What is Years: Definition and 634 Discussions

A year is the orbital period of a planetary body, for example, the Earth, moving in its orbit around the Sun. Due to the Earth's axial tilt, the course of a year sees the passing of the seasons, marked by change in weather, the hours of daylight, and, consequently, vegetation and soil fertility. In temperate and subpolar regions around the planet, four seasons are generally recognized: spring, summer, autumn and winter. In tropical and subtropical regions, several geographical sectors do not present defined seasons; but in the seasonal tropics, the annual wet and dry seasons are recognized and tracked.
A calendar year is an approximation of the number of days of the Earth's orbital period, as counted in a given calendar. The Gregorian calendar, or modern calendar, presents its calendar year to be either a common year of 365 days or a leap year of 366 days, as do the Julian calendars; see below. For the Gregorian calendar, the average length of the calendar year (the mean year) across the complete leap cycle of 400 years is 365.2425 days. The ISO standard ISO 80000-3, Annex C, supports the symbol a (for Latin annus) to represent a year of either 365 or 366 days. In English, the abbreviations y and yr are commonly used.
In astronomy, the Julian year is a unit of time; it is defined as 365.25 days of exactly 86,400 seconds (SI base unit), totalling exactly 31,557,600 seconds in the Julian astronomical year.The word year is also used for periods loosely associated with, but not identical to, the calendar or astronomical year, such as the seasonal year, the fiscal year, the academic year, etc. Similarly, year can mean the orbital period of any planet; for example, a Martian year and a Venusian year are examples of the time a planet takes to transit one complete orbit. The term can also be used in reference to any long period or cycle, such as the Great Year.

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  1. J

    Other Math Olympiad Advice Please (I will be 13 years old next year in 9th grade)

    Hi! I am 12, and will be a 13 in 9th grade ( I skipped 6th grade). I have a curiosity for mathematics and have started preparing to take the AMC 10 and 12 exams. I enjoy solving the ingeniously crafted problems, as I share the sentiment of many math competitors of not being challenged by the...
  2. LenaWenaKena

    I'm interested in physics but have no idea what path to take (14 years old)

    How did you find PF?: Google Search I'm new to this forum and I am currently 14 years old. I've recently taken an interest in physics(Due to popular science/ books and natural curiosity). But I have no idea what path to take so I could study it. I come from a poor and quite unsupportive family...
  3. pinball1970

    Ancient Human Relative Walked Upright 7 Million Years Ago

    "The fossilized find, first uncovered two decades ago, suggests that early humans regularly walked on two feet some seven million years ago. This new analysis, published today in Nature, makes a strong case that Sahelanthropus tchadensis, a species that lived during the critical time when our...
  4. Astronuc

    RIP Lucile Randon, world's oldest person, has died at age 118 years

    Lucile Randon, known as Sister André, has died a few weeks before her 119th birthday. https://www.npr.org/2023/01/18/1149748001/world-oldest-person-sister-andre-lucile-randon-france-nun What stories she could tell!
  5. BBBOB

    Need Aid On This Problem Set (Combinations of Month Numbers in 10 Years)

    TL;DR Summary: Eight Exact To Get 49 Please advise if I am wording this problem correctly and what are the solution (is there some equation for combinations )/ Answers:SET of numbers 1,2,3,4,5,6,7,8,9,10,11,12 months of the year. Within the exact time frame of 10 years I MUST choose a number...
  6. J

    Admissions Applying to PhD programs after a few years out of academia

    So I graduated in 2019 from a smaller state university with 2 honors BAs in physics and applied math. 3.83 GPA, all A's in my 400 level classes, few years of computational research and some independent honors projects, and I was involved with tutoring, TA'ing, led the SPS chapter, etc. Didn't do...
  7. pensive in PA

    Other Should I go back to grad school for physics after 4.5 years?

    In 2017 I graduated with a B.S. in physics and went on to a physics Ph.D. program in the fall. After six months, though, because of mental health problems I left grad school on a "medical leave of absence" from which I chose not to return in fall 2018. After job-searching for a while, I settled...
  8. Astronuc

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    https://www.msn.com/en-us/weather/topstories/u-s-volcano-that-s-been-dormant-for-more-than-800-years-showing-signs-of-life/ar-AA13s3xt It's also unusual.
  9. beethovenscroissant

    Admissions Climbing my way to a Physics PhD 10 years after a Philosophy BA

    Hi all! It's been a decade since I graduated with a bachelor's in philosophy. I went to an ivy planning double major with physics, but I ultimately dropped the latter after my introductory courses and graduated with a poor GPA (2.7). To save you the sob story, I basically had no ability to cope...
  10. robphy

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    Chen-Ning Yang is (on official documents) 100 years old today [His real birthday is Oct 1, according to https://en.wikipedia.org/wiki/Yang_Chen-Ning , which says " His birth date was erroneously recorded as September 22, 1922 in his 1945 passport. He has since used this incorrect date on all...
  11. fluidistic

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    I would like to let my 6 years old son play and learn about electricity or electronics. I have searched on the Internet and what comes out are mostly kits with an arduino or a clone, which are very interesting but not exactly what I'm looking for. I have seen a kit that teaches about electricity...
  12. S

    Exploring Our Timeline: 13 Billion Years Ago and Now

    The Webb Telescope is finding images from the early beginnings of our universe, indeed from nearly 13 billion years ago. That is fascinating, but, what is happening right at this moment in our timeline, in those locations giving astronomers 13 billion year old information? I ask, because the...
  13. Trysse

    Looking for the title of a book I read years ago

    Maybe you can help. Years ago I read a book. Unfortunately I can neither remeber the name of the book nor of the author. In the Story mankind has made it to the stars with faster than light space ships.. Than they develop kind of portals that make the ships redundant. Travel by portal much...
  14. jtbell

    In the North Sea, 50 years ago

    Today, the CBS Sunday Morning news magazine had a story about the Aurora, a cruise ship built in 1955 that is now being restored as one of the last of its type. When I heard its original name, the Wappen von Hamburg, and its original service, carrying tourists between Hamburg and the island...
  15. T

    B Mars Probe gets Windows 98 Update, after 19 years

  16. dlgoff

    Over 19 Years of Learning: Thank You Physics Forums!

    I just wanted to thank Physics Forums for the education. After being a member here for almost 19 years, I've learned a lot. Thanks @Greg Bernhardt .
  17. C

    Admissions Dropped out for 5 years -- What are my chances at Grad schools?

    Hello, so i have an interesting schooling history and was wondering how that would effect my chances of getting into grad schools. i went to community college for a couple of years but due to deaths in the family and severe financial hardships i really struggled attending and eventually...
  18. Astronuc

    Hiawatha impact crater in Greenland, formed ~58 million years ago

    Huge asteroid slammed into Greenland just a few (~7-8) million years after the dinosaurs died out https://www.space.com/greenland-impact-crater-hiawatha-age Scientists from Swedish Museum of Natural History independently sampled rocks from the crater and dated them using the uranium...
  19. jedishrfu

    B An Ancient Solar Storm 9200 years ago is Cause for Concern

  20. shivajikobardan

    I wasted 3 years of my uni life on unproductive and useless things

    https://www.physicsforums.com/threads/regret-induced-jealousy-how-to-deal-with-this.1011135/#post-6586239 I made a post this few days ago but I believe this is different than that post. How do I get over this? I wasted time trying to make online income, creating blogs. I didn't realize full...
  21. T

    Does Evo Change Her Avatar Every 5 Years?

    Evo used to change her avatar about 6 times a week. She's had this one for a LONG time.
  22. fluidistic

    Parent/Child Genome Comparison: 100,000 Years Ago

    Let's say you know you are given the full genome of 2 individuals such that they are related as father/son or mother/daughter, that they both died at age 30 some 100 k years ago. Can you tell who is the parent/child by looking at their genomes only? If so, how? I picked 100 k years only because...
  23. V

    Physics Transitioning to Physics after 10+ years in software, low gpa

    Hello everyone, I am from India.I completed my Bachelors in Engineering, ECE to specific from a very average Indian college in year 2006 with many backlogs and year gaps. Since then I have been working in the IT industry.I have a undergraduate percentage of 56%, using...
  24. Astronuc

    Fossilized Footprints dating to ~23k years ago, White Sands, NM

    https://www.nps.gov/whsa/learn/nature/fossilized-footprints.htm https://phys.org/news/2021-09-fossil-footprints-humans-populated-americas.html https://www.science.org/doi/10.1126/science.abg7586 (subscription needed for full article) https://www.nature.com/articles/d41586-021-02597-1...
  25. C

    B Measuring change in g with height (TV program many years ago)

    Bit of a long shot but can anyone remember a TV program where the presenter measured the weight of something at ground level and compared it to the weight at the top of a tall building, possibly the Empire State building? Sorry I can't recall more details. Think it was at least 10 years ago...
  26. S

    I What would it take to eliminate leap years?

    I am curious as to how exactly to calculate this! The concept is that when they raised all the water up in the 3-gorges dam, it adjusted the length of a day by a very small amount. Using this principle, what would it take for us to slow the Earth's rotation down sufficiently that it rotates...
  27. N

    Form a Linear Equation for the Value of this equipment during the 10 years it will be in use

    A school district purchases a high-volume printer, copier, and scanner for $24,000. After 10 years, the equipment will have to be replaced. Its value at that time is expected to be $2000. Write a linear equation giving the value V of the equipment during the 10 years it will be in use. Let t =...
  28. CPW

    More info about natural nuclear fission going critical 2 Million years ago?

    This week I read through the chapter "Energy from the Nucleus" inside the familiar intro physics textbook Halliday, Resnick, Walker. I found it fascinating that there is evidence from a uranium mine in West Africa that there may likely have been a nuclear fission natural reactor that went...
  29. J

    Programs Is doing a PhD in Engineering Part Time in 8 Years Possible?

    Is it possible for me to get a PhD in electrical engineering while going part time, one class at a time? The college I'm thinking of going to has a 8 year time limit for PhDs before credits expire. 8 years seems like a long time. This would allow for 16 different classes, not sure if summer term...
  30. S

    I Unbihexium could have a half-life of millions of years?

    This article seems to say that the range of estimates go this high. This could be something that would actually stay around long enough to be of some use. https://www.chemistryworld.com/news/beyond-element-118-the-next-row-of-the-periodic-table/9400.article
  31. nduka-san

    What quirky tradition do astronauts have before launching into space?

    it's been 60 years since humanity entered space. What are your favorite things about space or hidden space history tidbits? mine is On the 12 April 1961, the first man in space, Yuri Gagarin asked the bus driver to stop on the route to the launchpad and urinated against the right-hand back tire...
  32. Jarvis323

    Magnetic field excursion about 41,000-42,000 years ago

    A global environmental crisis 42,000 years ago https://science.sciencemag.org/content/371/6531/811
  33. bhobba

    COVID Do People Think It Will Take 7 Years to Get Back To Normal?

    See the following: For what t is worth I think it will be less than 7 years because research is still happening at a breathtaking speed - but exactly when I have no idea. Thanks Bill
  34. S

    MHB Probability of Surviving 10 Years for A, B, and C

    The probability that at least 2 of 3 people A, B, and C will survive for 10years is 247/315. The probability that A alone will survive for 10 years is 4/105 and the probability that C alone will die within 10 years is 2/21. Assuming that the events of t.he survival of A, Band C can be regarded...
  35. R

    Admissions Applying for PhD with Low UG GPA and Gap Years

    Hey everyone, I'm currently in my master's program in India and have been thinking about applying to states for a phd. So my problem is that I really messed up in my undergrad (2.74/4.00) but I'm doing much better in my MSc (3.2 in 1st sem, will try to reach 3.5 in total). Also, apart from that...
  36. S

    17 years later: Thank you FredGarvin and Artman

    I just stumbled upon a post I made when I was a kid here (16 then, I'm 33 now). Rudely, seems I never followed up and I can no longer reply in that thread. Wherever you are today @FredGarvin and @Artman, the hovercraft worked. In fact it worked better than expected and we immediately crashed it...
  37. A

    Other Possibilities after being a full time NTT lecturer for a few years

    Hi, I've been a full time physics lecturer for three years after the coming spring '21 semester. I got this job at the same university where I graduated with my PhD because (apparently) they liked my TA evaluations from students. Between graduating and becoming a lecturer I spent over a year...
  38. Evo

    Nice news for a change? How to turn back your life 25 years

    If this pans out, it would be nice. I had read FB founder Mark Zuckerberg bought one of these chambers for his wife, but can find nothing about it now, only that Justin Bieber sleeps in one. :rolleyes: https://www.yahoo.com/news/human-ageing-process-biologically-reversed-153921785.html
  39. O

    Will humans be able to live up to 120 years of age?

    <mentor note: moved to General Discussion> Will humans be able to live up to 120 years of age? I mean one day in the future will some scientific advancement allow most if not all of us to live till ~120 in decent health? Disregarding things such as accidents, viruses such as Covid. Thanks
  40. mfb

    Space inhabited non-stop for 20 years

    People under 20 have never lived at a time without at least two people in space. Exactly 20 years ago, on Halloween 2000, Soyuz TM-31 launched the first long-term crew towards the ISS to start Expedition 1. They docked 2 November. Since then the ISS has been inhabited continuously. This was by...
  41. BWV

    25 Years of the End of Science (or at least the end of physics?)

    John Horgan's book The End of Science was published nearly 25 years ago. This retrospective from 2006 he states https://www.discovermagazine.com/the-sciences/the-final-frontier-are-we-reaching-the-limits-of-science Not much has happened since 2006 to show that John was wrong. His premise...
  42. Drakkith

    Celebrating 10 Years with @Greg Bernhardt at PF!

    I just got my 10 Year award (3 days early) so I thought I'd say thanks to everyone for making the last 10 years here at PF great! Here's to another 10 great years! Special thanks to @Greg Bernhardt for creating this amazing place!
  43. Adesh

    I Why integrals took 2000 years to come up in a rigorous manner?

    Archimedes Riemann integral is one of the most elegant achievements in mathematics, I have a great admiration for it. Mr. Patrick Fitzpatrick commented on it as Archimedes first devised and implemented the strategy to compute the area of nonpolygonal geometric objects by constructing outer...
  44. T

    I A cold, massive, rotating disk galaxy 1.5 billion years after the BB

    Neeleman, M., Prochaska, J.X., Kanekar, N. et al. A cold, massive, rotating disk galaxy 1.5 billion years after the Big Bang. Nature 581, 269–272 (2020). https://doi.org/10.1038/s41586-020-2276-y Abstract Massive disk galaxies like the Milky Way are expected to form at late times in traditional...
  45. Astronuc

    Homo Sapiens in southern Europe, ~44-46K years ago?

    An international team of archaeologists exploring the Bacho Kiro (Бачо Киро) cave in Bulgaria since 2015 determined that a molar (tooth) the found is dated to about 44,000-46,000 years old...
  46. TaurusSteve

    Stargazing So If Something Happened In Space, Say 350 Million Years Ago....

    If something happened 350 million years ago in space, are we just seeing it/ receiving the light now? From SpacePlace "The nearest large galaxy to us, Andromeda, is 2.5 million light-years away. So, we see Andromeda as it was 2.5 million years in the past." Wow!
  47. TaurusSteve

    Stargazing Convert Light Years to Miles: 5.879e+12 Explanation and Conversion Guide

    5.879e+12. So that is what comes up if you convert one light year to miles. My question is, what does the 'e' mean? I see it quite a bit.
  48. P

    Other Searching for a postdoc in physics at 40 years old

    I 'am 40 years old. I 'am from Sudamerica. - Between my 19 and 25 years , i studied Industrial Enginer. - Between 26 and 29 years old i worked as Industrial Enginer. - Between 30 and 32 years old i studied a Master in Physics (branewold models). (1 publication) -Between 33 and 36 years old i...
  49. Athenian

    Traveling to Planet X in 23 Years: An SR Challenge

    Homework Statement: Problem: The planet X is far 48 light-years from Earth. Suppose that we want to travel from Earth to planet X in a time no more than 23 years, as reckoned by clocks aboard our spaceship. At what constant speed would we have to travel? How long would the trip take as reckoned...
  50. M

    B I am 47 years old and I trying to learn Mathematics

    How did you find PF?: https://www.intmath.com/blog/learn-math/top-10-math-help-sites-5966 Hello everyone. I know that there is a group isomorphism from Z[X] to the multiplicative group of all positive rational numbers. My question is: Are Z[X] and Q isomorphic groups?