temperature

Rising temperatures and high carbon dioxide emissions are the means through which humans are inadvertently causing the decline of several species. But one animal actively uses both heat and carbon dioxide as murderous weapons - the unassuming honeybee. With their stings and numbers, bees already seem to be well-defended but they are completely outgunned by giant hornets (right). These two-inch long monsters are three times longer than several times heavier than tiny honeybees and raiding parties can decimate entire hives. European bees mount little in the way of an effective defence, but…
For humans, sex is a simple matter of chromosomes: two Xs and we become female; one X and a Y and we develop into males. But things aren't so straightforward for many lizards - many studies have found that the temperature of the nest also has a say, even overriding the influence of the chromosomes. But the full story of how the lizard got its sex is even more complicated. For at least one species, the size of its egg also plays a role, with larger eggs producing females, and smaller ones yielding males. The discovery comes from Richard Shine's group at the University of Sydney. In earlier…
I already talked about increasing the temperature of a pool. My father commented that he thought the pool level rose by like half an inch when the temperature increased (by about 10 degrees F). So, this leaves the question: Is my father crazy, or is this possible? Or are both true? Does water expand when it warms up? Yes, except when it melts. Why does this happen? Liquids are actually very complicated, but here is a basic answer. Take a look at this PhET gas simulator, I know it is for gases not liquids. I think we can make it behave like a liquid if you increase the gravity to the…
There are some really cool questions out there. Questions that do not require a lot to ask and do not require a lot to answer. Here is one such question (I can't remember where I first found this question or something like it): Suppose you put take two identical cans of soda out of the fridge and place them on the floor in the middle of a room. One can you leave alone and one can you cover with a wool blanket. After an hour, you come back and check on the two cans of soda. Which will be warmer? First, why do I like this question? Mainly because everyone can give an answer. If asked…
Temperature is a pretty weird thing if you think about it. How do you best define temperature? Let me go ahead and give you my favorite definition: Temperature is the thing that two objects have in common when they have been in contact for a long time. Yes, that is a good definition. Maybe now you can see why temperature is weird. Doesn't it have something to do with energy? Well, something - yes. Let me take an example. Suppose pour some hot coffee into a paper cup (I use paper because styrofoam(TM) is trademarked). Further suppose that this is super hot coffee from McDonald's. Can…
I am sorry to point this out, but I can't help it. My kids watch this show "Fetch with Ruff Ruffman". It's mostly an ok kids show. However, there was a problem. In one episode, some kids were in the desert and measuring temperature with (they said it several times and it was even a quiz question at the end) - a LASER. Here is the device they used: ![Images](http://scienceblogs.com/dotphysics/wp-content/uploads/2008/10/images.jpg) This is an infrared thermometer with a LASER aiming system. The laser is only there to help you aim. The temperature is determined by measuring the infrared…
Heat. You have heard it before. You have used it. I have even used it. Do we need this word? No. Is this a useful word? No. Let me start with the definition as usually stated in a physics type text: (this is from [dictionary.com](http://dictionary.reference.com/browse/heat)) *heat:* a nonmechanical energy transfer with reference to a temperature difference between a system and its surroundings or between two parts of the same system. This definition is fine. It is not wrong, but is it needed? Not really. Couldn't we just say energy transfer? Actually, I like to use this in the…
Some of you who've been following astronomy for awhile might remember this report, where a group of astronomers reported finding a giant "void" in the Universe. What is a void? Well, galaxies are distributed pretty randomly, but because of gravity, they cluster together. A small example is our local group which looks like this, and a larger example is the Virgo cluster, which is about 1,000 times as massive as our local group, and looks like this: Well, a void is the opposite of a cluster, where you have a large volume of space that's simply empty of galaxies and matter. This press release…
When I think of molecules, I think of Conan O'Brien doing his skit where he plays Moleculo... the molecular man! I don't think of astronomy, and I certainly don't think of the leftover radiation from the big bang (known as the cosmic microwave background)! But somebody over at the European Southern Observatory put these two together and made an incredibly tasty science sandwich. See, we can measure the cosmic microwave background today, because we have photons (particles of light) coming at us in all directions at all locations, with a temperature of 2.725 Kelvin. Theoretical cosmology…
This is just one of dozens of responses to common climate change denial arguments, which can all be found at How to Talk to a Climate Sceptic. Objection: Today's warming is just a recovery from the Little Ice Age. Answer: The problem with this argument is that it relies on an implicit assumption that there is some particular climate that the earth needs to be at and that given a period of globally lower temperatures, an eventual rise is inevitable. What is the scientific basis for such an assumption? There is no evidence that such a situation exists. The climate is influenced by many factors…
This is just one of dozens of responses to common climate change denial arguments, which can all be found at How to Talk to a Climate Sceptic. Objection: Some stations, in the US for example, show cooling trends. If there really were global warming, it would be warming everywhere. Answer: Global Warming refers to the long term increase in globally and seasonally averaged surface temperatures. It is not the case, nor is it expected, that all regions, let alone all weather stations, on the globe will show the same changes in temperature or rainfall patterns. There are in fact many stations…
This is just one of dozens of responses to common climate change denial arguments, which can all be found at How to Talk to a Climate Sceptic. Objection: Climate science can't even fully explain why the climate did what it did in the past. How can they then claim they know what is going on today? Answer: There are two requirements for understanding what happened at a particular climate change in geological history. One is an internally consistent theory based on physical principles and the other is sufficient data to determine the physical properties involved. It is very hard, in some cases…
This is just one of dozens of responses to common climate change denial arguments, which can all be found at How to Talk to a Climate Sceptic. Objection: In the geological record it is clear that CO2 does not trigger climate changes. Why should it be any different now? Answer: Given the fact that the human species and our industrialization is rather unique in the history of planet Earth, do we really need to see some kind of historical precedent for CO2 triggered climate change before accepting what we observe today? Surely unprecedented consequences are not far fetched in the face of…
This is just one of dozens of responses to common climate change denial arguments, which can all be found at How to Talk to a Climate Sceptic. Objection: Global temperatures have been trending down since 1998. Global Warming is over. Answer: At the time, 1998 was a record high year in both the CRU and the NASA GISS analysis.  In fact, it was not just a record year, it blew away the previous record by .2oC. (That previous record went all the way back to 1997, by the way!) According to NASA, it was elevated far above the trend line because 1998 was the year of the strongest El Nino of the…
This is just one of dozens of responses to common climate change denial arguments, which can all be found at How to Talk to a Climate Sceptic. Objection: Global Warming has been going on for the last 20,000 years. Answer: It is quite true that 20Kyr ago the temperature was some 8 to 10oC colder than it is today, but it is highly arbitrary and dubious to simply draw a line from that point to today and say "Look! 20K years of Global Warming!". If you have look at this nice graph of temperature starting at a point when we were finishing the climb out of deep glaciation, you can clearly see that…
This is just one of dozens of responses to common climate change denial arguments, which can all be found at How to Talk to a Climate Sceptic. Objection: Newfoundland was so warm in the Medieval Warm Period that when the Vikings landed they called it Vineland and brought boatloads of grapes back to Europe. Answer: One can not infer a global climate from an anecdote about a single region, or even a few regions, you need detailed analysis of proxy climate indicators from around the world. These proxy reconstructions have shown that the Medieval Warm Period (around the time the Vikings were…
This is just one of dozens of responses to common climate change denial arguments, which can all be found at How to Talk to a Climate Sceptic. Objection: Greenland used to be a lovely hospitable island when the Vikings settled it. It was not until the Little Ice Age that it got so cold they abandoned it. During that time, it was clearly not the frozen wasteland it is today. Answer: Firstly, Greenland is just a part of a single region and as such can not be assumed to represent any kind of global climate shift. See the article on the Medieval Warm Period for a global perspective on this time…
This is just one of dozens of responses to common climate change denial arguments, which can all be found at How to Talk to a Climate Sceptic. Objection: If you look back over the last 600 million years you see that there really is not much correlation between temperatures and CO2 levels. Clearly CO2 is not a climate driver. Answer: While there are indeed poorly understood ancient climates and rather controversial climate changes in Earth's long geological history, there are no clear contradictions to greenhouse theory to be found. What we do have is an unfortunate lack of comprehensive and…
This is just one of dozens of responses to common climate change denial arguments, which can all be found at How to Talk to a Climate Sceptic. Objection: There was global cooling in the 40's, 50's and 60's even while human Greenhouse gas emissions were rising. Clearly, temperature is not being driven by CO2. Answer: None of the advocates of the theory of Anthropogenic Global Warming claim that CO2 is the only factor controlling temperature in the ocean-atmosphere climate system. It is a large and complex system, responsive on many different timescales, and subject to numerous forcings. AGW…
This is just one of dozens of responses to common climate change denial arguments, which can all be found at How to Talk to a Climate Sceptic. Objection: Satellite readings, which are much more accurate, show that the earth is in fact cooling. Some very old news here, that's all. I wonder how long before this one stops being brought up? Answer: There are a few advantages to the satellite readings, mainly the more uniform global coverage and the fact that readings can be taken at different altitudes.  However, it is in fact a very complicated process which uses microwaves emitted by the…