Age Definition and 590 Threads

Hello Everyone :) I would like to ask about the age of the normal PhD student. Is it too late to begin the PhD at 30 ? I would like to apply for a position in nanoscience. Is it difficult to get such position with the age of 30 ? What is the more important, the age or the grades of...

My little girl, who just turned five, asked if she could have her ears pierced. The answer was 'not for awhile', but that got me thinking, what is the appropriate age for her to get her ears pierced?

Hello Everyone, I am new to this forum. I understood from sources that space-time is like a fabric. The massive bodies bend the space around it, hence the gravity. If time is 4rth dimension, so, the space is bent in time due to mass. that pretty much explains stopping of time in black holes as...

Hi all. I'm on another forum discussing Gerald Shroeder's assertion that the age of the universe can, from certain reference frames, be said to have been 6 days at the creation of the Milky Way. In other words, that the creation account in Genesis is literally correct. Shroeder makes a...

OK, I'll dive in and start a climate change thread. I'm fascinated by the Nature paper by Abe-Ouchi, et.al., which I already uploaded in post #21 of this thread. If you look at Figure 1, the model does an outstanding job of modeling the last several ice ages. I have been somewhat skeptical of...

Yes, curious about that. (No, I'm NOT asking about some short term disturbances when glaciers were melting, but whether with lower temperature and part of continental shelf above water caused the currents to change their direction)

hello, my name is pablo bähler, i live in argentina right now, I am in the second year of a bachelor in physics but i am planning to move to switzerland, learn german and restart the bachelor in physics. i am 20 years old right now, and by the time i start the bachelor in physics in the...

Homework Statement For the problem see the attachment, I am trying to evaluate this integral... but the fun part is that I am getting totally different resultsThe Attempt at a Solution First of all, I tried to put the integral in the Mathematica, but the first result contained logarithms...

Homework Statement Geologists are able to calculate ages of rock samples through measurements of certain isotopic rations combined with known radioactive decay rates (all such decays being considered to adhere to 1st order kinetic rate laws). Two such processes leading to stable isotopes are...

I've been doing some Cosmology, but I'm having a really hard time understanding the results for the age of the Universe intuitively. For example I can work out from the FRW equation that in the case of no Cosmological constant and no radiation in a flat matter dominated universe the age is...

Hi, I am new to this forum! I am a 30 years old math instructor at a community college with a M.S. and B.S. in Math that included course works in calculus, advanced calculus, analysis, linear algebra, theoretical statistics, and machine learning, with intermediate knowledge in R and SQL. I...

I was taught integration formulas like these: . . \int\frac{du}{u^2-a^2} \;=\;\frac{1}{2a}\ln\left|\frac{u-a}{u+a}\right|+C . ** It took up only one brain cell and it saved me the bother of Partial Fractions (every time).I was taught: .\int\frac{du}{u^2+a^2}...

I'm interested in your advice and any insight you may provide. Thank you. I am just starting my second semester last week as a freshman in the undergraduate physics program at the Uni of Delaware. The fall semester went well and I understood the material fairly well since the semester focused...

After a recent conversation, I was trying to determine if there is an online authoritative definition for the age of the universe. The Wiki article states "the International Astronomical Union presently use 'age of the universe' to mean the duration of the Lambda-CDM expansion", but the...

We all very well know that, Earth has been made 4.5 billion years ago. Suppose, we are to explain the age of the star and we say that it is 27 billion years old. One year is the duration of time taken by the Earth to revolve around the sun once. Before the origin of Earth, how could we explain...

For some circumstances in my life I was not able to give steady continuation to my studies, so now I want to do a PhD but I have seen that some people finish their PhD by the age of 26-28. I am 25 so my question is: Am I too old to start a PhD? Thank you.

Two twins A and (evil) B. Twin A remains "stationary" while evil B goes at near light speed to-and-fro. Ignoring General Relativity (acceleration/deceleration) evil B experiences time dilation and as result, when they meet up again, B's clock is behind A's clock. Look at it from B's point...

Hi Great Ones (!) Just wondering if someone could help me understand something: Time is relative. If our planet orbited close to a black hole where the effect of gravity was very strong we would look out into the night sky and see stars formed and die, possibly in a single night. We...

Legend: A is the source B is the photons/light C is the destination (which isn't fixed) c is obviously the speed of light Yesterday I was sat thinking about how visible light can be older than the universe itself. I came to the conclusion that the...

Is there any reason to think that that the speed of light could vary with time (taking t=0 at Big Bang), ie, could light have been slower or faster billions of years ago? Also, is there any experimental evidence so far that either confirms or denies this? Do we know of any experiment that proves...

Homework Statement Suppose you have a 1.4g sample of old charcoal. It produces 0.7 beta decays per minute. How old is the charcoal. Given: 1g of carbon current day has 6.36x1010 atoms of 14C Homework Equations N = Noe-rt N = number of atoms in the sample (current-day) No =...

I am 20 years old, I am probably going to enter a engineering program not next fall but the one after it. As I understand it, biomedical, computer science and pretty well any engineering degree will be good for the future. What do you guys think about being 20-21 and entering a program? What...

Hi, I am a math major in South Korea. Recently, one of my friends came to me with a rumor that age of the applicant is a critical factor in admission to top math grad school like princeton, harvard, etc... What worries me is that due to the country's "mandatory military service law ", I...

Hi guys, I hope I can explain my situation well enough and get some good feedback on what to do. I graduated with a Bachelors in Economics, at the age of 24, started college late due to some financial hardship. I've been working for two years now, and I'm at a crossroads on what to do next...

An astronaut must journey to a distant planet, which is 186 light-years from Earth. What speed will be necessary if the astronaut wishes to age only 13 years during the round trip? (Give your answer accurate to four decimal places.) _________c 13y = to 186ly = t to/t = (√(1-(v^2 /...

What causes people to age differently? Here is a simple example: A man moves inertially between two clocks in inertial coordinate system A. He is age 20 when he starts. Man (20) --> [0]-------------Frame A-----------[?] Clock````````````````````````Clock Man...

Acc. to general relativity time runs slowly near a massive body.So, i have a question bothering me from some time that if time for every body/object in universe runs at a different rate then how can we determine the age of universe i.e. 13.72 billion years. Near a black hole as time runs...

You find two yellow stars at the same distance (but not in a binary system!). They have the same mass, but one is much more luminous than the other. Which one is older?

Do we assume that all galaxies which are equidistant from Earth are approximately the same age? Or are there galaxies at roughly the same distance from Earth but which vary greatly in age? Are we aware of any galaxies which are significantly younger than the Milky way?

I have always been confused why it is said that the universe is 13.7 billion years old it just does not make sense to me. Why do we not say that the stuff that we can observe is 13.7 billion years old? We base this on the most distant things that we can see from our perspective here on Earth...

Hi, I have the following problem. Consider an age-structured population growing according to a Leslie matrix. Suppose the population is in stable exponential growth, i.e. its age-structure is constant in time, while the total population is exponentially growing (or decreasing) with exponent...

Suppose our galaxy, say A, is moving at near the speed of light with respect to another galaxy, say B. (which I think it indeed is doing ). My age is say 80 years in my position (at earth, in the solar system, in the galaxy). 1. Persons in the 'another' galaxy are doing experiments...

I'm 27 years old and I recently quit my job to go back to school for physics. I just finished up my first semester and I'm about to start the Summer semester (I'm technically a sophomore though, even though I'm just starting, because I do have transfer credits). I have to do a few different math...

hello there , now excuse me to those to whom this looks like the questions you have hard a thousand times before. Now I understand how we calculate the speed of light in vacuum and no doubt we can do that under laboratory conditions etc. Light bending in gravitational fields is also...

Hi, My name is Ken. I am currenlty 42 Years old and have been working as a freelance camera operator for several years. After much struggle, frustration, and recently, time spent with a career counselor to find my true vocation, I have finally figured out what I want to be when I grow up: an...

Before I say the exact question, this is a inquiry about a hypothetical situation that says the Universe is infinite in both size and age. If possible, I would like a full explanation to what happens to the Universe going beyond the specific question, but I have the question here basically as a...

Hi all, my end of year Physics exam is tomorrow and I need some help on this question and if someone could help I'd appreciate it. Carbon-14 has a half life of 5730 years, and an equilibrium concentration in the Earth’s lower atmosphere of approximately one atom per 8.3 x 1011 atoms of normal...

Hello all! I joined this illustrious community with the hopes of expanding what little knowledge I know about physics, calculus, and general sciences. I am wondering, how should I learn physics. I am in middle school, am generally intelligent if I can say so myself, and have a thirst for...

Morning everyone, I apologize for bringing up a topic that has probably been discussed to death here in the past. I've been reading the FAQ, and a few old threads about finite vs infinite universe, but I'm still struggling to grasp both of these ideas. I'd be really grateful if someone could...

My grandmother (age 76) was admitted to a hospital two weeks ago. One part of her diagnosis report caught my attention - her WBC count was 25000/μL of blood, which is more than thrice the optimal value. While the double value would be acceptable considering she is old and such, but I clearly do...

I have learned a lot about cosmology on this forum, but I’m still behind on the logic. So far I have understood that, since the universe is everything, it cannot have a center nor a boundary. But it does have an expansion and that’s when my problems start. I would like to concentrate on a...

Basically, I'm a sophomore at Stony Brook University and I was doing biomed but now I think I want to be a software engineer so, I'm trying to get into the Computer Engineering program at my school. I did research and I learned that software developers/software engineers are growing in demand...

I'm 20 and joining collage this spring. I've taken only the minimum amount of math my math thinking is mediocre seriously and computer science requires a lot of math, mainly calculus, advanced functions and physics but i am really interested i always loved physics and computers is my thing so My...

Is the ace age ever expected to return at any point in the distant future? Human beings survived the first ice age, so hypothetically speaking, what effect would it have on modern civilization if it occurred today?

Hello. First post and sorry if the forum is flooded with similar questions, I'm 24 and I was a physics major but haven't spent a day in a class room since 2007 when i dropped out of college to care for an ill family member. I want to go back to school but what concerns me is how much of a...

Hi guys! I have a small doubt in the concept of age of our universe.Everyone say that our universe is 14.4 billion years old.Now I can't understand with what frame as reference this calculation is made. Is there any global reference frame with which these calculations are made?

Homework Statement Consider a universe where there are two types of matter: dust and curvature. The density of dust evolves with time as ρdust(t) = ρ0R(t)^(−3) and curvature evolves as ρcurvature = −kR(t)^(-2) where ρ0 and k are constants. The Friedmann equation is: H^2 = [(8∏G)/3][ρdust...

The estimated age of the universe is often stated to be about 13.7 billion years. But I've never seen any qualifiers on that age. We know that time passes slower the greater the gravity field you're in. Even the difference in gravity between the Earth's surface and orbit is enough to cause...

problem.. I've been given this question as my homework over the holiday, and I've come to attempt it and I'm completely stumped, as are most in my class so could you guys point me in the right direction? question.. Uranium decays into lead. The half life of uranium is 4,000,000,000...

Hi, The Universe in 14 billion years old. Is that then: 14,000,000,000,000 or 14 million million as in 1.4x1013 years old or 14,000,000,000 or 14 thousand million as in 1.4x1010 years old (I know a billionaire has a thousand million 1,000,000,000) Thanks,