What is Cold: Definition and 394 Discussions

Cold is the presence of low temperature, especially in the atmosphere. In common usage, cold is often a subjective perception. A lower bound to temperature is absolute zero, defined as 0.00 K on the Kelvin scale, an absolute thermodynamic temperature scale. This corresponds to −273.15 °C on the Celsius scale, −459.67 °F on the Fahrenheit scale, and 0.00 °R on the Rankine scale.
Since temperature relates to the thermal energy held by an object or a sample of matter, which is the kinetic energy of the random motion of the particle constituents of matter, an object will have less thermal energy when it is colder and more when it is hotter. If it were possible to cool a system to absolute zero, all motion of the particles in a sample of matter would cease and they would be at complete rest in this classical sense. The object would be described as having zero thermal energy. Microscopically in the description of quantum mechanics, however, matter still has zero-point energy even at absolute zero, because of the uncertainty principle.

View More On Wikipedia.org
Recent contents Top users
  1. ranger

    Hot or Cold Shower: Health Benefits of Regular Showers

    It is better to take a hot or cold shower after a regular days work i.e. not after exercising? I personally enjoy very warm showers regardless of the season. I was just wondering if there are any health benefits to either.
  2. Evo

    Will the Arctic Cold Front Cause Severe Weather and Damage to Crops?

    Anyone not getting snow? My forecast for tomorrow aka "Evo Alert" And I am supposed to see the doctor tomorrow and I still haven't replaced my donut tire from when I got that flat, and the stupid car is only a few inches off the ground. Turbo has been hit pretty bad, Even Kurdt in...
  3. Y

    Solve for Cold Surface Temp. of Slab with Heat Flow Rate 240 W

    Homework Statement The absolute value of the heat flow rate through a slab of area 0.83 m2 is 240 W. The thickness of the slab is 1.4 cm and its thermal conductivity is 0.6 W/(m·K). If the hot surface of the slab is at 40°C find the temperature of the cold surface. Homework Equations...
  4. V

    Is there a specific length of time for cold process saponification?

    There are often posts on the soapmaking forums about using one's own soap before it is cured. Curing time for soaps made with oils that solidify at room temperature is four to six weeks. For 100% Castille (olive oil) or similar, the curing time is six months or longer. Of course, we all...
  5. V

    How is development of ash and oxidation of oils in cold process soap related?

    I posted this on thedishforum: On the German soapmaking forum, there are several posts noting that there seems to be a correlation between ash and oxidation of oils. Can you speak to the presence of ash and soap going rancid? And got this reply: Yes, I could see this being an accurate...
  6. Q_Goest

    Fatigue strength of 304, cold worked versus annealed

    This web page: http://www.hghouston.com/ss_cwp.html states: The web page also shows that fatigue strength can be improved dramatically by cold working. Endurance limit is listed as: 304 annealed = 35 ksi 304 3/4 hard = 92 ksi I'm in the process of designing something that will be...
  7. W

    Privatives - Darkness and Cold

    Hi All This is my first post here and I have a question that should be relatively simple to answer. I am engaged in a debate with someone at the moment on a scifi forum. My stance is this: "Dark" is not a "thing" - it is merely the absence of light. You can measure light intensity...
  8. K

    Find Outlet Temp of Cold Stream of Counterflow in Double Pipe Heat Exchanger

    Given the mass flow, Cp, temp of the inlet streams of both hot and cold streams. As well as being given the inner pipe diametre of the double pipe heat exchanger. Also knowing the setting is at counterflow and that the overall heat transfer coefficient and that the temp difference between the...
  9. Q

    Heat Car Engine on Cold Morning: Tips & Advice

    Does anyone know the proper way to do this?
  10. P

    How many grams of cold water necessary to lower temperature in container

    Homework Statement How many grams of 20 degree C water do I need to add to 100 grams of 80 degree C of water to get the final temperature down to 50 degrees C? Homework Equations I'm sure it's a pretty simple equation, but I don't know it. (I'm studying a lot of different things at once...
  11. E

    Optimal House Color in Cold Climate

    A house with AC in a hot climate should be painted white (or covered with mirrors) to reduce absorption of light from the hotter sun and surrounding objects. That seems obvious. But what should cover a house in a cold climate? The house interacts with a system that is hotter than it (the sun)...
  12. F

    Hot Cold body in contact, what happens with heat and temperature?

    Homework Statement A hot body is brought into contact with a colder body until their temperatures are the same. Assume that no other bodies are around. 1.Is the heat lost by one body equal to the hear gained by the other? 2.Is the temp drop of one body equal to the temp increase of the...
  13. quasar987

    Why Does Wind Make a Cold Day Feel Even Colder?

    A windy 0 °C day perceived as colder than a 0 °C day without wind. I find that strange, given that wind is just air particles with kinetic energy. When those speedy particle hit a body, they should give off some of their energy to that body in the form of heat. But instead cold is perceived by...
  14. R

    Photosythesis in a cold climate

    Is there a listing of the mimimum light levels that edible vegetables need to commence photosynthesis? Is there a listing of such light levels, season by season, worldwide, and specifically for UK? Background of question Wish to see if plausible to construct, here in UK, Solar Greenhouse...
  15. M

    Can a PTC thermistor prevent overheating in a DIY speaker heater?

    Hi My brother has a logitech pure fi anytime alarm clock radio. The problem with it is that when it is cold the speakers do not work properly distorting the sound. This is not very useful as it is cold in the mornings when the alarm goes off (playing a song from the ipod). Now I had an...
  16. G

    Can Cold Temperatures Improve Vacuum Infusion for Fiberglassing?

    I've been reading up on vacuum infusion for fiberglass. The big problem is getting the resin to flow over a part completely before curing. Viscosity lowering additives can only be used at a minimum due to decreases in the strength that are undesirable. One solution is to heat a slow curing resin...
  17. W

    Calculating the Dielectric Constant of Cold Dilute Rubidium Gas

    assume that i have a cloud of cold dilute Rubidium atoms i know the atomic levels of the Rubidium atom How to calculate the dielectric constant of this gas? Which book can i consult?
  18. K

    60 minutes: Cold fusion is hot again

    http://www.cbsnews.com/video/watch/?id=4955212n So, what should one make of this? I would love to hear what people here with physics know-how think about both the people and the experiments. k
  19. S

    Schools Is Cold Calling a Useful Strategy for Grad School Admissions?

    Hey, So I don't have that much of a competitive GPA. I'm wondering how much useful it is to call some schools by phone before sending the application? As in, to make a short yet detailed call about why they should consider my application by having other strong components (such as work...
  20. D

    Cold air vs hot air in turbochargers

    Okay so i have a project, and this is pretty basic physics but I'm kind of confused. so for those of you how a turbo work, please help me out here. okay so: pV = nKT in thermodynamics. so in a turbo, as air enters the compressor turbine, n and k stay constant correct? however as air enters the...
  21. G

    Cold Fusion: US Navy makes breakthrough?

    http://news.yahoo.com/s/afp/20090324/ts_alt_afp/usscienceenergynuclear I guess we'll have to wait and see... Looks like it is being presented at the spring ACS meeting right now.
  22. R

    Keeping Your Dog Safe in Cold Weather: Doghouses with Heat Generators

    1. Do you own a dog? 2. Is your dog ever in cold weather? 3. Does he have a doghouse with a heat generator? 4. Is your dog outside for extended periods of time?
  23. wolram

    Cold water tastes better than warm

    To me cold water tastes nice, but leave it for a few minutes to warm (slightly) and it tastes horrible, is this just my taste, or do you find the same, if yes why does it taste different?
  24. C

    Is Cold a Universal Phenomenon in Space?

    Does what we as humans consider "cold" travel through space like heat does? Could a planet have moons that are cold because the planet itself is cold? I know cold is really just air, but could it somehow travel from one astronomical body to another?
  25. A

    Minty Freshness: Why Does It Feel Cold?

    Why does the mint flavore make your mouth feel cold? I thought it might be chemistry.
  26. Redbelly98

    How Cold is It? Share Your Best Line!

    "How cold is it?" Heard this bit on NPR radio today, reminiscent of the old Johnny Carson and Ed McMahon exchanges: "It's really cold." "How cold is it?" "It's so cold that ... " ... and the idea is to complete the statement. Here are a couple they played on the NPR bit: "It's so...
  27. A

    Cold Weather Makes Snow Squeak: The Science Behind It

    Right now it's a bit chilly in the upper midwest (-21 degrees this morning at 6:00 am; -23 degrees predicted for tonight). When walking our dog this afternoon, my wife and I noticed that the snow underfoot squeaked louder that usual. We observe that snow makes a qualitatively different sound...
  28. wolram

    Is the CDM particle still elusive?

    http://cdms.berkeley.edu From the discussion in APS Viewpoints. The two experiments taken together—XENON10 superior at lower masses and CDMS II at higher—are now encroaching well into the region where discovery may be lurking, a marvelous feat considering that a scattering cross section of...
  29. wolram

    Why Is Extreme Cold Causing Chaos in England and Power Outages in the US?

    For England that is, it is not often we gets this brass monkeys, looking out at the jack i saw one poor tin lid fall on his queen mum, it is minus 10c and jack has layed a carpet about 1/4 inch thick every where, dad had a minor operation canceled because of an influx of accidents, and a local...
  30. T

    Why do batteries loose omph when it gets cold?

    Why do batteries loose "omph" when it gets cold? Simple question really; It's well known that car batteries (and others) don't work as well when the temperature approaches -20C. I'm just wondering why? What's the physical reason? Also, if you bring the battery back to room temperature, will it...
  31. D

    Waiting for Winter: Graduate School Applications

    My applications to graduate school have been complete for a while, but now that fall semester is over it really feels like I'm waiting. AHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH! Anybody else going crazy?
  32. N

    Can Extreme Cold Cause Burns Similar to Heat?

    Hi, I was wondering, what is a cold burn exactly? We were told that liquid nitrogen (or anything that cold for that matter) can cause cold burns when touched... How can something cold burn you? Or is it not burning you but is it merely named 'cold burn' even though it is simply freezing...
  33. J

    Oil Heater, Humididy, Heating Cold Air

    Hi I am living in a 2 bedroom house with base bord heaters but i have also purchesed 3 oil space heaters, my landlord since has givin me a bogus eviction notice because of to much humididiy in the air, his fault really for nothin ensuring propor ventalation when repairing the house but my...
  34. X

    Can a 17-Year-Old Pioneer Cold Fusion Breakthroughs?

    Most of us have heard about it. Some of us know a little about it. Little understand it. I am a 17 year old student, competant in the science and maths, (not to toot my own horn, but it is my best area) Is there a physician (no? physicist (damn that word doesn't look right, oh well, you...
  35. N

    Twice as Hot/Cold? What Does That Mean?

    Hi, I was just wondering, if you say "The temperature today was twice as hot as it was yesterday", in which units are people usually referring? Degrees Celsius doesn't make any sense, since it is perfectly possible for something to be twice as hot or cold as 0C... For the same reason I don't...
  36. rootX

    How we get cold and how to avoid it

    For past few years/for all my life I have found that I realize I have cold only when I wake up (in the morning time). It comes all of sudden. I never successfully pinned down what caused it. I usually blame the things that I ate in my dinner. I am again in standard cycle. I woke up and...
  37. P

    Understanding Mouse Behavior in Cold Weather: Causes and Implications

    I have observed that the mice seem afraid of cold weather. They run into warm or hot regions when possible and go back when the tepurature incerase. What controls their activity actually ? Is it sexual urge for mating within the cold duration or fears of cold which might cause sense nerve...
  38. D

    Can Entropy Explain the Cold Temperatures of Outer Space?

    I was wondering why temperatures are so low out there in the vacuum of outer space? my understanding is that a thermometer works by interacting with the medium in which it's located. So when we are in a vacuum, there is nothing to interact with our thermometer to give off or absorb heat. So I...
  39. D

    Is Cold Fusion Finally Proven? New Demonstration Raises Hopes for Clean Energy

    http://www.physorg.com/news131101595.html "Now, esteemed Physics Professor Yoshiaki Arata of Osaka University in Japan claims to have made the first successful demonstration of cold fusion. Last Thursday, May 22, Arata and his colleague Yue-Chang Zhang of Shianghai Jiotong University presented...
  40. S

    Is Cold Fusion for real this time?

    http://physicsworld.com/blog/2008/05/coldfusion_demonstration_a_suc_1.html hey, it's physicsworld.com ...so what's up, anyone got some info?
  41. M

    Is the velocity of a bunsen burner flame proportional to the cold flow velocity?

    Homework Statement Is the velocity of a bunsen burner flame proportional to the cold flow velocity? Homework Equations S = Usin a Where S = flame velocity U = cold flow velocity a = half cone angle The Attempt at a Solution I took numerous photographs...
  42. C

    WMAP cold spot and void in the universe

    I'm doing a research paper on the supervoid found in the constellation Eridanus and it was discovered by WMAP which recorded a cold spot where the hole is ... I just don't know why a drop in temperature of the CMB radiation indicates a hole... can anyone explain please?
  43. S

    Roofing felt bubbled up because of cold weather?

    Recently I was helping a friend of mine nail sheets of felt on a roof, and we finished applying the felt in the afternoon when it was warm. We came back the next morning to nail the shingles on the roof, and the felt was bubbled up. It about 20 degrees colder that morning than it was the...
  44. J

    Exploring Cold Fusion and Electrolysis: A Beginner's Journey

    Hi I am by no means an expert nor have I even ever taken a class on physics. I have always been interested on such subjects however. Here is my question. I am doing research on electrolysis and found something interesting on a wikipedia with regards to cold fusion. "Cold fusion...
  45. C

    Medical Cold Medicine: Effects on Immunity?

    Is it true that cold medicines turns off your natural immunities to cold and take control of your body? and when you take cold medicines often you easily catch cold?
  46. Q

    A few questions about atoms splitting and some about cold fusion

    A few questions about atoms splitting and some about "cold fusion" Ok first I was thinking, when atoms fuse, they release energy, when an atom is split... it releases energy. Now, since energy is not created nor destroyed but only transferers, if you fuse an atom and then split it again, what...
  47. 5

    Hot gases flow better than cold gases why?

    I have read that hot gases flow better than cold gases. Why is this so? Less dense? Any good readings on it. I am thinking of incoming intake charge (cool) in an engine, and the outgoing (hot) gases. Thanks.
  48. A

    Understanding the Cold Black Sun and Its Mysteries in Space

    Hello All, Please excuse my ignorance. I have a number of questions about the sun. Space is cold, yes, very very cold, close to absolute Zero. I have heard the argument that it is solar radiation or through convection that the heat from the sun reaches us. However I still can't get my head...
  49. tandoorichicken

    Powering a Cold Box Under $100: Ideas & Solutions

    Hello all, I'm having a bit of a problem on a class design project. We have to design a mini-fridge for developing coutries that runs on its own power and must cost under $100 ideally (it can go over if necessary). My group decided to use a hand-crank powered thermoelectric module and fan...
  50. N

    Stargazing Catching the Eclipse Last Night: A Tale of Cold and Clear Skies

    Did anyone else catch the eclipse last night? I drug out the Dob around 9:30 and watched until 11:15 or so. It was brutally cold but totally cloudless and clear for most of the night. Saturn was right there too, at opposition I believe; so I got some good views of it too. I took a bunch of...
Back
Top