# Special relativity and Earth in context to a stationary point

1. May 16, 2009

### gray1985

Special relativity and Earth in context to a stationary point.

If Earth is travelling around at around 1,750,204 mph then surely the time dilation caused must be significant!

Lets take the twin paradox if we could take a set of new twins, leave one on earth (child A) and managed to put the other (child B) at a point of absolute zero (hypothetically assuming that there was a point of absolute zero). What would be the relative time dilation on the twins if after 10 years from child A’s perspective had passed. Basically how much older would we (along with Child A) consider child B?

Like I say I’m interested in the time dilation we on earth go through every day and just accept as the norm!

Also does time dilation have uniform increase with velocity or does it happen at an exponential rate towards c?

2. May 16, 2009

### CompuChip

Time dilation with respect to what?

Also note that the velocity you quoted is about 0.26% of the speed of light. The time dilation factor $\gamma$ only differs from unity by about 3 x 10-6 for those speeds, which is completely negligible for almost all practical purposes.

3. May 16, 2009

### tiny-tim

Welcome to PF!

Hi gray1985! Welcome to PF!
Nooo … the Earth orbits the Sun at about 18 miles per second (about 64,000 mph), which is about 1/10,000 of the speed of light.

Time dilation would be about 1 - 1/200,000,000.
https://www.physicsforums.com/library.php?do=view_item&itemid=166"is √(1 - v2/c2), which is approximately 1 - (1/2)(v/c)2 if v is small, and approximately √(1 - v/c)(1 + v/c) ~ √2(1 - v/c) if v is nearly c.

Last edited by a moderator: Apr 24, 2017
4. May 16, 2009

### gray1985

First things first, Thanks guys for taking the time to answer

That figure 1,750,204 mph was trying to factor in all things, i.e earth spinning, earth orbiting round the sun, sun round our galaxy and the galaxy being hurtled through the universe. (I naively assume that all these will factor and dilate time in our particular frame of reference.

Allow me to try and illustrate my problem a little better.
(I would be very pleased if someone could correct my thinking,)

if we could hypothetically exist at a point in the universe where our velocity through said universe was essentially zero and compared it to say the total sum of all contributing factors that make up the figure I stated (1750,204), would child B be notably older that twin A (lets say we could compare them biologically for aging)?

Like I say I’m not an academic on relativity (so please allow for my poor use of terminologies and what I’m sure are wild amateurish statements). Relativity fascinates me and I genuinely believe (and brace yourself for a wild statement) that time dilation is in essence a form of time travel. And although I’m aware mass can never attain light speed so that time travel in practicality is far fetched, but I believe that maybe 500, 1000 10,000 years from now, breakthroughs and discoveries may open doors that we perceive as closed.

So I guess ultimately what I’m asking, if child B (space kid) has aged more over the 10 years given his frame of reference in comparison to child A on earth, then surly in a rather rudimentary fashion, the time dilatation that has occurred to child A on earth has caused it to travel further into the ‘future’ in comparison to its twin (twin B).

(note when I use the term travelled into the future I mean it solely with respect to his twin i.e twin B).

I think I’m genuinely curios as to what our given speed through the universe is doing to our frame of reference.

Many thanks

5. May 16, 2009

### Staff: Mentor

That was answered in post #2: no.

Becareful saying things like "our velocity through said universe", though - special relativity throws out the concept of absolute velocity, so this velocity you have chosen is quite arbitrary. It doesn't hold any real physical significance.

Also be careful with 'anything is possibe with technology' type statements: technology is limited by the laws of physics and as a result, some things really are not possible.

6. May 16, 2009

### JesseM

As russ said, all velocity is relative in relativity, and so is time dilation. If we ignore spacetime curvature (which makes it impossible to define an inertial reference frame over a large region of spacetime), there is some inertial frame where we are traveling at 0.99c, another where we're traveling at 0.6c, another where we're at rest, etc...and all inertial frames are treated as equally valid in special relativity.