in no way time travel.
But as I mentioned earlier and as articles posted explain, it doesn't work like that. Time ticks the same for everyone. Time dilation happens between the two parties and not to the actual parties themselves, it doesn't just work like that, it could never work like that, it goes fundamentally about how space time works. Therefor, the only way the universe can synchronise the dilation in time back up, that was caused by the relative differences in movement, is the jump in time relative to one another. Aka time travel.
I totally get the argument being put forward, but there is a fundamental mis understanding in the assumption that the passage of time slows down from one party compared to another. It does not. The passage of time stays the same for both party's, it is just the dilation between the two parties, that gives the appearance that is has slowed down for the other party. This is extremely important, because if time did not stay the same, travel through it would be impossible. Yet it is not. Think of it like the doppler effect, it almost is, when an object like an ambulance has passed you by. You hear the sound being generated in a lower pitch, as the object generating the sound moves away from you. Not because the object generating the sound has actually lowered the pitch of the audio, but because the sound has dilated in between the objects, as the space between the two objects grows. Yet to you stood still, it seems like the ambulance has lowered the pitch of the siren. They do not work in exactly the same way, but very very similar. Enough to use them as an example here. As time doesn't work in the same way as it would with the doppler effect when sound is coming towards you. Change the sound waves being stretched out / dilated for space time and you are in a similar ball park.
Hopefully that makes sense.....I need a strong drink after thinking all that over in my head
. Sorry if I am going off on one. I could talk about this for hours. Truly fascinating stuff. But also, truly confusing stuff. Some of the most confusing stuff known to man I would argue.
