A profound feature of relativity is that two objects passing by each other cannot have a relative velocity greater than the speed of light. An even more profound feature, one which has received much less publicity, is that the concept of "relative velocity" does not even make sense unless the objects are very close to each other.

Again, this is a question that depends on which of the many distance definitions one uses. However, if we assume that the distance of an object at time t is the distance from our position at time t to the object's position at time t measured by a set of observers moving with the expansion of the Universe, and all making their observations when they see the Universe as having age t, then the velocity (change in D per change in t) can definitely be larger than the speed of light.

The shifting of light to lower energies or longer wavelengths (toward the red if we talk about visible light) from distant galaxies is caused by their recession from us under the universal expansion. There are other ways to affect light energies but they are less strong than the expansion. In addition objects moving not perfectly in step with the expansion flow will show Doppler or ''peculiar'' velocity shifts.

Distant Starlight and the Speed of Light?????????????????????????????????????????????????? Mendelson, Jim

This depends on how you measure things, or your choice of coordinates. In one view, the spatial positions of galaxies are changing, and this causes the redshift. In another view, the galaxies are at fixed coordinates, but the distance between fixed points increases with time, and this causes the redshift. General relativity explains how to transform from one view to the other, and the observable effects like the redshift are the same in both views.

We deduce that the universe is expanding from the observation that galaxies are receding from us, and receding faster the farther away they are from us.

We observe that distant galaxies are all moving away from us: we know the distances to galaxies via various methods (the ''cosmic distance ladder''- more on that later), and we know their recessional speeds from the wavelength shift of the light from them (more on that later, too). We could interpret these observations by assuming that we ourselves are at the center of the universe, and that all the other galaxies are fleeing from us... but that would be pretty strange.

Actually, galaxies in our Local Group are moving towards us. For instance, we are on a collision course with Andromeda (not to worry, though- more on that later!) Objects nearby each other may be gravitationally attracted to each other. It's on very large scales that galaxies are flying away from each other. One billion years from now the universe will be 15 billion years old.

The wavelengths of the light emitted by distant galaxies are stretched, i.e. shifted redwards in the spectrum. We call this redshift. This is similar to the familiar Doppler effect caused by moving objects. A car moving away from you fast will have a noticeably lower pitch than a stationary car, and a car moving towards you will have a higher pitch.

Waves travel at different speeds when traveling in different materials. In the vacuum of space, light travels at 3 ? 108 m/s. If light could travel in a circular path, it would orbit the Earth 7.5 times in one second. When light encounters a denser medium, however, like that of the Earth’s atmosphere, it slows down ever so slightly to 2.91 ? 108 m/s. Upon striking water it slows down rather dramatically, to 2.25 ? 108 m/s, three quarters of its original speed.

The speed of light is 299,792,458 m/s in a vacuum. The symbol used in Relativity for the speed of light is "c", which probably stands for the Latin word "celeritas", meaning swift.

No. In Relativity, c puts an absolute limit to speed at which any object can travel, hence, nothing, no particle, no rocket, no space vehicle can go at faster-than-light (=superluminal) speeds. However, there are some cases where things appear to move at superluminal speeds, such as in the following examples: 1. Consider two spaceships moving each at 0.6c in opposite directions. For a stationary observer, the distance between both ships grows at faster-than-light speed.

Looking at commercial wireless networks in other countries is an indication of what might be possible in Australia.

Yes ... start an account for another galaxy. Otherwise, no. No communication or travel is permitted between any two galaxies. (There have been suggestions to allow this, but they have been denied)

Light is a form of electromagnetic radiation. Visible light is a narrow range of wavelengths of the electromagnetic spectrum. By measuring the wavelength or frequency of light coming from objects in the universe, we can learn something about their nature. Since we are not able to travel to a star or take samples from a galaxy, we must depend on electromagnetic radiation to carry information to us from distant objects in space.

The origin of this claim is a paper by Norman & Setterfield which plots various historical measurements of the speed of light and claims to show a steady decrease. Extrapolating backwards, they conclude that the Universe is only about 6,000 years old. This also conveniently explains how we can see stars more than 6,000 light-years away. The first point about their paper is that it was originally distributed in Stanford Research Institute covers, and is sometimes described as an SRI report.

The speed of light is constant by definition in the sense that it is independent of the reference frame of the observer. Light travels slightly slower in a transparent medium, such as water, glass, and even air.

Household water heaters heat water for washing, not for drinking. Water out of the hot tap generally has health-threatening levels of heavy metals (such as lead), as well as an off taste. You should consider this water unfit for human consumption. Incidentally, if you live in the United States in a house whose plumbing system was constructed between the 1930s and the late 1970s, it's a good idea to let the cold tap run at full for about a minute before using it.

Honestly, yes, it would be faster. So much. On a good day, if she's really on a roll, Jet Wolf can script an entire episode in three to four days. The prosing, now that's a total bitch. But the reason behind choosing to prose is very important, and not just because reading scripts is headache-inducing. When you shoot an actual episode, you have the benefit of so many little details helping you along. Camera angles, editing and transitions, music, lighting, costumes, ACTORS.

Only a few moments usually, depending on how the pilots are doing that time. We don't worry about the speed of light because we don't travel that way. Things cannot travel by movement the way you know that fast without changing into near-non-mass particles. You already figured that out years ago. Just not the other travel way quite yet.