Years Definition and 619 Threads

Some of you have already seen another picture from this session on fb, but there is more :wink:

Summary: If the furthest quasars we can see are let's say 13 billion light years away from us, then does this mean that the distance between us and that quasar was 13 billion light years at 13 billion years ago? To anyone educated in physics this might be a silly question but to me this is...

I remember watching some documentary on TV some years ago and in it, they were mentioning how there was a physicist who was doing some research on radioactive elements in the laboratory, but because he was little bit crazy he believed that the fez hat he wore on his head would protect him from...

At the time of asteroid impact 65 million years ago wiping out the dinosaurs and 50 % of all life on Earth - presuming all but the smallest mammals or sea creatures suggests that humans most likely wouldn't be here today if not for that event because the tiny mammals which then existed would not...

So I just graduated Chemical Engineering from SJSU at 27 yrs old. Took a few years off in CC and a few semesters off here and there for work mainly. I'm personally interested in going into science entrepreneurship. [My non-science career] I was more focused on the entrepreneurship part...

Summary: I'd like to know if anyone else thinks of these things <mentor moved to general discussion>[/color] What if one day we can "warp" x light years away from Earth, build an enormous telescope, and look back at the Earth x years ago with resolution that rivals the American flag on the...

I'm curious how technology education in high school has progressed throughout the years. I graduated HS in '89. While there I had three semesters of programming. Basic on an Apple 2E and RPG 2 and COBOL on an IBM systems 3 mid-range. Punch cards for the win. Please share your experiences.

I'm a not techie - liberal arts and social sciences grad. For those knowledgeable about this space, can you explain what AMD and NVDA have going for them that is so great that their stocks have risen by 20-30 times in the past few years? I know that AMD is basically a chip company. They...

Just as the title says, I am trying to figure out what they are actually telling us when they say something is so many light years away. If you were to search the internet "what is the most distant object ever observed" you will be told it is a galaxy 13.3 billion light years away. Do we...

This is one of the most powerful and incredible short movies I have ever seen. (I got the link to it from a friend today.) It contains clips of interviews of American soldiers who were exposed to real nuclear detonations. What they have to say is terrifying, intense and important. That's all I...

From experience, up to what age can the brain and neurons still able to study physics? Steven Weinberg is already 80+ years old. Is his brain still as good as when he was in the 20s? If I begin undergraduate course in physics at 50 yrs old. How long before I can graduate as a PhD? I want to...

How did they calculate the half life of xenon 124 to be longer than the age of the universe if they only observed one decay? Is there some way to estimate half life?

Bohr declared it the duality paradox. It works. But a paradox in science is an unresolved problem. Are we any closer to resolving that problem 100 years after Bohr's declaration, or has the physics community just grown numb to it?

Continue reading...

Is there a historical example of a theory that physicists all over the world pursued and developed in a concerted and organized research for more than 20 years without results, but then turned out to be correct? I get frequently as an answer the heliocentric vs. geocentric model, it took...

We commonly see lists of "best science" both here on PF and elsewhere. I think it is time for a little friendly rivalry from the engineering side. I arbitrarily chose 100 years as the period. The wheel and Roman aqueducts were great engineering but not much fun for us to talk about because we...

i read somewhere the body replace itself every 7 years. does the brain also do this?

Been tracking down the most unusual bug I've seen in 40 years of programming (mostly in assemlber and C). It manifests in the test suite for an object oriented XBase language implementation that's been ported everywhere from Palm Pilot to OS/2 to the Blackberry tablet to Windows to, now, Qnx7...

Hello My name is Joseph I am a physics student, I am new to Fortran, I know how to write a code for solving differential equations, but now I have a physics equation for evolving star rotation as a function of mass. and I do not know how to evolve (using any numerical method, such as Euler) so...

Hi all, I'm seriously considering going back to college for a degree in engineering, specifically mechanical. I meet the aptitude tests, all of the interests, want to design and create, etc. I've definitely got the bug. I do DIY carpentry jobs on the side, I've got technical degrees in machine...

https://electronics.howstuffworks.com/everyday-tech/lithium-ion-battery2.htm "Lithium-ion batteries age. They only last two to three years, even if they are sitting on a shelf unused. So do not "avoid using" the battery with the thought that the battery pack will last five years." Is this...

John is x years old and his mother is 25 years older than he is. a) How old is John's mother? My answer: x + 25 = mother b) What is the sum of their ages now? my answer: x + mother = current age c) when john is 12 years old, how old is his mother? my answer: 12 + 25 = 37.

Q: The sum of the present ages of Vatha and Chris is 36. In 4 years time, the sum of their ages will equal twice Vatha's present age. How old are they now?A: Vatha:22, Chris: 14 (from the back of the textbook, only I'm not sure how to get here)I'm a little stuck with this one. If you could...

It had previously been verified within our own galaxy. http://uopnews.port.ac.uk/2018/06/22/einstein-proved-right-in-another-galaxy/

A star is 3.7 x 104 ly (light-years) from the center of its galaxy and is moving in a circle around that center at a speed of 170 km/s. (a) How long does it take the star to make one revolution about the galactic center? (b) How many revolutions has the star completed since it was formed about...

How fast would you have to go to reach a star 240 light years away in an 85-year human lifetime? Here, I know that I'm supposed to find $v$, but I'm having a hard time setting up my equation(s) in order to reach the final answer. :(

I realized that this movie is now 50 years old. That goes for anything else in 1968 of course. This was animation quite different from Disney. A really good band did the music too. Have we seen this movie?

Hello all, I have a few small questions regarding logarithms, which I would like to ask your help with. 1) A car loses 50% of it's value every 4 years. How many years does it take for the car to lose 1/3 of it's value ? (I think you need log with basis of 2 here, but not sure) 2) A company...

Say I have a function that represents the population growth of a certain country that can be written as ##f\left(x\right)=1.25\left(1.012\right)^t##, where t is in years. I can graph this function and it will look a certain way exponentially. I've looked at a ton of examples, and they're all...

I just got a taught Master offer in Physics (part-time mode for 2 years) and I don't know what to do... First of all, I have a BSc in Applied Physics which I graduated in 2011. I study Physics because it is interesting. I felt happy when I got to understand something new (about the universe)...

Hi, I need to convert a value of 12*10-16 m7 N-3 y-1 to the units of kPa-3 m2 s-1. Can anyone help me? where: m = meters, N = Newton, y = year, s = seconds. Thanks!

Perhaps this isn’t the place to ask, but I was just looking to hear opinions from some people on here about my situation. I’ve been out of school for 4 years now, having left to enlist with the Air Force. While in school I was majoring in Physics/Mathematics. I was a B student in Physics 1, 2...

Hello! So I’m not totally sure if this is where I post this but what do you do for Chinese New Year? I usually march in the town parade but it got canceled this year so instead I went to Ala Moana to go eat some good food with my family. I saw a lion dance. So, what do you guys do?

I find on a website as ours, we shouldn't have forgotten this: On January, 25th it has been 100 years, a complete century, since Emmy Noether published her paper "Invarianten bestimmter Differentialausdrücke" (Invariants of Certain Differential Expressions, Göttingen 1918). It is still the...

If I have a starting population of 200 people with an average life expectancy of 35 and a yearly growth rate of .10, what will my population be in 1,000 years?

Greg Bernhardt submitted a new PF Insights post 3 New Years Tips For Cooling Off Debates Continue reading the Original PF Insights Post.

It appears the oldest structures don't go father than 4500 BC. I was wondering if it's possible that were are structures that go beyond 4500 BC that we just haven't discovered yet? I doubt that there are buildings that can last for 500,000 years before falling down. However, is it possible that...

https://en.wikipedia.org/wiki/Most_recent_common_ancestor I was reading about the human most recent common ancestor (MRCA) at the above link at Wikipedia. According to this article at Wikipedia, there have been common human ancestors to all humans alive today. This sounds far-fetched to me...

So, I'm writing something taking place a few centuries after a global nuclear war, but I'm unsure what the climate would be like, both in general and in the story's specific setting - the western coast of Canada. Would the average temperature or amount of yearly rainfall change? Would areas...

Homework Statement An investment is made at 12.5% annual simple interest. Find the number of years it will take for the cumulative value of the interest to equal the original investment? Homework Equations V=P(1+rt) Where V= interest on Amount P = Principal amount r= interest rate t= number...

When we learn about energy and momentum at high school it can be taught by simple equations in a 1 hour lesson. So why did it take over 100 years from approx 1690 to 1790 for energy being direclty proportional to v squared to be accepted by the wider scientific community. Also shouldn't the...

Science news article by their dog domestication guy (David Grimm). Fossils of dogs, bred for use on sleds 9000 years ago, found on Siberian island.

Greetings, I am an undergraduate student, just finished my third year in physics. I began studying physics in my early 20's and had to drop out and work. 3 years ago, I decided to go back to school and build up a career in Physics. however, I am running out of options and not sure what to do...

Homework Statement I'm currently working through the following question: "A spaceship travels from Earth to the vicinity of the star that is measured by astronomers on Earth to be six light-years away. The spaceship and its occupants have a total rest mass of 32 000 kg. Assume that the...

oops this is a pre calc question $\tiny{hcc.18}$ the half life of silicon-32 is $710$ years. If $10g$ are present now how much will be present in 600 yrs? to find out $k$ using $$A=A_0 e^{kt}$$ $$\frac{1}{2}=e^{k \cdot 710}$$ $$\ln\left[\frac{1}{2}\right]=k\cdot710$$...

There has been a lot of discussion about the time when humans first arrived in the Americas, and also which way they took. 15,000 years ago? 20,000 years ago? 40,000 years ago, and with more immigration waves later? Along the coasts? Through the interior? Or even via the open Pacific...

My Kepler Bb humanoids are externally gender neutral until they are 5 years old. So you can only tell if they are male or female before then via genetic testing or an abdominal scan like an ultrasound, X ray, or CT. Now here is my idea as to how males and females develop in childhood: Male...

I read quite often on this forum and elsewhere that radio signals emitted into space fade enough after a few hundred light years that they are no longer discernible. How do we expect the Arecibo message to be received some 25,000 years from now?

Eventually the Sun will go through its phases and cool down. Is it possible to calculate how long it will take for the surface to cool to 75 degrees Fahrenheit?

I'm sure this is probably a stupid question with an obvious answer.. But i can't come up with it.. So, the observable universe is ment to be 90 billion lightyears across, right? And it's 13.8 billion years old, right? And a lightyear is the distance it takes for light and fields and stuff to...