How fast does the Speed of Light go?
ScienceDude21
Posts: 9
in Robotics
The Speed of Light goes in vacuum, commonly denoted c, is a universal physical contestant in many areas of physics. It's precise value is 299792458 metres per second (approximately 3.00x108 m/s), since the length of the metre is defined from this constant and the international standard for time.
Subdiscipline of: Physics
Related People: Albert Einstein, Leon Foucalt, Albert A. Michelson, Ole Romer, James Clark Maxwell, Hippolyte Fizeau, Christiaan Huygens, James Bradley, Edward W. Morley, Wilhelm Edward Weber, Louis Drude, Rudeolf Kohlrausch, and Albert A. Michelson.
Example: E= mc2
Subdiscipline of: Physics
Related People: Albert Einstein, Leon Foucalt, Albert A. Michelson, Ole Romer, James Clark Maxwell, Hippolyte Fizeau, Christiaan Huygens, James Bradley, Edward W. Morley, Wilhelm Edward Weber, Louis Drude, Rudeolf Kohlrausch, and Albert A. Michelson.
Example: E= mc2
Comments
Extra credit: What is the color and political affiliation of the bear?
In order to have a speed of light we need to be able to measure speed. That in turn means we need to be able to measure distance and time.
Time, the second, we get from the frequency of oscillation of whatever they use now a days. Some atomic clock or other.
Distance, the meter, if I remember correctly we get from X number of wavelengths of some spectral emission from some atomic thing or other.
On the other hand "the length of the metre is defined from this constant [the speed of light]" as wikipedia states.
As such the speed of light is actually whatever we say it is, by definition, the other units are derived from it to fit accordingly. In cosmology they often define the speed of light as 1 and work everything else accordingly. Makes calculating much easier.
There is a similar chicken and egg thing going on with the definition of mass, the kilogram. Currently the kilogram is the mass of some blob of stuff stored away in Paris. The plan is to redefine it in terms of the mass of X number of silicon atoms. Or from Planck's constant using a Watt Balance. If they do that they have to be careful the new definition does not diverge from the current standard and upset everything.
Does the barber get to shave himself when exceeding the speed of light without contradiction?
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Unless the "blob of stuff stored in Paris" is pure silicon then the new standard won't match the old standard. Just saying.
As far as I can tell the plan goes like this:
We have a standard kilogram. That blob of stuff in Paris. (I think that blob is platinum)
We can make a 1kg sphere of silicon calibrated against that blob.
Our 1Kg shere of silicon will contain N number of atoms of silicon.
We can always replicate our silicon Kg by making other ones that contain N atoms of silicon. Provided someone can count N atoms of silicon they can make a standard Kg without reference to any other blob any where. Not even the original Kg silicon Kg.
How do we know we have N atoms of silicon? Easy, make a perfect shere of silicon of a known diameter such that the volume holds N atoms.
We do that by measuring the thing with lasers and interferometry or whatever magic.
At this point we have reproducible Kilograms based on the mass of silcon atoms and wavelengths of light, We can redefine the Kg as that and throw the original platinum blob away,
Now, this new Kg may be a tiny bit different than the platinum blob but not enough to upset anything.
See "The Worlds Roundest Object"
and "Demise of the Kilogram"
Thanks VERY much, Whit - one of my most favorite people of all time!
Paul
isn't meaningful.
A nice equation: ε0 μ0 c^2 = 1, from which can be derived the density of mass-energy of a magnetic
field B as ε0/2 B^2, which is rather fun as magnetic field equations normally feature μ0 not ε0
To my ears, Speed of Light goes painfully slow and never gets to the end soon enough.
http://www.speedoflight.us/videos/
The nearest stars to us are over 4 light years away. So far our fastest space probes reach about 0.06% of the speed of light. That's about 6700 years to get there.
Assuming we can learn how to do better than that by a factor of 1000 or so we are still going to need a huge ship with a lot of resources to survive the trip. It would probably consume all the Earth's resources and economic output for some hundreds of years to do it.
Then you find there is nothing of much use or hospitable when you get there.
Nope, we are stuck to the solar system, and probably Earth until we go extinct. That's it.
Party on.
That is to say the planet Earth itself. Of course we will need to take the sun along for fuel. And probably we want to take all the planets and other rocks of the solar system for good measure.
How, we get all that lot accelerated to a useful speed across the solar system I leave as an exercise for the reader. But as we have all our resources with us we don't need to hurry so much.
This is one reason why Fermi's Paradox doesn't hold up, assuming the practicalities of other life forms are similar to ours. In the time it might take for the journey, regardless of "stasis sleep," our own history shows the passengers would likely end up killing one another before getting even halfway. Intelligence doesn't always mean smart.
Can we actually build anything like the robots you describe that will work properly for decades or centuries?
Can we be sure there is an Earth like planet in rage of this plan?
If the robots are intelligent enough to carry out this plan, build an environment, take care of the human babies and educate them as to how to survive in said new alien environment, then why bother carrying the human embryos? The robots can do it all.
I think it's like plants throwing their seeds to the wind, we would have throw millions of such projects into space. In the hope that one of them takes root some place.
It's impossible.
Currently the unit of action is Planck's constant, h, which is certainly not 1.
The speed of light was traditionally measured against a length, the length of a stick in Paris, and a time, derived from
astronomical observations. It was not a fundamental constant but something we could measure.
We can always define things the other way around. Make the speed of light is a constant, whatever we say it is, length and time
can be derived from that.
Also currently all of physics is built on measuring, and formulating rules as to what happens in space and time.
It's not clear what physics is without space and time. Although there are those who propose that is all about to change:
Nearly all stars have planets. We have discovered hundreds of planets using the Kepler telescope. Many of these are in the Goldilocks zone, where the temperature is not too hot and not too cold. It other words, it is just right for human habitation. We still don't know much about these planets. We have no idea if any of them have a breathable atmosphere. However, as time goes on we will discover more planets, and we'll gather more information about them. We may have to send out unmanned probes first to determine if there are any habitual planets within 100 light years.
We could just send intelligent robots out to colonize space, but that doesn't achieve the goal of getting humanity off of a single planet that could be destroyed by an errant asteroid. I suspect that interstellar colonization with take place in two phases. The first phase will be done by robots. After suitable planets are found, the second phase will follow that will include humans.
I think a lot of human colonies will happen in places that can't support live on it's own. Habitats will be needed to provide an artificial life support. The Moon will most likely be the first place where this will happen. The underground lava tubes on the moon are places that provide a good structure for building an artificial environment. Mars is most likely the next place that we'll colonize, and then there are some of the moons of Jupiter and Saturn.
You have to ask, "why bother"? What is the purpose of such an astronomically costly mission, when local colonization and expansion provide far more immediate benefit, and costs far less?
There's only a slight chance a human could even coexist on an earth-life planet if it has existing organisms; even simple bacteria and viruses can be deadly. They can hide across a planet surface, taking years or even decades to "discover." There would be no way for the robots to find each and every organism that poses danger, and even one could kill off the "hive." Unless some science fiction miracle comes true that reduces all sickness to mere a trifle, there's not much purpose in interstellar travel as a way to spread the human seed. Not much future if death meets us at the other end.
Apart from the ISS, which is really just a glorified space capsule, we have yet to seriously explore a single possibility of space colonization, 70 years after the proving of the first ballistic missile. We have enough to keep us busy for the next thousand years in our own Solar System.
Sad but true. I love all the sci-fi promises & pipe dreams of living off-planet, but food & resources just ain't there and likely never will be. No matter how toxic and polluted the earth gets (including another giant ELE asteroid hit and resulting multi-year ash cloud that blots out all sunlight), she will always be far friendlier and life-sustaining than any other planet/moon asteroid. Everything we need is here, just managed very poorly. Of course in time, generations & generations, everything sorts itself out. And now I must go read "A Canticle for Liebowitz" and watch "2012" again.
So, it's not a joke.
We have to understand what "action" is. So, from dimension it's energy times time. But what makes this a case? Take all the energy in the universe and all the time passed, multiply both numbers and you get an upper limit of what could happen. Don't think, what this could mean, as that took thousands of years and no end in sight.
But now look to a little detail and analyze an "action": whatever you do, you have to invest energy and time to get an result. So what make the term action looks as to be important: whenever you transfer a certain amount of energy from one system to another system, it takes time. And this time is inverse to the amount of energy. That means: high energy processes are fast, low energy processes are slow.
A well known example allows to gain a little understanding:
We say that the frequency of a photon is proportional to the energy of the photon and see the proportional factor as a constant. But see it inverse: if you catch a photon, the photon arrives at the speed of light. The lower the frequency, the longer the wavelength, the longer it takes for the photon to arrive. So the time elapsing times the energy absorbed is constant. Call a photon absorbtion an event. Then this event represents a quantum of action, as the word says: it is the smallest amount of action that can take place.
Every elementary event represents a quantum of action. High energy events, that take longer than the mimimal time h/dE are not elementary, but an acclomeration of lower energy elementary events, so they take more time to happen than the energy implies.
Time and space so are nothing then reflections of the fact, that multiple individuals exist (they can not be in one place) and that they change (the can not be different in one moment). It depends only of your point of view. Like a circle: is that geometry or algebra?
We can speculate about the convenience of defining at as 1. However I don't believe that gets us out of having to use real numbers. I'm not convince that the physicals constants c, G, k etc have nice integer relations. As soon as you get a PI or root 2 into any calculation you are in the land of the reals.
You can analyse any physical systems by looking at the action. Nature always does things in such a way as to minimize the action. The classic example of this is refraction, light will always take the path that minimizes the action.
So, for example, it used to be that we had a meter stick in Paris, we had the definition of the second from some astronomical observations. So we could measure the speed of light in meters/second based on those standards.
Or, like we do today, turn it around. Define the speed of light as some number, then derive the meter from it. The second having been redefined as X number of vibrations of some vibration of a Beryllium atom.
Like I said earlier, it's that chicken and egg thing, largely it's up to use to define which is which.
Now, no matter what you do, I'm not convinced you can reduce the relations between these physical constants in terms of integers only. Even before we start to think about PI and root two. Actually, when you do interference experiments with single photons of light, or particles like electrons, you start to come to the conclusion that there is no way they can end up where they do unless they have explored all possible paths. See Richard Feynman's lectures on YouTube where he discusses this for example.