# OK, Let's talk about "time" **URL:** \ **Category:** In My Humble Opinion\ **Created:** [January 19, 2016, 8:25am UTC](https://boards.straightdope.com/t/ok-lets-talk-about-time/743558 "2016-01-19T08:25:16Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![DoctorDick](https://avatars.discourse-cdn.com/v4/letter/d/41988e/32.png) [@DoctorDick](https://boards.straightdope.com/u/DoctorDick)\ **Post date:** [January 19, 2016, 8:25am UTC](https://boards.straightdope.com/t/ok-lets-talk-about-time/743558/1 "2016-01-19T08:25:16Z")
Professional scientists define time via the assertion that “time is what clocks measure”. History, on the other hand, defines time via the concept “if two entities exist at the same time and place, they can interact”. What bothers me is that the two definitions are entirely contradictory; i.e., there exists no collection of clocks which will display exactly the same time for the relevant interactions of interest to humanity! If you look at the “scientific” definition of time, it has already been shown that an official clock (the correct time by definition) will run at a different rate if it is raised or lowered in a gravitational field. If that is correct, how can a specific time for any interaction be quoted? Different people approaching the meeting via different paths can not possibly know the correct time of their meeting via the “scientific” definition! Give me a good answer to that question and I will salute you! ---
**Author:** ![Idle\_Thoughts](https://avatars.discourse-cdn.com/v4/letter/i/838e76/32.png) [@Idle\_Thoughts](https://boards.straightdope.com/u/Idle_Thoughts)\ **Post date:** [January 19, 2016, 8:30am UTC](https://boards.straightdope.com/t/ok-lets-talk-about-time/743558/2 "2016-01-19T08:30:54Z")
I’m going to move this to IMHO. I was thinking of moving it to GQ, but not sure it has a factual answer other than just guesses. ---
**Author:** ![Rigamarole](https://avatars.discourse-cdn.com/v4/letter/r/77aa72/32.png) [@Rigamarole](https://boards.straightdope.com/u/Rigamarole)\ **Post date:** [January 19, 2016, 8:37am UTC](https://boards.straightdope.com/t/ok-lets-talk-about-time/743558/3 "2016-01-19T08:37:37Z")
> [@DoctorDick](#): > > If you look at the “scientific” definition of time, it has already been shown that an official clock (the correct time by definition) will run at a different rate if it is raised or lowered in a gravitational field. Of course we know that time is not a constant but a relative dimension. It feels pretty consistent to us only because we move so darn slow. But the only “real” definition of time is distance divided by speed, with the speed of light being the only constant. ---
**Author:** ![DoctorDick](https://avatars.discourse-cdn.com/v4/letter/d/41988e/32.png) [@DoctorDick](https://boards.straightdope.com/u/DoctorDick)\ **Post date:** [January 19, 2016, 8:50am UTC](https://boards.straightdope.com/t/ok-lets-talk-about-time/743558/4 "2016-01-19T08:50:54Z")
We should just “guess” about the definition of time? All I am asserting is that we need a well thought out definition of time. I have one if you are interested! I define time as a reference number associated with interactions. These “reference numbers” refer to specific fact which we believe to be true ; i.e., an event we have experienced. I define “the past” to be that collection of events we have experienced. I define “the future” to be events we have not yet experienced. And, lastly, I define “the present” to a new event to be assigned to “the past”. I further define the universe to be represented by a “four dimensions” coordinate system (x,y,z,t) which is capable of displaying the knowledge we have acquired. Note that this system essentially yields two different times to every event: one is the time assigned by our supposed understanding of the universe and a second being the time assigned by our becoming aware of the specific event. If that is totally beyond your comprehension, don’t bother to answer this post. Have fun – Dick ---
**Author:** ![DoctorDick](https://avatars.discourse-cdn.com/v4/letter/d/41988e/32.png) [@DoctorDick](https://boards.straightdope.com/u/DoctorDick)\ **Post date:** [January 19, 2016, 8:54am UTC](https://boards.straightdope.com/t/ok-lets-talk-about-time/743558/5 "2016-01-19T08:54:38Z")
> [@Rigamarole](#): > > Of course we know that time is not a constant but a relative dimension. It feels pretty consistent to us only because we move so darn slow. But the only “real” definition of time is distance divided by speed, with the speed of light being the only constant. That does not qualify as a “definition”. ---
**Author:** ![Rigamarole](https://avatars.discourse-cdn.com/v4/letter/r/77aa72/32.png) [@Rigamarole](https://boards.straightdope.com/u/Rigamarole)\ **Post date:** [January 19, 2016, 9:30am UTC](https://boards.straightdope.com/t/ok-lets-talk-about-time/743558/6 "2016-01-19T09:30:33Z")
> [@DoctorDick](#): > > That does not qualify as a “definition”. Why not? It’s exactly what time is. When light has traveled 299,792,458 meters relative to a given observer, then the observer has experienced 1 second of time. It will vary from one observer relative to another depending on the observer’s own speed, so there is technically no universal experience of time. ---
**Author:** ![ticker](https://avatars.discourse-cdn.com/v4/letter/t/d07c76/32.png) [@ticker](https://boards.straightdope.com/u/ticker)\ **Post date:** [January 19, 2016, 11:10am UTC](https://boards.straightdope.com/t/ok-lets-talk-about-time/743558/7 "2016-01-19T11:10:35Z")
Time is not an invariant quantity because two physicists (let’s call then Leonard and Sheldon) who leave home together and, due to some domestic argument, travel in to the university separately, will not be able to agree on what time has elapsed when they meet again over lunch. This is a relativistic affect caused by the bus Sheldon took being somewhat slower than Leonard’s car. Neither will they be able to agree on the distance back to the apartment as space is also not an invariant. However, as they can agree that they are both currently in the same place, there must be _some_ invariant quantity. That quantity is called **Spacetime**. Being good physicists both can agree on how far they have travelled in spacetime, it is just a shame they could not agree on what brand of OJ to buy. ---
**Author:** ![WordMan](https://avatars.discourse-cdn.com/v4/letter/w/e8c25b/32.png) [@WordMan](https://boards.straightdope.com/u/WordMan)\ **Post date:** [January 19, 2016, 12:19pm UTC](https://boards.straightdope.com/t/ok-lets-talk-about-time/743558/8 "2016-01-19T12:19:50Z")
> [@DoctorDick](#): > > If that is totally beyond your comprehension, don’t bother to answer this post. > > Have fun – Dick “Dick” is right - this is how you engage people you are looking for input from? I have some thoughts on the OP, but will pass on participating. ---
**Author:** ![jtur88](https://avatars.discourse-cdn.com/v4/letter/j/e9c0ed/32.png) [@jtur88](https://boards.straightdope.com/u/jtur88)\ **Post date:** [January 19, 2016, 3:05pm UTC](https://boards.straightdope.com/t/ok-lets-talk-about-time/743558/9 "2016-01-19T15:05:37Z")
The difficulty is not scientific, but linguistic. Our language fails to give us words that have distinct enough meanings to talk about it unambiguously. Space is defined as the relationship of objects at different positions. Time is the relationship of events at different , well, times. Sadly, we have two words for ‘space’ and ‘position’. But our language fails to deliver two different words for ‘time’ and ‘time’ in those separate contexts. So, although we fully understand the difference, we have no vocabulary to unambiguously say the we understand it. ---
**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:** [January 19, 2016, 3:09pm UTC](https://boards.straightdope.com/t/ok-lets-talk-about-time/743558/10 "2016-01-19T15:09:14Z")
If it is necessary to schedule an event with such precision that different attendees might arrive at different times due to relativistic effects, then one would simply specify the frame of reference of the official clock used to set the time for the meeting to start. All attendees could then compare the clock’s frame of reference to their own and make the appropriate calculations. Just because different observers read different times on their clocks, doesn’t mean that they can’t calculate what others will observe. ---
**Author:** ![raventhief](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/raventhief/32/4_2.png) [@raventhief](https://boards.straightdope.com/u/raventhief)\ **Post date:** [January 19, 2016, 3:18pm UTC](https://boards.straightdope.com/t/ok-lets-talk-about-time/743558/11 "2016-01-19T15:18:30Z")
> [@DoctorDick](#): > > \*\*Professional scientists define time via the assertion that “time is what clocks measure”. \*\*History, on the other hand, defines time via the concept “if two entities exist at the same time and place, they can interact”. What bothers me is that the two definitions are entirely contradictory; i.e., there exists no collection of clocks which will display exactly the same time for the relevant interactions of interest to humanity! > > If you look at the “scientific” definition of time, it has already been shown that an official clock (the correct time by definition) will run at a different rate if it is raised or lowered in a gravitational field. If that is correct, how can a specific time for any interaction be quoted? Different people approaching the meeting via different paths can not possibly know the correct time of their meeting via the “scientific” definition! > > Give me a good answer to that question and I will salute you! Is that really the way “professional scientists” define time? Seems rather unscientific. ---
**Author:** ![The\_Other\_Waldo\_Pepper](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/the_other_waldo_pepper/32/12370_2.png) [@The\_Other\_Waldo\_Pepper](https://boards.straightdope.com/u/The_Other_Waldo_Pepper)\ **Post date:** [January 19, 2016, 3:23pm UTC](https://boards.straightdope.com/t/ok-lets-talk-about-time/743558/12 "2016-01-19T15:23:02Z")
> [@DoctorDick](#): > > I define “the past” to be that collection of events we have experienced. I define “the future” to be events we have not yet experienced. Who is “we” in that formulation? If I say _“in the past, before pterodactyls went extinct”_ – did we experience that, or was it not the past? If someone talks about what happened during the early days of the solar system, is it the past or isn’t it? ---
**Author:** ![Dewey\_Finn](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dewey_finn/32/4222_2.png) [@Dewey\_Finn](https://boards.straightdope.com/u/Dewey_Finn)\ **Post date:** [January 19, 2016, 3:23pm UTC](https://boards.straightdope.com/t/ok-lets-talk-about-time/743558/13 "2016-01-19T15:23:07Z")
> [@raventhief](#): > > Is that really the way “professional scientists” define time? Seems rather unscientific. The OP’s “About Me” age says that he/she has a PhD in theoretical physics, so presumably he/she knows how professional scientists define time. (And given that level of education, why he he/she asking us?) ---
**Author:** ![zoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/zoid/32/336_2.png) [@zoid](https://boards.straightdope.com/u/zoid)\ **Post date:** [January 19, 2016, 4:27pm UTC](https://boards.straightdope.com/t/ok-lets-talk-about-time/743558/14 "2016-01-19T16:27:16Z")
> [@Dewey\_Finn](#): > > The OP’s “About Me” age says that he/she has a PhD in theoretical physics, so presumably he/she knows how professional scientists define time. (And given that level of education, why he he/she asking us?) From where, Wassamatta U? ---
**Author:** ![pool](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pool/32/4152_2.png) [@pool](https://boards.straightdope.com/u/pool)\ **Post date:** [January 19, 2016, 4:44pm UTC](https://boards.straightdope.com/t/ok-lets-talk-about-time/743558/15 "2016-01-19T16:44:12Z")
Tangentially related maybe but maybe someone can answer this for me as I know nothing of physics or relativity. Is the speed of light constant? I thought Einstein’s theory had something about the gravity say from the sun affecting photons or maybe it’s just that they bend? ---
**Author:** ![Smeghead](https://avatars.discourse-cdn.com/v4/letter/s/f1d935/32.png) [@Smeghead](https://boards.straightdope.com/u/Smeghead)\ **Post date:** [January 19, 2016, 4:49pm UTC](https://boards.straightdope.com/t/ok-lets-talk-about-time/743558/16 "2016-01-19T16:49:18Z")
> [@Dewey\_Finn](#): > > The OP’s “About Me” age says that he/she has a PhD in theoretical physics, Well, if it’s on the internet… ---
**Author:** ![billfish678](https://avatars.discourse-cdn.com/v4/letter/b/7bcc69/32.png) [@billfish678](https://boards.straightdope.com/u/billfish678)\ **Post date:** [January 19, 2016, 5:02pm UTC](https://boards.straightdope.com/t/ok-lets-talk-about-time/743558/17 "2016-01-19T17:02:41Z")
> [@Dewey\_Finn](#): > > The OP’s “About Me” age says that he/she has a PhD in theoretical physics, so presumably he/she knows how professional scientists define time. (And given that level of education, why he he/she asking us?) Maybe they meant theoretical Phd in Physics. PS. I have a couple of those kind of Phds myself. ---
**Author:** ![Dewey\_Finn](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dewey_finn/32/4222_2.png) [@Dewey\_Finn](https://boards.straightdope.com/u/Dewey_Finn)\ **Post date:** [January 19, 2016, 5:14pm UTC](https://boards.straightdope.com/t/ok-lets-talk-about-time/743558/18 "2016-01-19T17:14:23Z")
> [@Smeghead](#): > > > [@Dewey\_Finn](#): > > > > The OP’s “About Me” age says that he/she has a PhD in theoretical physics, > > Well, if it’s on the internet… I know that people bullshit on the Internet (and specifically here on the SDMB) all the time, but what’s the point of completing the About Me page if you’re just putting bullshit there? ---
**Author:** ![Charlie\_Wayne](https://avatars.discourse-cdn.com/v4/letter/c/4bbf92/32.png) [@Charlie\_Wayne](https://boards.straightdope.com/u/Charlie_Wayne)\ **Post date:** [January 19, 2016, 5:20pm UTC](https://boards.straightdope.com/t/ok-lets-talk-about-time/743558/19 "2016-01-19T17:20:23Z")
> [@Dewey\_Finn](#): > > The OP’s “About Me” age says that he/she has a PhD in theoretical physics, so presumably he/she knows how professional scientists define time. (And given that level of education, why he he/she asking us?) Very nicely done, Dewey. It seems to me that despite what Einstein has said, it may well be possible to travel at speeds faster than light. As I understand it, Einstein never said that the speed of light was an absolute and could not be exceeded. The truth would be closer to say that nothing can \*\*accelerate \*\*past the speed of light because as something accelerates toward the speed of light it’s mass becomes infinite. By the way, I’m certainly not a PhD in anything - never mind Physics of any kind. And - if you can believe it - I am quoting a movie character named “\*\*Prot” \*\*who comes from the planet **K-PAX.** If anyone is interested, you can check that out here: > **[K-PAX (2001) ⭐ 7.4 | Drama, Mystery, Sci-Fi](https://www.imdb.com/title/tt0272152/)** > > 2h | PG-13 And … yes … I do get all my knowledge from movies. 🙂 ---
**Author:** ![Thudlow\_Boink](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/thudlow_boink/32/320_2.png) [@Thudlow\_Boink](https://boards.straightdope.com/u/Thudlow_Boink)\ **Post date:** [January 19, 2016, 5:47pm UTC](https://boards.straightdope.com/t/ok-lets-talk-about-time/743558/20 "2016-01-19T17:47:56Z")
> [@DoctorDick](#): > > Professional scientists define time via the assertion that “time is what clocks measure”. From [this page (“What Is Time?”)](http://www.pitt.edu/~jdnorton/Goodies/What_is_time/): > [@](#): > > Scientists trying to answer this question will almost invariably start by trying to deflect the question. If you ask them the question, you may first get the rather superficial quips: > > “Time is what clocks measure.” > > “Time is what stops everything happening all at once.” > > They are not real answers, but merely amusing retorts that often serve to quieten an annoying questioner. [Next page](https://boards.straightdope.com/t/ok-lets-talk-about-time/743558.md?page=2)