Life Definition and 965 Threads

Real life momentum *URGENT* I need a few major examples for how momentum is used in real life. Any good examples?

Hello there helpful people (at least I hope so). I've been lurking in the shadows of these forums since I stumbled upon them a week or so ago and I have come up with a question I have been unable to find enough information for. I'm in my first year of a BSc in physics, although its pretty...

Can someone explain all the known paths a star can take from its birth to its death? This is what I know so far. Please correct me or add things where they need to be in the list 1) Hydrogen gas, clumps together by gravity. 2) Hydrogen atoms bump against each other and these collisions...

Homework Statement A radioactive needle contains 222 Rn (t1/2=3.83 d) in secular equilibrium with 226 Ra(t1/2=1600 a). How long does is it required for 222 Rn to decay to half of its original activity?Homework Equations A(t) = -\frac{dN(t)}{dt} = \lambda N(t) The Attempt at a Solution...

I suddenly realize that my life has no purpose. Is this how slackers feel because now I don't feel motivated to anything since it will lead me nowhere. Don't get me wrong I'm not suicidal or depressed.

Hello, I have 2 24V lead acid batteries in parallel to make a power supply for my circuit. I want to do some drain tests, and plot a curve for % energy remaining vs. time. The load on the battery isn't that large, and I don't want to have to supervise my experiment for 12 hours solid. Im...

Homework Statement Could life arise from non life today? Why? Homework Equations The Attempt at a Solution I know that it's not possible today but I'm not sure why?

Recently, I've gotten into a kind of crisis mode. I am a third year undergraduate majoring in physics. Last semester, I've overloaded myself with graduate courses and dragged through it with good marks at the end. My social life was pretty much non-existent. I slowly realized that I cannot...

Hello all, Below I have a few questions regarding calculating the half life of muons. We measured how many muons were recorded at the top of a mountain, then measured how many muons were recorded at the bottom. Using this data, we calculated the half life of moving muons. Thanks for the...

Today I went down to Albuquerque and took part in a competition called English Expo and took 2nd place in one of my two events. My friend and fellow PFer Capslockroxx was there too and got 1st in one of his events. I don't really know why I'm bothering to mention this, just felt like sharing...

Salt industry What is the industry? What chemistry is involved? Process… What products come from this process/industry? Where do the products go? Who uses them? For what do people use them? Evaluate benefits of this industry on life and society How has this production benefited...

Hi, I've been suffering of mononucleosis in late 2006. I've read that the virus never leave out the body for all the life of the infected person. I wonder if it is possible that the virus becomes active once again (like the herpes virus since they are closely related) and also if it is...

Is it just because the brain is more spongy at an early age than in our later years? I am aware that we gain new interests and knowledge as adults , but those interests are usually tied to the interests and we had as children or in our tenns / early adulthood, and therefore just continued to...

http://news.yahoo.com/s/pew/63rejectdarwinstheoryofevolution;_ylt=An8rzCf84KVpYf08mAMFUO8DW7oF After all of these years ... Perhaps what we are witnessing is the exhibition of " an evolutionary trait " deemed as common sense. Really - why do some scientist believe that there is an...

http://content.nejm.org/cgi/content/full/357/4/328

What do you guys reckon to the odds of us finding alien life? The fermi paradox: 'If there are all these billions of planets in the universe that are capable of supporting life, and millions of intelligent species out there, then how come none has visited earth?' I reckon there exists...

Hai everybody! Could there be Life on Mars ?Are there any chances that the martians could be living. Once a report was published stating that a female was seen on the Mars,is that true ? Another report came stating that Water is found in the rocks as crystallized water. Can we...

First off, i love to bodybuild, that's my life right there, but i also love learning about the orgins of space and how its made and BEYOND. BUT If i want to pursue my life into become a physicist, will i have time to work out and eat my 6 meals a day? And get an 8 hour sleep? Whats the life like...

Why do some scientists assume that intelligent life may be rare--that because only one high-intelligence--homo-sapiens (us) developed on Earth, that inteligent life is rare to evolve throughout the universe? Instead of seeing it that way, why can't you turn that thought around and assume that...

I hated to let this one go without a post. There is already a post in Astronomy linking to the video. https://www.physicsforums.com/showthread.php?p=2035686#post2035686...

Homework Statement A radioactive material has a half life of 1550 years. Find the time during which a given amount of this material is reduced to one forth. I am really not sure how to do this since we have not covered it in class yet. But, a formula that I have found involves find the...

Hi, I live in the northeast, well known for its heavy snowfall in the winter. Where I live, for the past few days, it has been raining heavily during the daytime and stopped at night. This has collected in various ducts and pipes meant to remove the water from the roof. At night, when the...

I used to always wondered why people in my age group were hopelessly passionate and seemed to fall into the stereotype of 'young and restless dreamers' until a few years ago. As I go on in college, I, as well as many other people my age, have to make more and more choices and seriously...

Please help me solving this homework! 1. List three reasons why knowing the speed of sound is important to your life? 2. From at least three sources, gather information on how you can measure the speed of sound. then, describe the methods that are available to you. Information can be...

I am an older person (30 +) that has worked in technology for nearly 20 years. I have worked on and with High Performance Technical computing clusters to support NASA and scientist. I have no degrees. I have always has a deep interest and enjoy Astronomy, Physics, Cosmology. I am...

How does the temperature of a star relate to the radius of a star? How does the mass of a star affect the temperature of the star's core? How does the luminosity of a star relate to how long a star will live? How do the spectral lines of a star determine if the star is a first generation...

Hi all, I'll be starting my final year of my undergraduate degree in pure mathematics next year. My intention is to do postgraduate work and then try to get a position as a research fellow. However, I don't really know what a research mathematician does on a day to day basis, I just like the...

HI all. Just looking for some ideas or pointers. I wish to pass on an idea to a friend. I want to look at Platonic shapes in 3D evolving through various iterations. I've played with pretty fractals and I've played with the 2D and 3D Game of Life games. both nice diversions :) on a rainy...

Earth first formed about 4.6 billion years ago, condensing out of the gases & dust in the proto-Sun's Planetary Disk. But, for about the 1st billion years, the proto-planet was repeatedly pummeled by swarms of Impactors. They deposited gargantuan quantities of energy onto the Earth's surface...

Hey PF, I want to resurrect an old robot radio I have sitting around. What exactly is involved with building an AM/FM receiver?

So I like physics a lot and think that I would probably like to get my PhD but I have some concerns. One of the big ones is being able to have a social life while working on my PhD. If it was a degree that only took like 2 years to get I wouldn't be so concerned but considering that if I do...

Bigger stars are significantly brighter. That pushes back their Habitable Zones (HZs), where D2 ~ L, which makes them look smaller in the skies of (hypothetical) habitable planets, whose years are also a lot longer: Type Mass Temperature Radius Luminosity HZ-Distance Apparent-Size HZ-Year...

Assuming we can ever find another habitable planet and can get there, how the heck would we start to colonise it. If there is water, vegetation and there is~the same climate of Earth.

I am currently a junior at a 4 year university and I will be graduating in the spring of 2010 with a BS in physics. I'm having a very hard time deciding what to do after I graduate, so I thought I'd ask around for ideas. My problem is that I have a lot of interests, but I don't know how to...

1. Death 2. Taxes 3. To make continued substantial contributions (in anything) in the long term, one must work very hard. Agreeable?

The problem statement An electron going from 2p to 1s state in hydrogen sits up at the 2p for a while then jumps down. with the given eqn W=\frac {4*\alpha*\omega^3}{3*c^2}*\mid r12\mid^2 \mid r12\mid^2=\mid<1\mid x\mid2>\mid^2+\mid<1\mid y\mid2>\mid^2+\mid<1\mid z\mid2>\mid^2 alpha is...

If one wants to live a LOOOONG life doe's it matter what one eats and drinks? I recon it is all in the mind set, if one doe's not want to kick the bucket one will endure, just so long as some thing doe's not come along and throw a spanner in the works.

Can somebody give me an idea what you get upto on a day to day basis? I know roughly what you work towards in a PhD, obviously it depends on your topic, but I have no idea what it consists of day in and day out. For example, what maths do you do daily? What theory do you do daily? How much...

Now available on line through Google: http://images.google.com/hosted/life Images from the Civil War forward. They will have 107 images eventually.

I thought this internet application created by http://lindenlab.com/" was interesting: http://en.wikipedia.org/wiki/Second_life http://secondlife.com/ It takes the idea of a video game to an extreme. Video games normally either capture some specific portion of real life (i.e. life...

Why is life not included as a separate (fifth) fundamental force of nature? I’ve heard it said that life is more efficient at transforming energy (moving things around) than nuclear energy. This would seem to imply a force that is separate from the other 4. (I’m not necessarily talking about a...

It may sound trite, but people keep asking it. So, what is the meaning of life?

That is, if these cells even had anything to do with it. We're only going by the endosymbiotic theory.

is the chances pretty rare that advanced and intelligient life exists somewhere else in our universe, I mean it seems like we got pretty lucky here on Earth to get these conditions to have such abundant life. I am not doubting that bacteria and other simpler organisms exist elsewhere but it...

I've always wondered what a day in the life of an academic is like, particularly mathematicians, philosophers, and most of all theoretical physicists. So what's an average day like for a theoretical physicist? Do you sit in your thinking chairs, lost deep in thought, trying to unwind...

The first brains came about in the precambrian or at the border with the cambrian around 560 million years ago when the first multi-celluar organisms emerged. It has always struck me how/why organisms developed brains. The brain must have emerged together with eyesight, since eyesight would be...

Say you map out the entire decision tree of an individuals life starting from birth. Each node has N branches, where N is very large, and delta t approaching zero. Let's keep it finite density because we want some results. Now you trace out the individuals realized path outcome amongst...

If someone dies in a hospital a member of medical staff tries to brings their heart back to life, sometimes this works. Why if someone dies of nateral causes can't their heart be braught back to life after a while?

If the nuclear fusion reaction of converting 4 H ! He occurs at an efficiency of 0.7%, and that mass is converted into energy according to the equation E = mc2, then estimate the Main Sequence lifetime of the Sun (spectral type G2) in years if the luminosity of the Sun is 3.83×1033 ergs s−1...

how do you delete posts? i was going to post a question and i accidentally posted it how do i delete this error?