# Planet closest to us

1. Feb 23, 2012

### jbobay2339

OK I'm fairly new to these topics but eager to learn but as I'm sure most of you know the closest know habitable planet is gliese 581g. They say at 11 miles a sec it will take 79 years but I'm wondering does that take into account the universes expansion and would it be 79 earth years and if so wouldn't time be going slower for someone traveling at that speed. I realizes its not a very technical question but its just a curious thought I had. Thanks

Last edited by a moderator: Feb 23, 2012
2. Feb 23, 2012

### Ryan_m_b

Staff Emeritus
Welcome to the forum. Currently we do not know of any other habitable planet other than Earth; whilst it is located within the habitable zone where water could form we do not even know if it is a solid planet (it is also several times the mass of Earth). On top of that for something to be habitable we require a biosphere, specifically one we have evolved to cope with.

The distance to gliese 581g is ~20 light years which is 5.87 trillion miles! At a mere 11 miles per second it would take roughly 17,000 years.

The expansion of the universe is minute and at this distance would not make a difference.

3. Feb 23, 2012

### jbobay2339

Haha thanks that answered that as you can tell I've just started some reading and learning but I love this stuff

Last edited by a moderator: Feb 23, 2012
4. Feb 23, 2012

### Ryan_m_b

Staff Emeritus
No problem

5. Feb 23, 2012

### Chronos

The 5.87 trillion miles ryan mentioned is for one light year, so the journey to gliese 581g at 11m/s will take about 340,000 years. The planet is about 3-4 earth masses and its diameter is estimated at 1.2 - 1.4 times that of earth. That gives it a mean density somewhat greater than earth, so it definitely looks like a rocky planet. Here is the paper purporting its existence http://arxiv.org/abs/1009.5733. Its existence has, however, been in dispute. See http://blogs.discovermagazine.com/badastronomy/2011/01/18/does-gliese-581g-exist/ for the juicy details [scientists version of a cat fight].

6. Feb 23, 2012

### Ryan_m_b

Staff Emeritus
Cheers for the catch, I forgot to put the two things I'd said together.

7. Feb 23, 2012

Not enough to make a noticeable difference. Even at velocities slightly greater than that it still

wouldn't amount to much. For example, at the 17 miles per second velocity toward Gliese,

time dilation would still not be noticeable. For every second we age on Earth, the crew would

age approx 12 nanoseconds or twelve billionths of a second less. On the Mir space station

with an approx orbital velocity of 4.7845581802275 miles per second, a crewmember

ages approx 3 nanoseconds, or three billionths of a second less for every second we age

on Earth,

BTW
Earth orbital velocity around our sun averages approx 18.5044 mi. per second,
or 29.783 kilometers per second.

Last edited: Feb 23, 2012
8. Feb 24, 2012

### Chalnoth

This is why interstellar travel is only remotely reasonable if we can find a means to keep the ship accelerating continuously throughout the entire journey. That or commit ourselves to some extraordinarily long-term journeys.

9. Feb 24, 2012

### Staff: Mentor

Don't treat nanoseconds so lightly, you are wrong by just 60 ns and you stir up a havoc in the scientific community.

10. Feb 24, 2012

### Chalnoth

Why would you post this?

11. Feb 24, 2012

### Ryan_m_b

Staff Emeritus
Lol!
Perhaps because it was funny :rofl:

12. Feb 24, 2012

Just a joke. : )

Last edited: Feb 24, 2012
13. Feb 24, 2012

### cepheid

Staff Emeritus

Your post confuses me greatly, so I just have to ask: are you entirely unfamiliar with the concept of humour, and do you really not know what the 60 ns was in reference to? OR were you yourself just trying to make a joke as well? If the latter, I gotta say, you need to work on your material. :tongue:

14. Feb 24, 2012

Perhaps you are right and I misunderstood the post.
My sincere apologies.

15. Feb 24, 2012

You are 100% right! Even a nansecond is very important in science.

16. Feb 24, 2012

### CaptFirePanda

It was a reference to the 60 ηs "anomaly" detected in the travel time for a neutrino and the subsequent hoopla.

17. Feb 24, 2012

Thanks for the info.

Last edited: Feb 24, 2012
18. Feb 24, 2012

### cepheid

Staff Emeritus
Also just for clarity, I was the one giving you a hard time, not Borek, who told the joke.

Sorry for giving you a hard time.