Mars has water?

[sonofsanta]

Here's a question for you science people... On the film interstellar the dad goes to another planet and an hour on that planet is considered to be 7 years on Earth, therefore he only ages 1hour but all the people on Earth have aged 7 years. Now I know there's something about if you travel really fast time slows down. But is this all the case and if so how!?!?

 

This is the one subject that has always really confused me. Does that mean if I travel faster than the speed of light you'd go back in time? Does it mean I wouldn't age if I travelled consistently at the speed of light? I don't get it?

 

I've not seen Interstellar yet (I know, I know) but from what I gather, that planet at the end is near a supermassive black hole. Gravity warps time in the same way that speed does - if you could orbit a black hole safely, time would pass relatively slower just as if you were travelling quickly.

 

Regarding going back in time: theoretically, yes, and that may be part of why we can't go faster than light. You can't actually go at the speed of light - time would stop and the energy required is infinite - but the closer you get, you would age slower relative to people back home, yes. You'd still age normally as far as you're concerned - your frame of reference would be stationary - but if you returned home then millennia might have passed. You'd still be, relatively speaking, only 30 years old, but in absolute Earth terms you might be 4,000.

 

Time is weird, though; most equations in physics don't actually need it, and why we experience time in the linear fashion we do (the arrow of time) is a rather embarassing mystery. @jinnantonnix will fill you in more there, I expect

 

So we have a fairly rare star type with a rare planet in that it happens to be at the correct distance to be at the right temperature and it has things like a moon, plate tectonics, a magnetic field etc.

 

Don't forget our galactic position - any closer to the galactic core and there'd be too many cosmic rays scorching the planet, any further out and there wouldn't be enough heavy elements from supernovae. Our chances of existing are really really really really really really really really really really ridiculously slim.

Edited April 14, 2015 by sonofsanta

[CAM]

Here's a question for you science people... On the film interstellar the dad goes to another planet and an hour on that planet is considered to be 7 years on Earth, therefore he only ages 1hour but all the people on Earth have aged 7 years. Now I know there's something about if you travel really fast time slows down. But is this all the case and if so how!?!?

 

This is the one subject that has always really confused me. Does that mean if I travel faster than the speed of light you'd go back in time? Does it mean I wouldn't age if I travelled consistently at the speed of light? I don't get it?

 

You'd perceive yourself to age normally whilst those observing perceive you to age faster. The rate of aging remains the same.

 

As for time travel, you could travel faster then the speed of light (if you have a means, it's the speed limit), arrive at your destination and observe yourself arriving as the light is slower than you are. In theory, you could proceed to mess with the timeline by doing something to prevent your ship arriving at the planet. PARADOX TIME!

Edited April 14, 2015 by CAM

[LosOjos]

You'd perceive yourself to age normally whilst those observing perceive you to age faster. The rate of aging remains the same.

 

As for time travel, you could travel faster then the speed of light (if you have a means, it's the speed limit), arrive at your destination and observe yourself arriving as the light is slower than you are. In theory, you could proceed to mess with the timeline by doing something to prevent your ship arriving at the planet. PARADOX TIME!

 

In that example though, only the light would arrive later, the physical entities involved (you and the ship) would actually already be there. Trying to do something like putting a wall in front of the spot you landed at before the light reaches it wouldn't achieve anything except making the light cast it's image on the wall - you'd already be there. So it's not time travel per sé, but the ability to see past events after the fact.

 

Theoretically, if we could send a ship instantly to a position 65 million light years away equipped with a camera capable of focusing in on Earth from that distance, we could take photographs of living dinosaurs (I read a really interesting article on this (and why it's absolutely impossible - such a lens would have more mass than our solar system) via reddit a while back, shame I can't find it right now...)

[jinnantonnixx]

Here is one of the best introductions to relativity, and why time's passage is observed differently depending on your frame of reference.

 

It also shows how the famous E=mc2 equation is derived.

 

http://youtu.be/GL04RizDT_M

[eyetea]

Pfft way ahead of you it's already found it

[ATTACH=CONFIG]30140[/ATTACH]

 

*Plays dramatic alien music*

 

Don't let 1 set of footprints confuse you... the sand people always ride single file to conceal their numbers

 

[BassTech]

Exciting times we live in, all of these new potentially habitable planets/moons being discovered in "Goldilocks zones" are really awe-inspiring. With the amount of galaxies out there (100 billion that we know of) each harboring dozens of planets, I think there just HAS to be some other form of intelligent life other than us humans. We may never know and we will probably destroy our planet long before we get to deep-space travel, but it's incredible to think about.

[CAM]

In that example though, only the light would arrive later, the physical entities involved (you and the ship) would actually already be there. Trying to do something like putting a wall in front of the spot you landed at before the light reaches it wouldn't achieve anything except making the light cast it's image on the wall - you'd already be there. So it's not time travel per sé, but the ability to see past events after the fact.

 

Theoretically, if we could send a ship instantly to a position 65 million light years away equipped with a camera capable of focusing in on Earth from that distance, we could take photographs of living dinosaurs (I read a really interesting article on this (and why it's absolutely impossible - such a lens would have more mass than our solar system) via reddit a while back, shame I can't find it right now...)

 

Causality is what I was looking for. Relativity and FTL Travel: Part IV

 

It's insanely complex but I think I get the idea. Ship A and B pass each other. Ship A does something which is seen by an observer. The observer sends an FTL speed message back along the path of Ship B telling them to stop the event. Ship B intercepts the message further back in time as the signal is FTL and arrives at their antenna before they pass Ship A. Ship B stops Ship A from doing whatever it did to cause the event, but because the event hasn't happened the observer couldn't have seen it to send a message back at FTL speeds.

 

This means the message wouldn't have been sent and Ship A wouldn't be stopped from causing the event in the first place subsequently causing it to happen anyway. But the observer has now seen the event and sends an FTL signal back alerting Ship B. The event occurring is the cause of the event not occurring which isn't possible without the event occurring which stops the event occurring but......PARADOX!

[jinnantonnixx]

 

Given that I see people proposing black hole star drives, I have to wonder about unimaginable degrees of sophistication! The fact is, even with modest propulsion technology the human race could colonise the whole galaxy in a million years or so. If the probabilities of life are such that people believe life must arise elsewhere simply because the universe is so vast, then it surely would have arisen long enough ago to have already populated a galaxy -a million years being less than the blink of an eye on cosmological time-scales. The sheer scale of that kind of activity would leave tell tale signs - signs we simply do not see. So the basic paradox for those that think life must be out there is that the more likely they think that is, the more difficult it is to explain why we don't see evidence of it.

 

Well, my imagination may be a little more restrained than others.

 

I can't see how you can conclude that a failure to see signs (whatever they might be) is an indication that there is no other life in universe. This has fallen into the proving-a-negative fallacy you mentioned earlier. Let's take the Earth as a specific example. Our weak radio transmissions have been our only beacon, and these haven't been going for long. A reciprocal observer at a distance of over 200 light years, looking for the same signs must therefore conclude that there is no life in our solar system, even though there has been life on Earth for millions of years.

 

We must also consider that much of the universe can never be observed (not to be confused with Olbers' Paradox). Furthermore, billions of years from now, the universe will have expanded so much that galaxies that are now visible will become invisible forever. They will have slipped beyond the light horizon, and their light will never, every reach us, no matter how long we wait. The only visible galaxies will be 'local' galaxies. To an observer in this period, the universe will appear to be static, even though in reality it is still expanding.

Edited April 14, 2015 by jinnantonnixx

[pcstru]

I can't see how you can conclude that a failure to see signs (whatever they might be) is an indication that there is no other life in universe. This has fallen into the proving-a-negative fallacy you mentioned earlier. Let's take the Earth as a specific example. Our weak radio transmissions have been our only beacon, and these haven't been going for long. A reciprocal observer at a distance of over 200 light years, looking for the same signs must therefore conclude that there is no life in our solar system, even though there has been life on Earth for millions of years.

 

My conclusion is simply that we have no evidence of other life in the universe, therefore we cannot conclude that there is other life. I think that is entirely rational and reasonable!

 

We must also consider that much of the universe can never be observed (not to be confused with Olbers' Paradox). Furthermore, billions of years from now, the universe will have expanded so much that galaxies that are now visible will become invisible forever. They will have slipped beyond the light horizon, and their light will never, every reach us, no matter how long we wait. The only visible galaxies will be 'local' galaxies. To an observer in this period, the universe will appear to be static, even though in reality it is still expanding.

 

Big numbers become bigger but the problem remains the same.

[pcstru]

Here's a question for you science people... On the film interstellar the dad goes to another planet and an hour on that planet is considered to be 7 years on Earth, therefore he only ages 1hour but all the people on Earth have aged 7 years. Now I know there's something about if you travel really fast time slows down. But is this all the case and if so how!?!?

Yes it does seem to be the case that time is experienced differently for different observers relative to each other. How? Because maths. Because Physics. We know experimentally that it is the case - in fact we have to compensate for time dilation effects in the clocks aboard GPS satellites, otherwise the system would start to accumulate large errors very quickly.

 

This is the one subject that has always really confused me. Does that mean if I travel faster than the speed of light you'd go back in time? Does it mean I wouldn't age if I travelled consistently at the speed of light? I don't get it?

 

I'll give it a go, not because I think I have a great understanding and can explain it, but in the attempt I might learn something!

 

If you travel at the "speed of light", you will not experience time. Other peoples view of their time relative to yours will differ. Think of it like travelling over the ground relative to someone else. They are moving toward you at 3mph, you are moving toward them at 5mph, you all locally see a closing speed of 8mph - yet you travel over more ground than they do (relative to the ground).

 

Can you travel back in time? No. Travelling back in time is like negative distance, it doesn't make much sense. In terms of distance it doesn't matter which direction you move in, you are going to move a certain distance (> 0). If you travel to work, you go 10 miles. When you go home, you go another 10 miles. You can't 'ungo' 10 miles. There is simply no journey that is -10 miles, no journey is possible less than none. You can sit on your bum doing no miles at all, and you can move in different directions, but you can't move negative distance. Going faster won't turn distance negative just as it won't turn back the clock.

 

When we move, we move not just through space but through spacetime. Just like a ball rolled on a perfect billiard table, we move through space-time in a straight line. Unlike a billiard table, spacetime isn't flat. It is stretched and curved so a straight line path over that surface appears curved. What seems to cause the distortion the presence of things themselves. The very existence of anything distorts spacetime. And like our relative travel, if you are in orbit around a huge something, a massive object like a black hole or even just a planet, your experience of time will appear to be different relative to a friend not close to such a huge mass. For both of you, although the experience of a second will still be a second, less time will pass for you relative to the friend.

 

It turns out those things (that distort spacetime) are essentially dividied into two domains. Light (energy) and Mass (stuff). You can trade between them at a ratio of C^2 E for every 1 of mass stuff. C is commonly taken as the "speed of light" which as a number would make a delightful pay cheque, so square it and you get a lot of energy for only a small amount of mass. All stuff in the universe obeys this formula E=mc^2 and everything has energy, mass (or a ratio of both) and everything has C; that is everything is travelling through spacetime at C - the speed of light. C isn't a limit for spacetime, it is the law. You can't go faster than C, but also you can't go slower, you travel through spacetime at C, the speed of light.

 

Now before the chorus of objections pipes up, you are obvioulsy not whooshing through space at the speed of light, so some of your velocity is moving you in a different direction than the normal 3-space x,y and z axis - it's moving you through time. A photon, which travels in space at the speed of light, uses all it's C doing just that and it doesn't travel in the time direction at all - that is it locally experiences no time. A photon might have left a star billions of years (from your perspective) before it lands on the retina at the back of your eye and is absorbed by an atom, but for the photon, no time has passed at all. It was absorbed by your eye at the very instant it was emitted by the star - as far as it is concerned. This time dilation happens to anything that is travelling but it becomes particular pronounced as your speed through 3 space approaches the speed of light. In terms of spacetime, you aren't actually speeding up to C (since you are already travelling at C), you are simply changing direction such that your direction of travel is more into 3-space and less into the time axis.

 

So basically, time dilation relative to someone else is because we travel through spacetime but the spacetime we travel through locally is a different shape to theirs which causes us to take a different path, a path that may involve more or less travel on the time axis compared to the x,y and z axis (it should be said that normal space is distorted too, both in the presence of a mass and when travelling at close to the speed of light - you become stretched/compressed in space as well as time) .

 

And since the view that we are all travelling at C usually does raise objections, I'll leave it there for now!

[woodham]

couldn't we just as the mice to fund another earth?

 

 

ah well so-long and thanks for all the fish