h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Ok. I hate to do this, but frivolity is my nature. In this cosmicpolitan-fuelled moment I finally chose to read this thread and it's given me HOPE!

Based on a (grantedly haphazard) perusal I'm under the impression that since the universe is expanding that's an excuse for my *ahem* maternal backside to do the same, and I might as well just give in to it.. Cool! As long as I encase it in spandexI oughta be just fine.

Did the expansion of your rear end start with a Big Bang too?

the reason why i think theres sides is that is it expanding, a baloon expands you can see the ouside, how could the universe expand without this, there must be something inbetween the universe and watever its expanding into, this leads me to another question, not totaly related to this thread but, how many people can imagine nothing? if the universe was never created what would it look like, i find this hard to imagine, because you there would be nothing to know what it does look like

The universe isn't expanding into anything. It's just expanding, so that things which are close together now are later further apart. This is possible in an infinite unbounded universe as well as a finite unbounded one.

jfw

Light is the term used to describe all electromagnetic radiation.
Go here and have a look http://imagine.gsfc.nasa.gov/docs/science/know_l1/emspectrum.html.

Sound waves are different in that the energy of sound is carried through a medium such as air or water in compression fronts which look like waves if you view them in one plane.

Light, on the other hand behaves like a wave but also has features of a particle, the Photon. The Photon is a particle with no mass and a spin of 1. It can also be defined as a packet or quantum of energy.

Here is some light (pun intended!) reading for you.
http://atschool.eduweb.co.uk/rmext04/92andwed/pf_quant.html

turvy

Jonny Central.

If the universe had never come into existance it would not look like anything and we would not be here to worry about it!

turvy

Thanks turvy!
The links were a big help.

"Radio waves, visible light, X-rays, and all the other parts of the electromagnetic spectrum are fundamentally the same thing. They are all electromagnetic radiation."

So they really are all considered 'light' and travel at 186,000 mps (in a vacuum). But they all have different properties and these can be measured in three ways:

"..frequency is measured in cycles per second (which is called a Hertz), wavelength is measured in meters, and energy is measured in electron volts."

Given that there are so many variances in the properties of all forms of 'electromagnetic energy' I guess I'm still not convinced that they travel at exactly the same speed. Unless there is some as yet unidentified property common to them all which makes this 'radiant velocity' of 185,000mps an invariable constant. Fascinating stuff which requires a mathematical imagination. Most of it is way beyond my abilities.

I would have thought that 'frequency' for example would be a factor of speed and 'wavelength' a variable of range. The frequency of sound is known to limit its range and percieved volume and I keep thinking that light has 'physical' properties which would make it behave like sound thru a medium. There is some evidence that this might be true of 'light' energies. The fact that:

"Electromagnetic radiation from space is unable to reach the surface of the Earth except at a very few wavelengths, such as the visible spectrum and radio frequencies."
seems to suggest that all energy waves can be impeded or obstructed (either absored or deflected) by mass (matter).

Even the relatively narrow band of 'visible light' has dozens of spectral frequencies and wavelengths (colours). To me this suggests that, like visible light thru the earth's atmosphere, their progress thru some media (other than a theoretical vacuum) would be slowed or their energy diffused. If this were true of all EM energy then perhaps it could be regulated and redirected in the same way we now regulate redirect radio (and tv) waves to produce signals which can be re-interpreted.

Obviously, there is still much to learn about these energy forms which we have only just discovered in the last century or so. No doubt there will be further discoveries. Not just of other forms of energy but also other forms of matter and anti-matter which might give us ways to manipulate the properties of these energies.

thanks again,

~jwf~

.

Talking of vacuums. If a body, say a particle, is travelling through a vacuum and another is travelling in the same direction, but 100,000 miles to the left of the first particle. Where are they? Two things with nothing in between them must be next to each other?
Hey, we could revive the old 'Ether' theory...

All electromagnetic radiation (e.g. radio waves, infra-red, gamma rays, microwaves, gamma waves, visible light etc.) travels at the same speed--almost 300 000 km/s (the speed of "light", c).

There's no agreement about whether the Universe is infinite or not. However, the visible Universe had a radius of about 15 billion (*10^9) light years--because the Universe is about 15 billion years old so no light from further away can reach us yet.

Light doesn't need any medium to travel through. Although they used to think it traveled through the ether.