# Can I measure my time dilation displacement **URL:** \ **Category:** Factual Questions\ **Created:** [December 16, 2023, 4:23pm UTC](https://boards.straightdope.com/t/can-i-measure-my-time-dilation-displacement/994696 "2023-12-16T16:23:56Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![Crane](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crane/32/3495_2.png) [@Crane](https://boards.straightdope.com/u/Crane)\ **Post date:** [December 16, 2023, 6:10pm UTC](https://boards.straightdope.com/t/can-i-measure-my-time-dilation-displacement/994696/21 "2023-12-16T18:10:36Z")
Yes, I asked how we can now measure the difference between us. ---
**Author:** ![Crane](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crane/32/3495_2.png) [@Crane](https://boards.straightdope.com/u/Crane)\ **Post date:** [December 16, 2023, 6:11pm UTC](https://boards.straightdope.com/t/can-i-measure-my-time-dilation-displacement/994696/22 "2023-12-16T18:11:53Z")
> [@Whack-a-Mole](#): > > cosmonaut who had been in space for six months was 2-seconds off from those on earth Wow, that’s measurable. Could have produced an echo. ---
**Author:** ![Little\_Nemo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/little_nemo/32/3120_2.png) [@Little\_Nemo](https://boards.straightdope.com/u/Little_Nemo)\ **Post date:** [December 16, 2023, 6:12pm UTC](https://boards.straightdope.com/t/can-i-measure-my-time-dilation-displacement/994696/23 "2023-12-16T18:12:42Z")
> [@Crane](#): > > Right, so is there a way that I can measure the time dilation between me and my great grand daughter. Yes, but you can’t do it retroactively. You and your great grand daughter need to have two very accurate clocks. Then synchronize them so they’re on the exact same time. Now you can take a 500 mph flight while carrying one of the clocks. When you reunite with your great grand daughter, you will find that your two clocks are no longer synchronized. Your clock will show that less time has passed than her clock shows. ---
**Author:** ![bob\_2](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bob_2/32/3341_2.png) [@bob\_2](https://boards.straightdope.com/u/bob_2)\ **Post date:** [December 16, 2023, 6:13pm UTC](https://boards.straightdope.com/t/can-i-measure-my-time-dilation-displacement/994696/24 "2023-12-16T18:13:22Z")
> [@Crane](#): > > Yes, I asked how we can now measure the difference between us. I think that question has been answered. You can calculate the difference, but not measure it. ---
**Author:** ![Crane](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crane/32/3495_2.png) [@Crane](https://boards.straightdope.com/u/Crane)\ **Post date:** [December 16, 2023, 6:15pm UTC](https://boards.straightdope.com/t/can-i-measure-my-time-dilation-displacement/994696/25 "2023-12-16T18:15:16Z")
Where does that appear in the equation? What term specifies starting point. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [December 16, 2023, 6:15pm UTC](https://boards.straightdope.com/t/can-i-measure-my-time-dilation-displacement/994696/26 "2023-12-16T18:15:41Z")
It seems I misremembered. I did not find the cosmonaut story I mentioned but I found a report from someone who spent 520 days on the ISS and the time dilation was a LOT less than 2-seconds (but measurable…or, at least, can be calculated): > It really is all relative: Former NASA astronaut Scott Kelly’s historic [one-year mission](https://www.space.com/tag/one-year-mission) aboard the International Space Station (ISS) made his identical twin Mark an even older brother. > > The unprecedented jaunt, which [ended this past March](https://www.youtube.com/user/VideoFromSpace), brought Scott Kelly’s total time in orbit to 520 days — all of which he spent zooming around Earth at 17,500 mph (28,160 km/h). > > \< snip \> > > “So, where[as] I used to be just 6 minutes older, now I am 6 minutes and 5 milliseconds older,” Mark Kelly said Tuesday (July 12) during a panel discussion at the ISS Research & Development 2016 conference in San Diego. Scott Kelly also participated in the panel, which was moderated by CNN TV personality Sanjay Gupta and webcast live. “Now I’ve got that over his head.” - [SOURCE](https://www.space.com/33411-astronaut-scott-kelly-relativity-twin-brother-ages.html) This would suggest your time dilation, while there, is minuscule. I suppose it could be calculated but even that is difficult since you are both further away from the earth while flying (which matters for this) as well as moving but not always at a constant speed or altitude (ascend and descend). For comparison, the astronaut traveled 218,400,000 miles compared to your million…and was a lot higher up. ---
**Author:** ![Crane](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crane/32/3495_2.png) [@Crane](https://boards.straightdope.com/u/Crane)\ **Post date:** [December 16, 2023, 6:16pm UTC](https://boards.straightdope.com/t/can-i-measure-my-time-dilation-displacement/994696/27 "2023-12-16T18:16:24Z")
So it is not real, just theoretical? ---
**Author:** ![Little\_Nemo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/little_nemo/32/3120_2.png) [@Little\_Nemo](https://boards.straightdope.com/u/Little_Nemo)\ **Post date:** [December 16, 2023, 6:17pm UTC](https://boards.straightdope.com/t/can-i-measure-my-time-dilation-displacement/994696/28 "2023-12-16T18:17:47Z")
> [@Crane](#): > > Where does that appear in the equation? What term specifies starting point. You can start at any point you want as long as you both use the same starting point. ---
**Author:** ![Crane](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crane/32/3495_2.png) [@Crane](https://boards.straightdope.com/u/Crane)\ **Post date:** [December 16, 2023, 6:19pm UTC](https://boards.straightdope.com/t/can-i-measure-my-time-dilation-displacement/994696/29 "2023-12-16T18:19:44Z")
Then the effect would not apply to the astronauts because most of what they would view on earth would have a different starting point. ---
**Author:** ![DPRK](https://avatars.discourse-cdn.com/v4/letter/d/4491bb/32.png) [@DPRK](https://boards.straightdope.com/u/DPRK)\ **Post date:** [December 16, 2023, 6:21pm UTC](https://boards.straightdope.com/t/can-i-measure-my-time-dilation-displacement/994696/30 "2023-12-16T18:21:26Z")
Remember this video game? [http://gamelab.mit.edu/games/a-slower-speed-of-light/](http://gamelab.mit.edu/games/a-slower-speed-of-light/) > **[GitHub - vm6502q/OpenRelativity: An open source framework to add the effects...](https://github.com/vm6502q/OpenRelativity)** > > An open source framework to add the effects of traveling at relativistic speeds to visualizations or games - GitHub - vm6502q/OpenRelativity: An open source framework to add the effects of travelin... You see weird shit _when you are moving close to the speed of light,_ but not after you slow back down. ---
**Author:** ![Crane](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crane/32/3495_2.png) [@Crane](https://boards.straightdope.com/u/Crane)\ **Post date:** [December 16, 2023, 6:28pm UTC](https://boards.straightdope.com/t/can-i-measure-my-time-dilation-displacement/994696/31 "2023-12-16T18:28:08Z")
It seems that me A and the kid B should be able to observe a reference and react in a way that would be measurable. Like using the oscilloscopes to align a waveform to a fixed reference and get a result that is 2microseconds displaced. ---
**Author:** ![Little\_Nemo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/little_nemo/32/3120_2.png) [@Little\_Nemo](https://boards.straightdope.com/u/Little_Nemo)\ **Post date:** [December 16, 2023, 6:28pm UTC](https://boards.straightdope.com/t/can-i-measure-my-time-dilation-displacement/994696/32 "2023-12-16T18:28:19Z")
> [@Crane](#): > > Then the effect would not apply to the astronauts because most of what they would view on earth would have a different starting point. I have no idea what you’re saying here. Are you sure you understand the concept here? It’s not that people look like they’re in the past or in the future when you’re traveling at high speeds. There’s no echo effect. What happens is that when you move really fast, it causes time to slow down. But to anyone’s perception everything appears to be happening in the present. If you’re flying 17000 mph in a space station and you talk to your great grand daughter on the phone while she’s on the ground, neither of you will notice any time effects. She’s not talking to you from your past and you’re not talking to her from her future. The only effect is that she would think you are doing things a little slower and you would think she’s doing things a little faster. (And the effect is extremely little so neither of you would notice it with your senses.) ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [December 16, 2023, 6:28pm UTC](https://boards.straightdope.com/t/can-i-measure-my-time-dilation-displacement/994696/33 "2023-12-16T18:28:58Z")
> [@Whack-a-Mole](#): > > For comparison, the astronaut traveled 218,400,000 miles compared to your million…and was a lot higher up. If we extrapolate your million miles to the astronaut then you are 0.09 milliseconds younger than you would have been if you stayed on earth and not flown. There are a lot of confounding factors but I think that is a good ballpark. Not sure we can do much better. (someone please check my math…not my strongest subject) ---
**Author:** ![Crane](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crane/32/3495_2.png) [@Crane](https://boards.straightdope.com/u/Crane)\ **Post date:** [December 16, 2023, 6:33pm UTC](https://boards.straightdope.com/t/can-i-measure-my-time-dilation-displacement/994696/34 "2023-12-16T18:33:47Z")
Yeah, that’s 9 microseconds but close enough. So, relative to some of the objections above, is my age an absolute that is independent of the time on earth or am I displaced relative to earth time. ---
**Author:** ![md-2000](https://avatars.discourse-cdn.com/v4/letter/m/9d8465/32.png) [@md-2000](https://boards.straightdope.com/u/md-2000)\ **Post date:** [December 16, 2023, 6:35pm UTC](https://boards.straightdope.com/t/can-i-measure-my-time-dilation-displacement/994696/35 "2023-12-16T18:35:45Z")
> [@Little\_Nemo](#): > > > [@Crane](#): > > > > Where does that appear in the equation? What term specifies starting point. > > You can start at any point you want as long as you both use the same starting point. Actually, starting with the same frame of reference - i.e. not moving wrt each other. So yes, you are 2 µs younger than you would be if you’d not gone on that trip. If you’d gone on a jaunt to Alpha Centauri and back at 0.9c then the difference would be obvious, without a fancy pair of chronometers to show the difference - your friends would be planted and your great-grad-daughter would be married… As it is, and as you see with the example of the astronaut - time ran slower for the travelling person, but so small it’s not noticeable. As others have been saying - you would only tell the difference in such a miniscule difference if you’d taken a precise clock, or from something else where a 2µs difference was noticeable. ---
**Author:** ![DPRK](https://avatars.discourse-cdn.com/v4/letter/d/4491bb/32.png) [@DPRK](https://boards.straightdope.com/u/DPRK)\ **Post date:** [December 16, 2023, 6:37pm UTC](https://boards.straightdope.com/t/can-i-measure-my-time-dilation-displacement/994696/36 "2023-12-16T18:37:17Z")
> [@Whack-a-Mole](#): > > Or, earlier, the [Pound–Rebka experiment](https://en.wikipedia.org/wiki/Gravitational_time_dilation) where they measured the difference between clocks at the top and bottom of a tower. > > Cheaper than taking a plane. > [@Whack-a-Mole](#): > > the astronaut… was a lot higher up. Being higher up makes a clock tick faster, not slower. That is a related but sort of separate effect. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [December 16, 2023, 6:39pm UTC](https://boards.straightdope.com/t/can-i-measure-my-time-dilation-displacement/994696/37 "2023-12-16T18:39:32Z")
> [@md-2000](#): > > So yes, you are 2 µs younger than you would be if you’d not gone on that trip. I That’s the whole story right there. If you had owned two nearly perfect clocks before you began flying, and had taken one with you and left one on the mantle at home, then by now there’d be a visible 2 microsecond difference between them. But there is nothing you can do now to retroactively get the two clocks, synchronize them back then, then go travel, so you can look at them now and see the difference. ETA: Looking at the posts below I think I see the confusion. @Crane, there is no sense in which you’re “desynchronized” from the rest of the world, running two microseconds behind. There’s no existing signal or source you can look at now and have the perception that although a child sees it as e.g. 10am exactly, you see it as 10am minus 2 microseconds. That is simply not the situation. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [December 16, 2023, 6:39pm UTC](https://boards.straightdope.com/t/can-i-measure-my-time-dilation-displacement/994696/38 "2023-12-16T18:39:48Z")
You are just a tiny bit younger than you would be if you had never flown. If you have a million hours to live in your life you will still have a million hours to live. You’ll just die a few microseconds after someone else your exact age who also had a million hours to live. ETA: But to you, you will also have lived the exact million hours same as the other guy. You will not get any “extra” life from doing this. ---
**Author:** ![Crane](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crane/32/3495_2.png) [@Crane](https://boards.straightdope.com/u/Crane)\ **Post date:** [December 16, 2023, 6:40pm UTC](https://boards.straightdope.com/t/can-i-measure-my-time-dilation-displacement/994696/39 "2023-12-16T18:40:05Z")
Yes, and 2 microseconds is easily measurable with an oscilloscope. We just have to do something measurable in the time domain. As I proposed by aligning an electronic signal with a common reference. ---
**Author:** ![DPRK](https://avatars.discourse-cdn.com/v4/letter/d/4491bb/32.png) [@DPRK](https://boards.straightdope.com/u/DPRK)\ **Post date:** [December 16, 2023, 6:43pm UTC](https://boards.straightdope.com/t/can-i-measure-my-time-dilation-displacement/994696/40 "2023-12-16T18:43:00Z")
> [@Crane](#): > > So, relative to some of the objections above, is my age an absolute that is independent of the time on earth or am I displaced relative to earth time. You really want to get into how tricky it is to define “earth time” when pushing a clock across the room or taking it one floor up the elevator warps the time? Anyway, if you had a clock strapped to your wrist then it would count _your_ age, even if you went to live on Mars or Alpha Centauri and/or came back afterwards. [Previous page](https://boards.straightdope.com/t/can-i-measure-my-time-dilation-displacement/994696.md?page=1) [Next page](https://boards.straightdope.com/t/can-i-measure-my-time-dilation-displacement/994696.md?page=3)