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1548. When you traveling in a jet plane, why do objects on the ground look as though they are still or moving slowly? — K, India
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When you watch something move, what you really notice is the change in the angle at which see you it. Nearby objects don't have to be traveling fast to make you turn your head quickly to watch them go by so you perceive them as moving rapidly. An object that is heading directly toward you or away from you doesn't appear to be moving nearly as quickly because its change in angle is much smaller.

When you watch a distant object move, you don't see it change angles quickly so you perceive it as moving relatively slowly. Take the moon for example: it is moving thousands of miles an hour yet you can't see it move at all. It's just so far away that you see no angular change. And when you look down from a high-flying jet, the distant ground is changing angles slowly and therefore looks like it's not moving fast.


1549. My boyfriend and I are having this debate on whether or not to squeeze the air out of a 2 liter bottle of Coke after opening it. He thinks it will keep the Coke carbonated longer and I disagree. Who is right? — TN, Ft. Collins, CO
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Yours is actually a complicated question. After you open the soda, the CO2 dissolved in the soda is no longer in equilibrium with the gas above soda. When you cap the bottle, CO2 will gradually escape from the liquid until it forms a dense gas so that CO2 molecules from that gas return to the liquid solution as often as they leave the solution for the gas. In other words, the equilibrium between dissolved CO2 and gaseous CO2 has to be reestablished.

By shrinking the volume of gas over the soda, your boyfriend reduces the number of CO2 molecules that must enter the gas phase in order to reestablish that equilibrium. BUT, when dense gas develops in the squeezed bottle, the high pressure of that gas will reinflate the bottle to its original size. The benefits of shrinking the gas volume will thus be lost.

To succeed in keeping more of the CO2 molecules in solution, you have to make sure that the squeezed bottle stays squeeze. That's hard to do. You're probably better off pouring the soda gently into a smaller bottle, one that just barely holds all of the liquid. That smaller bottle won't expand as a dense gas of CO2 forms above the liquid soda and the soda will reestablish its equilibrium without losing too many of its dissolved CO2 molecules.


1571. How are the suffixes of websites determined? For example, why is a particular website .com or .org or .in? — D, India
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Although yours isn't a physics question, it's one that's interesting to me and easy to answer. The person who sets up the website gets to choose the domain. That's all there is to it. As long as the complete domain name hasn't already been registered, you can pay a fee and register it. For example, I chose to register this website as www.howeverythingworks.org because I feel more like an organization (of one person) than a commercial enterprise. I could have registered it as www.howeverythingworks.in, but that would imply I'm in India and I'm not. The only exception that I know of is .edu, which is restricted to educational institutions. I would not be allowed to register this website as www.howeverythingworks.edu.

Actually, I could have registered this website as www.howeverythingworks.com, but I would have had to purchase that domain name from someone else. It is registered to a cybersquatter—someone who registers a domain name in hopes of selling it at a profit to someone else. Cybersquatting was hugely popular during the internet bubble, when companies were paying vast amounts of money for particular domain names. But these days, who wants to pay thousands of dollars for a name? I'm totally happy to be www.howeverythingworks.org and I'll let someone else pay the big bucks to purchase www.howeverythingworks.com. In the meantime, that domain is just a link to advertising and an offer to sell the domain name.


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