# Design features in a spacecraft

1. Nov 8, 2004

### oheaveno

i'm stuck on my school project and the question goes like this:
design features in a spacecraft to overcome the negative effects of : time dilation, length contraction and mass increase.
thanks

2. Nov 8, 2004

### Garth

Welcome to these Forums oheaveno!
That's a hard question! Because, according to Special Relativity, as far as the space traveller is concerned, there are no such effects, everything would look normal to her. The effects you mention are only seen by the 'stay at homes' as she is travelling very fast in their frame of refeence.

However when she returns home after travelling near the speed of light she would find the 'stay at homes' had aged considerably - but she might not think that being younger than they is such a bad idea!
There is nothing you can do about it apart from travelling more slowly. (And then everybody would age) On the other hand you might want to build an 'Einstein-Rosen bridge' or 'wormhole' - have you seen the film "Contact"?

Garth

Last edited: Nov 8, 2004
3. Nov 8, 2004

### oheaveno

sorry but i dont get it

what are 'Einstein-Rosen bridge' or 'wormhole' ?!
and do you think this idea will work? (from my friends)
*spacecraft made of extremely light weighted materials so dat when mass does not increase significantly;

and i have one more question: for length contraction, does the person travelling in the spacecraft with close to the speed of light notice the other stuffz lengths have contracted?
so that they are gonna crash into stuff without knowing?
thanks

Last edited: Nov 8, 2004
4. Nov 8, 2004

### Garth

The theory of General Relativity describes gravitation as the effect of space-time being 'curved'.

Draw a straight line on a piece of rubber, say your eraser, and then bend the rubber. The line is now bent with the rubber, but it is still straight across the surface of the rubber in other words it is still the shortest distance between its two end points along that surface.

Einstein explained that when a satellite, say, goes round the Earth both the satellite and the Earth are travelling along straight (i.e. shortest) lines along a space-time surface that is curved by the presence of the Earth's mass. Think of a rubber sheet with a bowling ball in the middle. It dips in the middle, now watch an ant crawl across the dip trying to walk in a straight line, the ant's path curves towards the Ball, and if you did not know about the dip you might think the ball was pulling the ant towards it.

Now increase the mass of the ball until the rubber sheet stretches downwards vertically. This would be a good model for a Black Hole. Einstein and Rosen then added a second black hole to this back to back so the vertical tube of space-time opens out again. This is the Einstein-Rosen bridge, pop down one black hole and pop out again somewhere else and when in the universe! It is very speculative and if by some chance they do exist I would not want to try it!!

Garth

5. Nov 8, 2004

### Alkatran

I think the biggest concern is collisions with bodies moving at high speeds relative to the ship. So... get yourself a good radar.

A good analogy is this:

If you're a spaceship caption and you see another ship coming towards you at 5000 kph, how do you know if it's you or them that's moving? Who's fault is a crash?

What a nightmare for the courts.

If alien's were to ever make contact with earth, when the land their speedometers might read ".3c relative to home world" even though they're on the ground!

6. Nov 8, 2004

### oheaveno

thank you very much for your help, Garth and Alkatran. The information is very helpful
but i'm still not sure about:

(1)are there any ways to reduce the effect of mass increase besides travelling more slowly? and say if the person in the spacecraft is travelling at a speed close to light, does he actually FEEL his mass has increased?

(2)everything would seem perfectly normal to the person in the spacecraft so when length contraction occurs, the observer in an inertial frame would seem normal to the traveller too? like the observer wouldnt seem slimmer or anything?

Last edited: Nov 8, 2004
7. Nov 9, 2004

### Garth

No, as far as he is concerned it is the other person who is travelling at a speed close to light speed; velocities are relative.

At this moment we are travelling very fast, at about 1/1000 the speed of light, through the universe (relative to the surface of last scattering of the Cosmic Microwave Background) - How does it feel to you?

Once the spacecraft turned off its rocket motor both observer and traveller are in inertial frames of reference. The 'traveller' would appear "thinner" to the 'observer' and the 'observer' would appear "thinner" to the 'traveller'. Eveything in this case is relative.

Garth

Last edited: Nov 9, 2004
8. Nov 10, 2004

### oheaveno

^__^

i get it now, thanks very much :rofl: