Mar 25, Nov 21, Mar 24, Oct 10, Recommended for you. First observation of an inhomogeneous electron charge distribution on an atom 21 hours ago. Nuclear radiation used to transmit digital data wirelessly Nov 10, Load comments Let us know if there is a problem with our content. Your message to the editors. Your email only if you want to be contacted back. Send Feedback. Thank you for taking time to provide your feedback to the editors.
E-mail the story Does light experience time? Your friend's email. Your email. I would like to subscribe to Science X Newsletter. Learn more. Your name. Note Your email address is used only to let the recipient know who sent the email. Your message. Your Privacy This site uses cookies to assist with navigation, analyse your use of our services, collect data for ads personalisation and provide content from third parties. Left The firecrackers are sitting still and as the cloudthing whips past they explode.
The explosions are in different places. Right The exact same situation, but with the cloudthing sitting still and the firecrackers exploding in the same place as they pass it. In both diagrams time points in the upward direction. The important thing is that a given object will take up a given amount of space have a set size that everything can agree on, and will experience the same amount of time as everything else.
In Galilean relativity, the size of objects, the distance between two events that happen at the same time, and time itself are all fixed. So the dude on the boat and the dude on the shore will always agree on what time it is, as well as how far apart they are at any moment. That extra rule has a lot of weird consequences that you have to be some kind of Einstein to figure out.
In a single reference frame from the perspective of anything moving at the same speed as the particular object everything has a size and a position and a time.
The unfortunate thing is that as soon as you look at the same things from a different reference frame, sizes, positions, times, and durations all change. So finally, to the point. Not even that! Is it possible to transform that information to a different reference frame by a linear function?
Is it like the change of bases? Or is this nonsense? His opinion is that space cannot be an empty stage absolute space any more than a sentence can remain a sentence with all the words removed. It would simply be a part of the continuum. Even more so the dimension we were using to measure it by. To say that we may not think of time and distance in regarding such an empty universe is to beg the question, surely.
And the words in the sentence analogy fails because a sentence has no dimensions beyond its words — unless you include the paper it was written on. Otherwise, what is the effect? What are we measuring?
What assumptions can be made about a planet whose day is equivalent to earth days? Pretty much any planet can turn at pretty much any speed. Hi, nice website. Would you be able to expand on the topic by reference to the thermodynamic arrow of time entropy at all? If all the matter in the universe were to suddenly disappear, there would be no moving particles to infer time from?
For instance, even if we knew that all the matter in the universe was about to disappear, we could calculate the interval between the point in space time where I posted this comment and the point in space time at which the next president would have been sworn in.
Hopefully we would find better things to do with our remaining time, but in an SR universe that calculation would be possible. And vice-versa, how could you have the bodies without the space in which they may exist in. Either one is impossible without the other it seems.
SM, do you think the following alternative question sheds any light on the original? That may not be obvious from looking at the chart, but you know it has to be true because you could reverse the process. So the chart is highly ordered.
This is what it means for the cities to be situated within space. Spatial coordinates are a highly economical way of capturing the possible mutual relations among things. In the above example, we had 20 cities and intercity distances that reduce to 55 unique numbers.
The more things you have, the more impressive the savings are. For cities, the chart contains 10, intercity distances, reducing to numbers.
The reason the compression is so powerful is locality. Locality means that the whole is the sum of its spatial parts, and in this context, that means every journey is a series of smaller steps. These data put Salt Lake City in two different places, depending on whether you drive straight from Dallas or stop off in Denver. Under such circumstances, position becomes meaningless.
Space becomes meaningless. When I first drove in Boston, I had to learn to distrust my spatial awareness, because it kept getting me lost. To a driver, Boston is a nonspatial city. This is the case, after all, for human relationships. Our social lives are too tangled to be laid out on a spatial map. Family trees translate genetic and conjugal closeness into spatial closeness, and online social networks have spawned similar attempts. The Wolfram Alpha website, for example, used to be able to map out your Facebook friends network, using dots to symbolize your friends and lines to connect those who have friended each other.
Typically, your friends cluster into distinct social circles: family, classmates, workmates, ultimate Frisbee teammates, fellow Radiohead groupies, and so on. If these people go to the same party, they might congregate in different corners of the room, and the figurative distance between them translates into literal distance.
Finding unexpected connections is half the fun of these graphs, but does expose the limitations of the spatial metaphor. Like Salt Lake City in the above example, he occupies two different places, corresponding to two social circles. And the failure deepens when you consider everything these graphs leave off. One person might have an unrequited crush on the other, and still a line connects them. To capture these other dimensions of human relationships, you can festoon family trees with symbols: thick line for a close bond, zigzags for hostility, and so on.
Such diagrams, known as genograms, are popular among psychologists, social workers, and people struggling to follow Game of Thrones. The symbols compensate for the failure of the spatial metaphor. In some cases, people organize themselves so that their social network becomes radically streamlined, and these situations let us see how space might emerge from spacelessness. A structure can form where none existed before. That can happen in two ways: Build up or cut back.
People might start as atomized individuals who begin interacting, like your grandmother who finally got on Facebook and signs up all her friends. The army, for example, restricts socializing across ranks, on the assumption that familiarity might breed contempt. Consequently, difference in rank is analogous to spatial separation: A private is distant from a colonel in much the same way that Dallas is distant from Salt Lake City. Information flows up and down the chain of command just as a person driving from Dallas to Salt Lake City must pass through intermediate points.
Because of this structure, a military hierarchical chart is a fair representation of social relations in the military. A classic example is the market economy. And in a sense it is, because collective arrangements transcend the people who create them. Price becomes important when people come together and trade. Depending on their haggling skills, the price varies from person to person and place to place.
Some plucky entrepreneur takes advantage of these variations to buy low and sell high; in so doing, that person helps to even out the supply and therefore harmonize the prices. This kind of self-organizing happens all the time in physics. For instance, a single water molecule has no temperature. Temperature becomes meaningful when molecules collide and exchange energy. If you mix cold and hot water, the cold warms up, the hot cools off, until they equalize. Before equilibrium, the water is characterized by two temperatures; afterward, by a single value.
From complexity comes simplicity. The complexity remains latent, though. Physicists commonly use these deviations from standard behavior as windows into the microscopic composition of materials. The same might go for space, too. The basic building blocks of nature might be capable of a tangle of relationships that would fill a celebrity gossip rag. Through some organizing mechanism or simply the play of averages, those relationships become regimented, so that they can be laid out on a spatial grid and interact only in strictly prescribed ways.
In situations such as black holes, the system can become disordered and events can cease to have a position or a time. And even when the system is spatial, it contains a vast amount of latent complexity. The universe we see playing out in space may be just the surface level, where we float like little boats while leviathans stir in the deep.
T he concept of space as a network goes back to the s and the brainstorms of such innovative and iconoclastic theorists as John Wheeler, David Bohm, Roger Penrose, and David Finkelstein. Physicists have been trying to make the idea work for decades. Today one of its strongest champions is Fotini Markopoulou, who pictures the stringing-together process as a graph akin to those Facebook diagrams. Quantum graphity is a theory-in-miniature that focuses narrowly on what you might build with those grains.
After all, physicists have found that similar rules govern a huge diversity of complex systems, from earthquakes to ecosystems to economies. On the downside, quantum graphity is so bare-bones that it faces the problem of meshing with known physics. This thing has no notion of locality G is the gravitational constant, which has the same value throughout our universe. Einstein's theory of relativity adds to this. His theory predicted that objects with great mass deform space around them, causing light to deflect into them.
That has been shown to be true. He also predicted that gravity could travel in gravity waves, which we haven't seen yet. None of this explains why mass or distance affects gravity, though.
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