You are not logged in.
This topic is about time.
It is inspired by the vigorous arguments by Spaniard, who arrived in early 2025 with a passionate support of "scientific" time.
There was a brief moment of confusion, as members of the forum grappled with the difference between time at the scale of planets, and time at the scale of atoms.
All of this is happening within the context of General Relativity, which teaches that time slows as gravity increases or velocity increases with respect to the speed of light.
I decided to ask Google's search assistant to consider the question. I hope this analysis will stimulate discussion that sheds light and avoids creating further confusion.
Update: 2025/02/24 - An ideal application for "scientific" time is "Ship's Time". Every vessel traveling away from Earth must maintain it's own time, and that time will be independent of Earth or any other planet. "Scientific time" is perfect for time keeping on such vessels, and in any habitat away from Earth not tied to a planetary body.
Conversation with Gemini
Hi Gemini! Thank you for all your assistance with a great variety of questions. On this occasion, I am hoping to provide some useful information to a (very small) audience. The question is about the history of the word "second" as a measure of time. I am guessing there is a relationship to the nautical compass, but even there I am unsure of the history of the term minute. Do you have anything in your collection about these terms?It's fascinating to trace the history of these time measurements! Here's a breakdown of the etymological journey of "minute" and "second":
The Foundation: Sexagesimal System:
The roots go back to the ancient Babylonians, who used a base-60 (sexagesimal) number system. This system influenced how we divide circles and, later, time.
"Minute": Pars Minuta Prima:The word "minute" originates from the Latin phrase "pars minuta prima," meaning "first small part." This referred to the first division of an hour into 60 parts.
"Second": Pars Minuta Secunda:Similarly, "second" comes from the Latin "pars minuta secunda," meaning "second small part." This signifies the second division, where each minute is further divided into 60 parts.
Connection to Astronomy:These terms were also used in astronomy to divide degrees of arcs. So, you'd have minutes and seconds of arc, reflecting the same division principle.
Claudius Ptolemy's "Almagest" is a key historical text where these divisions were discussed.
Evolution of Timekeeping:While the concept of these divisions existed for a long time, accurately measuring seconds became possible with the development of precise mechanical clocks, particularly in the 16th and 17th centuries.
The development of atomic clocks in the mid 20th century allowed for even greater precision in defining the second.
In essence, the terms reflect a historical system of dividing quantities into smaller and smaller parts, originating from ancient mathematical practices. While there is a connection to the division of arcs, and therefore a connection to things such as nautical navigation, the primary root is from the latin phrases describing the "first small part" and the "second small part" of a whole.With this background, please consider the question: Is a second on a rotating planet such as the Earth properly defined as a part of the daily rotation of the object, divided into 24 hours which are divided into 60 minutes which are divided into 60 seconds. It appears that there are some humans who might wish to define an arbitrary length of time as a 'second'
You've touched upon a very important point about the evolution of timekeeping! Here's a clarification:
Historical Definition:
Historically, the second was indeed tied to the Earth's rotation, defined as 1/86,400 of a mean solar day.
However, the Earth's rotation is not perfectly consistent. It varies slightly, which made this definition inadequate for precise scientific measurements.
Modern Definition:To address this, the second is now defined based on the properties of atoms. Specifically, it's defined as:
"the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom."This atomic definition provides a much more stable and precise standard.
Why the Change?The need for extremely accurate timekeeping in fields like navigation (GPS), telecommunications, and scientific research drove the shift to an atomic definition.
Therefore, while the historical concept of the second is rooted in the Earth's rotation, the modern, official definition is not.
Arbitrary Definitions:It is true that anyone could make up an arbitrary definition of a second. However, for scientific and technological systems to work together, they must all use the same, standardized definition. This is why the atomic definition is so important.
In summary, while the concept originated from the Earth's rotation, the modern "second" is an atomic measurement.So now we arrive at the heart of the matter. Mars has it's own unique second, and for convenience, astronomers have deferred to the majesty of Mars, to accept it's second as 1/86400 th of the daily rotation (a Sol). Can you find any evidence that the humanly defined atomic "second" is at all useful on Mars? It would appear to me to be wildly inappropriate.
You've highlighted a very important distinction between fundamental scientific definitions and practical, localized applications. Here's a breakdown of how timekeeping works on Mars, and why the atomic second, while fundamental, isn't the primary practical unit:
Key Points:
The "Sol":
On Mars, the "sol" is the primary unit of a day. It's the length of a Martian solar day, which is slightly longer than an Earth day.
For practical purposes, especially for mission operations, it's far more useful to use the sol as the basis for daily activities.
Martian Timekeeping:Scientists working on Mars missions often use a "Martian clock" that is adjusted to the length of a sol. This means that their hours, minutes, and seconds are slightly longer than Earth's.
This is essential for coordinating activities with the Martian day/night cycle.
The Atomic Second's Role:The atomic second, as defined by the caesium-133 atom, remains the international standard unit of time. It's crucial for precise scientific measurements, including:
Navigation: Spacecraft navigation relies on extremely accurate timekeeping.
Communication: Precise timing is essential for transmitting and receiving data.
Scientific research: Many experiments require extremely accurate time measurements.
Therefore, even on mars, when very precise measurements are required, the atomic second is still the base measurement.
Practical vs. Fundamental:While the atomic second is fundamental, it's not always the most practical unit for everyday use.
Just as we use local time zones on Earth, scientists on Mars use a timekeeping system that's tailored to the Martian day.
In essence:The atomic second is the bedrock of precise time measurement, used in critical scientific and technological applications on Mars.
However, for daily operations and to align with the Martian environment, the "sol" and adjusted Martian time are used.Therefore, you are correct in that for the practical application of everyday time keeping on Mars, that using a second derived from the sol, is far more practical than using the earth based atomic second.
Nicely summarized! Thank you!
You're very welcome! I'm glad I could help
(th)
Offline
Like button can go here
This post is reserved for an index to posts that may be contributed by NewMars members over time.
It will help if members will write a one line summary of what the post is about, after re-reading the post to see what it ended up being about.
(th)
Offline
Like button can go here
This post is offered in appreciation of Spaniard's support of "scientific" time measurement.
While "scientific" time is inappropriate for use with rotating masses the size of planets, it ** is ** the perfect solution for humans traveling in space ships, or living in rotating habitats in space.
What I like about the use of the Cesium atom to count increments of time is that it will faithfully adjust to relativistic effects as vessels approach the speeds at which those effects become noticeable.
The time that is counted using the "scientific" method may well become known as "Ship's" time.
Obviously, the time on each vessel or in each habitat will differ from every other ship or habitat, since all will be operating with different velocities and in different gravitational fields.
The day may come when Earth will broadcast a time signal the way Big Ben in London broadcasts the local time. The Earth time will only be meaningful in the context of communications with Earth of course. It will have no significance for humans living elsewhere.
(th)
Offline
Like button can go here
Because Spaniard made a strong argument for "scientific" time (as compared to planetary time), I've been on the watch for news about scientific time. The article at the link below reports on NASA advances in time keeping in space.
https://www.jpl.nasa.gov/news/working-o … s-mission/
The article reports on the successful test of a Deep Space Atomic clock, and the upcoming Clock-2 that will fly to Venus in 2028 (if all goes well).
Built by NASA’s Jet Propulsion Laboratory in Southern California, the Deep Space Atomic Clock is an ultra-precise, mercury-ion atomic clock encased in a small box that measures about 10 inches (25 centimeters) on each side – roughly the size of a toaster. Designed to survive the rigors of launch and the cold, high-radiation environment of space without its timekeeping performance degrading, the Deep Space Atomic Clock was a technology demonstration intended to carry out technological firsts and fill critical knowledge gaps.
The NASA clock was reported to be 10 times more accurate that GPS clocks. GPS clocks (apparently) have to be updated twice a day from a master clock on Earth. A space probe far from Earth will need to keep it's own time accurately.
I am reminded of the challenges of accurate time keeping on ships at sea on Earth, and reports of shipwreck due to incorrect time keeping by early clocks. Apparently accurate time keeping for celestial navigation is even more important. The article gives examples.
(th)
Offline
Like button can go here
There is sideral vs solar time right here on Earth, both measured in standard (scientific) seconds, now defined in terms of some physical phenomenon.
Solar time is from noon to noon, 24 standard hours, each 60 standard minutes long, and each of those 60 standard (scientific) seconds long. But the Earth moves in its orbit during that interval, turning through slightly more than 360 degrees, with a finite angle between the two radials from sun to Earth, at noon one day vs noon the next.
Sidereal time is the interval required for the Earth to turn exactly 360 degrees, which is one revolution relative to the "fixed" stars. That is 23 hours, 56 minutes, in terms of the very same standard (scientific) hours and minutes. I don't know it to the nearest standard (scientific) second.
So, the day length on Earth is not simple number, even using standard (scientific) time. Depends upon whether you define a "day" as noon to noon, or as 360 degrees rotation.
GW
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
Offline
Like button can go here
The article at the link below is about the interesting idea that time itself may be quantized.
https://interestingengineering.com/scie … heory-link
My interpretation of the report is that while the concept is interesting, it has not been developed far enough so that it can be tested.
it does appear to have promise in the never-ending challenge of merging relativity to quantum mechanics, but my interpretation of the report is that "we aren't there yet".
Looking out a ways, it crossed my mind to wonder what that quantum time increment might be, or if it is relative as so much else in the Universe appears to be.
(th)
Offline
Like button can go here