NASA announce new planets

RocknRollDave

57Deluxe said:

RocknRollDave said:

Correct me if I am wrong, but finding planets isn't all that rare? Now, if they found new one in our solar system, THAT would be newsworthy

they have! - apparently a revision of the guidlines now suggests that the Moon should be reclassified as a Planet!

http://www.thetimes.co.uk/article/moon-rises-to-claim-its-place-as-a-planet-3m3wh5dz3

But......you can't have a planet made out of cheese, Gromit....!

Fretwired

RocknRollDave said:

Correct me if I am wrong, but finding planets isn't all that rare? Now, if they found new one in our solar system, THAT would be newsworthy

I thought they'd found a 9th planet beyond Pluto ..

http://www.sciencemag.org/news/2016/01/feature-astronomers-say-neptune-sized-planet-lurks-unseen-solar-system

Cirrus

RocknRollDave said:

Correct me if I am wrong, but finding planets isn't all that rare? Now, if they found new one in our solar system, THAT would be newsworthy

Now, let's not be too down on this. We're finding out conclusively that planets are absolutely everywhere, and this has huge long term implications for the potential of life outside our world... which in turn has big implications for our place in this game we call reality, if we can get over our tendancy to think short term, kill each other and ourselves, and avoid destroying the planet until we get to the point where we can do something practical with our discoveries.

I suppose the reason this one is note worthy is that it's an entire system - it's not just "kepler has found 500 planets while scanning 50,000 stars for a year" or whatever, it's the idea that this is an entire system of planets around a star with a number of planets orbiting in the zone where there would be sufficient energy for the complex chemical reactions that could lead to life. That's cool.

Kalimna

Now (if someone with a better grasp of relativistic physics could help me out a bit here) am I correct in thinking that although this system is 40 light years away, it would take less than 40years at near light-speed from the perspective of the travellers?
Accelerating to near light speed would not be impossible given something like a big enough solar sail. The significant problems would be collision avoidance, radiation protection and energy provision for the travellers.
Is it likely? Well, that depends on the timescale.

Adam

Cirrus

I am not a physicist, but this being the internet I will PRETEND I am.

The speed of the solar wind, according to google, is around 400km/s. Which is fast, but light speed is 300,000km/s. So a solar sail probably wouldn't cut it.

Yes, due to relativity, if you could get to nearly the speed of light time would move more slowly for you with reference to the rest of the universe. So you could get there after a few millennia and feel like only a few decades had passed, if you went fast enough.

However, my understanding is that as you approach the speed of light, your extra kinetic energy effectively becomes extra weight so each extra meter per second gets progressively harder to get to.

Nitefly

Cirrus said:

I am not a physicist, but this being the internet I will PRETEND I am.

The speed of the solar wind, according to google, is around 400km/s. Which is fast, but light speed is 300,000km/s. So a solar sail probably wouldn't cut it.

Yes, due to relativity, if you could get to nearly the speed of light time would move more slowly for you with reference to the rest of the universe. So you could get there after a few millennia and feel like only a few decades had passed, if you went fast enough.

However, my understanding is that as you approach the speed of light, your extra kinetic energy effectively becomes extra weight so each extra meter per second gets progressively harder to get to.



Also, you'll have to slow down and stop when you get there... 

Kalimna

Regarding the solar wind - it acts as a constant accelerating force. So a constant push from one 'side' of the sail with effectively no opposing resistance. Thats why its possible to get high velocities with a sail.

Adam

Cirrus

So, how do you end up going faster than it?

MrBump

Cirrus said:

So, how do you end up going faster than it?

You have to engage the flux capacitor.

Ravenous

Kalimna said:

Regarding the solar wind - it acts as a constant accelerating force. So a constant push from one 'side' of the sail with effectively no opposing resistance. Thats why its possible to get high velocities with a sail.

Adam

I don't think that works with solar "wind". It works with boats because you're in a dense liquid and can use the water's reaction against your hull, keel and rudder to maintain direction.

But - correct me if I'm wrong - I don't think a solar sail wouldn't allow tacking and other tricks of seamen.

(Huh - he said "Seamen".)

Kalimna

There's a nice Wikipedia article on solar sails.
They use photon momentum to impart a thrust to an object, and whilst a useful analogy is that of a sailing boat in wind it doesn't tell the whole story.

In a nutshell, I think, imagine each photon that hits the sail exerts an amount of thrust. As far as the sail is concerned, each photon will be hitting it at the same speed relative to the sail no matter what speed the sail is moving (see Einstein and relativity). Therefore the thrust gained from the solar wind (photon 'pressure') is independent of the speed of the object being moved - it doesn't act like a medium (like wind on a boats' sail) but more like a force (e.g gravity).

Adam

Nitefly

Makes sense, but I'd still like to know how you slow it down when you arrive?  Is that a matter of the photons from the "target" star working in the opposite direction?

robgilmo

http://nathangeffen.webfactional.com/spacetravel/spacetravel.php

Have a play with this.

TheMarlin

Kalimna said:

There's a nice Wikipedia article on solar sails.
They use photon momentum to impart a thrust to an object, and whilst a useful analogy is that of a sailing boat in wind it doesn't tell the whole story.

In a nutshell, I think, imagine each photon that hits the sail exerts an amount of thrust. As far as the sail is concerned, each photon will be hitting it at the same speed relative to the sail no matter what speed the sail is moving (see Einstein and relativity). Therefore the thrust gained from the solar wind (photon 'pressure') is independent of the speed of the object being moved - it doesn't act like a medium (like wind on a boats' sail) but more like a force (e.g gravity).

Adam

Nope.  That was an old theory, based on Crookes Radiometer.  In a partial vacume, it appears that photons impart momentum, but it's energy from heat moving dispersed air molecules.
In a hard vacume, Crookes Radiometer does not work.   The force of photons pushing against vanes cannot be detected.  
The idea that photons can push and reflect off a solar sail is a violation of conservation of energy because the photons are also imparting energy on the sail since they are doing work. The photons and the sail can't both gain energy. If you consider the doppler effect, the frequency of the reflected light will be shifted down. That is, the photons will have less energy. This difference equals the amount of energy transferred to the sail.  Therefore, the sail will not move.  

Nice idea though....

Kalimna

Cheers for the explanation. I feel like a QI style klaxon is going off in my distance

Adam

Danny1969

Travelling anywhere near light speed is not possible ... As you travel faster you gain mass and require more and more power ..... Basically nothing with any starting mass can travel at the speed of light as far as we know at this time .

Even if you could travel at the speed of light you wouldn't be able to navigate anywhere as your essentially travelling as fast as any navigational device can set your course ... As soon an obstacle was detected you would hit it Space isn't empty it has loads  of micro meteorites and other hazards 

Generation ships are the only way forward .... You set sail as a young man and its your great grand kids that get to colonise somewhere . Even then you would have to travel at 1/50th of the speed of light for 200 years to reach alpha Centauri, the nearest star system to us ...  

Its sad  but I doubt we will ever get beyond the solar system before we've used all the available resources and fuel on this planet. 

NelsonP

There, that pi$$ed on your bonfire, didn't it ;-)