# How far could we actually go into the future using relativity? **URL:** \ **Category:** Factual Questions\ **Created:** [September 20, 2018, 9:22pm UTC](https://boards.straightdope.com/t/how-far-could-we-actually-go-into-the-future-using-relativity/821654 "2018-09-20T21:22:52Z")\ **Posts on this page:** 9\ **Page:** 2
**Author:** ![Lucas\_Jackson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lucas_jackson/32/303_2.png) [@Lucas\_Jackson](https://boards.straightdope.com/u/Lucas_Jackson)\ **Post date:** [September 21, 2018, 2:00pm UTC](https://boards.straightdope.com/t/how-far-could-we-actually-go-into-the-future-using-relativity/821654/21 "2018-09-21T14:00:49Z")
> [@Jasmine](#): > > The closer one gets to the speed of light, the more time “slows down” locally in relation to everything else that is not moving at that speed. So, if you had propulsion technology good enough to reach, say 90% of the speed of light, for each day on board, two and a quarter days pass for an observer on earth with the respect to the ship in which you are traveling. > > The rest is math. If you traveled for twenty years, you return home 45 years later on earth or, from your perspective, 25 years into what you would consider the “future” on earth. As Einstein would say, it’s all “relative”. It seems to me the OP understands the general concepts relativity. We don’t have technology that can get us to 90% c. The question is - given our current technology, what is the greatest time dialation we could achieve. ---
**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\ **Post date:** [September 21, 2018, 3:59pm UTC](https://boards.straightdope.com/t/how-far-could-we-actually-go-into-the-future-using-relativity/821654/22 "2018-09-21T15:59:00Z")
> [@Great\_Antibob](#): > > The biggest shift achievable in 20 years? I’d be immensely surprised if it approached even 1 second. At the moment, the best we could hope for is sending somebody into orbit for long periods of time. Right. To achieve 1 second, an astronaut would have to travel 50 times faster than than ISS for 784 days. The ISS travels at 17,150 mph. 50 times that is 857,500 mph. Voyager 1 went 38,000 mph. The Parker Solar Probe will become our fastest space craft at 430,000 mph, but that’s its maximum speed at its closest to the sun and so won’t reach that speed for six years. Twice as fast as a space craft skimming the sun and maintaining that for more than two years. Unless there’s an awesome breakthrough we won’t see anything like that in 20 years. Even going five times faster for 20 years would be an amazing accomplishment. We have no conception of how hard it is to travel fast. ---
**Author:** ![Teuton](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/teuton/32/3864_2.png) [@Teuton](https://boards.straightdope.com/u/Teuton)\ **Post date:** [September 21, 2018, 4:14pm UTC](https://boards.straightdope.com/t/how-far-could-we-actually-go-into-the-future-using-relativity/821654/23 "2018-09-21T16:14:50Z")
To be clear, I’m not expecting the answer to be in days or months or anything, I fully expect it to be sub 1 second, but where? Half a second? A tenth? Is the current 0.02 seconds about as much as we can actually do? For the political will thing, imagine that the public’s imagination has caught onto the idea, and the Russians and the Chinese and the US are all planning to get their astronauts up into space and beating the record for national pride. How are they going to do it? Is the best way to just get something into orbit and see how fast you can orbit it, or is it better to send it off into space and come back? ---
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [September 21, 2018, 4:27pm UTC](https://boards.straightdope.com/t/how-far-could-we-actually-go-into-the-future-using-relativity/821654/24 "2018-09-21T16:27:09Z")
> [@Great\_Antibob](#): > > The biggest shift achievable in 20 years? I’d be immensely surprised if it approached even 1 second. At the moment, the best we could hope for is sending somebody into orbit for long periods of time. If Afdeyev shifted by 0.02 seconds after ~2 years in orbit, then 20 years in orbit (i.e. 10X as long) ought to shift an astronaut by 0.2 seconds. FWIW, the first module of the ISS has been in orbit for about that long. ---
**Author:** ![Great\_Antibob](https://avatars.discourse-cdn.com/v4/letter/g/e47c2d/32.png) [@Great\_Antibob](https://boards.straightdope.com/u/Great_Antibob)\ **Post date:** [September 21, 2018, 5:49pm UTC](https://boards.straightdope.com/t/how-far-could-we-actually-go-into-the-future-using-relativity/821654/25 "2018-09-21T17:49:21Z")
> [@Exapno\_Mapcase](#): > > The Parker Solar Probe will become our fastest space craft at 430,000 mph, but that’s its maximum speed at its closest to the sun and so won’t reach that speed for six years. Right. And it’s unmanned. If the idea is to accelerate a (living) human being to that type of speed, the engineering challenge is at least an order of magnitude more difficult. > [@Machine\_Elf](#): > > If Afdeyev shifted by 0.02 seconds after ~2 years in orbit, then 20 years in orbit (i.e. 10X as long) ought to shift an astronaut by 0.2 seconds. FWIW, the first module of the ISS has been in orbit for about that long. Sure, but thinking as an engineer (and not the physics “approximate a human being as a perfect sphere” type of handwaving), we aren’t going to send an astronaut up to the ISS on a 20 year long mission. Within the next 20 years, any individual sent on an ISS mission would be up there for significantly less than 20 years and would see a shift of less than 1s or even 0.2s. Pulling out the stops, at the end of 20 years we could conceivably have a manned spacecraft that’s significantly faster than any craft to date and launch it just under that window. Rather than orbit, better to launch it straight out and back. But it’s still unlikely to produce a shift of more than 1s at the end of that mission (fuel and life support supplies would be a major concern here). Let’s call 1s a reasonable upper limit. Actually, I’d think it’s less but we can postulate some kind of unforeseen technological breakthrough that let’s us go faster than we’d expect but simple enough to put into a spacecraft within a couple decades. A less hand-wavy guess? Say we could manage twice the orbital velocity of the ISS for 5 years, which is still a major engineering challenge. That gets us to 0.1s, which would be a more realistic upper limit though still probably not possible. That said, I still find the philosophical and theoretical discussion interesting, and exploring the limits of what we could conceivably do outside realistic time and resource constraints is worthwhile. ---
**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\ **Post date:** [September 21, 2018, 7:49pm UTC](https://boards.straightdope.com/t/how-far-could-we-actually-go-into-the-future-using-relativity/821654/26 "2018-09-21T19:49:52Z")
> [@Teuton](#): > > To be clear, I’m not expecting the answer to be in days or months or anything, I fully expect it to be sub 1 second, but where? Half a second? A tenth? Is the current 0.02 seconds about as much as we can actually do? > > For the political will thing, imagine that the public’s imagination has caught onto the idea, and the Russians and the Chinese and the US are all planning to get their astronauts up into space and beating the record for national pride. How are they going to do it? Is the best way to just get something into orbit and see how fast you can orbit it, or is it better to send it off into space and come back? Send them into the sun to die is the only plan. See how that catches the public’s imagination. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [September 21, 2018, 11:54pm UTC](https://boards.straightdope.com/t/how-far-could-we-actually-go-into-the-future-using-relativity/821654/27 "2018-09-21T23:54:54Z")
**[Moderating]** **Exapno Mapcase** , that looks a lot like being a jerk. Care to explain? ---
**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\ **Post date:** [September 22, 2018, 12:35am UTC](https://boards.straightdope.com/t/how-far-could-we-actually-go-into-the-future-using-relativity/821654/28 "2018-09-22T00:35:55Z")
> [@Chronos](#): > > **[Moderating]** > > **Exapno Mapcase** , that looks a lot like being a jerk. Care to explain? Sure. I simply pointed out the huge gap between what the public might find appealing and the physical reality that we can achieve such speeds only by sending spacecraft to the sun. A Swiftian proposal, perhaps, but jerkish? ---
**Author:** ![eburacum45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eburacum45/32/8690_2.png) [@eburacum45](https://boards.straightdope.com/u/eburacum45)\ **Post date:** [September 22, 2018, 12:24pm UTC](https://boards.straightdope.com/t/how-far-could-we-actually-go-into-the-future-using-relativity/821654/29 "2018-09-22T12:24:41Z")
> [@bob\_2](#): > > In Science Fiction, where FTL travel is pretty much a given, they usually ignore relativity altogether. It irritates me to read that our hero, who has been whizzed off planet via a convenient wormhole, can return to Earth and still find the same people they left behind. The good thing about wormholes is that you could return to the same time and place as you left, assuming you keep the wormhole open. Allowing for the passage of time in the interim, of course. [Previous page](https://boards.straightdope.com/t/how-far-could-we-actually-go-into-the-future-using-relativity/821654.md?page=1)