Life Definition and 965 Threads

There is an obvious connecting with the size of a living creature and how long it lives. I know that this is not always true but for the most part it is. I was wondering what this field of research this is called. Is there an average life span to mass ratio?

Hello all, this is my first of likely many posts here at the newly discovered Physics Forums. I'll do my best to help others out, and hopefully will receive the same in return. I've gotten through about 3/4 of a large problem that I'm working through in my book (no solution manual FTL). Here's...

All the very heavy atoms found in the Earth were created long ago by nuclear fusion reactions in a supernova, an exploding star. The debris spewed out by the supernova later coalesced to form the sun and the planets of our solar system. Nuclear physics suggests that the uranium isotopes 235U...

As far as I know, there isn't any definition of "life" that holds up to a physics standard. Sure enough, we can talk about (bio) chemistry and the specific arrangements of certain molecules, but what I'm missing is a simple, physical definition of life. I know that Erwin Schroedinger once...

It took me a little while to wrap my head around circularly polarized light, or more specifically how this can be done "passively". Wikipedia didn't do much help until I found the article at Polarizer, if any of you were wondering how the new 3D movie technology works. My first question is...

I am a junior in high school in AP Physics. Although not in the curriculum, I have been reading about theoretical quantum mechanics, string theory, et cetera for the past few months and I am extremely intrigued. If I do end up furthering my "physics career," where might it take me? There...

why planethunters and astrobiologists are concentrating on finding life on Earth like planet with an orbit around host star rather than on jupiterlike planets moon i was browsing through the essentials of complex life to evolve on a planet. i am sure you all pretty much know that. plate...

If there existed one universe that could support intelligent life on its own, it is likely to lead to a myriad of simulated universes. True or false?

Where does a nuclear engineer work? At a nuclear plant? Out of an office? There have not been any new nuclear plants built in the US in many, many years. So is there any new designing/innovation going on or is it just maintaining day-to-day operations (checking dials, running diagnostics and...

How does shot peening help improve fatigue life, or rather, how does the compressive surface stress imposed help improve fatigue life? How does materials having high elastic moduli and large grain size prevent creep?

I know a lot of people say water or carbon and some people even say fusion or gravity. I think these are just the building blocks we happen to find in our universe but I think life could exist without any of those things as long as the laws of physics of any particular universe allow for...

Sorry if this isn't the best forum for this question; putting it here due to a gut feeling cos my brain wouldn't tell me where to put it. I'm thinking of an idea for an art project. I'd like to somehow depict what a boring, every-day scene might look like if our eyes could see more of the EM...

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I am having trouble finding the method to figure out if a shaft has finite or infinite life if it is subjected to a fluctuating load. I know how to solve for n(factor of safety) in these types of problems. Is there a value that if n is above it has infinite life.

Guys, our thesis defense is near already. It will be this thursday. I just want to know some more real life applications of Circular Motion involving liquids. The experiment we performed was we placed water inside a bucket then we spin it around. (Vertically) Some water spilled but most of the...

If anyone needs motivation to keep an active life, or work shoulder to shoulder with his/her children to prevent them from ending as adolescent fat slobs, here is something to think about: story of a 11 year double amputee excelling at wrestling...

Once again my professor asked us to ask 6 people the following question and see how they answer it so if you could respond and give an answer, I would really appreciate it. And if possible can you also tell me a little bit about your mathematics background? We are supposed to write up what...

Hi, I am half way of a Ph.D. in theoretical particle physics in an European university. I have started to worry about my future after learning how really difficult it is to get a position, how much do postdocs earn and how difficult it is for some to find a good job outside academy. The truth...

Rare Earth or rampant life? I remember watching Carl Sagan's Cosmos and seeing the equation for life in the universe for the first time. It really made me wonder if indeed we might find some form of life at one of our nearby extra solar systems. But I remember even then wondering if the...

Question given. Predict how the average life span of a nerve cell located in the brain differs from the average life span of a red blood cell. Provide a basis based on cellular features. I know that the average life span of a nerve cell is the life span of the organism which it lives in. The...

Hi All Following this Physorg article... http://www.physorg.com/news184915200.html" ...here's the webpage of the Professor's Directed Panspermia Society... "[URL Society for Life in Space (SOLIS)[/URL] ...in which he describes a program for propagating microbes throughout the Galaxy, as a...

Hello, I'm new here, and I really don't know much about astrophysics so would appreciate it if your replies were as simple as possible I've read that scientists are hopeful to find life on Titan, Saturn's largest moon, because the planet resembles Earth in its earlier stages. I have a few...

I am watching this now and it looks pretty interesting. One thing that caught my attention was a segment about a Japanese school that teaches internet etiquette to young children. http://www.pbs.org/wgbh/pages/frontline/digitalnation/etc/synopsis.html Watch online...

Hi, A few days ago I attended an astronomy lecture and while explaining the basic theoretical background of astronomy the lecturer compared the expansion of the universe from the big bang onwards to a balloon filling with air. Since the galaxies/stars are (loosely speaking) dots fixed on...

Hi guys i'm having much difficulties in understanding the relations between half life, decay constant and activity. I'll explain what i known here. T^{\frac{1}{2}} is the half life which is the time to reduce the nuclides by half. \lambda is the decay constant which can be solved...

I'm skeptical of "proof" of past life on Mars as as result of rocks found on Earth. I'm skeptical of "proof" of past life on Mars as a result of rocks found on Earth. http://www.digitaljournal.com/article/285660" Wouldn't real proof be found on the planet? I thought these Martian...

I'm guessing this is the right forum to post in. Ammonia shares many properties with water. It is polar, it is amphoteric, it reacts with itself to form its acid and base conjugates NH4+ and NH2-. Just as water is our basis of life, could another species use ammonia like we use water...

I love Physics and Math and really want to become good a it. I like to make exercise, hang out with friends, have a girlfriend and maybe in the future have a family. I know that you have to put the effort to succeed but i like to know if at least let you time to do the thing i mentioned above.

I have a first generation Apple iTouch 16 GB, and frequently download podcasts to watch and listen to. With over 1 million applications written, I have searched in vain to locate an application that will allow you to launch a video, and instead of displaying video and audio to suppress the...

can anybody tell me what the life of a aerospace engineer is like

I've gone through both "ZapperZ's "So you want to be a Physicist?"" and "The Should-I-Become-An-Engineer? Thread", and I am still having a tough time figuring out what exactly I want to do. Both threads, and many other threads, have given me a lot of insight about what each field involves, but a...

Just a quick thought... Everything to our knowledge is governed by four fundamental forces: the gravitational, electromagnetic, and strong and weak nuclear forces. But I am wondering, my desire to spontaneously move my hand to the right for example -- what is the explanation for this. Can...

im 21 years old and i have done absolutely nothing in my life. i haven't taken the sat,act, or any type of college entrance exams. i am stuck in a rut and i don't see a way to get my life moving. i have made so many mistakes in my life. there are so many regrets i have. i remember not...

An undergrad here, about to finish up within a couple of months. My grades aren't too good overall and I think I've learned that the academic life is not for me. Well, to be more precise, the stress and pressure associated with academic life is not for me. I am thinking about the possibility of...

Hi, first of all, i am no physicist, but after doing some research on some physics theories i came to this question. If an infamous "law of everything" was discovered, and supposing we knew the state of the universe at a moment in time after the big bang, and also supposing that we had super...

1. Half life of a radioactive substance is 13 days. How long for 400 grams to decay to 300 grams? Solve algebraically and show all work. Give both exact answers and the answer rounded to 4 decimal places. So I manipulated (1/2)A0=A0e13K to obtain K = ln(1/2)/13 Where do I go from here?

Ok I'm currently exploring other forms of life, mainly silicone and ammonia based life I found out they can replace carbon and water in our system but I'm a bit stuck on the fact if they can replace both. So we would have SI instead of C and NH3 instead H2O. I think that assimilation...

This test question is really boggling me and my math group. Any help would be appreciated. We know that AT*x=AT*b is the setup, but we're not so sure how to approach the problem most effectively. Here's the question: Use the data below to find an approximate formula for the life expectancy in...

A rotating disc moves in the positive direction of the x axis. Find the equation y(X) describing the position of the instantaneous axis of rotation, if at the initial moment the axis C of the disc was located at the point O after which it moved (A) with a constant velocity v, while the disc...

Is there or was there any life on Mars in the past? Do you think so? I personally don't. I think that martian meteorite got contaminated with Earth life.

Okay, so on this last section we have been learning about friction. I'm a newby and right now we know of kinetic friction, static friction, and rolling friction. So the friction occurring when a person is walking would be kinetic right? Then when a car is braking it would be .. static? When a...

This quote that i found in the book Super Force by Paul Davies, once read, litterally summed up all the thoughts that I have had since I could remember about how the universe works. tell me if you also think its true "An intelligence knowing, at any given instant of time, all forces acting in...

Homework Statement The half life of strontium-90 is 28.0 years. Deduce that the decay constant of strontium-90 is 7.85 * 10^(-10) s^1. Homework Equations k = ln 2 over half-life in seconds The Attempt at a Solution dunno...please help me solve this!

Homework Statement A motor is connected to a solid cylindrical drum with a diameter of 1.2 m and a mass of 51 kg. A massless rope is attached to the drum and tied at the other end to a 38 \rm kg weight, so the rope will wind onto the drum as it turns. What torque must the motor apply if the...

In the chinese art of Tai Chi, the word chi is usually translated as energy. The exercises are designed to keep our energy flowing through the body. What does physics have to say about this idea? Could life be considered a form of energy?

I wonder how marine life can withstand the enormous pressures at the bottom of the ocean without being crushed. The deepest part of the ocean, the Mariana's trench in the pacific, which is about roughly 30,000 feet deep, does have some rather strange-looking sea life inhabiting it. How do these...

Just a quick question about conceptual stuff. How is momentum lost in real life? Is it because of friction or heat? Yet that only affects kinetic energy, which means that momentum should still be conserved. So, what else is there?

I'm only at the end of the second year (out of 5) of a physics bachelor. I plan on to do a Phd although I've absolutely no idea in which area (and I know the admission will be very hard). After the Phd I'd like to do research for the rest of my life. Is that possible in the US? For example...

Homework Statement Can anyone here help me find how and where trig identities are used in real life. can you also tell me which identity(with example) and is used for what purpose and how. Homework Equations The Attempt at a Solution I found out that it is used in the field...

I was looking at a program referring to dating the life of the Earth and I`m puzzled on a bit that I`m sure must be obvious to geologists. The dating was based on the ratio of lead that was present in combination with uranium. Lead being the final element after the uranium decay. It was...