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Seven earth-sized planets discovered circling a star 39 light years from Earth

nature.com

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Re: Seven earth-sized planets discovered circling a star 39 light years from Earth

#191

Post by sfeng »

wallace_f wrote: post #170
delecti wrote: post #157

Earlier quoted context omitted.

Just going that fast isn't really risky at all (assuming you don't hit anything, which isn't actually a safe assumption). The tough part is making something capable of a constant 1g of acceleration for a 7 year trip. Most of the craft we make only accelerate for the first small percent of a trip. We can do accelerations that high, but not for very long, and we can't even manage acceleration for such a long duration e…

My layman's reading of physics-for-layman books has taught me that if we were to travel at the speed of light, we'd convert into energy. However, I'm not so sure about 99.999999% the speed of light. That's really OK, as far as we know?

Yes, as long as you don't hit anything or care about the time dilation you will experience.

Re: Seven earth-sized planets discovered circling a star 39 light years from Earth

#192

Post by sand500 »

delecti wrote: post #157
wallace_f wrote: post #128

Earlier quoted context omitted.

Is it plausible for anything we'd build to travel .998c and survive the journey?

Just going that fast isn't really risky at all (assuming you don't hit anything, which isn't actually a safe assumption). The tough part is making something capable of a constant 1g of acceleration for a 7 year trip. Most of the craft we make only accelerate for the first small percent of a trip. We can do accelerations that high, but not for very long, and we can't even manage acceleration for such a long duration e…

If you go fast enough doesn't any incoming radiation just get blue shifted into gamma rays? Just running into cosmic dust at the speed of light would not be fun.

Re: Seven earth-sized planets discovered circling a star 39 light years from Earth

#193

Post by [deleted] »

delecti wrote: post #157
wallace_f wrote: post #128

Earlier quoted context omitted.

Is it plausible for anything we'd build to travel .998c and survive the journey?

Just going that fast isn't really risky at all (assuming you don't hit anything, which isn't actually a safe assumption). The tough part is making something capable of a constant 1g of acceleration for a 7 year trip. Most of the craft we make only accelerate for the first small percent of a trip. We can do accelerations that high, but not for very long, and we can't even manage acceleration for such a long duration e…

[deleted]

Re: Seven earth-sized planets discovered circling a star 39 light years from Earth

#194

Post by flexie »

_lbaq wrote: post #131
noobermin wrote: post #121

Earlier quoted context omitted.

One of the callers (a biologist, so not a crackpot) on TV suggested that given how close the planets were, he wondered if it were possible for there to be cross contamination between the planets given how close they are to each other. He referred to them being part of the same "ecosystem." I'm not sure how feasible that is as a non-astrobiologist, but it is an interesting idea.

Very likely, since this happens between Mars and Earth: https://en.wikipedia.org/wiki/Martian_meteorite

Fascinating! Would vira or bacteria beable to survive travelling from Earth to Mars in or on a rock or vice versa?

Re: Seven earth-sized planets discovered circling a star 39 light years from Earth

#195

Post by snerbles »

dexwiz wrote: post #62
jdormit wrote: post #39

Earlier quoted context omitted.

We don't have any spacecraft that can go that fast, do we?

No, but we probably could with enough fuel. The bigger issue is space dust. Hitting it at relativistic speeds would be like flying into a cosmic shotgun for the entire journey.

A large mass of water ice would make a decent ablative shield.

Re: Seven earth-sized planets discovered circling a star 39 light years from Earth

#196

Post by visakanv »

strictnein wrote: post #180
imdsm wrote: post #148

Earlier quoted context omitted.

If they are tidally locked as reported, then there will be no day, not really. Just as there is no day on the moon.

The moon rotates once every ~27 days, so its day is ~27 days. It's just in sync with its orbit of the earth, so it appears to us that it doesn't rotate. http://www.space.com/24871-does-the-moon-rotate.html

Isn't that technically the moon's "year"?

Re: Seven earth-sized planets discovered circling a star 39 light years from Earth

#197

Post by idbehold »

root_axis wrote: post #101
h4nkoslo wrote: post #41

Uh oh. The "great filter" hypothesis is essentially that the rarity of intelligent life has to be explained by some parameter of the Drake equation, and that whatever the "small" parameter is is either in our past or in our future. If the "great filter" is the rarity of habitable worlds, then clearly we don't need to fear it, since we already found one. But if habitable worlds aren't rare, then it's more likely it li…

The theory as described in your link seems to hand-wave away the difficulties incumbent in the "colonization explosion" step. As it stands, intergalactic space travel (at scale) is utterly inconceivable in practical terms, and to simply assume that it is inevitable seems like a major flaw in the theory.

> then it's more likely it lies in our future (e.g. global thermonuclear war, plague, difficulty of space travel, etc)

Difficulty of space travel is one of the possible filters.

Re: Seven earth-sized planets discovered circling a star 39 light years from Earth

#198

Post by dmreedy »

dagurp wrote: post #153
dmreedy wrote: post #70

Earlier quoted context omitted.

I guess J.J. Abrams is somewhat forgiven for this, then: http://vignette4.wikia.nocookie.net/startrek/images/2/29/Vul... [edited for direct .jpg]

Firefox tries to download this file

Apologies, sloppy link-copying. Should be pointing to the .jpg now.

Re: Seven earth-sized planets discovered circling a star 39 light years from Earth

#199

Post by [deleted] »

josho wrote: post #98
jdormit wrote: post #39

Earlier quoted context omitted.

We don't have any spacecraft that can go that fast, do we?

If I understand our capabilities correctly we can't even escape the solar system without using gravity assist boosts from other planets, let alone sustaining thrust for a long period. http://solarsystem.nasa.gov/basics/chapter4-1

[deleted]

Re: Seven earth-sized planets discovered circling a star 39 light years from Earth

#200

Post by semaphoreP »

coryfklein wrote: post #149

I'm having a hard time finding more data on the density of matter in interstellar space. Wikipedia says > The density of matter in the interstellar medium can vary considerably: the average is around 10^6 particles per m3 but cold molecular clouds can hold 10^8–10^12 per m3 [1] But I imagine that interstellar gas would be easier to fly through than interstellar sand. Do we know the composition of matter in interstell…

It's almost all Hydrogen/Helium gas. Other larger atoms and molecules are known to exist in the interstellar medium, but it's primary gas.

Also, a good way to remember the density is ~1 Hydrogen atom per cm^3.

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