A thought on relativity.

[Colby]

Relativity says that as your speed in three dimensions rises, your speed in the fourth dimension falls. I'm wondering if maybe there's some sort of equation for this, someyhing like f(space_acceleration)+g(time_acceleration)=constan t. Any thoughts?

[Tormod]

Originally Posted by Colby

Relativity says that as your speed in three dimensions rises, your speed in the fourth dimension falls.

Where did you read this? I was not aware that relativity separates time from space. The whole point of relativity is that time and space is two aspects of the same thing.

What you are talking about, though, is time dilation. Try searching for time dilation here at Hypography, it should yield quite a few topics.

[Janus]

Colby might be thinking about "four velocity". This is a vector in space-time, in three spatial dimensions and one time dimension. The length of this vector is invarient.
For an object "at rest" this vector points entirely in the "time" direction. From a frame where the object has a relative motion, this vector rotates into the spacial dimensions, and thus extends a shorter distance into the time dimension and now extends into the spatial dimension. IOW, its four-velocity in the time direction decreases as its four velocity increases in the the spatial dimensions.

This has been used to describe the Lorentz tranformations as the result of rotation in space-time.

[UncleAl]

He's thinking of conserved ds^2, the metric. If the spatial terms get bigger the temporal term must decrease to retain the identity. As in the Twin Paradox, the twin that moves through the most space accumulates the least time.

[Colby]

Originally Posted by Tormod

Where did you read this? I was not aware that relativity separates time from space. The whole point of relativity is that time and space is two aspects of the same thing.

What you are talking about, though, is time dilation. Try searching for time dilation here at Hypography, it should yield quite a few topics.

You are correct, I was referring to time dilation. What I'm thinking of is a function involving your velocity in space and your velocity in time (i.e., as your space velocity rises, your time velocity falls). Seemed like an odd way of looking at it, was just a thought.

[Qfwfq]

Janus is correct and Unc is wrong. Colby used improper terminology - "speed in the fourth dimension" - but of course he's asking a question with the aim of understanding.

Yes, it's what's behind time dilatation. Four-velocity is usually written as u and it's the derivative of coordinates wrt proper time. Its length squared is:

[Farsight]

If I might offer something in layman's language:

Basically, everything always moves at the speed of light through spacetime. I'm not moving in a space direction. But I am moving in the time direction. At the other end of the scale, a photon travels at the speed of light in a space direction, but doesn't travel in the time direction. No time passes for a photon, it's moving at "the speed of light". Only it isn't really the speed of light, because a photon is light, and light is really a dimensional disturbance rippling through spacetime. So the speed of light is really the speed at which things happen. And things happen. They don't happen faster or any slower. They just happen, and that's why the speed of light is really the speed of time. So, you're sitting at your computer screen doing 300,000 km/s, and if you weren't, nothing would be happening. Kinda. Something like that.

[HappytheStripper]

E=mc then squared .. basically the energy is .. the mass of light matter .. contained within that one reference point .. and then squared off .. to contain it .. stating that everything inside that square is relative to all 4 dimensions of this square .. time/space and mass/matter

Time divided space .. and mass divided matter .. and condensed .. they essentially became one as they could not survive without the other ..

He then theorised if everything in this square is relative .. then so should be everything else outside that square ..

Imagine the Earth as being contained within that square .. over the centuries .. man has shed light on the mass of matter contained within the Earth ..

Imagine everything outside the square is the universe .. over the centuries we have also added light to the mass of matter we see everynight ..

Add humanity as the observer Einstein speaks of .. and the study of humans and everything is said to become relative .. from an observers point of view ..

Laymens terms ..

As for the pressure .. which rises and falls .. what goes up must come down .. especially when contained within such a small space .. just like the rain really ..

Regards

Ashley

[CraigD]

Originally Posted by HappytheStripper

E=mc then squared .. basically the energy is .. the mass of light matter .. contained within that one reference point .. and then squared off .. to contain it …

Happy appears to misunderstand the notation and precedence of operations for the well known equation
E=mc^2
. It is not
E = (m * c)^2
or
E = mc^2
, as she appears to think, but
E = m * (c^2)
, (spoken “E equals M, times C squared”).

The symbols in the equation
E = m * c^2
mean:
E: energy
=: equals
m: rest mass of the object for which energy is being calculated
*: multipled by; times
c: the speed of light (a constant, about 300,000,000 meters/second)
^: to the power of; exponentiated by (so “^2” means “to the power of 2”, and is commonly called “squared”)

It’s a convention when writing equations to assume that exponentiation is done before multiplication, and multiplication before addition – otherwise, we’d have to use parenthesis a lot, cluttering their appearance.

The word “squared” in the context of this equation means “multipled by itself”, not “2 dimensional”, “a figure with 4 equal length sides meeting at 90° angles”, or any of the many other meaning of the word “square”.

My apologies for stating these very basic terms and conventions, with which many people are intimately familiar, but the basics are very important in Physics – small misunderstandings of them can result in profound misunderstanding of its more advanced concepts.

The “mass of light” – that is, the relativistic mass of a photon – is given by 2 equations:
Energy = (Planck’s constant)*Frequency
Energy = Mass * (speed of light)^2
Which combined (and abbreviating), give:
Mass = h*f/c^2

So the “mass” of a photon of red-orange light (about 5*10^14 cycles/second) is about
5*10^14 * 6.6*10^-34 /(3*10^8)^2 = 4*10^-36 kg

This value is useful for such things as calculating the pressure that light exerts on an object like a satellite or solar sail.

[Farsight]

Happystripper: we all search for concepts that we can grasp, and doubtless some of the concepts are the wrong ones and will in time be corrected. But can we try to grasp these concepts through physics, and logic, please. Not legends.