Computer science is not an exact science.

Strictly speaking: Matter AND energy are conserved - it is the Law of Conservation of Mass AND Energy. Matter can be converted into energy (e.g. in a nuclear reactor) and energy can be converted into matter (e.g. by relativistic motion). Einstein's famous E=mc2 (which is actually a special case form of his actual, more complex, equation) links matter and energy together.

Increasing the speed of an object requires energy to increase the kinetic energy (motion) of the object but some of that energy is converted into matter which increases the mass of the object. At the speeds that we are familiar with (cars, aircraft, interplanetary space probes) that increase in mass is undetectable or at least negligible. At higher speeds, approaching the speed of light, the mass increase becomes noticeable. The increased mass means that more energy is needed to increase the speed of the object. At a point just below the speed of light the energy required to push the speed higher becomes infinite so the speed of light is the speed limit for all matter in this universe. Apologies to all Star Trek and Star Wars fans but "space warps" and "hyperspace tunnels" which will allow faster than light travel may exist but would require impossible amounts of energy to open and maintain.

Apologies to all but my undergraduate majors were in Physics and the History and Philosophy of Science.
 
At a point just below the speed of light the energy required to push the speed higher becomes infinite so the speed of light is the speed limit for all matter in this universe. Apologies to all Star Trek and Star Wars fans but "space warps" and "hyperspace tunnels" which will allow faster than light travel may exist but would require impossible amounts of energy to open and maintain.

Apologies to all but my undergraduate majors were in Physics and the History and Philosophy of Science.

I must have misunderstood, as it appears you’re saying that to travel at the speed of light takes infinite energy. So does light have ‘infinite energy’ or is this a simplification for us thickies ;)
 
Light has zero mass so it takes zero energy for light to travel at the speed of light (that sounds a bit weird!). It is only matter (i.e. objects with mass) that requires energy to accelerate to higher speed and the faster matter goes the more mass it gains so even more energy is needed to accelerate it further until it reaches the limit of the speed of light where infinite energy is required for any further speed increase.

Another source of confusion is in the "expansion of the universe" which is often stated as moving faster than the speed of light, particularly during the very early phase of expansion known as "inflation". This is referring to the "space" component of the universe, not the matter or energy components. Space is not subject to the speed of light limit. All mind blowing stuff.
 
Strictly speaking: Matter AND energy are conserved - it is the Law of Conservation of Mass AND Energy.

That's only true if spacetime isn't expanding (or contracting). Here's an annoying video in which you can learn about Noether's theorem and - as an aside - how to repeatedly mispronounce squirrel as "squirl".

When conservation of energy fails!



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That's only true if spacetime isn't expanding (or contracting). Here's an annoying video in which you can learn about Noether's theorem and - as an aside - how to repeatedly mispronounce squirrel as "squirl".

Yes, I don't know what he has against squirrels or "squirls". If he is right then they could be a major contributor to the forest fires currently burning in Europe and California.

I don't agree with his explanation that the light from the Big Bang now only appears in the microwave region of the spectrum because it has somehow "lost energy" thus disproving the conservation of energy law. I would explain the change as due to red shifting caused by the expansion of the universe since the original light was first emitted - the same reason why the light from the most distant galaxies is also red shifted. Likewise, his claim that "Dark Energy" is mysteriously increasing is hampered by the fact that we know so little (or even nothing) about dark energy, even to the point that its existence is not universally accepted. This is what makes science, and cosmology in particular, so fascinating to me.

My thoughts.
 
Pware, how far does red-shifting work and how much into red? I am curious, because we use red-shifting to determine distance of "local" stars, and the greater the red-shift the greater the distance, so does that work all the way out to the big bang? At what point has something way far away red-shifted to the point it has shifted out of red into - what? - infrared or just disappeared from the visible spectrum? Just curious because I haven't a clue. P.S. Sorry if this is a bit O.T.
 
If I understand it correctly, the oldest, most distant light we detect has been redshifted all the way from visible to the microwave part of the e/m spectrum. This is the cosmic microwave background. It has a redshift of about 1100, corresponding to just 380,000 years after the big bang.

The Webb space telescope operates in the infrared spectrum and will detect redshifts up to about 20. That corresponds to about 180 million years after the big bang.

There is a nice graph, towards the end of this Wikipedia article, showing the relationship of redshift to the distance and time that light has travelled.

https://en.m.wikipedia.org/wiki/Redshift
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Pware, how far does red-shifting work and how much into red? I am curious, because we use red-shifting to determine distance of "local" stars, and the greater the red-shift the greater the distance, so does that work all the way out to the big bang? At what point has something way far away red-shifted to the point it has shifted out of red into - what? - infrared or just disappeared from the visible spectrum? Just curious because I haven't a clue. P.S. Sorry if this is a bit O.T.


OTs, isn't that what these forums are for?:D

The red shift (moving away from us) and blue shift (moving towards us) in local stars is used to determine their velocity (relative to us). Since they are part of our own Milky Way galaxy their motion is not affected by the expansion of the universe. This also extends to our local group of galaxies. The largest galaxy in our group, Andromeda, is slightly blue shifted indicating that it is approaching us and that we will eventually collide (but I am not cancelling next weeks dinner booking). The red-blue shift in local stars is one technique that has been used to identify the presence of orbiting exo-planets.

Edwin Hubble, after whom the Hubble Telescope was named, established the relationship between the red shift and the distance to galaxies (galaxies outside our local cluster) in what became known as Hubble's Law. There has been some refining of his law since he proposed it (back in the 1920s IIRC) but it still holds true for distant galaxies. Despite its name, "Red Shift", the frequency of the light can be shifted far beyond the red or infra-red region - to the microwave region for example for the cosmic background radiation. The terms "red shift" and "blue shift" simply indicate the direction in which the frequency shift has occurred. The electromagnetic spectrum, of which visible light is just one small part, extends "indefinitely" in both directions. Beyond microwaves are short and long radio waves which can extend to hundreds of kms (and far longer) in wavelength. At the other end of the spectrum, beyond ultra-violet, are X-rays and gamma rays.

Because red and blue shift can be used to measure the velocity of "nearby" objects as well as the expansion of the universe, and by extension, the distance to "distant" objects, the latter red shift is sometimes referred to as the "cosmological red shift" to distinguish it from velocity red shift.

A cosmological red shift beyond the microwave region would indicate a distance that is beyond the current age of the universe. Strangely, such a distance is not impossible and cosmologists happily accept that there are objects from our universe that have been "pushed" by the expansion beyond the distance where we can ever observe them - like a ship disappearing beyond the ocean horizon.

Headache powder anyone?
 
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