3 ms·

> Time is one of the few physical things that are objective and real […] Don't look too closely at it, as things can get squirrelly the deeper you dig: * http

> Time is one of the few physical things that are objective and real […] Don't look too closely at it, as things can get squirrelly the deeper you dig: * https://en.wikipedia.org/wiki/The_Order_of_Time_(book) https://en.wikipedia.org/wiki/The_Order_of_Time_(book) * https://en.wikipedia.org/wiki/Carlo_Rovelli https://en.wikipedia.org/wiki/Carlo_Rovelli Edit: For those downvoting, you may wish to look up the question "Does time exist?": * https://www.theguardian.com/books/2018/apr/14/carlo-rovelli-exploding-commonsense-notions-order-of-time-interview https://www.theguardian.com/books/2018/apr/14/carlo-rovelli-... * https://www.cbc.ca/player/play/1888683587729 https://www.cbc.ca/player/play/1888683587729 Calling it "objective and real" is… debatable. Certainly the "objective" part, as Einstein theorized and empirical observation has shown.

tgv 5y ago
Time may not be absolute, but calling gravity subjective is safer (after all, the arrow of time seems to be very much part of nature). However, I bet you still feel squeamish about jumping from anything higher than a meter.
- throw0101a 5y ago
  > (after all, the arrow of time seems to be very much part of nature) Rovelli has much to say about the Second Law and entropy: * https://www.youtube.com/watch?v=-6rWqJhDv7M https://www.youtube.com/watch?v=-6rWqJhDv7M * https://en.wikipedia.org/wiki/The_Order_of_Time_(book) https://en.wikipedia.org/wiki/The_Order_of_Time_(book)
- bagacrap 5y ago
  how can you tell whether something is part of "nature" or just part of our nature?
civilized 5y ago
People have this strange idea that Einstein destroyed objectivity in physics and validated all their pet postmodern theories. It isn't true. In relativity, time is a variable that is different for each observer, but it is still objective. It's not a matter of opinion for each observer. There are formulas that determine how all the variables change, and any observer can know what the other observers' variables are by watching how they move through space and using the formulas. While some naive Newtonian concepts such as a single universal time metric stop working, there's no wiggle room for observer A and B to be inconsistent with one another based on their personal opinions. There is one objective reality and one objective way to quantify it mathematically. Time isn't a single universal quantity in relativity, but it's still objective. Einstein didn't turn physics into cultural anthropology.
- morelisp 5y ago
  People have this strange idea that "subjective" means something equivalent to "unknowable" or "an opinion" or "as I please". It isn't true. > a variable that is different for each observer This is literally what "subjective" means - different dependent on the subject.
  - civilized 5y ago
    Google subjective and copy the definition you see here. Here's what I see: subjective: based on or influenced by personal feelings, tastes, or opinions.
    - morelisp 5y ago
      First result is Wikipedia entry for "Subjectivity" which says... - Something being a subject, narrowly meaning an individual who possesses conscious experiences, such as perspectives, feelings, beliefs, and desires. - Something being a subject, broadly meaning an entity that has agency, meaning that it acts upon or wields power over some other entity (an object). - Some information, idea, situation, or physical thing considered true only from the perspective of a subject or subjects. The third being the only obvious applicable one. It's also hypocritical to demand an adherence to an anti-common-sense physics-based formal definition of "time" while refusing the same courtesy towards formal definitions of "subjective."
      - civilized 5y ago
        But it's not applicable, because an "observer" in relativity is not a subject having perspectives, feelings, beliefs, etc. It is an abstract mathematical point moving through space. "Reference frame" is really the proper term, not observer or subject. And the proper time that passes in a given reference frame is an objective fact in relativity, even though that measurement cannot be directly applied to other reference frames without transformation. "Objective" doesn't mean "experienced from all perspectives in the same way". Two different observers of a cube will get two different perspectives of the cube. The cube is still a single, objective, observer-independent reality. The same applies to relativistic time. It's a single reality (part of the spacetime manifold) that is measured differently in different reference frames. The different measurements must be consistent with one another according to a system of formulas. Just as different perspectives of a cube must be consistent with one another based on (1) the cube's objective existence in space and (2) the formulas of optics which determine the perspective each observer will receive. It may be helpful to think about a more mundane example. Google search results for a given search term depend on who searches, which makes them relative. But they don't depend on the feelings of the searcher and hence are not subjective.

tgv 5y ago

Time may not be absolute, but calling gravity subjective is safer (after all, the arrow of time seems to be very much part of nature). However, I bet you still feel squeamish about jumping from anything higher than a meter.

throw0101a 5y ago
> (after all, the arrow of time seems to be very much part of nature) Rovelli has much to say about the Second Law and entropy: * https://www.youtube.com/watch?v=-6rWqJhDv7M https://www.youtube.com/watch?v=-6rWqJhDv7M * https://en.wikipedia.org/wiki/The_Order_of_Time_(book) https://en.wikipedia.org/wiki/The_Order_of_Time_(book)
bagacrap 5y ago
how can you tell whether something is part of "nature" or just part of our nature?

civilized 5y ago

People have this strange idea that Einstein destroyed objectivity in physics and validated all their pet postmodern theories. It isn't true. In relativity, time is a variable that is different for each observer, but it is still objective. It's not a matter of opinion for each observer. There are formulas that determine how all the variables change, and any observer can know what the other observers' variables are by watching how they move through space and using the formulas. While some naive Newtonian concepts such as a single universal time metric stop working, there's no wiggle room for observer A and B to be inconsistent with one another based on their personal opinions. There is one objective reality and one objective way to quantify it mathematically. Time isn't a single universal quantity in relativity, but it's still objective. Einstein didn't turn physics into cultural anthropology.

morelisp 5y ago
People have this strange idea that "subjective" means something equivalent to "unknowable" or "an opinion" or "as I please". It isn't true. > a variable that is different for each observer This is literally what "subjective" means - different dependent on the subject.
- civilized 5y ago
  Google subjective and copy the definition you see here. Here's what I see: subjective: based on or influenced by personal feelings, tastes, or opinions.
  - morelisp 5y ago
    First result is Wikipedia entry for "Subjectivity" which says... - Something being a subject, narrowly meaning an individual who possesses conscious experiences, such as perspectives, feelings, beliefs, and desires. - Something being a subject, broadly meaning an entity that has agency, meaning that it acts upon or wields power over some other entity (an object). - Some information, idea, situation, or physical thing considered true only from the perspective of a subject or subjects. The third being the only obvious applicable one. It's also hypocritical to demand an adherence to an anti-common-sense physics-based formal definition of "time" while refusing the same courtesy towards formal definitions of "subjective."
    - civilized 5y ago
      But it's not applicable, because an "observer" in relativity is not a subject having perspectives, feelings, beliefs, etc. It is an abstract mathematical point moving through space. "Reference frame" is really the proper term, not observer or subject. And the proper time that passes in a given reference frame is an objective fact in relativity, even though that measurement cannot be directly applied to other reference frames without transformation. "Objective" doesn't mean "experienced from all perspectives in the same way". Two different observers of a cube will get two different perspectives of the cube. The cube is still a single, objective, observer-independent reality. The same applies to relativistic time. It's a single reality (part of the spacetime manifold) that is measured differently in different reference frames. The different measurements must be consistent with one another according to a system of formulas. Just as different perspectives of a cube must be consistent with one another based on (1) the cube's objective existence in space and (2) the formulas of optics which determine the perspective each observer will receive. It may be helpful to think about a more mundane example. Google search results for a given search term depend on who searches, which makes them relative. But they don't depend on the feelings of the searcher and hence are not subjective.